According to the Hanafi school, blood breaks wudu when it exits the body and flows beyond the place from which it emerged. Merely seeing blood inside a vein, under the skin, or within medical tubing connected to a vein does not automatically invalidate wudu.

In the situation you described, the blood is appearing within the cannula tubing and remains part of a closed medical system. It is not flowing onto the skin or beyond the point of exit from the body in the manner discussed by the classical Hanafi jurists regarding bleeding wounds.

Therefore, the stronger Hanafi analysis is that the appearance of blood inside the cannula tubing alone does not invalidate wudu.

Even if one were to assume that a particular occurrence might affect wudu, Islamic law does not require a person in your condition to continuously inspect and monitor medical equipment throughout every prayer time. The principle is that certainty is not removed by doubt.

If you have wudu, then you remain upon wudu unless you become reasonably certain that something occurred which invalidates it. Merely worrying that blood may have appeared in the tubing at some point is not sufficient to invalidate your purification.

Furthermore, you should not delay prayers to the end of their time out of excessive caution. Hospital patients are among those for whom the Sharīʿah intends ease, not hardship.

My practical advice would be:

Make wudu when you are able.
Pray at the beginning or middle of the prayer time as normal.
Do not repeatedly inspect the cannula tubing.
Do not treat every possibility or suspicion as a nullifier of wudu.
Continue praying based on the certainty of your purification.
As for the status of a maʿdhūr (excused person), there is no need to enter into those rulings unless it becomes established that something is actually and repeatedly invalidating your wudu throughout the prayer times. From what you described, this does not appear necessary.

Indeed, what concerns me more from your question is the burden of uncertainty and caution that is causing you to delay your prayers and worry excessively. The jurists repeatedly mention that hardship does not create additional obligations upon a person. Allah says:

“Allah intends for you ease and does not intend for you hardship.” (Al-Baqarah 2:185)

Accordingly, you should consider yourself in a state of valid wudu unless you know with reasonable certainty that a recognized nullifier has occurred. The occasional appearance of blood within the cannula tubing itself should not prevent you from praying calmly and on time.