Power Spectrum of Heart Rate Variability in the Geriatric Patients Undergoings Spinal Anesthesia

Han, Jong In

Abstract

OBJECTIVES
Spectral analysis of heart rate variability(HRV) resulted in a characteristic power spectrum with two main regions, a high frequency at 0.15-0.5Hz(HFP) corresponding to the parasympathetic system and a low frequency at 0.017-0.l5Hz(LFP) corresponding to both parasympathetic and sympathetic influences. The ratio of low : high frequency(LFP/HFP) has been postulated as an index of sympathetic activation. We propose that the LFP/HFP ratio will provide important information concerning autonomic nervous system activity during spinal anesthesia especially geriatric patients.
METHODS
LFP, HFP and LFP/HFP were checked in 30 patients at the baseline and 5, 10, 15, 20, 25 and 30 minutes after subarachnoidal block. We divided patients into two groups: group 1 is 15 patients under 60 years old and group 2 is 15 patients over 65 years old, and we compared those parameters in both groups.
RESULTS
Spinal anesthesia did produce a significant decrease in LFP and HFP in both groups. But sympathetic-parasympathetic balance(LFP/HFP) increased at 5 minutes after spinal block. In group 1, LFP/HFP decreased at 10 minutes after spinal block, thereafter increased gradually. In group 2, LFP/HFP decreased at 10, 15 and 20 minutes and increased at 25 and 30 minutes after spinal block.
CONCLUSION
These data suggest that autonomic tone decreased with spinal anesthesia and sympathetic-parasympathetic balance decreased for a long time in geriatric patients.