HCO3- DEFICIT CALCULATOR: This free software application is to be used to calculate HCO3- (bicarbonate) deficits in patients with metabolic acidosis. I have personally used this application for years for rapid calculations in the ICU setting. The calculations can be done both with and without an ABG even though IV NaCO3- should not be used if the pH is greater than 7.2. Also using the pH and pCO2 from an arterial blood gas helps avoid over correction. The initial calculation can be made with only 2 variables: body weight and serum CO2 (bicarbonate). The third field asks for the HCO3 Goal which I preset at 20 (to change this value enter a new value, and the new value will be saved during the calculation. From these 3 variables the application generates 2 fields of data on the bottom, the HCO3 Deficit and Amps HCO3. Let''s start with the HCO3 Deficit. The HCO3 Deficit is usually calculated by the following formula: Def = (Desired HCO3 - HCO3(serum CO2, not pCO2 from an ABG)) * (body weight (kg) * 0.6) So that''s 20 - current bicarbonate times patient''s weight in kilograms times 0.6. The body weight should be lean body weight, but obviously this is hard to determine especially in ICU''s where edema and anascarca are not uncommon and some guides say use 0.5 instead of 0.6. If you look at my calculations you see 2 numbers giving you a range. The first calculation is done using 0.3 instead of 0.6 giving an approximate half deficit. The current literature supports using a half dose as an initial dose then to redraw ABG and metabolic profile and recalculate. Most of the current literature recommends stopping all IV NaHCO3 when the pH is 7.2 or greater. It is also important to follow other electrolytes like calcium, potassium and sodium and make adjustments in your therapy as needed. Please also note that in high-AG acidosis secondary to accumulation of ORGANIC ACIDS, LACTATES and KETONES these anions are eventually metabolized to HCO3- and care must be taken to avoid an overshoot alkalosis. I RARELY USE NaHCO3 in the treatment of DKA. Below the HCO3 Deficit field is a field showing number of NaHCO3 Amps needed (1 Amp contains 50 meq NaHCO3) to correct the bicarbonate deficit with the first number using the 0.3 and the second number 0.6. Above the HCO3 Deficit field is a field showing number of NaHCO3 Amps needed (1 Amp contains 50 meq NaHCO3) to make the arterial pH 7.4 based on an equation by (Pincus et al)* which utilizes the pH and pCO2 from an ABG. In the Exp HCO3 field the calculated HCO3- is shown from the pH and CO2 utilizing the Pincus & Henderson-Hasselbalch equations. The pH 7.4 value is usually close to the first value calculated in the NaHCO3 Amps needed field. *Alternative Equation (Pincus et al) Pincus MR, Preuss HG, Henry JB. Chapter 7: Evaluation of renal function, water,electrolytes, acid-base balance, and blood gases.page 153. IN: Henry JB. Clinical Diagnosis and Management by Laboratory Methods, 19th Edition. W.B. Saunders Company. 1996.
