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[Pitfalls in the interpretation of laboratory parameters-electrolytes, urea, creatinine].
Risch, L, Hess, B
Therapeutische Umschau. Revue therapeutique. 2013;(8):457-64
Abstract
When it comes to interpret parameters of electrolyte balance and kidney function, it is important to keep pathophysiology and the theory on reference intervals in mind. Hyponatremia is most often caused by excess water. A low sodium concentration in urine should prompt a clinical evaluation of volume status. In case of suspected acute kidney failure, fractionated sodium excretion and fractionated urea excretion are able to provide insights on prerenal or renal origin of the disorder. Disruption in potassium homoeostasis can occur due to changes in supply or renal elimination as well as due to changes in the potassium balance between the extra- and intracellular compartments. The transtubular potassium gradient can help in the differential diagnosis of hyperkalemia. Evaluation of kidney function should begin with determination of serum creatinine, accompanied by an estimate of the glomerular filtration rate, as calculated by the CKD-EPI equation. As a consequence of non-renal determinants of serum creatinine, this equation has been shown to overestimate true GFR in elderly and hospitalized patients. This can result in overdosing of renally-cleared drugs. Clearance determinations can be of use in this context.
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2.
Considerations in the difficult-to-manage urea cycle disorder patient.
Lee, B, Singh, RH, Rhead, WJ, Sniderman King, L, Smith, W, Summar, ML
Critical care clinics. 2005;(4 Suppl):S19-25
Abstract
Today, patients with urea cycle disorder (UCD) may survive well beyond infancy. The goal of keeping them in consistent nitrogen balance can be undermined by changing metabolic needs throughout various stages of life, resulting in hyperammonemia in the short term, and poor growth and development in the long term. The specific UCD genotype can affect the risk of metabolic destabilization and management difficulties, as can variable protein tolerance secondary to changing growth demands, biochemical complications, and environmental influences. Preventing catabolic stress is as important as controlling dietary protein intake for avoiding metabolic decompensation. Optimal treatment, specifically pharmacologic therapy, possible branched chain amino acid (BCAA) supplementation, accurate laboratory monitoring, and psychosocial support, requires thorough understanding and careful application of each component.
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3.
Nutritional management of urea cycle disorders.
Singh, RH, Rhead, WJ, Smith, W, Lee, B, Sniderman King, L, Summar, M
Critical care clinics. 2005;(4 Suppl):S27-35
Abstract
Nutritional management of patients who have urea cycle disorders is one of the most challenging tasks in clinical nutrition. The degree to which protein intake should be restricted in urea cycle disorders requires complex calculations which depend on many variables such as specific enzyme defect, age-related growth rate, current health status, level of physical activity, amount of free amino acids administered, energy intake, residual urea cycle function, family lifestyle, use of nitrogen-scavenging medications, and the patient's eating behaviors. This paper presents two case histories and a series of recommendations outlining the nutrition management of urea cycle disorders. It also identifies difficulties that arise in the course of treatment, and suggests practical solutions for overcoming them.
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4.
Genetic counseling issues in urea cycle disorders.
Sniderman King, L, Singh, RH, Rhead, WJ, Smith, W, Lee, B, Summar, ML
Critical care clinics. 2005;(4 Suppl):S37-44
Abstract
The goal of counseling families that have a urea cycle disorder (UCD) is to facilitate the process of scientific understanding, emotional acceptance, and decision-making in a nondirective way. A proper understanding of the genes involved, inheritance patterns, available testing, and complicating factors is critical to serving the families' needs. This article summarizes the needed information, in particular describing the complexities of prenatal testing and counseling issues for each UCD. Included case histories illustrate the genetic counseling process and the decision-making scenarios for two families.
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5.
Urea cycle disorders: clinical presentation outside the newborn period.
Smith, W, Kishnani, PS, Lee, B, Singh, RH, Rhead, WJ, Sniderman King, L, Smith, M, Summar, M
Critical care clinics. 2005;(4 Suppl):S9-17
Abstract
Although most commonly associated with infancy, the majority of individuals with urea cycle disorders (UCDs) present outside the neonatal period, frequently in childhood. Signs and symptoms are often vague, but recurrent; fulminant presentations associated with acute illness are also common. A disorder of urea cycle metabolism should be considered in children who have recurrent symptoms, especially neurologic abnormalities associated with periods of decompensation. Routine laboratory tests, including measurement of plasma ammonia concentrations, can indicate a potential UCD; however, specific metabolic testing and ultimately enzymatic or molecular confirmation are necessary to establish a diagnosis. Treatment with dietary protein restriction and medications may be challenging in children.