This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
A young donor came to the blood bank for the first time for platelet apheresis with platelet count of 1.9L. During the course he developed paresthesias, circumoral numbness during donation. His vitals remain stable though. ECG showed tachycardia with ST-T changes. What is the reason for his symptoms? 
Select and explain. 
A. Hypovolemic shock, B. Hypocalcemia, C. Seizures, D. Allergic reaction
B: Hypocalcemia
Answer: B: Hypocalcemia 
Explanation: Ans. b. HypocalcemiaClinical findings of paresthesias, circumoral numbness and ECG showing tachycardia with ST-T changes are highly suggestive of hypocalcemia, which has been caused by extensive transfusion of citrated blood."Citrate, commonly used to anticoagulate blood components, chelates calcium and thereby inhibits the coagulation cascade. Hypocalcemia, manifested by circumoral numbness and/or tingling sensation of the fingers and toes, may result from multiple rapid transfusions."-H,"Transient hypocalcemia is seen with severe sepsis, burns, acute kidney injury, and extensive transfusions with citrated blood.