Roux-en-Y Gastric Bypass
Patient phenotype
BMI ≥ 40 (or ≥ 35 with comorbidities). Almost universally OSA, hypertension, T2DM, GERD, possible obesity hypoventilation, NASH. Usually well-screened in pre-bariatric clinic with optimization done. 30s-60s.
Procedure
Laparoscopic creation of small (~30 mL) gastric pouch + Roux limb anastomosis bypassing duodenum + proximal jejunum. ~90-120 min. Reverse Trendelenburg + insufflation.
Anesthetic plan
GETA with RSI (high aspiration risk). Ramped position for induction. Multimodal opioid-sparing (dex 0.4-0.7 mcg/kg/h, ketamine 0.25 mg/kg, acetaminophen, ketorolac if appropriate). Avoid long-acting opioids — high OSA risk.
Setup
- ·Bariatric OR table (rated for weight + ramped pillows ready)
- ·Ramp / HELP position pre-induction (ear-to-sternal-notch alignment)
- ·Difficult airway cart (videolaryngoscope at minimum, BVM with PEEP, supraglottic backup)
- ·Long PIVs or US-guided IV (deep tissue)
- ·BMI-appropriate BP cuff + ECG patches
- ·Standard ASA + temp + NMB monitor (twitch unreliable in adipose — use ulnar)
Biggest concerns by phase
Airway risk + denitrogenation strategy
Obese patients desaturate fast (FRC ~ 30% lower, O₂ consumption higher). Preoxygenate 5 min with CPAP 10 cm H₂O + 100% FiO₂ in ramped + 25° head-up. Plan for mask difficulty (use 2-handed jaw thrust, oral airway) + difficult intubation (videolaryngoscope routine).
Drug dosing — IBW vs LBW vs TBW
Propofol induction: LBW (avoids overdose). Rocuronium: IBW (intubating dose 1 mg/kg IBW). Succinylcholine: TBW (extracellular fluid scales with TBW). Maintenance propofol: LBW. Opioids (fentanyl, hydromorphone): LBW. Sugammadex: TBW (capped at typical max). Wrong-weight dosing is a frequent oral exam trap.
RSI — modified RSI typical
GERD universal. Modified RSI: rapid-sequence induction with manual ventilation if SpO₂ drops, low-pressure (< 20 cm H₂O) ventilation. Cricoid debated — many bariatric programs omit. Have suction ready.
Ventilation — lung-protective + recruitment
TV 6-8 mL/kg IBW (NOT TBW — overdistends lungs). PEEP 8-12. Recruitment maneuvers q 30 min after position changes. Pneumoperitoneum further drops compliance — pressure-control mode often easier than volume-control.
VTE risk — already high, surgery makes higher
Bariatric patients = highest VTE risk in routine surgery. Sequential compression devices on at induction. Heparin 5000 U SQ preop or low-dose enoxaparin per protocol. Early ambulation postop.
Extubation + OSA postop strategy
Fully awake extubation in semi-Fowler or sitting. Reverse NMB to TOF > 0.9 (sugammadex preferred). Pain control without respiratory depression: scheduled acetaminophen, NSAID if appropriate, dex infusion, regional/wound infiltration. Resume CPAP in PACU per home settings.
Anastomotic leak detection
Tachycardia (> 110) is the earliest + most reliable sign of bypass leak. Don't dismiss as pain alone. Fever may be absent. Respiratory rate up. Surgical team notified for any sustained tachycardia — leak in this population is a surgical emergency.
Mock-defense scenarios
Practice answering these out loud. The probes show what an examiner is listening for.
BMI 52, OSA on home BiPAP, T2DM on metformin + GLP-1 agonist (semaglutide weekly, last dose 4 days ago), GERD. Surgery starts at 0730. NPO since midnight. Plan?
What an examiner probes for
- ▹GLP-1 + retained gastric contents — current ASA/SAMBA guidance (consider full stomach precautions even after fasting)
- ▹Modified RSI with ramped position + adequate preoxygenation
- ▹Proper drug dosing by IBW/LBW/TBW
- ▹OSA postop plan — CPAP available, opioid-sparing analgesia
- ▹PONV prophylaxis (Apfel + scopolamine + dex + ondansetron)
Sources
- SOBA Bariatric Anesthesia Guidelines 2020
- Miller's Ch 71 + 72
- ASA GLP-1 Consensus 2023
Anatomy reference
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