Clinical paperPrehospital induction of therapeutic hypothermia during CPR: A pilot study☆
Introduction
Mild therapeutic hypothermia improves survival and neurological outcome in comatose survivors of out-of-hospital cardiac arrest.1, 2 Current resuscitation guidelines recommend that therapeutic hypothermia should be induced as soon as possible,3 and there is evidence that delays in the cooling process negates the beneficial effects of this treatment.4, 5 In experimental cardiac arrest studies, intra-arrest cooling significantly improved resuscitation outcomes.6, 7 Infusion of ice-cold intravenous fluids for induction of therapeutic hypothermia has been found to be feasible and safe after return of spontaneous circulation (ROSC) in humans,8, 9, 10, 11 and one experimental study has shown this method to also be effective during ongoing cardiopulmonary resuscitation (CPR).12 We report our initial experience in the use of intravenous infusion of ice-cold Ringer's solution during ongoing CPR in prehospital patients treated by paramedics. The aim was to evaluate the feasibility of this approach and to study the cooling effects of this treatment during cardiac arrest.
Section snippets
Material and methods
We enrolled five consecutive patients treated by the paramedic-staffed Tampere Emergency Medical Service (EMS) system. This is a two-tiered EMS system with basic emergency medical technicians in the first tier, backed up by paramedics as a second tier. Patients, aged ≥18 years with cardiac arrest not due to trauma or intoxication, were included regardless of the initial cardiac rhythm. Exclusion criteria were pregnancy, return of spontaneous circulation within 5 min from the onset of
Results
The data of the study patients are shown in Table 1. There were four male and one female patient. Their mean age was 68 years and mean weight was 77 kg. All patients were resuscitated indoors. The initial cardiac rhythms were pulseless electrical activity in three patients, ventricular fibrillation in one and asystole in one patient. The mean delay from the onset of resuscitative efforts to infusion of cold fluids was 10 min.
During CPR, the mean volume of infused cold solution was 892 ml during a
Discussion
In this pilot study, induction of therapeutic hypothermia by paramedics using cold fluids via a peripheral vessel was found to be feasible during CPR. We found that the infusion of moderate amounts of cold (+4 °C) Ringer's acetate during cardiopulmonary resuscitation resulted in a fall in nasopharyngeal temperature during ongoing CPR. The volumes needed were smaller than in our previous study.9 It has been estimated that an infusion of 30 ml/kg of +4 °C saline decreases core temperature by 1.5 °C.3
Conclusions
We found that induction of therapeutic hypothermia using infusion of cold Ringer's solution by paramedics during cardiopulmonary resuscitation was feasible. This method warrants caution, however, as temperature is prone to decrease rapidly with small volumes of cold fluid and the decrease seems to continue even after the cessation of infusion. To which degree nasopharyngeal temperature reflects brain temperature in this context has to be further investigated.
Conflict of interest
None of the authors have conflicts of interest to declare.
Acknowledgement
We wish to thank the paramedics of the Tampere EMS system for their co-operation during this and future studies.
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2011, American Journal of Emergency Medicine
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A Spanish translated version of the summary of this article appears as Appendix in the final online version at 10.1016/j.resuscitation.2007.08.015.