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3.4 Mitral Valve Repair
3.4
Mitral Valve Repair Margo Winters, RN; Pam Obriot, RN indicates that continuing education contact hours are available for this activity. Earn the continuing education contact hours by reading this article and taking the examination on pages 167-168 and then completing the answer sheet and learner evaluation on pages 169-170 You also may access this article online at http://www.aorn journal.org.
T
he first treatment for mitral valve disease came shortly after the invention of the heart-lung bypass machine.1 Direct visualization of the mitral valve made replacement surgery possible. The negative aspects of mitral valve replacement, however, include possible thromboembolism, hemolysis, and infection. This led cardiothoracic surgeons to search for other methods to treat mitral valve disease. As physicians began to understand the complex function and geometry of the mitral valve and the subvalvular apparatus, repair techniques evolved, and mitral valve repair soon became the gold standard in mitral valve treatment.1 The number of mitral valve repair cases has increased during the last decade as new knowledge and increased experience has offered new treatments for valvular repair.2 This article describes typical mitral valve repair procedures
ABSTRACT •
DISEASES THAT AFFECT the mitral valve include mitral regurgitation, mitral stenosis, rheumatic heart disease, and cardiomyopathy.
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THE RESULTS OF DIAGNOSTIC procedures are used to identify and confirm mitral valve disease, evaluate the patient’s anatomy, and determine the severity of the disease.
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AFTER THE PATIENT IS PREPARED for surgery, the surgeon performs an intraoperative transesophageal echocardiogram and the patient is placed on cardiopulmonary bypass.
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A REPAIR PROCEDURE (eg, annuloplasty, slidingplasty, chordal repair/transfer/replacement, valve replacement) is performed depending on the patient’s specific anatomical abnormalities. AORN J 85 (January 2007) 152-166. © AORN, Inc, 2007.
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performed on a daily basis at the University of Michigan Health System, Ann Arbor, Mich. Table 1 provides definitions of common medical terms associated with mitral valve repair.
MITRAL VALVE DISEASE PROCESSES Two types of disease processes (ie, geometric and valvular) affect the mitral valve. The type of disease process determines the appropriate type of repair. GEOMETRIC DISEASE. Geometric disease, also referred to as ventricular disease, is mitral regurgitation originating within the left ventricle. In geometric mitral disease, the left ventricle has dilated so much that the mitral annulus has stretched and the mitral valve leaflets can no longer coapt (ie, come together). Geometric disease can be ischemic or nonischemic in origin. The most common form of ischemic heart failure is myocardial infarction. In the presence of coronary artery disease, narrowing or obstruction of an artery causes decreased myocardial perfusion.3 Occlusion of the artery can be caused by platelet aggregation, thrombotic embolism, dislodged calcium plaque, or coronary artery spasm. This ischemia leads to necrosis of the myocardial tissue. Persistent necrosis interferes with myocardial function and eventually can produce large areas of akinetic tissue (ie, tissue that has lost the ability to move).3 There are many causes of nonischemic heart disease, but the heart’s decreased ability to pump effectively ultimately results in cardiomyopathy. Some causes of nonischemic heart disease are hypertension and infections such as endocarditis.3 The most common cause of geometric disease is dilated cardiomyopathy. In geometric mitral disease, the valve and © AORN, Inc, 2007
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TABLE 1
Common Medical Terms Associated with Mitral Valve Repair Annulus
Mitral regurgitation
A ring-like structure; a fibrous band of tissue which serves as the attachment point for the leaflets
A backward flowing of blood into the left atrium of the heart caused by an incompetent mitral valve
Annuloplasty
Mitral stenosis
Surgical repair of a deformed annulus surrounding a diseased mitral valve
Obstruction to the flow of blood through the mitral valve, usually caused by narrowing of the valve orifice
Bicuspid valve
Subvalvular apparatus
A valve consisting of two leaflets (eg, the mitral valve)
Coaptation
Chordae tendineae and papillary muscles within the left ventricle that contribute to the geometry and function of the mitral valve
The proper joining or fitting together of two surfaces (eg, mitral valve leaflets)
Trigone
Geometric mitral disease
Valvular mitral disease
A dysfunction of the mitral valve related to dilation of the left ventricle
Three angled section on the ends of the fibrous region between the aortic and mitral valves Valve dysfunction related to issues of the valve or subvalvular apparatus
Left ventricular outflow tract
Zone of coaptation
A pathway from which blood exits the left ventricle and passes through the aortic valve
Rough surface of mitral valve leaflets that join together during left ventricular systole
subvalvular apparatus are all normal. The problem is within the ventricle, which has become dilated to the extent that the normal function of the valve is disrupted. VALVULAR DISEASE. Valvular mitral disease is a process in which the leaflets and/or the annulus have become calcified and stiff or fused. In addition to calcification, valvular disease also may include chordal shortening, which may lead to mitral stenosis or regurgitation. In the United States, valvular disease most commonly is caused by rheumatic endocarditis.4 Whatever the etiology, most patients will have some degree of dilation in the mitral annulus that must be repaired.5
MITRAL VALVE ANATOMY
AND
PHYSIOLOGY
The bicuspid (ie, two leaflet) mitral valve is located between the left ventricle and left atrium. The valvular complex consists of the annulus, leaflets, chordae tendineae, and papillary muscles (Figure 1), and in a sense, the left ventricle is the mitral valve. The annu-
lus, a fibrous band of tissue from which the leaflets originate, is considered the “hinge line” of the valve leaflets.6 Continuing out from the annulus, the two leaflets (ie, anterior and posterior) are pale yellow, thin, fibroelastic membranes whose anterior surfaces are relatively smooth. The posterior or ventricular surfaces are slightly irregular because of the attachments to the chordae tendineae. The anterior leaflet is also known as the anteromedial, septal, or aortic leaflet.4 The posterior leaflet, also known as the mural leaflet, is further divided into three cusps commonly known as P1, P2, and P3. The three posterior cusps do not have separate functions; they have been named purely for ease of describing mitral valve anatomy and locations of regurgitation jets (ie, flashes of backward blood flow). The chordae tendineae are attached to the inferior surface of the leaflets. These white, cord-like tendons act only as guides to assist in the coaptation of the two leaflets. The chordae tendineae AORN JOURNAL •
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Figure 1 • Interior view of the heart showing the mitral valve and subvalvar apparatus.
left atrium posterior leaflet anterior leaflet chordae tendinae papillary muscle left ventricle
preventing the backwards flow (ie, regurgitation) of blood into the left atrium. The chordae tendineae guide the leaflets into position; the chordae do not pull the leaflets together. This forms a tight closure (Figure 2), preventing mitral regurgitation and allowing the forward flow of blood through the left ventricular outflow tract, through the aortic valve, and out into the aorta. The function of the mitral valve is regulated by interaction of the components of the mitral apparatus (ie, leaflets, chordae tendineae, papillary muscles, ventricular wall). The mitral apparatus contributes to the normal geometry and function of the left ventricle.
CAUSES
Figure 2 • Normal mitral valve in closed position.
also prevent the leaflets from billowing or everting up into the atrium. If a primary chordae ruptures, the leaflet everts into the atrium and is called a “flail” leaflet. The chordae are attached to the papillary muscles at the base of the left ventricle. Oxygenated blood originating from the lungs flows through the pulmonary veins and collects in the left atrium. When pressure in the left atrium is greater than the pressure in the left ventricle, the mitral valve opens allowing blood to flow into the left ventricle. As the intraventricular pressure rises, the mitral valve closes (ie, the leaflets coapt)
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OF
MITRAL ABNORMALITIES
Numerous diseases affect the ability of the mitral valve to function properly. Some of these diseases include mitral regurgitation, mitral stenosis, rheumatic heart disease, and cardiomyopathy. MITRAL REGURGITATION. Mitral regurgitation also is referred to as incompetence or insufficiency. Regurgitation is a result of the leaflets not coming together completely. An incompetent mitral valve allows backflow of blood into the left atrium. This backward flow in turn leads to increased atrial volume and eventually leads to backward flow of blood into the lungs. This backflow into the lungs leads to pulmonary edema. As a result of this blood flow back-up, many patients with mitral regurgitation present to their primary care physician with signs and symptoms of right heart failure.2 The heart works harder to try to compensate for the lost forward blood flow; the ventricles may begin to hypertrophy (ie, thicken) because of the added workload. If there is an ischemic area in the left ventricle from a myocardial infarction, the tissue can weaken and become stretched, forming an aneurysm, and become dysfunctional.
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MITRAL STENOSIS. Mitral stenosis refers to the calcification of the leaflet and annulus. A stenotic mitral valve also leads to heart failure in much the same way as mitral regurgitation, but instead of blood moving backwards through the mitral valve, mitral stenosis does not allow enough blood through the narrowed, fused, or calcified opening of the mitral valve leaflets. The process continues much the same as is seen in mitral regurgitation, resulting in right heart failure as blood volume builds up in the lungs. Stenotic valve repair is more complicated than repair of a dilated mitral annulus and requires more experience on the part of the surgeon.5 The surgeon must make decisions about excising calcified valvular tissue and possibly replacing chordae or advancing leaflets. Each patient’s valve is different regarding the degree of stenosis and involvement of the chordae tendineae and papillary muscles. RHEUMATIC HEART DISEASE. Rheumatic heart disease has decreased in the United States in recent decades as a result of effective antibiotic treatment of streptococcal (ie, strep) infections.4 Untreated strep infections lead to rheumatic fever in which antibodies produced by the body to fight the infection also attack heart valve leaflet tissue, most commonly the mitral valve. In developing countries, children often do not receive therapeutic antibiotic treatments, so they constantly are reinfected with strep. These countries still have large populations with rheumatic heart disease, which is the leading cause of cardiovascular death in young adults.7 Infective endocarditis is a form of rheumatic heart disease seen more often in the United States. This disease can be caused by contamination of the blood as a result of illicit IV drug use,7 dental procedures, or surgical infections. The bacteria attach themselves to the mitral valve leaflets causing
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scarring; erosion; and ultimately, varying degrees of stenosis. CARDIOMYOPATHY. Although cardiomyopathy can be caused by neuromuscular or connective tissue disorders, alcohol abuse, viral infections, or exposure to cardiotoxic substances, most cases are of unknown origin (ie, idiopathic).4 The most common medical condition of patients older than age 65 is congestive heart failure (CHF).3 Chronic CHF can lead to dilated cardiomyopathy, which causes the mitral annulus to stretch, resultUntreated ing in mitral regurgitation. The geometric mitral streptococcal valve repair procedure to resolve this problem is the infections may simplest procedure to perform. This geometric discause rheumatic ease can be reversed with the placement of an annuloplasty device. Mitral fever in which the valve repair does not cure body’s antibodies CHF but can relieve the acute symptoms of mitral regurgitation and, ideally, fight the infection keep the patient off the but also attack heart transplant list longer.
DIAGNOSTICS
heart valve leaflet tissue, most commonly the mitral valve.
A variety of diagnostic procedures are performed to identify and then confirm mitral valve disease. After mitral valve disease is confirmed, diagnostic procedures can help evaluate the patient’s anatomy and determine the severity of the disease. PHYSICAL EXAMINATION. During any routine physical examination, general practitioners can detect a heart murmur— one sign of mitral regurgitation—by auscultation. If a health care provider is seeing a patient regularly, early detection of a heart murmur can result in early diagnosis and, more importantly, early treatment.
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CARDIAC CATHETERIZATION. In mitral valve disease, cardiac catheterization is used to confirm the diagnosis, assess ventricular function, discover other cardiac lesions, and evaluate coronary anatomy. Mitral regurgitation is confirmed by left ventriculography during cardiac catheterization. With the patient under light sedation, a cardiinserts a catheter A transesophageal ologist through the femoral artery injects an x-ray conechocardiogram and trast agent into the chamber. Fluoroscopy is used is a useful to document the dye flow as it regurgitates into the intraoperative left atrium. TRANSTHORACIC ECHOCARDIOtool to more GRAM. With acute mitral regurgitation, a surface accurately echocardiogram can detect determine valve abnormalities attributed to a ruptured chordae papilanatomy, annular lary muscle or perforated valve leaflet. The goal of transthoracic echocardiosize, and the gram is to identify the degree of mitral degree of regurgitation and valvular abnormality.5 Furthermore, addivalve disease tional information on left and assess for a atrial enlargement, right ventricular enlargement, regurgitant jet. and left ventricular dimensions can be obtained from an echocardiogram. TRANSESOPHAGEAL ECHOCARDIOGRAM (TEE). A preoperative TEE allows anatomy to be defined, assesses the degree of mitral regurgitation, and measures left ventricular function. The direction of the mitral regurgitation jet seen on a TEE can identify which leaflet is flailing or prolapsing. An anteriorly directed jet indicates a posterior leaflet prolapse or flail; whereas a posteriorly directed jet indicates an anterior leaflet prolapse or flail.1 A centrally directed jet may indicate annular dilation.
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Intraoperatively, the TEE is a useful tool to more accurately • determine valve anatomy, • assess the degree of the mitral valve disease, • assess the degree of regurgitation, • evaluate left ventricular function, • assess annular size and degree of enlargement, and • assess for a regurgitant jet. With the patient under anesthesia, a TEE probe is placed in the patient’s esophagus so that the probe lies behind the heart. The probe will remain in place throughout surgery. After the surgical repair has been performed, the surgeon will clamp the cardiopulmonary bypass (CPB) cannulas, fill the heart, and check the repair using a TEE. Based on this examination, the surgeon will decide if the repair is adequate. If the surgeon decides that additional repairs are needed, CPB will be reinitiated.
PREOPERATIVE PHASE
OF
SURGERY
In the preoperative holding room, the circulating nurse assesses the patient and verifies the patient’s identity. Before any narcotics are administered, the nurse confirms the proposed procedure with the patient and his or her family members, cross checking the procedure with the surgical consent and OR schedule, and resolving any discrepancies with the surgeon before the patient is taken to the OR. The nurse performs an examination to assess the patient’s physical health status, emphasizing identification of cardiovascular risk factors, such as height, weight, presence of hypertension or diabetes, and use of alcohol or illicit drugs. He or she further identifies the patient’s relevant medical history (eg, chronic illnesses, injuries, surgeries), and obtains the patient’s medication history, including medication allergies, and any use of • aspirin or other anticoagulants and
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the date of discontinuation of those medications, • prescribed medications, • over-the-counter medications, and • herbal therapies. The circulating nurse notes the results of pertinent laboratory studies, such as chest x-rays and complete blood count (CBC). He or she ensures that the patient has undergone blood typing and cross-matching and that two units of packed red blood cells are available. After completing the history and physical examination and reviewing the medical record, the nurse develops a nursing care plan specific to this patient and the proposed surgical procedure (Table 2).
INTRAOPERATIVE PHASE The circulating nurse and anesthesia care provider transport the patient to the OR. To maintain the patient’s temperature during the preparatory phase of the procedure, the circulating nurse places a temperature-regulating blanket on the patient after helping make the patient comfortable on the OR bed and securing the safety strap and arm boards. The anesthesia care provider places a radial arterial line in the patient’s nondominant wrist and a central line with a pulmonary artery thermodilution catheter in the patient’s right internal jugular. OR SETUP. While the anesthesia care provider places the monitoring lines, the circulating nurse and scrub person prepare the sterile field. Standard cardiac trays are used along with a valve tray, mitral valve retractor, and the appropriate valve sizers. The scrub person prepares the aortic cannula, bicaval cannulae, left ventricular catheter for ventricular decompression, and antegrade cardioplegia needle. The circulating nurse and scrub person perform the sponge, needle, and instrument counts. The circulating nurse confirms
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that all sizes of required implants (eg, mitral annular bands and rings) as well as necessary suture for valve repair are available. PREPARING THE PATIENT. After the anesthesia care provider has secured the monitoring lines, all perioperative team members including the surgeon and anesthesia care provider actively participate in the surgical time out. The anesthesia care provider then induces the patient under general anesthesia, The direction of after which the circulating nurse inserts an inthe regurgitant dwelling urinary catheter with a temperaturejet helps sensing probe. The circulating nurse ensures that determine the the patient is in an anatomically correct, sumechanism of pine position and pads and tucks the patient’s regurgitation elbows at the patient’s sides. The circulating because the jet nurse then places the electrosurgical unit (ESU) flows in the dispersive pad on the patient’s buttock. opposite direction The direction of the regurgitant jet helps deterof the flailing or mine the mechanism of regurgitation because the prolapsing leaflet. jet flows in the opposite direction of the flailing or prolapsing leaflet.1 The anesthesia care provider ensures that preload, afterload, and blood pressure are controlled during the TEE examination so that the degree of mitral regurgitation is not distorted. The anesthesia care provider inserts the TEE probe, and performs a preoperative assessment of valve function. Ideally, the anesthesia care provider and the cardiologist should perform the TEE together because TEE interpretation may vary between observers.1 When the TEE is complete, the circulating nurse preps the patient’s surgical AORN JOURNAL •
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TABLE 2
Nursing Care Plan for Patients Undergoing Mitral Valve Repair Diagnosis Risk for alteration in tissue perfusion related to cardiopulmonary bypass
• • • • •
Risk for anxiety related to knowledge deficit and stress of surgery
• • • • •
Risk for acute or chronic pain related to surgical procedure
• • • • •
Risk for fluid volume imbalance
• • •
Risk for inadvertent hypothermia
Interim outcome criteria
Outcome statement
Assesses for preexisting conditions that predispose the patient to inadequate tissue perfusion. Identifies baseline tissue perfusion. Collaborates in fluid management. Monitors physiological parameters (eg, peripheral pulses, urinary output, blood pressure, filling pressures). Evaluates postoperative tissue perfusion.
The patient maintains adequate tissue perfusion throughout the procedure as demonstrated by adequate urinary output and blood pressure and filling pressures within normal limits.
The patient demonstrates wound and tissue perfusion consistent with or improved from identified preoperative baseline levels.
Determines knowledge level, assesses readiness to learn, and identifies barriers to communication. Explains sequence of events and reinforces teaching about treatment options. Provides instruction (ie, verbal, written) for surgical procedure and discharge based on identified need. Communicates patient concerns to appropriate surgical team members. Evaluates response to instruction.
The patient verbalizes decreased anxiety and an ability to cope.
The patient demonstrates knowledge of the expected response to the procedure and discharge care.
Assesses patient’s pain preoperatively. Identifies patient’s accepted postoperative pain threshold. Provides pain management instruction and pain scale to assess pain control. Implements pain management guidelines. Evaluates patient’s response to pain management interventions.
The patient demonstrates adequate pain management, and vital signs are equal to or improved from preoperative values.
The patient demonstrates and reports adequate pain control throughout the perioperative period.
Monitors for fluid deficit. Monitors for signs of hypervolemia and hypovolemia. Monitors color and amount of urine output from urinary catheter.
The patient’s urinary output is within normal range at discharge.
The patient’s fluid, acidbase, and electrolyte balances are consistent with or improved from preoperative baseline levels.
Monitors patient’s body temperature. Implements thermoregulatory measures, to include • offering warm blankets and solutions and • applying temperature-regulating blanket or other warming devices when applicable.
The patient’s temperature is within normal limits at discharge.
The patient is at or returning to normothermia at the conclusion of the perioperative period.
Nursing interventions
• •
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site from chin to knees and lateral to the nipple line. The surgeon and scrub person then place the surgical drapes on the patient and the suction and ESU pencil on the sterile field. PLACING THE PATIENT ON CPB. The surgeon makes a median sternotomy incision from the sternal notch to the xiphoid process and opens the sternal bone using a reciprocating saw. The surgeon uses electrosurgery and bone wax to obtain sternal-edge hemostasis and then secures a Morse sternal retractor in place to expose the patient’s heart. He or she then opens the pericardium using Debakey forceps and Metzenbaum scissors and uses silk suture for pericardial stay stitches. After the pericardium is open, the surgeon dissects the aorta, superior vena cava (SVC), and inferior vena cava (IVC) and starts dissecting posteriorly to the interatrial groove. The anesthesia care provider administers heparin and checks the patient’s activated clotting time (ACT) after three minutes. The ACT test is used to monitor the effectiveness of high-dose heparin therapy administered during CPB surgery. High-dose heparin anticoagulation during CPB is necessary to reduce the risk of microthrombi that result from the extracorporeal manipulation of blood. The ACT test is used to demonstrate the inability of the patient’s blood to coagulate rather than quantifying the ability to clot. The surgeon places the aortic, SVC, and IVC purse-string sutures as the scrub person brings the CPB lines to the field and prepares them in anticipation of cannulation. The surgeon places a 7-mm aortic cannula in the ascending aorta and secures it with tourniquets and a 0-silk stitch. He or she places SVC and IVC cannulae and secures them with tourniquets and silk ties. The surgeon places a left ventricular catheter in the patient’s inferior pulmonary vein and an antegrade cardioplegia needle in
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the ascending aorta. The perfusionist initiates bypass via the SVC only while the surgeon completes posterior dissection to the interatrial groove. Before the surgeon opens the left atrium, the aorta must be crossclamped. If air is allowed to enter the left atrium, and subsequently, the left ventricle, the air becomes High-dose heparin an air embolism that may travel up the ventricular anticoagulation outflow tract through the aortic valve and into the during vessels coming off the aortic arch that feed the cardiopulmonary cranium. An air embolism is a serious complibypass is cation that can cause a stroke. When the left atriused to reduce um is dissected, the surthe risk of geon places a cross clamp on the aorta and applies microthrombi saline slush to the heart. The perfusionist begins that result from to cool the patient to 32º C (89.6º F) using cold solutions and initiates the extracorporeal total CPB.
MITRAL VALVE REPAIR TECHNIQUES
manipulation of blood.
Surgeons have a variety of techniques to choose from to repair the mitral valve (eg, annuloplasty, slidingplasty, chordal repair/ transfer/replacement, valve replacement). Vital to these repairs is proper exposure of the mitral valve and its complex valvular mechanism. The appropriate technique can only be decided after direct analysis of the valve and its corresponding structures. The circulating nurse must be prepared for any and all changes in the procedure based on this analysis. The inventory of annuloplasty devices must be maintained at sufficient levels and readily accessible. The assistance of AORN JOURNAL •
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Figure 3 • Placement of annuloplasty rings.
Figure 4 • C-shaped mitral valve implant. (Figure courtesy of Edwards Lifesciences, Irvine, Calif)
support service personnel, such as purchasing and inventory stocking personnel, is essential to an efficient system. The circulating nurse also must maintain a stock of suture and be prepared to use additional suture as the procedure progresses. Surgeon preference sheets must be maintained and updated to indicate the preferred annular devices and suture. After the surgeon has exposed the mitral valve apparatus, he or she opens the patient’s left atrium using Metzenbaum scissors. The incision extends from distal end of the intra-atrial groove to just below the SVC. At this point, the surgeon places the mitral valve retractor using a basket and one malleable blade to expose the annulus, leaflet tissue, or disrupted chords. He or she uses a Debakey forceps and nerve hooks to assess the mitral leaflets and chords and to plan the repair.
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The surgeon looks for redundant leaflet tissue and calcified or disrupted chords. The surgeon uses a #15 blade and Jamison scissors to dissect any leaflets or chords that need repair. The scrub person prepares the disposable suture guides and the 2-0 braided, coated, polyester valve suture. The surgeon performs any necessary • leaflet repairs using a 4-0 braided, coated, polyester suture; • chordal repairs with a 5-0 monofilament polypropylene suture; and • chordal replacement with 4-0 expanded, polytetrafluroethylene (ePTFE) suture. He or she then places the suture guides in a triangle around the mitral valve retractor and places 2-0 braided coated polyester sutures in the mitral annulus, alternating green- and white-colored suture. The surgeon tags the trigone sutures with mosquito clamps on which rubbershods have been placed. When all sutures are placed, the surgeon sizes the annulus by measuring the anterior leaflet from annulus to the beginning of the zone of coaptation.5 Choosing the appropriate annulus size is based on the theory that undersizing is appropriate for mitral regurgitation when it is related to left ventricular enlargement.5 The circulating nurse confirms the size and type of implant with the surgeon and delivers the implant to the scrub person. In geometric disease, a full ring is used to reduce the size of the dilated annulus. In valvular disease, however, a C-shaped ring is used to reinforce the repair. The scrub person places the annular implant on the holder and hands it to the surgeon. The surgeon places individual 2-0 braided, coated, polyester valve sutures in the annular ring or band. One-third of the sutures are
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Figure 5 • Complete ring mitral valve implant. (Figure courtesy of Edwards Lifesciences, Irvine, Calif)
placed and then tagged with mosquito clamps, and then the surgeon cuts off and returns the needles to the scrub person. The surgeon repeats this procedure for the remaining two-thirds of the valve suture. After all valve sutures have been placed in the ring, the surgeon slides the ring down the suture and seats it along the mitral annulus. The surgeon removes the ring holder using a #15 blade and ties down the individual valve sutures to secure the ring and then closes the left atrium using 3-0 monofilament polypropylene suture. ANNULOPLASTY. The primary technique used to repair the mitral valve is annuloplasty (Figure 3). Annuloplasty is aimed at restoring the functional size and shape of the fibrous band to which the leaflets attach. When this band is returned to its optimal size and shape, leaflet coaptation is restored. An important concept in annular repair is that much of the dilation occurs at the more flexible posterior portion of the annulus.1 The annular shape is restored using an annular band. A variety of annular bands are available to the cardiac surgeon. The rings range in the degree of flexibility as well as shape. A C-shaped band (Figure 4) allows the anterior portion of the annulus to be preserved and function naturally, whereas a complete ring (Figure 5) supports both the anterior and posterior dimension. The degree of flexibility is important to consider when choosing a band because the band allows the annulus to adapt to changes during the cardiac cycle. When choosing a mitral annuloplasty repair device, all of these variables must be considered in relation to the etiology of the patient’s specific disease pathology. For the patient with left ventricular geometry changes, a three-dimensional shaped band (Figure 6) may contribute to the reversing/remodeling of the rounded shape of the ventricle. SLIDINGPLASTY. In addition to the annu-
loplasty, other repair techniques may be employed based on analysis of the structures of the individual valve. Leaflet defects can be repaired using the slidingplasty technique. These defects, commonly involving the P2 cusp, can be repaired using a quadrangular resection of the cusp and reapproximating the free edges of the remaining P1 and P3 cusps. Undermining the leaflet tissue along the annulus allows the remaining tissue to approximate. The surgeon then reattaches the leaflet edges to the annulus using a 4-0 monofilament, polypropylene interrupted suture. CHORDAL REPAIR, TRANSFER, OR REPLACEMENT. Chordal repairs are accomplished based on the etiology of the patient’s specific
Figure 6 • Threedimensional, shaped mitral valve band implant (Figure courtesy of Edwards Lifesciences, Irvine, Calif)
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SIDEBAR
Systolic Anterior Motion
S
ystolic anterior motion (SAM) may occur when
a relatively large posterior mitral valve leaflet [that is coapting] with the anterior mitral valve leaflet closer to its base [causes] both an anterior shift of the coaptation point and an increase in the amount of redundant leaflet tissue in the left ventricular outflow tract.1(p179)
Lee et al2 reported that the incidence of SAM after mitral valve repair is 1% to 2%. More recently, Sternik and Zehr3 reported the incidence of SAM to be 4% to 5%. Often, SAM is noted after the mitral repair is complete and separation from cardiopulmonary bypass (CPB) is initiated. Walkes and Reardon4 assessed patients for SAM via TEE after separation from CPB. Performing an intraoperative transesophageal echocardiogram (TEE) provides a mechanism for diagnosing this phenomenon. Correction of SAM often requires reestablishing CPB and resecting the redundant anterior leaflet tissue in the left ventricular outflow tract. Several preventative surgical techniques have been suggested to prevent the need for an additional episode of CPB. Sternik and Zehn3 advocate tethering the mid segment of the anterior leaflet to prevent the leaflet from flipping into the left ventricular outflow tract. Quigley1 suggests using an elliptical excision of the body of the anterior mitral valve leaflet and simple closure, thus reducing the height of the anterior mitral valve leaflet by approximately 5 cm. If SAM is observed, ionotropic agents and volume loading are instituted to reduce after-load. The TEE is then repeated. If SAM is still observed, CPB is again established and the initial repair is reexamined. 1. Quigley RL. Prevention of systolic anterior motion after repair of severely myxomatous mitral valve with an anterior leaflet valvuloplasty. Ann Thorac Surg. 2005;80:179-182. 2. Lee KS, Stewart WJ, Lever HM, et al. Mechanism of outflow tract obstruction causing failed mitral valve repair. Anterior displacement of leaflet coaptation. Circulation. 1993;88:1124-1129. 3. Sternik L, Zehr KJ. Systolic anterior motion of the mitral valve after mitral valve repair. Tex Heart Inst J. 2005;32:47-49. 4. Walkes JM, Reardon MJ. Status of mitral valve surgery. Curr Opin Cardiol. 2004;19:117-122.
disease pathology. Elongation of the anterior leaflet chord can be repaired by invaginating the excessive chord into the papillary muscle.8 The surgeon uses a 5-0 polypropylene suture to bury the chord into the papillary muscle. Chordal
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transfers can be performed to repair ruptured chords. This can only be employed if suitable chords are available; in which case, the surgeon uses a 4-0 polypropylene suture to secure the chord to the leaflet. Chordal replacement can be used when suitable chords are not available for transfer. A suitable replacement material for chords is ePTFE suture. This replacement technique consists of passing the suture through the papillary muscle and then through the leaflet edge. The surgeon takes special care to determine the length of the chord to ensure accurate length of the replacement material. VALVE REPLACEMENT. Mitral valve repair and preservation of the subvalvular apparatus (ie, chordae and papillary muscles) contributes to the maintenance of left ventricular geometry and function. The decision to replace a valve that is beyond repair is based on the mechanism causing the regurgitation or stenosis. In the case of ischemic mitral valve regurgitation, repair is almost always possible because the underlying issue is the changing geometry of the left ventricle. This changing geometry can be reversed using an appropriately designed annuloplasty ring. Complex mitral valve repair may be a challenge. Replacement may be the only option for severe valvular disease.
WEANING OFF CPB AND CLOSING THE WOUND The perfusionist begins to warm the patient slowly to 37º C (98.6º F). The surgeon places temporary ventricular and atrial pacing wires because electrolyte imbalances, trauma to conductive tissue, and previously undetected conduction disturbances can contribute to postoperative dysrhythmias.4 The scrub person passes the pacing cables off the field to the anesthesia care provider who sets the temporary pacemaker to fully automatic pacing. The surgeon removes the aortic
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SIDEBAR
Protamine Sulfate
P
rotamine sulfate, a mixture of simple proteins obtained from the sperm or testes of suitable species of fish, usually salmon, is used to neutralize the anticoagulation effect of heparin. It commonly is used in instances of extracorporeal circulation, such as dialysis or cardiac surgery, in which cardiopulmonary bypass is used. Protamine also is used in some insulin preparations to delay the absorption of insulin. Protamine does have anticoagulant effects when administered in the absence of heparin.1 Protamine is supplied in a 10 mg/mL solution for injection. The standard adult dosage is 1 mg IV for every 100 units of heparin remaining in the patient. Protamine must be administered slowly over a period of 10 minutes because administering it too quickly may result in severe hypotension and anaphylactic reaction. Activated clotting time results should be used to monitor the effect of protamine in neutralizing heparin. Adverse reactions to protamine are an antigen-antibody response that can result in cutaneous symptoms (eg, skin flushing, pruritus) or systemic symptoms (eg, hypotension, bradycardia) and anaphylaxis.2 Precautions related to protamine administration should be taken for patients who have been exposed to protamine in the past through use of protamine-containing insulin or previous heparin neutralization during dialysis or CPB. Caution should be used for patients with a history of fish allergy as they may develop a sensitivity reaction. Men who have had a vasectomy are at increased risk for a protamine reaction. During a vasectomy the normal ejaculatory path is occluded and sperm are absorbed systemically. This systemic reabsorption may stimulate antibody production.3 Patients who have an increased risk for protamine reaction may be treated before initiation of CPB. Loubser 4 demonstrated that activation of the anaphylactic response mediated by complement activation is inhibited by high-dose methylprednisolone pretreatment before initiation of CPB. Diphenhydramine and ranitidine also can be used as pretreatment for patients with increased risk factors for protamine reaction. Health care providers administering protamine must be aware of possible risk factors that could result in a protamine reaction. Protamine should only be administered by health care providers who are trained in resuscitation techniques and the treatment of anaphylactic shock. Health care providers should continually assess the patient for flushing, nausea, vomiting, dyspnea, hypotension, and bradycardia and then promptly treat the patient to avoid potential catastrophic outcomes. 1. DRUGDEX DRUG EVALUATIONS—Protamine. In: MICROMEDEX(R) Healthcare Series [subscription database online]. Greenwood Village, Colo: Thomson MICROMEDEX; 2005. 2. MARTINDALE-The Complete Drug Reference—Protamine. In: MICROMEDEX(R) Healthcare Series [subscription database online]. Greenwood Village, Colo: Thomson MICROMEDEX; 2005. 3. Porsche R, Brenner ZR. Allergy to protamine sulfate. Heart Lung. 1999;28:418-428. 4. Loubser J. Effect of methylprednisolone on complement activation during heparin neutralization. J Cardiovasc Pharmacol. 1997;29:23-27.
cross clamp, and the perfusionist begins to wean the patient off bypass as a cardiologist performs a postoperative TEE to assess the function of the repaired valve, comparing it to the preoperative TEE. The surgeon also uses the TEE to diagnose the presence of systolic anterior motion and to identify air in the left ventricle. When it is confirmed that there is no air in the heart, the surgeon removes the left ventricular catheter and antegrade cardioplegia cannulae. If the surgeon identifies air in the heart, the anesthesia care provider places the patient in a slight Trendelenburg position. The surgeon then manually manipulates the heart to allow the air to
remain in the left ventricle so the air can be removed by the ventricular catheter. After the patient is completely weaned off CPB, the surgeon removes the SVC and IVC cannulae. The surgeon then inserts two mediastinal chest tubes and secures them with 0-silk sutures. The anesthesia care provider slowly administers protamine, at which point the circulating nurse and scrub person begin the sponge, needle, and instrument counts. The surgeon is notified of any discrepancies in the counts. The surgeon removes the aortic cannula, closes the pericardium, and removes the sternal retractor. He or she assesses the sternal edges for bleeding AORN JOURNAL •
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and uses bone wax and electrosurgery as needed to control bleeding. The surgeon then closes the sternum using eight #5 wires, and connects the chest tubes to continuous suction via a threechambered, underwaterseal, pleural drainage system. The surgeon closes the subcutaneous tissue The nurse using 0 and 2-0 monofilainitiates use of ment, polydioxanone suture and closes the skin with 4-0 monofilament, the incentive poliglecaprone suture. The spirometer with circulating nurse, anesthesia care provider, and surgeon transport the patient coughing and directly to the thoracic intensive care unit (ICU). deep breathing
immediately after extubation and helps the patient sit on the side of the bed within six hours of extubation.
POSTOPERATIVE PHASE
At University Hospital, Ann Arbor, Mich, postoperative care is guided by a critical pathway developed for the uncomplicated CBP procedure. The surgical day includes direct admission to the thoracic ICU from the OR. Initial postoperative laboratory tests include a CBC with platelets; an electrolyte (eg, potassium) count; and an arterial blood gas. An ICU nurse ensures that a chest x-ray is performed when the patient is admitted to the ICU. The nurse ensures that the patient regains and maintains normothermia by using a temperatureregulating blanket and warmed IV solutions and obtains the patient’s vital signs, including assessment of pain • every 15 minutes until rewarming is complete (ie, to 37° C [98.6° F]) and then • every four hours until discharged from the ICU, or as needed. The surgical resident extubates the
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patient as soon as possible (ie, usually within four to eight hours) and places the patient on 6 L of oxygen via nasal cannula. The ICU nurse monitors the patient’s mediastinal chest tubes and pleural drainage system for excessive (ie, more than 200 mL/hour) or increasing drainage. The ICU nurse replaces potassium to maintain levels between 4.0 mEq/L and 5.2 mEq/L. He or she administers morphine, the pain medication of choice, as needed and continues IV administration of antibiotics (eg, cefazolin or vancomycin) for 48 hours. The ICU nurse also administers heparin subcutaneously for platelet counts greater than 100,000/mL3. When the patient is extubated, the nurse advances the patient’s diet from clear liquids to full liquids, then to a full liquid, low cholesterol, no-addedsodium diet. The nurse initiates use of the incentive spirometer with coughing and deep breathing immediately after extubation and helps the patient sit on the side of the bed within six hours of extubation. The cardiologist sets the atrioventricular-sequential pacemaker to fully automatic pacing. On the first postoperative day, the surgical resident removes the pulmonary artery catheter and arterial lines after the patient is determined to be hemodynamically stable. The ICU nurse removes the indwelling urinary catheter on the first postoperative day. The nurse weans the patient from morphine to use of oxycodone/acetaminophen as soon as the patient is able to take oral medications and according to the patient’s acceptable pain threshold. The ICU nurse prepares the patient for transfer to the cardiac step-down unit, usually by the first postoperative day. In the cardiac step-down unit, the assigned nurse encourages the patient to ambulate in the halls three times per day. The nurse advances the patient from a full liquid to a regular diet with
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no added sodium and low cholesterol. The sternal dressing remains in place and the nurse reinforces it as needed. The nurse adds one aspirin per day to the patient’s medication regimen. On the second postoperative day, the surgical resident removes the mediastinal chest tubes if drainage is less than 50 mL in eight hours and applies an occlusive dressing over the chest tube sites for 24 hours. A chest x-ray is taken after the chest tubes are removed to ascertain that the patient’s lungs remain reinflated. The surgical resident removes the sternal dressing and the nurse cleans the incision with normal saline, after which the nurse covers the incision only if the wound is draining. The nurse and physical therapist ensure that the patient ambulates four times a day. The nurse adds a stool softener to the patient’s medication regimen and begins to teach the patient and his or her family members about the medication regimen to be followed at home after discharge. On the third postoperative day, the nurse ensures that discharge laboratory tests are performed including a CBC with platelet count. The surgical resident, nurse practitioner, or physician’s assistant removes the pacing wires if the patient’s heart rhythm is stable. The nurse begins teaching the patient and his or her family members about wound care and makes final discharge plans and orders any needed home supplies. The nurse then removes any remaining peripheral IV lines. The nurse discharges the patient on the fourth postoperative day with instructions about medications and wound care. He or she instructs the patient to continue using the incentive spirometer and performing coughing and deep breathing exercises. The nurse ensures that an appointment is made for a one-month follow-up in the cardiac surgery clinic and gives the
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patient instructions on how to contact the surgical resident should any questions arise.
CONCLUSION Treatment of mitral valve disease has evolved from replacement to repair. Improved understanding of the underlying pathology has been an important part of this evolution. A variety of repair techniques used by experienced surgeons provide patients with the best possible outcomes. The next phase in the evolution of mitral valve repair is minimally invasive, robotic-assisted mitral valve repair.9 This technique uses robotic technology along with a right-chest endoscopic approach. Although use of this technique has been reported by other centers in the United States, it currently is not being used for mitral valve repair at the University of Michigan. ❖ Margo Winters, RN, BSN, CNOR, was the adult cardiac surgery education coordinator at University Hospital, University of Michigan Health System, Ann Arbor, Mich, at the time this article was written. Currently, she is a clinical systems trainer for the computerized physician order entry project at the University of Michigan. Pam Obriot, RN, BSN, is a RN first assistant and cardiac surgery education coordinator at University Hospital, University of Michigan Health System, Ann Arbor, Mich.
REFERENCES 1. Ho SY. Anatomy of the mitral valve. Heart. 2002;88(suppl 4):iv5-10. 2. Seifert PC. Cardiac Surgery Perioperative Patient Care. St. Louis: Mosby; 2002. 3. Finkelmeier BA. Cardiothoracic Surgical Nursing. Philadelphia: Lippincott, Williams & Wilkins; 1995:21-22. 4. Thompson JM, McFarland GK, Hirsh JE, et al. Mosby’s Clinical Nursing. St Louis: Mosby; 1986. AORN JOURNAL •
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5. Walkes JM, Reardon MJ. Status of mitral valve surgery. Curr Opin Cardiol. 2004;19: 117-122. 6. Wells FC, Shapiro LM. Mitral Valve Disease. Oxford: Butterworth-Heinemann, Ltd; 1996. 7. Nowicki ER, Weintraub RW, Birkmeyer NJ, et al. Mitral valve repair in northern New
England. Am Heart J. 2003;145:1058-1062. 8. Savage EB, Bolling SF. Atlas of Mitral Valve Repair. Philadelphia: Lippincott, Williams & Wilkins; 2006. 9. Woo YJ, Nacke EA. Robotic minimally invasive mitral valve reconstruction yields less blood product transfusion and shorter length of stay. Surgery. 2006;140:263-267.
Computer System May Improve Weaning From Ventilators
P
atients with acute respiratory failure who are on ventilation in the intensive care unit (ICU) have a shorter duration on mechanical ventilation when placed on a computerized system of weaning from the ventilator, according to an Oct 16, 2006, news release from The American Thoracic Society. Compared to typical physician-controlled management of the weaning process, the computer-driven system resulted in a reduction in patients’ time on mechanical ventilation from 12 days to 7.5 days and a reduction in length of ICU stays from 15.5 days to 12 days. The computerized system introduces an automatic, gradual reduction in pressure support; initiates automatic spontaneous breathing trials; and generates an incentive message when the patient’s
spontaneous breathing trial is successful. Additionally, patients who were weaned using this computerized system had a 30% reduction in total number of ventilator-related complications, including • reintubation, • self-removal from ventilator assistance, • need for noninvasive ventilation, • mechanical ventilation longer than 21 days, and • tracheotomy. Computer-Driven System Reduces Patient Mechanical Ventilation Time Significantly [news release]. New York: American Thoracic Society; October 16, 2006. Available at: http://www.eurekalert.org/pub_releases/2006-10 /ats-csr100506.php. Accessed October 27, 2006.
Poor Have Higher Risk of Death in Some Neighborhoods
R
esearchers investigating income and education data in comparison to the socioeconomic status of a person’s neighborhood determined that people of low socioeconomic status living in affluent neighborhoods have an increased risk of death, according to an Oct 31, 2006, news release from the Stanford University School of Medicine, Stanford, Calif. This trend was discovered after researchers analyzed data from a previous study of 8,200 men and women from 82 neighborhoods in several California towns for a 17year period. The researchers determined that 19 out of every 1,000 women of low socioeconomic status who lived in wealthier neighborhoods had died after 17 years, compared to 11 out of every 1,000 women who lived in poorer neighborhoods. Although less dramatic, a similar trend was found in men. The differences in death rates became more pronounced over time, and were not found to be related to age; cause of death; or risk factors such
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as obesity, hypertension, or smoking. It is possible that the higher cost of living in wealthy neighborhoods reduces the amount of disposable income that people of low socioeconomic status have to spend on essential goods and services such as health care and healthy food. A poor person in a wealthier neighborhood might not have access to free social services made available in low-income neighborhoods. It also is possible that people of lower socioeconomic status, in comparing themselves with their neighbors, fare worse in this socioeconomic setting for psychological and social reasons. Poor People in Well-To-Do Neighborhoods Face Higher Death Rates, Stanford Study Finds [news release]. Stanford, Calif: Stanford University School of Medicine; October 31, 2006. Available at: http://mednews.stanford .edu/releases/2006/october/neighborhood.html. Accessed November 6, 2006.
Mitral Valve Repair Margo Winters, RN; Pam Obriot, RN indicates that continuing education contact hours are available for this activity. Earn the continuing education contact hours by reading this article and taking the examination on pages 167-168 and then completing the answer sheet and learner evaluation on pages 169-170 You also may access this article online at http://www.aorn journal.org.
T
he first treatment for mitral valve disease came shortly after the invention of the heart-lung bypass machine.1 Direct visualization of the mitral valve made replacement surgery possible. The negative aspects of mitral valve replacement, however, include possible thromboembolism, hemolysis, and infection. This led cardiothoracic surgeons to search for other methods to treat mitral valve disease. As physicians began to understand the complex function and geometry of the mitral valve and the subvalvular apparatus, repair techniques evolved, and mitral valve repair soon became the gold standard in mitral valve treatment.1 The number of mitral valve repair cases has increased during the last decade as new knowledge and increased experience has offered new treatments for valvular repair.2 This article describes typical mitral valve repair procedures
ABSTRACT •
DISEASES THAT AFFECT the mitral valve include mitral regurgitation, mitral stenosis, rheumatic heart disease, and cardiomyopathy.
•
THE RESULTS OF DIAGNOSTIC procedures are used to identify and confirm mitral valve disease, evaluate the patient’s anatomy, and determine the severity of the disease.
•
AFTER THE PATIENT IS PREPARED for surgery, the surgeon performs an intraoperative transesophageal echocardiogram and the patient is placed on cardiopulmonary bypass.
•
A REPAIR PROCEDURE (eg, annuloplasty, slidingplasty, chordal repair/transfer/replacement, valve replacement) is performed depending on the patient’s specific anatomical abnormalities. AORN J 85 (January 2007) 152-166. © AORN, Inc, 2007.
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performed on a daily basis at the University of Michigan Health System, Ann Arbor, Mich. Table 1 provides definitions of common medical terms associated with mitral valve repair.
MITRAL VALVE DISEASE PROCESSES Two types of disease processes (ie, geometric and valvular) affect the mitral valve. The type of disease process determines the appropriate type of repair. GEOMETRIC DISEASE. Geometric disease, also referred to as ventricular disease, is mitral regurgitation originating within the left ventricle. In geometric mitral disease, the left ventricle has dilated so much that the mitral annulus has stretched and the mitral valve leaflets can no longer coapt (ie, come together). Geometric disease can be ischemic or nonischemic in origin. The most common form of ischemic heart failure is myocardial infarction. In the presence of coronary artery disease, narrowing or obstruction of an artery causes decreased myocardial perfusion.3 Occlusion of the artery can be caused by platelet aggregation, thrombotic embolism, dislodged calcium plaque, or coronary artery spasm. This ischemia leads to necrosis of the myocardial tissue. Persistent necrosis interferes with myocardial function and eventually can produce large areas of akinetic tissue (ie, tissue that has lost the ability to move).3 There are many causes of nonischemic heart disease, but the heart’s decreased ability to pump effectively ultimately results in cardiomyopathy. Some causes of nonischemic heart disease are hypertension and infections such as endocarditis.3 The most common cause of geometric disease is dilated cardiomyopathy. In geometric mitral disease, the valve and © AORN, Inc, 2007
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TABLE 1
Common Medical Terms Associated with Mitral Valve Repair Annulus
Mitral regurgitation
A ring-like structure; a fibrous band of tissue which serves as the attachment point for the leaflets
A backward flowing of blood into the left atrium of the heart caused by an incompetent mitral valve
Annuloplasty
Mitral stenosis
Surgical repair of a deformed annulus surrounding a diseased mitral valve
Obstruction to the flow of blood through the mitral valve, usually caused by narrowing of the valve orifice
Bicuspid valve
Subvalvular apparatus
A valve consisting of two leaflets (eg, the mitral valve)
Coaptation
Chordae tendineae and papillary muscles within the left ventricle that contribute to the geometry and function of the mitral valve
The proper joining or fitting together of two surfaces (eg, mitral valve leaflets)
Trigone
Geometric mitral disease
Valvular mitral disease
A dysfunction of the mitral valve related to dilation of the left ventricle
Three angled section on the ends of the fibrous region between the aortic and mitral valves Valve dysfunction related to issues of the valve or subvalvular apparatus
Left ventricular outflow tract
Zone of coaptation
A pathway from which blood exits the left ventricle and passes through the aortic valve
Rough surface of mitral valve leaflets that join together during left ventricular systole
subvalvular apparatus are all normal. The problem is within the ventricle, which has become dilated to the extent that the normal function of the valve is disrupted. VALVULAR DISEASE. Valvular mitral disease is a process in which the leaflets and/or the annulus have become calcified and stiff or fused. In addition to calcification, valvular disease also may include chordal shortening, which may lead to mitral stenosis or regurgitation. In the United States, valvular disease most commonly is caused by rheumatic endocarditis.4 Whatever the etiology, most patients will have some degree of dilation in the mitral annulus that must be repaired.5
MITRAL VALVE ANATOMY
AND
PHYSIOLOGY
The bicuspid (ie, two leaflet) mitral valve is located between the left ventricle and left atrium. The valvular complex consists of the annulus, leaflets, chordae tendineae, and papillary muscles (Figure 1), and in a sense, the left ventricle is the mitral valve. The annu-
lus, a fibrous band of tissue from which the leaflets originate, is considered the “hinge line” of the valve leaflets.6 Continuing out from the annulus, the two leaflets (ie, anterior and posterior) are pale yellow, thin, fibroelastic membranes whose anterior surfaces are relatively smooth. The posterior or ventricular surfaces are slightly irregular because of the attachments to the chordae tendineae. The anterior leaflet is also known as the anteromedial, septal, or aortic leaflet.4 The posterior leaflet, also known as the mural leaflet, is further divided into three cusps commonly known as P1, P2, and P3. The three posterior cusps do not have separate functions; they have been named purely for ease of describing mitral valve anatomy and locations of regurgitation jets (ie, flashes of backward blood flow). The chordae tendineae are attached to the inferior surface of the leaflets. These white, cord-like tendons act only as guides to assist in the coaptation of the two leaflets. The chordae tendineae AORN JOURNAL •
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Figure 1 • Interior view of the heart showing the mitral valve and subvalvar apparatus.
left atrium posterior leaflet anterior leaflet chordae tendinae papillary muscle left ventricle
preventing the backwards flow (ie, regurgitation) of blood into the left atrium. The chordae tendineae guide the leaflets into position; the chordae do not pull the leaflets together. This forms a tight closure (Figure 2), preventing mitral regurgitation and allowing the forward flow of blood through the left ventricular outflow tract, through the aortic valve, and out into the aorta. The function of the mitral valve is regulated by interaction of the components of the mitral apparatus (ie, leaflets, chordae tendineae, papillary muscles, ventricular wall). The mitral apparatus contributes to the normal geometry and function of the left ventricle.
CAUSES
Figure 2 • Normal mitral valve in closed position.
also prevent the leaflets from billowing or everting up into the atrium. If a primary chordae ruptures, the leaflet everts into the atrium and is called a “flail” leaflet. The chordae are attached to the papillary muscles at the base of the left ventricle. Oxygenated blood originating from the lungs flows through the pulmonary veins and collects in the left atrium. When pressure in the left atrium is greater than the pressure in the left ventricle, the mitral valve opens allowing blood to flow into the left ventricle. As the intraventricular pressure rises, the mitral valve closes (ie, the leaflets coapt)
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OF
MITRAL ABNORMALITIES
Numerous diseases affect the ability of the mitral valve to function properly. Some of these diseases include mitral regurgitation, mitral stenosis, rheumatic heart disease, and cardiomyopathy. MITRAL REGURGITATION. Mitral regurgitation also is referred to as incompetence or insufficiency. Regurgitation is a result of the leaflets not coming together completely. An incompetent mitral valve allows backflow of blood into the left atrium. This backward flow in turn leads to increased atrial volume and eventually leads to backward flow of blood into the lungs. This backflow into the lungs leads to pulmonary edema. As a result of this blood flow back-up, many patients with mitral regurgitation present to their primary care physician with signs and symptoms of right heart failure.2 The heart works harder to try to compensate for the lost forward blood flow; the ventricles may begin to hypertrophy (ie, thicken) because of the added workload. If there is an ischemic area in the left ventricle from a myocardial infarction, the tissue can weaken and become stretched, forming an aneurysm, and become dysfunctional.
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MITRAL STENOSIS. Mitral stenosis refers to the calcification of the leaflet and annulus. A stenotic mitral valve also leads to heart failure in much the same way as mitral regurgitation, but instead of blood moving backwards through the mitral valve, mitral stenosis does not allow enough blood through the narrowed, fused, or calcified opening of the mitral valve leaflets. The process continues much the same as is seen in mitral regurgitation, resulting in right heart failure as blood volume builds up in the lungs. Stenotic valve repair is more complicated than repair of a dilated mitral annulus and requires more experience on the part of the surgeon.5 The surgeon must make decisions about excising calcified valvular tissue and possibly replacing chordae or advancing leaflets. Each patient’s valve is different regarding the degree of stenosis and involvement of the chordae tendineae and papillary muscles. RHEUMATIC HEART DISEASE. Rheumatic heart disease has decreased in the United States in recent decades as a result of effective antibiotic treatment of streptococcal (ie, strep) infections.4 Untreated strep infections lead to rheumatic fever in which antibodies produced by the body to fight the infection also attack heart valve leaflet tissue, most commonly the mitral valve. In developing countries, children often do not receive therapeutic antibiotic treatments, so they constantly are reinfected with strep. These countries still have large populations with rheumatic heart disease, which is the leading cause of cardiovascular death in young adults.7 Infective endocarditis is a form of rheumatic heart disease seen more often in the United States. This disease can be caused by contamination of the blood as a result of illicit IV drug use,7 dental procedures, or surgical infections. The bacteria attach themselves to the mitral valve leaflets causing
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scarring; erosion; and ultimately, varying degrees of stenosis. CARDIOMYOPATHY. Although cardiomyopathy can be caused by neuromuscular or connective tissue disorders, alcohol abuse, viral infections, or exposure to cardiotoxic substances, most cases are of unknown origin (ie, idiopathic).4 The most common medical condition of patients older than age 65 is congestive heart failure (CHF).3 Chronic CHF can lead to dilated cardiomyopathy, which causes the mitral annulus to stretch, resultUntreated ing in mitral regurgitation. The geometric mitral streptococcal valve repair procedure to resolve this problem is the infections may simplest procedure to perform. This geometric discause rheumatic ease can be reversed with the placement of an annuloplasty device. Mitral fever in which the valve repair does not cure body’s antibodies CHF but can relieve the acute symptoms of mitral regurgitation and, ideally, fight the infection keep the patient off the but also attack heart transplant list longer.
DIAGNOSTICS
heart valve leaflet tissue, most commonly the mitral valve.
A variety of diagnostic procedures are performed to identify and then confirm mitral valve disease. After mitral valve disease is confirmed, diagnostic procedures can help evaluate the patient’s anatomy and determine the severity of the disease. PHYSICAL EXAMINATION. During any routine physical examination, general practitioners can detect a heart murmur— one sign of mitral regurgitation—by auscultation. If a health care provider is seeing a patient regularly, early detection of a heart murmur can result in early diagnosis and, more importantly, early treatment.
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CARDIAC CATHETERIZATION. In mitral valve disease, cardiac catheterization is used to confirm the diagnosis, assess ventricular function, discover other cardiac lesions, and evaluate coronary anatomy. Mitral regurgitation is confirmed by left ventriculography during cardiac catheterization. With the patient under light sedation, a cardiinserts a catheter A transesophageal ologist through the femoral artery injects an x-ray conechocardiogram and trast agent into the chamber. Fluoroscopy is used is a useful to document the dye flow as it regurgitates into the intraoperative left atrium. TRANSTHORACIC ECHOCARDIOtool to more GRAM. With acute mitral regurgitation, a surface accurately echocardiogram can detect determine valve abnormalities attributed to a ruptured chordae papilanatomy, annular lary muscle or perforated valve leaflet. The goal of transthoracic echocardiosize, and the gram is to identify the degree of mitral degree of regurgitation and valvular abnormality.5 Furthermore, addivalve disease tional information on left and assess for a atrial enlargement, right ventricular enlargement, regurgitant jet. and left ventricular dimensions can be obtained from an echocardiogram. TRANSESOPHAGEAL ECHOCARDIOGRAM (TEE). A preoperative TEE allows anatomy to be defined, assesses the degree of mitral regurgitation, and measures left ventricular function. The direction of the mitral regurgitation jet seen on a TEE can identify which leaflet is flailing or prolapsing. An anteriorly directed jet indicates a posterior leaflet prolapse or flail; whereas a posteriorly directed jet indicates an anterior leaflet prolapse or flail.1 A centrally directed jet may indicate annular dilation.
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Intraoperatively, the TEE is a useful tool to more accurately • determine valve anatomy, • assess the degree of the mitral valve disease, • assess the degree of regurgitation, • evaluate left ventricular function, • assess annular size and degree of enlargement, and • assess for a regurgitant jet. With the patient under anesthesia, a TEE probe is placed in the patient’s esophagus so that the probe lies behind the heart. The probe will remain in place throughout surgery. After the surgical repair has been performed, the surgeon will clamp the cardiopulmonary bypass (CPB) cannulas, fill the heart, and check the repair using a TEE. Based on this examination, the surgeon will decide if the repair is adequate. If the surgeon decides that additional repairs are needed, CPB will be reinitiated.
PREOPERATIVE PHASE
OF
SURGERY
In the preoperative holding room, the circulating nurse assesses the patient and verifies the patient’s identity. Before any narcotics are administered, the nurse confirms the proposed procedure with the patient and his or her family members, cross checking the procedure with the surgical consent and OR schedule, and resolving any discrepancies with the surgeon before the patient is taken to the OR. The nurse performs an examination to assess the patient’s physical health status, emphasizing identification of cardiovascular risk factors, such as height, weight, presence of hypertension or diabetes, and use of alcohol or illicit drugs. He or she further identifies the patient’s relevant medical history (eg, chronic illnesses, injuries, surgeries), and obtains the patient’s medication history, including medication allergies, and any use of • aspirin or other anticoagulants and
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the date of discontinuation of those medications, • prescribed medications, • over-the-counter medications, and • herbal therapies. The circulating nurse notes the results of pertinent laboratory studies, such as chest x-rays and complete blood count (CBC). He or she ensures that the patient has undergone blood typing and cross-matching and that two units of packed red blood cells are available. After completing the history and physical examination and reviewing the medical record, the nurse develops a nursing care plan specific to this patient and the proposed surgical procedure (Table 2).
INTRAOPERATIVE PHASE The circulating nurse and anesthesia care provider transport the patient to the OR. To maintain the patient’s temperature during the preparatory phase of the procedure, the circulating nurse places a temperature-regulating blanket on the patient after helping make the patient comfortable on the OR bed and securing the safety strap and arm boards. The anesthesia care provider places a radial arterial line in the patient’s nondominant wrist and a central line with a pulmonary artery thermodilution catheter in the patient’s right internal jugular. OR SETUP. While the anesthesia care provider places the monitoring lines, the circulating nurse and scrub person prepare the sterile field. Standard cardiac trays are used along with a valve tray, mitral valve retractor, and the appropriate valve sizers. The scrub person prepares the aortic cannula, bicaval cannulae, left ventricular catheter for ventricular decompression, and antegrade cardioplegia needle. The circulating nurse and scrub person perform the sponge, needle, and instrument counts. The circulating nurse confirms
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that all sizes of required implants (eg, mitral annular bands and rings) as well as necessary suture for valve repair are available. PREPARING THE PATIENT. After the anesthesia care provider has secured the monitoring lines, all perioperative team members including the surgeon and anesthesia care provider actively participate in the surgical time out. The anesthesia care provider then induces the patient under general anesthesia, The direction of after which the circulating nurse inserts an inthe regurgitant dwelling urinary catheter with a temperaturejet helps sensing probe. The circulating nurse ensures that determine the the patient is in an anatomically correct, sumechanism of pine position and pads and tucks the patient’s regurgitation elbows at the patient’s sides. The circulating because the jet nurse then places the electrosurgical unit (ESU) flows in the dispersive pad on the patient’s buttock. opposite direction The direction of the regurgitant jet helps deterof the flailing or mine the mechanism of regurgitation because the prolapsing leaflet. jet flows in the opposite direction of the flailing or prolapsing leaflet.1 The anesthesia care provider ensures that preload, afterload, and blood pressure are controlled during the TEE examination so that the degree of mitral regurgitation is not distorted. The anesthesia care provider inserts the TEE probe, and performs a preoperative assessment of valve function. Ideally, the anesthesia care provider and the cardiologist should perform the TEE together because TEE interpretation may vary between observers.1 When the TEE is complete, the circulating nurse preps the patient’s surgical AORN JOURNAL •
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TABLE 2
Nursing Care Plan for Patients Undergoing Mitral Valve Repair Diagnosis Risk for alteration in tissue perfusion related to cardiopulmonary bypass
• • • • •
Risk for anxiety related to knowledge deficit and stress of surgery
• • • • •
Risk for acute or chronic pain related to surgical procedure
• • • • •
Risk for fluid volume imbalance
• • •
Risk for inadvertent hypothermia
Interim outcome criteria
Outcome statement
Assesses for preexisting conditions that predispose the patient to inadequate tissue perfusion. Identifies baseline tissue perfusion. Collaborates in fluid management. Monitors physiological parameters (eg, peripheral pulses, urinary output, blood pressure, filling pressures). Evaluates postoperative tissue perfusion.
The patient maintains adequate tissue perfusion throughout the procedure as demonstrated by adequate urinary output and blood pressure and filling pressures within normal limits.
The patient demonstrates wound and tissue perfusion consistent with or improved from identified preoperative baseline levels.
Determines knowledge level, assesses readiness to learn, and identifies barriers to communication. Explains sequence of events and reinforces teaching about treatment options. Provides instruction (ie, verbal, written) for surgical procedure and discharge based on identified need. Communicates patient concerns to appropriate surgical team members. Evaluates response to instruction.
The patient verbalizes decreased anxiety and an ability to cope.
The patient demonstrates knowledge of the expected response to the procedure and discharge care.
Assesses patient’s pain preoperatively. Identifies patient’s accepted postoperative pain threshold. Provides pain management instruction and pain scale to assess pain control. Implements pain management guidelines. Evaluates patient’s response to pain management interventions.
The patient demonstrates adequate pain management, and vital signs are equal to or improved from preoperative values.
The patient demonstrates and reports adequate pain control throughout the perioperative period.
Monitors for fluid deficit. Monitors for signs of hypervolemia and hypovolemia. Monitors color and amount of urine output from urinary catheter.
The patient’s urinary output is within normal range at discharge.
The patient’s fluid, acidbase, and electrolyte balances are consistent with or improved from preoperative baseline levels.
Monitors patient’s body temperature. Implements thermoregulatory measures, to include • offering warm blankets and solutions and • applying temperature-regulating blanket or other warming devices when applicable.
The patient’s temperature is within normal limits at discharge.
The patient is at or returning to normothermia at the conclusion of the perioperative period.
Nursing interventions
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site from chin to knees and lateral to the nipple line. The surgeon and scrub person then place the surgical drapes on the patient and the suction and ESU pencil on the sterile field. PLACING THE PATIENT ON CPB. The surgeon makes a median sternotomy incision from the sternal notch to the xiphoid process and opens the sternal bone using a reciprocating saw. The surgeon uses electrosurgery and bone wax to obtain sternal-edge hemostasis and then secures a Morse sternal retractor in place to expose the patient’s heart. He or she then opens the pericardium using Debakey forceps and Metzenbaum scissors and uses silk suture for pericardial stay stitches. After the pericardium is open, the surgeon dissects the aorta, superior vena cava (SVC), and inferior vena cava (IVC) and starts dissecting posteriorly to the interatrial groove. The anesthesia care provider administers heparin and checks the patient’s activated clotting time (ACT) after three minutes. The ACT test is used to monitor the effectiveness of high-dose heparin therapy administered during CPB surgery. High-dose heparin anticoagulation during CPB is necessary to reduce the risk of microthrombi that result from the extracorporeal manipulation of blood. The ACT test is used to demonstrate the inability of the patient’s blood to coagulate rather than quantifying the ability to clot. The surgeon places the aortic, SVC, and IVC purse-string sutures as the scrub person brings the CPB lines to the field and prepares them in anticipation of cannulation. The surgeon places a 7-mm aortic cannula in the ascending aorta and secures it with tourniquets and a 0-silk stitch. He or she places SVC and IVC cannulae and secures them with tourniquets and silk ties. The surgeon places a left ventricular catheter in the patient’s inferior pulmonary vein and an antegrade cardioplegia needle in
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the ascending aorta. The perfusionist initiates bypass via the SVC only while the surgeon completes posterior dissection to the interatrial groove. Before the surgeon opens the left atrium, the aorta must be crossclamped. If air is allowed to enter the left atrium, and subsequently, the left ventricle, the air becomes High-dose heparin an air embolism that may travel up the ventricular anticoagulation outflow tract through the aortic valve and into the during vessels coming off the aortic arch that feed the cardiopulmonary cranium. An air embolism is a serious complibypass is cation that can cause a stroke. When the left atriused to reduce um is dissected, the surthe risk of geon places a cross clamp on the aorta and applies microthrombi saline slush to the heart. The perfusionist begins that result from to cool the patient to 32º C (89.6º F) using cold solutions and initiates the extracorporeal total CPB.
MITRAL VALVE REPAIR TECHNIQUES
manipulation of blood.
Surgeons have a variety of techniques to choose from to repair the mitral valve (eg, annuloplasty, slidingplasty, chordal repair/ transfer/replacement, valve replacement). Vital to these repairs is proper exposure of the mitral valve and its complex valvular mechanism. The appropriate technique can only be decided after direct analysis of the valve and its corresponding structures. The circulating nurse must be prepared for any and all changes in the procedure based on this analysis. The inventory of annuloplasty devices must be maintained at sufficient levels and readily accessible. The assistance of AORN JOURNAL •
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Figure 3 • Placement of annuloplasty rings.
Figure 4 • C-shaped mitral valve implant. (Figure courtesy of Edwards Lifesciences, Irvine, Calif)
support service personnel, such as purchasing and inventory stocking personnel, is essential to an efficient system. The circulating nurse also must maintain a stock of suture and be prepared to use additional suture as the procedure progresses. Surgeon preference sheets must be maintained and updated to indicate the preferred annular devices and suture. After the surgeon has exposed the mitral valve apparatus, he or she opens the patient’s left atrium using Metzenbaum scissors. The incision extends from distal end of the intra-atrial groove to just below the SVC. At this point, the surgeon places the mitral valve retractor using a basket and one malleable blade to expose the annulus, leaflet tissue, or disrupted chords. He or she uses a Debakey forceps and nerve hooks to assess the mitral leaflets and chords and to plan the repair.
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The surgeon looks for redundant leaflet tissue and calcified or disrupted chords. The surgeon uses a #15 blade and Jamison scissors to dissect any leaflets or chords that need repair. The scrub person prepares the disposable suture guides and the 2-0 braided, coated, polyester valve suture. The surgeon performs any necessary • leaflet repairs using a 4-0 braided, coated, polyester suture; • chordal repairs with a 5-0 monofilament polypropylene suture; and • chordal replacement with 4-0 expanded, polytetrafluroethylene (ePTFE) suture. He or she then places the suture guides in a triangle around the mitral valve retractor and places 2-0 braided coated polyester sutures in the mitral annulus, alternating green- and white-colored suture. The surgeon tags the trigone sutures with mosquito clamps on which rubbershods have been placed. When all sutures are placed, the surgeon sizes the annulus by measuring the anterior leaflet from annulus to the beginning of the zone of coaptation.5 Choosing the appropriate annulus size is based on the theory that undersizing is appropriate for mitral regurgitation when it is related to left ventricular enlargement.5 The circulating nurse confirms the size and type of implant with the surgeon and delivers the implant to the scrub person. In geometric disease, a full ring is used to reduce the size of the dilated annulus. In valvular disease, however, a C-shaped ring is used to reinforce the repair. The scrub person places the annular implant on the holder and hands it to the surgeon. The surgeon places individual 2-0 braided, coated, polyester valve sutures in the annular ring or band. One-third of the sutures are
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Figure 5 • Complete ring mitral valve implant. (Figure courtesy of Edwards Lifesciences, Irvine, Calif)
placed and then tagged with mosquito clamps, and then the surgeon cuts off and returns the needles to the scrub person. The surgeon repeats this procedure for the remaining two-thirds of the valve suture. After all valve sutures have been placed in the ring, the surgeon slides the ring down the suture and seats it along the mitral annulus. The surgeon removes the ring holder using a #15 blade and ties down the individual valve sutures to secure the ring and then closes the left atrium using 3-0 monofilament polypropylene suture. ANNULOPLASTY. The primary technique used to repair the mitral valve is annuloplasty (Figure 3). Annuloplasty is aimed at restoring the functional size and shape of the fibrous band to which the leaflets attach. When this band is returned to its optimal size and shape, leaflet coaptation is restored. An important concept in annular repair is that much of the dilation occurs at the more flexible posterior portion of the annulus.1 The annular shape is restored using an annular band. A variety of annular bands are available to the cardiac surgeon. The rings range in the degree of flexibility as well as shape. A C-shaped band (Figure 4) allows the anterior portion of the annulus to be preserved and function naturally, whereas a complete ring (Figure 5) supports both the anterior and posterior dimension. The degree of flexibility is important to consider when choosing a band because the band allows the annulus to adapt to changes during the cardiac cycle. When choosing a mitral annuloplasty repair device, all of these variables must be considered in relation to the etiology of the patient’s specific disease pathology. For the patient with left ventricular geometry changes, a three-dimensional shaped band (Figure 6) may contribute to the reversing/remodeling of the rounded shape of the ventricle. SLIDINGPLASTY. In addition to the annu-
loplasty, other repair techniques may be employed based on analysis of the structures of the individual valve. Leaflet defects can be repaired using the slidingplasty technique. These defects, commonly involving the P2 cusp, can be repaired using a quadrangular resection of the cusp and reapproximating the free edges of the remaining P1 and P3 cusps. Undermining the leaflet tissue along the annulus allows the remaining tissue to approximate. The surgeon then reattaches the leaflet edges to the annulus using a 4-0 monofilament, polypropylene interrupted suture. CHORDAL REPAIR, TRANSFER, OR REPLACEMENT. Chordal repairs are accomplished based on the etiology of the patient’s specific
Figure 6 • Threedimensional, shaped mitral valve band implant (Figure courtesy of Edwards Lifesciences, Irvine, Calif)
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SIDEBAR
Systolic Anterior Motion
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ystolic anterior motion (SAM) may occur when
a relatively large posterior mitral valve leaflet [that is coapting] with the anterior mitral valve leaflet closer to its base [causes] both an anterior shift of the coaptation point and an increase in the amount of redundant leaflet tissue in the left ventricular outflow tract.1(p179)
Lee et al2 reported that the incidence of SAM after mitral valve repair is 1% to 2%. More recently, Sternik and Zehr3 reported the incidence of SAM to be 4% to 5%. Often, SAM is noted after the mitral repair is complete and separation from cardiopulmonary bypass (CPB) is initiated. Walkes and Reardon4 assessed patients for SAM via TEE after separation from CPB. Performing an intraoperative transesophageal echocardiogram (TEE) provides a mechanism for diagnosing this phenomenon. Correction of SAM often requires reestablishing CPB and resecting the redundant anterior leaflet tissue in the left ventricular outflow tract. Several preventative surgical techniques have been suggested to prevent the need for an additional episode of CPB. Sternik and Zehn3 advocate tethering the mid segment of the anterior leaflet to prevent the leaflet from flipping into the left ventricular outflow tract. Quigley1 suggests using an elliptical excision of the body of the anterior mitral valve leaflet and simple closure, thus reducing the height of the anterior mitral valve leaflet by approximately 5 cm. If SAM is observed, ionotropic agents and volume loading are instituted to reduce after-load. The TEE is then repeated. If SAM is still observed, CPB is again established and the initial repair is reexamined. 1. Quigley RL. Prevention of systolic anterior motion after repair of severely myxomatous mitral valve with an anterior leaflet valvuloplasty. Ann Thorac Surg. 2005;80:179-182. 2. Lee KS, Stewart WJ, Lever HM, et al. Mechanism of outflow tract obstruction causing failed mitral valve repair. Anterior displacement of leaflet coaptation. Circulation. 1993;88:1124-1129. 3. Sternik L, Zehr KJ. Systolic anterior motion of the mitral valve after mitral valve repair. Tex Heart Inst J. 2005;32:47-49. 4. Walkes JM, Reardon MJ. Status of mitral valve surgery. Curr Opin Cardiol. 2004;19:117-122.
disease pathology. Elongation of the anterior leaflet chord can be repaired by invaginating the excessive chord into the papillary muscle.8 The surgeon uses a 5-0 polypropylene suture to bury the chord into the papillary muscle. Chordal
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transfers can be performed to repair ruptured chords. This can only be employed if suitable chords are available; in which case, the surgeon uses a 4-0 polypropylene suture to secure the chord to the leaflet. Chordal replacement can be used when suitable chords are not available for transfer. A suitable replacement material for chords is ePTFE suture. This replacement technique consists of passing the suture through the papillary muscle and then through the leaflet edge. The surgeon takes special care to determine the length of the chord to ensure accurate length of the replacement material. VALVE REPLACEMENT. Mitral valve repair and preservation of the subvalvular apparatus (ie, chordae and papillary muscles) contributes to the maintenance of left ventricular geometry and function. The decision to replace a valve that is beyond repair is based on the mechanism causing the regurgitation or stenosis. In the case of ischemic mitral valve regurgitation, repair is almost always possible because the underlying issue is the changing geometry of the left ventricle. This changing geometry can be reversed using an appropriately designed annuloplasty ring. Complex mitral valve repair may be a challenge. Replacement may be the only option for severe valvular disease.
WEANING OFF CPB AND CLOSING THE WOUND The perfusionist begins to warm the patient slowly to 37º C (98.6º F). The surgeon places temporary ventricular and atrial pacing wires because electrolyte imbalances, trauma to conductive tissue, and previously undetected conduction disturbances can contribute to postoperative dysrhythmias.4 The scrub person passes the pacing cables off the field to the anesthesia care provider who sets the temporary pacemaker to fully automatic pacing. The surgeon removes the aortic
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SIDEBAR
Protamine Sulfate
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rotamine sulfate, a mixture of simple proteins obtained from the sperm or testes of suitable species of fish, usually salmon, is used to neutralize the anticoagulation effect of heparin. It commonly is used in instances of extracorporeal circulation, such as dialysis or cardiac surgery, in which cardiopulmonary bypass is used. Protamine also is used in some insulin preparations to delay the absorption of insulin. Protamine does have anticoagulant effects when administered in the absence of heparin.1 Protamine is supplied in a 10 mg/mL solution for injection. The standard adult dosage is 1 mg IV for every 100 units of heparin remaining in the patient. Protamine must be administered slowly over a period of 10 minutes because administering it too quickly may result in severe hypotension and anaphylactic reaction. Activated clotting time results should be used to monitor the effect of protamine in neutralizing heparin. Adverse reactions to protamine are an antigen-antibody response that can result in cutaneous symptoms (eg, skin flushing, pruritus) or systemic symptoms (eg, hypotension, bradycardia) and anaphylaxis.2 Precautions related to protamine administration should be taken for patients who have been exposed to protamine in the past through use of protamine-containing insulin or previous heparin neutralization during dialysis or CPB. Caution should be used for patients with a history of fish allergy as they may develop a sensitivity reaction. Men who have had a vasectomy are at increased risk for a protamine reaction. During a vasectomy the normal ejaculatory path is occluded and sperm are absorbed systemically. This systemic reabsorption may stimulate antibody production.3 Patients who have an increased risk for protamine reaction may be treated before initiation of CPB. Loubser 4 demonstrated that activation of the anaphylactic response mediated by complement activation is inhibited by high-dose methylprednisolone pretreatment before initiation of CPB. Diphenhydramine and ranitidine also can be used as pretreatment for patients with increased risk factors for protamine reaction. Health care providers administering protamine must be aware of possible risk factors that could result in a protamine reaction. Protamine should only be administered by health care providers who are trained in resuscitation techniques and the treatment of anaphylactic shock. Health care providers should continually assess the patient for flushing, nausea, vomiting, dyspnea, hypotension, and bradycardia and then promptly treat the patient to avoid potential catastrophic outcomes. 1. DRUGDEX DRUG EVALUATIONS—Protamine. In: MICROMEDEX(R) Healthcare Series [subscription database online]. Greenwood Village, Colo: Thomson MICROMEDEX; 2005. 2. MARTINDALE-The Complete Drug Reference—Protamine. In: MICROMEDEX(R) Healthcare Series [subscription database online]. Greenwood Village, Colo: Thomson MICROMEDEX; 2005. 3. Porsche R, Brenner ZR. Allergy to protamine sulfate. Heart Lung. 1999;28:418-428. 4. Loubser J. Effect of methylprednisolone on complement activation during heparin neutralization. J Cardiovasc Pharmacol. 1997;29:23-27.
cross clamp, and the perfusionist begins to wean the patient off bypass as a cardiologist performs a postoperative TEE to assess the function of the repaired valve, comparing it to the preoperative TEE. The surgeon also uses the TEE to diagnose the presence of systolic anterior motion and to identify air in the left ventricle. When it is confirmed that there is no air in the heart, the surgeon removes the left ventricular catheter and antegrade cardioplegia cannulae. If the surgeon identifies air in the heart, the anesthesia care provider places the patient in a slight Trendelenburg position. The surgeon then manually manipulates the heart to allow the air to
remain in the left ventricle so the air can be removed by the ventricular catheter. After the patient is completely weaned off CPB, the surgeon removes the SVC and IVC cannulae. The surgeon then inserts two mediastinal chest tubes and secures them with 0-silk sutures. The anesthesia care provider slowly administers protamine, at which point the circulating nurse and scrub person begin the sponge, needle, and instrument counts. The surgeon is notified of any discrepancies in the counts. The surgeon removes the aortic cannula, closes the pericardium, and removes the sternal retractor. He or she assesses the sternal edges for bleeding AORN JOURNAL •
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and uses bone wax and electrosurgery as needed to control bleeding. The surgeon then closes the sternum using eight #5 wires, and connects the chest tubes to continuous suction via a threechambered, underwaterseal, pleural drainage system. The surgeon closes the subcutaneous tissue The nurse using 0 and 2-0 monofilainitiates use of ment, polydioxanone suture and closes the skin with 4-0 monofilament, the incentive poliglecaprone suture. The spirometer with circulating nurse, anesthesia care provider, and surgeon transport the patient coughing and directly to the thoracic intensive care unit (ICU). deep breathing
immediately after extubation and helps the patient sit on the side of the bed within six hours of extubation.
POSTOPERATIVE PHASE
At University Hospital, Ann Arbor, Mich, postoperative care is guided by a critical pathway developed for the uncomplicated CBP procedure. The surgical day includes direct admission to the thoracic ICU from the OR. Initial postoperative laboratory tests include a CBC with platelets; an electrolyte (eg, potassium) count; and an arterial blood gas. An ICU nurse ensures that a chest x-ray is performed when the patient is admitted to the ICU. The nurse ensures that the patient regains and maintains normothermia by using a temperatureregulating blanket and warmed IV solutions and obtains the patient’s vital signs, including assessment of pain • every 15 minutes until rewarming is complete (ie, to 37° C [98.6° F]) and then • every four hours until discharged from the ICU, or as needed. The surgical resident extubates the
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patient as soon as possible (ie, usually within four to eight hours) and places the patient on 6 L of oxygen via nasal cannula. The ICU nurse monitors the patient’s mediastinal chest tubes and pleural drainage system for excessive (ie, more than 200 mL/hour) or increasing drainage. The ICU nurse replaces potassium to maintain levels between 4.0 mEq/L and 5.2 mEq/L. He or she administers morphine, the pain medication of choice, as needed and continues IV administration of antibiotics (eg, cefazolin or vancomycin) for 48 hours. The ICU nurse also administers heparin subcutaneously for platelet counts greater than 100,000/mL3. When the patient is extubated, the nurse advances the patient’s diet from clear liquids to full liquids, then to a full liquid, low cholesterol, no-addedsodium diet. The nurse initiates use of the incentive spirometer with coughing and deep breathing immediately after extubation and helps the patient sit on the side of the bed within six hours of extubation. The cardiologist sets the atrioventricular-sequential pacemaker to fully automatic pacing. On the first postoperative day, the surgical resident removes the pulmonary artery catheter and arterial lines after the patient is determined to be hemodynamically stable. The ICU nurse removes the indwelling urinary catheter on the first postoperative day. The nurse weans the patient from morphine to use of oxycodone/acetaminophen as soon as the patient is able to take oral medications and according to the patient’s acceptable pain threshold. The ICU nurse prepares the patient for transfer to the cardiac step-down unit, usually by the first postoperative day. In the cardiac step-down unit, the assigned nurse encourages the patient to ambulate in the halls three times per day. The nurse advances the patient from a full liquid to a regular diet with
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no added sodium and low cholesterol. The sternal dressing remains in place and the nurse reinforces it as needed. The nurse adds one aspirin per day to the patient’s medication regimen. On the second postoperative day, the surgical resident removes the mediastinal chest tubes if drainage is less than 50 mL in eight hours and applies an occlusive dressing over the chest tube sites for 24 hours. A chest x-ray is taken after the chest tubes are removed to ascertain that the patient’s lungs remain reinflated. The surgical resident removes the sternal dressing and the nurse cleans the incision with normal saline, after which the nurse covers the incision only if the wound is draining. The nurse and physical therapist ensure that the patient ambulates four times a day. The nurse adds a stool softener to the patient’s medication regimen and begins to teach the patient and his or her family members about the medication regimen to be followed at home after discharge. On the third postoperative day, the nurse ensures that discharge laboratory tests are performed including a CBC with platelet count. The surgical resident, nurse practitioner, or physician’s assistant removes the pacing wires if the patient’s heart rhythm is stable. The nurse begins teaching the patient and his or her family members about wound care and makes final discharge plans and orders any needed home supplies. The nurse then removes any remaining peripheral IV lines. The nurse discharges the patient on the fourth postoperative day with instructions about medications and wound care. He or she instructs the patient to continue using the incentive spirometer and performing coughing and deep breathing exercises. The nurse ensures that an appointment is made for a one-month follow-up in the cardiac surgery clinic and gives the
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patient instructions on how to contact the surgical resident should any questions arise.
CONCLUSION Treatment of mitral valve disease has evolved from replacement to repair. Improved understanding of the underlying pathology has been an important part of this evolution. A variety of repair techniques used by experienced surgeons provide patients with the best possible outcomes. The next phase in the evolution of mitral valve repair is minimally invasive, robotic-assisted mitral valve repair.9 This technique uses robotic technology along with a right-chest endoscopic approach. Although use of this technique has been reported by other centers in the United States, it currently is not being used for mitral valve repair at the University of Michigan. ❖ Margo Winters, RN, BSN, CNOR, was the adult cardiac surgery education coordinator at University Hospital, University of Michigan Health System, Ann Arbor, Mich, at the time this article was written. Currently, she is a clinical systems trainer for the computerized physician order entry project at the University of Michigan. Pam Obriot, RN, BSN, is a RN first assistant and cardiac surgery education coordinator at University Hospital, University of Michigan Health System, Ann Arbor, Mich.
REFERENCES 1. Ho SY. Anatomy of the mitral valve. Heart. 2002;88(suppl 4):iv5-10. 2. Seifert PC. Cardiac Surgery Perioperative Patient Care. St. Louis: Mosby; 2002. 3. Finkelmeier BA. Cardiothoracic Surgical Nursing. Philadelphia: Lippincott, Williams & Wilkins; 1995:21-22. 4. Thompson JM, McFarland GK, Hirsh JE, et al. Mosby’s Clinical Nursing. St Louis: Mosby; 1986. AORN JOURNAL •
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5. Walkes JM, Reardon MJ. Status of mitral valve surgery. Curr Opin Cardiol. 2004;19: 117-122. 6. Wells FC, Shapiro LM. Mitral Valve Disease. Oxford: Butterworth-Heinemann, Ltd; 1996. 7. Nowicki ER, Weintraub RW, Birkmeyer NJ, et al. Mitral valve repair in northern New
England. Am Heart J. 2003;145:1058-1062. 8. Savage EB, Bolling SF. Atlas of Mitral Valve Repair. Philadelphia: Lippincott, Williams & Wilkins; 2006. 9. Woo YJ, Nacke EA. Robotic minimally invasive mitral valve reconstruction yields less blood product transfusion and shorter length of stay. Surgery. 2006;140:263-267.
Computer System May Improve Weaning From Ventilators
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atients with acute respiratory failure who are on ventilation in the intensive care unit (ICU) have a shorter duration on mechanical ventilation when placed on a computerized system of weaning from the ventilator, according to an Oct 16, 2006, news release from The American Thoracic Society. Compared to typical physician-controlled management of the weaning process, the computer-driven system resulted in a reduction in patients’ time on mechanical ventilation from 12 days to 7.5 days and a reduction in length of ICU stays from 15.5 days to 12 days. The computerized system introduces an automatic, gradual reduction in pressure support; initiates automatic spontaneous breathing trials; and generates an incentive message when the patient’s
spontaneous breathing trial is successful. Additionally, patients who were weaned using this computerized system had a 30% reduction in total number of ventilator-related complications, including • reintubation, • self-removal from ventilator assistance, • need for noninvasive ventilation, • mechanical ventilation longer than 21 days, and • tracheotomy. Computer-Driven System Reduces Patient Mechanical Ventilation Time Significantly [news release]. New York: American Thoracic Society; October 16, 2006. Available at: http://www.eurekalert.org/pub_releases/2006-10 /ats-csr100506.php. Accessed October 27, 2006.
Poor Have Higher Risk of Death in Some Neighborhoods
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esearchers investigating income and education data in comparison to the socioeconomic status of a person’s neighborhood determined that people of low socioeconomic status living in affluent neighborhoods have an increased risk of death, according to an Oct 31, 2006, news release from the Stanford University School of Medicine, Stanford, Calif. This trend was discovered after researchers analyzed data from a previous study of 8,200 men and women from 82 neighborhoods in several California towns for a 17year period. The researchers determined that 19 out of every 1,000 women of low socioeconomic status who lived in wealthier neighborhoods had died after 17 years, compared to 11 out of every 1,000 women who lived in poorer neighborhoods. Although less dramatic, a similar trend was found in men. The differences in death rates became more pronounced over time, and were not found to be related to age; cause of death; or risk factors such
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as obesity, hypertension, or smoking. It is possible that the higher cost of living in wealthy neighborhoods reduces the amount of disposable income that people of low socioeconomic status have to spend on essential goods and services such as health care and healthy food. A poor person in a wealthier neighborhood might not have access to free social services made available in low-income neighborhoods. It also is possible that people of lower socioeconomic status, in comparing themselves with their neighbors, fare worse in this socioeconomic setting for psychological and social reasons. Poor People in Well-To-Do Neighborhoods Face Higher Death Rates, Stanford Study Finds [news release]. Stanford, Calif: Stanford University School of Medicine; October 31, 2006. Available at: http://mednews.stanford .edu/releases/2006/october/neighborhood.html. Accessed November 6, 2006.