不同程度急性等容量血液稀释对家兔血清S-100B蛋白浓度和脑氧代谢的影响

目的 探讨常温下不同程度急性等容量血液稀释(ANH)对家兔血清S-100B蛋白浓度和脑氧代谢的影响.方法 健康成年家兔32只,体重2～2.5 kg,随机分为4组(n=8),对照组(Ⅰ组)不行血液稀释;其余3组血液稀释的目标红细胞压积(Hot)分别为24%(Ⅱ组)、18%(Ⅲ组)、12%(Ⅳ组).麻醉下气管插管后行机械通气,维持体温37℃左右.左颈动脉和左颈内静脉穿刺并置管,用于监测血压、采血和血气分析.右颈内静脉穿刺并置管,用于监测中心静脉压.股动脉放血,同时Ⅱ组～Ⅳ组股静脉经30 min输注等量6%羟乙基淀粉200/0.5行ANH至目标Hct.于动脉、静脉穿刺并置管稳定20 min(To)、ANH后2、4、8 h(T1～T3)时,记录血液动力学指标;分别采集左颈动脉和左颈内静脉血样各0.1 ml,行血气分析,计算脑氧摄取率(CERO2);颈动脉取血样,采用ELISA法测定血清S-100B蛋白浓度.ANH后8 h时处死动物,取右侧脑组织,称湿重和干重,计算脑含水量.结果 与T0时比较,Ⅲ组T3时、Ⅳ组T1～T3时CERO2和血清S-100B蛋白浓度升高(P<0.05);Ⅰ组和Ⅱ组各时点CERO2和血清S-100B蛋白浓度比较差异无统计学意义(P>0.05);与Ⅰ组和Ⅱ组比较,Ⅲ组T3时、Ⅳ组T1～T3时CERO2和血清S-100B蛋白浓度升高(P<0.05);与Ⅲ组比较,Ⅳ组T1～T3时CERO2和血清S-100B蛋白浓度升高(P<0.05).各组问脑含水量比较差异无统计学意义(P>0.05).结论 常温下ANH目标Hct为24%时,对家兔脑氧代谢无影响;目标Hct≤18%时,发生脑氧代谢失衡和脑损伤.

Effects of different degrees of acute normovolemic hemodtiution on serum S-100B protein concentration and cerebral oxygen metabolism in rabbits

Objective To investigate the effects of different degrees of acute normovolemic hemodilution (ANH) with 6% HES 20010.5 on serum S-100B protein concentration and cerebral oxygen metabolism at 37℃ in rabbits.Methods Thirty-two adult rabbits weighing 2.0-2.5 kg were randomly assigned into 4 groups (n = 8each) : Ⅰ control group underwent no ANH and Ⅱ , Ⅲ , Ⅳ ANH group underwent ANH with hematocrit (Hct)reduced to 24%, 18% and 12% respectively. The animals were anesthetized with iv 20% urethane 5 ml/kg,tracheostomized and mechanically ventilated (VT = 15 ml/kg, RR = 30 bpm). The body temperature was maintained at 37℃. Left carotid artery and jugular vein were cannulated for BP monitoring, blood gas analysis and blood sampling. Right jugular vein was cannulated for CVP monitoring. Left femoral artery and vein were cannulated for hemodilution. Blood withdrawn from femoral artery was simultaneously replaced by iv infusion of equal volume of HES (200/0.5) until the target Hct was achieved. Hemodynamics parameters, were recorded and blood gases were analyzed and serum S-100B protein concentration and cerebral O2 metabolic rate (CERO2) were determined before (baseline) and at 2, 4 and 8 h after ANH. Brain water content was measured by wet/dry brain weight ratio. Results There were no significant differences in serum S-100B protein concentration, CERO2 and pH value between group Ⅰ and group Ⅱ (Hct 24%). Serum S-100B protein concentration and CERO2 were significantly increased at 8 h after ANH as compared with the baseline before ANH in group Ⅰ (Her 18%). Serun S-100B protein concentration and CERO2 were significantly increased at 2, 4 and 8 h after ANH as compared with the baseline before ANH in group Ⅳ (Hct 12%). There was no significant difference in brain water content among the 4 groups. Conclusion ANH does not affect cerebral O2 metabolic when Hct is reduced to 24%. CERO2 can not be sustained and ischemic cerebral injury may occur when Hct is reduced to≤18%.