Albumin and anion gap

 Q: Albumin has a significant (select one) 

 A) net negative charge 

B) net positive charge

Answer: A

The objective of this question is to lead readers toward the importance of albumin in an-ion gap calculation. ICU patients tend to have low albumin for various reasons and it can affect the calculation of an-ion gap.

To maintain hemostasis, the human body exists in balance: 

 Total serum cations = Total serum anions 

 In other words:

   Na + All unmeasured cations = Cl + HCO3 + All unmeasured anions 

With a negative charge, albumin is a significant role-player in this equation. The formula to adjust the anion gap is 

Corrected serum anion gap = (Serum anion gap measured) + (2.5 x [4.5 - Observed serum albumin]) 

 Simply, the anion gap falls by approximately 2.5 mEq/L for every 1 g/dL below normal (4.5 g/L) of serum albumin concentration.

#acid-base

Reference:

Feldman M, Soni N, Dickson B. Influence of hypoalbuminemia or hyperalbuminemia on the serum anion gap. J Lab Clin Med 2005; 146:317.