Experimental paperIntra-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*
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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Neurology of cardiopulmonary resuscitation
2017, Handbook of Clinical NeurologyTherapeutic hypothermia for acute myocardial infarction and cardiac arrest
2012, American Journal of CardiologyCitation Excerpt :In clinical practice, the potential hazards of large volume infusions might be attenuated with the coadministration of diuretics and with mechanical ventilation. Total liquid ventilation-induced TH has been used in animal models of cardiac arrest, resulting in significantly improved rates of ROSC, improved survival, and improved neurologic outcomes.10,12 In rabbits, hypothermic total liquid ventilation achieved a tympanic temperature of 33°C in <10 minutes (rectal temperature 33°C in <20 minutes).10
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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.