[Changes in heart rate during and after enflurane-nitrous oxide anesthesia]

Changes in heart rate of 21 patients who received enflurane-nitrous oxide anesthesia were studied. They had no cardiac, pulmonary, nervous system and endocrine diseases. We measured coefficient of variation of R-R intervals (CV) and power spectrum of heart rate fluctuation in 6 periods, (1) control phase (the day before operation), (2) during operation under enflurane-nitrous oxide anesthesia, (3) ten minutes after endotracheal extubation, (4) sixty minutes after arrival in the recovery room, (5) the next morning and (6) the next evening. The patients who were 15-25 years old, showed larger value of CV and larger power of low frequency component (0.03-0.1 Hz, LFC) as well as high frequency component (0.2-0.45 Hz, HFC) compared with patients who were 40-50 years old during control phase. They showed a significant decrease of CV, LFC and HFC in period (2), (3) and (4) but not in (5) and (6). These evidences show that autonomic nervous system is impared after enflurane-nitrous oxide anesthesia until the next morning.