Investigations of the rhythmic function of heart rate, blood pressure and temperature in neonates.

Over a period of 24-30 h in 10 min intervals, the systolic diastolic and mean arterial blood pressure, heart rate, rectal and skin temperature were measured simultaneously in 17 full-term babies on the 2nd day of life, and in 11 of them again at the age of 4 weeks. Each profile was analysed individually by the Cosinor method. On the 2nd day of life, a statistically significant circadian rhythm could be detected in 12 of the 17 neonates for systolic blood pressure and heart rate, in 16 for skin temperature and in all 17 neonates for rectal temperature. Summarizing the data of the 17 newborns the circadian rhythm was the most frequent component in all functions. A high portion of ultradian rhythms was observed as well. With increasing postnatal age, the variance of acrophases decreased, particularly for the temperature rhythms. This means that synchronization with the environment is beginning. Furthermore, we found an increase in the mesor of heart rate and blood pressure and an increase in amplitude of temperature.