Final answer:
The next event likely to occur after monitors are placed on the patient in the operating room is the placement of the breathing circuit and mask for preoxygenation before inducing anesthesia.
Step-by-step explanation:
If an anesthesiologist mentions that they are "putting monitors on," the likely next event in the operating room is D) Placement of the breathing circuit and mask for preoxygenation. This step occurs before the induction of anesthesia and is critical for ensuring that the patient has adequate oxygen in their system before the administration of anesthesia starts, which could depress respiration. Additionally, team members such as the nurse and an anesthesiology professional will orally confirm several patient safety checks, such as the patient's identity, the surgical site and procedure, informed consent, and proper functioning of the pulse oximeter. It is also important to ensure that all necessary equipment, including airway management tools, are available and that any known allergies or critical concerns are communicated among the team. Preoxygenation is vital since the drugs used for anesthesia relax the body's muscles, potentially affecting the muscles necessary for breathing and putting normal homeostatic control of respiration on hold, ultimately necessitating control by the anesthesiologist.