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How much tachycardia in infants can be attributed to fever?
Colleen M Hanna1, David S Greenes
1Division of Emergency Medicine, Children's Hospital Boston, Harvard Medical School, Boston, MA 02115, USA.
Insights
In infants aged 2 months and older, pulse rate rises with body temperature. A 1°C increase in temperature correlates with a 9.6 beats/min rise in infant pulse rate.
Area of Science:
- Pediatrics
- Physiology
Background:
- Fever is common in infants.
- Understanding the relationship between temperature and heart rate is crucial for diagnosis.
Purpose of the Study:
- To test if infant pulse rate increases linearly with body temperature.
- To quantify the pulse rate increase per degree Celsius rise in temperature.
Main Methods:
- Prospective enrollment of infants under 1 year in a pediatric emergency department.
- Measured rectal temperature and pulse rate in sleeping or quiet infants.
- Excluded crying/fussy infants and those with conditions causing tachycardia.
Main Results:
- Pulse rate increased linearly with temperature in infants older than 2 months (r²=0.102 to 0.376).
- For infants 2-12 months, pulse rate increased by 9.6 beats/min per 1°C rise in temperature (adjusted r²=0.225).
- Significant individual variation in pulse rate was observed.
Conclusions:
- Infant pulse rate correlates linearly with body temperature in infants aged 2-12 months.
- A 1°C temperature increase predicts a 9.6 beats/min pulse rate increase.
- Wide pulse rate variability exists among infants at any given temperature.
Study Objectives:
We evaluate the hypothesis that pulse rate increases linearly with increased body temperature in infants and determine how much tachycardia in infants can be explained by a 1 degrees C (1.8 degrees F) increase in body temperature.
Methods:
Infants younger than 1 year and presenting to a pediatric emergency department were prospectively enrolled. Rectal temperature and pulse rate were measured. Research personnel rated behavioral state as sleeping, awake and quiet, fussy, or crying. Patients were excluded if they were fussy or crying or if they had any medical condition expected to cause tachycardia. The remaining patients were divided into 6 age-based groups. Linear regression analysis of pulse rate and temperature was performed for each group.
Results:
Four hundred ninety patients were enrolled. Pulse rate increased linearly with temperature in all age groups older than 2 months (adjusted r2=0.102 to 0.376) but not in infants younger than 2 months (adjusted r2=0.004). In infants aged 2 months or older, a multivariate linear regression model adjusted for age showed that pulse rate increased an average of 9.6 beats/min (95% confidence interval 7.7 to 11.5) per 1 degrees C (1.8 degrees F) increase in temperature (adjusted r2=0.225). At any given temperature, the prediction interval for an individual's pulse rate had a span of approximately 64 beats/min.
Conclusion:
In infants 2 to 12 months of age, pulse rate increases linearly with body temperature, with a mean increase of 9.6 beats/min for each 1 degrees C (1.8 degrees F) increase in body temperature. Pulse rates of individual infants vary greatly, however, with a broad range of pulse rates observed at any given temperature.
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