Dilutional acidosis: where do the protons come from?

Area of Science:

• Physiology
• Biochemistry
• Medical Science

Background:

• Understanding the mechanisms of acid-base balance is crucial in clinical settings.
• Saline infusions are common medical procedures with potential to affect acid-base status.
• Distinguishing between dilutional and hyperchloremic acidosis is clinically important.

Purpose of the Study:

• To investigate the underlying mechanisms of acidosis following saline infusion.
• To differentiate between dilutional and hyperchloremic acidosis.
• To elucidate the role of carbon dioxide (CO(2)) in post-infusion acid-base changes.

Main Methods:

• Computerized simulation of extracellular fluid dilution using distilled water, normal saline, and lactated Ringer's solution.
• Modeling systems as either closed or open to alveolar gases.
• In vitro validation experiments using human plasma dilution.

Main Results:

• In closed systems, dilution with various solutions did not alter pH due to proportional decreases in determinants.
• Distilled water dilution in closed systems increased pH due to increased carbonic pK from reduced ionic strength.
• Acidosis developed only in open systems due to increased CO(2) content.

Conclusions:

• Increased proton concentration post-dilution arises from CO(2) hydration, specifically in systems open to gases.
• Both Stewart's strong ion difference approach and traditional methods can explain these findings.
• The development of acidosis is contingent on gas exchange dynamics.