Clinical acid-base pathophysiology: disorders of plasma anion gap
1Department of Internal Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, 75390-8856, USA. orson.moe@utsouthwestern.edu
Abstract:
The plasma anion gap is a frequently used parameter in the clinical diagnosis of a variety of conditions. The commonest application of the anion gap is to classify cases of metabolic acidosis into those that do and those that do not leave unmeasured anions in the plasma. While this algorithm is useful in streamlining the diagnostic process, it should not be used solely in this fashion. The anion gap measures the difference between the unmeasured anions and unmeasured cations and thus conveys much more information to the clinician than just quantifying anions of strong acids. In this chapter, the significance of the anion gap is emphasized and several examples are given to illustrate a more analytic approach to using the clinical anion gap; these include disorders of low anion gap, respiratory alkalosis and pyroglutamic acidosis.
Related Concept Videos
Roles of Electrolytes: Chloride and Bicarbonate
Conditions such as hypochloremia can arise from insufficient chloride reabsorption by the kidneys, often compounded by extended bouts of diarrhea, vomiting, or...
Acid-Base Balance
When the pH of arterial blood rises above 7.45, it results in a condition called alkalosis. Conversely, a drop below 7.35 leads to...
Respiratory Regulation of Acid-Base Balance
When carbon dioxide levels increase in the blood, more H+ and HCO3⁻ are produced, leading to a...
Renal Regulation of Acid-Base Balance
In the kidneys, cells within the proximal convoluted tubules (PCT) and the collecting ducts secrete hydrogen ions (H+) into the tubular fluid. Specifically, in the PCT, Na+/H+ antiporters secrete H+ while reabsorbing Na+.
However, the intercalated cells in...
Disorders of Acid-Base Balance
Respiratory Acidosis and Alkalosis
Respiratory acidosis occurs due to an increase in the partial pressure of carbon dioxide PCO2 in the blood. It often arises from shallow breathing or impaired gas exchange caused by...
Diagnosing Acidosis and Alkalosis
First, the pH level is assessed to determine whether the blood pH is normal (7.35–7.45), low (acidosis), or high (alkalosis).
Next, the PCO2 and HCO3− values are examined to...


