The Influence Of Anesthesia Depth On The Brain Injury During Cardiopulmonary Bypass

Objective: To discuss the influences of different depth of anesthesia monitoring by bispectral index(BIS) on brain injury during cardiopulmonary bypass(CPB).Methods: Forty-five patients of both sexes, aged 26-68 years, ASAⅢorⅣundergoing elective cardiac valve replacement surgery with CPB were included in this study. Patients were randomly divided into three groups: the dosage of propofol during CPB was adjusted to achieve a BIS level of 30～40 in group A, 40～50 in group B,50～60 in group C. Anesthesia induction was induced by lidocaine 0.5mg/kg, midazolam 0.1mg/kg , sufentanil 1μg / kg, etomidate 0.3mg/kg and rocuronium1mg/kg then tracheal intubation and keeping PETCO₂ 35～45mmHg by mechanical ventilation. Bispectral index (BIS), the arterial pressure (MAP), electro-cardiogram (ECG), heart rate(HR), central venous pressure (CVP), pulse oxygen saturation(SpO₂), end-tidal CO₂ partial pressure (PETCO₂),and nasopharynx (NPT) were continuously monitored during operation. Jugular bulb vein and artery blood were drawn following 4 time points: before CPB (Tl), 30min after CPB (T2), immediately at the end of CPB (T3),1h after the end of CPB(T4). Levels of S-100βprotein and cerebral oxygen metabolism indicators were evaluated at every time point. Standard neurological examination MMSE score made in the preoperative and postoperative 24 hours. SPSS17.0 software was used for statistical analyses. Data was express mean±S.D. Statistical significance of difference between and within groups was evaluated by one-way analysis of variance and P<0.05 was considered as statistical significance.Results:1,The dosage of propofol per hour is higher in group A and group B than in group C , where it is higher in group A than group B(P<0.05).2,At T2, the SjvO₂ in three groups were significantly increased(P <0.01),and then decreased. Compared with T₁, there were no significantly differences in SjvO₂ at T3 and T4 (P> 0.05). At T2, the SjvO₂ in group A and group B were higher than that in group C (P<0.05),and it was higher in group A than that in group B (P<0.05). At T2, the AVDO₂ and CEO₂ in three groups were significantly decreased (P <0.01), and then increased. Compared with T₁, there were no significantly differences in AVDO₂ and CEO₂ at T3 and T4 (P> 0.05). In group A and B, the AVDO₂ and CEO₂ at T2 were lower than those in group C (P<0.05), and they were lower in group A than those in group B(P<0.05). Comparing with T₁,the concentrations of LA and LV were all increased significantly more at T2,T3,T4, (P<0.05). At T3, the concentrations of LA and LV in group A and B were lower than those in group C (P<0.05), and they were lower in group A than those in group B (P<0.05). Compared with T₁, the AVDL in three groups at T2 were significantly decreased (P <0.01), and then increased, but there were no significantly differences in the AVDL at T3 and T4 (P> 0.05). In group A and B, the AVDL at T3 were lower than those in group C (P<0.05), and it was lower in group A than that in group B(P<0.05).3,Comparing with T₁, the concentration of serum S-100βprotein were all increased significantly more at T2,T3,T4, (P<0.05).The peak value was measured at T3. Comparing in three groups, there were no significantly differences in the concentration of serum S-100βprotein before CPB (P>0.05). In group A and B, the concentrations of S-100βwere significantly lower at T3 and T4 than those in group C(P<0.05),and it was significantly lower in group A than that in group B(P<0.05).4,MMSE scores in three groups after 24 h operation were all lower than those before operation, but there were significantly difference in three groups(P<0.05); In group A and B ,the scores after 24 h operation were significantly higher than those in group C, and they were significantly higher in group A than those in group B (P<0.05).Conclusion:1. The depth of anesthesia has some influences on the brain injury caused by CPB. To certain extent , regulating the depth of anesthesia can reduce brain damage during CPB. Deeper anesthesia may have brain protection effect.2. BIS monitoring may be used to assess the depth of anesthesia effectively as well as to prevent brain injury during CPB.