Ca and acid-base

Q: Acidosis __________ the bonding of albumin-calcium complex? (select one)

A) enhances

B) weakens

Answer: B

The serum calcium level measurement depends on the albumin-calcium complex's equilibrium constant. Acid-base disbalances disturb calcium-albumin bonding. Acidosis reduces this bonding, and alkalosis enhances it. 

Clinical significance: This is critically important in ICU, where the patient's acid-base level varies widely. Although formulae are available to adjust calcium per albumin, these formulae are not applicable in such situations. This is due to the fact that overall calcium or albumin level may be constant. Ideally, the ionized calcium should be measured.

#acid-base

#electrolytes

References:

1. Dickerson RN, Alexander KH, Minard G, et al. Accuracy of methods to estimate ionized and "corrected" serum calcium concentrations in critically ill multiple trauma patients receiving specialized nutrition support. JPEN J Parenter Enteral Nutr 2004; 28:133.

2. Schafer AL, Shoback DM. Hypocalcemia: Diagnosis and Treatment. [Updated 2016 Jan 3]. In: Feingold KR, Anawalt B, Blackman MR, et al., editors. Endotext [Internet]. South Dartmouth (MA): MDText.com, Inc.; 2000-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK279022/