Does massive blood transfusion cause acidosis or alkalosis?

From the Guidelines

Massive blood transfusion initially causes metabolic acidosis, but can later lead to metabolic alkalosis. During the early stages of massive transfusion, acidosis develops primarily due to the citrate preservative in stored blood products, which binds calcium and impairs tissue perfusion, leading to lactic acidosis 1. Additionally, stored blood contains lactic acid and becomes increasingly acidic over time due to ongoing cellular metabolism. However, as transfusion continues, metabolic alkalosis may develop because the liver metabolizes citrate to bicarbonate, causing a rise in serum bicarbonate levels. This transition typically occurs after the initial resuscitation phase, especially once bleeding is controlled and tissue perfusion improves.

Other factors contributing to acid-base disturbances during massive transfusion include hypothermia, which worsens acidosis by impairing enzyme function, and hypocalcemia from citrate binding 1. Monitoring acid-base status through arterial blood gases is essential during massive transfusion to guide appropriate management of these metabolic derangements. The most recent guideline recommends maintaining ionised calcium concentration above 0.9 mmol/l to prevent hypocalcaemia-related complications 1.

Key points to consider:

• Citrate preservative in stored blood products can cause acidosis by binding calcium and impairing tissue perfusion 1
• Liver metabolism of citrate to bicarbonate can lead to metabolic alkalosis later in the transfusion process 1
• Hypothermia and hypocalcemia can worsen acid-base disturbances during massive transfusion 1
• Monitoring acid-base status through arterial blood gases is crucial for guiding management of metabolic derangements 1

From the Research

Massive Blood Transfusion and Acid-Base Balance

• Massive blood transfusion can cause both acidosis and alkalosis, depending on various factors such as the type of blood products transfused, the rate of transfusion, and the patient's underlying condition 2, 3.
• Citrate metabolism in blood transfusions can lead to metabolic alkalosis, as citrate is metabolized to bicarbonate, increasing the plasma bicarbonate level 2, 4.
• However, massive blood transfusion can also cause a combined metabolic and respiratory acidosis, often following bicarbonate therapy 3.
• The development of acidosis or alkalosis in massive blood transfusion depends on the balance between the amount of citrate administered and the patient's ability to metabolize it 4.

Factors Influencing Acid-Base Balance

• The amount of citrate administered via blood and blood products can significantly impact the development of metabolic alkalosis 2, 4.
• The patient's serum electrolyte levels, such as potassium, sodium, and calcium, can also influence the development of acidosis or alkalosis 4, 3.
• The rate of blood transfusion and the type of blood products used can also affect the acid-base balance 3.

Clinical Implications

• Close monitoring of acid-base status, electrolyte levels, and oxygenation is essential in patients receiving massive blood transfusions 3, 5.
• Rapid correction of volume and pH, without overcorrection, is crucial to prevent complications such as metabolic alkalosis or acidosis 3.
• The use of hydrochloric acid infusion may be considered for the treatment of metabolic alkalosis in critically ill patients 5.