Effect Of Mild Hypothermia On Endotoxin Receptor Expression After Cardiopulmonary Resuscitation In Cardiac Arrest Rats

Part-I Effect of the type of advanced airway on cardiopulmonary resuscitation in a model of cardiac arrestObjective: To investigate the influence of the type of artificial airway on the respiratory function and the survival rate after return of spontaneous circulation in a rat model of asphyxial cardiac arrest(CA).Methods: The rat model of asphyxial CA was made by clamping endotracheal tube at expiration. Thirty male SD rats were randomly divided into two groups: orotracheal intubation group (n=15) and tracheotomy group (n=15). To observe the changes of blood gas during mechanical ventilation and spontaneously breathing, and to compare the 6-hour,24-hour and 72-hour survival rate between two groups.Results: The pH of orotracheal intubation group was not statistically different during mechanical ventilation and spontaneously breathing(7.41±0.02 versus 7.40±0.02) (P>0.05), but in tracheotomy group , the pH(7.40±0.03 versus 7.31±0.02, P<0.001) and PaCO2(40.32±2.43mmHg versus 49.56±3.35mmHg, P<0.001) were statistically different. Between two groups, the synchronous pH(7.40±0.02 versus 7.31±0.02, P<0.001), PaCO2(42.03±2.01mmHg versus 49.56±3.35mmHg, P<0.001) and PaO2(95.43±2.36mmHg versus 71.29±9.51mmHg, P<0.001) were statistically different. 6-hour,24-hour survival rates between two groups were not statistically different(P>0.05), but declined apparently in tracheotomy group. 72-hour survival rate between orotracheal intubation group and tracheotomy group was statistically different(85.7% versus 50%, P<0.05).Conclusion: For the rat model of CA , which needs a long time observation, to stop mechanical ventilation or to remove the artificial airway, orotracheal intubation should be selected with priority. And the orotracheal intubation, we have improved, is more practical and feasible in the rat. Part-II Effect of mild hypothermia on endotoxin receptor expression after cardiopulmonary resuscitation in cardiac arrest ratsObjective:To investigate the change of endotoxin receptor in cardiac arrest rat and the effect of mild hypothermia on the change.Methods:After setting up cardiac arrest model in rats, 24 animals were randomly divided into control group(S group), routine resuscitation group(C group) and mild hypothermia resuscitation group(M group), (n=8, per group). All animals were injected 3mg/kg LPS at 24h after operation or after CPR. In three groups, the contents of sCD14 and TNF-αin the plasma were determined by enzyme immunoassay method at 6 h, 12 h, 24 h after CPR or operation, and then at 1.5 h, 3 h, 6 h after injection of LPS. The expression of mCD14 protein in alveolar macrophage(AM) and interstitial macrophage were determined by immunohistochemistry. Pathological observation were observed in the right lung.Results:Contrast to S group, the contents of sCD14 in other groups increased after CPR and injection of LPS, but M group was less than C group at 6h(0.35±0.09ug/ml versus 0.54±0.16 ug/ml, P<0.05) and 24h(0.84±0.13ug/ml versus 1.02±0.19 ug/ml, P<0.05) after CPR. After injection of LPS, the contents of sCD14 in M group were compared with C group at 1.5h,3h,6h(1.82±0.21ug/ml versus 2.84±0.33ug/ml,2.76±0.21ug/ml versus 3.23±0.28ug/ml,2.72±0.29ug/ml versus 3.16±0.43ug/ml), two groups were statistically different(P<0.05). After injection of LPS, the contents of TNF-αin all the groups increased, M group was less than C group at 1.5h,3h,6h, two groups were statistically different(P<0.01). Furthermore, it was direct correlation between the contents of TNF-αand sCD14(r=0.92,P<0.01). The expression of AM mCD14 in C group was more than in M group (△OD 0.37±0.05 versus△OD 0.25±0.04, P<0.01). The ALI score in M group was lower in C group(8.04±0.81 versus 9.65±1.65, P<0.05).Conclusion:The expression of endotoxin receptor in cardiac arrest rat increased after CPR, meanwhile, enhanced sensitivity to the subsequent LPS challenge. But mild hypothermia could inhibit the increase, and mitigate the lung injury of LPS after CPR.