What is the ruling on one who was negligent in sterilizing a cannula for a patient, which led to the possibility of her being harmed or dying, and what must she do?

The doctor and nurse must take care of the patient, fulfilling their trust and responsibility, as many patients' conditions worsen due to medical negligence. If a doctor causes damage or death, they are liable.

It is not clear whether the patient died or was harmed as a result of your work, so there is nothing upon you. You should not burden yourself with thinking about it, as bacterial infection is merely a possibility, not a strong one, and it is likely that she was safe from it, and her death from it is very unlikely.

What you should do now: 1. Turn away from your intrusive thoughts regarding this case. The default is that you are innocent, and as long as you have not confirmed actual harm befell the patient due to your negligence, dismiss this matter entirely from your mind. 2. Hasten to treat your obsessive-compulsive disorder by seeking a trustworthy, specialized female or male doctor, going to them with one of your mahrams, and beginning medical treatment for this illness.