What Causes Nausea During Heart And Kidney Failure?

Last year a friend of mine had to go on dialysis. She stayed on it for about four months and then her doctors decided she no longer needed it and took her off. She began to be severely nauseated; she stayed this way for about four months. The doctors then determined that she was in heart and kidney failure. They said her kidney failed because her heart was not pumping enough blood to make her kidney work. Yesterday, she had a pacemaker put in. The surgery took longer than expected because she is so thin it was hard to place the device. The pacemaker is doing what it is suppose to be doing but she is still severely nauseated. Why is this?