Signs of Emergence: GA

From John Snow to Francis Plomey, anesthesiologists have relied upon a series of physical exams to assess emergence from general anesthesia. In 1937, Arthur Guedel provided the detailed system of anesthesia stages still used today in assessing anesthetic depth throughout emergence. Of note, Guedel’s classification was designed to assess patients undergoing inhalational anesthesia with ether already premedicated with atropine and morphine. Guedel’s classifications are as follows:

1. Stage I: from initiation of GA induction through loss of consciousness
2. Stage II: from loss of consciousness to onset of autonomic breathing. Eyelash reflex disappear but other reflexes (coughing, vomiting, struggling) will persist. Respirations can be irregular with breath holding. Also known as the stage of excitement or delirium.
3. Stage III: from onset of automatic respiration to complete respiratory paralysis and apnea. Early, eyelid reflexes are lost, swallowing reflexes disappear, and marked eyeball movements occur without conjunctival reflex. Soon thereafter, eyeball movements cease and intercostal muscle paralysis occurs. Laryngeal reflexes are lost, corneal reflexes disappear, secretion of tears increases, automatic and regular respiration occur, and deep breathing as a response to skin stimulation disappears. Lastly, progressive intercostal paralysis, pupil dilation, and light reflex is abolished, progressing to complete intercostal paralysis to diaphragmatic paralysis.
4. Stage IV: a state of medullary depression featuring cardiovascular and respiratory depression unto respiratory arrest and vasomotor collapse (also recognized as anesthetic overdose-caused medullary paralysis.

Emergence from GA involves a passive process with gradual return of consciousness following withdrawal and discontinuation of anesthetic agents following surgery. Signs of emergence from GA depend on the drug(s) administered, their sites of action, their potency, and their pharmacokinetics as well as the patient’s physiological characteristics and the type/duration of surgery. Generally, recovery from GA and paralysis involves assessing the following physiologic and behavioral signs.

• Return of spontaneous respirations. Usually the first clinical sign that that peripheral neuromuscular blockade has worn off or been reversed. Assessing neuromuscular reversal frequently involves neuromonitoring or twitch monitoring as well.
• Heart rate and blood pressure typically increase with emergence.
• Salivation and tearing begin.
• Non-localized responses to painful stimuli
• As skeletal muscle returns, the patient begins grimacing, swallowing, gagging, and coughing while making defensive movements, such as reaching for their airway device.
• At this juncture, the patient has demonstrated sufficient return of brainstem reflexes to maintain spontaneous respirations and airway protection, even without responding to oral commands or spontaneous eye opening.
• Before discharge from postanesthesia care unit, patient should be able to answer simple questions and convey any discomfort (pain, nausea, etc.)