A 77 year-old male is being admitted to the hospital for a coronary bypass. He has been taking Atenolol 100mg PO QD. His anesthetic regimen consisted of: (Propofol induction, Fentanyl IV infusion, Vecuronium muscle relaxant) During the procedure, his HR dropped to 38 and BP to 80/60. It was treated and reversed with atropine and epinephrine. What most likely contributed to this problem?