Subarachnoid sufentanil for early postoperative pain management in orthopedic patients - A placebo-controlled, double-blind study using spinal microcatheters

Background: Continuous spinal anesthesia is frequently used for intraoperat ive anesthesia but rarely for postoperative pain management. Because even s mall doses of local anesthetics can be associated with motor deficits, suba rachnoid opioid injection may be an alternative. Methods: Eighty patients randomly received a subarachnoid injection of 10 m ug sufentanil, 5 mg bupivacaine, 2.5 mug sufentanil plus 2.5 mg bupivacaine , or saline through 28-gauge spinal microcatheters for early postoperative pain relief after major lon er-limb surgery (n = 20 in each group). Hemodyn amic and respiratory parameters, pain scores, and motor function were monit ored, and sufentanil concentrations in plasma and cerebrospinal fluid were measured. Ten additional patients received up to three repetitive injection s of 10 mug sufentanil over 24 h, Results: All drugs provided excellent pain relief within 15 min after injec tion, lasting 128 +/- 61 min with sufentanil 146 +/- 74 min with bupivacain e, and 167 +/- 78 min with the mixture. Patients receiving bupivacaine show ed the highest cephalad extension of sensory block (median, T6) and the mos t intense motor block, whereas patients given only sufentanil had no motor deficit. The duration of analgesia was shorter after subsequent sufentanil injection (100-115 min) than after the first injection (198 +/- 70 min). Si x of 50 patients with sufentanil experienced a short episode of respiratory depression within 30 min after the first injection. Cerebrospinal fluid co ncentrations of sufentanil peaked at 5 min after injection (183 +/- 167 ng/ ml) but were at the level of detection in the plasma. Conclusions: Sufentanil injected through microspinal catheters provided pro found pain relief without impairing motor function when compared with bupiv acaine. However, close monitoring remains mandatory in this setting.