Overcooling during mild hypothermia in cardiac arrest survivors - phenomenon we should keep in mind

Czech version

Authors: R. Škulec ^1,2; T. Kovárník ²; prof. MUDr. Jan Bělohlávek, Ph.D. ²; G. Dostálová ²; J. Kolář ²; A. Linhart ²; J. Šeblová ¹
Authors‘ workplace: Záchranná služba Středočeského kraje Kladno, ředitel MUDr. Robert Zelenák ¹; II. interní klinika kardiologie a angiologie 1. lékařské fakulty UK a VFN Praha, přednosta prof. MUDr. Aleš Linhart, DrSc. ²
Published in: Vnitř Lék 2008; 54(6): 609-614
Category: Original Contributions

Overview

Background:
Mild hypothermia (MH) in cardiac arrest survivors has became a routine part of early postresuscitative support. Overcooling is a frequent phenomenon with the unknown outcome.

Aim of the study:
To analyze the incidence and outcome of overcooling below body core temperature (BT) of 32 °C.

Material and methods:
We performed retrospective analysis of all 56 consecutive cardiac arrest survivors treated by MH who reached therapeutic BT in the II^nd Department of Internal Medicine, General Teaching Hospital, Prague. MH was initiated as soon as possible after the return of spontaneous circulation to reach BT of 33 °C followed by maintainance of BT 32–34 °C for 12 hours. Patients were cooled by surface cooling via ice-packs and by interavenous infusion of cold crystaloids.

Results:
Overcooling below BT of 32 °C was observed in 23 patients (41%). This group of patients had more frequently asystole as the initial rhythm (34.8 vs 9.1%), more frequently were cooled by combinatory cooling approach (56.5 vs 27.3%), more frequently had lower baseline BT (35.3 ± 1.3 vs 36.2 ± 1.2 °C), higher cooling rate (the interval required for a decrease of BT by 1 °C 61.5 ± 53.1 vs 90.1 ± 50.0 min) (all p < 0.05) than patients with proper profile of BT during MH. Overcooling was independent negative predictor of discharge favourable neurological outcome (OR 0.16, 0.022-0.77, p = 0.037).

Conclusion:
Induction of MH by conventional cooling approach is burdened by high risk of overcooling. This phenomenon is probably associated with worse outcome.

Key words:
cardiac arrest - mild hypothermia - overcooling

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