Congestive heart failure (CHF) is the inability of the heart to pump blood and meet the body’s needs. Therefore, blood (and fluid) back up in the venous system causing venous congestion which produces many of the symptoms of CHF including shortness of breath and coughing (as fluid collects in the lungs), swelling of the feet (venous congestion), swelling of the abdomen (venous congestion), and tiredness/weakness/malaise (failure to provide adequate circulation).
Lasix (furosemide) is a diuretic (water pill) that increases the amount of free water secretion by the kidneys by preventing salt from being re-absorbed back into the body. Lasix is indicated to treat hypertension, general edema, as well as pulmonary edema.
To answer your question, it is certainly acceptable to still have residual lower extremity edema as long as the Lasix helps keep the lungs clear. The main goal of using Lasix for treatment of CHF is to prevent any life threatening processes such as pulmonary edema (fluid in the lungs). Treatment patients with CHF is a delicate balance as doctors aim to keep the patient functional and their lungs clear of fluid without over diuresing (over excretion of water) the patient and causing life threatening hypotension and electrolyte abnormalities. Therefore, if the 10 mg of Lasix is adequate in keeping the lungs clear and there is only some residual swelling of the feet, then increasing the dose of Lasix might be an unnecessary risk.