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Continuous nerve blocks for outpatient knee surgery
Continuous Nerve Blocks for Outpatient Knee Surgery Brian A. Williams, Donna Spratt, and Michael L. Kentor
In outpatient knee surgery, perineural catheter techniques are an important advance to further ensure a comfortable same-day discharge after procedures typically associated with significant pain. For outpatients, attention should be directed both to the multimodal treatment of pain as well as to the multimodal prophylaxis of postoperative nausea and/or vomiting. The ability to titrate local anesthetic doses to provide sensory-specific analgesia with minimal motor block is a significant benefit of the perineural catheter technique. For a successful program, key aspects of the facility’s infrastructure need to be addressed, including staffing and teamwork issues. The relevant anatomy is of extreme importance, but equally important is a clear outline of surgical indications such that patients are neither overtreated nor undertreated for surgical pain. Descriptions of technical aspects are included for the following continuous nerve blocks: (i) femoral, (ii) psoas compartment lumbar plexus, (iii) posterior gluteal sciatic, and (IV) posterior subgluteal sciatic. © 2004 Elsevier Inc. All rights reserved.
postoperatively. Indwelling perineural catheters can be dosed for surgery and then maintained with a continuous infusion of a low concentration of local anesthetics, to maximize motor function while providing sufficient analgesia. Bolus dosing can supplement the infusion at the patient’s discretion, if this feature is available with the selected infusion device. In this article, we will begin by describing some important institutional considerations specific to RA catheters used after outpatient knee surgery. We will then describe some caveats in patient selection, anesthesia care planning including time management considerations, fundamental anatomy, and relevant pearls in the placement of femoral, lumbar plexus, and sciatic (gluteal and subgluteal) catheters and list in detail the surgical indications for single-injection nerve blocks versus continuous infusions based on 8 years’ experience at the University of Pittsburgh Medical Center.
Infrastructure in Brief he benefits of regional anesthesia (RA) can be extended from the ambulatory surgery setting into the patient’s home postoperatively via perineural catheter placement. RA decreases the morbidity associated with (i) the stress response of surgery secondary to pain,1,2 and (ii) postoperative activity limitations secondary to the surgery. RA decreases the side effects associated with parenteral and/or oral opioids, such as respiratory depression, somnolence, nausea, and vomiting. Indwelling catheters for knee procedures may be exceptionally advantageous and have the potential to produce high patient satisfaction. Moreover, extrapolating from long-duration single-injection nerve block experiences,3-8 continuous RA techniques have the potential to decrease the hidden costs of procedures related to morbidity, unplanned hospital admissions, and delayed rehabilitation, all of which can likely be translated into healthcare cost savings. Successful implementation of an anesthetic plan, which for this discussion will include indwelling catheters, ideally begins preoperatively in the surgeon’s office, where s/he discusses RA and continuous nerve block catheters with the patient. On the day of surgery, the analgesic plan should be multimodal,9-11 as should be prophylaxis for postoperative nausea and/or vomiting (PONV).12,13 Preemptive analgesia should include an inhibitor of the cyclooxygenase type 2 enzyme (COX-2 inhibitor),14-16 started preoperatively and continued for 5 to 7 days
T
From the University of Pittsburgh School of Medicine, Department of Anesthesiology, Pittsburgh, PA. Address correspondence to Brian A. Williams, MD, MBA, UPMC South Side, Department of Anesthesiology, 2000 Mary Street, Pittsburgh, PA 15203. E-mail: [email protected]. © 2004 Elsevier Inc. All rights reserved. 1084-208X/04/0802-0005$30.00/0 doi:10.1053/j.trap.2004.06.001
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Transition of Gold Standards When replacing one generally accepted analgesic strategy (eg, oral opioids) with another (eg, nerve block infusions), stakeholders in this transition should first analyze both strategies. Ideally, the benefits of the newer method should outweigh inherent risks and expense, while the newer method should also be documented with the given patient population as being more clinically efficacious; otherwise there would be no need for the change.
Institutional Considerations An institution managing an outpatient regional anesthesia program requires meaningful patient teaching throughout the entire care process. Preoperative physical therapy teaching will allow the patient to master ambulation with an extremity restricted by both surgical procedure and nerve block analgesia. A postoperative evaluation (at the time of same-day discharge) of the patient’s analgesic level and physical function when the nerve block bolus is effectively at a steady state will allow for a titration plan of the local anesthetic to an optimal infusion rate. At this time, the ambulation strategies learned earlier are reinforced. Discharge instructions from the day surgery facility should include follow-up instructions and the phone/pager number of the catheter care team. The catheter care team should respond promptly to all inquiries, given the potential for a serious mishap.
Patient Selection Appropriate patient selection is essential for the successful use of perineural catheters in the ambulatory setting. Medical conditions such as coagulopathy, anticoagulation needs, and infec-
Techniques in Regional Anesthesia and Pain Management, Vol 8, No 2 (April), 2004: pp 76-84
tion are as important in determining the patient’s ineligibility to receive an indwelling catheter as are the patient’s inability to care for the device or to recognize a complication. It should be noted that anticoagulation is not a contraindication for perineural catheter placement and use, based on current evidence. The patient must comprehend the risks and benefits of regional anesthesia employing continuous nerve blockade. Since the patient will be managing the catheter and infusion device unsupervised, in his/her home, s/he must be aware of inherent risks associated with indwelling catheters. Disconnections, pump failure, and signs of LA toxicity must be recognized promptly and remedied immediately. Furthermore, s/he must identify motor weakness, which may accompany the analgesia, and compensate appropriately to avoid injury while still working to achieve his/her physical therapy objectives. Additionally, motivation (driven by a patient’s and a community’s history of failed traditional analgesic techniques such as oral opioids) can potentiate the success of perineural catheters and the institution’s outpatient RA program. Thus, success will be largely determined by appropriate patient selection.
Anesthesia Planning and Time Management Forecasting Time Management Issues, and Planning Appropriately Operating room schedules and start times are in constant flux. Close communication with the operating room staff can defer turnover delays secondary to catheter placement, for cases that have an unknown start time. However, in most institutions, the only viable alternative for minimizing turnover delays (secondary to the complexities of perineural catheter placement) may be to have patients report to the hospital earlier than “normal.” This 1 to 2 hour investment of the patient’s time would then be rewarded with the “best chance” for successful 40 to 80 hours of meaningful postoperative analgesia. Planning is essential to all anesthetic techniques that include indwelling catheters. The patient should arrive at the hospital, and soon after be taken to the “block area,” with sufficient time for (i) placing the catheter, and (ii) achieving the desired level of anesthesia/analgesia. Catheter placement may take 10 to 40 minutes each. Some knee procedures require the placement of two catheters for postoperative analgesia. While experience can shorten the placement time, one cannot discount the delays which may accompany the patient’s body habitus or other anatomical variances. An assistant (such as a resident, a physician’s assistant, or a subspecialized nurse) can facilitate the process and coordinate the patient’s catheter needs, affording the staff anesthesiologist the time to discuss the risks, benefits, and alternatives to perineural catheters with multiple patients, and to place the catheters. The assistant would review the schedule, assemble the necessary supplies in advance, and be the liaison between the OR and the perineural catheter team, calling for patients and ensuring that patients transition through the process expeditiously. The assistant would position the patient and place appropriate monitors before catheter placement, and then assist during the procedure by administering sedation and by manipulating the peripheral nerve stimulator. S/he could then secure the catheter and prepare the paperwork while the staff anesthesiologist moves on to another case. An effective assistant will allow the staff anesthesiologist more time for direct NERVE BLOCKS FOR OUTPATIENT KNEE SURGERY
patient care by completing some of these duties described above.
Anesthetic Plans That Include Indwelling Catheters There are three basic anesthetic plans that include indwelling perineural catheters. Each technique has special considerations which are reviewed below. First, the anesthetic plan could rely solely on the regional block for surgical analgesia. This technique requires higher doses of LA and has several time management issues. Accurately estimating the time requirements for several RA steps that are variable in nature is necessary to successfully employ this technique. In addition to the time required to place the catheter, the operator must allow for local anesthetic “set-up time” to provide for surgical analgesia. Less intense monitoring of the patient is necessary after the placement of the perineural catheter and before the patient’s transfer into the operating room, thus affording the anesthesiologist necessary “downtime” for documentation. Second, the anesthetic plan could consist of spinal or general anesthesia (GA) as the definitive intraoperative anesthetic, with preoperative activation of the regional block for intraoperative benefit for “preemptive analgesia.” Although the “preemptive effect” is controversial in human studies, active intraoperative nerve blocks clearly reduce intraoperative GA requirements (when GA is used) and effectively prolong the duration of spinal anesthesia if the nerve distribution in question is blocked. This technique still has time management issues that include catheter placement and starting the catheter infusion before or during the procedure, or bolusing the catheter before the procedure to reduce spinal/GA requirements, with subsequent infusions started postoperatively (Table 1). Third, the anesthetic plan could again rely on a spinal or GA as the definitive intraoperative anesthetic, and use of the perineural catheter as needed, postoperatively. This technique has some time management issues, but also allows for intraoperative neurological monitoring such as somatosensory evoked potentials and also allows for the evaluation of function before catheter activation. This option is essential when there is an expected prolonged tourniquet time, or a blameful surgeon. Furthermore, posterior knee pain is usually attributable to the sciatic nerve; thus activation of a sciatic catheter would occur only after demonstration of adequate sciatic nerve function (namely, dorsiflexion attributed to the common peroneal nerve) for outpatients with likely posterior knee pain after procedures such as high tibial osteotomy and multiligament reconstruction.
Catheter Placement Placement of a Femoral Nerve Catheter Anatomy and Anatomic Relationships The femoral nerve originates from nerve roots L2-L4. Osseous sensory innervation provided by the femoral nerve includes the patella and most of the femur, with the exception of the posterior femur and the greater trochanter. Muscular sensory and motor innervation to the anterior thigh muscles (ie, quadriceps femoris) is provided by the femoral nerve, which gives rise to a patellar twitch when stimulated. Dis-
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TABLE 1. UPMC South Side Hospital: Recommended Analgesia for Knee Surgery Category I (Mild) No blocks unless unanticipated postoperative pain occurs Category II (Moderate) Single-injection femoral nerve block recommended: Arthrotomy, deep hardware removal, microfracture, mosaicplasty/chondroplasty, ACL allograft Femoral bolus: 30 mL ropivacaine 0.5% No sciatic block unless unanticipated pain refractory to femoral block Continuous catheter recommended: ACL patellar tendon autograft, femur osteotomy Femoral catheter initial bolus: 20-30 mL 0.33% ropivacaine Femoral catheter infusion: 5 mL/h 0.2% ropivacaine No sciatic block unless unanticipated pain refractory to femoral block Category III (Severe) Procedure
Femoral nerve block
Sciatic nerve block
Most Invasive Category III (test for dorsiflexion before ablating sciatic nerve motor response) Total knee replacement Continuous femoral catheter Continuous sciatic catheter Initial bolus: Initial bolus: High tibial osteotomy 20-30 mL 0.33% ropivacaine 5-10 mL 0.2% ropivacaine Multiligament reconstruction Catheter dose: Catheter dose (postoperatively): (including PCL, LCL, MCL, POL) 5 mL/h 0.2% ropivacaine 5-20 mL 0.2% ropivacaine, then 3 mL/hF 0.2% ropivacaine Posterolateral corner reconstruction Moderately Invasive Category III ACL hamstring autograft Meniscal reconstruction Unicompartmental knee arthroplasty Less Invasive Category III Distal patella realignment
Continuous femoral catheter Initial bolus: 20 mL 0.2% ropivacaine Catheter dose: 5 mL/h 0.2% ropivacaine
Single-injection sciatic: 20 mL 0.33% ropivacaine
Single-injection femoral: 30 mL 0.33% ropivacaine
Single-injection sciatic: 20 mL 0.2-0.33% ropivacaine
Algorithm for the use of nerve block additives: If a catheter is to be used, clonidine is not routinely added If no catheter is used, clonidine is routinely recommended Regardless of catheter status, buprenorphine may be a very useful analgesic adjunct (as part of the catheter-bolus dose or single-injection dose). Buprenorphine dose should be restricted to a total of 150 m per adult patient to prevent nausea, vomiting, and pruritis associated (anecdotally) with higher doses. UPMC: University of Pittsburgh Medical Center; ACL: anterior cruciate ligament; PCL: posterior cruciate ligament; LCL: lateral collateral ligament; MCL: medial collateral ligament; POL: posterior oblique ligament.
tally in the groin, the femoral nerve becomes the saphenous nerve, which acts in a pure sensory capacity to innervate the medial leg and ankle. Thus the femoral nerve provides sensory innervation to the femur, anterior thigh, and medial leg and ankle, as well as motor innervation to the muscles responsible for a patellar contraction. Judging proximity to the femoral nerve depends on the motor component of the femoral nerve to produce a patellar twitch. The femoral nerve can be indirectly identified by means of its proximity to other landmarks. At a level 2 cm inferior to the inguinal ligament, the femoral nerve is 1 cm lateral to the femoral artery (Fig 1). This relationship is maintained for 3 to 5 cm distal to this point. Superficial to the nerve is the fascia iliaca, which gives rise to a small local contraction when stimulated. Deep to the femoral nerve is the iliopsoas muscle, which gives rise to a stronger local contraction when stimulated. The femoral nerve is close (medial) to the sartorious muscle, which presents as a recognizable twitch when stimulated. If the femoral artery is not palpable, a Doppler signal can easily identify this landmark, which can then be used to approximate the femoral nerve. One other anatomic “pearl” is that the location of the femoral nerve lies one-third of the distance from the pubic tubercle to the anterior superior iliac spine.
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Femoral Catheter Technique for Continuous Infusions Guidelines for placing indwelling catheters include patient positioning, marking the site of the femoral nerve, and using the correct needle trajectory. General positioning should consist of a patient in the supine position with the operator at a comfortable working level near the upper thigh. The site of the femoral nerve should be marked with an indelible marker. After cleansing the skin with alcohol, a 2 to 3 mL subcutaneous injection of local anesthetic should be placed, taking care to avoid blocking this superficial nerve. This will serve to both render the skin insensate and identify the site of the femoral nerve should the ink markings be erased. Please note that if the local skin or underlying tissue at the site of the planned femoral perineural catheter is not suitable (groin skin breakdown or infection, or previous vascular surgery involving the femoral artery), it may be prudent to use a posterior, psoas compartment lumbar plexus nerve block and perineural catheter instead. Skin preparation, needle insertion and trajectory, and nerve stimulator guidelines. With strict adherence to sterile technique, the area should then be cleansed and draped in a fashion so as to allow visualization or palpation of the patellar twitch. WILLIAMS ET AL
Fig 1. Landmarks for the femoral nerve block. The femoral artery (FA) is identified by palpation. The needle entry point for the femoral nerve block (indicated by the asterisk *) is usually 1 –1.5 cm lateral to the palpated femoral artery, and 3-4 cm caudad to the inguinal crease.
Trajectory of the needle is ⱕ30° with the bevel pointing cephalad, while the needle is directed parallel to the femoral artery. This is accomplished with the operator’s 3rd digit of the left hand resting on the femoral arterial pulse, while the right hand’s first and second digits guide the needle. Resting the ulnar surface of the right hand, more cephalad than the muscles being stimulated may help to stabilize the needle. While these hand positions are suitable for the start of the procedure, adjustments are often needed once the twitches have lessened to provide maximal stability for the injection of local anesthetic (if using a nonstimulating catheter) and the placement of the catheter. The nerve stimulator should be set at a current of 1.0 mA, as the 5- to 10-cm needle enters the skin. This current should provide both safety for the surrounding tissue as well as sufficient stimulus to evoke a twitch. Once the patellar twitch is evoked, the operator decreases the current while maximizing the twitch response continuously, by changing the position of the tip of the needle through slight rotation (while maintaining a cephalad trajectory), by minimal movements in the cephalad, caudad, medial, or lateral directions, or by advancing or withdrawing the needle. While the natural tendency for the operator may be to probe deeper, experience will demonstrate withdrawing the needle to a more superficial location is usually more successful in reproducing or enhancing the twitch response. If the evoked twitch is the medial twitch of the vastus medialis, then the introducer is likely too medial, and the operator should simply reposition the introducer needle tip 0.3 to 1 cm lateral (without exiting the skin). If a local twitch of fascia lata is generated, then the introducer is too shallow, and the operator should reposition the needle deeper. Once the current intensity is reduced to approximately 0.4 to 0.5 mA, with maintenance of the twitch, termination of the twitch response at 0.2 mA should be demonstrated. This will NERVE BLOCKS FOR OUTPATIENT KNEE SURGERY
help confirm (but not definitively) a peri-neural location (as opposed to an intraneural location), which is an endpoint warranting documentation. Twitches evoked in athletic patients may cause needle displacement. Patients with diabetes, or patients with peripheral neuropathy, may require a nerve stimulator pulse width greater than 0.3 ms (the limit of a standard peripheral nerve stimulator). After achieving the patellar twitch at an appropriate intensity, assuming a nonstimulating catheter is used, 20 to 40 mL of local anesthetic is incrementally injected (aspirating the syringe for heme every 5 mL of injection) while assessing neurological and hemodynamic status. Placing and securing the catheter. Finally, the catheter is placed and secured. The operator advances the catheter, with gentle pressure, 4 to 5 cm beyond the tip of the introducer. The bevel of the introducer should still be oriented cephalad. Risks of catheter knotting versus dislodgment should be evaluated by the operator when considering the catheter depth. Obese patients may require the catheter to be placed at a greater depth both to overcome the potential dislodgement by redundant soft tissue as well as to overcome the manual buttressing/compression of the same redundant tissue which may have occurred with the stimulation phase. After the catheter is threaded and the introducer nerve stimulator needle is removed, the area is finally prepared with a sterile adhesive liquid, after which thin sterile tape is laid (for example, in a crisscross fashion above the coiled catheter beneath); this adhesive dressing is followed by sterile transparent adhesive dressing. It may be wise to secure the edges of the sterile transparent dressing with an adhesive tape that includes imbedded zinc oxide, since patients discharged home will be discouraged from dressing changes until the time has come for catheter removal. Considerations of intraoperative thigh tourniquet use will require careful positioning of the catheter. Coiling the catheter be-
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Fig 2. Landmarks for the lumbar plexus continuous psoas compartment block, and for two approaches to the sciatic nerve block. For the lumbar plexus block (with landmark lines indicated in white), patient assumes a lateral decubitus position with surgical side up. The intercristal line (ICL) is drawn and crosses midline at the level of L4. Then a spinous process line (SPL) is drawn from approximately L3 to L5. A parallel line to the SPL is drawn cephalad originating from the posterior superior iliac spine (PSIS). Two-thirds of the distance from the SPL to the PSIS parallel line marks the entry point (green dot with white arrow directed at it) for the perpendicular needle entry of the nerve stimulator introducer needle. For the sciatic nerve blocks, the black markings on this figure are used. For the traditional gluteal approach to the sciatic nerve block, the most cephalad aspect of the greater trochanter (GT) is palpated. A line is drawn from there to the PSIS. Another line is drawn from the GT to the tip of the coccyx. The midpoint of the GT-PSIS line is bisected, with a perpendicular line drawn toward the GT-coccyx line. The skin insertion point for this approach to the sciatic nerve block is adjacent to the asterisk (*). Another approach can be considered, in which the groove between inferolateral edge of the gluteus maximus (GM) and the lateral edge of the long head of the biceps femoris (BF) is identified. The skin insertion point for this approach to the sciatic nerve block is in this groove, 3-4 cm caudad to the most caudad palpable portion of the gluteus maximus muscle (indicated by the symbol “#”). In our experience, this has served as a useful approximation of the skin entry point described by di Benedetto et al (CITE with superscript here), in which they draw a line from the GT to the ischial tuberosity, then from the mid-point of this line, a second line is drawn perpendicularly and extended 4 cm caudad, with the end of this perpendicular line (not shown in the figure) representing the entry point of the needle.
neath several sterile transparent adhesive dressings, while ensuring that the proximal end with the Luer connector is positioned away from the planned tourniquet location, is the final necessary step to placing and securing the femoral nerve catheter.
Lumbar Plexus Anatomy and Catheter Placement The lumbar plexus originates from ventral rami of lumbar nerve roots L2 to 4 and forms between the superficial and deep planes of the psoas muscle at the level 4th lumbar vertebral body. Moving distally, this plexus then forms the lateral femoral cutaneous (L2-3), femoral (L2-4), and obturator (L3-4) nerves. The lateral femoral cutaneous nerve provides sensory innervation to the anterior lateral and posterior medial thigh, while the femoral nerve provides sensory innervation from the anterior thigh and motor innervation to the quadriceps muscles, which produce a quadriceps twitch. The obturator nerve innervates hip adductors which adduct the leg and also carries sensory information from patches of the medial thigh. We endorse the psoas compartment lumbar plexus anatomic landmarks recently published by Capdevila and coworkers.17 In this article, computed tomography verification of the surface anatomic landmarks showed that the optimal needle entry
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point for the lumbar plexus block in the psoas compartment is somewhat more medial than originally described. The insertion point should occur on the intercristal line; the transverse process of L4 at the level of the lumbar plexus is 1 cm caudad to the intercristal line. A perpendicular line originating from the posterior superior iliac spine (PSIS) should be drawn to intersect with the intercristal line. Then, along the intercristal line originating from the spinous process, a mark should be made twothirds of the distance from the spinous process to the intersection point of the PSIS and intercristal lines (Fig 2). The 10-cm nerve stimulator introducer needle is inserted perpendicular to all planes, with the bevel pointing cephalad. After skin and subcutaneous fat, the needle then traverses the iliocostalis lumborum muscles and then the paravertebral muscles, both of which may produce a local contraction. These layers of needle passage occur within 6 to 7 cm of entry, typically. If the L4 transverse process is contacted, the needle is withdrawn by a fraction of a centimeter and is systematically “walked off” the cephalad aspect of the transverse process. If neither desired twitch nor transverse process is encountered (the average depth to achieve the desired quadriceps twitch response is 85 mm in men and 70 mm in women), the needle is withdrawn without WILLIAMS ET AL
Fig 3. Neurostimulation during perineural catheter insertion. For this sciatic nerve block procedure, the nerve-stimulating introducer needle was used to identify the sciatic nerve initially, via a clip-connecting wire carrying current from a peripheral nerve stimulator to the insulated needle. In this photo, the wire clip has been moved from the needle to the exposed stylet (indicated by the asterisk *) at the end at the proximal tip of the perineural catheter. Electrical current is then carried via the stylet to the distal tip of the catheter, guiding the operator’s insertion of the catheter through the nerve-finding needle, while twitch of the calf, ankle, and foot are observed. The equipment used is the Arrow ® StimuCathTM AB-05060 Continuous Nerve Block Set (Arrow International, Reading, PA).
exiting the skin and is systematically fanned from the initial entry point using small lateral increments, to try not to direct the needle medially (ie, toward the epidural space). Most commonly, the lumbar plexus can be identified within 2 cm of the L4 transverse process, once contacted. When placing the lumbar plexus needle, the operator seeks a quadriceps twitch (as opposed to an obturator twitch) since the quadriceps twitch is easier to identify when the patient is in the lateral position. The quadriceps twitch also confirms needle placement central to all of the nerves within the planes of the psoas compartment. The principles of catheter insertion once the desired twitch is identified follow the principles described for femoral perineural catheters above. It should be noted that the area surrounding the lumbar plexus is richly vascularized; thus, heme may be present in the incremental syringe aspirations up to 20% of the time.
This palpable margin of the gluteus maximus should be distinguished from the lateral margin of the vastus medialis, which lies a few centimeters laterally. Needle insertion for perineural catheter placement is typically perpendicular to all planes for traditional posterior sciatic (gluteal) approaches. In our experience with the subgluteal block, we have directed introducer needles cephalad with success, although diagrams by the author of the subgluteal approach use needles directed both cephalad and caudad. The principles of catheter insertion once the desired twitch is identified follows the principles described for femoral and lumbar plexus perineural catheters described above.
Placement of a Sciatic Nerve Catheter
Indications for Catheter Placement
The anatomic principles of sciatic nerve blocks using a traditional posterior gluteal approach (with landmarks shown in Fig 2) are well-outlined in textbooks and atlases. The needle is inserted typically perpendicular to all planes, like the lumbar plexus block above. A new subgluteal approach has emerged,18 which appears to confer less patient discomfort than traditional posterior gluteal approaches.19 The landmarks that we have found most helpful are (i) the lateral edge of the long head of the biceps femoris (medially), and (ii) the infero-medial edge of the gluteus maximus (laterally, as the gluteus maximus courses further inferolaterally toward its insertion on the proximal posterior femur).
Table 1 is a detailed algorithm that is used at the South Side Hospital division of the University of Pittsburgh Medical Center for our outpatients presenting for knee surgery. It should be noted that we have been using nerve block catheters for not quite one year at the time of this writing; our conversion to these catheters from the routine use of single-injection blocks was prompted by some surgeons requesting motor preservation. It should be emphasized that patient selection for catheter use is based largely on the criteria described earlier. In patients whom catheters are deemed inappropriate, the longest possible duration of single-injection is used. The surgeon commonly needs to be repeatedly reminded that motor preservation is
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Strategies and Indications for Outpatient Knee Surgery Catheter Placement, Confirmation, Dosing, and Management
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Fig 4. Tunneling the perineural catheter. After the perineural catheter is placed and its placement is confirmed by stimulation of the stylet, the introducer needle is carefully removed with special attention directed toward not accidentally removing or displacing the catheter simultaneously. Once the introducer needle is removed, the perineural catheter is further secured via subcutaneous tunneling. Routine intravenous catheters can be used for perineural catheter tunneling. In this photo of a femoral nerve block, a 14-gauge intravenous cannula is separated from its underlying needle. The needle (indicated by the asterisk [*]) has its tip passed through the original skin insertion site, and is passed laterally. Upon needle exit, the plastic cannula (the hub of which is indicated by the symbol [#]) is passed retrograde over the tunneled needle. The needle is then removed and the perineural catheter is passed from the distal tip of the plastic cannula back through the hub of the cannula. At this point, the plastic cannula is removed completely, ensuring that the perineural catheter is not displaced any more than is necessary to have a satisfactory subcutaneous tunnel for the perineural catheter. The equipment used is the Arrow ® StimuCathTM AB-05060 Continuous Nerve Block Set (Arrow International, Reading, PA).
meaningless if pain precludes meaningful advancement of physical therapy objectives. As far as we are aware, there are no data indicating that motor sparing in a peripheral nerve block, when all else is equal with respect to analgesic duration, has any effect on long-term patient outcome as far as ambulation and knee function. We preferentially use spinal anesthesia as the definitive intraoperative anesthetic, currently using hyperbaric ipsilateral solutions of procaine or bupivacaine, with doses titrated to anticipated surgical duration. The typical procaine dose is 50 to 70 mg, and the typical bupivacaine dose is 9 to 12 mg. It should be emphasized that we use the lateral decubitus position for these spinals, with the aperture of the pencil-point needle directed to the decubitus side, to maximize anesthesia of the surgical knee and minimize anesthesia in the nonsurgical knee. When compared with our previous reports in which we performed spinal anesthesia with patients in the sitting position using isobaric procaine, mepivacaine, and bupivacaine,5,6 we have found anecdotally that the ipsilateral hyperbaric spinal anesthesia strategy has significantly reduced time-to-discharge by nearly half. Combining this laterality/baricity principle with the suggestion by Mulroy and coworkers20 that patients need not void as a mandate before discharge after short-acting neuraxial anesthesia has the potential to significantly reduce discharge times. The block categories described in Table 1 were based on
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descriptive data detailed in a recent article describing our experiences with outpatients from 1995 to 1999.7 This article retrospectively categorized surgical procedures in which no blocks were needed versus procedures when femoral with or without sciatic nerve blocks were needed (a two-tier system). However, we clinically use a three-category system for predicting pain severity based on nerve distributions in which there is significant surgical trespass. For simplicity, we delineate using categories I (“mild”), II (“moderate”), and III (“severe”). Category I consists of procedures that are truly “minimally invasive,” consisting of arthroscopic debridement, meniscectomy, and small meniscal repairs. Category II consists of procedures in which the most significant postoperative pain is restricted to the femoral nerve distribution. We now have two subcategories of Category II, distinguished by the adequacy of a single-injection femoral nerve block versus the apparent necessity of a femoral nerve catheter. Table 1 delineates the procedures in which the need for the perineural catheter is apparent, based on internal data and clinical anecdotes to date. Category III is quite complex. These procedures typically require nerve block analgesia in the femoral and sciatic nerve distributions. The complexity in Category III lies in the anesthesiologist’s predictions of the sufficiency of single-injection femoral and sciatic nerve blocks versus the potential benefit of adding femoral with or without sciatic nerve catheters. Table 1 WILLIAMS ET AL
Fig 5. Testing the perineural catheter after tunneling with electrostimulation. In this figure, the asterisk (*) indicates the original skin entry point for the nerve finding needle, and the symbol “#” indicates the perineural catheter exit site after subcutaneous tunneling. At this point, the snap-top luer connector (indicated by the arrow) is connected to the proximal tip of the perineural catheter. The clip at the end of the wire (connected to the peripheral nerve stimulator) is now connected to the metal extension from the snap connector, which carries electrical current through the insulated perineural catheter to the distal catheter tip. Using this feature, the perineural catheter can be confirmed for placement before dosing takes place. On occasion, the absence of twitch at this point is commonly resolved by slowly withdrawing the catheter a millimeter at a time, until the desired twitch is produced once again. If no twitch is produced, however, the procedure would need to be repeated. The equipment used is the Arrow ® StimuCathTM AB-05060 Continuous Nerve Block Set (Arrow International, Reading, PA).
shows our current clinical impression of surgical procedure subtypes warranting the incremental levels of postoperative analgesia effort required.
Confirming Perineural Catheter Placement The use of perineural catheters in patients to be discharged home can be complicated, especially when verifying catheter placement before discharge. There are two immediately apparent means of verifying catheter placement. First, a test dose of local anesthetic can be injected through the catheter, and if anesthesia or analgesia is produced, then the catheter is assumed to be placed correctly. The inherent disadvantage of this approach is that the test dose used which would verify catheter placement may also produce a definitive motor block, which surgeons may wish to avoid. Another disadvantage is that the test dose volume (if the test dose is unsuccessful) may pose restrictions on subsequent local anesthetic dosing should the block or catheter be re-attempted, not to mention pose a potential restriction in nerve finding (previous twitch ablation, or tissue plane distortion by the previously injected local anesthetic volume). The other method of testing catheter placement is by electrostimulation through the inserted perineural catheter. This process has been described in detail for brachial plexus blocks for
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shoulder surgery by Boezaart.21 The catheter used for this process must include an imbedded wire which can conduct electrical current from the catheter origin (commonly via an electrical adapter incorporated to the Luer-lock snap connector) through the insulated catheter, to the catheter tip. The operator can stimulate such a catheter during catheter insertion through the nerve-finding needle (Fig 3), after removal of the nervefinding needle, after catheter tunneling (Figs 4 and 5), and after dressing, to confirm the absence of displacement at every step of inserting and securing the catheter. With stimulating catheters, boluses with local anesthetics should occur through the confirmed catheter, and not the nerve-finding needle, to maximize the benefits of using this specialty equipment. Pending studies which compare the success rates of perineural catheterization when using stimulating versus nonstimulating catheters, anesthesiologists should consider the costs of the equipment used for catheter placement, planned infusion pump device for outpatients, and the hidden costs of failure of the technique should the patient only have a nerve block duration of 24 hours or less with a catheter and infusion pump in place. Depending on how this comparative research ultimately pans out with respect to success rates, patients deserve the best chance to have the procedure completed successfully the first
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time, with minimal risk for return hospital visits with uncontrolled pain.
Dosing and Management of Perineural Catheters We recommend the use of infusion pumps in which a basal infusion occurs (eg, 5 mL/h) with the potential for a patientcontrolled bolus (eg, 5 mL bolus with a 60-minute lockout). Patients should be definitively instructed on how and when to clamp the infusion pump tubing (eg, for an elastomeric pump), or to power the device off (eg, with an electronic pump) should the nerve distribution in question accumulate a motor block effect and guidelines should be provided (return of motor function and onset of slight pain) as to when to resume the infusion.
Conclusions In outpatient knee surgery, perineural catheter techniques are an important advance to further ensure a comfortable same-day discharge after procedures typically associated with significant pain, procedures often justifying a planned or unplanned hospital admission. The ability to titrate local anesthetic doses to provide sensory-specific analgesia with minimal motor block is a significant benefit of the perineural catheter technique. Research is needed to determine (i) perineural catheter success rates when stimulating versus nonstimulating catheters are used; (ii) long-term benefits of sensory-specific analgesia when compared with blocks which transiently ablate all motor function; and (iii) optimal analgesic duration. In addition, epidemiologic studies of same-day-discharged patients are needed to determine success rates and complication rates (patient falls, infections, persistent paresthesiae, or other neurologic sequelae) related to the use of long-duration single-injection nerve blocks and perineural catheters.
References 1. Adams HA, Saatweber P, Schmitz CS, Hecker H: Postoperative pain management in orthopaedic patients: no differences in pain score, but improved stress control by epidural anaesthesia. Eur J Anaesthesiol 19:658-665, 2002 2. Breslow MJ: The role of stress hormones in perioperative myocardial ischemia. Int Anesthesiol Clin 30:81-100, 1992 3. Williams BA, DeRiso BM, Engel LB, Figallo CM, Anders JB, Sproul KA, Ilkin H, Harner CD, Fu FH, Nagarajan NJ, Evans JH 3rd, Watkins WD: Benchmarking the perioperative process: II. Introducing anesthesia clinical pathways to improve processes and outcomes, and reduce nursing labor intensity in ambulatory orthopedic surgery. J Clin Anesth 10:561-569, 1998 4. Williams BA, DeRiso BM, Figallo CM, Anders JB, Engel LB, Sproul KA, Ilkin HM, Harner CD, Fu FH, Nagarajan NJ, Evans JH 3rd, Watkins WD: Benchmarking the perioperative process: III. Effects of regional anesthesia clinical pathway techniques on process efficiency and recovery profiles in ambulatory orthopedic surgery. J Clin Anesth 10:570-578, 1998 5. Williams BA, Kentor ML, Williams JP, Figallo CM, Sigl JC, Anders JW, Bear TC, Tullock WC, Bennett CH, Harner CD, Fu FH: Process
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analysis in outpatient knee surgery: Effects of regional and general anesthesia on anesthesia-controlled time. Anesthesiology 93:529538, 2000 Williams BA, Kentor ML, Williams JP, Vogt MT, DaPos SV, Harner CD, Fu FH: PACU bypass after outpatient knee surgery is associated with fewer unplanned hospital admissions but more phase II nursing interventions. Anesthesiology 97:981-988, 2002 Williams BA, Kentor ML, Vogt MT, Williams JP, Chelly JE, Valalik S, Harner CD, Fu FH: Femoral-Sciatic nerve blocks for complex outpatient knee surgery are associated with less postoperative pain before same-day discharge: A review of 1200 consecutive cases from the period 1996-1999. Anesthesiology 98:1206-1213, 2003 Williams BA, Kentor ML, Vogt MT, Vogt WB, Coley KC, Williams JP, Roberts MS, Chelly JE, Harner CD, Fu FH: The economics of nerve block pain management after anterior cruciate ligament reconstruction: Significant hospital cost savings via associated PACU bypass and same-day discharge. Anesthesiology 2004; in press Kehlet H, Dahl JB: The value of “multimodal” or “balanced analgesia” in postoperative pain treatment. Anesth Analg 77:1048-1056, 1993 Menigaux C, Guignard B, Fletcher D, Sessler DI, Dupont X, Chauvin M: Intraoperative small-dose ketamine enhances analgesia after outpatient knee arthroscopy. Anesth Analg 93:606-612, 2001 Reuben SS, Steinberg RB, Cohen MA, Kilaru PA, Gibson CS: Intraarticular morphine in the multimodal analgesic management of postoperative pain after ambulatory anterior cruciate ligament repair. Anesth Analg 86:374-378, 1998 Gupta A, Wu CL, Elkassabany N, Krug CE, Parker SD, Fleisher LA: Does the routine prophylactic use of antiemetics affect the incidence of postdischarge nausea and vomiting following ambulatory surgery? A systematic review of randomized controlled trials. Anesthesiology 99:488-495, 2003 Desilva PH, Darvish AH, McDonald SM, Cronin MK, Clark K: The efficacy of prophylactic ondansetron, droperidol, perphenazine, and metoclopramide in the prevention of nausea and vomiting after major gynecologic surgery. Anesth Analg 81:139-143, 1995 Reuben SS, Fingeroth R, Krushell R, Maciolek H: Evaluation of the safety and efficacy of the perioperative administration of rofecoxib for total knee arthroplasty. J Arthroplasty 17:26-31, 2002 Reuben SS, Bhopatkar S, Maciolek H, Joshi W, Sklar J: The preemptive analgesic effect of rofecoxib after ambulatory arthroscopic knee surgery. Anesth Analg 94:55-59, 2002 Desjardins PJ, Shu VS, Recker DP, Verburg KM, Woolf CJ: A single preoperative oral dose of valdecoxib, a new cyclooxygenase-2 specific inhibitor, relieves post-oral surgery or bunionectomy pain. Anesthesiology 97:565-573, 2002 Capdevila X, Macaire P, Dadure C, Choquet O, Biboulet P, Ryckwaert Y, D’Athis F: Continuous psoas compartment block for postoperative analgesia after total hip arthroplasty: New landmarks, technical guidelines, and clinical evaluation. Anesth Analg 94:16061613, 2002 di Benedetto P, Casati A, Bertini L, Fanelli G, Chelly JE: Postoperative analgesia with continuous sciatic nerve block after foot surgery: A prospective, randomized comparison between the popliteal and subgluteal approaches. Anesth Analg 94:996-1000, 2002 di Benedetto P, Casati A, Bertini L, Fanelli G: Posterior subgluteal approach to block the sciatic nerve: Description of the technique and initial clinical experiences. Eur J Anaesthesiol 19:682-686, 2002 Mulroy MF, Salinas FV, Larkin KL, Polissar NL: Ambulatory surgery patients may be discharged before voiding after short-acting spinal and epidural anesthesia. Anesthesiology 97:315-319, 2002 Boezaart AP: Continuous interscalene block for ambulatory shoulder surgery. Best Practice and Research. Clin Anaesthes 16:295-310, 2002
WILLIAMS ET AL
In outpatient knee surgery, perineural catheter techniques are an important advance to further ensure a comfortable same-day discharge after procedures typically associated with significant pain. For outpatients, attention should be directed both to the multimodal treatment of pain as well as to the multimodal prophylaxis of postoperative nausea and/or vomiting. The ability to titrate local anesthetic doses to provide sensory-specific analgesia with minimal motor block is a significant benefit of the perineural catheter technique. For a successful program, key aspects of the facility’s infrastructure need to be addressed, including staffing and teamwork issues. The relevant anatomy is of extreme importance, but equally important is a clear outline of surgical indications such that patients are neither overtreated nor undertreated for surgical pain. Descriptions of technical aspects are included for the following continuous nerve blocks: (i) femoral, (ii) psoas compartment lumbar plexus, (iii) posterior gluteal sciatic, and (IV) posterior subgluteal sciatic. © 2004 Elsevier Inc. All rights reserved.
postoperatively. Indwelling perineural catheters can be dosed for surgery and then maintained with a continuous infusion of a low concentration of local anesthetics, to maximize motor function while providing sufficient analgesia. Bolus dosing can supplement the infusion at the patient’s discretion, if this feature is available with the selected infusion device. In this article, we will begin by describing some important institutional considerations specific to RA catheters used after outpatient knee surgery. We will then describe some caveats in patient selection, anesthesia care planning including time management considerations, fundamental anatomy, and relevant pearls in the placement of femoral, lumbar plexus, and sciatic (gluteal and subgluteal) catheters and list in detail the surgical indications for single-injection nerve blocks versus continuous infusions based on 8 years’ experience at the University of Pittsburgh Medical Center.
Infrastructure in Brief he benefits of regional anesthesia (RA) can be extended from the ambulatory surgery setting into the patient’s home postoperatively via perineural catheter placement. RA decreases the morbidity associated with (i) the stress response of surgery secondary to pain,1,2 and (ii) postoperative activity limitations secondary to the surgery. RA decreases the side effects associated with parenteral and/or oral opioids, such as respiratory depression, somnolence, nausea, and vomiting. Indwelling catheters for knee procedures may be exceptionally advantageous and have the potential to produce high patient satisfaction. Moreover, extrapolating from long-duration single-injection nerve block experiences,3-8 continuous RA techniques have the potential to decrease the hidden costs of procedures related to morbidity, unplanned hospital admissions, and delayed rehabilitation, all of which can likely be translated into healthcare cost savings. Successful implementation of an anesthetic plan, which for this discussion will include indwelling catheters, ideally begins preoperatively in the surgeon’s office, where s/he discusses RA and continuous nerve block catheters with the patient. On the day of surgery, the analgesic plan should be multimodal,9-11 as should be prophylaxis for postoperative nausea and/or vomiting (PONV).12,13 Preemptive analgesia should include an inhibitor of the cyclooxygenase type 2 enzyme (COX-2 inhibitor),14-16 started preoperatively and continued for 5 to 7 days
T
From the University of Pittsburgh School of Medicine, Department of Anesthesiology, Pittsburgh, PA. Address correspondence to Brian A. Williams, MD, MBA, UPMC South Side, Department of Anesthesiology, 2000 Mary Street, Pittsburgh, PA 15203. E-mail: [email protected]. © 2004 Elsevier Inc. All rights reserved. 1084-208X/04/0802-0005$30.00/0 doi:10.1053/j.trap.2004.06.001
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Transition of Gold Standards When replacing one generally accepted analgesic strategy (eg, oral opioids) with another (eg, nerve block infusions), stakeholders in this transition should first analyze both strategies. Ideally, the benefits of the newer method should outweigh inherent risks and expense, while the newer method should also be documented with the given patient population as being more clinically efficacious; otherwise there would be no need for the change.
Institutional Considerations An institution managing an outpatient regional anesthesia program requires meaningful patient teaching throughout the entire care process. Preoperative physical therapy teaching will allow the patient to master ambulation with an extremity restricted by both surgical procedure and nerve block analgesia. A postoperative evaluation (at the time of same-day discharge) of the patient’s analgesic level and physical function when the nerve block bolus is effectively at a steady state will allow for a titration plan of the local anesthetic to an optimal infusion rate. At this time, the ambulation strategies learned earlier are reinforced. Discharge instructions from the day surgery facility should include follow-up instructions and the phone/pager number of the catheter care team. The catheter care team should respond promptly to all inquiries, given the potential for a serious mishap.
Patient Selection Appropriate patient selection is essential for the successful use of perineural catheters in the ambulatory setting. Medical conditions such as coagulopathy, anticoagulation needs, and infec-
Techniques in Regional Anesthesia and Pain Management, Vol 8, No 2 (April), 2004: pp 76-84
tion are as important in determining the patient’s ineligibility to receive an indwelling catheter as are the patient’s inability to care for the device or to recognize a complication. It should be noted that anticoagulation is not a contraindication for perineural catheter placement and use, based on current evidence. The patient must comprehend the risks and benefits of regional anesthesia employing continuous nerve blockade. Since the patient will be managing the catheter and infusion device unsupervised, in his/her home, s/he must be aware of inherent risks associated with indwelling catheters. Disconnections, pump failure, and signs of LA toxicity must be recognized promptly and remedied immediately. Furthermore, s/he must identify motor weakness, which may accompany the analgesia, and compensate appropriately to avoid injury while still working to achieve his/her physical therapy objectives. Additionally, motivation (driven by a patient’s and a community’s history of failed traditional analgesic techniques such as oral opioids) can potentiate the success of perineural catheters and the institution’s outpatient RA program. Thus, success will be largely determined by appropriate patient selection.
Anesthesia Planning and Time Management Forecasting Time Management Issues, and Planning Appropriately Operating room schedules and start times are in constant flux. Close communication with the operating room staff can defer turnover delays secondary to catheter placement, for cases that have an unknown start time. However, in most institutions, the only viable alternative for minimizing turnover delays (secondary to the complexities of perineural catheter placement) may be to have patients report to the hospital earlier than “normal.” This 1 to 2 hour investment of the patient’s time would then be rewarded with the “best chance” for successful 40 to 80 hours of meaningful postoperative analgesia. Planning is essential to all anesthetic techniques that include indwelling catheters. The patient should arrive at the hospital, and soon after be taken to the “block area,” with sufficient time for (i) placing the catheter, and (ii) achieving the desired level of anesthesia/analgesia. Catheter placement may take 10 to 40 minutes each. Some knee procedures require the placement of two catheters for postoperative analgesia. While experience can shorten the placement time, one cannot discount the delays which may accompany the patient’s body habitus or other anatomical variances. An assistant (such as a resident, a physician’s assistant, or a subspecialized nurse) can facilitate the process and coordinate the patient’s catheter needs, affording the staff anesthesiologist the time to discuss the risks, benefits, and alternatives to perineural catheters with multiple patients, and to place the catheters. The assistant would review the schedule, assemble the necessary supplies in advance, and be the liaison between the OR and the perineural catheter team, calling for patients and ensuring that patients transition through the process expeditiously. The assistant would position the patient and place appropriate monitors before catheter placement, and then assist during the procedure by administering sedation and by manipulating the peripheral nerve stimulator. S/he could then secure the catheter and prepare the paperwork while the staff anesthesiologist moves on to another case. An effective assistant will allow the staff anesthesiologist more time for direct NERVE BLOCKS FOR OUTPATIENT KNEE SURGERY
patient care by completing some of these duties described above.
Anesthetic Plans That Include Indwelling Catheters There are three basic anesthetic plans that include indwelling perineural catheters. Each technique has special considerations which are reviewed below. First, the anesthetic plan could rely solely on the regional block for surgical analgesia. This technique requires higher doses of LA and has several time management issues. Accurately estimating the time requirements for several RA steps that are variable in nature is necessary to successfully employ this technique. In addition to the time required to place the catheter, the operator must allow for local anesthetic “set-up time” to provide for surgical analgesia. Less intense monitoring of the patient is necessary after the placement of the perineural catheter and before the patient’s transfer into the operating room, thus affording the anesthesiologist necessary “downtime” for documentation. Second, the anesthetic plan could consist of spinal or general anesthesia (GA) as the definitive intraoperative anesthetic, with preoperative activation of the regional block for intraoperative benefit for “preemptive analgesia.” Although the “preemptive effect” is controversial in human studies, active intraoperative nerve blocks clearly reduce intraoperative GA requirements (when GA is used) and effectively prolong the duration of spinal anesthesia if the nerve distribution in question is blocked. This technique still has time management issues that include catheter placement and starting the catheter infusion before or during the procedure, or bolusing the catheter before the procedure to reduce spinal/GA requirements, with subsequent infusions started postoperatively (Table 1). Third, the anesthetic plan could again rely on a spinal or GA as the definitive intraoperative anesthetic, and use of the perineural catheter as needed, postoperatively. This technique has some time management issues, but also allows for intraoperative neurological monitoring such as somatosensory evoked potentials and also allows for the evaluation of function before catheter activation. This option is essential when there is an expected prolonged tourniquet time, or a blameful surgeon. Furthermore, posterior knee pain is usually attributable to the sciatic nerve; thus activation of a sciatic catheter would occur only after demonstration of adequate sciatic nerve function (namely, dorsiflexion attributed to the common peroneal nerve) for outpatients with likely posterior knee pain after procedures such as high tibial osteotomy and multiligament reconstruction.
Catheter Placement Placement of a Femoral Nerve Catheter Anatomy and Anatomic Relationships The femoral nerve originates from nerve roots L2-L4. Osseous sensory innervation provided by the femoral nerve includes the patella and most of the femur, with the exception of the posterior femur and the greater trochanter. Muscular sensory and motor innervation to the anterior thigh muscles (ie, quadriceps femoris) is provided by the femoral nerve, which gives rise to a patellar twitch when stimulated. Dis-
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TABLE 1. UPMC South Side Hospital: Recommended Analgesia for Knee Surgery Category I (Mild) No blocks unless unanticipated postoperative pain occurs Category II (Moderate) Single-injection femoral nerve block recommended: Arthrotomy, deep hardware removal, microfracture, mosaicplasty/chondroplasty, ACL allograft Femoral bolus: 30 mL ropivacaine 0.5% No sciatic block unless unanticipated pain refractory to femoral block Continuous catheter recommended: ACL patellar tendon autograft, femur osteotomy Femoral catheter initial bolus: 20-30 mL 0.33% ropivacaine Femoral catheter infusion: 5 mL/h 0.2% ropivacaine No sciatic block unless unanticipated pain refractory to femoral block Category III (Severe) Procedure
Femoral nerve block
Sciatic nerve block
Most Invasive Category III (test for dorsiflexion before ablating sciatic nerve motor response) Total knee replacement Continuous femoral catheter Continuous sciatic catheter Initial bolus: Initial bolus: High tibial osteotomy 20-30 mL 0.33% ropivacaine 5-10 mL 0.2% ropivacaine Multiligament reconstruction Catheter dose: Catheter dose (postoperatively): (including PCL, LCL, MCL, POL) 5 mL/h 0.2% ropivacaine 5-20 mL 0.2% ropivacaine, then 3 mL/hF 0.2% ropivacaine Posterolateral corner reconstruction Moderately Invasive Category III ACL hamstring autograft Meniscal reconstruction Unicompartmental knee arthroplasty Less Invasive Category III Distal patella realignment
Continuous femoral catheter Initial bolus: 20 mL 0.2% ropivacaine Catheter dose: 5 mL/h 0.2% ropivacaine
Single-injection sciatic: 20 mL 0.33% ropivacaine
Single-injection femoral: 30 mL 0.33% ropivacaine
Single-injection sciatic: 20 mL 0.2-0.33% ropivacaine
Algorithm for the use of nerve block additives: If a catheter is to be used, clonidine is not routinely added If no catheter is used, clonidine is routinely recommended Regardless of catheter status, buprenorphine may be a very useful analgesic adjunct (as part of the catheter-bolus dose or single-injection dose). Buprenorphine dose should be restricted to a total of 150 m per adult patient to prevent nausea, vomiting, and pruritis associated (anecdotally) with higher doses. UPMC: University of Pittsburgh Medical Center; ACL: anterior cruciate ligament; PCL: posterior cruciate ligament; LCL: lateral collateral ligament; MCL: medial collateral ligament; POL: posterior oblique ligament.
tally in the groin, the femoral nerve becomes the saphenous nerve, which acts in a pure sensory capacity to innervate the medial leg and ankle. Thus the femoral nerve provides sensory innervation to the femur, anterior thigh, and medial leg and ankle, as well as motor innervation to the muscles responsible for a patellar contraction. Judging proximity to the femoral nerve depends on the motor component of the femoral nerve to produce a patellar twitch. The femoral nerve can be indirectly identified by means of its proximity to other landmarks. At a level 2 cm inferior to the inguinal ligament, the femoral nerve is 1 cm lateral to the femoral artery (Fig 1). This relationship is maintained for 3 to 5 cm distal to this point. Superficial to the nerve is the fascia iliaca, which gives rise to a small local contraction when stimulated. Deep to the femoral nerve is the iliopsoas muscle, which gives rise to a stronger local contraction when stimulated. The femoral nerve is close (medial) to the sartorious muscle, which presents as a recognizable twitch when stimulated. If the femoral artery is not palpable, a Doppler signal can easily identify this landmark, which can then be used to approximate the femoral nerve. One other anatomic “pearl” is that the location of the femoral nerve lies one-third of the distance from the pubic tubercle to the anterior superior iliac spine.
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Femoral Catheter Technique for Continuous Infusions Guidelines for placing indwelling catheters include patient positioning, marking the site of the femoral nerve, and using the correct needle trajectory. General positioning should consist of a patient in the supine position with the operator at a comfortable working level near the upper thigh. The site of the femoral nerve should be marked with an indelible marker. After cleansing the skin with alcohol, a 2 to 3 mL subcutaneous injection of local anesthetic should be placed, taking care to avoid blocking this superficial nerve. This will serve to both render the skin insensate and identify the site of the femoral nerve should the ink markings be erased. Please note that if the local skin or underlying tissue at the site of the planned femoral perineural catheter is not suitable (groin skin breakdown or infection, or previous vascular surgery involving the femoral artery), it may be prudent to use a posterior, psoas compartment lumbar plexus nerve block and perineural catheter instead. Skin preparation, needle insertion and trajectory, and nerve stimulator guidelines. With strict adherence to sterile technique, the area should then be cleansed and draped in a fashion so as to allow visualization or palpation of the patellar twitch. WILLIAMS ET AL
Fig 1. Landmarks for the femoral nerve block. The femoral artery (FA) is identified by palpation. The needle entry point for the femoral nerve block (indicated by the asterisk *) is usually 1 –1.5 cm lateral to the palpated femoral artery, and 3-4 cm caudad to the inguinal crease.
Trajectory of the needle is ⱕ30° with the bevel pointing cephalad, while the needle is directed parallel to the femoral artery. This is accomplished with the operator’s 3rd digit of the left hand resting on the femoral arterial pulse, while the right hand’s first and second digits guide the needle. Resting the ulnar surface of the right hand, more cephalad than the muscles being stimulated may help to stabilize the needle. While these hand positions are suitable for the start of the procedure, adjustments are often needed once the twitches have lessened to provide maximal stability for the injection of local anesthetic (if using a nonstimulating catheter) and the placement of the catheter. The nerve stimulator should be set at a current of 1.0 mA, as the 5- to 10-cm needle enters the skin. This current should provide both safety for the surrounding tissue as well as sufficient stimulus to evoke a twitch. Once the patellar twitch is evoked, the operator decreases the current while maximizing the twitch response continuously, by changing the position of the tip of the needle through slight rotation (while maintaining a cephalad trajectory), by minimal movements in the cephalad, caudad, medial, or lateral directions, or by advancing or withdrawing the needle. While the natural tendency for the operator may be to probe deeper, experience will demonstrate withdrawing the needle to a more superficial location is usually more successful in reproducing or enhancing the twitch response. If the evoked twitch is the medial twitch of the vastus medialis, then the introducer is likely too medial, and the operator should simply reposition the introducer needle tip 0.3 to 1 cm lateral (without exiting the skin). If a local twitch of fascia lata is generated, then the introducer is too shallow, and the operator should reposition the needle deeper. Once the current intensity is reduced to approximately 0.4 to 0.5 mA, with maintenance of the twitch, termination of the twitch response at 0.2 mA should be demonstrated. This will NERVE BLOCKS FOR OUTPATIENT KNEE SURGERY
help confirm (but not definitively) a peri-neural location (as opposed to an intraneural location), which is an endpoint warranting documentation. Twitches evoked in athletic patients may cause needle displacement. Patients with diabetes, or patients with peripheral neuropathy, may require a nerve stimulator pulse width greater than 0.3 ms (the limit of a standard peripheral nerve stimulator). After achieving the patellar twitch at an appropriate intensity, assuming a nonstimulating catheter is used, 20 to 40 mL of local anesthetic is incrementally injected (aspirating the syringe for heme every 5 mL of injection) while assessing neurological and hemodynamic status. Placing and securing the catheter. Finally, the catheter is placed and secured. The operator advances the catheter, with gentle pressure, 4 to 5 cm beyond the tip of the introducer. The bevel of the introducer should still be oriented cephalad. Risks of catheter knotting versus dislodgment should be evaluated by the operator when considering the catheter depth. Obese patients may require the catheter to be placed at a greater depth both to overcome the potential dislodgement by redundant soft tissue as well as to overcome the manual buttressing/compression of the same redundant tissue which may have occurred with the stimulation phase. After the catheter is threaded and the introducer nerve stimulator needle is removed, the area is finally prepared with a sterile adhesive liquid, after which thin sterile tape is laid (for example, in a crisscross fashion above the coiled catheter beneath); this adhesive dressing is followed by sterile transparent adhesive dressing. It may be wise to secure the edges of the sterile transparent dressing with an adhesive tape that includes imbedded zinc oxide, since patients discharged home will be discouraged from dressing changes until the time has come for catheter removal. Considerations of intraoperative thigh tourniquet use will require careful positioning of the catheter. Coiling the catheter be-
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Fig 2. Landmarks for the lumbar plexus continuous psoas compartment block, and for two approaches to the sciatic nerve block. For the lumbar plexus block (with landmark lines indicated in white), patient assumes a lateral decubitus position with surgical side up. The intercristal line (ICL) is drawn and crosses midline at the level of L4. Then a spinous process line (SPL) is drawn from approximately L3 to L5. A parallel line to the SPL is drawn cephalad originating from the posterior superior iliac spine (PSIS). Two-thirds of the distance from the SPL to the PSIS parallel line marks the entry point (green dot with white arrow directed at it) for the perpendicular needle entry of the nerve stimulator introducer needle. For the sciatic nerve blocks, the black markings on this figure are used. For the traditional gluteal approach to the sciatic nerve block, the most cephalad aspect of the greater trochanter (GT) is palpated. A line is drawn from there to the PSIS. Another line is drawn from the GT to the tip of the coccyx. The midpoint of the GT-PSIS line is bisected, with a perpendicular line drawn toward the GT-coccyx line. The skin insertion point for this approach to the sciatic nerve block is adjacent to the asterisk (*). Another approach can be considered, in which the groove between inferolateral edge of the gluteus maximus (GM) and the lateral edge of the long head of the biceps femoris (BF) is identified. The skin insertion point for this approach to the sciatic nerve block is in this groove, 3-4 cm caudad to the most caudad palpable portion of the gluteus maximus muscle (indicated by the symbol “#”). In our experience, this has served as a useful approximation of the skin entry point described by di Benedetto et al (CITE with superscript here), in which they draw a line from the GT to the ischial tuberosity, then from the mid-point of this line, a second line is drawn perpendicularly and extended 4 cm caudad, with the end of this perpendicular line (not shown in the figure) representing the entry point of the needle.
neath several sterile transparent adhesive dressings, while ensuring that the proximal end with the Luer connector is positioned away from the planned tourniquet location, is the final necessary step to placing and securing the femoral nerve catheter.
Lumbar Plexus Anatomy and Catheter Placement The lumbar plexus originates from ventral rami of lumbar nerve roots L2 to 4 and forms between the superficial and deep planes of the psoas muscle at the level 4th lumbar vertebral body. Moving distally, this plexus then forms the lateral femoral cutaneous (L2-3), femoral (L2-4), and obturator (L3-4) nerves. The lateral femoral cutaneous nerve provides sensory innervation to the anterior lateral and posterior medial thigh, while the femoral nerve provides sensory innervation from the anterior thigh and motor innervation to the quadriceps muscles, which produce a quadriceps twitch. The obturator nerve innervates hip adductors which adduct the leg and also carries sensory information from patches of the medial thigh. We endorse the psoas compartment lumbar plexus anatomic landmarks recently published by Capdevila and coworkers.17 In this article, computed tomography verification of the surface anatomic landmarks showed that the optimal needle entry
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point for the lumbar plexus block in the psoas compartment is somewhat more medial than originally described. The insertion point should occur on the intercristal line; the transverse process of L4 at the level of the lumbar plexus is 1 cm caudad to the intercristal line. A perpendicular line originating from the posterior superior iliac spine (PSIS) should be drawn to intersect with the intercristal line. Then, along the intercristal line originating from the spinous process, a mark should be made twothirds of the distance from the spinous process to the intersection point of the PSIS and intercristal lines (Fig 2). The 10-cm nerve stimulator introducer needle is inserted perpendicular to all planes, with the bevel pointing cephalad. After skin and subcutaneous fat, the needle then traverses the iliocostalis lumborum muscles and then the paravertebral muscles, both of which may produce a local contraction. These layers of needle passage occur within 6 to 7 cm of entry, typically. If the L4 transverse process is contacted, the needle is withdrawn by a fraction of a centimeter and is systematically “walked off” the cephalad aspect of the transverse process. If neither desired twitch nor transverse process is encountered (the average depth to achieve the desired quadriceps twitch response is 85 mm in men and 70 mm in women), the needle is withdrawn without WILLIAMS ET AL
Fig 3. Neurostimulation during perineural catheter insertion. For this sciatic nerve block procedure, the nerve-stimulating introducer needle was used to identify the sciatic nerve initially, via a clip-connecting wire carrying current from a peripheral nerve stimulator to the insulated needle. In this photo, the wire clip has been moved from the needle to the exposed stylet (indicated by the asterisk *) at the end at the proximal tip of the perineural catheter. Electrical current is then carried via the stylet to the distal tip of the catheter, guiding the operator’s insertion of the catheter through the nerve-finding needle, while twitch of the calf, ankle, and foot are observed. The equipment used is the Arrow ® StimuCathTM AB-05060 Continuous Nerve Block Set (Arrow International, Reading, PA).
exiting the skin and is systematically fanned from the initial entry point using small lateral increments, to try not to direct the needle medially (ie, toward the epidural space). Most commonly, the lumbar plexus can be identified within 2 cm of the L4 transverse process, once contacted. When placing the lumbar plexus needle, the operator seeks a quadriceps twitch (as opposed to an obturator twitch) since the quadriceps twitch is easier to identify when the patient is in the lateral position. The quadriceps twitch also confirms needle placement central to all of the nerves within the planes of the psoas compartment. The principles of catheter insertion once the desired twitch is identified follow the principles described for femoral perineural catheters above. It should be noted that the area surrounding the lumbar plexus is richly vascularized; thus, heme may be present in the incremental syringe aspirations up to 20% of the time.
This palpable margin of the gluteus maximus should be distinguished from the lateral margin of the vastus medialis, which lies a few centimeters laterally. Needle insertion for perineural catheter placement is typically perpendicular to all planes for traditional posterior sciatic (gluteal) approaches. In our experience with the subgluteal block, we have directed introducer needles cephalad with success, although diagrams by the author of the subgluteal approach use needles directed both cephalad and caudad. The principles of catheter insertion once the desired twitch is identified follows the principles described for femoral and lumbar plexus perineural catheters described above.
Placement of a Sciatic Nerve Catheter
Indications for Catheter Placement
The anatomic principles of sciatic nerve blocks using a traditional posterior gluteal approach (with landmarks shown in Fig 2) are well-outlined in textbooks and atlases. The needle is inserted typically perpendicular to all planes, like the lumbar plexus block above. A new subgluteal approach has emerged,18 which appears to confer less patient discomfort than traditional posterior gluteal approaches.19 The landmarks that we have found most helpful are (i) the lateral edge of the long head of the biceps femoris (medially), and (ii) the infero-medial edge of the gluteus maximus (laterally, as the gluteus maximus courses further inferolaterally toward its insertion on the proximal posterior femur).
Table 1 is a detailed algorithm that is used at the South Side Hospital division of the University of Pittsburgh Medical Center for our outpatients presenting for knee surgery. It should be noted that we have been using nerve block catheters for not quite one year at the time of this writing; our conversion to these catheters from the routine use of single-injection blocks was prompted by some surgeons requesting motor preservation. It should be emphasized that patient selection for catheter use is based largely on the criteria described earlier. In patients whom catheters are deemed inappropriate, the longest possible duration of single-injection is used. The surgeon commonly needs to be repeatedly reminded that motor preservation is
NERVE BLOCKS FOR OUTPATIENT KNEE SURGERY
Strategies and Indications for Outpatient Knee Surgery Catheter Placement, Confirmation, Dosing, and Management
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Fig 4. Tunneling the perineural catheter. After the perineural catheter is placed and its placement is confirmed by stimulation of the stylet, the introducer needle is carefully removed with special attention directed toward not accidentally removing or displacing the catheter simultaneously. Once the introducer needle is removed, the perineural catheter is further secured via subcutaneous tunneling. Routine intravenous catheters can be used for perineural catheter tunneling. In this photo of a femoral nerve block, a 14-gauge intravenous cannula is separated from its underlying needle. The needle (indicated by the asterisk [*]) has its tip passed through the original skin insertion site, and is passed laterally. Upon needle exit, the plastic cannula (the hub of which is indicated by the symbol [#]) is passed retrograde over the tunneled needle. The needle is then removed and the perineural catheter is passed from the distal tip of the plastic cannula back through the hub of the cannula. At this point, the plastic cannula is removed completely, ensuring that the perineural catheter is not displaced any more than is necessary to have a satisfactory subcutaneous tunnel for the perineural catheter. The equipment used is the Arrow ® StimuCathTM AB-05060 Continuous Nerve Block Set (Arrow International, Reading, PA).
meaningless if pain precludes meaningful advancement of physical therapy objectives. As far as we are aware, there are no data indicating that motor sparing in a peripheral nerve block, when all else is equal with respect to analgesic duration, has any effect on long-term patient outcome as far as ambulation and knee function. We preferentially use spinal anesthesia as the definitive intraoperative anesthetic, currently using hyperbaric ipsilateral solutions of procaine or bupivacaine, with doses titrated to anticipated surgical duration. The typical procaine dose is 50 to 70 mg, and the typical bupivacaine dose is 9 to 12 mg. It should be emphasized that we use the lateral decubitus position for these spinals, with the aperture of the pencil-point needle directed to the decubitus side, to maximize anesthesia of the surgical knee and minimize anesthesia in the nonsurgical knee. When compared with our previous reports in which we performed spinal anesthesia with patients in the sitting position using isobaric procaine, mepivacaine, and bupivacaine,5,6 we have found anecdotally that the ipsilateral hyperbaric spinal anesthesia strategy has significantly reduced time-to-discharge by nearly half. Combining this laterality/baricity principle with the suggestion by Mulroy and coworkers20 that patients need not void as a mandate before discharge after short-acting neuraxial anesthesia has the potential to significantly reduce discharge times. The block categories described in Table 1 were based on
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descriptive data detailed in a recent article describing our experiences with outpatients from 1995 to 1999.7 This article retrospectively categorized surgical procedures in which no blocks were needed versus procedures when femoral with or without sciatic nerve blocks were needed (a two-tier system). However, we clinically use a three-category system for predicting pain severity based on nerve distributions in which there is significant surgical trespass. For simplicity, we delineate using categories I (“mild”), II (“moderate”), and III (“severe”). Category I consists of procedures that are truly “minimally invasive,” consisting of arthroscopic debridement, meniscectomy, and small meniscal repairs. Category II consists of procedures in which the most significant postoperative pain is restricted to the femoral nerve distribution. We now have two subcategories of Category II, distinguished by the adequacy of a single-injection femoral nerve block versus the apparent necessity of a femoral nerve catheter. Table 1 delineates the procedures in which the need for the perineural catheter is apparent, based on internal data and clinical anecdotes to date. Category III is quite complex. These procedures typically require nerve block analgesia in the femoral and sciatic nerve distributions. The complexity in Category III lies in the anesthesiologist’s predictions of the sufficiency of single-injection femoral and sciatic nerve blocks versus the potential benefit of adding femoral with or without sciatic nerve catheters. Table 1 WILLIAMS ET AL
Fig 5. Testing the perineural catheter after tunneling with electrostimulation. In this figure, the asterisk (*) indicates the original skin entry point for the nerve finding needle, and the symbol “#” indicates the perineural catheter exit site after subcutaneous tunneling. At this point, the snap-top luer connector (indicated by the arrow) is connected to the proximal tip of the perineural catheter. The clip at the end of the wire (connected to the peripheral nerve stimulator) is now connected to the metal extension from the snap connector, which carries electrical current through the insulated perineural catheter to the distal catheter tip. Using this feature, the perineural catheter can be confirmed for placement before dosing takes place. On occasion, the absence of twitch at this point is commonly resolved by slowly withdrawing the catheter a millimeter at a time, until the desired twitch is produced once again. If no twitch is produced, however, the procedure would need to be repeated. The equipment used is the Arrow ® StimuCathTM AB-05060 Continuous Nerve Block Set (Arrow International, Reading, PA).
shows our current clinical impression of surgical procedure subtypes warranting the incremental levels of postoperative analgesia effort required.
Confirming Perineural Catheter Placement The use of perineural catheters in patients to be discharged home can be complicated, especially when verifying catheter placement before discharge. There are two immediately apparent means of verifying catheter placement. First, a test dose of local anesthetic can be injected through the catheter, and if anesthesia or analgesia is produced, then the catheter is assumed to be placed correctly. The inherent disadvantage of this approach is that the test dose used which would verify catheter placement may also produce a definitive motor block, which surgeons may wish to avoid. Another disadvantage is that the test dose volume (if the test dose is unsuccessful) may pose restrictions on subsequent local anesthetic dosing should the block or catheter be re-attempted, not to mention pose a potential restriction in nerve finding (previous twitch ablation, or tissue plane distortion by the previously injected local anesthetic volume). The other method of testing catheter placement is by electrostimulation through the inserted perineural catheter. This process has been described in detail for brachial plexus blocks for
NERVE BLOCKS FOR OUTPATIENT KNEE SURGERY
shoulder surgery by Boezaart.21 The catheter used for this process must include an imbedded wire which can conduct electrical current from the catheter origin (commonly via an electrical adapter incorporated to the Luer-lock snap connector) through the insulated catheter, to the catheter tip. The operator can stimulate such a catheter during catheter insertion through the nerve-finding needle (Fig 3), after removal of the nervefinding needle, after catheter tunneling (Figs 4 and 5), and after dressing, to confirm the absence of displacement at every step of inserting and securing the catheter. With stimulating catheters, boluses with local anesthetics should occur through the confirmed catheter, and not the nerve-finding needle, to maximize the benefits of using this specialty equipment. Pending studies which compare the success rates of perineural catheterization when using stimulating versus nonstimulating catheters, anesthesiologists should consider the costs of the equipment used for catheter placement, planned infusion pump device for outpatients, and the hidden costs of failure of the technique should the patient only have a nerve block duration of 24 hours or less with a catheter and infusion pump in place. Depending on how this comparative research ultimately pans out with respect to success rates, patients deserve the best chance to have the procedure completed successfully the first
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time, with minimal risk for return hospital visits with uncontrolled pain.
Dosing and Management of Perineural Catheters We recommend the use of infusion pumps in which a basal infusion occurs (eg, 5 mL/h) with the potential for a patientcontrolled bolus (eg, 5 mL bolus with a 60-minute lockout). Patients should be definitively instructed on how and when to clamp the infusion pump tubing (eg, for an elastomeric pump), or to power the device off (eg, with an electronic pump) should the nerve distribution in question accumulate a motor block effect and guidelines should be provided (return of motor function and onset of slight pain) as to when to resume the infusion.
Conclusions In outpatient knee surgery, perineural catheter techniques are an important advance to further ensure a comfortable same-day discharge after procedures typically associated with significant pain, procedures often justifying a planned or unplanned hospital admission. The ability to titrate local anesthetic doses to provide sensory-specific analgesia with minimal motor block is a significant benefit of the perineural catheter technique. Research is needed to determine (i) perineural catheter success rates when stimulating versus nonstimulating catheters are used; (ii) long-term benefits of sensory-specific analgesia when compared with blocks which transiently ablate all motor function; and (iii) optimal analgesic duration. In addition, epidemiologic studies of same-day-discharged patients are needed to determine success rates and complication rates (patient falls, infections, persistent paresthesiae, or other neurologic sequelae) related to the use of long-duration single-injection nerve blocks and perineural catheters.
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