Comparison between Gel Pad Cooling Device and Water Blanket during Target Temperature Management in Cardiac Arrest Patients

Abstract

Background: Target temperature management (TTM) improves neurological outcomes for comatose survivors of out-of-hospital cardiac arrest. We compared the efficacy and safety of a gel pad cooling device (GP) and a water blanket (WB) during TTM.

Methods: We performed a retrospective analysis in a single hospital, wherein we measured the time to target temperature (<34℃) after initiation of cooling to evaluate the effectiveness of the cooling method. The temperature farthest from 33℃ was selected every hour during maintenance. Generalized estimation equation analysis was used to compare the absolute temperature differences from 33℃ during the maintenance period. If the selected temperature was not between 32℃ and 34℃, the hour was considered a deviation from the target. We compared the deviation rates during hypothermia maintenance to evaluate the safety of the different methods.

Results: A GP was used for 23 patients among of 53 patients, and a WB was used for the remaining. There was no difference in baseline temperature at the start of cooling between the two patient groups (GP, 35.7℃ vs. WB, 35.6℃; P=0.741). The time to target temperature (134.2 minutes vs. 233.4 minutes, P=0.056) was shorter in the GP patient group. Deviation from maintenance temperature (2.0% vs. 23.7%, P<0.001) occurred significantly more frequently in the WB group. The mean absolute temperature difference from 33℃ during the maintenance period was 0.19℃ (95% confidence interval [CI], 0.17℃ to 0.21℃) in the GP group and 0.76℃ (95% CI, 0.71℃ to 0.80℃) in the WB group. GP significantly decreased this difference by 0.59℃ (95% CI, 0.44℃ to 0.75℃; P<0.001).

Conclusions: The GP was superior to the WB for strict temperature control during TTM.

Keywords: body temperature; heart arrest; hypothermia; induced hypothermia.

Figure 1.

Patient ratio which reached target temperature every minute is expressed in a Kaplan-Meier curve. Comparisons between the two groups were made using the log-rank test.

Figure 2.

Bar graph representing distribution of temperature during maintenance period. The total length of maintenance phase was divided into three phases: hyperthermia (>34°C), target temperature (32°C-34°C), and hypothermia (<32°C). Water blanket group experienced 119 hours (18.4%) of hypothermia and 37 hours (5.7%) of hyperthermia. Gel pad group experienced 10 hours (1.9%) of hyperthermia.

Figure 3.

The distribution of core temperatures during maintenance of hypothermia by cooling device. (A) Water blanket group. (B) Gel pad group. The difference value from 33°C was analyzed with generalized estimating equation to compensate between the individual patient’s changes of body temperature.