Atropine enhances neuromuscular transmission in humans

The effect of atropine (1-10 micrograms . kg-1) on neuromuscular transmission in humans was studied by analysing its effects on the amplitude of indirectly-elicited twitch (0.2 Hz) and tetanic (50 and 100 Hz for 1 s duration) contractions. Six patients, free from any neuromuscular disorders, undergoing orthopaedic surgery, were included in the present study. The patients received either no premedication or the oral benzodiazepine, temazepam, 30 mg 1-2 h pre-operatively. Anaesthesia was induced with propofol (1-2 mg . kg-1, i.v., over 20 s). The patients breathed no less than 30% oxygen in nitrous oxide, halothane (1%) or enflurane (1-2%). Incremental doses of fentanyl (50-100 micrograms) were given to provide additional analgesia. The ulnar nerve was stimulated, supramaximally, at the wrist, and control mechanical responses of the adductor pollicis muscle, to nerve stimulation at 50 and 100 Hz for 1 s duration, were recorded. Theses responses were repeated at 2, 5 and 10 min intervals, after injection of atropine (1-10 micrograms . kg-1). At the same time, heart rate and blood pressures (systolic and diastolic) were recorded. The results showed that atropine enhanced the tetanic contractions, elicited at 50 and 100 Hz for 1 s duration, by 27 +/- 1.2% (50 Hz and atropine, control 220 +/- 13 g tension), and by 43 +/- 7% (100 Hz and atropine, control 333 +/- 26 g tension) at the 5 min intervals (mean +/- S.E., n = 6).(ABSTRACT TRUNCATED AT 250 WORDS)