Heart Rate Variabilty and Fentanyl Administration

This pilot study investigates the effect fentanyl has on heart rate variability (HRV) in the operating theatre. Many studies on the effect of anaesthetic agents on HRV include fentanyl in the anaesthetic mix but few studies look at the effect of fentanyl in isolation. HRV uses changes in heart rate to indirectly observe changes in the activity of the autonomic nervous system and in particular, the relative changes in activity of the parasympathetic and sympathetic branches. Patients were studied in the 10 minutes before anaesthesia was induced with continuous ECG recording. A randomly selected dose of fentanyl was administered after 5 minutes. Preliminary results with spectral analysis reveal a small effect on HRV with fentanyl administration. LF and HF power both decrease immediately after fentanyl administration and the LF/HF ratio slowly rises over a longer time period. This effect can be masked by application of the oxygen mask at the time of fentanyl administration.