The physiological and behavioral evaluation of patient-control sedation

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Methods : Prior to this study, written informed consent was obtained from each of the 32 subjects. They were randomly assigned to receive bolus injections of 0.075 mg/kg midazolam : group M (n=7) ; 0.7 mg/kg propofol : group P0.7 (n=15) ; or 1.0 mg/kg propofol ; group P1.0 (n=10). The changes in grip were measured by digital hand-dynamometer for 60 minutes after injection of midazolam, 30 minutes after propofol. After the control value for the grip and the EMG activity of the superficial flexor muscles of the fingers were determined, the subject received a bolus injection of designed drug for 2 minutes. And the sedative condition of the subject was evaluated by subjective and objective sedation scales. Duringexperiment, heart rate, blood pressure, respiratory rate and SpO_2 were measured. These data were analyzed using paired t-test, with p<0.05 considered statistically significant.Results : Compared to the control value for the grip, the average value in Group M decreased significantly from 0 min (75%) till 30 min (83%) after midazolam injection. The value in Group P0.7 decreased significantly at 1 min (83%) and 3 min (85%) after 0.7 mg/kg propofol injection. The value in Group P1.0 decreased significantly from 0 min (74%) till 15 min (83%) after 1.0mg/kg propofol injection. Four subjects in the group P1.0 could not grip the digital hand-dynamometer at all at 1 min after 1.0mg/kg propofol injection due to the depth of their sedation. Severe changes were not observed in heart rate, blood pressure, respiratory rate and SpO_2.Conclusion : The results suggest that a value for grip that indicates adequate sedation is below 80% of the control value and that the lockout time of PCS should be 30 minutes after bolus injection of 0.075 mg/kg midazolam, 3 minutes after that of 0.7 mg/kg propofol. Bolus injection of 1.0 mg/kg propofol appears to be inappropriate for patient-controlled conscious sedation.