A low dose of plain or hyperbaric bupivacaine for unilateral spinal anesthesia

Background and Objectives: Unilateral spinal anesthesia may be advantageous , especially in the outpatient setting. A low dose of anesthetic solution, pencil-point needle, low speed of intrathecal injection, and a lateral posi tion have been reported to facilitate the production of unilateral distribu tion of spinal anesthesia. We compared the effects of plain and hyperbaric bupivacaine in attempting to obtain a unilateral spinal anesthesia for pati ents undergoing outpatient knee arthroscopy. Methods: Sixty patients were randomly allocated to 2 groups to receive eith er 1.2 mt (6 mg) of plain 0.5% bupivacaine (group 1; n = 30) or 1.2 mt (6 m g) of hyperbaric 0.5% bupivacaine in 8% glucose (group 2; n = 30). Drugs we re administered at the L2-3 interspace with the patient in the lateral posi tion. Patients remained in this position for 20 minutes before being turned supine for the operation. Spinal block was assessed by pinprick and modifi ed Bromage scale and compared between the operated and nonoperated sides. Results: There was a significant difference between the operated and nonope rated side in both groups at all testing times, but a more unilateral spina l block was achieved with hyperbaric bupivacaine. Unilateral motor and sens ory block was observed in 25 patients in group 2 (83%) and in 11 patients i n group 1 (37%) (P < .01). The hemodynamic changes were minimal, since hypo tension occurred only in 5.0% and bradycardia in 1.7% of all patients. Conclusion: In conclusion, the spinal anesthesia in both groups are suitabl e alternatives for adult outpatient knee arthroscopies, but hyperbaric bupi vacaine provides us with a more unilateral spinal block.