Plasma osmolality

Diabetes insipidus Urine volume and osmolality, plasma osmolality... 

Antidiuretic hormone Glucose/insulin Urine osmolality Plasma insulin, glucose concentration Urine sodium excretion... 

While some clinical and laboratory findings assist in the general diagnosis of ARF, others are used to differentiate between prerenal, intrinsic, and postrenal ARF. For example, patients with prerenal ARF typically demonstrate enhanced sodium reabsorption, which is reflected by a low urine sodium concentration and a low fractional excretion of sodium. Urine is typically more concentrated with prerenal ARF and there is a higher urine osmolality and urine plasma creatinine ratio compared to intrinsic and postrenal ARF. 

Fluid restriction is generally unnecessary as long as sodium intake is controlled. The thirst mechanism remains intact in CKD to maintain total body water and plasma osmolality near normal levels. Fluid intake should be maintained at the rate of urine output to replace urine losses, usually fixed at approximately 2 L/day as urine concentrating ability is lost. Significant increases in free water intake orally or intravenously can precipitate volume overload and hyponatremia. Patients with stage 5 CKD require renal replacement therapy to maintain normal volume status. Fluid intake is often limited in patients receiving hemodialysis to prevent fluid overload between dialysis sessions. 

ECF depletion tends to occur acutely. In this setting, rapid and aggressive fluid replacement is required to maintain adequate organ perfusion. Because ECF depletion is generally due to the loss of isotonic fluid (proportional losses of sodium and water), major disturbances of plasma osmolality... 

TBW depletion (often referred to as dehydration ) is typically a more gradual, chronic problem compared to ECF depletion. Because TBW depletion represents a loss of hypotonic fluid (proportionally more water is lost than sodium) from all body compartments, a primary disturbance of osmolality is usually seen. The signs and symptoms of TBW depletion include CNS disturbances (mental status changes, seizures, and coma), excessive thirst, dry mucous membranes, decreased skin turgor, elevated serum sodium, increased plasma osmolality, concentrated urine, and acute weight loss. Common causes of TBW depletion include insufficient oral intake, excessive insensible losses, diabetes insipidus, excessive osmotic diuresis, and impaired renal concentrating mechanisms. Long-term care residents are frequently admitted to the acute care hospital with TBW depletion secondary to lack of adequate oral intake, often with concurrent excessive insensible losses. 

In situ perfusion studies assess absorption as lumenal clearance or membrane permeability and provide for isolation of solute transport at the level of the intestinal tissue. Controlled input of drug concentration, perfusion pH, osmolality, composition, and flow rate combined with intestinal region selection allow for separation of aqueous resistance and water transport effects on solute tissue permeation. This system provides for solute sampling from GI lumenal and plasma (mesenteric and systemic) compartments. A sensitive assay can separate metabolic from transport contributions. 

Common laboratory tests are used to classify the cause of ARF. Functional ARF, which is not included in this table, would have laboratory values similar to those seen in prerenal azotemia. However, the urine osmolality-to-plasma osmolality ratios may not exceed 1.5, depending on the circulating levels of antidiuretic hormone. The laboratory results listed under acute intrinsic renal failure are those seen in acute tubular necrosis, the most common cause of acute intrinsic renal failure. 

Total plasma protein concentration was determined by the buiret method (16) after correction of plasma hemoglobin which was determined by the cyanmethemoglobin method (15). Plasma osmolality was measured by a Wescor model 5100 vapor pressure osmometer. 

Statistical Methods. Means of treatment groups for plasma retention of BSP, plasma osmolality, total plasma protein concentration and urine flow rates were compared by students t test for independent sample means (17). Plasma enzyme activity data were converted to a quantal form and analyzed by the Fischer Exact Probability Test (18). Values greater than 2 standard deviations (P < 0.05) from the control value were chosen to indicate a positive response in treated fish. 

The first modern hydrophilic nonspecific iodinated CA was diatrizoic acid, which, formulated as a sodium and/or meglumine salt, is still used. This agent was first synthesized in 1953 [1]. Osmolality for this compound, at concentrations compatible with imaging (ie. 300-370 mgl mL" ), is about 5-7 times that of plasma (1500-2100 mOsm kg H2O). Other HOCA such as iothalamate, metrizoate and ioxithalamate, were synthesized and marketed over the next few years. In an attempt to reduce the osmolality of the injected solution and thus reduce pain and haemodynamic disturbances, metrizamide, a compound resulting from the condensation of metrizoic acid and glucosamine, was synthesized. It was the first nonionic CA. 

In the 1990s, to achieve iso-osmolality with plasma, various teams synthesized nonionic dimers, which resulted in the marketing of iotrolan and iodixanol. However, these compounds suffer from high levels of viscosity (at 20 °C and 320 mgl mL h iodixanol = 25.4 mPa.s vs 15.7 mPa.s for the ionic dimer sodium/ meglumine ioxaglate). 

The fundamental treatment for DKA includes aggressive intravenous hydration and insulin therapy and maintenance of potassium and other electrolyte levels. Fluid and insulin therapy is based on the patient s individual needs and requires frequent reevaluation and modification. Close attention has to be given to hydration and renal status, the sodium and potassium levels, and the rate of correction of plasma glucose and plasma osmolality. Fluid therapy generally begins with normal saline. Regular human insulin should be used for intravenous therapy with a usual starting dose of about 0.1 IU/kg/h. 

Cerebral edema has been described during therapy of diabetic ketoacidosis with a large volume of fluid, resulting in rapid changes in plasma osmolality, mostly in young patients (SEDA-26, 462). However, in 10 adults with... 

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