Effects of Hyperglycemia During Cardiopulmonary Bypass on Renal Function

Significance:

Postoperative renal dysfunction is a common complication of cardiopulmonary bypass occurring in nearly 8% of all patients undergoing myocardial revascularization. Both diabetes and preoperative hyperglycemia are independent risk factors for postoperative renal dysfunction after coronary artery bypass surgery.

The cause of renal injury is multifactoral and in most cases involves renal ischemia from alteration of renal perfusion, resistance, metabolic byproducts (free-radical species), inflammatory mediators and embolic processes.

In the setting of ischemia, specifically, neuronal, hyperglycemia has been shown to worsen neurologic outcome and interfere with wound healing-possibly increasing the incidence of wound infection.

Hyperglycemia is common during cardiopulmonary bypass in both diabetic and non-diabetic patients as a result of altered glucose regulation during hypothermic conditions (body temperature actively cooled to 28 degree centigrade) and, more importantly, from delivery of cardioplegia to arrest the heart allowing for surgical repair in a non-beating heart. The cardioplegia is rich in potassium, among other agents, believed to offer cardioprotection during cardiopulmonary bypass and is prepared in Dextrose 5% and normal saline. On average, each patient receives nearly 2 liters of this solution, amounting to 100 grams or more of glucose. In this setting, hyperglycemia is also promoted from insulin suppression, stress hormone induced gluconeogenesis and enhanced tubular resorption.