My Dad Is At Dialysis 3 Days A Week And

My Dad is at dialysis 3 days a week and every day, especially at night, he is troubled with mucus or phlegm causing him to gag and often puke up his meal which is always high in protein. He is on many other meds for heart, cholesterol, Coumadin for a stroke he had at 35 and another at 36, and specific meds to help him with jitters and RLS... can you explain?