Master How to Interpret Acid Base Disorders with Picmonic for Nursing RN

The first step to acid-base lab value interpretation is to look at pH. Blood pH is normally 7.35-7.45. pH is determined by the amount of hydrogen ions contained in the blood.

A pH of less than 7.35 is termed acidosis. Acidosis indicates a buildup of carbonic acid in the blood.

A pH higher than 7.45 is termed alkalosis. Alkalosis indicates a buildup of bicarbonate (bases) and/or a general decrease in carbonic acid in the blood.

The second step is to examine the partial pressure of carbon dioxide in the blood. pCO₂ is normally 35-45 mmHg and is regulated primarily through respiration.

Opposite Respiratory and pH directions indicate a respiratory disorder. If the pCO₂ is not in the opposite direction of the pH, then check the HCO₃ next.

Respiratory acidosis is often indicated by a pH of less than 7.35 and a pCO₂ of higher than 45 mmHg.

Respiratory Alkalosis is indicated by a pH of more than 7.45 and a pCO₂ of less than 35 mmHg.

The normal value of bicarbonate is 22-26 mmol/L. The amount of the base HCO₃, bicarbonate, in the blood is regulated in the kidneys.

If the HCO₃ (bicarbonate) is going in the same direction as pH, then the problem is most likely a metabolic problem.

The patient with Metabolic acidosis can grossly be determined as Down, Down, Down (Decreased pH, Decreased pCO₂, Decreased HCO₃).

Metabolic alkalosis can grossly be determined as UP, UP, UP (Increased pH, Increased pCO₂, Increased HCO₃).