Baroreflex impairment and morbidity after major surgery.

BACKGROUND: Baroreflex dysfunction is a common feature of established cardiometabolic diseases that are most frequently associated with the development of critical illness. Laboratory models show that baroreflex dysfunction impairs cardiac contractility and cardiovascular performance, thereby increasing the risk of morbidity after trauma and sepsis. We hypothesized that baroreflex dysfunction contributes to excess postoperative morbidity after major surgery as a consequence of the inability to achieve adequate perioperative tissue oxygen delivery.

METHODS: In a randomized controlled trial of goal-directed haemodynamic therapy (GDT) in higher-risk surgical patients, baroreflex function was assessed using the spontaneous baroreflex sensitivity (BRS) method via an arterial line placed before surgery, using a validated sequence method technique (one beat lag). The BRS was calculated during the 6 h postoperative GDT intervention. Analyses of BRS were done by investigators blinded to clinical outcomes. The primary outcome was the association between postoperative baroreflex dysfunction (BRS <6 mm Hg s(-1), a negative prognostic threshold in cardiovascular pathology) and early postoperative morbidity. The relationship between baroreflex dysfunction and postoperative attainment of preoperative indexed oxygen delivery was also assessed.

RESULTS: Patients with postoperative baroreflex dysfunction were more likely to sustain infectious {relative risk (RR) 1.75 [95% confidence interval (CI): 1.07-2.85], P=0.02} and cardiovascular morbidity [RR 2.39 (95% CI: 1.22-4.71), P=0.008]. Prolonged hospital stay was more likely in patients with baroreflex dysfunction [unadjusted hazard ratio 1.62 (95% CI: 1.14-2.32), log-rank P=0.004]. Postoperative O2 delivery was 36% (95% CI: 7-65) lower in patients with baroreflex dysfunction in those not randomly assigned to GDT (P=0.02).

CONCLUSIONS: Baroreflex dysfunction is associated with excess morbidity, impaired cardiovascular performance, and delayed hospital discharge, suggesting a mechanistic role for autonomic dysfunction in determining perioperative outcome.

CLINICAL TRIAL REGISTRATION: ISCRTN76894700.