Who Pays for MED A items?

Here's the issue: we accepted a woman status post pneumonia for short term rehab. AFTER she was admitted we found she had a non healing wound. Out she goes and comes back with orders for a wound vac. So we paid for it. But now, she has to go to the hospital for vascular studies and most likely surgery. If she stays on census (with a paid bed hold) do WE have to pay for the surgery etc? We are constantly getting bills for followup MD visits for people with new hips and knees. In my old facilities we didn't pay for those but for some reason, this facility is convinced those bills are our responsibility. Anyone know?? Talino??