Table 2. Regression Model Results.

	Esophageal/Axillary Temperatureb (n=343 observations)					Esophageal Temperatureb (n=190 observations)
Heart Rate Metrica	t-value	P-value	Adjustedc t-value	Adjustedc p-value	Significant Covariates	t-value	p-value	Adjustedc t-value	Adjustedc p-value	Significant Covariates
Median RRi	-13.57	<0.001	-14.02	<0.001	pH	-9.04	<0.001	-8.95	<0.001
SDNN	-0.73	0.464	-0.77	0.440		-1.21	0.2274	-1.26	0.2105	Gender
LF Power	-3.29	0.001	-3.35	0.001	Enceph	-2.32	0.022	-2.28	0.024	Enceph
HF Power	0.03	0.978	0.07	0.945		-0.47	0.6379	-0.72	0.4748	Enceph
DFA αS	-3.28	0.001	-3.31	0.001	Enceph	-1.35	0.1803	-1.23	0.2203	Enceph
DFA αL	4.34	<0.001	4.30	<0.001	Enceph	3.42	<0.001	3.38	<0.001
DFA RMSS	-10.50	<0.001	-10.38	<0.001	Enceph, pH	-4.66	<0.001	-4.81	<0.001
DFA RMSS	-8.33	<0.001	-8.23	<0.001	Enceph	-4.41	<0.001	-4.39	<0.001	Enceph

RRi= cardiac beat-to-beat intervals; SDNN= standard deviation of RRi; LF= low frequency; HF= high frequency; DFA- detrended fluctuation analysis; α= alpha exponent; S= short time scales; L= long time scales; RMS= root mean square.

^aDependent variable;

^bIndependent variable;

^cAdjusted for birth weight, gestational age, gender, encephalopathy grade at presentation (Enceph), presenting pH, hypotension (need for inotropes)