Assessment of the Optimal Interval of Tetanic Stimulation for Post-Tetanic Count

Han, Jeong Uk; Kim, Kyo Sang

Abstract

Post-tetanic count(PTC) was a known monitoring method to evaluate intense neuromuscular blockade of peripheral muscles. It has been reported that intermittent tetanic stimulation(50 Hz for 5 sec.) every 6 to 10 min. during intense nondepolarizing neuromuscular blockade did not influence the recovery of neuromuscular transmission. However, the relatively frequent use of tetanic stimulation might be possible to influence the recovery of neuromuscular blockade and the repeated stimuli might result in a false recovery state. The purpose of this study was to determine the best interval time of tetanic stimulation for evaluation of the correct PTC. Sixty adult patients undergoing stomach operations were randomly allocated to three groups according to the interval of tetanic stimulation ; group 1 (6 min. n=20), group 2 (8 min. n=20) and group 3 (10 min. n=20). In all cases, Anesthesia was maintained with 50% nitrous oxide, 50% oxygen and 1-2% enflurane following induction of anesthesia with thiopental sodium 3-5 mg/kg. Neuromuscular block was achieved by intravenous pancuronium bromide 0.13 mg/kg before application of ulnar nerve stimuli using Myotest MKII. The adduction force of the resultant thumb twitch was measured by the acceleration of a small piezo-electric ceramic wafer with electrodes of Mini-accelograph and recorded by Datascope 2200 I After 1 Hz single twitch stimulation, a tetanic stimulus(50 Hz) was applied for 5 sec. Three seconds later, the single twitch stimulation was again applied for 1 min. followed by 1 min. of TOF stimulation. This pattem of tetanic stimulation was continued by the interval of 6, 8 and 10 min. The results were as follows: 1. The continuance (which was the percentage when PTC was continuously increased, not intermittently reduced) was 73.7% in group 1 and 2, but 100% in group 3 and there were statistically significance. 2. In the regression analysis between FI'C and time from PTC1, we yielded the following equations ; Y=10+3.5X (r(2)=0.71) for group 1, Y=8.6+4.1X (r(2)=0.78) for group 2 and Y=9.8+5.7X (r(2)=0.69) for group 3. The slope and intercept of the line of group 3 showed significantly different to that of group 1 and 2 (p<0.001). The more frequent tetanic stimulation reduced the time to arrive the same PTC. 3. The time from PTCl to TOFl was 51.6+/-3.9 min. in group 1, 65+/-5 min. in group 2 and 69+/-4.3 min. in group 3. There were no statistically significance, but they had trend to reduce by more frequent tetanic stimulation. 4. PTC was 12.9+/-0.9 in group 1, 14.9+/-1.5 in group 2 and 13.2+/-0.8 in group 3 when TOF1 was appeared, and 38.3+/-2.3 in group 1, 33.3+/-2.3 in group 2 and 32.4+/-2.6 in group 3 when the second response to TOF stimulation(TOF2) was recorded(meanSEM). There were no statistically significance. With the above results the authors concluded that 10 min. will be the optimal interval of the tetanic stimulation for the correct PTC, and recognized that the interval of tetanic stimulation was not related to the time from PTC1 or PTC at TOF twitches.