Dehydration, hypernatremia caused

Hypernatremia occurs in water deficiency, caused by reduced water supply or elevated water loss, corresponding to hypertonic dehydration. Hypernatremia caused by excessive intake of sodium or reduced elimination of sodium results in hypertonic hyperhydration. Elevated serum sodium may also occur in endocrine dysregulations (e.g., hyperaldosteronism. Conn s syndrome, Cushing s syndrome) and in chronic kidney disease. 

Acid-base and electrolyte balance High therapeutic dose especially when used in rheumatic fever, stimulates respiration and causes respiratory alkalosis. Reduction in bicarbonate and potassium level reduces the buffering capacity of the extracellular and intracellular fluid. Hypokalemia may lead to dehydration and hypernatremia. They also interfere with carbohydrate metabolism resulting in accumulation of pyruvic acid and lactic acid. 

Hypernatremia (plasma Na >150 mmol/L) is always hyperosmolar, Symptoms of hypernatremia are primarily neurological (because of intraneuronal loss of H2O to the ECF) and include tremors, irritability, ataxia, confusion, and coma. As with hyponatremia, the rapidity of the development of hypernatremia wiU determine the plasma Na value at which symptoms occur. Acute development may cause symptoms when Na reaches 160 mmol/L, although in chronic hypernatremia, overt symptoms may not occur until Na exceeds 175 mmol/L. In chronic hypernatremia, the intracellular osmolality of CNS cells wiU increase to protect against intracellular dehydration. Because of this, rapid correction of hypernatremia can cause dangerous cerebral edema, as CNS cells will take up too much water if the ICF is hyperosmotic when normonatremia is achieved. ... 

Hypernatremia in the setting of decreased ECF is caused by the renal or extrarenal loss of hypoosmotic fluid leading to dehydration. Thus once hypovolemia is established, measurement of urine Na" " and osmolality is used to determine the source of fluid loss. Patients who have large extrarenal losses have a concentrated urine (>800 mOsmol/L) with low urine Na (<20 mmol/L), reflecting the proper renal response to conserve Na and water as a means to restore ECF volume. Extrarenal causes include diarrhea, skin (burns or excessive sweating), or respiratory losses coupled with failure to replace the lost water. When gastrointestinal loss is excluded, and the patient has normal mental status and access to H2O, a hypothalamic disorder (tumor or granuloma) should be suspected, because the normal thirst response should always replace insensible water losses. 

The unmeasured anion is commonly known as the anion gap, which is normally 12 4 mEq/L. This value is useful in assessing the acid-base status of a patient and in diagnosing metabolic acidosis. Disorders that cause a high anion gap are metabolic acidosis, dehydration, therapy with sodium salts of strong acids, therapy with certain antibiotics (e.g., carbenicillin), and alkalosis. A decrease in the normal anion gap occurs in various plasma dilution states, hypercalcemia, hypermagnesemia, hypernatremia, hypoalbuminemia, disorders associated with hyperviscosity, some paraproteinemias, and bromide toxicity. 

The low plasma PCO2 leads to decreased renal tubular reabsorption of bicarbonate and increased renal excretion ofNa , K, and water. Water also is lost by salicylate-induced sweating (especially in the presence of hyperthermia) and hyperventilation dehydration, which can be profound, particularly in children, rapidly occurs. Because more water than electrolyte is lost through the lungs and by sweating, the dehydration is associated with hypernatremia. Prolonged exposure to high doses of salicylate also causes depletion ofK due to both renal and extrarenal factors. 

Thus hypernatremia occurs in diabetes insipidus because the disease causes excessive urine production and dehydration. 2... 

In hypernatremia, fluid moves out of the cells in an attempt to dilute the high concentration of sodium in the extracellular fluid. This causes cell dehydration with shrinkage, resulting in dry tissues, particularly evident in mucous membranes, loss of skin elasticity (turgor), and thirst (stimulated by ADH release). 

Some symptoms of hypernatremia may vary depending on the underlying cause. If dehydration is present owing to vomiting or diarrhea or failure to drink fluids, the urine output will be low (< 30 mL/h) with dark yellow appearance. However, if a hyperosmotic state or a condition causing decreased ADH release, such as diabetes insipidus, is... 

If dehydration is the underlying cause of hypernatremia, the primary treatment will be rehydration. Of particular concern is the rate of rehydration and use of hypotonic... 

Fluid loss and dehydration are the most common causes of hypernatremia. 

The nutritional requirement is a reflection of obligatory losses (maintenance) and the needs of growth, pregnancy, and lactation. Abnormal losses owing to disease, or in animals such as humans and horses which sweat extensively, raise the requirement. The impact of equine sweating is different from that in humans. Human sweat always contains sodium at concentrations well below plasma levels (and when aldosterone secretion is raised, levels of sweat sodium fall very low) horse sweat is hypertonic but this helps to offset the osmotic effect of the increased respiratory water loss during exertion, i.e., it may be a defense against hypernatremia, rather than a potential cause of sodium depletion. Similarly hypernatremia in many species induces dehydration natriuresis - an appropriate defense. 

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