Optimal body temperature in transitional extremely low birth weight infants using heart rate and temperature as indicators.

OBJECTIVE

To explore body temperature in relationship to heart rate in extremely low birth weight (ELBW) infants during their first 12 hours to help identify the ideal set point for incubator control of body temperature.

DESIGN

Within subject, multiple-case design.

SETTING

A tertiary neonatal intensive care unit (NICU) in North Carolina.

PARTICIPANTS

Ten infants born at fewer than 29 weeks gestation and weighing 400 to 1,000 g.

METHODS

Heart rate and abdominal body temperature were measured at 1-minute intervals for 12 hours. Heart rates were considered normal if they were between the 25th and 75th percentile for each infant.

RESULTS

Abdominal temperatures were low throughout the 12-hour study period (mean 35.17-36.68 degrees C). Seven of 10 infants had significant correlations between abdominal temperature and heart rate. Heart rates above the 75th percentile were associated with low and high abdominal temperatures; heart rates less than the 25th percentile were associated with very low abdominal temperatures. The extent to which abdominal temperature was abnormally low was related to the extent to which the heart rate trended away from normal in 6 of the 10 infants. Optimal temperature control point that maximized normal heart rate observations for each infant was between 36.8 degrees C and 37 degrees C.

CONCLUSIONS

Hypothermia was associated with abnormal heart rates in transitional ELBW infants. We suggest nurses set incubator servo between 36.8 degrees C and 36.9 degrees C to optimally control body temperature for ELBW infants.