45 y/o male s/p tracheostomy three days ago presents with massive bleeding of bright red blood from about his trach. A tracheo-arterial fistula is suspected. What is your next move?

DON'T remove the trach; then, hyperinflate the cuff to tamponade the bleeding.   If the trach is removed the patient will aspirate blood and asphyxiate.

Fortunately, tracheo-arterial fistula after trach is a rare complication but can occur from erosion into the brachiocephalic trunk, especially with placement of a low lying trach below the third tracheal ring. 

Pressure necrosis from a trach tube can erode into the brachiocephalic artery which runs anterior to the trachea.

Sources

Praveen, CV.  "A rare case of fatal haemorrhage after tracheostomy"  Ann R Coll Surg Engl.  2007.

Image source: http://www.hawaii.edu/medicine/pediatrics/pemxray/v6c19.html