Detection of neuromuscular block in man. Preliminary communication.

The presence of residual neuromuscular block is often difficult to assess. Muscle tension or electrical activity in response to motor nerve stimulation is of limited value without control responses. Neuromuscular transmission which was suppressed by tubocurarine in the in vitro preparation could be briefly restored by application to the nerve of two or more very closely spaced stimuli; this occurred because of summation of endplate potentials. In this preliminary communication a technique for the detection of neuromuscular block is suggested which utilizes this facilitation phenomenon. The summation of endplate response was demonstrated to occur in an in vivo preparation when a double stimulus is applied. An attempt was made to define the critical limits of stimulus spacing which would be necessary for the application of the technique to humans. A simple comparison between the twitch tension resulting from a single stimulus and that resulting from a double stimulus with a 1-1.8 m.sec stimulus interval may reveal evidence of neuromuscular block.