Using Heart Rate Variability Monitoring for Dexmedetomidine Dosing in Neurointensive Care Patients

Aim : to validate the use of heart rate variability monitoring during dexmedetomidine administration in patients with brain injury of various etiologies. Material and methods . The study included 25 patients (14 male, 11 female, mean age 58.2±1.81 years) 20 and more days after traumatic brain injury (TBI) (n=9; 36%), acute stroke (n=4; 16%), anoxic brain injury (n=6; 24%), subarachnoid hemorrhage (SAH) (n=6; 24%). Dexmedetomidine was prescribed because of sympathetic hyperactivity as diagnosed by heart rate variability (HRV). The following indices were measured: SI (stress index, in normalized units [nu]), SDNN (standard deviation of all normal sinus RR intervals over 24 h, in ms), RMSSD (root-mean-square of successive normal sinus RR interval difference, in ms), pNN 50% (the percentage of successive normal sinus RR intervals >50 ms), TP (total power of the frequency spectrum, in ms2). HRV parameters were determined prior to dexmedetomidine infusion (baseline), on days 1–3, 4–5, 9–10, 15–20 of drug administration. Sympathetic hyperactivity was diagnosed by determining following values: SDNN 900 nu, and TP < 200 ms2. Normal reference ranges for HRV parameters were as follows: SDNN (13.31–41.4 ms), RMSSD (5.78–42.3 ms), pNN5 0% (0.110–8.1%), SI (80–900 nu), and TP (200–2000 ms2). Results . The starting dose of dexmedetomidine for sympathetic hyperactivity was 0.12–0.24 µg/kg/hr (mean dose 0.16±0.01; total 200 µg/day). According to digital HRV data, the effective dose ED50 of dexmedetomidine was 0.26±0.03 µg/kg/hour (353.8±35.1 µg total per day) that was achieved on day 9–10 of drug administration. Conclusion . Electrophysiological neuromonitoring of the autonomic nervous system function increases the efficacy of dexmedetomidine administration in patients with brain injury of various etiologies.