Diabetic complications

My 58 year old diabetic brother received an LVAD about 4 months ago and is having a problem getting through physical and occupational rehabilitation because of unstable, high blood sugar levels. He has lost close to 50 of his original 172 lb body weight. He had a stroke about 6 weeks ago and doctors haven't been able to control blood sugar spikes, in rehab facilities. He has been pulled back to the hospital from rehab twice and is now in a new rehab facility. He is on Coumadin, baby aspirin and insulin shots for short term and long acting use. He may be dehydrated. This is a man who worked 7 days a week for the last 35 years and now he can barely get out of bed. Could there be a drug interaction issue being overlooked by the medical professionals? His siblings and 82 year old mother are at wits end.