Elsevier

Resuscitation

Volume 80, Issue 5, May 2009, Pages 561-566
Resuscitation

Experimental paper
Intra-arrest hypothermia: Both cold liquid ventilation with perfluorocarbons and cold intravenous saline rapidly achieve hypothermia, but only cold liquid ventilation improves resumption of spontaneous circulation*

https://doi.org/10.1016/j.resuscitation.2009.01.016Get rights and content

Abstract

Background

Rapid intra-arrest induction of hypothermia using total liquid ventilation (TLV) with cold perfluorocarbons improves resuscitation outcome from ventricular fibrillation (VF). Cold saline intravenous infusion during cardiopulmonary resuscitation (CPR) is a simpler method of inducing hypothermia. We compared these 2 methods of rapid hypothermia induction for cardiac resuscitation.

Methods

Three groups of swine were studied: cold preoxygenated TLV (TLV, n = 8), cold intravenous saline infusion (S, n = 8), and control (C, n = 8). VF was electrically induced. Beginning at 8 min of VF, TLV and S animals received 3 min of cold TLV or rapid cold saline infusion. After 11 min of VF, all groups received standard air ventilation and closed chest massage. Defibrillation was attempted after 3 min of CPR (14 min of VF). The end point was resumption of spontaneous circulation (ROSC).

Results

Pulmonary arterial (PA) temperature decreased after 1 min of CPR from 37.2 °C to 32.2 °C in S and from 37.1 °C to 34.8 °C in TLV (S or TLV vs. C p < 0.0001). Coronary perfusion pressure (CPP) was higher in TLV than S animals during the initial 3 min of CPR. Arterial pO2 was higher in the preoxygenated TLV animals. ROSC was achieved in 7 of 8 TLV, 2 of 8 S, and 1 of 8 C (TLV vs. C, p = 0.03).

Conclusions

Moderate hypothermia was achieved rapidly during VF and CPR using both cold saline infusion and cold TLV, but ROSC was higher than control only in cold TLV animals, probably due to better CPP and pO2. The method by which hypothermia is achieved influences ROSC.

Introduction

The International Liaison Committee on Resuscitation (ILCOR) Guidelines for Cardiopulmonary Resuscitation currently recommend the induction of hypothermia to 32–34 °C in all unconscious adult patients with spontaneous circulation after resuscitation from out-of-hospital cardiac arrest.1, 2 This recommendation is supported by two large prospective clinical studies from Australia and Europe, which demonstrated better neurologic outcomes if such patients underwent induced hypothermia.3, 4

Externally induced hypothermia is slow, requiring hours to reach moderate hypothermia.3, 4 Various intra-arrest cooling techniques have been investigated to determine the feasibility of rapid hypothermia induction during VF cardiac arrest. Total liquid ventilation (TLV) with cold perfluorocarbons (PFCs) has been shown to rapidly decrease pulmonary arterial temperature to 33.8 °C after only 4 min of liquid ventilation in an animal model of ventricular fibrillation arrest and resuscitation, and cold TLV animals had improved resumption of spontaneous circulation (ROSC) after CPR compared with a control group.5 In addition to rapid induction of hypothermia, TLV with PFCs may provide additional protective benefits in the setting of ischemia and production of reactive oxygen species. These include improved gas exchange, decreased ventilatory inflation pressures, matching the ventilation/perfusion ratio in the lungs, improving pulmonary blood flow, and decreasing the number of pulmonary inflammatory cells present which release inflammatory mediators during cellular injury.6, 7, 8, 9, 10, 11

Cold intravenous fluid is a simpler method used to rapidly induce hypothermia.12, 13, 14, 15 When mild hypothermia was initiated early during CPR with cold saline, ROSC was more frequent and neurological outcomes improved.16 Kim et al.17 determined that hypothermia induction in patients just resuscitated from cardiac arrest could be initiated in the field even before arrival in an emergency department.

The aim of the current study was to compare two methods of rapid hypothermia induction – cold PFC TLV vs. cold intravenous saline – during resuscitation in a large animal model of ventricular fibrillation cardiac arrest.

Section snippets

Animal preparation

The University of Iowa Animal Care and Use Committee reviewed and approved the animal preparation and experimental protocol for the investigation. Twenty-four female swine (22.7 ± 1.7 kg) were randomized into one of three groups: cold TLV (TLV), cold intravenous saline (S), or control (C). Both ketamine 20 mg/kg and acepromazine 0.2 mg/kg were used for induction of general anesthesia followed by inhalational 4% isoflurane via face mask. Animals were intubated with placement of a Sheridan/HVT® 7.0

Baseline

A total of 24 swine were studied and randomized into 3 groups: control (C, n = 8), cold intravenous saline (S, n = 8), and cold total liquid ventilation (n = 8). Compared to C animals, there were no differences in baseline heart rate, mean arterial pressure (MAP), cardiac output (CO), mean pulmonary arterial pressure (MPAP), pulmonary capillary wedge pressure (PCWP), coronary perfusion pressure (CPP), pH, partial pressure of arterial oxygen (pO2), and temperature (esophageal, pulmonary arterial,

Discussion

Boddicker et al.19 demonstrated that animals rendered hypothermic by external cooling before cardiac arrest was induced showed a higher ROSC rate than normothermic animals, but external cooling is very slow. In the current study, hypothermia was rapidly achieved with cold IV saline or cold total liquid ventilation with perfluorocarbons during resuscitation from VF arrest. Although IV saline achieved a lower pulmonary artery temperature, only TLV improved resuscitation outcome compared to a

Conflict of interest

None of the authors have any conflict of interest regarding this manuscript.

Acknowledgement

Supported in part by NHLBI grant #5 R01 HL71676-04. No assistance was used in the writing of this manuscript.

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    *

    A Spanish translated version of the summary of this article appears as Appendix in the final online version at doi:10.1016/j.resuscitation.2009.01.016.

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