Essential L-amino acids for hyperalimentation in patients with disordered nitrogen metabolism

Acute Renal Failure in Critically Ill Patients

Acute renal failure is an important cause of morbidity in critically ill patients. Acute renal failure results from pre renal and postrenal causes and, most importantly, acute tubular necrosis (ATN). Although it is known that renal toxins and renal ischemia are the most common causes of ATN in hospitalized patients, the exact pathogenesis of this entity is still not fully understood. Patients in the intensive care unit are at high risk for ATN because of hemodynamic instability, the administration of neph rotoxic antibiotics or chemotherapeutic agents, and ex posure to radiographic contrast agents. The acquired immunodeficiency syndrome is also associated with an increased risk of renal failure development, either from complications of the disease itself or from its treatment. Many consequences of acute renal failure such as vol ume overload, acidosis, hyperkalemia, and serositis can be managed adequately with peritoneal dialysis, hemo dialysis, or a newer technique, continuous arteriove nous hemofiltration. Despite improvements in treat ment, however, the mortality of ATN remains high. In this review, we recommend measures to prevent ATN in certain clinical situations that commonly occur among critically ill patients. We also review therapeutic options for treating patients in whom acute renal failure devel ops and discuss newer developments that may begin to reduce the excessive morbidity associated with ATN.

Recovery from ischemic acute renal failure is improved with enteral compared with parenteral nutrition

OBJECTIVE

To compare measurements of renal function after acute ischemic renal failure in rats fed enterally or parenterally.

DESIGN

Prospective, randomized, animal trial.

SETTING

University research laboratory.

SUBJECTS

Male Sprague-Dawley rats (n = 21).

INTERVENTIONS

Animals were randomized to receive isocaloric (160 nonprotein kcal/kg/day), or isonitrogenous (1.4 g of nitrogen/kg/day [100 mmol/kg/day]) enteral (n = 10), or parenteral nutrition (n = 11) through either a gastrostomy tube or a catheter placed in the jugular vein. After the animals received 7 days of assigned feedings, baseline blood samples were collected. A right nephrectomy and 45-min left renal pedicle occlusion were then performed. One hour after the ischemic injury, assigned feedings were resumed and continued for 3 days. After ischemic injury, daily blood samples were obtained and 24-hr urine collections were performed. On day 11, animals were killed and the kidney was harvested and fixed for subsequent microscopic examination.

MEASUREMENTS AND MAIN RESULTS

Urine was analyzed for concentrations of total urea nitrogen, creatinine, protein, and calcium. Serum was analyzed for creatinine and urea nitrogen concentrations. Fixed kidney sections were examined for mitotic figures, tubular calcifications, and casts using light microscopy by an investigator blinded to the nutritional regimen. Data are presented as mean +/- SD or median (range). Percent increase in creatinine clearance from the nadir on day 9 to day 11 was approximately 2.5-fold greater in the enteral compared with the parenteral nutrition group (490 +/- 221% vs. 208 +/- 130%; p = .003). Histologic evaluation demonstrated greater dystrophic tubular calcifications per ten high-power fields in the parenteral compared with the enteral nutrition group (50 [four to 85] vs. three [0 to 37]; p = .001). No differences in urine calcium concentration or 24-hr calcium excretion were seen.

CONCLUSION

Rats given continuous enteral nutrition 7 days before and for 3 days after ischemic acute renal failure have improved renal function compared with rats given parenteral nutrition.

Pathogenesis and treatment of acute renal failure

This article reviews the current understanding of the pathophysiologic sequence of events that culminate in an acute renal insult. The use of urinary indices to differentiate the physiologic causes of oliguria, namely, diminished intravascular volume or renal perfusion, from an established acute renal failure, is discussed for children and adolescents, as well as for neonates. Treatment modalities for the support of children with acute renal failure are described in detail.

Postoperative total parenteral nutrition in patients with liver disorders

Sixty-one patients with liver disorders receiving total parenteral nutrition (TPN) for about 14 postoperative days were divided into three groups based on the parenteral nutritional regimen. The influence of these TPN solutions on the liver function tests and the nutritional assessments, and the availability of the specially formulated amino acid solution were studied. Glucose alone as energy source was infused in Group Ia. The mixture of glucose and fructose was infused in Group Ib. In these patients (Group I), a commercially available amino acid solution was administered simultaneously. A specially formulated amino acid, rich in branched-chain amino acids but poor in aromatic amino acids was infused with the mixture of glucose and fructose in Group II. There was no remarkable elevation of blood glucose and lactate levels in all patients. Blood glucose levels in Group Ib were maintained lower than that in Group Ia. Except for serum alkaline phosphatase, no remarkable abnormality was observed in liver function tests. Body weight changes were less than 5% in each group. Average nitrogen balances were -44.5 mg/kg/day in Group Ia, -5.5 mg/kg/day in Group Ib, -51.5 mg/kg/day in Group II. While the abnormalities in serum amino acid pattern and molar ratio of leucine, isoleucine, and valine to phenylalanine and tyrosine tend to be more enhanced in Group I, these abnormalities returned to near normal in Group II during TPN. By multiple linear regression analyses, 45 kcal/kg/day of energy intake would be required to maintain nitrogen equilibrium and zero body weight change. And when nitrogen intakes were 159 mg/kg/day in Group Ia, 114 mg/kg/day in Group Ib, and 189 mg/kg/day in Group II at 45 kcal/kg/day in energy intake, nitrogen balances were expected to be equivalent. These results suggest that postoperative TPN is good for nutritional support in patients with liver disorders. And also, the combination of glucose and fructose has better effect on nitrogen balance. The postoperative TPN with a specially formulated amino acid solution may be a valuable way of maintaining the nutritional status as well as normal serum amino acid pattern in patients with liver disorders.

Nutritional support in the patient with acute renal failure

Nutritional support in the patient with acute renal failure is of great importance in lessening the degree of catabolism when energy demands are high and may also result in salutary metabolic effects. Overall treatment considerations in the posttraumatic or postsurgical patient with acute renal failure will be discussed, including fluid and electrolyte balance and energy and nutritional considerations. The application of the Giordano and Giovannetti principles to the field of parenteral nutritional support enables modifications of treatment programs of total parenteral nutrition to be applied to patients with acute renal failure. Utilizing an intravenous mixture of eight essential l-amino acids, hypertonic dextrose, and vitamins, we observed salutary biochemical effects in surgical patients. A prospective, randomized double-blind study of that treatment regimen compared to patients receiving hypertonic dextrose and vitamins alone resulted in improved survival and a decreased duration of renal failure in the treated group. Management considerations of these patients and possible application of these principles to other patients in renal failure will be discussed.

Meeting exceptional nutritional needs. 2. Elemental enteral alimentation

Elemental enteral alimentation (EEA) is an alternative to parenteral nutrition in patients with a functioning gastrointestinal tract and increased caloric requirements or in whom regular oral feeding is impossible or impractical. EEA is given by nasogastric, jejunostomy, or gastrostomy tube. It is useful in cases of short-gut syndrome, pancreatic disease, partial intestinal obstruction, colitis, neuropsychiatric cachexia, trauma, fistula, vascular insult, and renal and liver disease, as well as in patients being prepared for surgery or requiring hyperalimentation after surgery or abdominal irradiation. Strict attention must be paid to fluid and electrolyte status and to blood and urine glucose levels in patients receiving EEA. With use of a nasogastric tube, infection of the middle ear is a possible but uncommon complication.