Jim Kuhn can be kept alive by a $90,000 heart pump, but his doctors and family say hospitals won't take his case because he has run out of Medicare days. For the past seven months, Kuhn, 53, has been in intensive care in a West Palm Beach hospital with a failing heart. But a combination of little-known Medicare limitations, hospital requirements and, most recently, uncertainty over Kuhn's ability to endure the surgery have amounted to a life-or-death situation for the former truck driver. As Kuhn waits in a hospital bed, his family hopes his condition will stabilize while they and senators, including Miami's Marco Rubio, search for a way to get him the help he needs.