Master of Science
Health Related Sciences
Twenty ASA class I and II patients between the ages of 15 and 64 years undergoing surgical procedures requiring neuromuscular blockade and general anesthesia were selected at random to participate in this study. Patients taking medication known to interfere with neuromuscular blockade were excluded. All patients were given 2 mg of midazolam IV as a premedication. In the operating room, routine monitors were connected and baseline blood pressure, pulse and respirations were recorded with subsequent recordings at 5 and 10 minutes following induction of anesthesia.
Indirect stimulation of the ulnar nerve was achieved by placing ECG electrodes 2 cm and 10 cm proximal to the distal end of the ulnar nerve. The same type ECG electrodes were used at the orbicularis oculi muscle group. One electrode was placed 2 cm lateral and 2 cm caudal to the outer canthus of the eye and the second 2 cm caudal to the first.
Induction of anesthesia was achieved with mivacurium 0.1 mg/kg IV followed by fentanyl 100 mcg IV and propofol 2 mg/kg IV. The second dose of mivacurium 0.1 mg/kg was administered 30 seconds after the initial dose. Baseline twitch response was started at both monitoring sites using 1 Hz twitch mode with an output of 60 mA. Each patient was monitored until there was a loss of twitch response at either of the two sites. When the twitch response was suppressed at one site, the anesthetist performed direct visual laryngoscopy. If the vocal cords were open, the trachea was intubated. The time of twitch suppression at the second site was also recorded. The data collected from the study was examined using a paired t-test and a comparison of the mean times to loss of twitch at the orbicularis oculi and the adductor pollicis was made. All 20 of the subjects lost the orbicularis oculi motor response to stimulation prior to the loss of motor response to stimulation at the adductor pollicis. The mean time to loss of twitch response was 85 seconds at the orbicularis oculi and 230 seconds at the adductor pollicis.
It was concluded that there is a shorter time to loss of twitch response at the orbicularis oculi than at the adductor pollicis using 0.2 mg/kg mivacurium chloride in equally divided doses given 30 seconds apart.
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