Microcomputer controlled administration of muscle relaxant

Abstract

A closed loop system was applied to control the administration of muscle relaxant in ten patients. The integrated evoked electromyographic (IEMG) response to stimulation of the ulnar nerve was measured with a DATEX anesthesia and brain activity monitor (ABM). The digital output of the ABM was transferred to an NEC PC8201 microcomputer through an RS-232C interface and was used as the feed-back signal. Alcuronium chloride was used as muscle relaxant and simple ON/OFF action of a syringe pump was selected for the controller algorithm. Following a bolus injection of alcuronium chloride (0.2mgkg^-1), muscle relaxation was regulated to the initial set point (ten percent of the control IEMG) by this system over the period of 82 to 588 minutes. During the period the level of muscle relaxation was stable with the mean IEMG response of 9.4 to 11.0 percent of the control. The mean dose of the drug infused during the period was 1.2μgkg^-1min^-1 and roughly proportional to the duration of the period. The simple ON/OFF algorithm was proved to be capable of successfully maintaining the level of muscle relaxation during anesthesia.