A low-dose hypobaric bupivacaine spinal anesthesia for knee arthroscopies.

Background and objectives: Ambulatory surgery requires anesthesia methods that allow rapid recovery and safe discharge of the patient. Spinal anesthesia is easy and quick to perform, and the use of noncutting small gauge needles reduces the occurrence of postdural puncture headache. For minimal hemodynamic consequences and faster recovery and discharge it would be optimal to limit the spread of spinal anesthesia only to the area which is necessary for surgery. In this study, the possibility in achieving unilateral spinal anesthesia with 0.18% hypobaric bupivacaine was studied.

Methods: Spinal anesthesia with 3.4 mL of hypobaric 0.18% bupivacaine (6.12 mg), without any intravenous infusion or prophylactic vasopressors, was administered with 27-gauge Whitacre unidirectional needle to 70 ASA I and II patients undergoing knee arthroscopies. The patients were allocated randomly to be kept either 20 (group I) or 30 (group II) minutes in the lateral position operation side uppermost. Sensory and motor block (pinprick/modified Bromage scale) were compared between the operation and the contralateral side.

Results: The motor and sensory block between operation and contralateral sides were significantly different at all testing times in both groups (P < .001, Mann-Whitney U test). The motor block was completely unilateral in 14 patients (39%) in group I and in 22 patients (65%) in group II. The hemodynamics were stable in all 70 patients.

Conclusions: Approximately three and a half milliliters hypobaric 0.18% bupivacaine (6.12 mg) provides a predominantly unilateral spinal block. Thirty minutes spent in the lateral position does not provide benefits over 20 minutes. The main advantages of our method are the hemodynamic stability and the patient satisfaction.