A Microcomputer-Based Neuromuscular Blockade Monitor

A portable device has been developed and tested for monitoring the effects of neuromuscular blocking drugs. It incorporates a nerve stimulator, force transducer, and microcomputer for quantitating the level of neuromuscular block. The nerve stimulator, under microcomputer control, is capable of delivering single shocks at 0.1 Hz, train-of-four stimulation at 2 Hz, and tetanic stimulation at 30, 100, or 200 Hz. Stimuli are applied to the ulnar nerve. The response, adduction of the thumb, is sensed by a flexible beam force transducer. The output of the transducer is amplified and then processed by the microcomputer. The microcomputer quantitates twitch and train-of-four responses, and calculates the ratio between the first and fourth responses of train-of-four. The ratio is used to estimate the level of block. The device has clinical potential as a trend monitor of neuromuscular function during anesthesia and surgery. It also has research potential for determining the effects of newer neuromuscular blocking drugs for comparison with presently used drugs or, alternatively, for determining the effects of blocking drugs in altered physiological states.