Effects Of Environmental Hypothermia And Anesthesia On Hemodynamics And Oxygen Dynamics And Core Temperature In Hemorrhagic Shock Pigs

Objective：To study the effects of environmental hypothermia and anesthesia onhemodynamics and oxygen dynamics and core temperature in swine model ofhemorrhagic shock （HS）.Methods：1.24healthy Bama miniature pigs were randomized into three groups （n=8, each）:awaken ambient temperature group （A） and awaken environmental hypothermiagroup （B） and anesthesia ambient temperature group （C）.2. Right internal jugular vein and right femoral artery were cut open and insertedpulmonary artery flotation catheter and deep venous catheter respectively forhemodynamics and core temperature monitoring, blooding, blood sampling andblood gas analysis. Pigs in group A and group B were placed in a special cage2hfor awake and stable and adjusted anesthetics for stable0.5h in group C afteroperation. 3. Venous blood (30ml·kg^-1) was continously withdrawn over15minutes in pigsto establish HS model.4. Placed models of group B in0～5℃environment and adjusted anesthetics ingroup C by unified standard.5. Pulmonary arterial temperature（core temperature）, Heart rate （HR）, meanarterial pressure （MAP）, central venous pressure （CVP）, mean pulmonary arterypressure （MPAP）, pulmonary artery wedge pressure （PAWP） and cardiac output（CO）, saturation of mixed venous blood（SmvO₂）and blood gas analysis wererecorded at the pro-bleed （HS0min） and different HS time; The stroke volume（SV）, systemic vascular resistance （SVR）, oxygen uptake （Ca-vO₂）, oxygendelivery （DO₂）, oxygen consumption（VO₂）, and the oxygen extraction ratio（O₂ER）were calculated; record survive time of all pigs.Results：1. Effects of environmental hypothermia on hemodynamics and oxygen dynamicsand core temperature in hemorrhagic shock pigsIn period of4hours after HS, core temperature of group A and B decreasedfrom38.97±0.57℃and39.75±0.71℃to37.37±0.99℃and35.43±1.81℃,respectively. There was significant difference between two groups afterHS120min （P﹤0.05）. HR of group A and B increased to193±19bpm and166±27bpm respectively in HS15min, then the group A decreased gradually, thevariation of HR in group B was smaller. But the MAP and SVR increased morerapidly in group B, they reached max value of120±7mmHg and6308±479dyne.sec.cm^-5at HS120min, whereas reached max value of91±7mmHgand3543±443dyne.sec.cm^-5at HS180min in group A. CO and SV also got morereduction in group B. HS resulted in significant reduction in DO₂and VO₂, whileno difference was found between two groups, but the SmvO₂、Ca-vO₂and ERO₂ obviously inferior in group B after HS150min （P﹤0.05）. There no significantdifference between two groups in other indexes, but more complicated changedtrends was found in group B. Kaplan-Meier survival analysis showed that theliving conditions in group A was better than group B （Log-rank test P=0.025）.2. Effects of anesthesia on hemodynamics and oxygen dynamics and coretemperature in hemorrhagic shock pigsIn period of4hours after HS, core temperature of group A decreased from38.97±0.57℃to37.37±0.99℃, whereas core temperature in group C stabilized inthe level of34℃to35℃. There was significant difference between two groups（P﹤0.05）. HR of group A and C increased to193±19bpm and126±16bpmrespectively in HS15min, then decreased gradually in group A, while thevariation of HR in group C was smaller. MAP and CO in group A increased morerapidly than group C after HS， which exceed80mmHg and1.5L·min-1respectively at HS90min. But no difference was found in SVR between twogroups, and MPAP increased more significantly in group C. HS resulted insignificant reduction in DO₂and VO₂, which decreased below200ml·min-1and150ml·min-1respectively, but lower levels in group C, and O₂ER, Ca-vO₂and LAwere lower, SmvO₂was higher in group C. Two sets pigs were all survived within4h.Conclusion：1. Relative to ambient, core-body temperature decreased more rapidly, vascularresistance was higher in systemic circulation, cardiac output was lower andoxygen metabolism was more complicated when HS models were exposed inenvironmental hypothermia. Environmental hypothermia accelerated the naturalprogression of HS and increased short-term mortality of hemorrhagic shock.2. Anesthesia significantly attenuated the stress compensatory response of hemodynamics and depressed the cardiovascular system obviously; oxygensupply and oxygen consumption decreased simultaneously, but the imbalance ofoxygen dynamics was attenuated in anesthesia state.