Transfusion question....(open not closed)

[student-2]

Immediately after infusing one unit of blood the patient develops a dramatic wheeze and points to his neck in distress. You notice also a general new onset of "redness".

Question- what is your next step
for extra brownie points discuss this event and underlying possibilities.

[student-2]

CLUE- The situation described is a Type I hypersensitivity reaction

[student-2]

Give epinephrine to counter the anaphylactic reaction witnessed.

Mechanism:
IgA deficiency..........

For brownie points- before doing what test should you always test for IgA deficiency otherwise your test is irrelevant?