Quick test interpretation

Here we provide quick guides (tables and algorithms) to interpreting changes in acid-base results from a standard chemistry panel.

Simple disturbances

Respiratory disturbances

The following table provides a summary of the changes in the blood gas (pH, pCO2) with primary respiratory acid-base disturbances, based on the type of disturbance. Note, that a respiratory disturbance cannot be detected from a biochemical panel and a respiratory disturbance does not alter BE.

Disturbance	pCO2	Effect on pH
Respiratory acidosis	↑	↓
Respiratory alkalosis	↓	↑

Metabolic disturbances

The following table provides a summary of the changes in the blood gas (pH, HCO₃^–, BE) and biochemical panel (HCO₃^–, AG, strong ion difference and chloride changes in relation to sodium) with primary metabolic acid-base disturbances, based on the type of disturbance. The strong ion difference = (Na⁺ + K⁺) – Cl^–.

Disturbance	HCO3– or BE	AG	Strong ion difference	Chloride versus sodium	Effect on pH
Titration metabolic acidosis	↓	↑	normal	normal	↓
Strong ion metabolic acidosis	↓	normal	↓	↑	↓
Metabolic alkalosis	↑	normal	↑	↓	↑

 

Compensation

The table below represents compensatory (secondary) responses to a single primary blood gas disturbance (respiratory or metabolic).  As can be seen, the change in the primary parameter (HCO₃^– for metabolic and pCO₂ for respiratory) is paralleled by the compensatory response.

Primary disorder	pH	[H+]	Primary change	Compensation
Metabolic acidosis	↓	↑	↓ HCO3–	↓ pCO2
Metabolic alkalosis	↑	↓	↑ HCO3–	↑ pCO2
Respiratory acidosis	↓	↑	↑ pCO2	↑ HCO3–
Respiratory alkalosis	↑	↓	↓ pCO2	↓ HCO3–

Mixed disturbances

Some examples of mixed acid-base disturbances and the changes that ensue are shown in the table below. Note that not all possible combinations are shown in this table. Strong ion difference is calculated as above