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

ObjectiveTo assess the autonomic nervous system (ANS) in coma by heart rate variability (HRV).MethodsSixteen 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.ResultsA 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.ConclusionsThe HRV procedure is a powerful tool to assess the ANS in comatose patients.SignificanceHRV is a minimally invasive, low-cost methodology, suitable for assessing the ANS in coma.

► We study comatose patients classified into two subgroups according to the GCS, and compared with a normal control group, by calculating HRV indices in time, frequency and informational domains. ► In general, a notable reduction of HRV variability was found in patients, compared to normal subjects, and significant statistical differences between the subgroups of patients, classified according to GCS scores, were found for HRV indices in all domains. ► Our results are discussed regarding the progressive dysfunction the ANS networks when coma deepens.