Comparison of hypnotic effects of propofol administered by target-controlled infusion during daytime and nighttime / 中华麻醉学杂志

ABSTRACT

Objective To compare the hypnotic effects of propofol administered by target-controlled infusion (TCI in daytime and nighttime,in order to explore the effect of circadian rhythm on the sedative effect of propofol.Methods Sixty-five male ASA Ⅰ or Ⅱ patients,aged 18-55 years,with the body mass index (BMI) of 18.5-24.9 kg/m2,undergoing emergency minor hand surgery were divided into two groups according to the time of the day when they received TCI of propofoldaytime group (from 0701 to 1900) and nighttime group (from 1901 to 0700).The pharmacokinetic parameters proposed by Schnider et al.which suggested the effect-site concentration (Ce) was used.Four Ces of propofol were set at 0.8,1.2,2.0 and 4.0 μg/ml,respectively.Ce was increased step by step and each Ce was maintained for 5 minutes.The level of sedation at each Ce was assessed by bispectral index (BIS) and observer's assessment of alertness/sedation (OAA/S) scores.BIS values and Ces of propofol were recorded and compared between the two groups when the patients lost consciousness (OAA/S score =2).Results There were 28 and 30 patients in daytime and nighttime groups,respectively.When Ces were 1.2 and 2.0 μg/ml,the BIS values were significantly lower in the nighttime group than in the daytime group.There was no significant difference in BIS values between the two groups when Ces were 0.8 and 4.0 μg/ml.When the patients lost consciousness (OAA/S =2),the BIS value was comparable between the two groups,but Ce was significantly lower in the nighttime group than in the daytime group.Conclusion The hypnotic effect of propofol is greater during night time than during day time.