Recovery from anesthesia occurs on a continuum: the patient initially responds to noxious stimuli and then to oral command, though the patient remains amnestic; motor control returns gradually; finally, in 15 to 45 min, the patient is able to converse rationally. Wakefulness requires diffuse cortical activation (arousal) elicited by afferent stimuli from the reticular formation in the brainstem. Within 15 min of admission to the postanesthesia care unit, 90% of patients regain consciousness. Delayed awakening after general anesthesia (i.e., >45-60 min after admission to the postanesthesia care unit) is secondary to a diverse number of causes and can be broadly classified as pharmacologic, metabolic, or neurologic (Box 113-1).

The anesthesia provider should systematically evaluate the patient with delayed emergence from anesthesia (Box 113-2) while simultaneously managing the patient’s preoperative comorbid conditions and medications. This includes taking into consideration the type of operation, the type and doses of anesthetic drugs, drugs administered by the surgical team, and the duration and complications of anesthesia. Importantly, delayed emergence may be associated with the patient’s inability to protect his or her airway, airway obstruction, and respiratory failure. Many of the causes of delayed emergence are overlapping and may coexist.