Mild hypothermia induced by a helmet device: a clinical feasibility study

Abstract

Study objective: To test the feasibility and the speed of a helmet device to achieve the target temperature of 34 °C in unconscious after out of hospital cardiac arrest (CA). Methods: Patients with cardiac arrest due to asystole or pulseless electrical activity (PEA) who remained unconscious after restoration of spontaneous circulation (ROSC) were enrolled in the study and randomised into two groups: a normothermic group (NG) and a hypothermic group (HG). Bladder and tympanic temperature were monitored every 15 min. A helmet device was used to induce mild hypothermia in the HG. Later on, the effect of mild hypothermia on the haemodynamics, electrolytes, lactate, arterial pH, CaO 2, CvO 2 and O 2 extraction ratio were analysed and compared to the values obtained from the NG. Results: Thirty patients were eligible for the study, 16 were randomised into the HG and 14 were randomised into the NG. The median tympanic temperature at admission in both groups was 35.5 °C (range: 33.3–38.5 °C) and the median tympanic temperature after haemodynamic stabilisation was 35.7 °C (range: 33.6–38.2 °C). In the HG, the core and the central target temperature of 34 °C were achieved after a median time of 180 and 60 min, respectively after ROSC. At the start of the study, no significant differences between the NG and HG were seen. At the end of the study, lactate concentration and O 2 extraction ratio were significantly lower in the HG; however the CvO 2 was significantly lower in the NG. Conclusions: Mild hypothermia induced by a helmet device was feasible, easy to perform, inexpensive and effective, with no increase in complications.