Enteral Feeding Improves Outcome and Protects against Glycerol-induced Acute Renal Failure in the Rat

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Abstract
Acute renal failure is a common cause of morbidity and mortality in critically ill patients and frequently results from vasoconstrictive ischemic injury to the kidney. Protein and amino acids can vasodilate renal blood vessels. Thus, we tested the hypothesis that enteral feeding could prevent renal ischemic injury using an experimental model in which renal vasoconstriction is believed to cause ischemic renal injury. This study was performed using male Sprague-Dawley rats, and renal injury was induced by glycerol injection into the hind limbs. The resulting muscle necrosis (rhabdomyolysis) causes acute renal injury. In the first part of the study, 35 animals were randomized to a peptide-based enteral diet or water via a duodenal feeding tube and subsequently injected with glycerol. Seventy-eight percent (14 of 18) of the animals receiving the enteral diet survived 3 d compared with 35% (six of 17) of the water-fed animals (p < 0.05). Blood urea nitrogen (47+/-8 versus 137+/-27 mg/dl) and creatinine (0.8+/-0.1 versus 2.0+/-0.3 mg/dl) were significantly lower in the enteral survivors than in the water survivors. In the second part of the study, renal plasma flow (para-aminohippurate clearance) and glomerular filtration rate (insulin clearance) were measured in similarly treated animals (n = 14) 1 d after injury. Renal plasma flow (4.83+/-0.65 versus 2.37+/-0.62 ml/min) and glomerular filtration rate (2.05+/-0.27 versus 0.89+/-0.22 ml/min) were significantly higher in the enteral group than in the water group. These data indicate that enteral feeding can prolong survival and decrease renal injury after glycerol-induced rhabdomyolysis. The mechanism for the protection is partly related to maintenance of renal blood flow.