Study of the Effects of 3 h of Continuous Cardiopulmonary Resuscitation at 27°C on Global Oxygen Transport and Organ Blood Flow.

Jan Harald Nilsen,Torstein Schanche,Torvind Naesheim,Sergei Valkov,Gary C Sieck,Rizwan Mohyuddin,Timofei V Kondratiev,Torkjel Tveita

doi:10.3389/fphys.2020.00213

Abstract

AimsComplete restitution of neurologic function after 6 h of pre-hospital resuscitation and in-hospital rewarming has been reported in accidental hypothermia patients with cardiac arrest (CA). However, the level of restitution of circulatory function during long-lasting hypothermic cardiopulmonary resuscitation (CPR) remains largely unknown. We compared the effects of CPR in replacing spontaneous circulation during 3 h at 27°C vs. 45 min at normothermia by determining hemodynamics, global oxygen transport (DO2), oxygen uptake (VO2), and organ blood flow.MethodsAnesthetized pigs (n = 7) were immersion cooled to CA at 27°C. Predetermined variables were compared: (1) Before cooling, during cooling to 27°C with spontaneous circulation, after CA and subsequent continuous CPR (n = 7), vs. (2) before CA and during 45 min CPR in normothermic pigs (n = 4).ResultsWhen compared to corresponding values during spontaneous circulation at 38°C: (1) After 15 min of CPR at 27°C, cardiac output (CO) was reduced by 74%, mean arterial pressure (MAP) by 63%, DO2 by 47%, but organ blood flow was unaltered. Continuous CPR for 3 h maintained these variables largely unaltered except for significant reduction in blood flow to the heart and brain after 3 h, to the kidneys after 1 h, to the liver after 2 h, and to the stomach and small intestine after 3 h. (2) After normothermic CPR for 15 min, CO was reduced by 71%, MAP by 54%, and DO2 by 63%. After 45 min, hemodynamic function had deteriorated significantly, organ blood flow was undetectable, serum lactate increased by a factor of 12, and mixed venous O2 content was reduced to 18%.ConclusionThe level to which CPR can replace CO and MAP during spontaneous circulation at normothermia was not affected by reduction in core temperature in our setting. Compared to spontaneous circulation at normothermia, 3 h of continuous resuscitation at 27°C provided limited but sufficient O2 delivery to maintain aerobic metabolism. This fundamental new knowledge is important in that it encourages early and continuous CPR in accidental hypothermia victims during evacuation and transport.

Highlights

Over the past years, patient case reports of accidental hypothermia with cardiac arrest (CA) indicate favorable neurologic outcome after in-hospital rewarming (Walpoth et al, 1990, 1997; Gilbert et al, 2000; Mark et al, 2012; Wanscher et al, 2012; Hilmo et al, 2014)
No statistically significant differences were found between groups in any of the variables recorded at the start of the experiments
Stability of the actual pig model related to hemodynamic function and organ blood flow at normothermia has previously been documented in experiments lasting up to 7 h (Filseth et al, 2010; Valkov et al, 2019)

Summary

Introduction

Patient case reports of accidental hypothermia with cardiac arrest (CA) indicate favorable neurologic outcome after in-hospital rewarming (Walpoth et al, 1990, 1997; Gilbert et al, 2000; Mark et al, 2012; Wanscher et al, 2012; Hilmo et al, 2014) These favorable outcomes appear to be linked to the good quality of pre-hospital emergency medical treatment provided including early start and continued cardiopulmonary resuscitation (CPR) (Monsieurs et al, 2015; Truhlar et al, 2015) in accordance to the latest international guidelines (Truhlar et al, 2015). Subsequent pharmacologic studies on pigs (Krismer et al, 2000; Kornberger et al, 2001) reported the maintenance of coronary perfusion pressure at 28◦C during short-lasting CPR, but neither of these studied applied the latest standard CPR algorithm (Truhlar et al, 2015)

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