Comparison of Rectal, Axillary, Abdominal Skin and Tympanic Membrane Temperature Measurements in Term and Preterm Neonates

Abstract

A quasi-experimenal study was conducted to investigate the optimum time and accuracy of temperature measurements from four sites: rectum (2.5 cm and 3 cm beyond the anus in preterm and term neonates, respectively), axilla (with mercury-in-glass thermometers), abdominal skin (with Duotemp Temperature Monitor), and tympanic membrane (with FirstTemp Genius Infrared Tympanic Thermo-meter in the rectal-equivalent mode). A convenience sampling technique was utilized to enroll 109 neonates, 52 stable preterm and 57 healthy term neonates from a nursery of a university medical center. Simultaneous measurements were made at the four sites by three observers. Each infant was studied only once. The highest temperatures were recorded when temperature readings remained unchanged for two minutes. The findings demonstrated that the rectal temperature was significantly higher than the axillary (mean differences of 0.06 and 0.09 ^oC in preterm and term neonates, respectively) and the abdominal skin temperatures (0.3 ^oC in preterm and 0.2 ^oC in term neonates). However, the differences between rectal and axillary temperatures were considered no clinical significance. Tympanic temperatures were significantly higher than the rectal. The mean differences between tympanic and rectal temperatures varied widely depending on the ear side (0.88 and 0.52 ^oC for protected ears, 0.63 and 0.21 ^oC for exposed ears in preterm and term infants, respectively). The temperatures of preterm neonates were not significantly different from the term neonates measured at rectum, axilla, and abdominal skin. Preterm neonates required shorter times to achieve highest temperatures at all sites. There were significant differences in the mean times of axillary and abdominal skin measurements between preterm and term neonates. The mean times of placement in preterm and term neonates, 2.8 and 3.4 minutes for rectum, 5.4 and 7.9 minutes for axilla, and 4.0 and 6.1 minutes for abdominal skin, were considered the optimum times since 91 to 100 per cent of neonates had temperature readings within their highest temperatures - 0.1 ^oC.
Conclusion : The axillary temperature is as accurate as rectal temperature measured with mercury- in-glass thermometer if the placement times are optimum. The rectal temperature equals the abdominal skin plus 0.3 ^oC for preterm and plus 0.2 ^oC for term neonates. Temperatures obtained with infrared tympanic thermometer in the rectal equivalent mode do not accurately reflect and is not recommended to substitute for rectal temperatures in neonates.