Final answer:
The acid-base disturbance caused by citrate in massive transfusion is metabolic alkalosis, characterized by an excess of bicarbonate in the blood which increases blood pH. The correct answer is options 2.
Step-by-step explanation:
The acid-base disturbance caused by citrate in massive transfusion is metabolic alkalosis. Citrate is used in blood transfusions as an anticoagulant and, when large quantities of blood are transfused, the citrate can cause a transient excess of bicarbonate in the blood. This excess bicarbonate results in a condition known as primary bicarbonate excess, which is another term for metabolic alkalosis.
Metabolic alkalosis occurs when the pH of the blood is too alkaline (above 7.45) due to an excess of bicarbonate ions. This could occur in various situations, including the loss of hydrochloric acid from the stomach through vomiting, or in our case, the ingestion of substances like citrate from blood transfusions. The increased levels of bicarbonate result in an increase in blood pH, leading to metabolic alkalosis.