CONTINUOUS REGIONAL ANALGESIA BY INTRANEURAL BLOCK - EFFECT ON POSTOPERATIVE OPIOID REQUIREMENTS AND PHANTOM LIMB PAIN FOLLOWING AMPUTATION

The objective of this study was to assess the effectiveness of a previ ously described technique of regional analgesia (continuous infusion o f local anesthetic through a catheter placed at the time of amputation within the exposed sciatic or posterior tibial nerve) on relieving th e postoperative pain in a heterogeneous group of patients who underwen t lower extremity amputations. A second objective was to determine the effect of such treatment on the incidence and characteristics of phan tom limb pain 6 months or more after surgery in the same patients. The study design was retrospective, unblinded, controlled (postoperative pain), and unblinded questionnaire and interview (phantom pain) were u tilized. Subjects were inpatients at Harborview Medical Center, Univer sity of Washington, Seattle, WA. Nineteen bupivacaine-treated and 40 n onbupivacaine-treated patients who underwent lower extremity amputatio n subsequent to trauma, infection, long-standing injury (poor or no fu nction), congenital deformity, or burns were evaluated in the postoper ative pain management assessment. Nine treated and 12 untreated patien ts were interviewed in the phantom pain assessment. Bupivacaine 0.5% 2 -6 ml/h was infused through a polyamide 20-gauge catheter inserted int o the sciatic or posterior tibial nerve sheath under direct vision at the time of surgery. All patients, treated and control, received opioi d analgesics systemically during the 72-hour period of study. The post operative opioid analgesic requirement of treated patients was compare d with that of control patients who received opioid analgesics alone. A questionnaire was administered to assess presence, severity, and cha racter of phantom pain. The opioid analgesic requirement of treated pa tients was comparable to that of controls (132.7 ml of morphine equiva lents/72 h treated; 151.3 ml morphine equivalents/72 h control), as we re the incidences of all opioid related side effects. The follow-up qu estionnaire revealed a similar incidence (77% treated; 50% controls) a nd profile of phantom pain in both groups. In this study, continuous r egional analgesia by intraneural infusion of local anesthetic failed t o decrease systemic analgesic requirements or reduce the incidence of phantom pain compared with standard opioid analgesia. Since two previo usly published reports have found this technique effective, several po ssible reasons for the different results of this study are suggested.