Relationship of post-tetanic count and train-of-four response during intense neuromuscular blockade caused by atracurium

Abstract

Atracurium-induced intense neuromuscular blockade was evaluated in 60 randomly selected patients using the post-tetanic count (PTC) and train-of-four (TOF) methods. Thirty patients were anaesthetized with thiopentone, nitrous oxide and halothane, and 30 patients received thiopentone, nitrous oxide and fentanyl. In all patients, the response to post-tetanic single twitch stimulation appeared before the response to TOF stimulation, and a close correlation was found between the number of post-tetanic twitches (PTC) and the time interval between the PTC and the first detectable TOF response. A PTC of zero indicated that the time to first response to TOF stimulation was always more than 8min. A PTC of 1 meant that the TOF response would appear in, on average, 9 min (95% confidence limits: 4-14 min). Halothane significantly prolonged the time from injection of atracurium to the first response to post-tetanic single twitch stimulation. It is concluded that the relationship between PTC and the time to first response to TOF nerve stimulation makes the PTC method a valuable supplement to TOF nerve stimulation for neuromuscular monitoring during clinical anaesthesia involving atracurium. © 1987 Copyright: 1987 British Journal of Anaesthesia.