Calculates the Serum Anion Gap (AG) to evaluate metabolic acidosis. The Anion Gap represents the difference between measured cations (Sodium) and measured anions (Chloride and Bicarbonate). An optional calculation for the Albumin-Corrected Anion Gap is included, which adjusts for hypoalbuminemia, a common cause of a falsely low anion gap.
Usage
calculate_anion_gap(sodium, chloride, bicarbonate, albumin = NULL)
Value
A list containing:
Anion_Gap
The calculated Anion Gap.
Corrected_Anion_Gap
The Anion Gap adjusted for albumin level (if albumin is provided).
Arguments
sodium
Numeric. Serum Sodium level in mEq/L or mmol/L.
chloride
Numeric. Serum Chloride level in mEq/L or mmol/L.
bicarbonate
Numeric. Serum Bicarbonate (or total CO2) level in mEq/L or mmol/L.
albumin
Numeric (Optional). Serum Albumin level in g/dL. Used to calculate the Corrected Anion Gap.
Details
The basic formula is:
$$AG = Na - (Cl + HCO3)$$
The Albumin-Corrected Anion Gap formula is:
$$Corrected AG = AG + (2.5 \times (4.4 - Albumin))$$
Normal Anion Gap range is typically considered 4-12 mEq/L, though this varies by laboratory assay.
References
Emmett M, Narins RG. Clinical use of the anion gap. Medicine (Baltimore). 1977;56(1):38-54.
Figge J, Jabor A, Kazda A, Fencl V. Anion gap and hypoalbuminemia. Crit Care Med. 1998;26(11):1807-1810.