Background: The purpose of this prospective, randomized study was to evaluate the time required to perform anaesthesia, achieve surgical block and fulfil standardized discharge criteria in outpatients receiving knee arthroscopy with either spinal anaesthesia or combined sciatic-femoral nerve block.
Methods: After a standard midazolam/ketoprofen premedication and baseline measurement of cardiovascular parameters, 50 ASA I-II patients scheduled for elective outpatient knee arthroscopy were randomized to receive spinal anaesthesia with 8 mg of 0.5% hyperbaric bupivacaine (group Spinal, n=25), or combined sciatic-femoral nerve block with 25 ml of mepivacaine 20 mg ml(-1) and a multiple injection technique (15 ml for femoral nerve block and 10 ml for sciatic nerve block). Times lasting from skin disinfection to the end of local anaesthetic injection (preparation time) and then to achieve surgical anaesthesia (readiness for surgery), as well as times required for block resolution, micturition, unassisted ambulation, and home discharge were recorded by a blinded observer. Occurrence of adverse events was also recorded.
Results: Preparation time (mean+/-SD) was longer with sciatic-femoral block (8+/-2.7 min) than spinal anaesthesia (5+/-2.1 min) (P=0.0002) while no differences were observed in the time required to achieve readiness for surgery (14+/-5 min and 15+/-6 min in the Spinal and Sciatic-femoral groups, respectively). No differences in haemodynamic side effects and need for intraoperative additional analgesia were observed. Patients receiving spinal anaesthesia showed a faster resolution of nerve block and longer time to micturition (137+/-49 min and 231+/-101 min) than patients receiving peripheral nerve blockade (206+/-51 min and 145+/-36 min) (P<0.0005 and P=0.002, respectively); however, no differences were observed in the time required to fulfil standardized discharge criteria (241+/-101 min in group Spinal and 209+/-70 min in group Sciatic-femoral; P=0.86).
Conclusion: In patients receiving elective outpatient knee arthroscopy, using a combined sciatic-femoral nerve block with 25 ml of mepivacaine 20 mg ml(-1) and a multiple injection technique results in a slightly longer preoperative time but provides similarly effective anaesthesia with no differences in home discharge times as compared to spinal anaesthesia with 8 mg hyperbaric bupivacaine.