21 g needle vs 23 g butterfly

Nurses General Nursing

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I work in geriatrics and I have noticed that I get a higher rate of hemolysis and false positive hyperkalemia with a 21 g needle versus a 23 g butterfly. I tried not to tie the tourniquet too tightly. I've even tried drawing without a tourniquet. Same results. What am I doing wrong? Does anyone have any tips to prevent this from happening?

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Specializes in Vascular Access.

Logically it does not compute, I agree.. but I'd have to ask you: How long was the tourniquet on? Did you make sure the alcohol was dry, before cannulating? Did you erroneously shake the red top after drawing the specimen? Did the specimen get overheated? Was the blood tube expired? How was it transported? Now, not all of these will create a situation where K elevates, but proper procedure and care is essential for good outcomes.

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Logically it does not compute, I agree.. but I'd have to ask you: How long was the tourniquet on? Did you make sure the alcohol was dry, before cannulating? Did you erroneously shake the red top after drawing the specimen? Did the specimen get overheated? Was the blood tube expired? How was it transported? Now, not all of these will create a situation where K elevates, but proper procedure and care is essential for good outcomes.

Thank you for your response. I think that I did in fact shake the red tube. I thought this was required :( None of the other things you suggested happened. Thanks again.

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Specializes in Pediatrics, Emergency, Trauma.
Thank you for your response. I think that I did in fact shake the red tube. I thought this was required :( None of the other things you suggested happened. Thanks again.

You can do a gentle inversion of the tubes:

BD Vacutainer® LabNotes - The Evolution of Evacuated Blood Collection Tubes

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Specializes in Vascular Access.

Gently invert the tubes with anticoagulants in them (purple top, blue top) Shaking a red top can rupture cells.

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Specializes in ICU, CVICU, E.R..

You're not supposed to shake the vacutainers. Just gently invert them back and forth.

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Specializes in Med-Surg, Emergency, CEN.

I agree with the above posters. Blood work is like a baby. Never shake or drop the blood work.

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