A tertiary care center's experience with therapeutic hypothermia after pediatric cardiac arrest

Abstract

Objective: To describe the use and feasibility of therapeutic hypothermia after pediatric cardiac arrest.

Design: Retrospective cohort study.

Setting: Pediatric tertiary care university hospital.

Patients: Infants and children (age 1 wk to 21 yrs) without complex congenital heart disease with return of spontaneous circulation after in-hospital or out-of-hospital cardiac arrest from 2000 to 2006.

Intervention: None.

Measurements and main results: We studied 181 patients after cardiac arrest, of which 91% were asphyxial in etiology (vs. cardiac) and 52% occurred in-hospital. Overall survival to hospital discharge was 45%. Forty patients received therapeutic hypothermia; all were admitted during or after 2002. Sixty percent of patients in the therapeutic hypothermia group had an initial temperature <35 degrees C. The median therapeutic hypothermia target temperature was 34.0 degrees C (33.5-34.8 degrees C), was reached by 7 hrs (5-8 hrs) after admission in patients who were not hypothermic on admission, and was maintained for 24 hrs (16-48 hrs). Re-warming lasted 6 hrs (5-8 hrs). In the therapeutic hypothermia group, temperature <32 degrees C occurred in 15% of patients and was associated with higher hospital mortality (29% vs. 11%; p = .02). Patients treated with therapeutic hypothermia differed from those treated with standard therapy, with more un-witnessed cardiac arrest (p = .04), more doses of epinephrine to achieve return of spontaneous circulation (p = .03), and a trend toward more out-of-hospital cardiac arrests (p = .11). After arrest, therapeutic hypothermia patients received more frequent electrolyte supplementation (p < .05). Standard therapy patients were twice as likely as therapeutic hypothermia patients to have a fever (>38 degrees C) after arrest (37% vs. 18%; p = .02) and trended toward a higher rate of re-arrest (26% vs. 13%; p = .09). Rates of red blood cell transfusions, infection, and arrhythmias were similar between groups. There was no difference in hospital mortality (55.0% therapeutic hypothermia vs. 55.3% standard therapy; p = 1.0), and 78% of the therapeutic hypothermia survivors were discharged home (vs. 68% of the standard therapy survivors; p = .46). In multivariate analysis, mortality was independently associated with initial hypoglycemia or hyperglycemia, number of doses of epinephrine during resuscitation, asphyxial etiology, and longer duration of cardiopulmonary resuscitation, but not treatment group (odds ratio for mortality in the therapeutic hypothermia group, 0.47; p = .2).

Conclusions: This is the largest study reported on the use of therapeutic mild hypothermia in pediatric cardiac arrest to date. We found that therapeutic hypothermia was feasible, with target temperature achieved in <3 hrs overall. Temperature below target range was associated with increased mortality. Prospective study is urgently needed to determine the efficacy of therapeutic hypothermia in pediatric patients after cardiac arrest.

Figure 1

Study flowchart. Hypothermia (HT) data are presented as mean ± SD and median (interquartile range). ROSC, return of spontaneous circulation; h, hour; n, number.

Figure 2

Physiologic variables of the hypothermia therapy (HT) group. A, Temperatures of the HT group (mean ± standard error) during the time before HT, HT, re-warming, and after re-warming phases. Because there was no HT protocol, each data point contains a variable number of patients. B and C, Mean arterial blood pressure and heart rate, normalized for age and gender. The arrow in (C) denotes increased heart rate after re-warming.