Neonatal hyperthermia and thermal stress in low- and middle-income countries: a hidden cause of death in extremely low-birthweight neonates.

BACKGROUND

Over 70% of neonatal deaths in Nigeria occur within the first 7 days of life and, despite the millennium development goals, there has been no significant reduction of this figure.

OBJECTIVE

To investigate how rapid changes of temperature outside the physiologically allowable range in extremely low-birthweight infants are associated with increased mortality.

METHODS

Ninety-eight neonatal cases in three Nigerian tertiary-care hospitals were retrospectively recruited; on the basis of birthweight  < 1500 g, this number was reduced to 41 for a two-stage analysis. In the first stage, 34 cases recruited over 24 months were analysed. In the second stage, seven cases recruited over 6 months were analysed; these were neonates managed with a new temperature control technique (the 'handy approach') to enable comparison of outcomes. The mean (SD) birthweight of the infants analysed was 991 g (251), and 28 of them were of extremely low-birthweight (ELBW) [mean (SD) 846 g (128)]. A lifetime temperature plot with a clearly visible reference zone was developed, from which all thermal stresses and their duration associated with mortality were identified and defined on the basis of their characteristics. Methods of quantifying the magnitude and duration of these thermal stresses were devised to enable definition of critical values. This was then applied to calculate a measure of the various thermal stresses which may have contributed to neonatal death.

RESULTS

Hypothermic events were very common in all the infants in the study period, but were not significantly associated with mortality. However, hyperthermic events occurred in 35% of the infants and were more likely to be associated with mortality. Most neonates with prolonged hypothermia culminating in rapid hyperthermia survived. However, all ELBW neonates who experienced prolonged hyperthermia culminating in rapid hypothermia died within 8 hours of the event. There was greater ELBW survival (6/6) in the second stage using the 'handy approach' than in the first stage (2/22).

CONCLUSION

Hyperthermia is a high-risk event in ELBW infants and methods of cooling a high and prolonged temperature must be reviewed.