Can skin temperature replace rectal temperature monitoring in babies undergoing therapeutic hypothermia in low‐resource settings?

In low-resource settings, where the majority of asphyxial deaths occur, the mandatory measuring of core temperature may not always be practical when practicing therapeutic hypothermia (TH). If a standardized measurement of skin temperature could replace core temperature monitoring, it would make cooling more feasible. In normothermic newborn, axillary temperature measurements are the standard of care (1). Further studies have shown that insulated back temperature using the zero heat flow method correlates well with rectal temperature and can be used as a measure of core temperature (2–4). However, none of the studies comparing the agreement of skin and rectal temperature included babies who were hypothermic. The only studies that have looked at cooled babies have used correlation as a measure, which does not mean that the agreement is within acceptable limits (5,6). The aim of our study was to look at the correlation and agreement of skin temperature with rectal temperature, postulating that skin temperature could replace rectal temperature monitoring in babies undergoing therapeutic hypothermia. This was a method comparison study conducted in a level 3 neonatal unit of a tertiary care teaching hospital in south India from November 2008 to August 2011. All babies who underwent whole-body cooling for perinatal asphyxia were included. The details of the inclusion criteria and the low cost method of cooling used have previously been described (7). The institutional review board, ethics committee approval and patient consent were obtained prior to cooling babies. In all babies who underwent therapeutic hypothermia, a rectal probe (Philips-ref no 21090A or Drager-ref no 4329848-08) to monitor core temperature was inserted 5 cm within the rectum and connected to a multi-parameter monitor [Philips Intellivue MP20 (Philips, Bobleign, Germany) or Drager vista XL (Drager, Telford, PA, USA)]. Temperature was continuously monitored and recorded every 15 min for 4 h and then subsequently every hour for 80 h until re-warming was completed. The skin temperature measured was either axillary temperature or insulated back temperature. In 20 babies, the axillary temperature was measured simultaneously at the time of the rectal temperature recording using an electronic thermometer [Terumo-C 27 (Terumo corporation, Shizuoka, Japan)], which was placed in the apex of the axilla, arms adducted and reading taken after 3 min. In the subsequent 20 babies, the insulated back temperature (zero heat flow method) was continuously monitored using a skin probe (Drager-ref no 7498921), which was placed lateral to the spine just below the level of the scapula and recorded at the same time as the rectal temperature. All data were recorded in the study form and entered into an excel spread sheet. Data were analysed using SPSS 16.0 for windows (SPSS Inc, Chicago, IL, USA). Linear regression analysis and correlation coefficients were calculated to assess the relation between rectal and skin temperature. Reliability analysis was performed using intraclass correlation (ICC). The primary outcome we looked at was the agreement between rectal and skin temperature measurements using the method suggested by Bland and Altman (8). A BlandAltman plot of bias (rectal minus skin temperature for each outcome at each time point) versus average of each pair of measurement was created. From this, the mean bias (accuracy) and the 95% limits of agreement (precision) were calculated. The limits of agreement are used to estimate where 95% of future differences of skin temperature measurements Acta Pædiatrica ISSN 0803–5253