Prevention of Acute Kidney Injury in Cardiac Surgery Patients

Acute kidney injury (AKI) has no uniform criteria, but is commonly defined as an increase in serum creatinine concentration by at least 25% from baseline. It occurs in 30% of patients following cardiac surgery, and at least 50% of patients with underlying renal insufficiency. Patients who have a reduced creatinine clearance pre-operatively are at the greatest risk of developing post-operative AKI. The purpose of the current study is to determine if intravenous hydration with either isotonic saline or sodium bicarbonate 150 mEq/L is effective at preventing post-operative AKI in patients with baseline kidney insufficiency and who are undergoing cardiac surgery using cardiopulmonary bypass. The study hypothesis is that an infusion of sodium bicarbonate 150 mEq/L will be more effective than isotonic saline in reducing the incidence of post-operative AKI in cardiac surgery patients with a preoperative glomerular filtration rate (GFR) less than 60 ml/min/1.73m2.

This is a randomized, placebo-controlled, prospective, double-blinded. The study will take place at Community Medical Center in Scranton, Pennsylvania. The inclusion criteria are patients undergoing elective, urgent, or emergent cardiac surgery using cardiopulmonary bypass and having a baseline GFR less than 60 ml/min/1.73m2 estimated using the Modification of Diet in Renal Disease equation. Patients will be excluded from the study if they have cardiogenic shock (defined as a cardiac index less 2 L/min/m2 despite high dose inotropes or the need for intra-aortic balloon pump), end-stage kidney disease requiring dialysis, received an infusion of sodium bicarbonate on the same day as cardiac surgery, or if they are enrolled in a separate clinical research trial. This trial will involve two treatment groups. Group one will receive isotonic saline at 3 ml/kg/hr for one hour pre-operatively until the patient is started on cardiopulmonary bypass. Then the infusion will be reduced to 1 ml/kg/hr throughout cardiopulmonary bypass and for six hours following cardiopulmonary bypass. Group two will receive sodium bicarbonate 150mEq in 850ml of a 5% dextrose solution using the same infusion regimen as described above for isotonic saline. The primary efficacy outcome of the study will be the incidence of AKI postoperatively. Acute kidney injury will be defined as an increase in serum creatinine concentration by at least 25% from baseline or an absolute increase of 0.5 mg/dL at any time within the first five postoperative days.

This group will receive isotonic saline at 3 ml/kg/hr for one hour pre-operatively until the patient is started on cardiopulmonary bypass. Then the infusion will be reduced to 1 ml/kg/hr throughout cardiopulmonary bypass and for six hours following cardiopulmonary bypass.

This arm two will receive sodium bicarbonate 150mEq in 850ml of a 5% dextrose solution at 3 ml/kg/hr for one hour pre-operatively until the patient is started on cardiopulmonary bypass. Then the infusion will be reduced to 1 ml/kg/hr throughout cardiopulmonary bypass and for six hours following cardiopulmonary bypass.

0.9% Sodium Chloride (placebo) will infuse at 3 ml/kg/hr for one hour pre-operatively until the patient is started on cardiopulmonary bypass. Then the infusion will be reduced to 1 ml/kg/hr throughout cardiopulmonary bypass and for six hours following cardiopulmonary bypass.

Group two will receive sodium bicarbonate 150mEq in 850ml of a 5% dextrose solution at 3 ml/kg/hr for one hour pre-operatively until the patient is started on cardiopulmonary bypass. Then the infusion will be reduced to 1 ml/kg/hr throughout cardiopulmonary bypass and for six hours following cardiopulmonary bypass.

Inclusion Criteria: elective, urgent, or emergent cardiac surgery using cardiopulmonary bypass baseline GFR less than 60 ml/min/1.73m2 estimated using the Modification of Diet in Renal Disease equation Exclusion Criteria: cardiogenic shock (defined as a cardiac index less 2 L/min/m2 despite high dose inotropes or the need for intra-aortic balloon pump) end-stage kidney disease requiring dialysis received an infusion of sodium bicarbonate on the same day as cardiac surgery

Kristeller JL, Zavorsky GS, Prior JE, Keating DA, Brady MA, Romaldini TA, Hickman TL, Stahl RF. Lack of effectiveness of sodium bicarbonate in preventing kidney injury in patients undergoing cardiac surgery: a randomized controlled trial. Pharmacotherapy. 2013 Jul;33(7):710-7. doi: 10.1002/phar.1262. Epub 2013 Apr 1.