Maintenance and replacement fluid therapy in adults
- Richard H Sterns, MD
Richard H Sterns, MD
- Section Editor — Fluid and Electrolytes
- Professor of Medicine
- University of Rochester School of Medicine and Dentistry
A critical role of the kidneys is to maintain the effective circulating volume and plasma osmolality within relatively narrow limits, as well as to maintain electrolyte homeostasis. The normal homeostatic mechanisms that maintain the effective circulating volume and plasma osmolality are discussed elsewhere. (See "General principles of disorders of water balance (hyponatremia and hypernatremia) and sodium balance (hypovolemia and edema)".)
Under normal circumstances, the kidneys can adjust to wide variations in dietary intake by appropriate variations in water and electrolyte excretion , which is particularly important when discussing maintenance fluid requirements.
Water balance — Water losses lead to an increase in serum sodium and osmolality, resulting in stimulation of thirst and increased release of antidiuretic hormone (ADH). In normal individuals, these changes will lead to increased water intake and reduced water excretion, which will restore normal water balance. Thus, patients who are alert, have an intact thirst mechanism, and access to water will not become hypernatremic. (See "Etiology and evaluation of hypernatremia".)
On a normal diet, the minimum water intake is estimated at 500 mL/day (assuming there are no increased losses). This value is based upon the balance of total water intake and production and the minimum rate of urinary loss. Individuals who can concentrate their urine to 1200 mosmol/kg who excrete 600 mosmol of solute (sodium and potassium salts and urea) per day will have a minimum urine output of 500 mL (600 mosmol ÷ 1200 mosmol/kg).
There are two other sources of water in addition to fluid ingestion: the water content of food (fruits and vegetables are almost 100 percent water by weight) and the water generated by oxidation of carbohydrates. There are also other sources of water loss in addition to the urine output: insensible losses and sweat.
- Rose BD, Post TW. Clinical Physiology of Acid-Base and Electrolyte Disorders, 5th ed, McGraw-Hill, New York 2001. p.285.
- Shafiee MA, Bohn D, Hoorn EJ, Halperin ML. How to select optimal maintenance intravenous fluid therapy. QJM 2003; 96:601.
- WATKIN DM, FROEB HG, HATCH FT, GUTMAN AB. Effects of diet in essential hypertension. II. Results with unmodified Kempner rice diet in 50 hospitalized patients. Am J Med 1950; 9:441.
- MURPHY RJ. The effect of "rice diet" on plasma volume and extracellular fluid space in hypertensive subjects. J Clin Invest 1950; 29:912.
- Sterns RH, Silver SM. Salt and water: read the package insert. QJM 2003; 96:549.
- Rose BD, Post TW. Clinical Physiology of Acid-Base and Electrolyte Disorders, 5th ed, McGraw-Hill, New York 2001. p.441.
- Lu KC, Hsu YJ, Chiu JS, et al. Effects of potassium supplementation on the recovery of thyrotoxic periodic paralysis. Am J Emerg Med 2004; 22:544.
- McCowen KC, Malhotra A, Bistrian BR. Stress-induced hyperglycemia. Crit Care Clin 2001; 17:107.
- Rosmarin DK, Wardlaw GM, Mirtallo J. Hyperglycemia associated with high, continuous infusion rates of total parenteral nutrition dextrose. Nutr Clin Pract 1996; 11:151.
- Schloerb PR, Henning JF. Patterns and problems of adult total parenteral nutrition use in US academic medical centers. Arch Surg 1998; 133:7.
- Wolfe RR, Allsop JR, Burke JF. Glucose metabolism in man: responses to intravenous glucose infusion. Metabolism 1979; 28:210.
- Sheean P, Braunschweig C. The incidence and impact of dextrose dose on hyperglycemia from parenteral nutrition (PN) exposure in hematopoietic stem cell transplant (HSCT) recipients. JPEN J Parenter Enteral Nutr 2006; 30:345.
- Water balance
- Sodium balance
- Fluid therapy
- MAINTENANCE FLUID THERAPY
- REPLACEMENT FLUID THERAPY
- Volume deficit
- Rate of repletion
- Choice of replacement fluid
- - Hypernatremia
- - Hyponatremia
- - Addition of potassium
- - Addition of bicarbonate
- SALINE ALONE OR WITH DEXTROSE
- Dextrose-induced hyperglycemia
- SUMMARY AND RECOMMENDATIONS
- Maintenance therapy
- Replacement therapy