Can baroreflex sensitivity and heart rate variability predict late neurological outcome in patients with traumatic brain injury?

Background: Previous studies have suggested that depressed heart rate variability (HRV) and baroreflex sensitivity (BRS) are associated with early mortality and morbidity in patients with acute brain injuries of various etiologies. The aim of the present study was to assess changes in HRV and BRS in isolated traumatic brain injury (TBI), with the hypothesis that measurement of autonomic nervous system dysfunction can provide prognostic information on late neurological outcome.

Materials and Methods: Nineteen patients with TBI, requiring mechanical ventilation, sedation and analgesia, and with arterial and intracranial pressure monitoring for at least 1 week, were included. Physiological and treatment variables were collected and power spectral analyses of HRV and BRS analyses in time domain were performed daily. HRV in the high-frequency (HF) and low-frequency (LF) domains, as well as LF/HF ratio and total power, were investigated. The power of these variables to predict poor (Glasgow Outcome Scale Extended [GOSE] score <5), late (1 y) neurological outcome was assessed.

Results: Total power, LF, HF, and BRS were all significantly depressed in patients with GOSE score <5. This difference could not be explained by a more severe brain injury at admission or more extensive use of sedative or analgesic drugs. The autonomic variables predicted the late neurological outcome with areas under the receiver-operating curves between 0.78 and 0.83 (sensitivity: 0.63 to 0.88 and specificity: 0.73 to 0.82).

Conclusions: HRV and BRS measures in TBI patients during intensive care treatment, including sedative, analgesic, and vasoactive drugs, may identify patients with poor late neurological outcome.