The RAS, Fibrinolysis and Cardiopulmonary Bypass

Summary

Each year over a million patients worldwide undergo cardiac surgery requiring cardiopulmonary bypass (CPB).1 CPB is associated with significant morbidity including hemodynamic instability, the transfusion of allogenic blood products, and inflammation. Blood product transfusion increases mortality after cardiac surgery. Enhanced fibrinolysis contributes to increased blood product transfusion requirements in the perioperative period. CPB activates the kallikrein-kinin system (KKS), leading to increased bradykinin concentrations. Bradykinin, acting through its B2 receptor, stimulates the release of nitric oxide, inflammatory cytokines and tissue-type plasminogen activator (t-PA). Based on data indicating that angiotensin-converting enzyme (ACE) inhibitors reduce mortality in patients with coronary artery disease, many patients undergoing CPB are taking ACE inhibitors. While interruption of the renin-angiotensin system (RAS) reduces inflammation in response to CPB, ACE inhibitors also potentiate the effects of bradykinin and may augment B2-mediated change in fibrinolytic balance and inflammation. In contrast, angiotensin II type 1 receptor antagonism does not potentiate bradykinin and does not inhibit bradykinin metabolism.

Studies in animals suggest that bradykinin receptor antagonism inhibits reperfusion-induced increases in vascular permeability and neutrophil recruitment.A randomized, placebo controlled clinical trial of a bradykinin B2 receptor antagonist demonstrated some effect on survival in patients with systemic inflammatory response syndrome and gram-negative sepsis. In addition, we and others have shown bradykinin B2 receptor antagonism reduces vascular t-PA release during ACE inhibition. The current proposal derives from data from our laboratory and others elucidating the role of the KKS in the inflammatory, hypotensive and fibrinolytic response to CPB. Specifically, we have found that CPB activates the KKS and that ACE inhibition and smoking further increases bradykinin concentrations. During CPB, bradykinin concentrations correlate inversely with mean arterial pressure and directly with t-PA. Moreover, we have found that bradykinin receptor antagonism attenuates protamine-related hypotension following CPB. The current proposal tests the central hypothesis that the fibrinolytic and inflammatory response to cardiopulmonary bypass differ during angiotensin-converting enzyme inhibition and angiotensin II type 1 receptor antagonism.

Conditions

• Coronary Artery Disease
• Angiotensin Converting Enzyme
• Angiotensin Receptor Blockers
• Cardiopulmonary Bypass
• Fibrinolysis
• Inflammation

Interventions

DRUG

Placebo

Placebo

DRUG

Ramipril

Ramipril 2.5mg day 1 and 2 and then 5mg/d thereafter

DRUG

Candesartan

Candesartan 16mg/d

Sponsors & Collaborators

• Vanderbilt University

  lead OTHER

Principal Investigators

• Mias Pretorius, MBChB, MSc · Vanderbilt University

Study Design

Allocation

RANDOMIZED

Purpose

TREATMENT

Masking

QUADRUPLE

Model

PARALLEL

Eligibility

Min Age

18 Years

Max Age

80 Years

Sex

ALL

Healthy Volunteers

No

Timeline & Regulatory

Start

2006-08-31

Primary Completion

2011-08-31

Completion

2011-12-31

Countries

• United States

Study Locations