亚低温对兔心肺复苏后凝血及脑微循环的影响

目的 探讨亚低温治疗对兔心肺复苏后凝血异常及脑微循环血流变化的干预作用.方法 本实验在中山大学卫生部辅助循环重点实验室进行.24只成年新西兰大白兔随机(随机数字法)分为常温(normothermic,NT)治疗组和亚低温治疗(therapeutic hypothermia,TH)组,每组12只,采用交流电致颤的方式建立心肺复苏(CPR)模型,自主循环恢复后(ROSC)NT组动物置于室温下观察12 h,TH组动物采用体表降温的方法诱导亚低温,达到目标温度后维持12 h.所有动物CPR前及ROSC后4,8,12 h分别测定PT,APTT,INR,D-D,血小板计数(BPC);测定抗凝血酶Ⅲ活性(AT-Ⅲ)和血浆蛋白C活性(PC);用PERIMED Multichannel Laser Doppler系统监测大脑皮层微循环血流.各组数据依据正态检验结果用单因素方差分析或秩和检验,多重比较用LSD-t检验,两样本均数的比较用成组t检验,相关性采用Pearson相关性分析,以P＜0.05为差异具有统计学意义.结果 NT组动物ROSC后PT,APTT,INR逐渐缩短的趋势,ROSC后12 h APTT明显短于基础值(P=0.025),而AT-Ⅲ和PC活性显著下降.和NT组相比,TH组PT,APTT,INR值显著增大,差异具有统计学意义;但AT-Ⅲ,PC活性、D-D浓度,两组差异无统计学意义.CPR前、ROSC后4,8和12 h NT组大脑皮层血流分别(401.60±11.76),(258.86±34.58),(317.59±23.36)和(371.98±5.79)mL/min,TH组为398.18±12.91.336.19±19.27,347.76±13.80和383.78±3.29 mL/min.ROSC后各时间点TH组大脑皮层血流量明显高于NT组(4 h:t=-6.025,df=16,P=0.000;8 h:t=-2.942,df=12,P=0.012;12 h:t=-3.959,df=8,P=0.004).Pearson相关分析显示ROSC后大脑皮层血流和APTT正相关(4 h:R=0.503,P=0.033;8 h:R=0.565,P=0.035;12 h:R=0.774,P=0.009),与其他凝血指标无关.结论 ROSC后亚低温治疗使凝血功能下降的同时伴随脑微循环血流的增加,CPR后亚低温治疗对ROSC后凝血失衡的影响可能是其发挥脑保护作用的机制之一.

Abstract：

Objective To study the effects of mild hypothermia (MH) on blood coagulation and cerebral microcirculation in rabbits after cardiopulmonary resuscitation (CPR). Method A total of 24 New Zealand rabbits were randomly (random number) divided equally into normothermic group (NT) and MH group. CPR model was established by ventricular fibrillation induced by using alternating current. The rabbits of NT group were observed for 12 h in room temperature after restoration of spontaneous circulation (ROSC). The mild hypothermia was induced in the rabbits of group MH by surface cooling after ROSC, and maintained for 12 h after the aimed low temperature reached. The PT (prothrombin time), APTT (activated partial thromboplastin time), INR (international normalized ratio of prothrombin), D-dimmer (DD) , blood platelet count (BPC) , anti-thrombin Ⅲ activity (AT-Ⅲ) and protein C activity (PC) were measured before CPR and 4 h, 8 h and 12 h after ROSC, and at the same time the cerebral microcirculation was measured by using PERIMED Multichannel Laser Doppler system. One-way ANOVA or Mann-Whitney rank was used to determine the statistical significance between two groups. LSD-t test was used for multiple comparisons,t test for comparisons of means between two independent samples, and Pearson correlation test for correlation analysis. Results The PT, APTT and INR showed a trend of gradually shortening during the course. The APTT in 12 h after ROSC was significantly shorter than that before CPR (23.32 ±5.19 vs. 29.53 ±5.10,P = 0.025), and the activity of AT- Ⅲ and PC were decreased significantly. Compared with the group NT,the PT, APTT and INR in group MH were increased significantly, while there were no differences in the activity of AT- Ⅲ, PC and D-D between two groups. The rates of cerebral microcirculation in group NT before CPR and 4 h, 8 h and 12 h after ROSC were 401.60 ± 11.76 mL/min, 258.86 ± 34. 58 mL/min,317.59 ± 23.36 mL/min and 371.98 ± 5.79 mL/min, respectively, and those in group MT were 398.18 ±12.91 mL/min, 336.19 ± 19.27 mL/min, 347.76 ± 13.80 mL/min and 383.78 ± 3.29 mL/min, respectively. There were significant differences between two groups at each interval after ROSC (4 h: t = - 6.025,df=16, P=0.000;8 h: t= -2.942, df=12, P=0.012;12 h: t= -3.959, df=8, P=0.004). The Pearson correlation test showed that the rate of cerebral microcirculation was positive correlated with APTT after ROSC (4 h:R =0.503,P=0.033;8 h:R=0. 565,P=0. 035;12 h:R=0. 774,P=0. 009), and was not correlated with the other blood coagulants. Conclusions The mild hypothermia led to the inhibition of blood coagulation and improved the cerebral microcirculation concomitantly, which may be one of the mechanism of cerebral protection.

The impact of mild hypothermia on coagulation and cerebral microcirculation after cardiopulmonary resuscitation in rabbits

Objective To study the effects of mild hypothermia (MH) on blood coagulation and cerebral microcirculation in rabbits after cardiopulmonary resuscitation (CPR). Method A total of 24 New Zealand rabbits were randomly (random number) divided equally into normothermic group (NT) and MH group. CPR model was established by ventricular fibrillation induced by using alternating current. The rabbits of NT group were observed for 12 h in room temperature after restoration of spontaneous circulation (ROSC). The mild hypothermia was induced in the rabbits of group MH by surface cooling after ROSC, and maintained for 12 h after the aimed low temperature reached. The PT (prothrombin time), APTT (activated partial thromboplastin time), INR (international normalized ratio of prothrombin), D-dimmer (DD) , blood platelet count (BPC) , anti-thrombin Ⅲ activity (AT-Ⅲ) and protein C activity (PC) were measured before CPR and 4 h, 8 h and 12 h after ROSC, and at the same time the cerebral microcirculation was measured by using PERIMED Multichannel Laser Doppler system. One-way ANOVA or Mann-Whitney rank was used to determine the statistical significance between two groups. LSD-t test was used for multiple comparisons,t test for comparisons of means between two independent samples, and Pearson correlation test for correlation analysis. Results The PT, APTT and INR showed a trend of gradually shortening during the course. The APTT in 12 h after ROSC was significantly shorter than that before CPR (23.32 ±5.19 vs. 29.53 ±5.10,P = 0.025), and the activity of AT- Ⅲ and PC were decreased significantly. Compared with the group NT,the PT, APTT and INR in group MH were increased significantly, while there were no differences in the activity of AT- Ⅲ, PC and D-D between two groups. The rates of cerebral microcirculation in group NT before CPR and 4 h, 8 h and 12 h after ROSC were 401.60 ± 11.76 mL/min, 258.86 ± 34. 58 mL/min,317.59 ± 23.36 mL/min and 371.98 ± 5.79 mL/min, respectively, and those in group MT were 398.18 ±12.91 mL/min, 336.19 ± 19.27 mL/min, 347.76 ± 13.80 mL/min and 383.78 ± 3.29 mL/min, respectively. There were significant differences between two groups at each interval after ROSC (4 h: t = - 6.025,df=16, P=0.000;8 h: t= -2.942, df=12, P=0.012;12 h: t= -3.959, df=8, P=0.004). The Pearson correlation test showed that the rate of cerebral microcirculation was positive correlated with APTT after ROSC (4 h:R =0.503,P=0.033;8 h:R=0. 565,P=0. 035;12 h:R=0. 774,P=0. 009), and was not correlated with the other blood coagulants. Conclusions The mild hypothermia led to the inhibition of blood coagulation and improved the cerebral microcirculation concomitantly, which may be one of the mechanism of cerebral protection.