Hypothermia is neuroprotective, because it reduces brain oxygen consumption in 6%, suppresses chemical reactions associated to reperfusion, reduces free radicals and mitochondrial damage. It has already been proved useful when implemented late after cardiac arrest, and its immediate use could be more beneficial. Adverse effects such as cardiac arrhythmia, infection and coagulopathy lead to abandon protocols with moderate hypothermia (28-32 C°).
Low hypothermia (32-34 C°) post cardiorespiratory arrest is recommended but classical approaches make it difficult to maintain a stable temperature, therefore a device with automatic feedback could be useful.
The study randomized 36 patients post cardiorespiratory arrest (26 shockable rhythm, 10 asystole) to be cooled to 32°C vs.34°C by intravenous infusion of saline followed by a catheter Icy 9.3F implantation (ZOLL Medical Corporation, Chelmsford, MA) in the inferior vena cava through a femoral vein connected to the Thermogard XP Temperature Management System (ZOLL Medical Corporation).
Temperature was maintained for 24 hrs followed by 12 to 24 hrs of rewarming. Primary end point was survival free from severe dependence (Barthel index score ≥ 60) at 6 months. 44.4% of the 32 C° group reached primary end point vs. 11.1% of 34 C° group (p=0.12). All patients with asystole died within follow up. But from patients with initial shockable rhythm 61% of those assigned to 32°C were alive and free from severe dependence at six months, compared to 15.4% of those assigned to 34°C (p=0,0002). Complications incidence was similar in both groups.
Conclusion: this trial suggests that a cooling target of 32 C° in out of hospital cardiorespiratory arrest survivors could be beneficial.
Comment: though several questions remain unanswered, this therapy appears premising for this small group of patients. More definite results require further and larger trials
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Esteban Lopez-de-Sa
2012-11-06
Original title: Pilot Trial of Two Levels of Hypothermia in Comatose Survivors from Out-of-Hospital Cardiac Arrest.
