Canadian Journal of Anaesthesia

, Volume 42, Issue 11, pp 1003–1009 | Cite as

Differential effects of ketamine and midazolam on heart rate variability

  • Toru Komatsu
  • Prabhat K. Singh
  • Tomomasa Kimura
  • Kimitoshi Nishiwaki
  • Kenji Bando
  • Yasuhiro Shimada
Reports of Investigation


Alterations in autonomic activity caused by anaesthesia can be assessed by spectral analysis of heart rate variability (HRV). This study examined the effects of ketamine and midazolam on HRV. Thirty patients of ASA PS 1 were studied. Fifteen were given ketamine (2 mg · kg−1) and 15 received midazolam (0.3 mg · kg−1), m The RR intervals of ECG were measured before and after induction of anaesthesia for ten minutes during spontaneous respiration. Power spectral density of the data was computed using fast Fourier transform. The spectral peaks within each measurement were calculated: low frequency area (LF, 0.04–0.15 Hz), high frequency area (HF, 0.15–0.5 Hz), and total power (TP, 0.04–0.5 Hz). Normalized unit power was derived as follows: low frequency area (nuLF): LF/ TP × 100%, high frequency area (nuHF): HF/TP × 100%. Both ketamine and midazolam caused reductions in all measurements of HRV power (P < 0.05). However, ketamine increased nuLF from 64 ± 14% to 75 ± 13% (P < 0.05) and decreased nuHF from 36 ± 14% to 25 ± 13% (P < 0.05), while midazolam decreased nuLF from 66 ± 15% to 54 ± 14% (P < 0.05) and increased nuHF from 34 ± 15% to 46 ± 14% (P < 0.05). These results documented that both ketamine and midazolam reduced the total power and all frequency components of power in spite of their opposing effects on autonomic nervous activity. However, normalized unit power showed the expected sympathetic activation with ketamine and sympathetic depression with midazolam since ketamine increased nuLFand midazolam decreased nuLF.

Key words

anaesthetics: intravenous, ketamine, midazolam autonomic nervous system: sympathetic, parasympathetic measurement techniques: heart rate variability spectral analysis, normalized unit power 


Il est possible de mesurer l’activité autonome initiée par l’anesthésie au moyen de l’analyse spectrale des fluctuations de la fréquence cardiaque (FFC). Cette étude recherche les effets de la kétamine et du midazolam sur les FFC. Trente patients ASA PS I font partie de l’étude. Quinze ont reçu de la kétamine (2 mg · kg−1) et quinze du midazolam (0,3 mg · kg−1) iv. Les intervalles RR ont été mesurés à l’ECG avant et après l’induction de l’anesthésie pendant dix minutes de respiration spontanée. La densité de la puissance spectrale des données a été calculée après transformation rapide sur une échelle de Fourier. Les pointes spectrales de chaque mesure ont été calculées: zone de basse fréquence (LF, 0.04–0,15 Hz), zone de haute fréquence (HF, 0,15–0.5 Hz) et puissance totale (TP, 0,04–0,5 Hz). L’unité de puissance normalisée a été dérivee comme suit: zone de basse fréquence (nuLF): LF/TP × 100%, zone de haute fréquence (nuHF): HF/TP × 100% La kétamine et le midazolam provoquent des réductions de toutes les mesures de puissance des FFC (P < 0,05). Cependant la kétamine a augmenté nuLF de 64 ± 14% à 75 ± 13% (P < 0,05) et a diminue nuHF de 36 ± 14% à 25 ± 13% (P < 0,05), alors que le midazolam a diminué nuLF de 66 ± 14% à 54 ± 14% (P < 0,05) et a augmenté nuHF de 34 ± 15% à 46 ± 14% (P < 0,05). Ces résultats montrent que la kétamine et le diazépam réduisent tous deux la puissance totale et toutes les composantes fréquentielles de la puissance malgré leurs effets opposés sur l’activité nerveuse autonome. Cependant, l’unité de puissance normalisée a montré, comme on s’y attendait, l’activation sympathique par la kétamine et la dépression sympathique par le midazolam étant donné que la kétamine augmentait nuLF et que le midazolam diminuait nuLF.


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Copyright information

© Canadian Anesthesiologists 1995

Authors and Affiliations

  • Toru Komatsu
    • 1
  • Prabhat K. Singh
    • 1
  • Tomomasa Kimura
    • 1
  • Kimitoshi Nishiwaki
    • 1
  • Kenji Bando
    • 1
  • Yasuhiro Shimada
    • 1
  1. 1.Department of AnesthesiologyNagoya University School of MedicineShowaku, NagoyaJapan

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