Does heart rate variability predict hypotension and bradycardia after induction of general anaesthesia in high risk cardiovascular patients?

Abstract

This study investigated whether heart rate variability predicts haemodynamic events in high risk patients, defined as Revised Cardiac Risk Index score = 3, scheduled for general anaesthesia. Fifty patients underwent baseline measurement of heart rate variability and were then assigned according to haemodynamic events (hypotension or bradycardia) after standardised induction of anaesthesia into 'stable' (n = 39) and 'unstable' patients (n = 11). Unstable patients had significantly lower baseline total power. Total power < 500 ms2 x Hz(-1) was associated with high sensitivity and specificity for the prediction of hypotension or bradycardia. Prospectively, 29 patients with total power < 500 ms2 x Hz(-1) were compared with 21 patients with total power > 500 ms2 x Hz(-1). Differences were found in the lowest mean arterial pressure and heart rate after induction of anaesthesia. We conclude that the pre-operative total power of heart rate variability in high risk patients may indicate the occurrence of haemodynamic events with high sensitivity and specificity. Heart rate variability may be a suitable tool to identify patients at high risk of a haemodynamic event and may be used to indicate need for intensive monitoring and, perhaps, prophylactic treatment.