Tachycardia, HR >180 bpm in cats³ and HR >150– 190 bpm for large and small dogs, respectively,⁴⁴ during anesthesia deserves special mention, because it should prompt the anesthetist to run through a list of rule-outs and not simply assume it is a response to inadequate anesthetic depth. Tachycardia can be secondary to a noxious stimulus, hypoxemia, hypercarbia, and hypovolemia. It can also occur secondary to administration of drugs such as alfaxalone, ketamine, atropine, and dopamine.