Evaluation of cardiac autonomic function using heart rate variability in children with acute carbon monoxide poisoning.

Abstract

The present study included 40 children aged 1-17 years who were admitted to the Pediatric Intensive Care Unit with acute carbon monoxide poisoning and 40 healthy age- and sex-matched controls. Carboxyhaemoglobin and cardiac enzymes were measured at admission. Electrocardiography was performed on admission and discharge, and 24-hour Holter electrocardiography was digitally recorded. Heart rate variability was analysed at both time points - 24-hour recordings - and frequency domains - from the first 5 minutes of intensive care unit admission. Time domain and frequency indices such as high-frequency spectral power and low-frequency spectral power were similar between patient and control groups (p>0.05). The ratio of low-frequency spectral power to high-frequency spectral power was significantly lower in the carbon monoxide poisoning group (p<0.001) and was negatively correlated with carboxyhaemoglobin levels (r=-0.351, p<0.05). The mean heart rate, QT dispersion, corrected QT dispersion, and P dispersion values were higher in the carbon monoxide poisoning group (p<0.05) on admission. The QT dispersion and corrected QT dispersion remained longer in the carbon monoxide poisoning group compared with controls on discharge (p<0.05). The frequency domain indices, especially the ratio of low-frequency spectral power to high-frequency spectral power, are useful for the evaluation of the cardiac autonomic function. The decreased low-frequency spectral power-to-high-frequency spectral power ratio reflects a balance of the autonomic nervous system, which shifted to parasympathetic components.