A Study of Succinylcholine Dose Response Using Isolated Arm Test

Kim, Sung Yell; Kim, Tae Jung; Hwang, Kyung Ho; Kim, Sun Chong

Abstract

Succinylcholine is still widespread use, despite the lack of understanding of the mechanisms of its action at the neuromuscular junetion. It is assumed that succinylcholine acts exclusively on the post-junctional structure of the neuromuscular junction, phase I block, but after administration of additional large doses, this phase I block is followed by the appearance of phaae II block, curare like. These phase I and II block are purely descriptive terms and do not imply a mechanism of action. Not only would administration of repeat of large doses of succinylcholine for study in vivo be dangerous but objective measurement of their effect can be difficult to interpret. Therefore, the present study was designed to determine succinylcholine doses response relationships for the incremental bolus and its divided doses using isolated arm test which is isolated from systemic circulation appling tourniquet on upper arm and using small dose of muscle relaxant safely, and measuring the force of contraction of adductor pollicis with Accelograph under the enflurane and 50% N2O anesthesia. The tourniquet was kept inflated for 4 minutes to allow retrograde spread of some of the succinylcholine into the capillary bed where neuromuscular block was established. At the end of 4 minutes, the tourniquet was released and the interpretation of twitch response was started: 1. The incremental doses of succinylcholine induced significantly prolongation of duration (p< 0.005) but no significant different in recovery index. 2. TOF ratio runs down definitely from over 40 mg incremental doses with bolus injection and more in divided doses than bolus. 3) The relationship between incremental doses and TOF ratio decreasing was statistically signifi-cant (y=-0.49x+84.5, r= 0.65, p<0.005)