Thread by @medrants

1/ #UncleBob - how I use the delta gap. Hopefully worth #5goodminutes

@UnremarkableLab

Here is the idea - we have an increased anion gap and want to see if the patient also has either a normal gap metabolic acidosis or metabolic alkalosis. Here are the assumptions:

2/ Expected gap = 11 - 2.5*(albumin -4) but that is hard to remember, so we use a reasonable approximation = albumin * 3.
Example, patient has an albumin of 2.3 so we expect a gap of 7.

3/ Second assumption - the increased anion gap has replaced bicarbonate. - thus treating the gap will restore bicarbonate

2 examples to follow:

4/ Ex. 1
So - patient has the following labs:
Na 138 Cl 90 HCO3 16 albumin 4
Gap = 32
Expected gap = 12
Delta gap = 32-12 = 20
Estimated HCO3 if we "fix the gap" = 16 + 20 = 36
Thus, the patient has both an anion gap acidosis and an underlying metabolic alkalosis

5/ Ex. 2

Na 136 Cl 106 HCO3 10 Albumin 3.6
Gap = 20
Expected gap = 11
Delta gap = 20 - 11 = 9
Estimated HCO3 if we "fix the gap" = 10 + 9 = 19
Thus, the patient has both an anion gap acidosis and a normal gap acidosis

Hope this is helpful.