Heart rate variability in neonates with hypoxic ischemic encephalopathy.

Objective: To evaluate the changes in heart rate variability (HRV) in newborns with hypoxic-ischemic encephalopathy (HIE).

Methods: Twenty-two newborns (14 boys, 8 girls) with moderate or severe HIE and 24 term neonates with similar gestational and postnatal age for control were included in this study. Normalized low and high frequency components of HRV and their ratio were evaluated for 24-h in newborns with HIE and control subjects.

Results: The newborns with hypoxic-ischemic encephalopathy had significantly lower normalized low frequency (LFn) and low frequency (LF) / high frequency (HF) values and higher normalized high frequency (HFn) values when compared with the control babies. In addition, when the cases with severe HIE are compared with those of moderate HIE, decreased LFn, LF/HF values and also increased HFn values were present in the severe cases.

Conclusions: HIE is associated with reduced sympathetic nervous system activity, and increased parasympathetic nervous system activity and these activities also correlate with the severity of the disease.