Anesthesiology APPLIED Exam › Neuroanesthesia and neuromuscular

Delayed emergence

Neuroanesthesia and neuromuscular·~5 min read· Physician-reviewed✓ Sourced · 4

Stem

A 76-year-old woman, 54 kg, with type 2 diabetes on insulin and atrial fibrillation, has had a four-hour open colectomy under sevoflurane, fentanyl, midazolam at induction and rocuronium. The surgeon closed 30 minutes ago and the vaporizer is off. She is breathing spontaneously through the tube at 8 breaths per minute, her pupils are small, and she does not open her eyes or move to command. Her temperature is 34.8 °C.

Question

She has not woken up. How do you approach this?

Ideal answer

HeadlineNot waking 20–30 minutes after the anesthetic should have ended is a diagnostic problem. I secure airway, oxygenation, ventilation and pressure, then work drugs, metabolism, brain.

Confirm the vaporizer and every infusion off, end-tidal agent near zero,¹ because ongoing drug delivery is the quickest cause to exclude.
Quantitative train-of-four, and reverse, because residual block looks like coma in a paralyzed patient.
Pinpoint pupils: naloxone 40 mcg every 2 minutes, looking elsewhere after about 400 mcg; flumazenil 0.2 mg each minute to 1 mg, because she had midazolam.¹
Glucose and a gas with sodium and calcium; warm her, because hypothermia, hypercarbia, hyponatremia and hypoglycemia all produce this picture.
Drug and metabolic causes excluded, or a focal deficit: stroke, bleed or seizure until proven otherwise; with her atrial fibrillation, neurology and CT with the airway secured.

Breaking down the answer

An order, not a list — the test is organization: a usable order with a treatment on each branch, and judgment about when a sleepy patient becomes a neurologic emergency. Formal definitions allow up to 60–90 minutes even after a long anesthetic.¹
Residual anesthetic first — usually a relative overdose in an elderly, hypothermic, renal or hepatic patient: volatile still above 0.2 MAC, or an opioid given late. I support, set a 30-minute limit, and work the differential while I wait.
Antagonist hazards — miosis with slow, deep breathing is opioid; abrupt naloxone brings hypertension, arrhythmias, pulmonary edema: 2–3 minute increments;² no flumazenil in benzodiazepine dependence or cyclic antidepressant overdose (seizures).³ Physostigmine up to 2 mg IV, slowly, reverses central anticholinergic syndrome from scopolamine and antihistamines.⁴
Twitch monitor before "unconscious" — a train-of-four of zero is awake and terrified. Pseudocholinesterase deficiency after succinylcholine looks the same: I sedate and ventilate for the hours it takes.¹
Metabolic causes — hypoglycemia from insulin or an insulinoma, hyponatremia below about 120 mEq/L from TURP irrigant or SIADH: reversible within minutes if found, lethal if missed. Hypercarbia above 60–70 mmHg is narcosis in its own right.¹
Temperature below 33 °C — hypothermia slows drug clearance and depresses consciousness directly; I warm actively before I interpret the neurologic exam.
CT now — focal signs or risk: carotid, cardiac, neurosurgical and prolonged hypotensive cases, new asymmetry; antagonists do not delay it. Surgical causes: carotid cross-clamp, air embolism in a sitting case, a subdural after a dural tear. Non-convulsive status: EEG if CT is clean.

Follow-up question

You give naloxone and she still does not wake. Now the right pupil is 6 mm and unreactive. What do you do?

Follow-up answer

HeadlineA surgical emergency until proven otherwise: intracranial hemorrhage, embolic stroke or herniation from edema, and I say so to the room.

I reintubate if the airway is not secure, ventilate to a PaCO2 of 35 mmHg, raise the head 30 degrees, give mannitol 0.5–1 g/kg or 3% saline, keep the mean pressure adequate for cerebral perfusion, and go straight to CT with a neurosurgeon notified. I review the record and ask the surgeon about hypotension or an embolus from her atrial fibrillation. If instead the glucose comes back at 32 mg/dL: 25 g of dextrose, waking within minutes, and why: a missed insulin dose adjustment, an islet-cell tumor, liver failure, or sepsis.

Pitfalls that cost points

Giving a full 0.4 mg ampule of naloxone to a patient with a fresh sternotomy.
Waiting an hour for an elderly patient to "metabolize" before checking a twitch monitor or a glucose.
Calling a patient who opens eyes to pain and withdraws simply "slow" when there is a new hemiparesis.

Rapid-fire

Q: Why do elderly patients emerge late even at normal doses? A: MAC falls about 6% per decade after 40, drug clearance falls, and cerebral reserve is lower, so the same dose is a relative overdose.

Q: Why does hyponatremia cause coma? A: Water follows the osmotic gradient into neurons; brain swelling and raised intracranial pressure depress consciousness and provoke seizures.

Q: What is the risk of flumazenil? A: Seizures in benzodiazepine-dependent patients and resedation after about an hour, because its terminal half-life of 40–80 minutes is shorter than that of midazolam.³

Q: When do you stop waiting? A: At 30 minutes with the drug causes reversed and the metabolic screen normal, or at once with focal findings.

Numbers to know

Item	Value
Time to call it delayed	Formally 60–90 min;¹ I start the workup at 20–30 min
Naloxone	40 mcg IV every 2 min; reconsider after 400 mcg¹
Flumazenil	0.2 mg IV, repeat every minute to 1 mg³
Physostigmine	0.04 mg/kg IV, max 2 mg per dose, at about 1 mg/min⁴
Hypoglycemia treatment	25 g dextrose (50 mL of D50)
Hyponatremia symptomatic	Sodium below ~120 mEq/L; 3% saline 100 mL bolus

Sources

1.Delayed Emergence · OpenAnesthesia (IARS) · openanesthesia.org
2.Naloxone hydrochloride injection prescribing information · FDA / DailyMed · dailymed.nlm.nih.gov
3.Flumazenil injection prescribing information · FDA / DailyMed · dailymed.nlm.nih.gov
4.ANTICHOLIUM (physostigmine salicylate) injection labeling · FDA / DailyMed · dailymed.nlm.nih.govImported product labeling; postoperative awakening disorders 0.04 mg/kg slowly (about 1 mg/min), maximum single dose 2 mg.

Facts on this page were checked against these sources on Oct 14, 2026. Guidelines change; confirm doses against current institutional protocols.