Clinical Study of Post - tetanic Count ( PTC ) during Vecuronium - induced Intense Neuromuscular Blockade

Hwang, Kyung Ho; Kim, Sung Yel

Abstract

Vecuronium induced intense neuromuscular blockade was evaluated in 40 USA class l, ll adult patients using the post tetanic count (PTC) and train-of-four(TOF) methods. All patients were anesthetized with thiopental sodium, nitrous oxide(50%), and enflurane(1~2%). Neuromuscular monitoring commended immediately after administration of thiopental sodium. The ulnar nerve was stimulated using surface electrodes and the mechanical response of the adductor policis muscle recorded using the Acclograph, neuromuscular transmission monitor. TOF nerve stimulation was used every 15s. After supramaximal stimulation was achieved a bolus of vecuronium 0.1mg/kg was injected intravenously. The traches was intubated when TOF response was depressed to 95% or above to control twitch height and the lungs ventilated with a tidal volume of 10ml/kg and a rate of 14 b.p.m. The patients were allocated randomly to two groups of 20 patients each. Patients in control group were allowed to recover TOF response spontaneously, and in PTC group were applied tetanic stimulation(50Hz for 5s) at 7 minutes intervals during no TOF response. In PTC group, the tetanic stimulation was preceded by a 30s period of 1Hz stimulation on each occasion, which was continued after the 3s pause. Duration of no TOF response in each group, and relationship between first post tetanic twitch height of PTC and time to first reaction to TOF nerve stimulation in PTC group were measured. In the results, duration of no TOF response was shortened by tetanic stimulation(p<0.01). There was a close inverse correlation between first post tetanic twitch height or PTC and time to first reaction to TOF nerve stimulation (p<0.01). It was concluded that PTC method appeared to be a valuable supplement to TOF nerve stimulation in assessment and trend for vecuronium induced intense neuromusclular blockade.