Effect of Direction of Bevel on the Spread of Spinal Anesthesia with Hyperbaric 0.5% Tetracaine

Lee, Sang Chul; Lim, Young Jin; Gwak, Mi Sook

Abstract

Many factors influence the distribution of local anesthetic solutions within the subarachnoid space. Among the factors which are under the control of the anesthesiologists, the effect of direction of bevel on spinal anesthetic spread was investigated in 40 young adult male patients undergoing orthopedic or urologic surgery, with ASA physical status 1. Patients were randomized into one of four groups, according to the direction of bevel(cephalad, caudad, up, down). With patient in the lateral decubitus position, dural puncture was performed in the midline at the L3-4 interspace with a 23-gauge needle, and the patients were immediately turned to supine position. Local anesthetic solution in all patients was composed of 1.6 ml of 1% tetracaine and 1.6 ml of 10% dextrose, resulting 3.2 ml(16 mg) of 0.5% tetracaine. Segmental spread of analgesia was determined by pin-prick in the anterior axillary line. Duration of block and degree of motor block were measured by two segment regression time and Bromage scale, respectively. No difference was observed among four groups in the onset time to maximal level of sensory block, two segment regression time, and degree of complete motor block of lower limbs. In caudal group, maximal level of sensory block was about 1.1-1.4 segments lower than other groups, but no statistical significance was found. There were wide variations in the maximal level of sensory block(T11-T3), and time to reach this(5 min-35 min). The present study indicates that the direction of bevel is unimportant in influencing anesthetic characteristics of spinal anesthesia and, it is difficult to predict accurately the onset time and the level which will be attained because there are wide individual variations in the spread of local anesthetics in subarachnoid spaee.