Maintenance Fluid Calculation

Introduction to Fluid Calculation

The Holliday-Segar formula is recommended for calculating maintenance fluid requirements, which is 100 ml/kg/day for the first 10 kg of body weight, plus 50 ml/kg/day for the next 10 kg, plus 25 ml/kg/day for each kg above 20 kg, based on the principle that water requirements parallel energy needs at approximately 1 kcal per 1 ml of water, as suggested by the American Society for Parenteral and Enteral Nutrition 1, 2, 3

The American Academy of Pediatrics recommends using isotonic fluids, such as 0.9% saline or balanced crystalloids, for maintenance hydration in acutely ill children, especially during the first 24 hours, due to Level 1+ evidence showing that hypotonic fluids significantly increase the risk of hospital-acquired hyponatremia and potentially fatal hyponatremic encephalopathy 1, 2, 4
Balanced/buffered crystalloids are preferred over 0.9% saline for initial resuscitation in critically ill children, although this is a weaker recommendation based on lower quality evidence, as stated by the Society of Critical Care Medicine 5

In acutely and critically ill children at risk of increased antidiuretic hormone (ADH) secretion, maintenance fluid volume should be restricted to 65-80% of the Holliday-Segar calculated volume to prevent hyponatremia and fluid overload, as recommended by the Pediatric Critical Care Society 4
For patients with heart failure, renal failure, or hepatic failure, fluid restriction to 50-60% of calculated volume is recommended, based on guidelines from the American Heart Association 4

Water requirements increase with fever, hyperventilation, hypermetabolism, and gastrointestinal losses, as stated by the American Society for Parenteral and Enteral Nutrition 1
Water requirements decrease with renal failure, congestive heart failure, and critical illness with mechanical ventilation, according to the National Kidney Foundation 1, 6

Total daily maintenance fluid should be calculated by including all sources, such as IV fluids, blood products, IV medications, arterial/venous line flushes, and enteral intake, to prevent "fluid creep" and fluid overload, as recommended by the Society of Critical Care Medicine 4
Fluid overload, defined as >10% increase in cumulative fluid balance from baseline, is an independent predictor of morbidity, mortality, prolonged mechanical ventilation, and increased length of stay, according to the American Thoracic Society 4

Fluid balance and clinical status should be reassessed at least daily, with regular monitoring of serum electrolytes, especially sodium, to prevent hyponatremia and fluid overload, as recommended by the American Society for Parenteral and Enteral Nutrition 4
The induced change in serum osmolality should not exceed 3 mOsm/kg/hour during fluid replacement, based on guidelines from the Endocrine Society 1, 7, 6

Potassium supplementation of 20-40 mEq/L (2/3 KCl and 1/3 KPO4) is recommended once renal function is assured and serum potassium is known, as stated by the American Society for Parenteral and Enteral Nutrition 1, 7, 6
Sodium requirements are 1-3 mmol per 100 kcal, and potassium requirements are 1-3 mmol per 100 kcal, according to the National Academy of Sciences 1