Heart-Rate Variability and Its Role in Non-Cardiac Surgery Perioperative Care: Scoping Review.
BACKGROUND Heart rate variability (HRV) is a non-invasive method of assessing autonomic function. Those with autonomic dysfunction may be at heightened risk of peri-operative complications due to sympatho-parasympathetic imbalance. This review summarises the clinical applications of HRV, approaches to how it is measured, and its role in predicting peri-operative complications. METHOD A systematic search of EMBASE and MEDLINE databases was performed, with results screened independently by two reviewers. Primary studies exploring the use of HRV in the context of non-cardiac surgery were eligible. Outcomes of interest were technical parameters involved in assessing autonomic function and peri-operative complications. The data were systematically extracted, charted, and summarised using a narrative synthesis. Due to expected heterogeneity of results, quantitative analysis was not planned. RESULTS In total 1513 studies were screened and 63 were eligible for inclusion. Heart rate variability was used to measure autonomic function before surgery (n = 54/63; 85.7%), during surgery (n = 12/63; 19.0%), and after surgery (n = 18/63; 28.6%). HRV indices showed promise for identifying patients at risk of perioperative complications, most commonly comprising mortality, delirium, postoperative pain, myocardial ischaemia, and critical care admission. Measurements of HRV on post-operative day 1 tended to show superior discriminatory value than those performed later during recovery. CONCLUSION Multiple clinical applications of HRV exist in the peri-operative period. If demonstrated definitively, HRV in patients undergoing major non-cardiac surgery could identify those at increased risk of perioperative morbidity and mortality.