The only trouble with sitting with feet up/elevated is that all you do is send the fluid to another part of the body! If his breathing is ok , he may as well sit with his feet down , at least the fluid will stay in his lower regions and not make its way to his torso. If he finds his breathing gets really bad , dont wait until tomorrow ,contact the renal unit today. As everyone has said, really really cut back on fluids today. If he can breathe ok today then tell the unit he is overloaded and they will pull the fluid off him. Its also possible if he hasnt been drinking loads that his dry weight may need adjusting ? Or if he is being a good boy! then maybe he needs a different program on the machine?