Early achievement of mild therapeutic hypothermia and the neurologic outcome after cardiac arrest
Introduction
Over the past decades, the prognosis after cardiac arrest (CA) and cardiopulmonary resuscitation (CPR) has remained poor [1], [2]. Those who survive the devastating event, often retain a hypoxic brain injury and a permanently incapacitating neurologic deficit. Recently, mild therapeutic hypothermia (MTH) with a recommended reduction of body core temperature (T) to 33 °C over 12 to 24 h [3] has emerged as a new treatment strategy. Feasibility and safety of MTH have been assessed in several clinical trials [4], [5], [6]. And, since these trials delivered promising results, there is now a growing appreciation that MTH is capable of improving the neurologic outcome after CA [7], [8], [9]. Currently, data on MTH have been derived from clinical trials conducted under tightly controlled or experimental conditions [10], [11]. In the clinical practice, though, the time interval between the occurrence of CA and ensuing resuscitative measures can vary immensely depending on arrest location and daytime. Thus, whereas the overall benefit of MTH is meanwhile substantiated, the impact of the time intervals between CA and MTH on the neurologic outcome has not yet received much attention.
We hypothesized that the clinical benefit of MTH is greater among those patients in whom effective MTH is more rapidly achieved. To test this hypothesis, we analyzed the association of the time intervals from CA to MTH (1: time to cooling, 2: time to target temperature of 33.0 °C [TTT], 3: time to coldest temperature [TCT]) and the neurologic outcome under consideration of clinically relevant confounders. We also examined the correlation between those time intervals and serum levels of neurone specific enolase (NSE), a biochemical marker of brain tissue damage. Body cooling was performed by use of a closed-loop endovascular system which has recently been shown to allow more rapid achievement and more precise control of MTH [12].
Section snippets
Methods
The HELIOS Clinics Schwerin are an academic, regional tertiary-care hospital serving an estimated population of about 500,000 citizens in the German federal state of Mecklenburg-West Pomerania as well as in parts of northwestern Brandenburg. The hospital has a total of 1400 acute-care beds. Tertiary critical-care services include an 11-bed medical ICU for adult patients with non-surgical conditions. The medical ICU is a separate unit staffed by physicians specialized in non-surgical
Results
The study enrolled 49 patients. Fourteen of the 21 patients with poor neurologic outcome died (median survival time: 6 days, 20 h [2 days, 5 h–12 days, 0 h]) after intensive care was withdrawn in agreement with the patient's families. The 7 others remained in a comatose or vegetative state (N = 6) or retained a severe cerebral disability (N = 1) after achieving normothermia.
Discussion
We observed that those patients resuscitated from CA who had lower starting T at the beginning of cooling therapy, who had lower T after 1 h cooling therapy and who reached their coldest T sooner tended to be those with better neurologic outcome. Moreover, we found a correlation between maximum NSE, as a quantitative marker of brain tissue damage, and TCT in which shorter TCT were associated with lower maximum NSE levels. Finally, in multivariate analyses, any hour delay till the coldest T or
Conclusion
According to our data, early achievement of MTH is a determinant of the final neurologic outcome. Thus, measures to speed up the initiation of cooling therapy after CA appear warranted.
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2020, American Journal of Emergency Medicine