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Analysis of heart rate variability to assess hemodynamic alterations following induction of anesthesia

1992; Elsevier BV; Volume: 6; Issue: 6 Linguagem: Inglês

10.1016/1053-0770(92)90045-9

1532-8422

Fawzy G. Estafanous, José M. Brum, Marcio P. Ribeiro, Marc Estafanous, Norman J. Starr, Carlos M. Ferrario,

Hemodynamic Monitoring and Therapy

Extensive changes in hemodynamics and cardiac rhythm during induction of anesthesia may be mediated by altered responses of the autonomic nervous system to anesthetic agents. Analysis of the power spectrum of the heart rate (PSHR) variability can supply information about the autonomic nervous system, and may be used in order to assess this phenomenon. In this study, 78 patients undergoing coronary artery bypass graft surgery were evaluated. Anesthesia was induced with sufentanil, and neuromuscular blockade with vecuronium, a combination that may cause a decrease in heart rate. Before and after induction of anesthesia, the heart rate (HR), blood pressure (BP), cardiac output (CO), cardiac index (CI), and PSHR components were recorded. PSHR was obtained by using a special algorithm and data acquisition system for real-time spectral analysis. A low-frequency component (LFa, mainly sympathetic) was analyzed from a band of 0.04 Hz to 0.1 Hz. A high-frequency component (RFa, parasympathetic) was identified by the respiratory frequency spectrum. Alterations of the heart rate after induction of anesthesia were defined in order to separate the patient population into two groups: slow heart rate (slow-HR) and stable heart rate (stable-HR). Slow heart rate was defined as a decrease in HR of more than 20% of the baseline value. The variables were analyzed and compared between the slow-HR (n = 25) and stable-HR (n = 53) groups in order to verify the possibility of identifying patients prone to hemodynamic changes after anesthesia induction. There were no differences in preoperative HR, BP, CO, or Cl between groups before anesthesia induction. However, the PSHR analysis showed (mean ± SE) a higher LFa/RFa (sympathetic/parasympathetic index) ratio in the slow-HR (7.30 ± 1.31) than in the stable-HR (4.38 ± 0.63) population. The LFa component was not significantly different between groups. The RFa in the slow-HR group (0.34. ± 0.08 BPM2) was lower than in the stable-HR group (1.04 ± 0.22 BPM2) before induction of anesthesia. These data showed that patients who developed a slow HR following induction of anesthesia had a lower parasympathetic component of heart rate variability than patients who maintained a stable heart rate. This investigation suggests that PSHR may identify patients at high risk of developing hemodynamic alterations following anesthesia.