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Bradycardia During Therapeutic Hypothermia Is Associated With Good Neurologic Outcome in Comatose Survivors of Out-of-Hospital Cardiac Arrest*

Stær-Jensen, Henrik MD; Sunde, Kjetil MD, PhD; Olasveengen, Theresa M. MD, PhD; Jacobsen, Dag MD, PhD; Drægni, Tomas RN; Nakstad, Espen Rostrup MD; Eritsland, Jan MD, PhD; Andersen, Geir Øystein MD, PhD

doi: 10.1097/CCM.0000000000000515
Neurologic Critical Care

Objective: Comatose patients resuscitated after out-of-hospital cardiac arrest receive therapeutic hypothermia. Bradycardia is frequent during therapeutic hypothermia, but its impact on outcome remains unclear. We explore a possible association between bradycardia during therapeutic hypothermia and neurologic outcome in comatose survivors of out-of-hospital cardiac arrest.

Design: Retrospective cohort study, from January 2009 to January 2011.

Setting: University hospital medical and cardiac ICUs.

Patients: One hundred eleven consecutive comatose out-of-hospital cardiac arrest patients treated with therapeutic hypothermia.

Interventions: Patients treated with standardized treatment protocol after cardiac arrest.

Measurements and Main Results: All out-of-hospital cardiac arrest patients’ records were reviewed. Hemodynamic data were obtained every fourth hour during the first days. The patients were in temperature target range (32–34°C) 8 hours after out-of-hospital cardiac arrest and dichotomized into bradycardia and nonbradycardia groups depending on their actual heart rate less than or equal to 60 beats/min or more than 60 beats/min at that time. Primary endpoint was Cerebral Performance Category score at hospital discharge. More nonbradycardia group patients received epinephrine during resuscitation and epinephrine and norepinephrine in the early in-hospital period. They also had lower base excess at admission. Survival rate with favorable outcome was significantly higher in the bradycardia than the nonbradycardia group (60% vs 37%, respectively, p = 0.03). For further heart rate quantification, patients were divided into quartiles: less than or equal to 49 beats/min, 50–63 beats/min, 64–77 beats/min, and more than or equal to 78 beats/min, with respective proportions of patients with good outcome at discharge of 18 of 27 (67%), 14 of 25 (56%), 12 of 28 (43%), and 7 of 27 (26%) (p = 0.002). Patients in the lowest quartile had significantly better outcome than the higher groups (p = 0.027), whereas patients in the highest quartile had significantly worse outcome than the lower three groups (p = 0.013).

Conclusions: Bradycardia during therapeutic hypothermia was associated with good neurologic outcome at hospital discharge. Our data indicate that bradycardia should not be aggressively treated in this period if mean arterial pressure, lactate clearance, and diuresis are maintained at acceptable levels. Studies, both experimental and clinical, are warranted.

1Department of Anesthesiology, Division of Emergencies and Critical Care, Oslo University Hospital-Ulleval, Oslo, Norway.

2Institute for Experimental Medical Research, Oslo University Hospital-Ulleval, Oslo, Norway.

3Centre of Heart Failure Research, University of Oslo, Oslo, Norway.

4Department of Acute Medicine, Oslo University Hospital-Ulleval, Oslo, Norway.

5Department of Cardiology, Oslo University Hospital-Ulleval, Oslo, Norway.

* See also p. 2452.

This study was performed at the University of Oslo and Oslo University Hospital Ulleval, Oslo, Norway.

Supported, in part, by grants from South-Eastern Norway Regional Health Authority, Laerdal Foundation, and Oslo University Hospital.

Dr. Sunde received support for lectures and travel from Bard Medical (2012, 2013). Dr. Jacobsen received royalties for the Textbook of Medicine (in Norwegian). Dr. Naksted lectured for a University course. The remaining authors have disclosed that they do not have any potential conflicts of interest.

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