Objective To investigate the effects of mild hypothermia on post-resuscitation neurological outcome after ventricular fibrillation (VF) in rabbits.Methods Forty-five adult New Zealand rabbits were induced VF by direct current of electricity.The rabbits were randomly(random number) divided into following groups:normothermic resuscitation group (NR),mild hypothermia prearrest group (HP),mild hypothermia resuscitation 30 min group (HRe30),mild hypothermia resuscitation 90 min group (HRe90),normothermic sham group (NS),and hypothermia sham group (HS).The rabbits of NR group were observed for 600 min in room temperature after restoration of spontaneous circulation (ROSC).The mild hypothermia was induced by surface cooling,and maintained for 600 min after the aimed low temperature reached.The arterial blood samples were collected for determining neuron-specific enolase (NSE) and thioredoxin (Trx) and the mean arterial pressure (MAP),left ventricular end-diastolic pressure (LVEDP) and left ventricular pressure raise and fall rate (±dp/dtmax) were observed at 15 min before CA,and 30 min,60 min,120 min,360 min and 600 min after ROSC.After the animals were sacrificed at 600 min after ROSC,the whole brain of animals was harvested and observed under light microscope to calculate the apoptotic index of the hippocampal CA1 neurons by using TUNEL method.One-way ANOVA was used to determine the statistical significance between two groups,a two-tailed value of P＜0.05 was considered statistically significant.Results (1) Hemodynamically compared with normal temperature groups,HR was lower in hypothermia groups.Compared with NR,HRe30,and HRe90 group,LVEDP was higher in HP group at 30 min after ROSC(3.4±0.8 vs.4.6±1.0,4.1±0.5,4.3±0.2,F=9.85,P=0.019).In Hp group,the level of +dp/dtmax was higher than that in NR,HRe30 and HRe90 groups at 30 min and 120 min after ROSC.In HP group,the level of-dp/dtmax was higher than that of NR group at 30 min,60 min,120 min,360 min and 600 min after ROSC.(2) Serologically compared with HP,HRe30 and HRe90 group,NSE levels were higher in NR group at 60 min,120 min and 360 min after ROSC.Compared with NR,HRe30,and HRe90 group,Trx levels in NR group were lower at 60 min,120 min,360 min and 600 min after ROSC.Compared with HP group,Trx levels in HRe30 and HRe90 groups were higher at 60 min,120 min,360 min and 600 min after ROSC.(3) Pathologically compared with NR group,histopathological changes in hippocampus CA1 area were milder found in HP,HRe30 and HRe90 groups.AI (％) was lower in HP,HRe30 and HRe90 groups than that in NR group[(62.25±10.43)％ vs.(20.61±5.02)％,(25.08±3.92)％,(30.33±7.15)％,P=0.001].Concusions This study shows that hypothermia should be initiated as soon as possible,and especially early intra-arrest cooling appears to be significantly better than post-ROSC cooling and normothermia.

Objective:To evaluate the prognostic value of arterial lactate (Lac) combined with central venous-to-arterial carbon dioxide difference to arterial-to-central venous oxygen content difference ratio (Pcv-aCO 2/Ca-cvO 2) in patients with septic shock following early fluid resuscitation. Methods:A total of 97 patients with septic shock admitted to intensive care unit (ICU) of Lanzhou University Second Hospital from January 2017 to December 2019 were enrolled. The Pcv-aCO 2/Ca-cvO 2 ratio was calculated from blood gas analysis of radial artery and superior vena cava which was performed before resuscitation and at 6 hours of resuscitation at the same time. The patients were divided into death group and survival group according to the 28-day prognosis. The baseline data, acute physiology and chronic health evaluation Ⅱ (APACHEⅡ) score, sequential organ failure score (SOFA), clinical therapy, lactate clearance rate (LCR) at 6 hours, the length of ICU stay, hemodynamics and oxygen metabolism parameters before and after resuscitation were compared between the two groups. Risk factors were analyzed by multivariate Cox regression for 28-day mortality of patients with septic shock. The receiver operating characteristic (ROC) curve was plotted to assess the prognostic values of these factors for 28-day mortality. Results:① Compared with the survival group, the patients in the death group showed significantly higher levels of APACHEⅡ score (23.96±4.31 vs. 17.70±3.92) and SOFA score (12.74±2.80 vs. 9.23±2.43, both P < 0.01), significantly higher proportions of mechanical ventilation [85.2% (23/27) vs. 50.0% (35/70)] and continuous renal replacement therapy [CRRT; 51.9% (14/27) vs. 25.7% (18/70), both P < 0.05], a significantly more fluid replacement at 6 hours (L: 2.92±0.24 vs. 2.63±0.25, P < 0.01), a significantly lower level of LCR at 6 hours [(11.61±7.76)% vs. (27.67±13.71)%, P < 0.01], and a shorter length of ICU stay (days: 6.37±2.70 vs. 7.67±2.31, P < 0.05). ② Compared with the survival group, the patients before resuscitation in the death group showed a significantly lower level of mean arterial pressure [MAP (mmHg, 1 mmHg = 0.133 kPa): 52.63±4.35 vs. 55.74±3.01, P < 0.01], significantly higher levels of Lac and Pcv-aCO 2/Ca-cvO 2 ratio [Lac (mmol/L): 7.13±1.75 vs. 5.22±1.36, Pcv-aCO 2/Ca-cvO 2 ratio: 1.67±0.29 vs. 1.48±0.22, both P < 0.01]; and the patients at 6 hours of resuscitation in the death group showed a significantly lower level of MAP (mmHg: 62.59±4.80 vs. 66.71±3.91, P < 0.01), significantly higher levels of central venous pressure (CVP), Lac, Pcv-aCO 2 and Pcv-aCO 2/Ca-cvO 2 ratio [CVP (mmHg): 10.74±1.40 vs. 8.80±0.75, Lac (mmol/L): 6.36±1.86 vs. 3.90±1.95, Pcv-aCO 2 (mmHg): 7.59±2.02 vs. 4.34±1.37, Pcv-aCO 2/Ca-cvO 2 ratio: 1.87±0.51 vs. 1.03±0.27, all P < 0.01]. ③ Multivariate Cox regression analysis showed that the independent risk factors for 28-day mortality in patients with septic shock were Lac and Pcv-aCO 2/Ca-cvO 2 ratio whether before or at 6 hours of resuscitation [Lac before resuscitation: relative risk ( RR) = 1.434, 95% confidence interval (95% CI) was 1.070-1.922, P = 0.016; Lac at 6 hours of resuscitation: RR = 1.564, 95% CI was 1.202-2.035, P = 0.001; Pcv-aCO 2/Ca-cvO 2 ratio before resuscitation: RR = 2.828, 95% CI was 1.108-4.207, P = 0.038; Pcv-aCO 2/Ca-cvO 2 ratio at 6 hours of resuscitation: RR = 4.386, 95% CI was 2.842-5.730, P = 0.000]. ④ ROC curve analysis showed that Lac and Pcv-aCO 2/Ca-cvO 2 ratio at 6 hours of resuscitation had predictive value for the prognosis of patients with septic shock, the area under ROC curve (AUC) was 0.849 (95% CI was 0.762-0.914) and 0.905 (95% CI was 0.828-0.955), respectively. However, the predictive value of Lac combined with Pcv-aCO 2/Ca-cvO 2 ratio in patients with septic shock was significantly higher than Lac [AUC (95% CI): 0.976 (0.923-0.996) vs. 0.849 (0.762-0.914), Z = 3.354, P = 0.001], the sensitivity was 97.14%, and the specificity was 88.89%. Conclusions:Lac and Pcv-aCO 2/Ca-cvO 2 ratio are independent risk factors for predicting 28-day mortality in patients with septic shock. Lac combined with Pcv-aCO 2/Ca-cvO 2 ratio can assess the prognosis of patients with septic shock more accurately.