Diuresis, osmotic

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. 

The answer is b. (Hardman, pp 695-697.) A significant increase in the amount of any osmotically active solute in voided urine is usually accompanied by an increase in urine volume Osmotic diuretics affect diuresis through this principle. The osmotic diuretics (such as mannitol) are nonelectrolytes that are freely filtered at the glomerulus, undergo limited re absorption by the renal tubules, retain water in the renal tubule, and promote an osmotic diuresis, generally without significant Na excretion. Ln addition, these diuretics resist alteration by metabolic processes. 

Ad. 3. Manipulation of intra-f extra-cellular ration. Le Rumear et al24 manipulated intra-/extra-cellular ratios and showed that an increase in vascular volume induced by nerve stimulation increased the fraction of the slow relaxation component, while reduced intra-cellular/interstitial volume induced by osmotic diuresis decreased the fraction of the fast relaxing component and increased the fraction of the slow relaxing component, which indicates that the fast and slow relaxing component can be ascribed to the intra- and extra-cellular space, respectively. 

Polyuria, dehydration, and thirst (exacerbated by hyperglycemia and osmotic diuresis)... 

Drugs and poisons can in principle be removed from the systemic circulation by forced osmotic diuresis. These are theoretical concepts used in the... 

The dianhydro-D-glucitol lessens cerebrospinal fluid pressure and brain mass when administered orally to dogs 117 this effect is accompanied by osmotic diuresis. Intravenous injection likewise produces a drop in the cerebrospinal fluid pressure, but this is followed by a greater rebound. ... 

Pretreatment with intravenous hydration without glucose to avoid osmotic diuresis... 

Water Deficiency. This condition occurs when water output exceeds intake. Water is continually losl by way of the lungs, skin, and kidneys and dius a deficiency of body water will occur if a critical minimal supply is not maintained. Decreased intake when water is available is uncommon. Very rarely, a brain malfunction may interfere with one s sense of diirst. Increased output of water can result from many causes. For example, a person with diabetes insipidus who lacks ADH (antidiuretic hormone) or a person whose kidneys do not respond normally to ADH, as in instances of nephrogenic diabetes insipidus, will increase water output Other diseases which may cause excess excretion of water include osmotic diuresis, hypercalcemia, hypokalemia, chronic pyelonephritis, and sickle cell anemia, among others. Excessive water losses are also experienced in some cases with advanced age and in some burn cases. Two clinical features are good measures of dehydration—weight loss of the patient and an elevation of the serum sodium concentration. In situations of dehydration, the body initiates mechanisms which manipulate the transfer of water from one compartment to the next, retaining water in those cells and organs where it is most needed. 

Wesson LG, Anslow WP (1952) Effect of osmotic diuresis and mercurial diuresis in simultaneous water diuresis. Am J Physiol 170 255-259... 

These include mannitol and sorbitol which act mainly in the proximal tubules to prevent reabsorption of water. These polyhydric alcohols cannot be absorbed and therefore bind a corresponding volume of water. Since body cells lack transport mechanisms for these substances (structure on p.175), they also cannot be absorbed through the intestinal epithelium and thus need to be given by intravenous infusion. The result of osmotic diuresis is a large volume of dilute urine, as in decompensated diabetes melli-tus. Osmotic diuretics are indicated in the prophylaxis of renal hypovolemic failure, the mobilization of brain edema, and the treatment of acute glaucoma attacks (p. 346). 

Cirrhosis Hyperglycaem i a Portosystemic shunting of insulin and decreased hepatic insulin breakdown leads to inhibition of muscle glucose utilisation and peripheral insulin resistance, leading to elevated glucose levels Hyperglycaemia, acidosis, osmotic diuresis... 

Other metabolic effects. In addition to enabling glucose to pass across cell membranes, the transit of amino acids and potassium into the cell is enhanced. Insulin regulates carbohydrate utilisation and energy production. It enhances protein synthesis. It inhibits breakdown of fats (lipolysis). An insulin-deficient diabehc (Type 1) becomes dehydrated due to osmotic diuresis, and is ketotic because fats break down faster than the ketoacid metabolites can be metabolised. 

In cases of inadequate response to diuretic therapy (stage II), osmotic diuresis (stage III) may be advisable in order to improve hypoalbuminaemia and hypovolaemia. (s. fig. 16.16)... 

Mannitol Stimulation of osmotic diuresis is possible using mannitol (10-20% solution). (128) Mannitol is neither metabolized in the body nor reabsorbed by the tubules and is excreted almost totally through the kidney. Renal circulation and renal filtration are raised, and by reducing tubular absorption (= osmotic diuresis), water excretion is increased ( diuresis starter ). The saluretic effect is, however, relatively small. In the case of restricted renal function, application of mannitol is contraindicated. If necessary, the mannitol test (i.v. injection of 75 ml of a 20% solution) can be carried out beforehand. With enhanced diuresis of > 40 ml/hr, the kidneys still function adequately, so that it is possible to stimulate osmotic diuresis by means of a mannitol infusion. 

Well-controlled studies on aminocaproic acid in a limited number of patients showed no serious adverse effects. Minor unwanted effects have been reported in 10-20% of patients and include headache, nasal congestion, conjunctival suffusion, nausea, vomiting, diarrhea, and transient hjrpotension (32). Skin rashes have also been associated with aminocaproic acid, including maculopapular and morbilliform eruptions. Rarer dermatological reactions reported include purpuric rashes (33), bullous eruptions (34), and contact dermatitis with positive patch tests (35-37). Treatment with a high dose (the maximum daily dose is 36 g/day) can result in an osmotic diuresis (38). 

Lee P, Pompeius R. Antifibrinolytisk behandhng och for-cerad osmotisk diures efter transuretral prostataresektion. [Antifibrinolytic treatment and forced osmotic diuresis after transurethral prostatectomy.] Nord Med 1970 84(51) 1624-6. 

Dalgard OZ, Pederson KJ. Some observations of the fine structure of human kidneys in acute anuria and osmotic diuresis. In Renal Biopsy. Wolstenholme GEW, Cameron MP (editors). Little Brown, New York, 1962 ... 

Leyssac PP, Holstein-Rathlou NH,Skott P,Alfrey AC. A micropuncture study of proximal tubulartransport of lithium during osmotic diuresis. Am J Physiol 1990 258 F1090-F1095. 

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