Effects Of Different Fluids On Microcirculation And Inflammatory Factors In Rabbits With Hemorrhagic Shock

Objectives:To study the effects of different types of fluid resuscitation on mesenteric microcirculation and inflammatory factors in rabbits with hemorrhagic shock.Methods:Forty-eight healthy male rabbits were randomly divided into 6 groups（n=8 each）according to the type of resuscitation fluids:control group,normal saline group,lactate Ringer group,acetate Ringer group,hydroxyethyl starch group and succinyl gelatin group.After intravenous anesthesia,tracheotomy was performed and endotracheal tube was placed in each group.The common carotid artery and internal jugular vein were isolated from the side of the rabbit’s neck:the common carotid artery was catheterized for invasive arterial pressure measurement and exsanguination,then the basal mean arterial pressure and heart rate were recorded;The internal jugular vein was catheterized for fluid resuscitation.The mesentery was pulled out,and the microcirculation of the mesentery was monitored by a microcirculation monitor after laparotomy.The hemorrhagic shock model was established by exbleeding from the common carotid artery,which caused the mean arterial pressure to decrease by 40%compared with the basal value,and the blood volume was recorded.After 60 minutes of shock observation,fluid resuscitation was initiated.The control group did not undergo liquid resuscitation,and the experiment was finished after 90 minutes of observation.Rabbits in the normal saline group,Ringer lactate group and Ringer acetate group were respectively injected with normal saline,lactated Ringer’s solution and acetated Ringer’s solution at a uniform speed within 30 minutes,and the infusion volume was three times the blood loss.In addition,rabbits in the hydroxyethyl starch and succinyl gelatin groups were injected with hydroxyethyl starch solution and succinyl gelatin solution at the uniform rate,and the amount of infusion was equal to the amount of blood loss.After liquid resuscitation completed,the resuscitated rabbits were observed for 1 hour and then the experiment was finished.The animals were killed by air embolization after the experiment.Observation index:The weight of the rabbits was recorded before the experiment;And Mean arterial pressure（MAP）,heart rate（HR）,proportion of microcirculation perfusion vessels（PPV）and microvascular blood flow index（MFI）were recorded before bleeding（T0）,at the time of hemorrhagic shock（T1）,at the beginning of fluid resuscitation（T2）,at the completion of fluid resuscitation（T3）and at the end of the experiment（T4）.At the time of T₀,T₂and T₄,rabbit blood was extracted and centrifugated,and the upper serum was taken and stored in the refrigerator at-80℃.Subsequently,tumor necrosis factor-α（TNF-α）,interleukin-1（IL-1）and lactic acid（Lac）were determined by enzym-linked immunosorbent assay（ELISA）;Then we recorded the amount of bleeding,urine volume and resuscitation fluid volume of rabbits after the experiment.Results:1.The results of comparison for general conditions:there were no significant differences in body weight and blood release volume among all groups（P>0.05）.And the urine volume of experimental control group was significantly different from that of other groups（P<0.05）.The infusion volume of the normal saline group,lactate Ringer group and acetic Ringer acetate group was equal to 3 times the volume of blood loss,and the infusion volume of hydroxyethyl starch group and succinyl gelatin group was equal to the volume of blood loss.2.The results of comparison for vital signs:comparison within groups:MAP decreased at T₁,and the differences in MAP between T₁and T₀of each group were statistically significant（P<0.05）;Similarly,there were no significant differences in MAP between T₂and T₁among all groups（P>0.05）;There was no significant difference in MAP between T₃and T₂in control group（P>0.05）,but were significant differences between T₃and T₂in other groups（P<0.05）;In addition,there was a difference in MAP between T₄and T₃in normal saline group（P<0.05）,while no statistically significant differences between T₄and T₃in the other groups（P>0.05）.Comparison among groups:Differences in MAP were not significant among all groups at T₀,T₁and T₂（P>0.05）;And the MAP difference between lactate Ringer group and hydroxyethyl starch group at T₃time was statistically significant（P<0.05）;At T₄,the differences in MAP between experimental control group and other groups were statistically significant（P<0.05）,and the differences between lactate Ringer group,normal saline group and hydroxyethyl starch group were statistically significant（P<0.05）.In addition,There were no statistically significant differences in heart rate between groups or at different time points3.The results of comparison for microcirculation indicators:comparison within groups:at T₁,PPV and MFI decreased significantly after hemorrhagic shock,and the differences in PPV and MFI between T₁and T₀were statistically significant（P<0.05）;Differences in PPV and MFI in the control group were little significant at T₁,T₂and T₄（P>0.05）;At T₂,the PPV and MFI levels of all groups were still low,and there was no difference between T₂and T₁（P>0.05）;At T₃moment,PPV and MFI were significantly increased in all groups after effective fluid resuscitation,except for the control group,and the differences with T₂were statistically significant（P<0.05）;At T₄,PPV and MFI still maintained high levels,and there was no statistical significance in T₄and T₃among all groups（P>0.05）.Comparison among groups:Comparison among groups:there were no differences in PPV and MFI among all groups at T₀,T₁and T₂（P>0.05）;At T₃,there were statistical significances between all groups and experimental control group（P<0.05）;At T₄,there were statistical significances between all groups and experimental control group（P<0.05）.At T₄,The levels of PPV and MFI in colloid group were higher than those in crystal group:the PPV in hydroxyethyl starch group and succinyl gelatin group were significantly different from those in saline group,lactate Ringer group and acetate Ringer group group at T₄（P<0.05）.In addition,The MFI of hydroxyethyl starch group and succinyl gelatin group were significantly different from that of normal saline group and lactate Ringer group at T₄（P<0.05）.4.The results of comparison for inflammatory factors:Comparison within groups:TNF-αwas significantly increased in all groups at T₂compared with T₁,and the differences between T₂and T₀were statistically significant（P<0.05）;IL-1 was slightly increased in all groups at T₂,and there were no statistically significant differences between T₂and T₀（P>0.05）;At T₄,TNF-αand IL-1 continued to increase in all groups,and there were no statistical significance in TNF-αand IL-1 between T₄and T₂（P>0.05）.Similarly,There were no significant differences in the levels of TNF-αand IL-1 between the groups at T₀,T₂and T₄（P>0.05）.5.The results of comparison for lactic acid:comparison within the group:the concentration of lactic acid at T₂was significantly higher than that at T₀,and the differences were statistically significant（P<0.05）;At T₄,the lactic acid of all groups except experimental control group decreased compared with that of T₂,and the differences were statistically significant（P<0.05）.However,the lactic acid of experimental control group at T₄continued to increase compared with that of T₂,and the differences were statistically significant（P<0.05）.Comparison between groups:Differences were little significant between groups at T₀and T₂（P>0.05）.At T₄,the differences between hydroxyethyl starch group,lactated Ringer group and normal saline group were statistically significant（P<0.05）,and the differences between experimental control group and each group were statistically significant（P<0.05）.Conclusions:1.Hydroxyethyl starch solution and succinyl gelatin solution are better than normal saline,lactated Ringer’s solution and acetated Ringer’s solution in improving microcirculation in rabbits with hemorrhagic shock.2.Neither normal saline,lactated Ringer’s solution,acetated Ringer’s solution,hydroxyethyl starch solution and succinylated gelatin could improve the early inflammatory factor levels in rabbits with hemorrhagic shock.3.Resuscitation with hydroxyethyl starch solution can better reduce lactic acid levels.