Correlating changes in body temperature with infectious outcome in febrile children who receive acetaminophen.

We reviewed the body-temperature patterns of 140 children ages 2 to 24 months who had fever > or = 39.0 degrees C, received acetaminophen 10 to 15 mg/kg, and had their temperatures remeasured 60 to 90 min later. The children comprised three groups: 22 had bacterial meningitis; 59, isolated bacteremia; and 59, nonbacterial febrile illness. Percentages of patients who became afebrile (temperature < 38.0 degrees C) after receiving acetaminophen were not significantly different among the three groups. Differences in mean temperature decrease after antipyretic was given were significant within each group but not between groups. An inverse relation (P < .004) between patient age and magnitude of temperature was revealed by the following formula: degrees C of defervescence = 1.66 - (0.028 x patient age in months). Thus, highly febrile young children with and without invasive bacterial infections who receive a therapeutic dose of acetaminophen experience a significant temperature drop after 60 to 90 min but do not commonly defervesce to an afebrile state. The degree of defervescence is age-dependent and does not distinguish between infectious outcomes.