急性高容血液稀释对犬血脑屏障受损后颅内压和脑组织含水率的影响

Effect of acute hypervolemic hemodilution on ICP and brain tissue water content after blood-brain barrier injury in dogs

目的 研究在血脑屏障(BBB)开放后极端条件下急性高容血液稀释(AHH)对颅内压(ICP)和脑组织含水率的影响。方法 健康杂种犬29只,气管插管机械通气。随机分成四组;A组(对照组,n=2):机械通气60min后处死;B组(BBB完整AHH组,n=10):6％羟乙基淀粉50ml/kg,AHH 60min后处死;C组(BBB开放AHH组,n=10):麻醉后开放BBB,AHH 60min后处死;D组(BBB开放组,n=7):不行AHH,开放BBB 60min后处死。比较CVP、MAP、HR、ECG、ICP和脑组织含水率指标并在光镜下检查脑组织和细胞形态学。结果 B、C组Hct值范围分别由(37±3)％、(36.9±3.7)％降到(19.8±2.8)％、(22.9±2.1)％。A、B组ICP未见明显变化。C、D组AHH后ICP分别由(9.8±2.9)、(10.5±2.0)mmHg降为(8.2±1.7)、(6.5±1.7)mmHg。脑组织含水率四组极为接近,A～D组AHH和BBB是否开放对其未见明显影响。光镜下的形态学分析显示,A、B组无明显细胞变性,C组神经元细胞轻度水肿变性,D组神经元细胞变性较重伴轻度水肿。结论 应用6％羟乙基淀粉AHH对ICP没有显著影响,即使在BBB完全开放的情况下。当BBB开放后,AHH可致神经元和胶质细胞一定程度的损害,故重度颅脑外伤等因素引起脑血流自动调节机制不全时进行AHH应谨慎。

Objective To study the effect of AHH on ICP and brain tissue water content (BTWC) after blood-brain barrier(BBB) injury. Methods 29 anesthetized and mechanically ventilated healthy dogs were allocated into one of four groups randomly. The animals in group A with no special treated were killed after ventilation for 60 min,in group B with BBB normal and acute hemodilution (AHH) were given 6% HEAS 50 ml/kg,and killed 60 min later,in group C with BBB opened by 20% mannitol 4 ml/kg and AHH were given and killed as in group B,in group D with BBB opened only were killed as in group B.ICP,MAP,HR,ECG,CVP and BTWC were recorded and brain tissue morphological examination was done by optical microscope. Results Hct in group B and C decreased from (37±3)% and (36.9±3.7)% to (19.8±2.8)% and (22.9±2.1)% respectively. No significant changes in ICP were found in group A and B. ICP in group C and D,however, was significantly descented from (9.8±2.9),(10.5±2.0) mmHg to (8.2±1.7),(6.5±1.7) mmHg after AHH respectively. The measurements of BTWC were very close in four groups. A slight cellullar edema was seen in group C and slight edema with severe cellullar degeneration in group D. Conclusion AHH with 6% HEAS has no effect on ICP remarkably, whether BBB is opened or not. So does the brain edema due to the increase of intercellular and intracellular fluid. The morphological injury of the neurocyte and gliocyte may take place after AHH when BBB is opened. Caution should be taken when AHH is used in the patients with malfunctioned brain blood flow autoregulation.