不同液体中度和重度急性等容血液稀释对兔凝血功能和存活率的影响

目的:观察用乳酸林格氏液(lactated Ringer's solution, LR)、琥珀酰明胶液(4% succinylated gelofusin(R),GEL)、羟乙基淀粉液(6% hydroxyethyl starch 130/0.4,HES)进行中度、重度急性等容体内和体外血液稀释后,对兔凝血功能、存活率和存活时间的影响.方法:将雄性中国白兔30只随机分成3组,(1)乳酸林格氏液(LR)组(n=10);(2)琥珀酰明胶液(GEL)组(n=11);(3)羟乙基淀粉液(HES)组(n=9);将兔麻醉后经耳缘中动脉采集稀释前血样.体外稀释是在10mL注射器内用上述3种液体以倍比稀释至50%和75%(红细胞压积下降50%,75%);体内稀释是在股动脉放血同时,经耳缘静脉以同样速度输入上述3种液体(水浴至39℃)进行50%稀释,继而进行75%稀释(估计放出全身血量的50%,75%).稀释后每隔5 min记录平均动脉压、心率、体温;稀释完成30min后经股动脉采取血样,测定动脉血气、电解质、红细胞压积、凝血功能.凝血功能应用血栓弹性描计仪在37℃测定;观察稀释75%后1 h内动物存活率和存活时间.结果:(1)与稀释前比较,3种液体体内血液稀释50%时平均动脉压均下降,但稀释75%时明显下降(P<0.01);心率、体温变化不明显;体内稀释P(O2)上升,p(CO2)下降,稀释使Na+Ca2+下降,K+在稀释50%时下降,稀释75%时升高;体外稀释后pHa变化不明显,GEL组和HES组为高Na+,Ca2+和K+明显下降.(2)比较3种液体,体外稀释时,LR组凝血启动无影响,而GEL和HES组使凝血启动延长;体内稀释时,3种液体都可使凝血启动加速,但GEL和HES作用较弱.3种液体稀释在体内或体外都可使血块硬度降低.(3)兔在稀释75%后1 h内的存活率,比较LR(6/10),GEL(5/11)和HES(8/9),组间差异无统计学意义(x2=4.093,P>0.05);LR组、GEL组、HES组存活时间分别为(50.50±62.38)min,(324.55±777.32)min和(748.89±881.67)min,LR组与GEL组比较差异无统计学意义(t=0.243,P>0.5);HES组与GEL组比较差异有统计学意义(t=3.012,P<0.01),HES组与LR组比较差异有统计学意义(t=2.781,P<0.01).结论:3种液体体外稀释时凝血启动无变化或抑制,体内稀释时凝血启动加速或无变化,此差异提示尽管凝血物质被稀释,机体却存在未知的促进凝血启动的机制.HES可明显延长重度血液稀释兔的存活时间.

Effect of acute progressive normovolemic hemodilution with lactated Ringer's,gela-tin and hydroxyethyl starch on coagulation and survival rate in rabbits

OBJECTIVE: To observe acute progressive normovolemic hemodilution with lactated Ringer's, gelatins, and hydroxyethyl starch in vivo and in vitro on blood coagulation and survival rate and time in rabbits. METHODS: Thirty male Chinese white rabbits were randomly assigned to three groups that underwent acute progressive normovolemic hemodilution with one of three solutions: (1) lactated Ringer's solution (LR group, n=10). (2) 4% succinylated gelatin (GEL group, n=11), (3) 6% hydroxyethyl starch (HES group, n=9). After anesthesia, a 22-gauge catheter was placed in the central ear artery and blood samples were obtained before hemodilution. In vitro, 50% and 75% hemodilutions were completed by doubling the volume of blood sample with a 10 mL syringe in two times. In vivo, 50% and 75% (50%,75% of estimated blood volume removed) hemodilutions were performed by removing an equal volume of blood from a femoral arterial catheter, simultaneously administering the marginal ear vein as previous solutions (water warmed to 39 degrees C). Mean arterial pressure (MAP), heart rate (HR), and body temperature were measured and arterial blood samples were obtained after 30 min of equilibration to determine blood gas, electrolytes, hematocrit, and thrombelastography variables at 37 degrees C, after 75% hemodilution rabbits survival rates within 1 h and survival times were observed. RESULTS: MAP with progressive hemodilutions (50%, 75%) significantly decreased (P<0.01); However, HR and body temperature remained virtually unchanged. the p(O(2)) increased, the p(CO(2)) decreased,blood sodium and calcium markedly decreased with progressive hemodilutions (50%, 75%), Blood potassium decreased in 50% but increased in 75% hemodilution. In vitro pH values were found to be constant in three groups, p(CO(2)) and the blood sodium greatly increased within HES and GEL groups, and blood potassium and calcium throughout progressive hemodilution significantly decreased. In vitro hemodilution with the three solutions, initiation of coagulation was not affected or prolonged but the toughness of clot decreased. In vivo hemodilution, initiation of coagulation was accelerated or unchanged but also with decreased clot toughness. In comparing the three solutions, in vitro hemodilution with LR had no effect on initiation of coagulation but GEL and HES prolonged the procedure. In vivo hemodilution with the three replacement solutions accelerated the initiation of coagulation, making it more weakly in GEL and HES than in LR. Either in vivo or in vitro the three solutions could decrease the toughness of clot. The survival rates within 1 hour after 75% hemodilution were not significantly different among LR(6/10), GEL(5/11) and HES(8/9) groups(chi(2)=4.093,P>0.05), survival times of the LR, GEL and HES groups were (50.50+/-62.38) min,(324.55+/-777.32) min,(748.89+/-881.67) min, respectively. The difference between LR and GEL survival times was nonsignificant (t=0.243,P>0.05), the average survival time of HES solutions was longer than that after LR or GEL infusion (t=3.012,P<0.01 and t=2.781,P<0.01, respectively). CONCLUSION: With in vitro hemodilution, the initiation of coagulation is unaffected or decreased. However with in vivo hemodilution, initiation of coagulation is accelerated or unchanged. The discrepancy between in vivo and in vitro hemodilution, indicates an unknown internal mechanism to promote initiation of coagulation. Hemodilution makes the toughness of clot soften. and the longest survival time in profound hemodilution associated with hydroxyethyl starch.