| Objective:The purpose of this study was to assess the effectiveness of cardiopulmonary bypass on the plasma propofol concentraition and examine the relationship of plasma propofol concentration, mean arterial pressure and temperature to Bispectral Index (BIS) as an index of conscious level during cardiopulmonary bypass.Method:Thirty ASAⅡ-Ⅲpatients aged 20-55 years and weighted 40-70kg were randomly divided into two groups,C3 group was received 3mg/kg/h propofol constant infusion, C6 group was received 6mg/kg/h propofol constant infusion. Patients were anesthetized with midazolam 0.05mg/kg, fentanly 5μg/kg, vecurium 0.15mg/kg, propofol 0.5-1.0mg/kg, and mornitored the BIS value and the MAP,T,HR and PETCO2. Before sternotomy,the infushion rate of propofol was 10mg/kg/h, after that the rate was adjusted to the aim rates. At the same time, giving fentanly (4μg/kg/h) and vecurium (0.1mg/kg/h) through constant infusioning. The priming volume of the system consisted of 1.0 litre of Gelofusine, 500 ml of Ringer, with100ml of 20% mannitol.Intraoperative data and total plasma propofol concentration were measured at To (after heparining about 10 minutes),T1 (30 minutes after CPB),T2 32℃,T3 34℃,T4 36℃and T5(10 minutes after rewarming,about 37℃).The 2ml blood samples were collected through the radial artery, each sample was centrifuged for 10 min at 3000 r/min to separate plasma and then used immediately for measurement of protein binding. The remaining part of the sample was stored at-70℃until analysis. We used the HPLC to determine the plasma propofol concentration.Results:1. The differences between the age,gender,premedication and operation time of the two groups were not significant(P>0.05). And the results were:the plasma propofol concentration of the two groups had changed.(1).After hemodilution the propofol concentration was obviously lower at T1,T2,T3,T4 and T5 than that at T0(P<0.05).In C3 group,the plasma propofol concentration decreased from 2.4±0.5μg/ml to 1.4±0.3μg/ml,and in C6 group,it decreased from 3.0±0.6μg/ml to 2.2±0.6μg/ml.(2).During the period of hemodilution the plasma propofol concentration was stable.There was no significant difference after hemodilution(P>0.05) among T1,T2,T3 andT5.And at the T4,the plasma propofol concentration reach to a peak concentration during the CPB.(3).After rewarming to 36℃about 10 minutes, the plasma propofol concentration decreased significantly from T4 to T5.2. The correlation between BIS value and the MAP of C6 group was insignificant (P>0.05), BIS value showed a weak correlation with the MAP of C3group (r=0.308,P<0.01);3. BIS value showed a moderate correlation with the temperature of C6 group(r=0.445,P<0.01) BIS value showed a moderate correlation with the temperature of C3 group (r=0.685,P<0.01).Conlusion:1.The hemodilution in CPB decreased the plasma propofol concentration significantly.During the rewarming period, the 36℃as the critical point, the plasma propofol concentration increased first and then decreased significantly.2. During the rewarming period, C6 group was better than C3 group for inhabiting the influence of mean arterial pressure on the BIS value. 3. During the rewarming period, the temperature influnced the BIS value significantly, we should control the rate of the rewarming,and adjust the rate of the infusion in time so that we could avoid the awareness occurring. |
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