Induction of therapeutic hypothermia after cardiac arrest in prehospital patients using ice-cold Ringer’s solution: a pilot study
Introduction
Mild therapeutic hypothermia improves neurological outcome after cardiac arrest [1], [2]. It has been suggested that hypothermia should be induced as soon as possible after return of spontaneous circulation (ROSC) [3]. The earliest possible induction of hypothermia implies that the technique should be available in the prehospital setting and that it should be capable of being undertaken easily by non-physician prehospital care providers. The purpose of this study was to investigate the haemodynamic and cooling effects of infusing ice-cold Ringer’s solution immediately after ROSC in closely monitored prehospital patients using a technique described recently [4], but which has not been used in the prehospital setting before.
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Material and methods
We enrolled 13 prehospital cardiac arrest patients treated by the physician staffed Helsinki Area Helicopter Emergency Medical Air Service (Helsinki Area, HEMS). The study protocol was approved by the institutional review board of Helsinki University Hospital, Finland. Written informed consent was obtained from relatives of the patients before induction of hypothermia. Inclusion criteria were age more than 18 years, cardiac arrest not due to trauma or drug overdose, ROSC later than 10 min from
Results
Research data and demographics are shown in Table 1. The mean age of eight male and five female patients was 60.8 ± 12.5 years. ROSC was achieved at 26 ± 10 min. Initial cardiac rhythm was ventricular fibrillation (53.8%), asystole (30.8%) or pulseless electrical activity (15.4%). The oesophageal temperature decreased significantly during treatment (Fig. 1). The mean infused volume was 2188 ± 754 ml. Infusion started at 27 ± 12 min after ROSC and mean duration of infusion was 25 ± 11 min. One
Discussion
The results of this pilot study suggest that induction of therapeutic hypothermia with rapid infusion of ice-cold Ringer’s solution soon after ROSC is well tolerated and feasible in the prehospital setting. This treatment has been documented in hospitalised patients starting, on average, 73 min after ROSC [4]. However, the cardiovascular situation might be different immediately after ROSC, and the haemodynamic effects of induction of cooling by infusion at this stage have not been reported,
Conclusion
We conclude that induction of therapeutic hypothermia with peripheral infusion of ice-cold Ringer’s solution seems feasible soon after ROSC in the prehospital setting. Because this technique is also readily available to non-physician care providers, the induction of therapeutic hypothermia can be started earlier if found safe and well tolerated in larger trials.
Acknowledgements
We would like to thank the crew of the Helsinki Area HEMS for the valuable help in enrolling the study patients. This study was supported by institutional EVO grant #9B102 from Special State Allocation via Tampere University Hospital.
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