In vitro hemolysis occurring before or after a blood transfusion may mimic an in vivo hemolytic transfusion reaction.



Before or During Infusion

Blood Sample Handling

freezing blood

environmental or unregulated refrigerator

environmental, specimen handling, or unregulated refrigerator

overheating blood

blood warmer or makeshift warmer; placing blood on a room heater

specimen handling

mixing with hypotonic or hypertonic solution

infusion of blood with an IV solution; addition of a drug

drawing from a peripheral line running an infusion

small needle with high pressure

use of pressure bag forcing flow through small needle

difficult draw with large syringe


Some causes of in vitro hemolysis:

(1) storing blood in an unregulated refrigerator, with undetected freezing

(2) using a microwave oven or other unregulated device to warm blood

(3) malfunction of a blood warmer

(4) traveling in an ambulance or helicopter during the winter


Both occurrences require a high index of suspicion, usually after the transfusion reaction workup turns up negative:

(1) A careful redraw of a new sample will usually detect a problem in specimen handling.

(2) Preinfusion hemolysis often requires exclusion of the different causes plus circumstantial evidence.

(2a) If the blood bag or infusion setup is still available then it should be examined.

(2b) If a blood warmer was used it should be tested.

(2c) All personnel involved in handling and transfusing the implicated blood product(s) should be debriefed.


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