Delayed Emergence

Definition

There is no universally accepted definition of delayed emergence/recovery after anesthesia. In clinical practice, it is thought to be the failure of the patient to regain the expected level of consciousness within 20 to 30 minutes of the end of anesthetic administration. It may also include abnormal emergence such as severe agitation. The time it takes for full consciousness to recover after anesthesia is influenced by patient factors, anesthetic drugs used, duration of surgery, and interaction between various medications used during the perioperative period. In many patients, it is probably multifactorial with a predominant contribution from one factor.

Common causes of delayed recovery include the following:

• Interactions and potentiation of drugs between preoperative medications and anesthetic drugs

• Absolute or relative overdose of sedative and anesthetic drugs

• Concomitant administration of benzodiazepines and opioids

• Sensitivity of patients to drugs (e.g., opioid-naive patients)

Uncommon causes include the following:

• Metabolic disorders

• Electrolyte disorders

• Postoperative delirium

• Sepsis

Rare causes include the following:

• Serotonin syndrome

• Central anticholinergic syndrome

• Psychiatric disorders

• Stroke and other neurologic complications

Recognition

Recognition of delayed emergence is usually made by simple neurologic assessments such as AVPU ( a lert, responds only to v erbal stimuli, responds only to p ain, u nresponsive) or the GCS score. It is a diagnosis of exclusion; hence the anesthesiologist must promptly evaluate these patients to diagnose and rule out airway obstruction, respiratory failure, and hypoglycemia to differentiate delayed emergence from life-threatening problems that may falsely manifest as delayed emergence.

The patient should be evaluated immediately with assessment of vital signs after an airway, breathing, circulation (ABC) approach (especially the rate and the character of spontaneous breathing and oxygen saturation) and a physical examination. ABC should be reevaluated throughout the course of delayed emergence. An aid to assessing and managing an unconscious patient is outlined in Fig. 137.1 .

Risk Assessment

In modern anesthesia with short-acting anesthetic drugs, a majority of the patients recover very quickly after surgery, and most patients are ready to be discharged from the PACU within the first hour. Although delayed emergence has many causes, its predictability and the rate at which it will occur have not been studied well so far. Most case reports are purely anecdotal, and thus no incidence rate has been determined. Though incidence due to long-acting anesthetic drugs may be coming down, actual incidence of delayed recovery may not be, because of patients with complex medical problems on multiple medications having major operations. The cause may also be multifactorial, such as an elderly patient with dementia or renal impairment who has a lengthy procedure under GA. Pharmacologic causes are more likely, especially in the first hour. After the first hour, metabolic, neurologic, and other rare causes are more likely.

Risk factors for delayed recovery include the following:

• Elderly

• Patients with dementia

• Preexisting cognitive or psychiatric disorders

• Patients with hepatic and renal impairment

• Long operation and anesthesia duration

• Longer-acting anesthetic medications

• Absolute and relative overdose of anesthetic drugs

• Patients on sedative and antipsychotic medications

• Intoxicated patients having emergency surgery

• Patients physically exhausted before surgery

Implications

A majority of patients with delayed emergence recover well. Provided life-threatening problems are rapidly diagnosed and treated, close observation and monitoring will be enough for most patients. Some patients may need unplanned inpatient, high-dependency/intensive care management. Very rarely patients may require surgical intervention, such as evacuation of subdural hematoma, which may initially present as delayed emergence.