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Ann Thorac Surg 1999;67:828-829
© 1999 The Society of Thoracic Surgeons
a Division of Anesthesiology, The Cleveland Clinic Foundation, 9500 Euclid Ave/E-31, Cleveland, OH 44195, USA
Invited commentary
Watson and colleagues present a scientifically well-conducted, randomized, double-blind clinical investigation that demonstrates that lidocaine offers pain relief equivalent to bupivacaine when administered for continuous extrapleural intercostal nerve blockade after thoracotomy. Although they did not assess or compare a dose-response range for either local anesthetic, the doses used for each drug (bupivacaine, 0.5 mg · kg-1 · h-1; lidocaine, 1 mg · kg-1 · h-1) are well-established in the literature for continuous extrapleural intercostal nerve blockade. These doses proved to be equianalgesic in this study, producing similar pain scores with equal supplemental opioid requirements.
Even though systemic toxicity did not occur in any of the limited number of patients in this study, the authors’ concern about the potential for systemic toxicity with bupivacaine for this continuous nerve blockade technique is well taken and cannot be emphasized enough. Whichever local anesthetic drug is selected, it must be noted that intercostal nerve blockade results in the highest plasma concentrations of local anesthetic of all commonly used regional anesthesia techniques. Moreover, the dose of bupivacaine (0.5 mg · kg-1 · h-1) is approaching the range generally considered at risk for producing toxicity, used in a group of surgical patients who may be at higher risk for local anesthetic toxicity because of heart failure, liver disease, or renal failure. In contrast, the dose of lidocaine (1 mg · kg-1 · h-1) is well below the toxic range. Most importantly, the cardiotoxicity associated with bupivacaine (refractory wide-complex arrhythmias and asystole) is far more dangerous and life-threatening than with lidocaine. Furthermore, the "window of forewarning" between less life-threatening central nervous system toxicity (agitation, confusion, seizures), which occurs at lower plasma levels for any local anesthetic, and cardiotoxicity, which occurs at higher plasma levels, is narrower with bupivacaine than lidocaine. Thus, I agree with the authors’ conclusion that lidocaine offers equivalent pain control with less risk of systemic toxicity, even though their study had insufficient statistical power to directly assess this low frequency but life-threatening end point. Given these results and the potentially toxic doses of bupivacaine required to provide equal analgesia, one must recommend lidocaine over bupivacaine for this continuous regional anesthesia technique.
It is important not to condemn bupivacaine when used in appropriate well-established safe doses for other continuous regional anesthesia techniques. Bupivacaine offers much wider separation of sensory and motor blockade ("motor sparing") in comparison with lidocaine and other shorter-acting local anesthetics, making it much more ideal for continuous epidural analgesia. Typical dose requirements are in the very safe range of 0.1 to 0.3 mg · kg-1 · h-1. Similarly, for "single-shot" intercostal nerve blocks, bupivacaine offers much longer duration of pain relief with well-established safety, particularly when epinephrine is added to limit the rate of systemic uptake and prolong the duration of analgesia. Nonetheless, for regional anesthesia and analgesia techniques that require higher doses of long-acting local anesthetic, bupivacaine is gradually being replaced by the newer local anesthetic ropivacaine and the soon-to-be-introduced levo-bupivacaine, which offer a similar efficacy profile with less cardiotoxicity.
Although this study did not include a placebo-control continuous extrapleural intercostal nerve blockade group, the visual analog scale pain scores and patient-controlled morphine requirements were relatively low. Other studies have demonstrated the efficacy of this technique. Continuous intercostal nerve blockade is an effective but underused regional anesthesia technique for controlling pain associated with fractured ribs, chest wall injuries, and flail chest as well as after thoracic and upper abdominal operations. Even with placement of a catheter through a needle inserted percutaneously into a single intercostal space, a volume of local anesthetic can extend subpleurally up to five adjacent intercostal spaces. In this case, creation of an extrapleural pocket for two to three interspaces above and below the level of the thoracotomy and placement of the catheter by direct visualization assures appropriate placement and adequate spread of the drug.
Although supplemental systemic opioids are required with this regional analgesia technique, opioid requirements are significantly reduced and pain relief is improved. This underscores the important role of regional analgesia techniques and other opioid sparing strategies (ie, nonsteroidal antiinflammatory drugs) in the management of postthoracotomy pain. Systemic opioids alone are usually associated with incomplete pain relief, and often drowsiness, nausea, vomiting, urinary retention, cough suppression, and respiratory depression. Effective postthoracotomy analgesia using regional techniques can reduce morbidity, improve patient outcome, hasten recovery, reduce hospital costs, and perhaps even prevent chronically debilitating postthoracotomy pain syndromes.
Thoracic epidural analgesia (local anesthetic with or without opioid) provides more complete pain relief and is much more commonly used after thoracotomy. However, the technical expertise, management experience, and 24-hour per day availability of anesthesiologists to provide this technique are not available in some institutions. Also, there are situations (ie, sepsis, coagulopathy) in which epidural analgesia may be contraindicated. Continuous extrapleural intercostal nerve blockade offers an effective alternative. Furthermore, because the side effects of sympathetic blockade and motor blockade, as well as the remote specter of catastrophic spinal cord injury, are avoided, comparison studies are warranted.
Related Article
Ann. Thorac. Surg. 1999 67: 825-828.
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