RESUMEN
This study was designed to evaluate the duration required to perform anaesthesia, achieve surgical block and fulfill standardized discharge criteria for knee surgery with spinal anaesthesia versus combined sciatic femoral nerve block. fifty patients ASA 1-11 scheduled for knee hrartoscopy were randomized to receive either spinal anaesthesia with 4 mg of 0.5% hyperbaric bupivacaine [spinal group], or combined sciatic -femoral nerve block with 0.75% ropivacaine and a multiple injection technique [12 ml for femoral nerve block and 18 ml for sciatic nerve block]. Time lasting from skin disinfection to the end of local anaesthetic injection [performance time] and then to achieve surgical anaesthesia [readiness for surgery], time required for block resolution, as well as time for discharge were recorded. Occurrence of adverse events was also recorded. Performance time was longer with sciatic femoral block than spinal block while no differences were observed in the time required to achieve anaesthesia [mean time for sensory block was 6.2 +/- 1.5 min and 8.8 +/- 1.7 min in the spinal and sciatic femoral block respectively and that for motor block was 9.7 +/- 3.6 min and 10.5 +/- 3.5 min]. No differences in haemodynamic parameter or in the visual analogue scale. Patients in the spinal group showed faster resolution of nerve block however no significant differences were observed in the discharge time. Sciatic femoral nerve block with multiple injection technique using ropivacaine 0.75% provided adequate anaesthesia for knee arthroscopy as spinal anaesthesia with no differences in home discharge and less side effects