Obstructive sleep apnea

Airway·~4 min read· Physician-reviewed✓ Sourced · 4

Stem

A 57-year-old man, 118 kg, BMI 39, neck circumference 45 cm, is scheduled for elective total knee arthroplasty. He has treated hypertension, his wife says he snores loudly and stops breathing at night, and he falls asleep watching television. He has never had a sleep study. Room-air SpO2 is 95%, and his serum bicarbonate is 26 mmol/L.

Question

How do you assess his sleep apnea risk, and how does it change your anesthetic plan?

Ideal answer

HeadlineSTOP-Bang 8 of 8: very likely untreated moderate-to-severe sleep apnea.¹ I plan around it rather than cancel: regional, light sedation, monitored afterward.

No delay for a sleep study, because that is for uncontrolled systemic disease such as hypoventilation, severe pulmonary hypertension or resting hypoxemia;² his room-air saturation and normal bicarbonate argue against hypoventilation. Sleep referral afterward.
Spinal, adductor canal block, multimodal analgesia, because regional anesthesia is preferable to general when it fits the operation, and it spares opioids.³
Light sedation, no benzodiazepines, because propofol sedation and IV benzodiazepines both raise his risk of airway events.³
If general: difficult mask and difficult intubation assumed, ramped, well preoxygenated, a train-of-four ratio of at least 0.9 confirmed, extubated awake and semi-upright.⁴
Afterward: continuous oximetry, head-up, opioid-sparing analgesia, monitored bed, rather than an unmonitored ward.

Breaking down the answer

Say the number — STOP-Bang is the most validated screening tool in surgical patients; 0 to 2 makes moderate-to-severe OSA unlikely, 5 to 8 means a high probability.² ¹
Do not cancel by reflex — SASM finds insufficient evidence to cancel or delay surgery for a sleep study and PAP initiation unless there is significant or uncontrolled systemic disease; this shows judgment rather than risk aversion.²
Use bicarbonate to sharpen the screen — adding HCO3 of at least 28 mmol/L to a score of 3 or more raises specificity for moderate-to-severe OSA from 30% to 82%; it also hints at hypoventilation.¹
Why opioids last — patients with OSA are at greater risk of respiratory events from opioids, which is why SASM favors regional when it fits.³
Prepare the airway — known or suspected OSA is an independent risk factor for difficult intubation, difficult mask ventilation, or both.³
Monitoring is the safety net — PAP therapy is not an alternative to appropriate monitoring. Changes if: he already used CPAP; he brings it and uses it while asleep in hospital.²

Follow-up question

The spinal wears off in PACU and he receives two doses of IV hydromorphone. Asleep, he now has repeated apneas with desaturation to 82%, and the nurse wants to send him to the floor once he is awake. What do you do?

Follow-up answer

HeadlineRecurrent obstructive apnea worsened by opioids in presumed severe OSA; not ready for an unmonitored bed. I tell the nurse and surgeon he stays monitored.

I wake and reposition him head-up or lateral, give oxygen, and start CPAP from PACU or respiratory therapy. If he is hard to rouse or hypoventilating, I titrate small doses of naloxone rather than a full reversal dose, so I do not unmask severe knee pain. Analgesia switches to scheduled acetaminophen, an NSAID if his kidneys allow, and a continuous adductor canal catheter. I reassess saturation and arousal off stimulation; he goes to a step-down bed with continuous pulse oximetry overnight.

Pitfalls that cost points

Extubating supine with qualitative twitch monitoring only.
Saying CPAP replaces monitoring.

Rapid-fire

Q: What does STOP-Bang stand for? A: Snoring, tiredness, observed apnea, high blood pressure, BMI over 35, age over 50, neck over 40 cm, and male sex.

Q: What does a score of 4 tell you? A: It has a sensitivity of 88% for severe OSA; raising the cutoff to 6 increases specificity at lower sensitivity.²

Q: Who needs a preoperative specialist evaluation? A: Patients with OSA who are nonadherent to PAP and have uncontrolled hypoventilation, severe pulmonary hypertension or resting hypoxemia.²

Q: Which reversal agent fits deep rocuronium block in this patient? A: Sugammadex, recommended over neostigmine at deep, moderate and shallow depths.⁴

Numbers to know

Item	Value
STOP-Bang low risk	0–2¹
STOP-Bang high risk	5–8¹
Bicarbonate that sharpens the screen	≥28 mmol/L with score ≥3¹
Score 4: sensitivity for severe OSA	88%²
Train-of-four ratio before extubation	≥0.9⁴

Sources

1.SLEEP STRATEGIES: The flexibility of STOP-Bang Questionnaire to screen for OSA: A practical approach · CHEST Physician (Chung and Nagappa) · blogs.the-hospitalist.org0–2 low, 5–8 high; 3–4 upgraded by BMI >35, neck >40 cm, male sex or HCO3 ≥28 mmol/L.
2.Society of Anesthesia and Sleep Medicine Guidelines on Preoperative Screening and Assessment of Adult Patients With Obstructive Sleep Apnea · SASM, 2016 · ebi.ac.ukAnesth Analg 2016; full text via Europe PMC (PMC4956681). The 2014 ASA OSA practice guideline could not be accessed for verification.
3.Society of Anesthesia and Sleep Medicine Guideline on Intraoperative Management of Adult Patients With Obstructive Sleep Apnea · SASM, 2018 · ebi.ac.ukAnesth Analg 2018; full text via Europe PMC (PMC6135479).
4.New Practice Guidelines for Neuromuscular Blockade · APSF, 2023 · apsf.orgReproduces the recommendations of the 2023 ASA Practice Guidelines for Monitoring and Antagonism of Neuromuscular Blockade.

Facts on this page were checked against these sources on Oct 15, 2026. Guidelines change; confirm doses against current institutional protocols.