Comparability of infant abdominal skin and axillary temperatures

Early detection of cold stress to prevent hypothermia: A narrative review

Temperature monitoring is essential for assessing neonates and providing appropriate neonatal thermal care. Thermoneutrality is defined as the environmental temperature range within which the oxygen and metabolic consumptions are minimum to maintain normal body temperature. When neonates are in an environment below thermoneutral temperature, they respond by vasoconstriction to minimise heat losses, followed by a rise in metabolic rate to increase heat production. This condition, physiologically termed cold stress, usually occurs before hypothermia. In addition to standard axillary or rectal temperature monitoring by a thermometer, cold stress can be detected by monitoring peripheral hand or foot temperature, even by hand-touch. However, this simple method remains undervalued and generally recommended only as a second and lesser choice in clinical practice. This review presents the concepts of thermoneutrality and cold stress and highlights the importance of early detection of cold stress before hypothermia occurs. The authors suggest systematic clinical determination of hand and foot temperatures by hand-touch for early detection of physiological cold stress, in addition to monitoring core temperature for detection of established hypothermia, particularly in low-resource settings.

Comparison of rectal and axillary temperature measurements in preterm newborns

OBJECTIVE

To compare rectal and axillary temperatures in preterm newborns on admission to the neonatal intensive care unit (NICU).

DESIGN

Secondary analysis of data collected in a randomised controlled trial (RCT).

SETTING

Maternity hospital, level 3 NICU.

PATIENTS

Seventy-two newborns <31 weeks who were enrolled in the BAMBINO RCT (A randomised trial of exothermic mattresses to prevent heat loss in preterm infants at birth, ISRCTN31707342).

INTERVENTIONS

Newborns were placed in polyethylene bags and were randomised to placement on exothermic mattresses, or not in the delivery room. All infants had rectal and axillary temperatures measured in immediate succession using a digital thermometer on NICU admission.

OUTCOME MEASURES

Admission rectal and axillary temperatures.

RESULTS

Mean (SD) gestational age was 28 (2) weeks and birth weight was 1138 (374) g. Mean rectal-axillary temperature difference was 0.1 (0.5°C) (range -1.4°C to +1.5°C). Rectal and axillary temperatures differed by ≥0.5°C in 18/72 (25%) infants; axillary temperature was higher than rectal in 6 (8%) and lower in 12 (17%). There was a positive linear relationship between rectal and axillary measurements (Pearson's correlation R=0.84). Applying the Bland-Altman technique, the width of 95% prediction interval was 1.8°C (-0.8°C to 1.0°C) implying that rectal and axillary measurements may vary by up to 1.0°C. Axillary temperature had a sensitivity of 65% when used to detect rectal hyperthermia and 100% sensitivity for hypothermia.

CONCLUSION

Paired rectal and axillary temperature measurements in preterm newborns on NICU admission vary significantly. Axillary temperature was sensitive at detecting rectal hypothermia but not hyperthermia. Axillary temperature may not be an accurate proxy for rectal temperature measurement in all preterm newborns on NICU admission.

Comparing Axillary and Rectal Temperature Measurements in Very Preterm Infants: A Prospective Observational Study

PURPOSE

The agreement between axillary temperature (AT) and rectal temperature (RT) measurements has not been well established in preterm infants. Therefore, our study aimed to evaluate the agreement between AT and RT measurements in very preterm infants.

METHODS

Preterm infants <32 weeks of gestational age were prospectively included. The infants' body temperature (BT) was measured twice a day from day 1 to day 6. A paired t-test and the Bland-Altman method were used to analyze the difference between the AT and RT. A linear regression model was used to explore the effects of environmental factors on the differences of BT between the axillary and rectal measurements and to calibrate the RT according to the AT.

RESULTS

Eighty infants each underwent 6 paired axillary and rectal measurements. The gestational age varied from 22 to 31 weeks (mean 28 weeks). The birth weight varied from 302 to 1,770 g (mean 1,025 g). The AT was significantly lower than the RT. The difference between the RT and AT significantly increased with increasing RT. The AT and RT demonstrated poor agreement overall; however, the RT can be estimated using the AT with the following equation: RT = -4.033 + 1.116 × AT. Environmental factors, including the incubator temperature, incubator humidity, phototherapy, and application of invasive mechanical ventilation did not affect the differences between the AT and RT measurements.

CONCLUSION

AT measurements cannot be interchangeably used with RT measurements in very preterm infants.

Effect of Timing of the First Bath on a Healthy Newborn's Temperature

OBJECTIVE

To determine if a healthy newborn's age in hours (3, 6, or 9 hours after birth) affects thermoregulatory status after the first bath as indicated by axillary and skin temperatures.

DESIGN

Quasi-experimental, mixed-model (between subjects and within subjects) design with hours of age as the nonrepeated variable and prebath and postbath temperatures as the repeated variables.

SETTING

Family-centered care unit at an urban hospital in the southwestern United States.

PARTICIPANTS

Healthy newborns (N = 75) 37 weeks or more completed gestation.

METHODS

Mothers chose time of first bath based on available time slots (n = 25 newborns in each age group). Research nurses sponge bathed the newborns in the mothers' rooms. Axillary temperature, an index of core temperature, was measured with a digital thermometer, and skin temperature, an index of body surface temperature, was measured with a thermography camera. Temperatures were taken before the bath; immediately after the bath; and 5, 30, 60, and 120 minutes after the bath. Immediately after the bath, newborns were placed in skin-to-skin care (SSC) for 60 or more minutes.

RESULTS

We found a difference (p = .0372) in axillary temperatures between the 3- and 9-hour age groups, although this difference was not clinically significant (0.18 °F [0.10 °C]). We found no statistically significant differences in skin temperatures among the three age groups. Regardless of age group, axillary and skin temperatures initially decreased and then recovered after the bath.

CONCLUSION

For up to 2 hours postbath, axillary and skin temperatures were not different between healthy newborns bathed at 3, 6, or 9 hours of age. Thermography holds promise for learning about thermoregulation, bathing, and SSC.

Umbilical temperature correlation with core and skin temperatures at rest, in the heat and during physical activity

PURPOSE

to determine the correlation of umbilical temperatures (T_umb) with simultaneously recorded chest wall temperature (T_chest) and rectal temperature (T_rectal) in adults during rest, heat exposure and exercise.

METHODS

A total of 28 healthy men, wearing different types of clothing (athletic garb, a spandex full body heating garment, firefighter bunker gear) had average and peak umbilical, chest wall and rectal temperature measurements taken during sedentary temperature stabilisation stages, heat exposure periods and active exercise phases.

RESULTS

Curvilinear relationships were noted between T_chest and T_umb compared with T_rectal and their association became noticeably positive and linear at approximately 35.5 °C. Polynomial regression analysis of T_rectal with linear and quadratic forms of T_chest and T_umb indicated an overall R² of 0.657 and 0.767, respectively. Bivariate analysis of a restricted data set (where T_chest and T_umb ≥35.5°), indicated that T_umb was significantly associated with T_rectal (r_average = 0.710, p <0.001; r_peak  = 0.841, p <0.001) and T_chest was also significantly associated with T_rectal, but less so (r_average = 0.570, p <0.001; r_peak = 0.699, p <0.001).

CONCLUSIONS

the umbilicus offers a non-invasive, peripheral site for measurement of temperature that more closely correlated with body core temperature than T_chest when core temperature was ≥35.5 °C.

Ideal Site for Skin Temperature Probe Placement on Infants in the NICU: A Review of Literature

BACKGROUND

Maintaining normothermia and prevention of hypothermia are critical determinants of morbidity and mortality in infants. Noninvasive monitoring of skin temperature using skin temperature probes (STPs) has been a practice in neonatal intensive care units (NICUs) for decades. Incubators and radiant warmers use feedback mechanisms from the STP readings to determine the heat output to maintain normothermia. Placing the STP on an ideal site on the infant's body is essential for optimum servo control of the temperature. More importantly, where is the ideal site for the STP placement? Clinical practice guidelines (CPGs) vary on information regarding the site and proper placement of the STPs. The literature is analyzed to identify evidence for the ideal STP placement on infants in NICUs.

PURPOSE

To review the literature for evidence for ideal placement for skin temperature probe placement on an infant.

SEARCH STRATEGY

OVID/MEDLINE, CINAHL, Cochrane databases, and CPGs were searched to identify research, literature reviews, and guidelines for ideal sites for STP placement. Twenty documents were reviewed.

RESULTS

Guidelines vary in suggested sites for STP placement. The majority of the studies compared temperature measurement between abdomen and axilla. Although a Cochrane review found abdominal skin as an ideal site, other studies did not find any difference between axially and abdominal skin temperature measurements.

IMPLICATIONS FOR PRACTICE AND RESEARCH

Placing the STP on an ideal site is essential for accurate and safe monitoring of skin temperature in infants. NICU nurses are uniquely positioned to undertake research to identify the ideal site for STP placement to guide safe practice and impact optimal neonatal outcome.

Evaluation of the Cadi ThermoSENSOR wireless skin-contact thermometer against ear and axillary temperatures in children

The Cadi ThermoSENSOR skin-contact thermometer measures body temperature continuously and transmits readings wirelessly to a central server. This study evaluated the ThermoSENSOR against ear temperatures (ETs) measured by a Braun ThermoScan ear thermometer and axillary temperatures (ATs) measured by a Terumo digital clinical thermometer. The test participants consisted of 109 children aged 6 months to 16 years from a pediatric ward. The sensor was attached to the lower abdomen at least 15 minutes before the first measurement. ET, AT, and ThermoSENSOR temperatures (TTs) were recorded up to three times at the usual measurement times. The TTs differed from ETs by -0.23 degrees C +/- 0.47 degrees C (mean +/- standard deviation, n = 271) and from ATs by +0.21 degrees C +/- 0.46 degrees C (n = 270). The ETs differed from ATs by +0.43 degrees C +/- 0.42 degrees C (n = 315). These results suggest that the TTs were comparable to the ETs and ATs.