Relationship between heart rate variability and hypotension with bradyacardia following spinal anaesthesia in patients undergoing elective surgery

Abstract

Background: Hypotension is a common complication of spinal anaesthesia and occurs due to the sympatholytic effect of local anaesthesia on the cardiovascular system and consequence effects on the autonomic nervous system. Heart rate variability (HRV) is currently a well-known predictive tool for hypotension and the commonly associated bradycardia.

Objective: To evaluate the relationship between preoperative measured HRV and hypotension with bradycardia among patients undergoing elective surgeries under spinal anaesthesia.

Method: Eighty-four patients aged between 18 and 65 years were recruited. HRV measurements were taken immediately after electrocardiographic (ECG) tracing according to the North American Society for Pacing and Electrophysiology (NASPE). Pre and intraoperative heart rate (HR), systolic and diastolic blood pressure and mean arterial blood pressure were monitored and recorded every 5 minutes from induction of spinal anaesthesia till the end of surgery. Multivariate analysis was used to determine the association between development of hypotension, bradycardia and age, systolic and diastolic blood pressure and Heart Rate Variability in the low frequency (LF) and high Frequency (HF) domains.

Results: Hypotension occurred in 55 patients (65.5%). Age (p= 0.015), base line systolic blood pressure (p=0.003) and base line diastolic pressure (p=0.027) were significantly associated with the development of hypotension. Low frequency (LF) was significantly associated with the development of hypotension, while high frequency (HF) was significantly associated with bradycardia.

Conclusion: Heart rate variability was useful in predicting development of hypotension and bradycardia in patient undergoing elective surgery under spinal anaesthesia.