Effect of perioperative autonomic nervous system imbalance on surgical outcomes: a systematic review

The autonomic nervous system (ANS) is essential for maintaining physiological homeostasis. Autonomic nervous system imbalance, characterised by sympathetic hyperactivation and low parasympathetic tone, can occur during the perioperative period. These changes drive systemic stress responses, cardiovascular instability, impaired tissue repair, and immunosuppression, which in turn increase infection risk, neurocognitive decline, and multiorgan dysfunction. Surgical trauma, anaesthesia, pain, hypothermia, and psychological stressors all contribute to this dysregulation, and consequently low parasympathetic tone results in the cholinergic anti-inflammatory pathway being less effective. High sympathetic nervous system activity promotes catecholamine surges and pro-inflammatory cytokine release. Pharmacological interventions, including dexmedetomidine and β-blockers, together with nonpharmacological strategies, such as electroacupuncture and temperature management, are measures that have potential to restore ANS balance. This systematic review covers ANS-mediated organ regulation, pathophysiological consequences of perioperative dysautonomia, and evidence-based therapeutic strategies. By integrating findings from multiple basic and clinical studies, the pivotal roles of ANS modulation in mitigating postoperative complications, including neurocognitive disorders, immunosuppression, and cancer recurrence, are discussed. Maintaining balance of the sympathetic and parasympathetic nervous systems is an important prospect in perioperative medicine that could benefit surgical patients' short- or long-term recovery.