Mild hypothermia preserves cerebral cortex microcirculation after resuscitation in a rat model of cardiac arrest.
OBJECTIVE
Mild hypothermia improves the outcomes of comatose patients after cardiac arrest. Its neuroprotective mechanism is not fully understood. We investigated the effects of mild hypothermia on cerebral cortex microcirculation and cerebral oxygen extraction ratio.


METHODS
Twenty-five rats were randomized into the hypothermic group (HT), normothermic group (NT) or the sham control group. Ventricular fibrillation was electrically induced and untreated for 8 min, followed by 8 min of precordial compressions and mechanical ventilations. The core temperature in the HT group was reduced to 33±0.5 °C at 14 min after ROSC with a combination of ice packs, an electrical fan and a cooling blanket. The temperature was maintained at 33 °C for 8h. Hemodynamics, arterial and jugular venous blood gases and cerebral cortex microcirculation were measured at baseline, 2, 4 and 8h after ROSC.


RESULTS
Microvascular flow index was significantly reduced in the NT and HT groups when compared with the SC group. A significant lesser reduction in microvascular flow index was observed in the HT group when compared with the NT group. Mild hypothermia reduced the cerebral oxygen extraction ratio after resuscitation when compared with the NT group.


CONCLUSIONS
Mild hypothermia improves the cerebral cortex microcirculatory blood supply/oxygen uptake mismatching after resuscitation. This may provide an additional cerebral protection.
Weil Institute of Critical Care Medicine, Rancho Mirage, CA, United States; Department of Emergency Medicine, First Hospital of Dalian Medical University, Dalian, China. Electronic address: gongp828@sina.cn.
Ping
P
Gong
Weil Institute of Critical Care Medicine, Rancho Mirage, CA, United States. Electronic address: jzkzhaoshen@163.com.
Shen
S
Zhao
Weil Institute of Critical Care Medicine, Rancho Mirage, CA, United States. Electronic address: wangjg222@gmail.com.
Jiangang
J
Wang
Weil Institute of Critical Care Medicine, Rancho Mirage, CA, United States. Electronic address: yangzhengfei@vip.163.com.
Zhengfei
Z
Yang
Weil Institute of Critical Care Medicine, Rancho Mirage, CA, United States. Electronic address: qjssmu@gmail.com.
Jie
J
Qian
Weil Institute of Critical Care Medicine, Rancho Mirage, CA, United States. Electronic address: mike_wu@weiliccm.org.
Xiaobo
X
Wu
Weil Institute of Critical Care Medicine, Rancho Mirage, CA, United States. Electronic address: jena.cahoon@weiliccm.org.
Jena
J
Cahoon
Weil Institute of Critical Care Medicine, Rancho Mirage, CA, United States; Keck School of Medicine of the University of Southern California, Los Angeles, CA, United States. Electronic address: Wanchun.tang@me.com.
Wanchun
W
Tang
D000818:Animals; D001921:Brain / Q000378:metabolism*; D001927:Brain Diseases / Q000517:prevention & control; D016887:Cardiopulmonary Resuscitation; D002540:Cerebral Cortex / Q000098:blood supply*; D004195:Disease Models, Animal; D006323:Heart Arrest / Q000628:therapy*; D007036:Hypothermia, Induced; D008297:Male; D008833:Microcirculation / Q000502:physiology*; D010100:Oxygen / Q000378:metabolism*; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley
D010100:Oxygen
Brain; Cardiopulmonary resuscitation; Hypothermia; Microcirculation