Effect of increased radiant warmer power output on state of hydration in the critically ill neonate

To correlate radiant warmer bed power output with state of hydration in the critically ill infant, warmer power input was measured by a wattmeter and recorded by an on-line computer every 5 sec for 2 periods of 8-24 h each in 11 newborns with respiratory distress syndrome (mean birth weight 1.42 kg, mean gestational age 31.4 weeks). The 2 periods were compared to define a high and a low radiant power period. Fluid intake and urine output, urine and serum osmolalities, serum electrolytes, and free water clearance during each study period (high vs low radiant power) were also compared. Mean radiant power density received during periods of high radiant power output (8.93 mw/cm2) was significantly greater than during periods of low radiant power output (7.85 mw/cm2, p less than 0.001). Mean urine osmolality and fluid intake to output ratio were also significantly increased during periods of high radiant power density. There was a trend toward increased serum osmolality and decreased free water clearance during periods of high radiant power; however, these differences were not significant. This study suggests that prospective measurement of radiant power density delivered to critically ill newborns may be clinically significant in predicting an infant's state of hydration.