Effects of Different Hypothermia on the Results of Cardiopulmonary Resuscitation in a Cardiac Arrest Rat Model

Abstract

Objective. To investigate the optimal temperature of hypothermia treatment in rats with cardiac arrest caused by ventricular fibrillation (VF) after the return of spontaneous circulation (ROSC). Methods. A total of forty-eight male Sprague-Dawley rats were induced by VF through the guidewire with a maximum of 5 mA current and untreated for 8 min. Cardiopulmonary resuscitation (CPR) was performed for 8 min followed by defibrillation (DF). Resuscitated rats were then randomized into the normothermia (37°C) group, milder (35°C) group, mild (33°C) group, or moderate (28°C) group. Hypothermia was immediately induced with surface cooling. The target temperature was maintained for 4 h before rewarming to 37 ± 0.5 ° C . Moreover, at the end of the 4 h, a rat in each group was randomly selected to be sacrificed for the cerebral cortex electron microscopy observation ( n = 1 ). The other resuscitated animals were observed for up to 72 h after ROSC ( n = 7 ). Left ventricular ejection fraction (LVEF) and left ventricular end diastolic volume (LVEDV) were measured. Survival time, survival rate, and neurological deficit score (NDS) were recorded for 72 h. Results. During hypothermia, higher LVEF was observed in the hypothermia groups when compared with normothermia group (35°C vs. 37°C, p < 0.05 , 33°C and 28°C vs. 37°C, p < 0.01 ). Among the hypothermia groups, LVEF was higher in the 28°C group than that of 35°C ( p < 0.05 ). However, both the heart rate (HR) ( p < 0.01 ) and LVEDV (28°C vs. 35°C, p < 0.01 , 28°C vs. 37°C and 33°C, p < 0.05 ) were lowest in the 28°C group when compared with the other groups. There were no significant differences of LVEF and LVEDV between the group 35°C and 33°C ( p > 0.05 ). After rewarming, the LVEF of 35°C group was higher than that of group 37°C, 33°C, and 28°C (35°C vs. 37°C and 28°C, p < 0.01 , 35°C vs. 33°C, p < 0.05 ). Group 35°C and 33°C resulted in longer survival ( p < 0.01 ), higher survival rate ( p < 0.01 ), and lower NDS (35°C vs. 37°C and 28°C, p < 0.01 , 33°C vs. 37°C and 28°C, p < 0.05 ) compared with the group 37°C and 28°C. The extent of damage to cerebral cortex cells in group of 35°C and 33°C was lighter than that in group of 37°C and 28°C. The 35°C group spent less time in the process of cooling and rewarming than the group 33°C and 28°C ( p < 0.01 ). Conclusions. An almost equal protective effect of milder hypothermia (35°C) and mild hypothermia (33°C) in cardiac arrest (CA) rats was achieved with more predominant effect than moderate hypothermia (28°C) and normothermia (37°C). More importantly, shorter time spent in cooling and rewarming was required in the 35°C group, indicating its potential clinical application. These findings support the possible use of milder hypothermia (35°C) as a therapeutic agent for postresuscitation.

Combination of Hyperoxygenation and Targeted Temperature Management Improves Functional Outcomes of Post Cardiac Arrest Syndrome Irrespective of Causes of Arrest in Rats

“…Normothermia was defined as a body temperature of 37.5°C. The body temperature of animals treated with hypothermia was reduced to 34.0°C by using ice packs and electrical fan to achieve the target temperature quickly and maintained for the first 2 hours of post resuscitation (18,19). Afterward, the temperature was gradually increased to normothermia within 2 hours.…”

Rat model of asphyxia-induced cardiac arrest and resuscitation

“…Recent hypothermia drug studies have shown that these can eliminate shivering by acting on central or peripheral thermoregulatory pathways, and can also be used to treat conscious patients with hypothermia ( Lee et al, 2017a ). In animal experiments, cold temperature durations range from 30 min to 6 h, with 4 h commonly used ( Diao et al, 2020 ; Xu et al, 2022 ). Finally, rewarming rate is usually controlled at 0.5–2.0°C/h ( Diao et al, 2020 ; Xu et al, 2022 ) or as the fastest rewarming speed ( Jawad et al, 2021 ; Wang et al, 2022 ).…”

“…In animal experiments, cold temperature durations range from 30 min to 6 h, with 4 h commonly used ( Diao et al, 2020 ; Xu et al, 2022 ). Finally, rewarming rate is usually controlled at 0.5–2.0°C/h ( Diao et al, 2020 ; Xu et al, 2022 ) or as the fastest rewarming speed ( Jawad et al, 2021 ; Wang et al, 2022 ).…”

“…Therefore, maintaining normothermia is often needed to avoid variable temperature confounds. Rat’s normal core body temperature (rectal temperature) is about 37.5°C ( Dangarembizi et al, 2017 ), therefore, most rat models control the normal body temperature at 37.5 ± 0.5°C ( Tungalag et al, 2022 ; Xu et al, 2022 ). Heating pads or lamps can keep the rats at normal body temperature.…”

Dependence of blood coagulation activity on temperature in cows <i>in vitro</i>

“…Одной из таких систем является тонко сбалансированная система гемостаза, которая ответственна за сохранение оптимального агрегатного состояния крови, предупреждение и остановку кровотечений, а также целостность кровеносных сосудов. реанимационных мероприятий [5] и используют животных в качестве моделей для изучения влияния гипотермии на гемостаз при сердечнолегочной реанимации. Авторы проведенного эксперимента доказали, что легкая гипотермия увеличивала сывороточные уровни физиологических антикоагулянтов у свиней [6].…”