Quantitative assessment of residual antidepolarizing block (part 1)

A method is presented for the assessment of residual curarization after the use of antidepolarizing muscle relaxants which does not involve the necessity for establishing control observations. The ulnar nerve at the elbow was stimulated with a train of four pulses repeated intermittently. The muscle response to this train of four stimuli was recorded and analyzed using three ratios of twitch height (or electromyographic responses). Ratio (a) was taken as the height of the first response of the train to the height of the control response (i.e. the response before muscle relaxant was given), ratio (b) as the height of the second response to the height of the first response, and ratio (c) as the height of the fourth response to the height of the first response. There was a highly significant positive linear association between ratio (a), which involves the use of a control response, and the other two ratios, (b) and (c), which do not involve a control response.