This study was undertaken to elucidate the effects of general anesthesia by power spectral analysis of heart rate variability in diabetic and non-diabetic patients.

EKG was measured in 35 patients, 17 without diabetes (control group) and 18 with diabetes (DM group). EKG and signal were digitized at 500 Hz for; 3 min in the period before anesthesia, during 1 to 5 min after intubation, 5 to 10 min after intubation and 30 min after skin incision. We also measured systolic and diastolic blood pressure, and heart rate in each period. The signal was analyzed using a fast Fourier transform algorithm to yield the power spectrum of the heart rate variability. Low frequency (LF, 0.04-0.15 Hz), high frequency (HF, 0.15-0.5 Hz) powers and the LF/HF ratio were obtained.

The blood pressure was increased transiently by tracheal intubation but decreased gradually while anesthesia progressed. To maintain a minimal pressure range, ephedrine 10mg was injected into 11 patients in the DM group. Heart rate also showed the same trend as blood pressure, and no difference between the two groups. LF and HF power of heart rate variability, which was measured before induction, were significantly decreased in the DM group compared to the control group. As anesthesia was applied, overall frequency power was significantly attenuated in both groups. As the operation proceeded, frequency power gradually recovered only in the control group. Changes of the LF/HF ratio in the control group were 2.58±0.62 at pre-induction and 5.47±1.36, 1.11±0.33, 1.03±0.21 successively and in the DM group were 3.21±0.76 at pre-induction and 4.92±2.55, 0.80±0.18, 0.56±0.16 as the anesthesia progressed.

These results suggest that the heart rate variability is significantly attenuated when anesthetics are administered, and that in the DM group heart rate variability is more prominently attenuated than in the control group. This result implies that diabetic patients have an underlying impairment of autonomic nervous system function and that this may lead to a further impairment of autonomic control, which has the potential to allow substantial intraoperative blood pressure liability during periods of surgical stress or blood loss.