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

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 ofovercooling below body core temperature (BT) of 32 degrees C.

MATERIAL AND METHODS: We performed retrospective analysis of all 56 consecutive cardiac arrest survivors treated by MH who reached therapeutic BT in the 2nd 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 degrees C followed by maintainance of BT 32-34 degrees 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 degrees 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 degrees C), higher cooling rate (the interval required for a decrease of BT by 1 degrees 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.