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A 33-year-old member asked:

During dialysis why does the subclavian catheter have darker blood than in patients with a fistula?

2 doctor answers5 doctors weighed in
Dr. James Cain
Nephrology and Dialysis 36 years experience
Venous blood: A subclavian catheter has only venous, deoxygenated blood returning from the body. A fistula contains oxygenated arterial blood coming from the heart. This is the reason for the bright red blood seen in fistulas.
Dr. Eric Chen
Radiology 11 years experience
Fistula vs catheter: Dialysis catheters are placed in veins, and therefore use deoxygenated (dark) blood. Dialysis fistula is a connection between an artery and a vein. The blood within a fistula is oxygenated, and therefore more red.

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A 48-year-old member asked:

For a dialysis, why is the subclavian catheter has darker blood rather than in patient with fistula?

1 doctor answer2 doctors weighed in
Dr. Jack Rubin
Nephrology and Dialysis 48 years experience
Catheter vs fistula: An a-v fistula (avf) is a connection between an artery and a vein, that's why its called an a, for artery, v, for vein, fistula. Arterial blood has more oxygen, making it redder, than venous blood. A subclavian catheter has both blood tubes in the vein, where there is less oxygenated blood, as it does not have any arterial inflow. That's why it has darker blood than an avf.

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Last updated Sep 29, 2019

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