Items in AFP with MESH term: Water-Electrolyte Balance

Management of Hyponatremia - Article

ABSTRACT: Hyponatremia is an important electrolyte abnormality with the potential for significant morbidity and mortality. Common causes include medications and the syndrome of inappropriate antidiuretic hormone (SIADH) secretion. Hyponatremia can be classified according to the volume status of the patient as hypovolemic, hypervolemic, or euvolemic. Hypervolemic hyponatremia may be caused by congestive heart failure, liver cirrhosis, and renal disease. Differentiating between euvolemia and hypovolemia can be clinically difficult, but a useful investigative aid is measurement of plasma osmolality. Hyponatremia with a high plasma osmolality is caused by hyperglycemia, while a normal plasma osmolality indicates pseudohyponatremia or the post-transurethral prostatic resection syndrome. The urinary sodium concentration helps in diagnosing patients with low plasma osmolality. High urinary sodium concentration in the presence of low plasma osmolality can be caused by renal disorders, endocrine deficiencies, reset osmostat syndrome, SIADH, and medications. Low urinary sodium concentration is caused by severe burns, gastrointestinal losses, and acute water overload. Management includes instituting immediate treatment in patients with acute severe hyponatremia because of the risk of cerebral edema and hyponatremic encephalopathy. In patients with chronic hyponatremia, fluid restriction is the mainstay of treatment, with demeclocycline therapy reserved for use in persistent cases. Rapid correction should be avoided to reduce the risk of central pontine myelinolysis. Loop diuretics are useful in managing edematous hyponatremic states and chronic SIADH. In all instances, identifying the cause of hyponatremia remains an integral part of the treatment plan.


Perioperative Management of Diabetes - Article

ABSTRACT: Maintaining glycemic and metabolic control is difficult in diabetic patients who are undergoing surgery. The preoperative evaluation of all patients with diabetes should include careful screening for asymptomatic cardiac or renal disease. Frequent self-monitoring of glucose levels is important in the week before surgery so that insulin regimens can be adjusted as needed. Oral agents and long-acting insulin are usually discontinued before surgery, although the newer long-acting insulin analog glargine may be appropriately administered for basal insulin coverage throughout the surgical period. The usual regimen of sliding scale subcutaneous insulin for perioperative glycemic control may be a less preferable method because it can have unreliable absorption and lead to erratic blood glucose levels. Intravenous insulin infusion offers advantages because of the more predictable absorption rates and ability to rapidly titrate insulin delivery up or down to maintain proper glycemic control. Insulin is typically infused at 1 to 2 U per hour and adjusted according to the results of frequent blood glucose checks. A separate infusion of dextrose prevents hypoglycemia. Potassium is usually added to the dextrose infusion at 10 to 20 mEq per L in patients with normal renal function and normal preoperative serum potassium levels. Frequent monitoring of electrolytes and acid-base status is important during the perioperative period, especially in patients with type 1 diabetes because ketoacidosis can develop at modest levels of hyperglycemia.



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