Comparison of contralateral acceleromyography and electromyography for posttetanic count measurement

Electromyography has advantages over mechanomyography and acceleromyography. Previously, agreement of the train-of-four counts between acceleromyography and electromyography was found to be fair. The objective of this study was to assess the agreement of posttetanic count including agreement of neuromuscular blockade status (intense block; posttetanic count = 0 or deep block; posttetanic count ≥ 1 and train-of-four count = 0) between acceleromyography and electromyography.

Thirty-six patients, aged 20–65 years, participated in this study. Rocuronium 0.6 mg/kg, with additional dose of 0.3 mg/kg if required, was administered to the patients. The train-of-four and posttetanic counts were monitored in the contralateral arm using electromyography at the first dorsal interosseus or adductor pollicis, and acceleromyography at the adductor pollicis. Posttetanic count measurements were performed at 6 min intervals; the responses were recorded until the train-of-four count reached 1. We evaluated the agreement of degree of neuromuscular blockade (intense or deep block) and that of posttetanic count between acceleromyography and electromyography.

We analyzed 226 pairs of measurements. The percentage agreement indicating the same neuromuscular blockade status (intense or deep block) between acceleromyography and electromyography was 73%. Cohen’s kappa coefficient value was 0.26. After excluding data with acceleromyography-posttetanic counts over 15, 184 pairs of posttetanic counts were used to evaluate the agreement between the two monitoring methods. For acceleromyography-posttetanic count, 42 (23%) pairs had the same electromyography–posttetanic count, and 93 (50%) pairs had more than the electromyography–posttetanic count. The mean posttetanic count on electromyography was 38% (95% CI: 20% to 51%) lower than that on acceleromyography (P = 0.0002).

Acceleromyography frequently counted more twitches than electromyography in posttetanic count monitoring. Acceleromyography– and electromyography–posttetanic counts cannot be used interchangeably to assess the degree of neuromuscular blockade.