Therapeutic hypothermia with a novel surface cooling device improves neurologic outcome after prolonged cardiac arrest in swine*


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Abstract

Objective:Devices for rapid induction of mild hypothermia after cardiac arrest are needed. We hypothesized that the Life Recovery Systems' ThermoSuit System provides effective core cooling by pumping ice water over the skin surface and improves neurologic outcome after prolonged cardiac arrest.Design:Prospective experimental study.Setting:University research laboratory.Subjects:Large White breed pigs (29 to 35 kg).Interventions:Swine were anesthetized and mechanically ventilated. Ten minutes of untreated ventricular fibrillation, 3 mins of basic life support, and 5 mins of advanced cardiac life support, including two 0.4 IU/kg doses of vasopressin, were followed by up to three countershocks. After restoration of spontaneous circulation, swine were randomized to two groups (normothermic control, hypothermia). The hypothermia group was cooled from a pulmonary artery temperature of 38.5 ± 0.5°C to 33.0°C and kept for 14 hrs. At day 9 of the experiment, overall performance categories scores (1, normal; 2, slightly disabled; 3, severely disabled; 4, comatose; 5, dead, brain dead) and neurologic deficit scores (0%, normal; 100%, brain dead) were assessed. Data are presented as median and interquartile range; group comparison was done with a Mann-Whitney U test.Measurements and Main Results:In total, 16 of 22 animals were randomized. Time to target temperature in the hypothermia group (n = 8) was 9.0 (5.3–11.9) mins (cooling rate 0.4 [0.3–0.8]°C/min), and all animals achieved an overall performance categories score of 1. In the control group, one swine achieved an overall performance categories score of 1, three achieved a score of 2, and four achieved a score of 3 (p = .002). Neurologic deficit score was 0% (0%–4%) in the hypothermia group and 39% (19%–55%) in the control group (p = .001). No harmful side effects could be observed.Conclusions:The Life Recovery Systems' ThermoSuit System rapidly and safely induced mild therapeutic hypothermia. Hypothermia improved neurologic outcome in swine after cardiac arrest as compared with normothermia. Further studies are warranted to compare the device with established cooling methods.

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