Thank you for your question. I am sorry for your loss and know that it is normal to question yourself in these situations to see if there is something different that you could have done. I haven’t examined Paris myself so I am unable to diagnose or suggest a different course of action; however, given Paris’s age and the situation you describe, the best course of action probably was euthanasia. Fluid on the lungs is a symptom of a primary condition; the progress of the primary condition was probably a factor in the decision to euthanize. Regards Dr Callum Turner DVM
Edema is a form of swelling caused by excess fluids trapped in the tissues of your body. It is most commonly found at the ankles, feet, legs, arms and hands. Edema can be a result of a temporary condition such as during pregnancy or after an injury. Edema can also result from heart, kidney or liver disease, or it can be a side effect of a medication. Edema can also be peripheral, which means it is found in the ankles, feet, legs, arms, and hands, or it can be central, which means it is found around internal organs such as the lungs. 
Transdermal patches (adhesive patches placed on the skin) may also be used to deliver a steady dose through the skin and into the bloodstream. Testosterone-containing creams and gels that are applied daily to the skin are also available, but absorption is inefficient (roughly 10%, varying between individuals) and these treatments tend to be more expensive. Individuals who are especially physically active and/or bathe often may not be good candidates, since the medication can be washed off and may take up to six hours to be fully absorbed. There is also the risk that an intimate partner or child may come in contact with the application site and inadvertently dose himself or herself; children and women are highly sensitive to testosterone and can suffer unintended masculinization and health effects, even from small doses. Injection is the most common method used by individuals administering AAS for non-medical purposes.