• Lian Yun Li and Xing Xu.
• Department of Anesthesiology, Peking University First Hospital, Beijing, China.
• Beijing Da Xue Xue Bao. 2008 Jun 18;40(3):292-300.

ObjectiveTo 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.MethodsThirty 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.ResultsMAP 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).ConclusionWith 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.

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