Effects of dexmedetomidine on changes in heart rate variability and hemodynamics during tracheal intubation

Sympathetic hyperactivation during tracheal intubation prolongs the QT interval and increases the risk of arrhythmias. We investigated if dexmedetomidine pretreatment affected autonomic nervous system balance and QT intervals during intubation. Sixty-six patients were randomized to receive 1.0 g/kg fentanyl (group F, n 22), 0.5 g/kg dexmedetomidine (group D0.5, n 22), or 1.0 g/kg dexmedetomidine (group D1.0, n 22) before induction. Autonomic nervous system balance was assessed by the ratio of low-frequency/high-frequency (LF/HF) power for heart rate variability at baseline (T0), before intubation (T1), and after intubation (T2). QT intervals were corrected by the Bazett's formula (QT c) and compared at baseline, before intubation, and 1, 2, and 3 minutes after intubation. The LF/HF ratio was higher after intubation compared with that at T0 in group F (P < 0.001). There were no significant changes in groups D0.5 and D1.0. The LF/HF ratio was significantly higher in group F compared with those in groups D0.5 and D1.0 after intubation (7.9 vs. 2.1 and 2.5; P < 0.001). The heart rate was increased for 3 minutes after intubation in group F, whereas only for 1 minute after intubation in groups D0.5 and D1.0, compared with that at baseline. More patients in group F had QT c greater than 440 ms compared with that in group D0.5 or D1.0 (8 vs. 1 and 2; P 0.005) at 1 minute after intubation. In contrast to 1.0 g/kg fentanyl, pretreatment with 0.5 or 1.0 g/kg dexmedetomidine suppressed sympathetic hyperactivity and attenuated QT c prolongation during intubation.