Low BP after Plastic Surgery. Consult!

My father fell from the first floor on February 22, 2017 and underwent jaw surgery (by a team of plastic surgeons ) on March 3, 2017. He lost a lot blood because of the accident. During the hospitalization, his BP was keeping a little high. Once discharged, he was asked to stay on a liquid diet for around 1 month. Later, once the wires and stitches were opened, he was asked to have soft solid food and do some mouth opening exercises. Recently, he is experiencing frequent low BP ( which varies from 50/80 or sometimes 60/90. I am concerned. Please guide us about the probable reason for the same. We consulted a local doctor (not a specialized one), he gave some neuro medicines and asked him to get EEG test done. We have stopped the medicines given by the local doctor, as after taking the medicine, my father was not able to get up from the bed. My father had also undergone C spine surgery in the Feb2016 for compression of nerves. Please advice us on the treatment and whom should we consult