Disturbed RAAS response to cardiac surgery in heart failure patients

Introduction: 

Heart failure (HF) patients are prone to postoperative hemodynamic instability after cardiac surgery, possibly due to upregulated renin-angiotensin-aldosterone system (RAAS) activity. We evaluated perioperative RAAS activity in control and HF patients and its impact on acute kidney injury (AKI) incidence. 

Materials and Methods: 

Pre-specified analysis of a prospective observational cohort study (VASOR). Plasma renin, angiotensinogen and aldosterone were measured perioperatively in 18 control and 18 HF patients. 

Results: 

RAAS blocker use was identical in both groups. HF patients displayed a diminished preoperative renal function. AKI occurred in 1 control and 8 HF patients. Preoperatively, HF patients exhibited 5-fold higher renin and aldosterone levels, identical aldosterone/renin ratios, and modestly lower angiotensinogen levels than controls. During surgery, renin rose 10-fold higher in HF patients. Aldosterone increased proportionally, but was blunted when normalized for renin (aldosterone/renin ratio). This was not due to angiotensinogen depletion. Postoperatively, angiotensinogen increased 50% in both groups, allowing aldosterone to increase, despite a modest postoperative renin decline. Preoperative renin levels and the surgery-induced renin rise predicted postoperative AKI. 

Conclusions: 

HF patients exhibit dysregulated RAAS responses to surgery may reflect impaired angiotensin I-angiotensin II conversion. Elevated renin signals RAAS dysregulation, identifying patients who might benefit from angiotensin II infusion. The Netherlands Trial Register (NTR5647); http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=5647.