Maintenance Fluids Calculator

Maintenance intravenous fluids replace the water and electrolytes a stable patient normally needs over a day when ordinary oral intake is unavailable or inadequate. The estimate is not intended to replace resuscitation fluid, correct a pre-existing deficit, or match ongoing abnormal losses. It provides a starting rate that clinicians adjust after reviewing the patient's diagnosis, examination, urine output, laboratory results, medications, and response to treatment. This calculator applies the Holliday-Segar method to body weight. For the first 10 kilograms it allocates 100 milliliters per kilogram per day. For weight from 10 through 20 kilograms it adds 50 milliliters per kilogram per day, and above 20 kilograms it adds 20 milliliters per kilogram per day. The hourly 4-2-1 rule mirrors those tiers: 4 milliliters per kilogram per hour for the first 10 kilograms, 2 for the next 10, and 1 for every kilogram above 20. Because the daily and hourly conventions use rounded clinical tiers, multiplying the hourly result by 24 may not exactly reproduce the daily figure. Weight can be entered in kilograms or pounds. Pounds are converted to kilograms before either formula is applied. Accurate current weight is important, especially for infants and small children, because each kilogram has a larger proportional effect on the result. In patients with obesity, edema, ascites, or large recent weight changes, a clinician may select ideal, adjusted, or dry weight rather than the number shown on a scale. Maintenance needs often fall during acute illness. Cardiac failure, kidney dysfunction, liver disease, inappropriate antidiuretic hormone secretion, postoperative stress, and some medications can increase the danger of fluid overload or hyponatremia. Fever, tachypnea, gastrointestinal losses, burns, and high urine output can increase requirements, but those additional losses should be assessed separately instead of silently folded into the maintenance formula. Use the result as a transparent reference point and document the assumptions behind the chosen prescription. Reassess weight, fluid balance, sodium, potassium, creatinine, glucose, and clinical signs at intervals appropriate to the patient's risk. Children, older adults, and critically ill patients may deteriorate quickly when a rate is inappropriate. Only a qualified professional with access to the full clinical picture should order or change intravenous therapy.