Metabolic alkalosis: The following equations represent different methods of
correction utilizing either the serum HCO3-, the serum
chloride, or the base excess
Dose of mEq NH4Cl = [0.2 L/kg x body weight (kg)] x [103 -
observed serum chloride]; administer 100% of dose over 12 hours, then
re-evaluate
Note: 0.2 L/kg is the estimated chloride space and 103 is the average
normal serum chloride concentration
Dosing of mEq NH4 Cl via the bicarbonate-excess method
(refractory hypochloremic metabolic alkalosis):
Dose of NH4Cl = [0.5 L/kg x body weight (kg)] x (observed serum
HCO3- - 24); administer 50% of dose over 12 hours, then
re-evaluate
Note: 0.5 L/kg is the estimated bicarbonate space and 24 is the
average normal serum bicarbonate concentration
Dosing of mEq NH4 Cl via the base-excess
method:
Dose of NH4Cl = [0.3 L/kg x body weight (kg)] x measured base
excess (mEq/L); administer 50% of dose over 12 hours, then re-evaluate
Note: 0.3 L/kg is the estimated extracellular bicarbonate and base
excess is measured by the chemistry lab and reported with arterial blood gases
These equations will yield different requirements of ammonium chloride
Equation #1 is inappropriate to use if the patient has severe metabolic
alkalosis without hypochloremia or if the patient has uremia
Equation #3 is the most useful for the first estimation of ammonium chloride
dosage
Children: Urinary acidifying agents: Oral, I.V.: 75 mg/kg/day in 4 divided
doses; maximum daily dose: 6 g
Adults: Urinary acidifying agent/diuretic:
Oral: 1-2 g every 4-6 hours
I.V.: 1.5 g/dose every 6 hours