Abnormal cardiac autonomic activity and complexity in newly diagnosed and untreated hypertensive patients after general anesthesia

To investigate change of cardiac autonomic activity and cardiac complexity during general anesthesia in hypertensive patients, we analyzed electrocard iographic (ECG) data using power spectral analysis and approximate entropy (ApEn). Anesthesia was performed by a mixture of enflurane and nitrous oxid e. From 10 minutes before induction of anesthesia (resting state) until 20 minutes after induction, ECG data were obtained from newly diagnosed and un treated hypertensive (n = 18) and normotensive patients (n = 18). Period 1 was defined as the initial 10 minutes after induction and period 2 as the f ollowing 10 minutes. The low-, mid-, and high-frequency power and the value s of ApEn of the two groups were calculated from ECG recording. At resting state, the powers in all frequency bands and the values of ApEn in hyperten sive patients did not differ from those of normotensive patients. During pe riods 1 and 2, the powers of all frequency range significantly decreased in normotensive group (p<0.05), while they did not change in hypertensive gro up. The values of ApEn in normotensive patients decreased significantly onl y during period 2, while those in hypertensive patients decreased during pe riods 1 and 2 (p<0.05 and p<0.05, respectively). These results suggest that , in the hypertensive patients, persistent autonomic activity under the con dition of suppressed cardiac complexity may contribute to the unstable hemo dynamic insults from the outset of general anesthesia