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, Cl^–_corr) with primary metabolic acid-base disturbances, based on the type of disturbance.

Disturbance	HCO₃^– BE	AG	Cl^–_corr	Effect on pH
Titration metabolic acidosis	↓	↑	normal	↓
Bicarbonate loss 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.

HCO₃^–	pCO₂	AG	Cl^–_corr	Disorders	Expected pH
↓	↑	↑	↓	Primary titration metabolic acidosis (low HCO₃^– high AG) AND respiratory acidosis (high pCO₂) AND primary or compensatory metabolic alkalosis (low Cl^–_corr)	N to ↓ (depending on if the alkalosis is primary or secondary)
N	N	↑	↓	Primary titration metabolic acidosis (high AG) AND metabolic alkalosis (low Cl^–_corr)	N, ↑, ↓ (depends on dominating disturbance)
↑	↓	N	↓	Primary metabolic alkalosis (high HCO₃^–, low Cl^–_corr) AND respiratory alkalosis (low pCO₂)	↑↑
↓↓	↓	↑	↑	Primary titration AND loss metabolic acidosis (very low HCO₃^–, high AG, high Cl^–_corr), compensatory respiratory alkalosis (low pCO₂)	↓

Diagnostic algorithms

Interpretation of bicarbonate results from a chemistry panel
High bicarbonate	Normal bicarbonate	Low bicarbonate
Interpretation of blood gas results
Traditional interpretation	Strong ion interpretation