The ambulance driver states that he has to go through the Sumner Tunnel to get to Logan Airport. Since 1961, the tunnel going to Logan has been the Callahan tunnel. The Sumner tunnel has been outbound from the airport since 1962.
The MG-B that Dr. Wheeler drives in the opening scene with a tan interior and a black plastic honeycomb grille switches to an earlier model with a black interior and an all chrome grille (noticeable in the scene where the car will not start). When Dr. Wheeler visits the Jefferson Institute, it has switched back to the MG-B with the tan interior and black grille.
When Dr. Harris completes an appendectomy, the anesthesiologist reaches for the patient's endotracheal tube, as Dr Harris begins to turn away. When he completes the turn, the anesthesiologist is seen removing a face mask from the patient. There was no time for the anesthesiologist to remove the tube and replace it with the mask.
When Dr. Wheeler discovers the carbon monoxide line leading to OR 8, it might seem as if she is looking down into the operating room, but she is actually above the hall looking at the door into the OR, as the nameplate beside the door proves. An operating room would never feature a drop ceiling.
Drs. Mark Bellows (Michael Douglas) and Susan Wheeler (Geneviève Bujold) are seen on the DVD cover/movie poster climbing a ladder together, presumably the one that leads to the crawlspace above OR8. Each one of the characters only climbed a ladder once and those were on separate occasions.
In the scene toward the end, where Dr. Susan Wheeler discovers Tom Selleck's body after it has been "harvested" it is Tom himself laying on the table. Later shots show that a dummy with a bad wig has been substituted for the actor.
Right after the death of Sean Murphy in Operating Room #8, Dr. Susan Wheeler (Genevieve Bujold) adds his name to a handwritten list she has. She includes what might have been his patient number, but it doesn't follow the sequencing of the patients who died before him, nor would she have had time to even find out what that number was because she had just become aware of his death.