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Transpharyngeal Imaging With Transesophageal Echocardiography as an Adjunct for Optimizing Retrograde Cerebral Perfusion
Transpharyngeal Imaging With Transesophageal Echocardiography as an Adjunct for Optimizing Retrograde Cerebral Perfusion Niranjan Dilip Waje, MD, Madan Mohan Maddali, MD, and Kamalakannan Nadarajan, MD
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EUROLOGIC PROTECTION DURING aortic arch surgery is challenging. Hypothermic circulatory arrest, retrograde cerebral perfusion, and antegrade cerebral perfusion are a few strategies that have evolved to minimize the neurologic injury that occurs from hypoperfusion.1 Monitoring adequacy of cerebral perfusion is of paramount importance despite the strategy that is adopted. Retrograde cerebral perfusion is an established technique in patients undergoing aortic arch surgery with atheromatous cervical branches.2 This case report highlights the clinical adoption of transpharyngeal ultrasonography as a surrogate marker for assessing adequacy of retrograde cerebral perfusion in a patient who underwent successful surgery for acute type-A aortic dissection. Approval of this study was obtained from the Institutional Medical Ethics and Scientific Research Committee (MESRC number 73/2016), and written consent to publish data was obtained from the patient. CASE PRESENTATION
A 63-year-old man (weight 76 kg, height 168 cm, body surface area 1.9 m2) with severe chest pain was diagnosed using transthoracic echocardiography and computed tomography as experiencing an acute type-A aortic dissection with severe aortic regurgitation. A coronary angiogram demonstrated normal coronary arteries. He was transferred to the operating room for an emergency surgical repair. Before induction of anesthesia, bilateral near-infrared spectroscopy sensors for cerebral oximetry (INVOS 5100C; Covidien, Minneapolis, MN) were placed on the patient’s forehead. After preoxygenation, using standard American Society of Anesthesiologists’ recommended monitoring modalities, general anesthesia was administered with intravenous fentanyl (2 μg/kg), midazolam (1 mg), etomidate (0.5 mg/kg), and rocuronium (0.6 mg/kg). Anesthesia was maintained with isoflurane (1 minimum alveolar concentration) and weightadjusted infusions of 1% propofol, fentanyl, and rocuronium. Invasive hemodynamic monitoring included bilateral radial artery cannulation and left axillary vein and right jugular bulb catheterization under ultrasound guidance. Bilateral radial artery cannulation was performed to monitor and ensure the adequacy of perfusion through all the aortic arch vessels during femoral arterial cardiopulmonary bypass. In addition, right radial arterial pressures could be considered as surrogate markers for innominate artery patency both before and after placement of the aortic cross-clamp. In cases of innominate artery repair or reimplantation, the left radial artery pressure would be used to assess the antegrade cerebral perfusion through the left common carotid artery. Simultaneous monitoring of retrograde cerebral perfusion pressure was performed through left axillary vein cannulation with a 9-Fr IntroFlex Percutaneous Sheath Introducer (Edward Lifesciences, Irvine, CA) and right jugular venous bulb cannulation. Left axillary vein pressure was monitored to confirm perfusion of the left jugular vein and to preclude inappropriate positioning of the retrograde cerebral perfusion cannula. A pulmonary artery catheter could be inserted through the left axillary vein when
the need arose and at the end of surgery for hemodynamic management if advanced monitoring was deemed necessary. The anesthesia team included 2 experienced anesthesiologists; 1 of the anesthesiologists, who was experienced in intraoperative transesophageal echocardiography, performed echocardiography examinations, and the second anesthesiologist managed the hemodynamic parameters. Intraoperative transesophageal echocardiography was used to confirm the preoperative transthoracic echocardiography findings. The ascending aorta was dilated (aortic annulus 27 mm, sinotubular junction 45 mm, ascending aorta 51 mm, aortic arch 38 mm). A dissecting flap was noted just above the aortic valve. The aortic regurgitation was severe (pressure half-time 245 milliseconds), with diastolic flow reversal in the descending aorta. The short-axis view of the carotid arteries on transpharyngeal imaging showed the aortic arch vessels to be normal and perfused through the true lumen. After a median sternotomy and whole-body heparinization, cardiopulmonary bypass was established through femoral arterial, right atrial, and inferior caval venous cannulation (with a clamped shunt line from the arterial to the superior vena caval cannula for retrograde cerebral perfusion). Systemic cooling was initiated, and the ascending aorta was cross-clamped proximal to the origin of the innominate artery while the right radial artery pressure waveform was monitored. With the patient’s head in neutral position, the transesophageal echocardiography probe was rotated anticlockwise once the pulmonary artery with the pulmonary valve was visualized in the upper esophageal short-axis view. The longitudinal cervical course of the medially located left common carotid artery and anterolaterally located left internal jugular vein was followed by additional retraction of the probe into the hypopharynx to an approximate depth of 8-to-10 cm. Clockwise rotation of the probe (plane 901 to 1001) at the same level helped with examination of the right cerebral vessels. The bilateral carotid arteries and the jugular veins were visualized alternately along their cervical course, and the blood flow pattern was recorded (Fig 1). The left subclavian artery was identified using pulsed-wave Doppler echocardiography, which demonstrated systolic antegrade flow velocity with short early diastolic reversal and no antegrade diastolic flow velocity. The common carotid arteries were recognized by a higher systolic
From the Department of Cardiac Anesthesia, National Heart Center, Royal Hospital, Muscat, Sultanate of Oman. Address reprint requests to Madan Mohan Maddali, MD, National Heart Center, Royal Hospital, P.B. No 1331, PC 111, Seeb, Muscat, Sultanate of Oman. E-mail: [email protected] © 2016 Elsevier Inc. All rights reserved. 1053-0770/2602-0033$36.00/0 http://dx.doi.org/10.1053/j.jvca.2016.07.033 Key Words: aortic diseases/surgery, echocardiography, Doppler, color/methods, echocardiography, transesophageal/methods, jugular veins/ultrasonography, carotid artery, common/ultrasonography, pharynx
Journal of Cardiothoracic and Vascular Anesthesia, Vol ], No ] (Month), 2016: pp ]]]–]]]
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and lower diastolic antegrade flow velocity. A normal biphasic flow pattern was seen in both carotid arteries with absence of a false lumen, ruling out extension of aortic dissection into the carotid vessels. Continuous antegrade flow with equal velocities (about 40 cm/sec) in both carotid arteries reassured the authors that the femoral arterial blood flow after initiation of cardiopulmonary bypass was indeed through the true lumen of the aorta (Fig 2). Myocardial protection was achieved with both retrograde cardioplegia and direct antegrade coronary ostial cardioplegia. The aortic valve and ascending aorta were replaced by a 25/28mm valved conduit (Medtronic Open Pivot; Medtronic, Minneapolis, MN). The distal anastomosis was performed with the patient under deep hypothermic circulatory arrest (181C) and retrograde cerebral perfusion that was achieved after repositioning the right atrial cannula into the superior vena cava. Additional cerebral protection maneuvers, such as topical cooling of the head with ice packs and administration of thiopental (10 mg/kg) and methylprednisolone (30 mg/kg), were used per institutional protocol. Once retrograde cerebral perfusion was initiated, flow reversal in the left jugular vein could not be detected (Fig 3). The reason for this was that at the time of initiation of retrograde cerebral perfusion, the superior vena cava cannula
WAJE ET AL
had been advanced inadvertently by the surgeon beyond the innominate-superior vena caval junction, resulting in selective right jugular vein perfusion, and this malposition of the cannula was recognized immediately. Antegrade flow (jugular flow reversal) was detected in only the right internal jugular vein, with no flow seen in the left internal jugular vein. This was recognized early with continual transpharyngeal imaging of bilateral jugular flow. Withdrawal of the superior vena caval cannula toward the right atrium restored flow into the left jugular vein, and reversal of blood flow was demonstrated in both the carotid arteries and the jugular veins using transpharyngeal imaging (Fig 4). Deep hypothermic circulatory arrest was initiated at jugular bulb saturations of 97%. The regional hemoglobin oxygen saturation (rSO2) values as monitored by near-infrared spectroscopy were in the range of 62% to 65% bilaterally before commencement of the procedure. The rSO2 values were above 90% initially and stabilized above 70% for the duration of retrograde cerebral perfusion. The flow reversal velocities in the cerebral vessels were monitored, which were about 20 cm/ sec on average, throughout the duration of retrograde cerebral perfusion. Retrograde cerebral perfusion pressure was measured using the pressure transduction of the cannula in the right jugular bulb and the sheath in the left axillary vein. Higher
Fig 1. Transpharyngeal images of the baseline blood flow pattern in the bilateral carotid arteries and internal jugular veins. LCCA, left common carotid artery; RCCA, right common carotid artery; LIJV, left internal jugular vein; RIJV, right internal jugular vein.
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TRANSPHARYNGEAL ULTRASONOGRAPHY, EXTENDED USE
Fig 2. Transpharyngeal images of the blood flow patterns in both carotid arteries after institution of femoral-right atrial cardiopulmonary bypass. The flow in LCCA was interrogated by placing the pulse wave Doppler cursor towards the heart. LCCA, left common carotid artery; RCCA, right common carotid artery.
retrograde cerebral perfusion pressures of about 30 mmHg were accepted initially until a reversal of blood flow in both carotid arteries was observed using transpharyngeal ultrasonography. Subsequently, the pressure was reduced to acceptable levels of below 25 mmHg, ensuring continuation of reversal of flow in the carotid arteries with velocities of about 20 cm/sec. The transpharyngeal ultrasonography–guided flow rates with velocities of about 20 cm/sec in the cerebral vessels during retrograde cerebral perfusion ensured that the rSO2 values demonstrated on near-infrared spectroscopy did not decrease by more than 70% of the baseline. The bilateral rSO2 values were in close approximation to each other. These parameters helped in the determination of the cerebral perfusion pressure. The surgical procedure was completed uneventfully using cardiopulmonary bypass (total cardiopulmonary bypass time 201 minutes, aortic cross-clamp time 87 minutes) and deep hypothermic circulatory arrest with continuous retrograde cerebral perfusion (42 minutes). The patient was separated from cardiopulmonary bypass easily and began receiving inotropic infusions (milrinone, 0.5 mg/kg/min, norepinephrine, 0.05 mg/ kg/min) and underwent atrioventricular sequential pacing. He was admitted to postcardiac intensive care for stabilization of hemodynamic and ventilatory parameters.
Fig. 3. Transpharyngeal image of the left internal jugular vein (LIJV) showing no blood flow due to malposition of the retrograde cerebral perfusion cannula.
After 22 hours of mechanical ventilation, tracheal extubation was performed successfully and the patient had no transient or permanent neurologic deficits. The patient was discharged home 9 days after the surgery. A detailed neurologic examination before discharge did not reveal any cognitive or functional derangement. DISCUSSION
The role of transpharyngeal ultrasonography in optimizing retrograde cerebral perfusion in a patient who underwent successful surgery for acute type-A aortic dissection is described. The patient experienced no neurologic sequelae. The major issue during retrograde cerebral perfusion is that only a small proportion of the retrograde flow is delivered to the brain and in a too-uneven pattern.2 Monitoring the jugular vein pressure alone may not be a reliable indicator for assessing the adequacy of retrograde cerebral perfusion. This is because of the possibility of significant shunting of blood flow between the internal and external jugular veins and runoff of the delivered blood via the azygos-inferior vena caval collaterals and the cerebral sinuses.1,2 The inferior vena caval drainage status also is a determinant for the amount of blood flow actually reaching the brain, making jugular pressure alone an unreliable marker for adequacy of retrograde cerebral perfusion.2 Transcutaneous Doppler ultrasound of the carotid arteries in conjunction with cerebral oximetry with near-infrared spectroscopy, bilateral radial artery monitoring, and transesophageal echocardiography have been suggested to be of great importance to quantify carotid artery flow velocity and monitor intraoperative cerebral malperfusion in all aortic surgical cases, particularly when the femoral artery is used for cardiopulmonary bypass.3 During repairs of acute type-A aortic dissection with retrograde cerebral perfusion, identification of cerebral malperfusion using M-mode transcranial Doppler monitoring leads to modification of the technique, resulting in improved neurologic outcomes.4 Transcranial Doppler sonography was found to be useful for providing real-time visualization of the state of cerebral perfusion over the circle of Willis and helped in optimizing perfusion for both hemispheres during an aortic dissection repair under moderate hypothermic circulatory arrest with antegrade selective cerebral perfusion.5 Transcranial color Doppler ultrasonography was found to be useful in the early
4
WAJE ET AL
Fig. 4. Transpharyngeal images showing flow reversal in all major vessels after institution of retrograde cerebral perfusion and readjustment of the right atrial cannula into the superior vena cava. The flow in the left internal jugular vein was examined by placing the pulse-wave Doppler cursor toward the heart. LCCA, left common carotid artery; RCCA, right common carotid artery; LIJV, left internal jugular vein; RIJV, right internal jugular vein.
detection of perfusion abnormalities and to help optimize antegrade and retrograde cerebral perfusion rates during aortic arch surgery.6 A limitation of transcranial Doppler monitoring, especially in elderly patients, could be intracranial atherosclerosis producing ultrasonic opacities within the cranial temporal region, thereby precluding its utility as a monitoring modality in this group of patients.7 The authors of this study explored the possibility of transpharyngeal ultrasonography as a semi-invasive monitoring modality to guide optimal delivery of retrograde cerebral blood flow. Transpharyngeal ultrasonography with a transesophageal echocardiography probe to help guide the internal jugular vein cannulation was described earlier.8 Augoustides,9 taking a futuristic view, predicted the role transpharyngeal vascular real-time imaging of the carotid artery and the internal jugular vein could play in the surgical management of adult aortic arch repairs. Detection of carotid malperfusion and identification of venous abnormalities that might alter delivery of the retrograde cerebral perfusion using transpharyngeal imaging were some of the attributes that were suggested.9 In the patient described here, malposition of the cannula during cerebral reperfusion was detected early using transpharyngeal ultrasonography, and corrective measures were taken.
During retrograde cerebral perfusion the suggested flow rates are about 300-to-500 mL/min with central venous pressures of 25 mmHg.1 Higher initial flows with higher opening pressures (elevated perfusion pressures) probably are required to optimize oxygen substrate and blood delivery to the brain. Higher opening pressures might be needed to open competent venous valves and to overcome the increase in venous resistance of the cerebral vasculature as a result of the conversion from antegrade to retrograde perfusion.4 In this patient, the initial pressures were high (30 mmHg) for bilateral reversal of flow (with velocities of about 20 cm/sec) in the carotid arteries to be realized. Subsequently, the cerebral perfusion pressure was reduced to the recommended levels, with transpharyngeal ultrasonography demonstrating flow reversal in both carotid arteries. Transpharyngeal imaging–aided cerebral perfusion during deep hypothermic circulatory arrest could be a valuable adjunct to cerebral oximetry. Reversal of flow velocities of about 20 cm/sec in both carotid arteries during retrograde cerebral perfusion correlated with nearly equal bilateral rSO2 values. Higher retrograde cerebral perfusion pressures might be needed initially to increase retrograde cerebral blood flow and ensure greater availability of cerebral substrate perfusion. However, high superior vena caval pressures of 30 mmHg
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could cause cerebral edema and a higher intracranial pressure.2 Therefore, as soon as flow reversal (with velocities of about 20 cm/sec) is detected bilaterally in the cerebral vessels, the retrograde perfusion pressure should be reduced to maintenance level. It is important that velocities of reversed flows in both carotid arteries and bilateral near-infrared spectroscopy values are nearly equal at all times. Inadequate retrograde cerebral perfusion flow and excessive flows causing cerebral edema could affect near-infrared spectroscopy values adversely. Near-infrared spectroscopy values alone probably would be insufficient to help guide titration of retrograde cerebral perfusion pressures. Bilateral reversal of blood flow in the carotid arteries as demonstrated by transcranial Doppler or transpharyngeal ultrasonography would be a valuable adjunct to cerebral oximetry during retrograde cerebral perfusion. Transpharyngeal ultrasonography has the added advantage of its use in examining jugular blood flows and helping in the early identification of cannula malposition. Monitoring flow velocities and blood flow directions in the cerebral vessels using transpharyngeal imaging in patients undergoing aortic arch surgery would take place at the following time points: (1) before instituting cardiopulmonary bypass, (2) soon after initiating cardiopulmonary bypass, and (3) continually thereafter during the entire duration of retrograde cerebral perfusion. Transpharyngeal ultrasonography should be performed by a dedicated professional with experience in intraoperative transesophageal echocardiography while a second anesthesiologist
manages the hemodynamic parameters. As the probe is retracted into the hypopharynx, care must be taken that it is not dislodged from the oral cavity, and trauma to oral structures should be avoided. It is possible that clear images might not be acquired in all patients because the intervening trachea is filled with air. A lower color scale (about 20 cm/sec) might be needed for optimal visualization of the neck vasculature using color Doppler examination. Lastly, this technique should be used in conjunction with cerebral oximetry because there is a dearth of evidence that transpharyngeal ultrasound monitoring of the carotid and/or jugular venous flow actually correlates with cerebral blood flow under the conditions of either lowflow antegrade or retrograde selective cerebral perfusion. An extended use of the transesophageal echocardiography probe for transpharyngeal monitoring of the bilateral carotid arteries at all stages of aortic arch repair is proposed. It would help in the detection of reversal of flow during retrograde cerebral perfusion. Close-proximity transpharyngeal ultrasonic measurement of cerebral blood flow or velocity would help in the detection of clinically significant asymmetry that might suddenly develop but go undetected and result in preventable neurologic injury. ACKNOWLEDGMENT
The authors sincerely thank Dr. Roger Green, FRCS, for his valuable guidance in the preparation of this manuscript.
REFERENCES 1. Seco M, Edelman JJ, Van Boxtel B, et al: Neurologic injury and protection in adult cardiac and aortic surgery. J Cardiothorac Vasc Anesth 29:185-195, 2015 2. Ueda Y: A reappraisal of retrograde cerebral perfusion. Ann Cardiothorac Surg 2:316-325, 2013 3. Pulido JN, Pallohusky BS, Park SJ, et al: Transcutaneous ultrasound measurements of carotid flow to monitor for cerebral malperfusion during type-A aortic dissection repair. J Cardiothorac Vasc Anesth 27:728-730, 2013 4. Estrera AL, Garami Z, Miller CC 3rd, et al: Determination of cerebral blood flow dynamics during retrograde cerebral perfusion using power M-mode transcranial Doppler. Ann Thorac Surg 76:704-709, 2003 5. Ghazy T, Darwisch A, Schmidt T, et al: Transcranial Doppler sonography for optimization of cerebral perfusion in aortic arch operation. Ann Thorac Surg 101:e15-e16, 2016
6. Catena E, Tasca G, Fracasso G, et al: Usefulness of transcranial color Doppler ultrasonography in aortic arch surgery. J Cardiovasc Med (Hagerstown) 14:597-602, 2013 7. Suri MF, Georgiadis AL, Tariq N, et al: Estimated prevalence of acoustic cranial windows and intracranial stenosis in the US elderly population: Ultrasound screening in adults for intracranial disease study. Neuroepidemiology 37:64-71, 2011 8. Bevilacqua S, Romagnoli S, Ciappi F, et al: Transpharyngeal ultrasonography for cannulation of the internal jugular vein. Anesthesiology 102:873-874, 2005 9. Augoustides JG: Transpharyngeal imaging of the carotid artery and internal jugular vein: Possible roles in cerebral perfusion management during adult aortic arch repair. J Cardiothorac Vasc Anesth 21: 318-319, 2007
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EUROLOGIC PROTECTION DURING aortic arch surgery is challenging. Hypothermic circulatory arrest, retrograde cerebral perfusion, and antegrade cerebral perfusion are a few strategies that have evolved to minimize the neurologic injury that occurs from hypoperfusion.1 Monitoring adequacy of cerebral perfusion is of paramount importance despite the strategy that is adopted. Retrograde cerebral perfusion is an established technique in patients undergoing aortic arch surgery with atheromatous cervical branches.2 This case report highlights the clinical adoption of transpharyngeal ultrasonography as a surrogate marker for assessing adequacy of retrograde cerebral perfusion in a patient who underwent successful surgery for acute type-A aortic dissection. Approval of this study was obtained from the Institutional Medical Ethics and Scientific Research Committee (MESRC number 73/2016), and written consent to publish data was obtained from the patient. CASE PRESENTATION
A 63-year-old man (weight 76 kg, height 168 cm, body surface area 1.9 m2) with severe chest pain was diagnosed using transthoracic echocardiography and computed tomography as experiencing an acute type-A aortic dissection with severe aortic regurgitation. A coronary angiogram demonstrated normal coronary arteries. He was transferred to the operating room for an emergency surgical repair. Before induction of anesthesia, bilateral near-infrared spectroscopy sensors for cerebral oximetry (INVOS 5100C; Covidien, Minneapolis, MN) were placed on the patient’s forehead. After preoxygenation, using standard American Society of Anesthesiologists’ recommended monitoring modalities, general anesthesia was administered with intravenous fentanyl (2 μg/kg), midazolam (1 mg), etomidate (0.5 mg/kg), and rocuronium (0.6 mg/kg). Anesthesia was maintained with isoflurane (1 minimum alveolar concentration) and weightadjusted infusions of 1% propofol, fentanyl, and rocuronium. Invasive hemodynamic monitoring included bilateral radial artery cannulation and left axillary vein and right jugular bulb catheterization under ultrasound guidance. Bilateral radial artery cannulation was performed to monitor and ensure the adequacy of perfusion through all the aortic arch vessels during femoral arterial cardiopulmonary bypass. In addition, right radial arterial pressures could be considered as surrogate markers for innominate artery patency both before and after placement of the aortic cross-clamp. In cases of innominate artery repair or reimplantation, the left radial artery pressure would be used to assess the antegrade cerebral perfusion through the left common carotid artery. Simultaneous monitoring of retrograde cerebral perfusion pressure was performed through left axillary vein cannulation with a 9-Fr IntroFlex Percutaneous Sheath Introducer (Edward Lifesciences, Irvine, CA) and right jugular venous bulb cannulation. Left axillary vein pressure was monitored to confirm perfusion of the left jugular vein and to preclude inappropriate positioning of the retrograde cerebral perfusion cannula. A pulmonary artery catheter could be inserted through the left axillary vein when
the need arose and at the end of surgery for hemodynamic management if advanced monitoring was deemed necessary. The anesthesia team included 2 experienced anesthesiologists; 1 of the anesthesiologists, who was experienced in intraoperative transesophageal echocardiography, performed echocardiography examinations, and the second anesthesiologist managed the hemodynamic parameters. Intraoperative transesophageal echocardiography was used to confirm the preoperative transthoracic echocardiography findings. The ascending aorta was dilated (aortic annulus 27 mm, sinotubular junction 45 mm, ascending aorta 51 mm, aortic arch 38 mm). A dissecting flap was noted just above the aortic valve. The aortic regurgitation was severe (pressure half-time 245 milliseconds), with diastolic flow reversal in the descending aorta. The short-axis view of the carotid arteries on transpharyngeal imaging showed the aortic arch vessels to be normal and perfused through the true lumen. After a median sternotomy and whole-body heparinization, cardiopulmonary bypass was established through femoral arterial, right atrial, and inferior caval venous cannulation (with a clamped shunt line from the arterial to the superior vena caval cannula for retrograde cerebral perfusion). Systemic cooling was initiated, and the ascending aorta was cross-clamped proximal to the origin of the innominate artery while the right radial artery pressure waveform was monitored. With the patient’s head in neutral position, the transesophageal echocardiography probe was rotated anticlockwise once the pulmonary artery with the pulmonary valve was visualized in the upper esophageal short-axis view. The longitudinal cervical course of the medially located left common carotid artery and anterolaterally located left internal jugular vein was followed by additional retraction of the probe into the hypopharynx to an approximate depth of 8-to-10 cm. Clockwise rotation of the probe (plane 901 to 1001) at the same level helped with examination of the right cerebral vessels. The bilateral carotid arteries and the jugular veins were visualized alternately along their cervical course, and the blood flow pattern was recorded (Fig 1). The left subclavian artery was identified using pulsed-wave Doppler echocardiography, which demonstrated systolic antegrade flow velocity with short early diastolic reversal and no antegrade diastolic flow velocity. The common carotid arteries were recognized by a higher systolic
From the Department of Cardiac Anesthesia, National Heart Center, Royal Hospital, Muscat, Sultanate of Oman. Address reprint requests to Madan Mohan Maddali, MD, National Heart Center, Royal Hospital, P.B. No 1331, PC 111, Seeb, Muscat, Sultanate of Oman. E-mail: [email protected] © 2016 Elsevier Inc. All rights reserved. 1053-0770/2602-0033$36.00/0 http://dx.doi.org/10.1053/j.jvca.2016.07.033 Key Words: aortic diseases/surgery, echocardiography, Doppler, color/methods, echocardiography, transesophageal/methods, jugular veins/ultrasonography, carotid artery, common/ultrasonography, pharynx
Journal of Cardiothoracic and Vascular Anesthesia, Vol ], No ] (Month), 2016: pp ]]]–]]]
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and lower diastolic antegrade flow velocity. A normal biphasic flow pattern was seen in both carotid arteries with absence of a false lumen, ruling out extension of aortic dissection into the carotid vessels. Continuous antegrade flow with equal velocities (about 40 cm/sec) in both carotid arteries reassured the authors that the femoral arterial blood flow after initiation of cardiopulmonary bypass was indeed through the true lumen of the aorta (Fig 2). Myocardial protection was achieved with both retrograde cardioplegia and direct antegrade coronary ostial cardioplegia. The aortic valve and ascending aorta were replaced by a 25/28mm valved conduit (Medtronic Open Pivot; Medtronic, Minneapolis, MN). The distal anastomosis was performed with the patient under deep hypothermic circulatory arrest (181C) and retrograde cerebral perfusion that was achieved after repositioning the right atrial cannula into the superior vena cava. Additional cerebral protection maneuvers, such as topical cooling of the head with ice packs and administration of thiopental (10 mg/kg) and methylprednisolone (30 mg/kg), were used per institutional protocol. Once retrograde cerebral perfusion was initiated, flow reversal in the left jugular vein could not be detected (Fig 3). The reason for this was that at the time of initiation of retrograde cerebral perfusion, the superior vena cava cannula
WAJE ET AL
had been advanced inadvertently by the surgeon beyond the innominate-superior vena caval junction, resulting in selective right jugular vein perfusion, and this malposition of the cannula was recognized immediately. Antegrade flow (jugular flow reversal) was detected in only the right internal jugular vein, with no flow seen in the left internal jugular vein. This was recognized early with continual transpharyngeal imaging of bilateral jugular flow. Withdrawal of the superior vena caval cannula toward the right atrium restored flow into the left jugular vein, and reversal of blood flow was demonstrated in both the carotid arteries and the jugular veins using transpharyngeal imaging (Fig 4). Deep hypothermic circulatory arrest was initiated at jugular bulb saturations of 97%. The regional hemoglobin oxygen saturation (rSO2) values as monitored by near-infrared spectroscopy were in the range of 62% to 65% bilaterally before commencement of the procedure. The rSO2 values were above 90% initially and stabilized above 70% for the duration of retrograde cerebral perfusion. The flow reversal velocities in the cerebral vessels were monitored, which were about 20 cm/ sec on average, throughout the duration of retrograde cerebral perfusion. Retrograde cerebral perfusion pressure was measured using the pressure transduction of the cannula in the right jugular bulb and the sheath in the left axillary vein. Higher
Fig 1. Transpharyngeal images of the baseline blood flow pattern in the bilateral carotid arteries and internal jugular veins. LCCA, left common carotid artery; RCCA, right common carotid artery; LIJV, left internal jugular vein; RIJV, right internal jugular vein.
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TRANSPHARYNGEAL ULTRASONOGRAPHY, EXTENDED USE
Fig 2. Transpharyngeal images of the blood flow patterns in both carotid arteries after institution of femoral-right atrial cardiopulmonary bypass. The flow in LCCA was interrogated by placing the pulse wave Doppler cursor towards the heart. LCCA, left common carotid artery; RCCA, right common carotid artery.
retrograde cerebral perfusion pressures of about 30 mmHg were accepted initially until a reversal of blood flow in both carotid arteries was observed using transpharyngeal ultrasonography. Subsequently, the pressure was reduced to acceptable levels of below 25 mmHg, ensuring continuation of reversal of flow in the carotid arteries with velocities of about 20 cm/sec. The transpharyngeal ultrasonography–guided flow rates with velocities of about 20 cm/sec in the cerebral vessels during retrograde cerebral perfusion ensured that the rSO2 values demonstrated on near-infrared spectroscopy did not decrease by more than 70% of the baseline. The bilateral rSO2 values were in close approximation to each other. These parameters helped in the determination of the cerebral perfusion pressure. The surgical procedure was completed uneventfully using cardiopulmonary bypass (total cardiopulmonary bypass time 201 minutes, aortic cross-clamp time 87 minutes) and deep hypothermic circulatory arrest with continuous retrograde cerebral perfusion (42 minutes). The patient was separated from cardiopulmonary bypass easily and began receiving inotropic infusions (milrinone, 0.5 mg/kg/min, norepinephrine, 0.05 mg/ kg/min) and underwent atrioventricular sequential pacing. He was admitted to postcardiac intensive care for stabilization of hemodynamic and ventilatory parameters.
Fig. 3. Transpharyngeal image of the left internal jugular vein (LIJV) showing no blood flow due to malposition of the retrograde cerebral perfusion cannula.
After 22 hours of mechanical ventilation, tracheal extubation was performed successfully and the patient had no transient or permanent neurologic deficits. The patient was discharged home 9 days after the surgery. A detailed neurologic examination before discharge did not reveal any cognitive or functional derangement. DISCUSSION
The role of transpharyngeal ultrasonography in optimizing retrograde cerebral perfusion in a patient who underwent successful surgery for acute type-A aortic dissection is described. The patient experienced no neurologic sequelae. The major issue during retrograde cerebral perfusion is that only a small proportion of the retrograde flow is delivered to the brain and in a too-uneven pattern.2 Monitoring the jugular vein pressure alone may not be a reliable indicator for assessing the adequacy of retrograde cerebral perfusion. This is because of the possibility of significant shunting of blood flow between the internal and external jugular veins and runoff of the delivered blood via the azygos-inferior vena caval collaterals and the cerebral sinuses.1,2 The inferior vena caval drainage status also is a determinant for the amount of blood flow actually reaching the brain, making jugular pressure alone an unreliable marker for adequacy of retrograde cerebral perfusion.2 Transcutaneous Doppler ultrasound of the carotid arteries in conjunction with cerebral oximetry with near-infrared spectroscopy, bilateral radial artery monitoring, and transesophageal echocardiography have been suggested to be of great importance to quantify carotid artery flow velocity and monitor intraoperative cerebral malperfusion in all aortic surgical cases, particularly when the femoral artery is used for cardiopulmonary bypass.3 During repairs of acute type-A aortic dissection with retrograde cerebral perfusion, identification of cerebral malperfusion using M-mode transcranial Doppler monitoring leads to modification of the technique, resulting in improved neurologic outcomes.4 Transcranial Doppler sonography was found to be useful for providing real-time visualization of the state of cerebral perfusion over the circle of Willis and helped in optimizing perfusion for both hemispheres during an aortic dissection repair under moderate hypothermic circulatory arrest with antegrade selective cerebral perfusion.5 Transcranial color Doppler ultrasonography was found to be useful in the early
4
WAJE ET AL
Fig. 4. Transpharyngeal images showing flow reversal in all major vessels after institution of retrograde cerebral perfusion and readjustment of the right atrial cannula into the superior vena cava. The flow in the left internal jugular vein was examined by placing the pulse-wave Doppler cursor toward the heart. LCCA, left common carotid artery; RCCA, right common carotid artery; LIJV, left internal jugular vein; RIJV, right internal jugular vein.
detection of perfusion abnormalities and to help optimize antegrade and retrograde cerebral perfusion rates during aortic arch surgery.6 A limitation of transcranial Doppler monitoring, especially in elderly patients, could be intracranial atherosclerosis producing ultrasonic opacities within the cranial temporal region, thereby precluding its utility as a monitoring modality in this group of patients.7 The authors of this study explored the possibility of transpharyngeal ultrasonography as a semi-invasive monitoring modality to guide optimal delivery of retrograde cerebral blood flow. Transpharyngeal ultrasonography with a transesophageal echocardiography probe to help guide the internal jugular vein cannulation was described earlier.8 Augoustides,9 taking a futuristic view, predicted the role transpharyngeal vascular real-time imaging of the carotid artery and the internal jugular vein could play in the surgical management of adult aortic arch repairs. Detection of carotid malperfusion and identification of venous abnormalities that might alter delivery of the retrograde cerebral perfusion using transpharyngeal imaging were some of the attributes that were suggested.9 In the patient described here, malposition of the cannula during cerebral reperfusion was detected early using transpharyngeal ultrasonography, and corrective measures were taken.
During retrograde cerebral perfusion the suggested flow rates are about 300-to-500 mL/min with central venous pressures of 25 mmHg.1 Higher initial flows with higher opening pressures (elevated perfusion pressures) probably are required to optimize oxygen substrate and blood delivery to the brain. Higher opening pressures might be needed to open competent venous valves and to overcome the increase in venous resistance of the cerebral vasculature as a result of the conversion from antegrade to retrograde perfusion.4 In this patient, the initial pressures were high (30 mmHg) for bilateral reversal of flow (with velocities of about 20 cm/sec) in the carotid arteries to be realized. Subsequently, the cerebral perfusion pressure was reduced to the recommended levels, with transpharyngeal ultrasonography demonstrating flow reversal in both carotid arteries. Transpharyngeal imaging–aided cerebral perfusion during deep hypothermic circulatory arrest could be a valuable adjunct to cerebral oximetry. Reversal of flow velocities of about 20 cm/sec in both carotid arteries during retrograde cerebral perfusion correlated with nearly equal bilateral rSO2 values. Higher retrograde cerebral perfusion pressures might be needed initially to increase retrograde cerebral blood flow and ensure greater availability of cerebral substrate perfusion. However, high superior vena caval pressures of 30 mmHg
5
TRANSPHARYNGEAL ULTRASONOGRAPHY, EXTENDED USE
could cause cerebral edema and a higher intracranial pressure.2 Therefore, as soon as flow reversal (with velocities of about 20 cm/sec) is detected bilaterally in the cerebral vessels, the retrograde perfusion pressure should be reduced to maintenance level. It is important that velocities of reversed flows in both carotid arteries and bilateral near-infrared spectroscopy values are nearly equal at all times. Inadequate retrograde cerebral perfusion flow and excessive flows causing cerebral edema could affect near-infrared spectroscopy values adversely. Near-infrared spectroscopy values alone probably would be insufficient to help guide titration of retrograde cerebral perfusion pressures. Bilateral reversal of blood flow in the carotid arteries as demonstrated by transcranial Doppler or transpharyngeal ultrasonography would be a valuable adjunct to cerebral oximetry during retrograde cerebral perfusion. Transpharyngeal ultrasonography has the added advantage of its use in examining jugular blood flows and helping in the early identification of cannula malposition. Monitoring flow velocities and blood flow directions in the cerebral vessels using transpharyngeal imaging in patients undergoing aortic arch surgery would take place at the following time points: (1) before instituting cardiopulmonary bypass, (2) soon after initiating cardiopulmonary bypass, and (3) continually thereafter during the entire duration of retrograde cerebral perfusion. Transpharyngeal ultrasonography should be performed by a dedicated professional with experience in intraoperative transesophageal echocardiography while a second anesthesiologist
manages the hemodynamic parameters. As the probe is retracted into the hypopharynx, care must be taken that it is not dislodged from the oral cavity, and trauma to oral structures should be avoided. It is possible that clear images might not be acquired in all patients because the intervening trachea is filled with air. A lower color scale (about 20 cm/sec) might be needed for optimal visualization of the neck vasculature using color Doppler examination. Lastly, this technique should be used in conjunction with cerebral oximetry because there is a dearth of evidence that transpharyngeal ultrasound monitoring of the carotid and/or jugular venous flow actually correlates with cerebral blood flow under the conditions of either lowflow antegrade or retrograde selective cerebral perfusion. An extended use of the transesophageal echocardiography probe for transpharyngeal monitoring of the bilateral carotid arteries at all stages of aortic arch repair is proposed. It would help in the detection of reversal of flow during retrograde cerebral perfusion. Close-proximity transpharyngeal ultrasonic measurement of cerebral blood flow or velocity would help in the detection of clinically significant asymmetry that might suddenly develop but go undetected and result in preventable neurologic injury. ACKNOWLEDGMENT
The authors sincerely thank Dr. Roger Green, FRCS, for his valuable guidance in the preparation of this manuscript.
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