PACU hypoxemia and post-extubation stridor

Airway·~5 min read· Physician-reviewed✓ Sourced · 12

Stem

A 49-year-old man, 112 kg, with obstructive sleep apnea on home CPAP, has had a 4-hour prone L4–S1 fusion. He received rocuronium, with the last dose 50 minutes before closure, and neostigmine 3.5 mg when two twitches were present. He had hydromorphone 2 mg. Fifteen minutes into PACU he is drowsy and snoring, with SpO2 86% on 4 L nasal cannula, respiratory rate 8, blood pressure 152/90 and heart rate 96.

Question

What is your differential, and how will you manage him?

Ideal answer

HeadlineHe is hypoventilating and obstructing, from residual block, opioid and sleep apnea together; I oxygenate first, then treat each cause while I look for shunt.

Call for help; sit up, jaw thrust, 100% by mask, and I assist with bag-mask if he is not better within a minute.
Quantitative train-of-four now, because neostigmine given at two twitches leaves residual weakness; below a ratio of 0.9 I give sugammadex 2 mg/kg.¹^,2
Naloxone 0.1 mg every 2–3 minutes to effect, so he breathes without pain or hypertension.³
His own CPAP on, because his pharynx collapses again when he falls back asleep.
Auscultate, blood gas, chest ultrasound or film, because hypoxemia persisting once ventilation is fixed is shunt or V/Q mismatch.

Watch for: capnography, respiratory rate and a rising PaCO2; supplemental oxygen hides hypoventilation from the oximeter.

Breaking down the answer

Sorting the differential — hypoventilation (drugs, weakness, obstruction) raises PaCO2 and corrects with ventilation; shunt or V/Q mismatch (atelectasis, aspiration, pulmonary edema, bronchospasm, pneumothorax, embolism) does not; true shunt persists on 100%. Changes if: normal PaCO2, then imaging leads.
Residual block — clinical assessment alone is not recommended; fade cannot be felt until the ratio is about 0.4.¹ Neostigmine suits only minimal block, ratio 0.4 to below 0.9; deeper than that, sugammadex.¹ Changes if: ratio already 0.9 or more.
Naloxone's limits — some opioids outlast it, so he stays under continued surveillance after a good response.³ Changes if: renarcotization, which earns an infusion and a monitored bed, not discharge.
Laryngospasm — paradoxical breathing, no air movement: CPAP with 100% oxygen, jaw thrust and Larson's maneuver,⁴ then propofol 0.5–0.8 mg/kg,⁵ then succinylcholine 0.1–0.5 mg/kg IV, 1–2 mg/kg and intubate if severe.⁶
Negative-pressure pulmonary edema — obstructed inspiration generates −50 to −100 cmH2O;⁷ pink frothy sputum minutes later. I give oxygen and CPAP or PEEP, limit fluid, use a diuretic selectively; on imaging it usually resolves in 12–24 hours.⁷
The prone case — four hours face down plus fluids swells the tongue, pharynx and larynx; I look at his face and listen at the neck before I blame the lungs.

Follow-up question

With CPAP and sugammadex his saturation reaches 93%. Twenty minutes later he develops high-pitched inspiratory stridor and suprasternal retractions, his face and tongue are visibly swollen, and the SpO2 falls to 88% on a face mask. What do you do now?

Follow-up answer

HeadlineThis is upper-airway edema threatening his airway; I call for help, the difficult-airway cart, and ENT or a surgical-airway-capable surgeon.

Rash, wheeze or hypotension after sugammadex means anaphylaxis:² epinephrine 50 mcg IV, repeated to effect, or 0.5 mg IM without IV access.⁸ Otherwise it is laryngeal edema: upright, humidified 100% oxygen, racemic epinephrine 0.5 mL of 2.25% in 3 mL saline,⁹^,10 and dexamethasone 5 mg IV.¹¹ Heliox only buys time and must not delay intubation.¹¹ If he tires, I reintubate with a video laryngoscope, a smaller tube and front-of-neck access ready; if he improves, he is monitored at least 4 hours.⁹

Pitfalls that cost points

Calling stridor "bronchospasm" and giving albuterol: inspiratory noise at the neck is an extrathoracic, upper-airway problem.⁹
Running 70:30 heliox in a desaturating patient: it caps the inspired oxygen at 30%.
Discharging to the ward an hour after racemic epinephrine, when its effect is already fading.⁹

Rapid-fire

Q: Why does a little edema cause so much obstruction? A: Turbulent resistance rises with the fifth power of the radius; in an infant, 1 mm of subglottic edema cuts cross-sectional area by about 75%.⁹

Q: How long does racemic epinephrine last? A: At least an hour, gone by two, so after anesthesia I observe at least four hours;⁹ croup guidance discharges after 2–4 symptom-free hours.¹²

Q: When do steroids prevent post-extubation laryngeal edema? A: IV corticosteroids started 12–24 hours before extubation, in multiple doses, after prolonged intubation.¹¹

Q: What sugammadex dose for deep block? A: 4 mg/kg at 1–2 post-tetanic counts with no train-of-four response.²

Q: Succinylcholine for laryngospasm with no IV? A: 3–4 mg/kg intramuscularly.⁴

Numbers to know

Item	Value
TOF ratio before extubation	≥0.9¹
Sugammadex	2 mg/kg at T2; 4 mg/kg at 1–2 PTC²
Naloxone, postoperative	0.1–0.2 mg IV every 2–3 min³
Racemic epinephrine 2.25%	0.05 mL/kg, max 0.5 mL (adult 0.5 mL), in 3 mL saline;⁹^,10 ED croup uses a fixed 0.5 mL at any age¹²
Post-nebulizer observation	≥4 h⁹
NPPE inspiratory pressure	−50 to −100 cmH2O⁷

Sources

1.New Practice Guidelines for Neuromuscular Blockade · APSF Newsletter (summary of the 2023 ASA practice guidelines), 2023 · apsf.orgQuantitative monitoring over clinical or qualitative assessment; TOF ratio >=0.9 before extubation; sugammadex for deep to shallow block, neostigmine only at minimal block (TOF ratio 0.4 to <0.9).
2.BRIDION (sugammadex) injection prescribing information · DailyMed (FDA labeling) · dailymed.nlm.nih.gov
3.Naloxone hydrochloride injection: dosage and administration · Pfizer Medical Information (FDA labeling) · pfizermedical.com
4.Laryngospasm · OpenAnesthesia (IARS) · openanesthesia.org
5.Pediatric laryngospasm (Hampson-Evans, Morgan, Farrar; consensus management algorithm) · Paediatric Anaesthesia, 2008 · mcgill.caPaediatr Anaesth 2008;18:303-7. Succinylcholine 1-2 mg/kg IV is the gold standard, some advise 0.1 mg/kg; propofol 0.5-0.8 mg/kg; atropine 0.02 mg/kg; IM succinylcholine 4 mg/kg.
6.Laryngospasm · Life in the Fast Lane (LITFL) · litfl.comSuxamethonium 0.1-0.5 mg/kg IV may suffice; full dose 1-2 mg/kg IV and intubate in severe laryngospasm; 3-4 mg/kg IM without IV access.
7.Negative pressure pulmonary edema (Review) · Experimental and Therapeutic Medicine (Ma et al.), 2023 · ebi.ac.uk
8.Peri-operative anaphylaxis: for anaesthetists/intensivists · Resuscitation Council UK / Association of Anaesthetists, 2024 · resus.org.ukAdult and child over 12 years: adrenaline 50 micrograms IV, repeated; no IV access: 10 micrograms/kg IM, max 500 micrograms; infusion if poor response.
9.Postextubation Stridor · OpenAnesthesia (IARS), 2023 · openanesthesia.orgRacemic epinephrine 0.05 mL/kg (max 0.5 mL) of 2.25% diluted to 3 mL; effect about 1 h, gone by 2 h; observation at least 4 h; edema and radius physics.
10.Racemic epinephrine · WikEM · wikem.orgAdult post-extubation stridor: 0.5 mL of 2.25% diluted in 3 mL normal saline by jet nebulizer, repeatable every 20 minutes.
11.Postextubation laryngeal edema and stridor resulting in respiratory failure in critically ill adult patients: updated review · Critical Care (Pluijms et al.), 2015 · ebi.ac.ukSteroid plus nebulized epinephrine as treatment; suggested dexamethasone 5 mg or methylprednisolone 20-40 mg; heliox and NIV must not delay reintubation; prophylaxis 12-24 h before extubation.
12.Acute management of croup in the emergency department · Canadian Paediatric Society (Ortiz-Alvarez, Acute Care Committee), 2026 · cps.caPosted 2017, updated March 2026. Effect within 10-30 min, sustained at least 1 h, gone after 2 h; fixed 0.5 mL racemic or 5 mL 1:1000 L-epinephrine at any age or weight; discharge if croup does not recur 2-4 h after treatment (with dexamethasone).

Facts on this page were checked against these sources on Oct 23, 2026. Guidelines change; confirm doses against current institutional protocols.