Anesthesiology APPLIED Exam › Endocrine, renal, hepatic and metabolic

Morbid obesity and bariatric surgery

Endocrine, renal, hepatic and metabolic·~5 min read· Physician-reviewed✓ Sourced · 4

Stem

A 42-year-old man, 158 kg, 175 cm (BMI 52), is scheduled for laparoscopic sleeve gastrectomy. He snores loudly, his wife has witnessed apneas, and he has never had a sleep study. Neck circumference is 49 cm, Mallampati III. Serum bicarbonate is 30 mmol/L. He takes semaglutide, on a stable dose for six months, and denies nausea or bloating.

Question

How will you plan his anesthetic, from induction through his postoperative disposition?

Ideal answer

HeadlineHigh-risk airway with untreated OSA: ramped, preoxygenated to end-tidal O2 0.9, video laryngoscope, monitored bed afterward.

Semaglutide continued, liquid diet for 24 hours beforehand, because the dose is stable and he is asymptomatic;¹ gastric ultrasound before induction. The bicarbonate sends me looking for obesity hypoventilation and pulmonary hypertension.
Ramped, external auditory meatus level with sternal notch; preoxygenated head-up by tight-fitting mask or high-flow nasal oxygen to end-tidal oxygen above 0.9, with apneic oxygenation during laryngoscopy.
Video laryngoscope, second-generation supraglottic airway ready; propofol and rocuronium on lean weight, succinylcholine on total weight.
Ideal-body-weight tidal volumes, PEEP, recruitment, because lungs scale with height and collapse under weight; multimodal opioid-sparing analgesia, full reversal, awake semi-upright extubation.
Monitored bed with continuous oximetry, because his apnea is untreated: not an unmonitored floor with a PCA.

Breaking down the answer

Ramped and head-up — aligns the airway axes and raises functional residual capacity, extending safe apnea time from about 1–2 minutes to several minutes in a morbidly obese patient.
Rapid sequence or not — obesity alone does not mandate it; gastric volume and pH are similar to lean patients. I use it for reflux, diabetic gastroparesis, GLP-1 use with symptoms or in dose escalation, or a full stomach on ultrasound.
GLP-1 agonists — most patients continue them; risk is highest in dose escalation, on higher doses, or with active nausea, vomiting, pain or constipation. I defer elective surgery for escalation or symptoms and treat a full antrum as a full stomach.¹
Dosing scalar — succinylcholine on total weight because pseudocholinesterase activity and volume of distribution rise;² sugammadex on actual weight, which in the label's BMI ≥40 trial reversed faster than ideal-weight dosing;³ opioids on lean weight and titrated.
Ventilation — 6–8 mL/kg ideal body weight, PEEP 8–10 cmH2O or higher with pneumoperitoneum, and recruitment, because atelectasis forms within minutes of induction.
Disposition — the examiner grades judgment here: continuous oximetry or a monitored bed for untreated or severe OSA, opioid-requiring patients and those with hypoventilation.
VTE prophylaxis — obesity and laparoscopy raise risk; mechanical and pharmacologic prophylaxis and early ambulation.

Follow-up question

After induction, mask ventilation is difficult and the first video laryngoscopy attempt fails. The SpO2 is 88% and falling. What do you do?

Follow-up answer

HeadlineA failing airway in a patient with minimal oxygen reserve; I call for help and announce the situation.

I place a second-generation supraglottic airway to oxygenate rather than make repeated attempts. If oxygenation improves, I decide with the team whether to intubate through it with a flexible scope or to wake him. If I cannot oxygenate, I declare CICO and perform a front-of-neck airway, scalpel-bougie-tube, with a vertical skin incision because landmarks are hard to palpate. I reassess saturation and end-tidal CO2 after each step. Airway ultrasound to mark the cricothyroid membrane before induction would have reduced this risk.

Pitfalls that cost points

Treating obesity alone as an indication for rapid sequence.
Extubating deep or supine in a patient with OSA.

Rapid-fire

Q: Why do obese patients desaturate so quickly? A: FRC falls below closing capacity and oxygen consumption is higher; the oxygen reservoir is smaller and used faster.

Q: Why does obesity hypoventilation syndrome matter? A: Daytime hypercapnia, blunted CO2 drive, pulmonary hypertension and high risk of postoperative respiratory failure; a bicarbonate of 28 mmol/L or more also raises the probability of significant OSA.⁴

Q: Why is the blood pressure cuff a problem? A: A cuff that is too small overestimates pressure; I use the correct size, a forearm cuff, or an arterial line.

Q: What is the leak test after sleeve gastrectomy? A: The surgeon asks for methylene blue or air through an orogastric tube, so I coordinate tube placement and withdraw it before stapling.

Numbers to know

Item	Value
Class III obesity	BMI ≥ 40 kg/m²
STOP-BANG high risk	5–8; 3–4 upgraded by BMI > 35, neck > 40 cm, male sex or HCO3 ≥ 28⁴
Preoxygenation target	End-tidal O2 ≥ 0.9
Tidal volume	6–8 mL/kg ideal body weight
PEEP	8–10 cmH2O or more
Ideal body weight (men)	50 kg + 2.3 kg per inch over 5 ft
Sugammadex scalar	Actual body weight: 2, 4 or 16 mg/kg by depth of block³

Sources

1.New Multi-society Clinical Practice Guidance Released (GLP-1 receptor agonists) · ASA / AGA / ASMBS / ISPCOP / SAGES, 2024 · asahq.org
2.Obesity: succinylcholine dosing · OpenAnesthesia · openanesthesia.org
3.BRIDION (sugammadex) injection prescribing information · Merck / FDA label · merck.comSection 2.1 dosing on actual body weight; section 8.10 obese patients.
4.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.

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