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The activity of the autonomic nervous system depends on sleep stage. The imbalance of the autonomic nervous system together with over-reactivity to stimuli has been suggested to be an etiologic factor for infantile colic. This study was designed to estimate the reactivity of the autonomic nervous system to a sleep-time stimulus in non-rapid eye movement (NREM) and rapid eye movement (REM) sleep stages and in colic and control infants. Overnight sleep polygraphic recordings were performed for 12 colic and 14 control infants at the age of 8 weeks. Movements were detected by a static-charge-sensitive bed. Extent of heart rate variability (HRV) was measured in response to spontaneous sleep-related movements. HRV analysis was performed over 2-min segments during NREM and REM sleep before and after 5-36-s long movement periods. Total (0.04-1.0 Hz), low (0.04-0.15 Hz) and high frequency (0.15-1.0 Hz) HRV increased after the movement periods in light NREM sleep (p < 0.001). These changes were not observed in REM sleep. No differences were found between the colic and the control groups in HRV. The observed difference in the response of the HRV between sleep stages is likely to reflect the different characteristics of heart rate control in NREM and REM sleep, but our results do not suggest that colic infants would have abnormal autonomic reactivity to stimuli while asleep.

Unlabelled: Excessively crying, hard-to-soothe infants are described as colicky. The self-limiting course of infantile colic during early infancy suggests an etiology of transient developmental dysmaturation. It has been proposed that emotional characteristics such as temperament and self-soothing ability are correlated with the balance of the autonomic nervous system. Heart rate variability (HRV) analysis was used for evaluating the balance of the autonomic nervous system in colicky and control infants during and after the colicky period. HRV analysis was carried out on 12 colicky infants and 14 control infants at the age of 2 mo, and repeated on 10 colicky and 11 normal infants at the age of 7 mo. Measurements were performed during polygraphically confirmed slow-wave sleep (sleep stages 3 and 4). Three HRV frequency bands were defined, including a high (0.2-1.0 Hz), middle (0.12-0.2 Hz) and low (0.025-0.12 Hz) frequency variability. There were no differences between the study groups in any of the three HRV frequency bands analyzed. The high frequency variability increased significantly with age in both study groups (p = 0.009)., Conclusion: The findings suggest that imbalance between the parasympathetic and the sympathetic nervous system is not associated with infantile colic and that, in accordance with previous findings, control of HRV shifts in a parasympathetic direction with increasing age during the first year of life.

Oscillations of skin blood flow and heart rate can be synchronised using external rhythmic thermal stimulation in healthy adults and infants. We examined the effect of thermal stimulation on the cutaneous circulation and heart rate of an anencephalic neonate using cutaneous laser Doppler flowmetry and ECG monitoring. The results suggest that synchronisation of SBF and HR to thermal stimulation can also be induced in an anencephalic newborn.

The reactivity of skin blood flow and heart rate to periodic thermal stimulation was studied in 10 term small-for-gestational age (SGA) infants, in 9 preterm and 8 term normal-sized infants during the first two postnatal months. During the first postnatal days, the increase in thermally stimulated skin blood flow oscillations was absent in SGA infants but was clearly present in both preterm (p < 0.01) and term (p < 0.01) normal-sized infants. The responsiveness of SGA infants improved during the follow-up (p < 0.05). The response of the periodic heart rate variability of SGA and preterm infants was inferior to term normal-sized infants until the age of 2 months. The cardiovascular responsiveness of growth-retarded infants seems abnormal during the first days of life, and may impair their ability to meet stress, e.g. changes of ambient temperature.

Simultaneous electrocardiogram (ECG) and static charge sensitive bed (SCSB) method recordings were carried out in fifteen healthy and twenty-one neurologically damaged infants during sleep at the age of one week, one month and three months. The SCSB method allows continuous long-term recording of body movements without electrodes connected to the subject. The heart rate response to body movements was studied. Healthy newborns had clear heart rate (HR) acceleration response to body movements. A rapid HR deceleration response occurred at the end of body movements. In the neurologically damaged infants the HR response to body movements was significantly hyperactive or delayed. The abnormal heart rate acceleration-deceleration response to body movements in damaged infants can best be explained by disturbed function of the autonomic nervous system.

The aim of this work was to investigate the usefulness of the individual regression coefficients between the HR and the Q-A2 when studying their relationship during simultaneous changes in afterload and preload in combination with autonomic blockade. Twelve healthy male volunteers were studied in an orthostatic test done four times: without drugs (control test), after atropinization, after beta-blockade, as well as after combined beta-blockade and atropinization. The individual regression coefficients showed great inter-individual variation, and in average they were not significantly different in the four tests. However, it was observed that during the control test four, during the atropinization eight, during the beta-blockade three and during the combined beta-blockade and atropinization five individual regression coefficients were greater than -2.1, which is the regression coefficient used for the rate correction of the Q-A2 in males in the Weissler formula. It seems to use that the individual regression coefficents are useful in the evaluation of the relationship between the HR and the Q-A2 in pharmacological or physiological interventions, in which the intra-individual variation is great, and in which the number of subjects is often so small that group regressions are not very informative.

Instantaneous heart rate, indices of long-term and short-term heart-rate variability (HRV), and transcutaneous O2 (PtcO2) and CO2 (PtcCO2) tensions were recorded simultaneously on 164 occasions in 16 neonates. There was significant inverse correlation between PtcCO2 and both HRV indices, while no linear correlation was detected between HRV and PtcO2. The heart rate was positively related to PtcCO2 and inversely correlated with PO2. It is suggested that increasing PCO2 decreases medullary pH, thus increasing heart rate and decreasing HRV. We conclude that each of these monitoring variables is unique: the transcutaneous measurements display the efficiency of respiration, whereas the heart-rate patterns reflect the dynamic condition of the autonomic nervous system.

Sixteen infants were studied with the static charge sensitive bed (SCSB) method. This method is newly developed for neonatal recordings and it allows recording of body movements, respiration and of the ballistocardiographic signal. Eight healthy newborn infants and eight infants with clear neurological dysfunction were recorded and the heart rate acceleration-deceleration responses to body movements during sleep were studied. Healthy infants had a constant heart rate response to body movements but infants with neurological symptoms had either too weak or hyperactive reactions. This finding can be explained by abnormal function of the autonomic nervous system in infants with disturbance of the central nervous system.

Heart rate variation (HRV) was measured in 12 children with brain death. Computer analysis demonstrated an overall heart rate variation (RMSM) of 3.5 to 9.6 msec (mean, 6.0 msec). The respective figures for beat-to-beat variation (RMSSD) were 4 to 16 msec (mean, 7.7 msec). Normal infants (RMSM, 20 to 30 msec) and children (RMSM, 50 to 90 msec) and infants with respiratory distress syndrome (RMSM, 10 to 20 msec) have a clearly higher HRV than those with brain death. In all subjects a periodic component of the HRV with a cycle length of 5.9 +/- 0.26 seconds was discovered. In five patients an additional periodic component was found that corresponded exactly to the rate of artificial respiration. This study demonstrated the value of accurate digital techniques in the characterization of fixed heart rate in decerebration. This phenomenon could be considered one clinical criterion of brain death.