Elsevier

Resuscitation

Volume 73, Issue 1, April 2007, Pages 46-53
Resuscitation

Clinical paper
Cold infusions alone are effective for induction of therapeutic hypothermia but do not keep patients cool after cardiac arrest

https://doi.org/10.1016/j.resuscitation.2006.08.023Get rights and content

Summary

Aim of the study

Cold infusions have proved to be effective for induction of therapeutic hypothermia after cardiac arrest but so far have not been used for hypothermia maintenance. This study investigates if hypothermia can be induced and maintained by repetitive infusions of cold fluids and muscle relaxants.

Material and methods

Patients were eligible, if they had a cardiac arrest of presumed cardiac origin and no clinical signs of pulmonary oedema or severely reduced left ventricular function. Rocuronium (0.5 mg/kg bolus, 0.5 mg/kg/h for maintenance) and crystalloids (30 ml/kg/30 min for induction, 10 ml/kg every 6 h for 24 h maintenance) were administered via large bore peripheral venous cannulae. If patients failed to reach 33 ± 1 °C bladder temperature within 60 min, endovascular cooling was applied.

Results

Twenty patients with a mean age of 57 (±15) years and mean body mass index of 27 (±4) kg/m2 were included (14 males). Mean temperature at initiation of cooling (median 27 (IQR 16; 87) min after admission) was 35.4 (±0.9) °C. In 13 patients (65%) the target temperature was reached within 60 min, 7 patients (35%) failed to reach the target temperature. Maintaining the target temperature was possible in three (15%) patients and no adverse events were observed.

Conclusion

Cold infusions are effective for induction of hypothermia after cardiac arrest, but for maintenance additional cooling techniques are necessary in most cases.

Introduction

Mild hypothermia improves survival and neurological outcome after out-of-hospital cardiac arrest.1, 2, 3 According to the results of two large randomised controlled trials the European Resuscitation Council Guidelines 2005 recommend treating comatose survivors of out-of-hospital cardiac arrest due to a shockable rhythm with mild hypothermia for 12–24 h.4 The ideal method for induction and maintenance of therapeutic hypothermia is not known. As experimental results suggest that the effect of hypothermia on neurological outcome might be most beneficial when applied as early as possible after return of spontaneous circulation5, 6 recent research focused on methods for fast induction of hypothermia.7, 8, 9, 10, 11, 12, 13 So far, five feasibility trials have investigated the efficacy and safety of large volume infusions of cold infusions in more than 200 adult cardiac arrest survivors (9–13). Those studies showed that hypothermia could be induced very effectively with cooling rates up to −4.0 °C/h and no clinically relevant adverse effects of the infusions, especially no pulmonary oedema, were observed. Although the target temperature (32–34 °C) could be reached in most patients, hypothermia was then maintained by additional more resource demanding cooling techniques. To our knowledge no study has investigated, if hypothermia can be induced and also maintained by repetitive infusions of cold crystalloid fluids and complete muscle relaxation with deep sedation.

Section snippets

Methods

This was a prospective, observational case series of a convenience sample of patients after cardiac arrest admitted to an emergency department of a tertiary care hospital between October 2005 and February 2006. The study procedures were approved by the responsible committee on human experimentation. According to our study protocol there was no need for patient's consent to be included in our study but patients or their relatives received detailed information about the trial.

Inclusion and

Results

The demographics and cardiac arrest data of the 20 patients studied are presented in Table 2. Bladder temperature on admission was 35.2 (±1.1) °C. A total amount of 2465 (±536) ml of cold infusions was given commencing 93 (±62) min after return of spontaneous circulation and 27 (16; 87) min after admission. Cold infusions were started at a mean patient temperature of 35.4 (±0.9) °C which dropped to 34.4 (±1.1) °C after 30 min (p < 0.001) and to 34.2 (±1.0) °C after 60 min (p < 0.001), respectively (Figure 2

Discussion

In most patients who achieve return of spontaneous circulation after cardiac arrest hypothermia can be successfully induced by cold infusions. Although large amounts of fluid were administered within 30 min, no serious side effects occurred. Once the target temperature was reached few patients remained within the temperature range of 32–34 °C but the majority rewarmed within several hours and required additional endovascular cooling. No patient required active rewarming during the induction or

Conclusion

In the majority of patients after cardiac arrest, therapeutic hypothermia can be induced by rapid infusion of cold fluids. However, most patients rewarm after 3–4 h and require additional cooling. As most therapeutic and diagnostic interventions can be performed within this period (e.g. coronary angiography or computed tomography) the induction of hypothermia with cold infusions will allow a rapid induction of hypothermia in this first critical phase after the arrest while more resource

Conflict of interest statement

There are no conflicts of interest.

References (16)

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    Citation Excerpt :

    In the end, in a prehospital situation, this is not the only method of induction and is not sufficient in itself for the maintenance of hypothermia; internal and external cooling methods should be associated appropriately [2,4,5,11]. The targeted population and temperature, the ideal moment in the initiation of a thermic control, advantageously ensured by the application of multimodal protocols, should be better clarified and be the object of further studies [9,22–28]. The studies for inducing hypothermia per cardiopulmonary resuscitation should only be considered after the careful management of all the available techniques.

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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.2006.08.023.

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