الفهرس 
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Abstract
Cardiac surgery with cardiopulmonary bypass (CPB) is associated with the development of a systemic inflammatory response that can often lead to dysfunction of major organs. Cardiac surgery associated acute kidney injury is a serious complication, the etiology of renal injury is multi-factorial sympathetic over-activity in addition to nephrotoxic, renal ischemia/ reperfusion, inflammation, hemolysis, oxidative stress and cholesterol emboli contribute to the development and progression of AKI. Valvular cardiac surgery with extracorporeal circulation is a stressful procedure increasing sympathetic nervous system activity which could attenuate renal function due the interrelation of sympathetic nervous system, hemodynamics and renal function.
Dexmedetomidine, an alpha 2-adrenoceptor agonist, has been evaluated as an adjunct to anesthesia and for the delivery of sedation and perioperative hemodynamic stability. It provokes dose-dependent and centrally-mediated sympatholysis. It is clear that dexmedetomidine attenuates surgical stress-induced increases in circulating epinephrine and norepinephrine and maintain renal blood flow and glomerular filtration. Therefore, it can protect the kidney against the adrenergic-mediated vasoconstriction by activation of α-2c receptors in the wall of vascular smooth muscle.
Furosemide, a potent loop diuretic, is frequently used in different stages of acute kidney injury Furosemide inhibits sodium reabsorption in the thick ascending limp of the loop of Henle, thus inducing a reduction in tubular oxygen consumption and improving renal tolerance to hypoxia. An increased excretion of renal vasodilatory prostaglandin E has been reported after intravenous administration of furosemide.
Serum creatinine is the most common marker of kidney function used in clinical practice. Nonetheless, the limitations of using serum creatinine as a kidney function measure are well documented. In particular, the production of creatinine is highly affected by dietary intake and muscle mass, which itself varies by age, height, gender, and race/ethnicity.
Serum cystatin C is a novel marker of kidney function that has been suggested to be able to overcome some of the age and body size limitations of serum creatinine as a marker of kidney function. Cystatin C has been proved to be a more sensitive and specific marker of kidney function in both children and adults.
The aim of this study is to compare dexmedetomidine with furosemide infusions as renal protection in valvular cardiac surgery with extracorporeal circulation, using cystatin C as an early predictor of acute kidney injury.
This prospective double-blinded study was conducted at El Minia university hospital from June 2015 to December 2016. Patients were assigned by pre-randomized, sealed envelopes to one of the study three groups; the study involved 90 patients who underwent elective valvular heart surgery using cardiopulmonary bypass at cardiothoracic hospital El Minia University.