Lumbar Sympathetic Blockade Does Not Prevent Tourniquet-Induced Hypertension During General Anesthesia

Abstract

The effect of unilateral lumbar sympathetic blockade on tourniquet-induced hypertension during general anesthesia was studied in 44 patients undergoing orthopedic surgery of the lower extremity, including the use of a thigh tourniquet for more than 1 hour. After the induction of general anesthesia, a lumbar sympathetic blockade at L2 and L4 levels was induced on the side to be operated on using either 2 × 20 ml of 0.5% bupivacaine or 2 × 20 ml saline in double-blind fashion. Plasma bupivacaine concentrations were determined at 5, 10, 20, and 30 minutes after the injections. The quality of the sympathetic blockade was judged by the difference in toe skin temperature between the blocked and unblocked leg (5.5°C [±1.6°C, SD]). Four patients were excluded from the study because the temperature difference was less than 2°C. In both groups, 15 of 20 patients had an increase of more than 30% in systolic or diastolic blood pressure during anesthesia. The arterial blood pressure drop at the time of deflation of the thigh tourniquet was similar in both groups. Seven patients in both groups developed bradycardia (decrease of > 30% of the reference value). One patient in the saline group had a heart rate increase of more than 30%. The mean bupivacaine plasma concentration at 5 minutes was 1.1 μg/ml (±0.5 μg/ml, SD), and the maximum concentration was 2.8 μg/ml. The need for postoperative analgesics in the recovery room was similar in both groups.