Hello, Thanks for posting your query on Healthcare Magic... * Brief Answer: congestion in intestinal mucosa can alter drug absorbtion and so need to shift to injection instead. *Explanation: My opinion is that in your relative case congestive heart failure is a result of ischemic heart. After bypass surgery , post operative care is crucial. Shifting to oral medications is a good sign but some times , especially with lasix ,response may not be satisfying as for drug bioavailability. Sometimes we as doctors shift our patient from oral to injections to get a good result and that is only temporary I suggest my patients the following   : less salt and fluid restriction. Ask about symptoms and signs of heart failure. The information provided by you is not sufficient to provide a good opinion. If someone comes to me with this condition I would ask them about your relative vitals signs and nutritional state ,also if other comorbidities present. *Conclusion: I suggest you follow up with doctors and see improvement in body weight and urine output. If you have any further questions I will be happy to help, If not, you can close the discussion and rate the answer. Wish your relative good health.