VISUAL EVALUATION OF RESIDUAL CURARIZATION IN ANESTHETIZED PATIENTS USING 100-HERTZ, 5-SECOND TETANIC STIMULATION AT THE ADDUCTOR POLLICIS MUSCLE

We were looking for a clinical test to indicate a train-of-four (TOF) ratio of approximately 0.9. We compared the adductor pollicis muscle ( AP) visually evaluated response to ulnar nerve 100-Hz, 5-s tetanus (RF 100 Hz) with the measured AP TOF ratio in 30 ASA physical status I or II adult anesthetized (propofol, sufentanil, N2O/O-2) patients. After the induction of anesthesia, the left ulnar nerve was stimulated at th e wrist (single twitch and TOF) and the resultant isometric force was measured. When TOF was assessed, the independent investigators, unawar e of the left AP-measured TOF ratios, visually evaluated the presence or absence of AP fading elicited by right ulnar nerve 100-Hz, 5-s teta nus. The 30 patients were randomly allocated to receive either 0.5 mg/ kg atracurium (n = 15) or 0.1 mg/kg vecuronium (n = 15). The neuromusc ular blockade was allowed to resolve spontaneously. A multiple logisti c regression analysis was performed by computing the 771 visual observ ations. The probabilities of success of 100-Hz, 5-s tetanus to detect TOF ratios of 0.8, 0.85, and 0.9 were 99%, 96%, and 67%, respectively. The sensitivity and specificity of 100-Hz, 5-s tetanus as an indicato r of TOF ratios of 0.85 and 0.9 are 100% and 75%, 54% and 67%, respect ively. We conclude that RF100 Hz Visual assessment seems to be highly sensitive in evaluating residual paralysis, as the absence of RF100 Hz visual fading at the AP is compatible with a TOF ratio >0.85. Implica tions: After the administration of muscle relaxants, the absence of vi sual fading at the adductor pollicis, elicited in anesthetized patient s by 100-Hz, 5-s tetanus, is compatible with a train-of four ratio >0. 85. Therefore, clinical observation of fading after 100-Hz, 5-s tetanu s seems to be a highly sensitive test in evaluating residual paralysis .