Preoperative ultra short-term entropy predicts arterial blood pressure fluctuation during the induction of anesthesia

BACKGROUND: In this study, we sought to determine whether the preoperative nonlinear index of heart rate variability, ultra short-term entropy (UsEn), could predict cardiovascular responses to the induction of general anesthesia. METHODS: UsEn was estimated by a linearized version of the nonlinear least squares method combined with the maximum entropy spectral analysis method (MemCalc method). Preoperative UsEn of 46 patients (ASA PS 1 or 2, aged 40-60 yr) without a history of hypertension was evaluated using the MemCalc method. Patients were assigned to two groups according to preoperative UsEn (Group LOW; UsEn <45, Group HIGH; UsEn ≥45). Anesthesia was induced with propofol, fentanyl and vecuronium bromide and endotracheal intubation was performed. Hemodynamic fluctuations during the induction of anesthesia were recorded and compared between the two groups. RESULTS: It was found that arterial blood pressure fluctuations during the induction of anesthesia were significantly greater in patients with a low UsEn. CONCLUSION: UsEn could predict arterial blood pressure fluctuations during the induction of anesthesia.