Twice, when donating blood platelets to the Red Cross, I鈥檝e started sneezing uncontrollably. Assistants respond immediately by giving me Tums, a brand of antacid indigestion tablet. Their explanation is that Tums restores my calcium balance. I understand how my calcium could get out of whack when my blood is being removed, filtered and given back to me without platelets, but what does this have to do with sneezing?
鈥� Donating platelets involves the use of a , which draws and separates platelets from a donor鈥檚 blood before returning red cells and plasma to the donor鈥檚 bloodstream.
A solution called acid citrate dextrose is added to the blood to stop clotting during this process: citrate, in particular, has the effect of lowering blood calcium levels to a point where the blood cannot clot in the machine.
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鈥淐itrate has the effect of lowering blood calcium levels to the point where the blood cannot clot鈥�
This calcium deficiency, or hypocalcaemia, may cause side effects when blood from the machine is returned to the donor鈥檚 body. Symptoms include tingling, chills, slight nausea, bruising, fatigue and dizziness; the most frequent one is tingling around the lips.
Sneezing is not a common side effect, but low calcium levels could cause tingling in the nasal passages and hence sneezing.
The treatment for this is first to slow down the rate of platelet collection and then to supply the donor with antacid tablets, a rich source of supplementary calcium. If this is not effective, the procedure may have to be halted until symptoms resolve and a decision made over whether to proceed at a lower rate of platelet collection.
Richard Benjamin, Chief medical officer, American Red Cross, Washington DC, US