The maintenance of the balance of flitids in the body during dialysis or other treatment.
The appropriate balance of fluid intake and output (along with dissolved salts essential for life) over 24 hours. During this period, about 2,500 millilitres (ml) of fluid should be taken in by a 70-kg man and the same amount excreted; of this, 1,500 ml will be drunk, 800 ml will be in the food eaten, and 200 ml produced by food being metabolised during digestion. Excreted water is made up of 1,500 ml of urine, 800 ml insensible loss (sweating and in the breath) and 200 ml in the faeces. A 70-kg man’s total body fluid is 42 litres — 60 per cent of body weight. Cells contain about 28 litres (intracellular fluid) and are bathed in a further 14 litres. Blood constitutes a further 5 litres. Water content is controlled mainly by the sodium concentration in the body fluids via the release of ANTIDIURETIC HORMONE from the posterior part of the PITUITARY GLAND. In seriously ill people, close monitoring of fluid intake and output, along with measurements of PLASMA sodium and calcium concentrations, is an essential factor in treatment.
Regulation of the amount of liquid in the body. A negative fluid balance (a “fluid deficit”) may occur when fluids are lost by vomiting, diarrhea, bleeding, or diaphoresis. Fluid overload may result from the excessive administration of intravenous fluids, or in diseases marked by impaired fluid excretion, such as congestive heart failure, cirrhosis, or renal failure.