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Update on peripheral regional analgesia
Update on Peripheral Regional Analgesia Sugantha Ganapathy
Introduction of continuous regional analgesia has resulted in improved quality of pain relief to patients and reduced the chances of unplanned admission in ambulatory surgical patients. Ambulatory patient controlled regional analgesia at home has further extended the use of regional analgesia beyond the hospital setting. The challenges posed by such ventures has resulted in development of newer techniques to reduce secondary catheter failures as well as adjuvants to local anesthesia that improve success with such novel modalities of pain relief. These include stimulating catheters, disposable infusion devices with patient controlled modalities and use of drugs such as ketamine and long acting local anesthetic formulations. There is further data available with regards to the safety of these techniques. © 2003 Elsevier Inc. All rights reserved.
ublic awareness of the use of peripheral nerve blocks for postoperative analgesia has tremendously increased since Time magazine published the picture of Dr. Greengrass performing paravertebral block on a patient for breast cancer surgery. Recent studies documenting the efficacy of multimodal analgesia for improving patient outcome1-3 have further resulted in an explosion of studies evaluating the use of peripheral nerve blocks for postoperative analgesia beyond the hospital environment. The development of infusion pumps, which are light and disposable, newer needles, and stimulating catheters, the use of imaging and ultrasound, and large scale population based studies have opened a Pandora’s box of what can be accomplished with regional techniques. As far as the consumers are concerned, they do not want to be sore, sick, and sleepy after their surgery, and do not wish to lose days of productivity because of their surgery. How has the regional anesthesia community worked towards accomplishing this goal? I will discuss some newer techniques with regional blocks, adjuvants to extend the duration of analgesia following single injection regional blocks, techniques introduced to improve success with catheters, outcomes with regional analgesia, and newer drugs on the horizon for use in regional analgesia. This article will deal with only peripheral nerve blocks.
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From the Department of Anesthesiology, Duke University Medical Center, Durham, NC. Address reprint requests to Sugantha Ganapathy, FRCA, FRCPC, Department of Anesthesiology, Duke University Medical Center, Box 3094, 2500 North Pavilion, Durham, NC 27710. Email: ganap001@notes. duke.edu © 2003 Elsevier Inc. All rights reserved. 1084-208X/03/0703-0022$30.00/0 doi:10.1053/S1084-208X(03)00032-6
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Novel Techniques Upper Limb Interscalene Block Although we have been using continuous interscalene blocks at the root level, the classic technique is associated with 100% diaphragmatic paresis, resulting in reduction in tidal volume and functional vital capacity that may preclude this excellent modality of analgesia from being used in patients with moderate or severe respiratory compromise.4-6 Boezaart and coworkers have described a technique of approaching the brachial plexus from the back as a cervical paravertebral block using the loss of resistance and a stimulating catheter, and they document a significantly lower incidence (ie, 30%) of diaphragmatic paresis.7 This technique may be particularly useful for catheterization in patients in whom nerve stimulation and the muscle twitches can cause a lot of pain, such as trauma and fracture. It needs further evaluation to quantify the risks associated with the posterior approach, such as epidural spread and intravascular injections, which intuitively may be higher. The investigators reiterate that the area of shoulder supplied by the cervical plexus will not be anesthetized by this technique, and, therefore, additional superficial cervical plexus blocks should be combined with this technique when used for shoulder surgery. Suprascapular nerve blocks have been used for postoperative analgesia following arthroscopic shoulder surgery8 with no complications, but do we need to perform it in addition to an interscalene block? In a recent, prospective randomized placebo controlled trial, Neal and coworkers note that addition of suprascapular nerve to interscalene block prolongs analgesia (594 ⫾ 369 versus 375 ⫾ 273 minutes) but does not improve outcome.9
Supraclavicular Blocks Supraclavicular nerve blocks are performed at the level of the trunks compactly situated posterosuperior to the subclavian artery and, thus, result in a high success rate with blocking all the components of the brachial plexus. Unfortunately, the conventional approach to supraclavicular block does not facilitate easy catheterization in this area. The paravascular technique by Moorthy and colleagues allows easier catheterization.10 PhamDang and coworkers have described an intersternocleidomastoid approach that facilitates catheterization.11 This technique has also resulted in a lower incidence of diaphragm paresis.12 Neither of these techniques have been adequately exploited,
Techniques in Regional Anesthesia and Pain Management, Vol 7, No 3 (July), 2003: pp 148-154
particularly for ambulatory surgical patients for postoperative analgesia.
Sciatic Blocks These blocks are commonly used for analgesia following foot and ankle surgery, knee and hip arthroplasty, ligament repair around the knee joint, and osteotomy. The majority of the reports involve the use of the classic technique (Labatt) of sciatic blockade at the gluteal region. Blockade at the popliteal fossa has been beneficial for foot and ankle surgery but has a higher incidence of problems with catheters and incomplete blocks. Single injection blocks have been reviewed recently by Singelyn and coworkers.13 The main advantage of the popliteal sciatic block is the preservation of hamstring function, allowing the ease of ambulation on crutches following surgery. A lateral approach at this location has been evaluated and has the advantage that the catheters can be inserted for ongoing analgesia with the patient in the supine position.14-16 di Benedetto and coworkers have described an alternate technique of the subgluteal approach to the sciatic nerve, which is performed with the patient in the Sim position.17 They compared the technique with the popliteal as well as classic sciatic blocks and found the subgluteal approach to be less painful for the patients during insertion. As the block is performed in the intermuscular plane, intuitively, catheterization for extended analgesia should be easier, but this needs to be prospectively evaluated. Naux and coworkers have described a lateral approach to the sciatic nerve at the mid femoral region.18 Because the needle comes at a right angle to the nerve, intuitively, catheterization might be more difficult, but this needs to be evaluated. The advantage of the latter 2 approaches is that the sciatic nerve has not separated and diverged as tibial and peroneal at this location, although the fibers may already be oriented separately. This process may reduce the chances of failure of block with tibial or peroneal component seen sometimes with popliteal blocks. Sciatic nerve block is combined with femoral or lumbar plexus block for surgery, but ambulation with a weak quadriceps and hamstring mechanisms may pose problems. Often, we do femoral block with a short-acting mepivacaine combined with a sciatic catheter for postoperative pain for foot and ankle surgery. If there is a medial incision over the saphenous distribution that often occurs with ankle fusion or bimalleolar fracture, either wound infiltration with long acting local anesthetic or a subsartorial saphenous block19 with or without the catheter may be added for extension of analgesia in the medial ankle without producing extended quadriceps weakness. Williams and coworkers have documented a 2.5-fold reduction in unplanned admission using femoral and sciatic block or femoral block alone following invasive ambulatory knee surgery.20 Currently, we do not send patients home with combined catheters, but that could certainly be done in patients admitted to hospital. With combined catheters, one has to consider the total dose of local anesthetic, potential local anesthetic toxicity, as well as potential for primary and secondary failures with each of those catheters. Patient-controlled regional anesthesia (PCRA) with double catheters has not been tried for obvious reasons.
Lumbar Plexus Blocks It has been well documented by several investigators that femoral 3-in-1 block does not predictably get all the 3 nerves it is intended to get. The obturator nerve is often missed with this UPDATE ON PERIPHERAL REGIONAL ANALGESIA
technique, resulting in inadequate analgesia postoperatively. McNamee and coworkers looked at the role of obturator block in analgesia following knee replacements and noted that additional obturator block improves analgesia.21 The posterior approach to the lumbar plexus anesthetizes the obturator nerve more frequently, thus obviating the need for additional obturator block. The catheters can also be fixed more securely in the back, with less chances of leakage and infection. Unfortunately, there are some concerns with the use of posterior lumbar plexus blocks. In their review on major complications of regional anesthesia in France, Auroy and coworkers have documented a high incidence of major complications (80 of 10,000) and cardiac arrest (1 in 400) following posterior lumbar plexus block.22 This block has also resulted in renal injury, accidental intra-abdominal catheterization, and psoas hematoma, particularly in patients who were anticoagulated.23-26 Although the latter 3 are isolated episodes, one has to be cognizant of these potential complications. Landmarks using a more medial approach may result in a higher incidence of epidural spread, which may cause hypotension and, perhaps, delay discharge in the ambulatory setting. Because of their location, femoral catheters are associated with more episodes of kinking and leakage, apart from a high incidence of bacterial colonization. Cuvillon and coworkers report incidences of 57% colonization and 1.5% bacteremia.27 Because the knee joint has a variable supply from femoral, obturator and sciatic nerves, the quality of analgesia with isolated lumbar plexus block can be variable. Many patients have excellent analgesia following knee surgery just with lumbar plexus block alone, yet a small proportion has significant pain in the posterior knee. This posterior pain can often be managed beyond the first postoperative day with oral opioids and cyclooxygenase-2 inhibitors. Although the addition of sciatic block to lumbar plexus block for analgesia following knee arthroplasty has been of questionable value, for major knee surgery, we run lumbar plexus and sciatic infusions for the initial 24 hours. This process significantly reduces opioid requirements, and postoperative nausea and vomiting (PONV). The sciatic catheter is removed the morning after surgery after a 10 to 15-mL bolus with long acting local anesthetic, and only the lumbar plexus infusion is continued for 48 to 72 hours. This process provides excellent patient satisfaction and good analgesia.
Adjuvants Single injection blocks provide analgesia on an average for 12 to 14 hours. A number of patients may not be suitable for continuous ambulatory patient-controlled regional analgesia due to their lack of proximity to a health facility and/or appropriate home support. If we could provide these patients with an analgesic regime that covers the pain well during the first 24 hours, they will be able to manage subsequent days of pain with oral analgesics. There are several drugs that have been tried to improve analgesia following single injection regional blocks. Although there is evidence of opioid receptors in the peripheral nerves, the addition of opioids in the peripheral nerve blocks have resulted in variable efficacy. In fact, the addition of sufentanil has increased the incidence of hypoxemia and PONV.28 Murphy and coworkers have reviewed this topic systematically and note that 6 of 10 studies showed evidence of improved analgesia, and only 4 of them had a systemic narcotic control
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group.29 The investigators conclude that the evidence of opioid efficacy in peripheral nerve blocks is weak. Contrary to the opioids, clonidine, an ␣-2 agonist that has C-fiber blocking potential when added in low doses (0.5 to 1 g/kg) to the peripheral nerve blocks, significantly prolongs analgesia but loses additional efficacy at higher doses.30-32 The higher doses may also be associated with undesirable side effects, such as sedation and hemodynamic changes.31,33,34 Although this might be acceptable in the inpatient setting, it might not be prudent in the ambulatory setting. Other additives, such as neostigmine, have not been useful for extending the analgesia following intravenous regional anesthesia (IVRA) or nerve blocks. Ketamine added to small dose interscalene block has provided extended analgesia.35 Ketorolac added to IVRA has also produced extended analgesia.
Ambulatory Regional Analgesia By far, the most progress regarding postoperative analgesia has been made in the field of ambulatory anesthesia. This area has been extensively reviewed by Klein.36 Orthopedic patients perceive the most significant pain following ambulatory surgery that adversely impacts patient outcome.37,38 Klein and coworkers had reported on the safety and efficacy of regional anesthesia in the ambulatory setting, with patients discharged home with ongoing sensory and motor block providing extended analgesia.39 Grant and colleagues reported their experience with 228 patients in an ambulatory surgery center where patients received an infusion via the block catheter in a short stay facility for 24 hours.40 They bolused the catheter before discharge and removed the catheters. Their initial block success was 94%. Their secondary catheter failure was 10%. They managed to reduce the incidence of postoperative nausea to an impressive 1.7%. Since the introduction of elastomeric41 as well as lightweight electronic pumps, patients are discharged home with an ongoing local anesthetic infusion via the peripheral nerve catheters. Ilfeld and coworkers42,43, and Enneking and Ilfeld44 have documented excellent analgesia with this technique using an electronic pump, and report excellent pain relief, reduced nausea, and improved sleep pattern during the postoperative period following orthopedic surgery. Function of different pumps regarding the accuracy of delivery has been evaluated by Ilfeld45 as well as Capdevila46 and colleagues. Capdevila and coworkers note that both class of pumps perform acceptably. The elastomeric pumps as well as some of the newer electronic pumps (Fig 1) are disposable and, thus, may be used in patients at a distance from the hospital. The elastomeric pumps usually have a fixed reservoir and fixed delivery rate. Currently, there are some elastomeric pumps that also provide the facility of patient administered boluses. There were instances when the entire contents of the bulb were delivered into the patient when the clamp was opened and closed to deliver the set bolus. The “Rawal pump” has a built in valve that is activated by the patient to provide a fixed bolus, so that accidental discharge of the entire contents of the bulb is avoided. The rate of delivery of these bulbs can depend on storage temperature, vehicle for local anesthetic, and distal occlusion pressure, but technically, they are easy to use. The electronic pumps are significantly more expensive, but they allow a larger reservoir of local anesthetic and variable bolus rates. The Sorensen microject pump (Fig 1) and similar devices are reusable. With the microject
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pump, the maximum rate per hour is 9.9 ml, and the maximum bolus dose is 2 ml, which precludes higher doses with boluses. Although this may be acceptable for upper limb blocks, lumbar plexus and femoral blocks being compartment blocks sometimes require higher bolus doses. Currently in the hospital setting, we allow nurse-administered boluses of 10 ml every 6 hourly when required. Such a paradigm is currently impossible with the ambulatory PCRA. The future might have a device with a red button for the larger bolus and a green button for the smaller bolus set to lock out differentially with a predetermined maximum dose per 4-hour period lock out. Our experience suggests that it is rare that patients require the larger boluses beyond the first 23 hours. Singelyn and coworkers used 0.125% bupivacaine, with clonidine 1 g/mL and sufentanil 0.1 g/mL, via a femoral nerve sheath catheter as a continuous infusion at 10 mL/h or as PCA boluses only 10 mL/h, or as PCA boluses 5 mL per 30 minute.47 Pain scores at rest and supplemental analgesia were comparable in the 3 groups. At 48 hours, pain relief on movement was significantly better associated with a significant reduction in the bupivacaine consumption in the 2 bolus groups compared with the continuous infusion group. Side effects were comparable in the 3 groups. Satisfaction scores were significantly higher in the 5 mL bolus group than in the other groups. The investigators concluded that PCRA techniques reduce the local anesthetic consumption without compromise in patient satisfaction or pain scores. At our institution, we run a small dose of basal infusion and allow the patient to self-administer 2 to 4-mL boluses every 20 minutes as needed. The dosages are adjusted for patient size and the number of catheters having an infusion. If patients receive double catheter infusions, one of them will be a low dose continuous infusion, such as the sciatic for knee surgery and the second catheter will be set for PCRA. Patients receiving double catheter infusions during the first 23 hours have one of them removed after a 10 to 15-mL bolus the morning after surgery, depending on the site of surgery. The removal process is used to educate the home caregiver for removing the second catheter at home after 48 hours. All patients receive verbal and written instructions, and the staff is available 24 hours a day for troubleshooting. Patients do not like a weak, heavy limb that is difficult to manage during the postoperative period. More studies are required to evaluate the optimum concentration and dosing with continuous regional analgesia. Borgeat and coworkers compared 0.2% ropivacaine with 0.15% bupivacaine and note that bupivacaine resulted in more significant hand motor block.48 Although they have not used an equipotent dose, the fact that the ropivacaine group had very little motor block makes it a drug of choice. Whether a lower concentration, larger volume is better is currently unknown. There are no data on levobupivacaine for this indication. There are several important details that one needs to pay attention to regarding sending patients home with regional block infusions. Patient selection, availability of a chaperone, willingness and capacity to use the simple equipment, proximity to a health care facility, written as well as verbal education, and availability of staff 24 hours a day and 7 days a week for troubleshooting are very important. This modality has reduced the need for hospital admissions in a number of cases. It also significantly reduces the opioid requirements, reduces postoperative nausea and vomiting, and results in excellent patient SUGANTHA GANAPATHY
Fig 1. Infusion devices for ambulatory regional analgesia. 1. McKinnnley pump; 2. Sorensen microproject pumps; 3. Stryker pain pump 2, with 250 or 500 mL reservoir.
satisfaction. This modality has not only been used for postoperative pain but also to facilitate physiotherapy and for complex regional pain syndrome (personal unpublished data). Although the patients are sent home with ongoing motor sensory block, our experience reveals that with appropriate instructions, the patients protect their numb, weak limb. We usually make 1 to 2 telephone calls daily to ensure safe monitoring during the infusion. The removal of catheter should ideally be done after the block wears off so that patients may stop pulling on the catheter if they should perceive any pain. Although that is not our practice, preliminary data from the Duke Ambulatory Surgical Center (ASC) database reveal that persistent neurologic deficits UPDATE ON PERIPHERAL REGIONAL ANALGESIA
in this group are similar to the ones receiving single injection blocks.
Techniques to Improve Success Rates A number of investigators have used multiple stimulation techniques and have shown that it improves success with the initial block as well as reduces the dose of local anesthetic required for the block.49,50 Although the investigators claim that it does not lead to increased neurologic injury (1.7%), with the current information available on the conductive properties at the needle tip with small amounts of ionic solutions delivered near the
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Fig 2. Tunneled stimulating catheter. Lower arrow indicates needle entry site, and upper arrow shows tunneled exit of the catheter. The Pajunk stimulating assembly with the catheter (right panel).
nerve, the use of multiple stimulation techniques may not be for the beginner regionalist. Where individual nerves are separated from each other, such as in the mid humeral or infraclavicular location, this technique may offer selective catheterization of the nerve supplying the operative site for postoperative analge-
sia, which may result in reduced local anesthetic doses. This concept needs further evaluation. Stimulating catheters have been introduced recently into the market (Arrow International, Reading PA and Pajunk GmbH, Geisingen, Germany) (Figs 2 and 3). As the initial dose is
Fig 3. Arrow stimulating catheter assembly. Note the stimulating metal tip on the catheter and the attachment on the blue connector to facilitate stimulation of the catheter after the stylet is removed.
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SUGANTHA GANAPATHY
delivered through the catheter, if one is able to establish the block with nominal doses, it may signify appropriate location of the catheter. The stimulating properties of the Pajunk catheter are slightly different from the needle because the gold tip requires a higher current strength to maintain the stimulus (Fig 2). The catheter is soft and flexible. The prototypical catheters had a filament at the syringe end that made tunneling cumbersome. The Arrow catheter has similar stimulating qualities to the needle but has a rather rigid stylet and large (17 G), standard length Tuohy needle to initiate the block. A short needle has recently been introduced for the brachial plexus blocks. There is a learning curve to using these catheters, and clinicians should use the workshops, such as the RASCI (University of Iowa), to familiarize themselves with the use of these catheters. In an observational study, Pham-Dang and coworkers, using the Pajunk catheters, note that with upper limb catheters, the lack of stimulation signified misplaced catheter, while in the lower limb, one may not stimulate with the catheter but may still be able to establish the block via the catheter.51 Unfortunately, some methodological errors make it difficult to interpret their data. These investigators injected saline before advancing the catheter, which could have altered the stimulating environment with dispersion of current. Secondly, they did not advance the catheter while stimulating, which is a fatal flaw in their technique.52 There are no prospective randomized trials to document the safety and success rates with these catheters. Intuitively, these catheters should reduce secondary failure rates if the block was initiated by injecting the anesthetic via the catheters and they are fixed appropriately. Klein and coworkers reported on the cyanoacrylate glue for fixing these catheters.53 Subcutaneous tunneling (Fig 2) may not only allow the catheters to be fixed well but may also prevent leakage, which is the most common cause for the catheters to become loose and dislodged or kinked. The second technique that may reduce secondary catheter failure is the use of ultrasound to position the catheters in the appropriate location. A number of studies54-58 have examined the success of blocks using ultrasound, but there are no prospective trials researching secondary catheter failures. There are no prospective trials evaluating either of these techniques.
Outcomes Nielsen and Steele have recently reviewed outcomes after regional analgesia.59 Studies have documented reduction in unplanned admission, improved patient satisfaction, reduction in PONV, and improved sleep. The quality of life improvement and stress response to surgery, and reduction in cognitive dysfunction need prospective evaluation with regional analgesia.
Pharmacology for the Future Long acting local anesthetic with microsphere laden bupivacaine underwent early clinical trials and have been withdrawn due to prolonged conduction block with these formulations in animals.60 Butamben, an ester local anesthetic used in animal experiments, has been documented to produce prolonged sensory block without motor block lasting more than 3 weeks.61 IQB-9302, an amide local anesthetic, has produced sensory block lasting 30% longer than bupivacaine.62 These are exciting developments in regional analgesia. Whether they will replace continuous catheter regional analgesia will be determined by UPDATE ON PERIPHERAL REGIONAL ANALGESIA
their safety. For now, the art of pain management with regional techniques is undergoing the artist’s final touch for perfection.
References 1. Jin F, Chung F: Multimodal analgesia for postoperative pain control. J Clin Anesth 13:524-539, 2001 2. Katz J, Jackson M, Kavanagh BP, et al: Acute pain after thoracic surgery predicts long-term post-thoracotomy pain. Clin J Pain 12: 50-55, 1996 3. Williams BA, Kentor ML: Making an ambulatory surgery centre suitable for regional anaesthesia. Best Pract Res Clin Anaesthesiol 16:175-194, 2002 4. Urmey WF, Talts KH, Sharrock NE: One hundred percent incidence of hemi diaphragmatic paresis associated with interscalene brachial plexus anesthesia as diagnosed by ultrasonography. Anesth Analg 72:498-503, 1991 5. Urmey WF, Gloeggler PJ: Pulmonary function changes during interscalene brachial plexus block: Effects of decreasing local anesthetic injection volume. Reg Anesth 18:244-249, 1993 6. Bennani SE, Vandenabele-Teneur F, Nyarwaya JB, et al: An attempt to prevent spread of local anaesthetic to the phrenic nerve by compression above the injection site during the interscalene brachial plexus block. Eur J Anaesthesiol 15:453-456, 1998 7. Boezaart AP, de Beer JF, du Toit C, et al: A new technique of continuous interscalene nerve block. Can J Anaesth 46:275-281, 1999 8. Ritchie E, Tong D, Chung F, et al: Suprascapular nerve block for postoperative pain relief in arthroscopic shoulder surgery: A new modality? Anesth Analg 84:1306-1312, 1997 9. Neal JM, McDonald SB, Larkin KL, et al: Suprascapular nerve block prolongs analgesia after nonarthroscopic shoulder surgery but does not improve outcomes. Anesth Analg 96:982-986, 2003 10. Moorthy SS, Schmidt SI, Dierdorf SF, et al: A supraclavicular lateral paravascular approach for brachial plexus regional anesthesia. Anesth Analg 72:241-244, 1991 11. Pham-Dang C, Gunst JP, Gouin F, et al: A novel supraclavicular approach to brachial plexus block. Anesth Analg 85:111-116, 1997 12. Petitfaux F, Pham-Dang C, Dupas B, et al: Diaphragmatic excursion after inter-sternocleidomastoid block depending on the site of the injection. Annales Francaises d Anesthesie et de Reanimation 19: 517-522, 2000 13. Singelyn FJ, Aye F, Gouverneur JM: Continuous popliteal sciatic nerve block: An original technique to provide postoperative analgesia after foot surgery. Anesth Analg 84:383-386, 1997 14. Singelyn FJ: Single-injection applications for foot and ankle surgery. Best Pract Res Clin Anaesthesiol 16:247-254, 2002 15. Zetlaoui P, Bouaziz H: Lateral approach to the sciatic nerve in the popliteal fossa. Anesth Analg 87:79-82, 1998 16. Hadzic A, Vloka J: A comparison of the posterior versus lateral approaches to the block of the sciatic nerve in the popliteal fossa. Anesthesiology 88:1480-1486, 1998 17. di Benedetto P, Casati A, Bertini L, et al: 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 18. Naux E, Pham-Dang C, Petitfaux F, et alSciatic nerve blockA new lateral mediofemoral approachThe value of its combination with a “3 in 1” block for invasive surgery of the knee. Annales Francaises d Anesthesie et de Reanimation192000915 19. Mansour NY: Sub-sartorial saphenous nerve block with the aid of nerve stimulator. Reg Anesth 18:266-268, 1993 20. Williams BA, Kentor ML, Vaght MT, et al: Femoral sciatic blocks for complex outpatient knee surgery are associated with less postoperative pain before same day discharge. Anesthesiology 98:12061213, 2003 21. McNamee DA, Parks L, Milligan KR: Postoperative analgesia following total knee replacement: An evaluation of the addition of obturator nerve block to combined femoral and sciatic nerve block. Acta Anesthesiol Scand 46:1-4, 2002 22. Auroy Y, Benhamou D, Bargues L, et al: Major complications of regional anesthesia in France: The SOS Regional Anesthesia Hotline Service. Anesthesiology 97:1274-1280, 2002
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23. Aida S, Takahashi H, Shimoji K: Renal subcapsular hematoma after lumbar plexus block. Anesthesiology 84:452-455, 1996 24. Capdevila X, Macaire P, Dadure C, et al: Continuous psoas compartment block for postoperative analgesia after total hip arthroplasty: New landmarks, technical guidelines, and clinical evaluation. Anesth Analg 94:1606-1613, 2002 25. Klein SM, D’Ercole F, Greengrass RA, et al: Enoxaparin associated with psoas hematoma and lumbar plexopathy after lumbar plexus block. Anesthesiology 87:1576-1579, 1997 26. Weller RS, Gerancher JC, Crews JC, et al: Extensive retroperitoneal hematoma without neurological deficit in two patients who underwent lumbar plexus block and were later anticoagulated. Anesthesiology 98:581-585, 2003 27. Cuvillon P, Ripart J, Lalourcey L, et al: The continuous femoral nerve block catheter for postoperative analgesia: Bacterial colonization, infectious rate and adverse events. Anesth Analg 93:1045-1049, 2001 28. Bouaziz H, Kinirons BP, Macalou D, et al: Sufentanil does not prolong the duration of analgesia in a mepivacaine brachial plexus block: A dose response study. Anesth Analg 90:383-387, 2000 29. Murphy DB, McCartney CJL, Chan VWS: Novel analgesic adjuncts for brachila plexus blocks: A systematic review. Anesth Analg 90: 1122-1128, 2000 30. Ishander H, Guillaume E, Dixmerias F, et al: The enhancement of sensory blockade by clonidine selectively added to mepivacaine after midhumeral block. Anesth Analg 93:771-775, 2001 31. Casati A, Magistris L, Fanelli G, et al: Small dose clonidine prolongs postoperative analgesia after sciatic-femoral nerve block with 0.75% ropivacaine for foot surgery. Anesth Analg 91:388-392, 2000 32. Reuben S, Steinberg R, Klatt J, et al: Intravenous regional anesthesia using lidocaine and clonidine. Anesthesiology 91:654-660, 1999 33. Culebras X, Van Gessel E, Hoffmyer P, et al: Clonidine combined with long acting local anesthetic does not prolong postoperative analgesia after brachial plexus block but does induce hemodynamic changes. Anesth Analg 92:199-204, 2001 34. Reinhart D, Wang W, Stagg K, et al: Postoperative analgesia after peripheral nerve block for podiatric surgery: Clinical efficacy and chemical stability of lidocaine alone versus lidocaine plus clonidine. Anesth Analg 83:760-765, 1996 35. McCartney CJ, Chan VWS, Sunandaji L , et al: Small dose ketamine 0.5 mg/Kg produces a peripheral preventive analgesic effect when added to interscalene block for major shoulder surgery. ASRA A4, 2003 (abstr) 36. Klein S: Regional Anesthesia in ambulatory surgical patients. Best Pract Res Clin Anesthesiol 16:2, 2002 37. Chung F, Ritchie E, Su J: Postoperative pain in ambulatory surgery. Anesth Analg 85:808-816, 1997 38. Beauregard L, Pomp A, Choiniere M: Severity and impact of pain after day surgery. Can J Anaesth 45:304-311, 1998 39. Klein SM, Nielsen KC, Greengrass RA, et al: Ambulatory discharge after long acting peripheral nerve blockade: 2382 blocks with bupivacaine. Anesth Analg 94:65-70, 2002 40. Grant SA, Nielsen KC, Greengrass RA, et al: Continuous peripheral nerve block for ambulatory surgery. Reg Anesth Pain Med 26:209214, 2001 41. Ganapathy S, Amendola A, Litchfield R, et al: Elastomeric pumps for ambulatory patient controlled regional analgesia. Can J Anesth 47: 897-902, 2000 42. Ilfeld BM, Morey TE, Wright TW, et al: Continuous interscalene brachial plexus block for postoperative pain control at home: A randomized, double-blinded, placebo-controlled study. Anesth Analg 96:1089-1095, 2003
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43. Ilfeld BM, Morey TE, Wang RD, et al: Continuous popliteal sciatic nerve block for postoperative pain control at home: A randomized, double-blinded, placebo-controlled study. Anesthesiology 97:959965, 2002 44. Enneking FK, Ilfeld BM: Major surgery in the ambulatory environment: Continuous catheters and home infusions. Best Pract Res Clin Anaesthesiol 16:285-294, 2002 45. Ilfeld BM, Morey TE, Enneking FK: The delivery rate accuracy of portable infusion pumps used for continuous regional analgesia. Anesth Analg 95:1331-1336, 2002 46. Capdevila X, Macaire P, Aknin P, et al: Patient-controlled perineural analgesia after ambulatory orthopedic surgery: A comparison of electronic versus elastomeric pumps. Anesth Analg 96:414-417, 2003 47. Singelyn FJ, Vanderelst PE, Gouverneur JM: Extended femoral nerve sheath block after total hip arthroplasty: Continuous versus patientcontrolled techniques. Anesth Analg 92:455-459, 2001 48. Borgeat A, Kalberer F, Jacob H, et al: Patient controlled interscalene analgesia with ropivacaine 0.2% versus Bupivacaine 0.15% after major open shoulder surgery: The effects on hand motor function. Anesth Analg 92:218-223, 2001 49. Fanelli G, Casati A, Garancini P, et al: Nerve stimulator and multiple injection technique for upper and lower limb blockade: Failure rate, patient acceptance, and neurologic complications. Anesth Analg 88:847-852, 1999 50. Casati A, Fanelli G, Beccaria P, et al: The effects of single or multiple injections on the volume of 0.5% ropivacaine required for femoral nerve blockade. Anesth Analg 93:183-186, 2001 51. Pham-Dang C, Kick O, Collett T, et al: Continuous peripheral nerve blocks with stimulating catheters. Reg Anesth Pain Med 28:82-88, 2003 52. Salinas FV: Location, location, location: Continuous peripheral nerve blocks and stimulating catheters. Reg Anesth Pain Med 28:7982(editorial), 2003 53. Klein SM, Nielsen KC, Buckenmaier CC III, et al: 2-octyl cyanoacrylate glue for the fixation of continuous peripheral nerve catheters. Anesthesiology 98:590-591, 2003 54. Sandhu NS, Capan LM: Ultrasound-guided infraclavicular brachial plexus block. Br J Anaesth 89:254-259, 2002 55. De Andres J, Sala-Blanch X: Ultrasound in the practice of brachial plexus anesthesia. Reg Anesth Pain Med 27:77-89, 2002 56. Ootaki C, Hayashi H, Amano M: Ultrasound-guided infraclavicular brachial plexus block: An alternative technique to anatomical landmark-guided approaches. Reg Anesth Pain Med 25:600-604, 2000 57. Marhofer P, Schrogendorfer K, Koinig H, et al: Ultrasonographic guidance improves sensory block and onset time of three-in-one blocks. Anesth Analg 85:854-857, 1997 58. Marhofer P, Schrogendorfer K, Wallner T, et al: Ultrasonographic guidance reduces the amount of local anesthetic for 3-in-1 blocks. Reg Anesth Pain Med 23:584-588, 1998 59. Nielsen KC, Steele SM: Outcome after regional anesthesia in the ambulatory setting–Is it really worth it? Best Pract Res Clin Anesthesiol 16:145-157, 2002 60. Grant SA: Holy Grail: Long-acting local anesthetics and liposomes. Best Pract Res Clin Anesthesiol 16:345-352, 2002 61. McCarthy RJ, Kerns J, Nath H, et al: The antinociceptive and histologic effect of sciatic nerve blocks with 5% butamben suspension in rats. Anesth Analg 95:711-717, 2002 62. Galvez-Mugica MA, Santos-Ampuero MA, Novalbos J, et al: Ulnar nerve block induced by the new local anesthetic IQB-9302 in health volunteers: A comparison with bupivacaine. Anesth Analg 93:13161320, 2001
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Introduction of continuous regional analgesia has resulted in improved quality of pain relief to patients and reduced the chances of unplanned admission in ambulatory surgical patients. Ambulatory patient controlled regional analgesia at home has further extended the use of regional analgesia beyond the hospital setting. The challenges posed by such ventures has resulted in development of newer techniques to reduce secondary catheter failures as well as adjuvants to local anesthesia that improve success with such novel modalities of pain relief. These include stimulating catheters, disposable infusion devices with patient controlled modalities and use of drugs such as ketamine and long acting local anesthetic formulations. There is further data available with regards to the safety of these techniques. © 2003 Elsevier Inc. All rights reserved.
ublic awareness of the use of peripheral nerve blocks for postoperative analgesia has tremendously increased since Time magazine published the picture of Dr. Greengrass performing paravertebral block on a patient for breast cancer surgery. Recent studies documenting the efficacy of multimodal analgesia for improving patient outcome1-3 have further resulted in an explosion of studies evaluating the use of peripheral nerve blocks for postoperative analgesia beyond the hospital environment. The development of infusion pumps, which are light and disposable, newer needles, and stimulating catheters, the use of imaging and ultrasound, and large scale population based studies have opened a Pandora’s box of what can be accomplished with regional techniques. As far as the consumers are concerned, they do not want to be sore, sick, and sleepy after their surgery, and do not wish to lose days of productivity because of their surgery. How has the regional anesthesia community worked towards accomplishing this goal? I will discuss some newer techniques with regional blocks, adjuvants to extend the duration of analgesia following single injection regional blocks, techniques introduced to improve success with catheters, outcomes with regional analgesia, and newer drugs on the horizon for use in regional analgesia. This article will deal with only peripheral nerve blocks.
P
From the Department of Anesthesiology, Duke University Medical Center, Durham, NC. Address reprint requests to Sugantha Ganapathy, FRCA, FRCPC, Department of Anesthesiology, Duke University Medical Center, Box 3094, 2500 North Pavilion, Durham, NC 27710. Email: ganap001@notes. duke.edu © 2003 Elsevier Inc. All rights reserved. 1084-208X/03/0703-0022$30.00/0 doi:10.1053/S1084-208X(03)00032-6
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Novel Techniques Upper Limb Interscalene Block Although we have been using continuous interscalene blocks at the root level, the classic technique is associated with 100% diaphragmatic paresis, resulting in reduction in tidal volume and functional vital capacity that may preclude this excellent modality of analgesia from being used in patients with moderate or severe respiratory compromise.4-6 Boezaart and coworkers have described a technique of approaching the brachial plexus from the back as a cervical paravertebral block using the loss of resistance and a stimulating catheter, and they document a significantly lower incidence (ie, 30%) of diaphragmatic paresis.7 This technique may be particularly useful for catheterization in patients in whom nerve stimulation and the muscle twitches can cause a lot of pain, such as trauma and fracture. It needs further evaluation to quantify the risks associated with the posterior approach, such as epidural spread and intravascular injections, which intuitively may be higher. The investigators reiterate that the area of shoulder supplied by the cervical plexus will not be anesthetized by this technique, and, therefore, additional superficial cervical plexus blocks should be combined with this technique when used for shoulder surgery. Suprascapular nerve blocks have been used for postoperative analgesia following arthroscopic shoulder surgery8 with no complications, but do we need to perform it in addition to an interscalene block? In a recent, prospective randomized placebo controlled trial, Neal and coworkers note that addition of suprascapular nerve to interscalene block prolongs analgesia (594 ⫾ 369 versus 375 ⫾ 273 minutes) but does not improve outcome.9
Supraclavicular Blocks Supraclavicular nerve blocks are performed at the level of the trunks compactly situated posterosuperior to the subclavian artery and, thus, result in a high success rate with blocking all the components of the brachial plexus. Unfortunately, the conventional approach to supraclavicular block does not facilitate easy catheterization in this area. The paravascular technique by Moorthy and colleagues allows easier catheterization.10 PhamDang and coworkers have described an intersternocleidomastoid approach that facilitates catheterization.11 This technique has also resulted in a lower incidence of diaphragm paresis.12 Neither of these techniques have been adequately exploited,
Techniques in Regional Anesthesia and Pain Management, Vol 7, No 3 (July), 2003: pp 148-154
particularly for ambulatory surgical patients for postoperative analgesia.
Sciatic Blocks These blocks are commonly used for analgesia following foot and ankle surgery, knee and hip arthroplasty, ligament repair around the knee joint, and osteotomy. The majority of the reports involve the use of the classic technique (Labatt) of sciatic blockade at the gluteal region. Blockade at the popliteal fossa has been beneficial for foot and ankle surgery but has a higher incidence of problems with catheters and incomplete blocks. Single injection blocks have been reviewed recently by Singelyn and coworkers.13 The main advantage of the popliteal sciatic block is the preservation of hamstring function, allowing the ease of ambulation on crutches following surgery. A lateral approach at this location has been evaluated and has the advantage that the catheters can be inserted for ongoing analgesia with the patient in the supine position.14-16 di Benedetto and coworkers have described an alternate technique of the subgluteal approach to the sciatic nerve, which is performed with the patient in the Sim position.17 They compared the technique with the popliteal as well as classic sciatic blocks and found the subgluteal approach to be less painful for the patients during insertion. As the block is performed in the intermuscular plane, intuitively, catheterization for extended analgesia should be easier, but this needs to be prospectively evaluated. Naux and coworkers have described a lateral approach to the sciatic nerve at the mid femoral region.18 Because the needle comes at a right angle to the nerve, intuitively, catheterization might be more difficult, but this needs to be evaluated. The advantage of the latter 2 approaches is that the sciatic nerve has not separated and diverged as tibial and peroneal at this location, although the fibers may already be oriented separately. This process may reduce the chances of failure of block with tibial or peroneal component seen sometimes with popliteal blocks. Sciatic nerve block is combined with femoral or lumbar plexus block for surgery, but ambulation with a weak quadriceps and hamstring mechanisms may pose problems. Often, we do femoral block with a short-acting mepivacaine combined with a sciatic catheter for postoperative pain for foot and ankle surgery. If there is a medial incision over the saphenous distribution that often occurs with ankle fusion or bimalleolar fracture, either wound infiltration with long acting local anesthetic or a subsartorial saphenous block19 with or without the catheter may be added for extension of analgesia in the medial ankle without producing extended quadriceps weakness. Williams and coworkers have documented a 2.5-fold reduction in unplanned admission using femoral and sciatic block or femoral block alone following invasive ambulatory knee surgery.20 Currently, we do not send patients home with combined catheters, but that could certainly be done in patients admitted to hospital. With combined catheters, one has to consider the total dose of local anesthetic, potential local anesthetic toxicity, as well as potential for primary and secondary failures with each of those catheters. Patient-controlled regional anesthesia (PCRA) with double catheters has not been tried for obvious reasons.
Lumbar Plexus Blocks It has been well documented by several investigators that femoral 3-in-1 block does not predictably get all the 3 nerves it is intended to get. The obturator nerve is often missed with this UPDATE ON PERIPHERAL REGIONAL ANALGESIA
technique, resulting in inadequate analgesia postoperatively. McNamee and coworkers looked at the role of obturator block in analgesia following knee replacements and noted that additional obturator block improves analgesia.21 The posterior approach to the lumbar plexus anesthetizes the obturator nerve more frequently, thus obviating the need for additional obturator block. The catheters can also be fixed more securely in the back, with less chances of leakage and infection. Unfortunately, there are some concerns with the use of posterior lumbar plexus blocks. In their review on major complications of regional anesthesia in France, Auroy and coworkers have documented a high incidence of major complications (80 of 10,000) and cardiac arrest (1 in 400) following posterior lumbar plexus block.22 This block has also resulted in renal injury, accidental intra-abdominal catheterization, and psoas hematoma, particularly in patients who were anticoagulated.23-26 Although the latter 3 are isolated episodes, one has to be cognizant of these potential complications. Landmarks using a more medial approach may result in a higher incidence of epidural spread, which may cause hypotension and, perhaps, delay discharge in the ambulatory setting. Because of their location, femoral catheters are associated with more episodes of kinking and leakage, apart from a high incidence of bacterial colonization. Cuvillon and coworkers report incidences of 57% colonization and 1.5% bacteremia.27 Because the knee joint has a variable supply from femoral, obturator and sciatic nerves, the quality of analgesia with isolated lumbar plexus block can be variable. Many patients have excellent analgesia following knee surgery just with lumbar plexus block alone, yet a small proportion has significant pain in the posterior knee. This posterior pain can often be managed beyond the first postoperative day with oral opioids and cyclooxygenase-2 inhibitors. Although the addition of sciatic block to lumbar plexus block for analgesia following knee arthroplasty has been of questionable value, for major knee surgery, we run lumbar plexus and sciatic infusions for the initial 24 hours. This process significantly reduces opioid requirements, and postoperative nausea and vomiting (PONV). The sciatic catheter is removed the morning after surgery after a 10 to 15-mL bolus with long acting local anesthetic, and only the lumbar plexus infusion is continued for 48 to 72 hours. This process provides excellent patient satisfaction and good analgesia.
Adjuvants Single injection blocks provide analgesia on an average for 12 to 14 hours. A number of patients may not be suitable for continuous ambulatory patient-controlled regional analgesia due to their lack of proximity to a health facility and/or appropriate home support. If we could provide these patients with an analgesic regime that covers the pain well during the first 24 hours, they will be able to manage subsequent days of pain with oral analgesics. There are several drugs that have been tried to improve analgesia following single injection regional blocks. Although there is evidence of opioid receptors in the peripheral nerves, the addition of opioids in the peripheral nerve blocks have resulted in variable efficacy. In fact, the addition of sufentanil has increased the incidence of hypoxemia and PONV.28 Murphy and coworkers have reviewed this topic systematically and note that 6 of 10 studies showed evidence of improved analgesia, and only 4 of them had a systemic narcotic control
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group.29 The investigators conclude that the evidence of opioid efficacy in peripheral nerve blocks is weak. Contrary to the opioids, clonidine, an ␣-2 agonist that has C-fiber blocking potential when added in low doses (0.5 to 1 g/kg) to the peripheral nerve blocks, significantly prolongs analgesia but loses additional efficacy at higher doses.30-32 The higher doses may also be associated with undesirable side effects, such as sedation and hemodynamic changes.31,33,34 Although this might be acceptable in the inpatient setting, it might not be prudent in the ambulatory setting. Other additives, such as neostigmine, have not been useful for extending the analgesia following intravenous regional anesthesia (IVRA) or nerve blocks. Ketamine added to small dose interscalene block has provided extended analgesia.35 Ketorolac added to IVRA has also produced extended analgesia.
Ambulatory Regional Analgesia By far, the most progress regarding postoperative analgesia has been made in the field of ambulatory anesthesia. This area has been extensively reviewed by Klein.36 Orthopedic patients perceive the most significant pain following ambulatory surgery that adversely impacts patient outcome.37,38 Klein and coworkers had reported on the safety and efficacy of regional anesthesia in the ambulatory setting, with patients discharged home with ongoing sensory and motor block providing extended analgesia.39 Grant and colleagues reported their experience with 228 patients in an ambulatory surgery center where patients received an infusion via the block catheter in a short stay facility for 24 hours.40 They bolused the catheter before discharge and removed the catheters. Their initial block success was 94%. Their secondary catheter failure was 10%. They managed to reduce the incidence of postoperative nausea to an impressive 1.7%. Since the introduction of elastomeric41 as well as lightweight electronic pumps, patients are discharged home with an ongoing local anesthetic infusion via the peripheral nerve catheters. Ilfeld and coworkers42,43, and Enneking and Ilfeld44 have documented excellent analgesia with this technique using an electronic pump, and report excellent pain relief, reduced nausea, and improved sleep pattern during the postoperative period following orthopedic surgery. Function of different pumps regarding the accuracy of delivery has been evaluated by Ilfeld45 as well as Capdevila46 and colleagues. Capdevila and coworkers note that both class of pumps perform acceptably. The elastomeric pumps as well as some of the newer electronic pumps (Fig 1) are disposable and, thus, may be used in patients at a distance from the hospital. The elastomeric pumps usually have a fixed reservoir and fixed delivery rate. Currently, there are some elastomeric pumps that also provide the facility of patient administered boluses. There were instances when the entire contents of the bulb were delivered into the patient when the clamp was opened and closed to deliver the set bolus. The “Rawal pump” has a built in valve that is activated by the patient to provide a fixed bolus, so that accidental discharge of the entire contents of the bulb is avoided. The rate of delivery of these bulbs can depend on storage temperature, vehicle for local anesthetic, and distal occlusion pressure, but technically, they are easy to use. The electronic pumps are significantly more expensive, but they allow a larger reservoir of local anesthetic and variable bolus rates. The Sorensen microject pump (Fig 1) and similar devices are reusable. With the microject
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pump, the maximum rate per hour is 9.9 ml, and the maximum bolus dose is 2 ml, which precludes higher doses with boluses. Although this may be acceptable for upper limb blocks, lumbar plexus and femoral blocks being compartment blocks sometimes require higher bolus doses. Currently in the hospital setting, we allow nurse-administered boluses of 10 ml every 6 hourly when required. Such a paradigm is currently impossible with the ambulatory PCRA. The future might have a device with a red button for the larger bolus and a green button for the smaller bolus set to lock out differentially with a predetermined maximum dose per 4-hour period lock out. Our experience suggests that it is rare that patients require the larger boluses beyond the first 23 hours. Singelyn and coworkers used 0.125% bupivacaine, with clonidine 1 g/mL and sufentanil 0.1 g/mL, via a femoral nerve sheath catheter as a continuous infusion at 10 mL/h or as PCA boluses only 10 mL/h, or as PCA boluses 5 mL per 30 minute.47 Pain scores at rest and supplemental analgesia were comparable in the 3 groups. At 48 hours, pain relief on movement was significantly better associated with a significant reduction in the bupivacaine consumption in the 2 bolus groups compared with the continuous infusion group. Side effects were comparable in the 3 groups. Satisfaction scores were significantly higher in the 5 mL bolus group than in the other groups. The investigators concluded that PCRA techniques reduce the local anesthetic consumption without compromise in patient satisfaction or pain scores. At our institution, we run a small dose of basal infusion and allow the patient to self-administer 2 to 4-mL boluses every 20 minutes as needed. The dosages are adjusted for patient size and the number of catheters having an infusion. If patients receive double catheter infusions, one of them will be a low dose continuous infusion, such as the sciatic for knee surgery and the second catheter will be set for PCRA. Patients receiving double catheter infusions during the first 23 hours have one of them removed after a 10 to 15-mL bolus the morning after surgery, depending on the site of surgery. The removal process is used to educate the home caregiver for removing the second catheter at home after 48 hours. All patients receive verbal and written instructions, and the staff is available 24 hours a day for troubleshooting. Patients do not like a weak, heavy limb that is difficult to manage during the postoperative period. More studies are required to evaluate the optimum concentration and dosing with continuous regional analgesia. Borgeat and coworkers compared 0.2% ropivacaine with 0.15% bupivacaine and note that bupivacaine resulted in more significant hand motor block.48 Although they have not used an equipotent dose, the fact that the ropivacaine group had very little motor block makes it a drug of choice. Whether a lower concentration, larger volume is better is currently unknown. There are no data on levobupivacaine for this indication. There are several important details that one needs to pay attention to regarding sending patients home with regional block infusions. Patient selection, availability of a chaperone, willingness and capacity to use the simple equipment, proximity to a health care facility, written as well as verbal education, and availability of staff 24 hours a day and 7 days a week for troubleshooting are very important. This modality has reduced the need for hospital admissions in a number of cases. It also significantly reduces the opioid requirements, reduces postoperative nausea and vomiting, and results in excellent patient SUGANTHA GANAPATHY
Fig 1. Infusion devices for ambulatory regional analgesia. 1. McKinnnley pump; 2. Sorensen microproject pumps; 3. Stryker pain pump 2, with 250 or 500 mL reservoir.
satisfaction. This modality has not only been used for postoperative pain but also to facilitate physiotherapy and for complex regional pain syndrome (personal unpublished data). Although the patients are sent home with ongoing motor sensory block, our experience reveals that with appropriate instructions, the patients protect their numb, weak limb. We usually make 1 to 2 telephone calls daily to ensure safe monitoring during the infusion. The removal of catheter should ideally be done after the block wears off so that patients may stop pulling on the catheter if they should perceive any pain. Although that is not our practice, preliminary data from the Duke Ambulatory Surgical Center (ASC) database reveal that persistent neurologic deficits UPDATE ON PERIPHERAL REGIONAL ANALGESIA
in this group are similar to the ones receiving single injection blocks.
Techniques to Improve Success Rates A number of investigators have used multiple stimulation techniques and have shown that it improves success with the initial block as well as reduces the dose of local anesthetic required for the block.49,50 Although the investigators claim that it does not lead to increased neurologic injury (1.7%), with the current information available on the conductive properties at the needle tip with small amounts of ionic solutions delivered near the
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Fig 2. Tunneled stimulating catheter. Lower arrow indicates needle entry site, and upper arrow shows tunneled exit of the catheter. The Pajunk stimulating assembly with the catheter (right panel).
nerve, the use of multiple stimulation techniques may not be for the beginner regionalist. Where individual nerves are separated from each other, such as in the mid humeral or infraclavicular location, this technique may offer selective catheterization of the nerve supplying the operative site for postoperative analge-
sia, which may result in reduced local anesthetic doses. This concept needs further evaluation. Stimulating catheters have been introduced recently into the market (Arrow International, Reading PA and Pajunk GmbH, Geisingen, Germany) (Figs 2 and 3). As the initial dose is
Fig 3. Arrow stimulating catheter assembly. Note the stimulating metal tip on the catheter and the attachment on the blue connector to facilitate stimulation of the catheter after the stylet is removed.
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delivered through the catheter, if one is able to establish the block with nominal doses, it may signify appropriate location of the catheter. The stimulating properties of the Pajunk catheter are slightly different from the needle because the gold tip requires a higher current strength to maintain the stimulus (Fig 2). The catheter is soft and flexible. The prototypical catheters had a filament at the syringe end that made tunneling cumbersome. The Arrow catheter has similar stimulating qualities to the needle but has a rather rigid stylet and large (17 G), standard length Tuohy needle to initiate the block. A short needle has recently been introduced for the brachial plexus blocks. There is a learning curve to using these catheters, and clinicians should use the workshops, such as the RASCI (University of Iowa), to familiarize themselves with the use of these catheters. In an observational study, Pham-Dang and coworkers, using the Pajunk catheters, note that with upper limb catheters, the lack of stimulation signified misplaced catheter, while in the lower limb, one may not stimulate with the catheter but may still be able to establish the block via the catheter.51 Unfortunately, some methodological errors make it difficult to interpret their data. These investigators injected saline before advancing the catheter, which could have altered the stimulating environment with dispersion of current. Secondly, they did not advance the catheter while stimulating, which is a fatal flaw in their technique.52 There are no prospective randomized trials to document the safety and success rates with these catheters. Intuitively, these catheters should reduce secondary failure rates if the block was initiated by injecting the anesthetic via the catheters and they are fixed appropriately. Klein and coworkers reported on the cyanoacrylate glue for fixing these catheters.53 Subcutaneous tunneling (Fig 2) may not only allow the catheters to be fixed well but may also prevent leakage, which is the most common cause for the catheters to become loose and dislodged or kinked. The second technique that may reduce secondary catheter failure is the use of ultrasound to position the catheters in the appropriate location. A number of studies54-58 have examined the success of blocks using ultrasound, but there are no prospective trials researching secondary catheter failures. There are no prospective trials evaluating either of these techniques.
Outcomes Nielsen and Steele have recently reviewed outcomes after regional analgesia.59 Studies have documented reduction in unplanned admission, improved patient satisfaction, reduction in PONV, and improved sleep. The quality of life improvement and stress response to surgery, and reduction in cognitive dysfunction need prospective evaluation with regional analgesia.
Pharmacology for the Future Long acting local anesthetic with microsphere laden bupivacaine underwent early clinical trials and have been withdrawn due to prolonged conduction block with these formulations in animals.60 Butamben, an ester local anesthetic used in animal experiments, has been documented to produce prolonged sensory block without motor block lasting more than 3 weeks.61 IQB-9302, an amide local anesthetic, has produced sensory block lasting 30% longer than bupivacaine.62 These are exciting developments in regional analgesia. Whether they will replace continuous catheter regional analgesia will be determined by UPDATE ON PERIPHERAL REGIONAL ANALGESIA
their safety. For now, the art of pain management with regional techniques is undergoing the artist’s final touch for perfection.
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