Abstract & Commentary
Spontaneous Hypothermia After Cardiac Arrest Is a Bad Prognostic Sign
By David J. Pierson, MD, Editor, Professor, Pulmonary and Critical Care Medicine, Harborview Medical Center, University of Washington, Seattle, is Editor for Critical Care Alert.
Synopsis: In this observational cohort study of patients admitted to an ICU after resuscitation from cardiac arrest, initial spontaneous hypothermia (T < 35.0° C) was the strongest predictor of an unfavorable neurological outcome among those examined.
Source: den Hartog AW, et al. Spontaneous hypothermia on intensive care unit admission is a predictor of unfavorable neurological outcome in patients after resuscitation: An observational cohort study. Crit Care 2010;14:R121.
This study from the University of Amsterdam reports outcome data on 105 consecutive patients resuscitated from primary cardiac arrest and treated in the ICU with a protocol of induced mild hypothermia. The median ICU admission temperature in these patients was 35.1° C, and the authors assessed neurological outcome in patients with initial temperatures above and below 35° C. Neurologic outcome was assessed at 6 months by means of the Glasgow Outcome Score, with a score of 1 to 3 defined as unfavorable and a score of 4 to 5 as favorable. Logistic regression was used to assess the influence of APACHE II score, sequential organ failure assessment (SOFA) scores, as well as spontaneous hypothermia, on neurologic outcome.
At 6 months, 61% of the patients had an unfavorable outcome: 59% had died and 2% were severely disabled. Thirty-nine percent of the patients had a favorable outcome as defined above. The percentage of patients with an unfavorable outcome was higher among patients admitted to the ICU with spontaneous hypothermia than among those with initial temperatures above 35° C (69% vs 50%; P = 0.05). By logistic regression analysis, age, APACHE II score, and SOFA scores and spontaneous hypothermia on admission were all associated with an increased odds ratio for an unfavorable outcome after 6 months. However, spontaneous hypothermia had the strongest independent association with unfavorable outcome (odds ratio, 2.6; 95% confidence interval [CI], 1.1-5.9), and this association became even stronger when adjusted for age, presenting heart rhythm, APACHE II score, and SOFA score (odds ratio, 3.8; 95% CI, 1.3-11.0). The association between initial spontaneous hypothermia and poor neurological outcome persisted when examined for out-of-hospital vs in-hospital cardiac arrest.
Commentary
Among patients admitted to the ICU with severe sepsis1 and following trauma,2 initial spontaneous hypothermia is associated with worse outcomes. In those settings, hypothermia is thought to be evidence of profoundly altered homeostasis and has been associated with a variety of metabolic disruptions at the cellular level. This study shows that patients resuscitated from cardiac arrest who present to the ICU with spontaneous hypothermia also have a worse prognosis in comparison with patients with a more normal initial body temperature.
This finding should be distinguished from those of several studies that have reported improved neurologic outcomes in patients treated with intentional mild hypothermia following cardiac arrest. The implication here is different: If the patient's ability to maintain internal homeostasis is so profoundly disrupted after cardiac arrest that a near-normal body temperature cannot be sustained, it appears to be a sign of more severe injury overall, as supported by the worse neurologic outcomes documented in this study.
References
- Peres Bota D, et al. Body temperature alterations in the critically ill. Intensive Care Med 2004;30:811-816.
- Wang HE, et al. Admission hypothermia and outcome after major trauma. Crit Care Med 2005;33:1296-1301.
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