Heart rate variability for assessing comatose patients with different Glasgow Coma Scale scores.

OBJECTIVE To assess the autonomic nervous system (ANS) in coma by heart rate variability (HRV). METHODS Sixteen comatose patients and 22 normal subjects with comparable ages and genders were studied. Patients were classified in two subgroups according to the Glasgow Coma Scale (GCS). Time, frequency, and informational HRV domain indices were calculated. RESULTS A notable reduction of HRV was found in patients. Regarding the time domain indices, the triangular index, and the Delta_RRs, were significantly reduced in the subgroup with GCS=3. Absolute power for the whole frequency spectrum decreased whenever GCS scores were lower. A significant decrement was found for absolute power of the VLF and LF bands in the subgroup of GCS=3, and although it was lower for the HF band in these patients, those changes were not statistically significantly different. The LF/HF ratio and the Shannon´s entropy indices were significantly reduced in the subgroup with GCS=3. Our results are discussed regarding the progressive dysfunction the ANS networks when coma deepens. CONCLUSIONS The HRV procedure is a powerful tool to assess the ANS in comatose patients. SIGNIFICANCE HRV is a minimally invasive, low-cost methodology, suitable for assessing the ANS in coma.