低温暴露对失血性休克血流动力学和氧动力学的影响

Effects of environmental hypothermia on hemodynamics and oxygen dynamics in hemorrhagic shock pigs

目的研究低温暴露对失血性休克猪血流动力学和氧动力学的影响。方法巴马小型猪16头，采用随机数字表法分为2组（每组8头）：常温对照组（c组）和低温实验组（H组）。2组猪均在15min内按全身血容量的40％（即按30ml／kg计算）匀速放血制备休克模型后，分别置于20％～22℃常温和0℃～5℃低温环境中，监测和计算放血前和放血后4h内不同时点的肺动脉温度（pulmonary arterial temperature，TP）和心率（HR）、平均动脉压（MAP）等血流动力学指标；通过血气分析监测和计算乳酸（LA）、氧供（oxygen delivery，DO2）、氧耗（oxygen consumption，VO2）等氧动力学指标；记录每头猪的生存时间。结果失血性休克（hemorrhagic shock，HS）后4h，C组和H组TP分别从（38．97±0．57）℃和（39．75±0．71）℃下降到（37．37±0．99）℃和（35．43±1．81）℃，两组HS120min后差异有统计学意义（P〈0．05）；HS发生后，C组和H组HR分别升至（193±19）次／分和（166±27）次／分，其后C组逐步下降，H组变异较小，但H组MAP和体循环阻力（systemic vascular resistance，SVR）升高较快，于HS120min最高达（120±7）mmHg（1mm Hg=0．133kPa）和（6308±479）dyne·sec·cm-5，而c组于HS180min达最高值（91±7）mmHg和（3543±443）dyne·sec·cm-5，同时H组心排出量（cardiac output，CO）和每搏量（stroke volume，SV）均降低更加明显；HS导致DO2和VO2明显下降，组间差异无统计学意义，但HS150min后，H组混合静脉血氧饱和度（mixed venous blood，SmvO2）、动静脉血氧含量差（oxygenuptake，Ca-vO2）和氧摄取率（oxygen extraction ratio，ERO2）显著差于C组（P〈0．05）；Kaplan-Meier生存分析显示C组生存状况优于H组（Log-rank检验P=0．025）。结论低温暴露使HS机体中心体温下降更快，SVR明显增高，CO更低，氧代谢紊乱更加复杂，使休克病程更快进展至失代偿期，并增加短期死亡率。

Objective To study the effects of environmental hypothermia on hemodynamics and oxygen dynamics in swine model of hemorrhagic shock （HS）. Methods 16 healthy Bama miniature pigs were randomized into two groups （n=8）： Ambient temperature group （C） and environmental hypothermia group （H）. Venous blood （30 ml/kg） was continously withdrawn over 15 minutes in pigs to establish HS model, then placed models of two groups in the environment of 20℃-22℃ and 0℃-5℃ respectively. Pulmonary arterial temperature （TP）, Heart rate （HR）, mean arterial pressure （MAP）, central venous pressure （CVP）, mean pulmonary artery pressure （MPAP）, pulmonary artery wedge pressure （PAWP） and cardiac output （CO）, saturation of mixed venous blood （SmvO2）and blood gas analysis were recorded at the pro-bleed （HS 0 min） and different HS time; The stroke volume （SV）, systemic vascular resistance （SVR）, oxygen uptake （Ca-vO2）, oxygen delivery （DO2）, oxygen consumption（VO2）, and the oxygen extraction ratio（ERO2）were calculated, along with survive time of all pigs. Results In period of 4 hrs after HS, TP of group C and H decreased from （38.97±0.57）℃ and （39.75±0.71）℃ to （37.37±0.99）℃ and （35.43±1.81）℃, respectively. There was significant difference between two groups after HS120 min （P〈0.05）. HR of group C and H increased to （193±19） bpm and （166±27） bpm respectively at HS15 min, then the group C decreased gradually, the variation of HR in group H was smaller. But the MAP and SVR increased more rapidly in group H, they reached max value of （120±7） mm Hg （1 mm Hg=0.133 kPa）and （6 308±479）dyne.sec. cm-5 at HS120 min, whereas reached max value of （91-7） mm Hg and （3 543±443）dyne.sec.cm-5 at HS180 min in group C. CO and SV also got more reduction in group H. HS resulted in significant reduction in DO2 and VO2, while no difference was found between two groups, but the SmvO2,Ca-vO2 and ERO2 obviously inferior in group H after HS150 min （P〈0.05）. There was no significant difference between two groups in other indexes, but more complicated changed trends was found in group H. Kaplan-Meier survival analysis showed that the living conditions in group C was better than group H （Log-rank test P=0.025）. Conclusion Relative to ambient, core-body temperature decreased more rapidly, vascular resistance was higher in systemic circulation, cardiac output was lower and oxygen metabolism was more complicated when HS models were exposed in environmental hypothermia. Environmental hypothermia accelerated the natural progression of HS and increased short-term mortality of hemorrhagic shock.