Objective: To determine whether bundling elevates rectal and/or skin temperature of young infants.
Design: Randomized, prospective study stratified by age.
Setting: Clinical Studies Center at a teaching hospital in Los Angeles.
Patients: Sixty-four well, full-term infants (ages 11 to 95 days).
Interventions: Control infants (n = 28) were dressed in a disposable diaper and terry coveralls. Bundled infants (n = 36) were dressed as control infants, plus a cap, a receiving blanket, and a thermal blanket. All infants were monitored in an open crib (room temperature 72 degrees to 75 degrees F). Rectal and skin (anterior mid-lower leg) temperatures and infant states were measured at 5-minute intervals from time 0 to 60 minutes and at 62 and 65 minutes.
Results: The mean skin temperature of bundled infants increased by 2.67 degrees C/hr; mean rectal temperature increased by 0.06 degrees C/hr. The mean skin temperature of nonbundled infants increased by 1.5 degrees C/hr; mean rectal temperature decreased by less than 0.01 degree C/hr. Comparing bundled infants to nonbundled controls, there was a significant rise in skin temperature (P = .0001) but not in rectal temperature (P > .05, Wilcoxon rank sum test). The study had a power > 98% to detect a rise of .5 degrees C in rectal temperature over 60 minutes. The 95% confidence interval for the change in rectal temperature in bundled infants was -0.03 to +0.15 degrees C.
Conclusions: Bundling a healthy infant in a temperate external environment causes an increase in skin temperature, but not in rectal temperature. Elevated rectal temperatures should therefore, rarely if every be attributed to bundling.