As the coronavirus pandemic upended the U.S. health-care system, EmCare IAH Emergency Physicians, a Houston staffing company owned by private equity firm KKR, made a little-noticed request of the government: It applied for a $317,379 interest-free loan. KKR had for years paid lobbyists to fend off efforts to ban a practice known as surprise billing used by EmCare and other providers that has driven up the cost of health care.