**15. Albumin, phosphate, lactate and corrected anion gap**

At normal blood pH 7.4 plasma proteins are mostly anionic. It has been estimated that anion gap decreases by 2.5 mEq/L for every 10 gm/L drop of serum albumin [36, 37]. Several studies had observed that 2–2.5 times changes in albumin influences in anion gap changes [58]. Albumin contributes a greater part of the normal anion gap [46]. Phosphate and lactate contribute some anion gap as well [59]. Consideration of all of these contributors are important in explaining changes in anion gap. Calculation of anion gap is crucial in critically ill patients. Anion gap should be adjusted for Eq. (7) albumin, phosphate and lactate with the following equation [59].

 Anion gap = {(Na) + (K) − (Cl) − (HCO3)} − {2 × albumin g/dl + 0.5 × phosphate mg/dl} − {lactate mmol/L} (7)
