What is the utility of base excess in an Arterial Blood Gas (ABG) result?

From the Guidelines

Base excess in an Arterial Blood Gas (ABG) result is a crucial tool for assessing metabolic acid-base disturbances, particularly in critical care settings, as it provides an indirect estimation of global tissue acidosis due to impaired perfusion, as supported by the most recent guideline 1. The utility of base excess lies in its ability to isolate the metabolic component of acid-base balance, helping clinicians distinguish between respiratory and metabolic causes of pH abnormalities.

• Normal base excess ranges from -2 to +2 mEq/L, with a positive base excess indicating metabolic alkalosis or compensation for respiratory acidosis, and a negative base excess (base deficit) indicating metabolic acidosis or compensation for respiratory alkalosis.
• The initial base deficit has been established as a potent independent predictor of mortality in patients with traumatic-hemorrhagic shock, both in adult and pediatric patients, as shown in studies 1.
• Base excess is particularly useful in settings where lactate levels may be unreliable, such as in cases of alcohol-associated trauma, where base deficit may be a better predictor of prognosis than lactate 1.
• When interpreting base excess, it should always be considered alongside other ABG parameters (pH, PCO2, HCO3-) and the patient's clinical context to develop appropriate treatment strategies for underlying acid-base disorders.
• The most recent European guideline on management of major bleeding and coagulopathy following trauma 1 highlights the importance of base deficit as a prognostic marker, further emphasizing its utility in clinical practice.

From the Research

Utility of Base Excess in ABG Results

• Base excess is a calculated parameter in an Arterial Blood Gas (ABG) result that helps in assessing the acid-base balance of the body 2.
• It is defined as the amount of base that is present in the blood in excess of the normal amount, and is usually measured in millimoles per liter (mmol/L) 3.
• The base excess can be either positive (base excess) or negative (base deficit), depending on whether the blood is alkalotic or acidotic, respectively 2.
• A positive base excess indicates that the blood is alkalotic, while a negative base excess indicates that the blood is acidotic 4.
• The utility of base excess in ABG results lies in its ability to help clinicians diagnose and manage acid-base disorders, such as metabolic acidosis and respiratory alkalosis 5, 4.
• By analyzing the base excess, clinicians can determine the severity of the acid-base disturbance and guide treatment decisions, such as the administration of alkali therapy or adjustments to ventilation 6, 3.

Clinical Applications

• Base excess is useful in evaluating patients with respiratory acidosis, as it can help determine the severity of the condition and guide treatment decisions 6.
• It is also useful in evaluating patients with metabolic acidosis, as it can help determine the underlying cause of the condition and guide treatment decisions 5.
• In addition, base excess can be used to monitor the effectiveness of treatment for acid-base disorders and to adjust treatment as needed 2, 3.
• The use of base excess in ABG results can also help clinicians to identify patients who are at risk of developing life-threatening complications, such as respiratory failure or cardiac arrest 4.