Half-effective Target Plasma Concentration Of Propofol For Respiratory Depression In Different Gender And Different Age Patients

Objective: To determine the Half-effective target plasma concentration of propofol for respiratory depression in different gender and different age patients and evaluate the depth of anesthesia by BIS.Methods: Eighty ASAⅠorⅡpatients aged 40~80 yrs undergoing general anesthesia were enrolled in this study. Their body mass index (BMI) was 18~25 kg·m-2. Patients who was hypersensitiveness to eggs were excluded and no premedication was administered. The patients were divided into adult male group and adult female group (40~60 yrs:MA or FAgroup) and older male group and older female group group (>60 yrs: MO or FO group). An IV cannula was inserted into an antecubital vein and lactated Ringer's solution 5ml/kg (over 15~20min), followed by an infusion at 10 ml·kg-1·h-1, was administered. Patients breathed spontaneously 100% oxygen at a total gas flow rate of 3L/min, via a close-fitting facemask. The ECG, noninvasive blood pressure, heart rate, pulse oxyhaemoglobin saturation, bispectral Index of the electroencephalogram (BIS), end-tidal carbon dioxide partial pressure, tidal volume, respiratory frequency were monitored continuously throughout the study. A target-controlled infusion of propofol using the Marsh pharmacokinetic data set was then commenced at a target determined by the response of the previous patient in the same group (the Dixon up-and-down method). The target propofol blood concentration in the first patient in each group was set to 3μg/ml. Subsequent target concentrations were increased or decreased by 0.5μg/ml, on the basis of the response of the previous patient in the same group. Time was allowed for effect-site concentration to equal target blood concentration. A positive response was recorded if the patient was in respiratory depression state. (respiratory rate≤8 breaths/min and/or VT≤5ml/kg and/or an end-tidal PaCO2≥50 mmHg and/or oxyhaemoglobin saturation≤94% and/or apnea≥15s was considered evidence of respiratory depression. ) At this time or fifteen minutes later, the study was complete. The anesthetic was then allowed to proceed according to the needs of the patient and surgery was commenced. Noninvasive arterial blood pressure, Heart rate and BIS value just before experiment finished, the BIS value after the onset of experiment 1min, 3min were recorded. The Cp50 and confidence interval of each group was Calculated.Results: the Cp50 of propofol for respiratory depression was 4.3μg/ml (95% CI 3.5～5.2μg/ml) in FO group, 4.5μg/ml(95% CI 3.3～6.2μg/ml)in MO group, 5.9μg/ml (4.4～7.8μg/ml)in FA group, 6.3μg/m(l95% CI 5.4～7.4μg/ml)in MA group. Cp50 was significantly shorter in older group than in adult group(P < 0.05). No significant differences existed between the male and female patients with respect to Cp50. SBP, DBP decreased significantly after infusion of propofol (P < 0.05). BIS1min, BIS3min, BISfinish decreased significantly (P < 0.05).Conclusion: Olders are more sensitive to propofol than adults. No significant difference exists between the male and female patients with respect to Cp50 of propofol for respiratory depression.