This version was machine-translated from German and has not been medically reviewed. The authoritative version is the German version.
Fluids, electrolytes & acid-base
20 calculators · maintenance requirements, deficits, sodium, potassium, osmolality, anion gap, compensation
Here you will find calculators for fluid requirements, electrolytes and acid-base balance in children. Included are maintenance requirements according to Holliday-Segar with deficit and losses, fluid balance and urine output according to KDIGO 2012, free water deficit, sodium deficit, sodium correction rate, potassium replacement, bicarbonate deficit, and serum and effective osmolality. In addition there are the anion gap (also albumin-corrected according to Figge 1998), delta gap, delta ratio, Winter's formula according to Albert, Dell & Winters 1967 and the acid-base compensation calculator. The calculators are intended for planning and monitoring infusion therapy and laboratory findings. Each calculator states its formula and sources.
-
Fluid calculator
Holliday-Segar maintenance requirement, 24-hour plan for dehydration and volume bolus by AWMF 068-003 -
Urine output ml/kg/h
From urine volume, weight and collection time – with the oliguria stages according to KDIGO (children and neonates) -
Fluid balance
Intake minus output over a period – with urine output in ml/kg/h and balance in % of body weight -
Free water deficit
In hypernatremia: water deficit from sodium, weight and total body water fraction, with correction limit -
Sodium deficit
In hyponatremia: sodium deficit, infusion volume according to Adrogué-Madias and correction limits of the guideline -
Corrected sodium in hyperglycemia
Sodium according to Katz (1.6) and Hillier (2.4) per 100 mg/dl glucose above 100 -
Sodium correction rate
Actual change in sodium from two measurements – compared with the guideline limits -
Potassium intake / potassium replacement
Maintenance requirement and potassium replacement per kg by severity (SCHN 2025) and RCH Melbourne – with maximum rates and concentrations -
Bicarbonate deficit
Volume of distribution × kg × (target − actual) – with selectable volume of distribution 0.3–0.5 -
Serum osmolality
Calculates from sodium, glucose and urea/BUN – conventional or SI -
Effective osmolality (tonicity)
2 × sodium + glucose – the osmotically effective osmolality without urea -
Osmolal Gap
Measured minus calculated osmolality – with ethanol correction (Purssell 2001) -
Anion gap
Na − (Cl + HCO₃), optionally with potassium – reference range according to Kraut & Madias -
Albumin-corrected Anion Gap
AG + 2.5 × (4.0 − albumin g/dl) according to Figge 1998 -
Delta gap
Anion gap minus 12 – rise in the anion gap relative to the reference value and comparison with the bicarbonate decrease -
Delta ratio
(AG − 12) ÷ (24 − HCO₃) – assessment of mixed acid–base disorders -
Corrected calcium
Albumin-corrected total calcium according to Payne – mg/dl or mmol/l -
Winter's formula
Expected pCO₂ in metabolic acidosis: 1.5 × HCO₃ + 8 ± 2 -
Acid-base compensation calculator
Primary disorder from pH, pCO₂ and HCO₃ – expected compensation according to Berend 2014 and anion gap -
Fluid overload in percent in the intensive care unit
Cumulative balance since admission in % of admission weight: (intake − output in litres) ÷ kg × 100 – without fixed thresholds
Frequently asked questions
How do I calculate the maintenance fluid requirement in children?
The fluid calculator calculates the maintenance requirement according to Holliday-Segar in ml/24 h and ml/h. In dehydration, it adds the deficit and ongoing losses to form a 24-hour plan. The calculation methods are documented in the calculator with their source.
How do I calculate the anion gap and correct it for low albumin?
The anion gap calculator forms the gap from sodium, chloride and bicarbonate and classifies it against the reference range. According to Figge et al. 1998, the albumin-corrected anion gap adds 2.5 mEq/l for each g/dl of albumin below 4.0.
How fast may sodium be corrected?
The Sodium correction rate calculator uses two sodium values and the time interval to calculate the rate in mmol/l per hour and per 24 hours, and compares it with the stored upper limits for hyponatremia.