Sodium bicarbonate is a base when its concentration in blood increases the pH also increases and becomes more basic. When its concentration in the blood decreases pH decreases too and becomes more acidic.
Sodium bicarbonate must not be over-replaced, it may cause cerebral edema or in some cases, severe metabolic alkalosis.
The general rule to replace bicarbonate is; when the pH is less than 7.1 or when the concentration of bicarbonate is less than 10 mEq/L. The pH is what that matters most.
When the above criteria fulfill and you want to replace bicarbonate, first calculate the bicarb deficit by using the formula give below:
0.5 x (weight in Kgs) x (24 – patient’s bicarbonate mEq/L) = Bicarbonate deficit.
Discard the two third of the calculated deficit and transfuse the remaining one-third within one to one and half hour.
For example
Patient’s ABGs showed following values:
pH 7.0, HCO3 8, pCO2 20, pO2 100, Sat O2 98%.
and patient’s weight is: 70 kgs.
Then according to the above formula:
0.5 x (weight in Kgs) x (24 – Pt’s bicarb) = Bicarb deficit:
0.5 x 70 x (24 – 8) = 35 x 16 = 560.
Now calculate the one third of the above bicarbonate deficit.
560/3 = 186 mEq/L
Now transfuse only 186 mEq/L in one to two hours, and get the arterial blood gases (ABGs) again.
Continue to hydrate the patient per protocol, and monitor urine output and lab parameters.
Goal is to keep Bicarb more than 10 mEq/L or pH more than 7.2
Bicarbonate replacement is very crucial in the management of diabetic ketoacidosis. Diabetic ketoacidosis is a condition which has a very high mortality if not managed correctly. But if it is managed per protocol, and the patient is not in severe sepsis, then such patient usually comes out of the ketoacidosis and improves rapidly with proper management. We will discuss some useful points of DKA management elsewhere.
