Fluid and electrolyte balance

Saltin, B. Costill, D.L. (1988). Fluid and electrolyte balance during prolonged exercise. In Exercise, Nutrition, and Energy Metabolism (Horton, E.S. Teijung, R.L., ed), pp. 150-158, MacMillan. New York. 

The posterior pituitary is innervated by direct nervous stimulation from the hypothalamus, resulting in the release of specific hormones. The hypothalamus synthesizes two hormones, oxytocin and vasopressin. These hormones are stored in and released from the posterior pituitary lobe. Oxytocin exerts two actions (1) it promotes uterine contractions during labor, and (2) it contracts the smooth muscles in the breast to stimulate the release of milk from the mammary gland during lactation. Vasopressin is an antidiuretic hormone (ADH) essential for proper fluid and electrolyte balance in the body. Specifically, vasopressin increases the permeability of the distal convoluted tubules and collecting ducts of the nephrons to water. This causes the kidney to excrete less water in the urine. Consequently, the urine becomes more concentrated as water is conserved. 

The kidneys are organs specialized to filter the blood. As such, they make an important contribution to the removal of metabolic waste products as well as to maintenance of fluid and electrolyte balance. Specific functions of the kidneys include ... 

Renal replacement therapy (RRT), such as hemodialysis and peritoneal dialysis, maintains fluid and electrolyte balance while removing waste products. See Table 75-4 for indications for RRT in ARF. Intermittent and continuous options have different advantages (and disadvantages) but, after correcting for severity of illness, have similar outcomes. Consequently, hybrid approaches (e.g., sustained low-efficiency dialysis and extended daily dialysis) are being developed to provide the advantages of both. 

Corticosteroids synthesized by the adrenal gland are mineralocorticoids and GC. Min-eralocorticoids regulate fluid and electrolyte balance by affecting ion transport in the kidney. Cortisol, the primary circulating GC in most species (including humans), has many activities, including resistance to stress, regulation of intermediary metabolism, and immunosuppressive and anti-inflammatory effects. GC synthesis and secretion is... 

Medical Management No specific viral therapy exists so treatment is supportive only. Treat patients with uncomplicated VEE infection with analgesics to relieve headache and myalgia. Patients who develop encephalitis could require anticonvulsants and intensive care to maintain fluid and electrolyte balance, ensure adequate ventilation, and avoid complicating secondary bacterial infections. Patients should be treated in a screened room or in quarters treated with residual insecticide for at least five days after onset, or until afebrile (without fever) to foil mosquitoes since humans may remain infectious for mosquitoes for at least seventy-two hours. Isolation and qaurantine is not required. Standard Precautions should be practiced when dealing with infection control for VEE victims as shown below ... 

No specific antidote has been shown to be effective in treating 1,2-dibromoethane intoxication once absorption into the bloodstream has occurred (Ellenhorn and Barceloux 1988). Intravenous infusions of glucose may limit the hepatotoxicity of 1,2-dibromoethane (ERA 1989b). During the recovery phase, a diet rich in vitamin B and carbohydrates may limit liver damage (Dreisbach and Robertson 1987 Lawrence and Michaels 1984). Hemodialysis may be needed to regulate extracellular fluid and electrolyte balance and to remove metabolic waste products if renal failure occurs (ERA 1989b). 

Gelatin is a plasma substitute. Plasma substitutes should not be used to maintain plasma volume in burns or peritonitis. In these scenarios albumin should be given. Close monitoring, including monitoring of fluid and electrolyte balance and urine output, is required in patients being administered plasma and plasma substitutes. Plasma substitutes should also be used with caution in patients with cardiac disease, liver disease or renal impairment. 

Mineralocorticoids are endogenous compounds that have an effect on fluid and electrolytic balance in the body, mainly by promoting sodium retention in the kidney. 

Patients with CRF not requiring dialysis Patients with CRF not yet requiring dialysis may require lower maintenance doses of darbepoetin than patients receiving dialysis. Predialysis patients may be more responsive to the effects of darbepoetin, and require judicious monitoring of blood pressure and hemoglobin. Also closely monitor renal function and fluid and electrolyte balance. 

Fluid and electrolyte balance Average and large doses of hydrocortisone or cortisone can cause elevation of blood pressure, salt and water retention, and increased excretion of potassium. These effects are less likely to occur with the synthetic derivatives except when used in large doses. 

Fluid and electrolyte balance Monitor fluid and electrolyte balance and body weight. Give with a diuretic to prevent fluid retention and possible CHF a loop diuretic is usually required. If used without a diuretic, retention of several hundred mEq salt and corresponding volumes of water can occur in a few days, leading to increased plasma and interstitial fluid volume and local or generalized edema. 

Monitoring Monitor initially and periodically thereafter body weight, blood pressure, fluid, and electrolyte balance signs and symptoms of pericardial effusion ECG changes CBC alkaline phosphatase renal function tests. 

Hyperkalemia Carefully evaluate patients for possible fluid and electrolyte balance disturbances. Hyperkalemia may occur with impaired renal function or excessive potassium intake and can cause cardiac irregularities that may be fatal. Ordinarily, do not give potassium supplements with spironolactone. 

Treatment- Primarily symptomatic and supportive maintain proper fluid and electrolyte balance and administer a tranquilizer to suppress anxiety. Severe withdrawal symptoms may require narcotic replacement. Gradual withdrawal using successively smaller doses will minimize symptoms. 

Severe emesis - Severe emesis should not be treated with an antiemetic drug alone where possible, establish cause of vomiting. Direct primary emphasis toward restoration of body fluids and electrolyte balance, and relief of fever and causative disease process. Avoid overhydration which may result in cerebral edema. 

Fluid and electrolyte balance Excessive laxative use may lead to significant fluid and electrolyte imbalance. Monitor patients periodically. 

The few animal studies located appear to be in general agreement with the human findings (Gardner et al. 1925 Korsrud et al. 1972). Effects of carbon tetrachloride ingestion on blood pressure are sometimes observed, but these are likely secondary to effects on the central nervous system, or to effects on fluid and electrolyte balance following renal injury. 

While the rate limiting step of the cascade is the renin release, the biological active component is the octapeptide angiotensin n. It is an essential regulator of fluid and electrolyte balance as well as blood pressure. It exerts its actions on various structures like blood vessels, adrenal cortex, kidney and central nervous system. Although at least two different receptor subtypes for angiotensin II have been identified (ATi and AT2) the ATi-subtype is responsible for most of the cardiovascular effects of the agonist. 

Mecftanism of Action Sodium Is a major cat ion of extracellular fluid that controls water distribution, fluid and electrolyte balance, and osmotic pressure of body fluids it also maintains acid-base balance. 

Monitor fluid and electrolyte balance, correcting any imbalance. 

Thiazide diuretics considerably reduce renal clearance of lithium and should be avoided. Loop diuretics, such as furosemide (frusemide), seem to have less likelihood of such effects but any drug affecting fluid and electrolyte balance... 

Ang II exerts important actions at vascular smooth muscle, adrenal cortex, kidney, heart, and brain. Through these actions, the renin-angiotensin system plays a key role in the regulation of fluid and electrolyte balance and arterial blood pressure. Excessive activity of the renin-angiotensin system can result in hypertension and disorders of fluid and electrolyte homeostasis. 

Chronic alcohol use has important effects on the endocrine system and on fluid and electrolyte balance. Clinical reports of gynecomastia and testicular atrophy in alcoholics with or without cirrhosis suggest a derangement in steroid hormone balance. 

Individuals with chronic liver disease may have disorders of fluid and electrolyte balance, including ascites, edema, and effusions. Alterations of whole body potassium induced by vomiting and diarrhea, as well as severe secondary aldosteronism, may contribute to muscle weakness and can be worsened by diuretic therapy. The metabolic derangements caused by metabolism of large amounts of ethanol can result in hypoglycemia, as a result of impaired hepatic gluconeogenesis, and in ketosis, caused by excessive lipolytic factors, especially increased cortisol and growth hormone. 

Chloride, a normal constituent of extracellular fluid in the body, is an important anion in the maintenance of fluid and electrolyte balance, as well as a necessary component of gastric juice. Whole milk contains 103 mg chloride per 100 g (NDC 1983A). 

The most serious side effects of diuretics are fluid depletion and electrolyte imbalance.13,88 By the very nature of their action, diuretics decrease extracellular fluid volume as well as produce sodium depletion (hyponatremia) and potassium depletion (hypokalemia). Hypokalemia is a particular problem with the thiazide and loop diuretics, but occurs less frequently when the potassium-sparing agents are used. Hypokalemia and other disturbances in fluid and electrolyte balance can produce serious metabolic and cardiac problems and may even prove fatal in some individuals. Consequently, patients must be monitored closely, and the drug dosage should be maintained at the lowest effective dose. Also, potassium supplements are used in some patients to prevent hypokalemia. 

By the very nature of their action, diuretics are often associated with disturbances in fluid and electrolyte balance. Volume depletion, hyponatremia, hypokalemia, and altered pH balance are among the most fre-... 

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