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Anesthesia for Bariatric Surgery + Obesity
TEXTSpecial Populations · 8 min read
Largest growth population in surgical volume. Drug dosing, airway plan, ventilation strategy, OSA management — all different.
After this lesson you can
2 min read6 sections- Optimize position + airway for the bariatric patient.
- Adjust drug dosing by weight type (TBW, IBW, LBW).
- Plan aspiration prophylaxis.
- Manage post-op pain + airway monitoring.
Definitions + dosing scalars
IBW (Devine): men 50 + 2.3 (in over 60); women 45.5 + 2.3 (in over 60).
LBW: roughly IBW × 1.2 in obese.
ABW (adjusted): IBW + 0.4 (TBW − IBW) — for water-soluble drugs in obese.
- propofol maintenance
- rocuronium
- vecuronium
- neostigmine
- hydromorphone
Use TBW for: succinylcholine (pseudocholinesterase scales with TBW), sugammadex (per package insert).
- propofol induction
- fentanyl
- remifentanil
Use ABW for: hydrophilic abx (cefazolin, gentamicin).
Airway
Ramp position essential — align tragus with sternum (HELP — Head Elevated Laryngoscopy Position; bed-stack pillows or commercial ramp device).
Pre-oxygenate with 25° head-up + CPAP.
Video laryngoscopy first-line for BMI >40 or OSA.
- bougie
- supraglottic
- awake fiberoptic kit
Ventilation strategy
Recruitment after intubation (CPAP 40 cmH₂O × 30 sec).
PEEP 8-12 mandatory.
Tidal volume 6-8 mL/kg IBW (NOT total body weight — would barotrauma).
FiO₂ titrated to SpO₂ ≥94% (avoid 100% unless required — promotes absorption atelectasis).
Reverse Trendelenburg / head-up 25-30° throughout case.
Use pressure-limited modes (PCV or VC with pressure limit) to keep plateau <30 cmH₂O.
Higher driving pressures = postop pulm complications.
Pharmacology
Sevo acceptable.
Avoid isoflurane (long emergence).
TIVA propofol-remi based on LBW.
Opioid-sparing approach (multimodal — dex, ketamine, lidocaine infusion, regional, IV acetaminophen) — minimize postop respiratory depression.
Avoid morphine if possible (active metabolites accumulate, respiratory depression).
Local anesthetic dose by IBW.
OSA + postop monitoring
STOP-BANG ≥3 or known OSA continuous SpO₂ + capnography postop, monitored bed.
Avoid full µ-opioids for outpatient bariatric (rare anyway — most stay 1 night).
Multimodal analgesia + regional first.
Patient education on home CPAP compliance critical.
Bariatric procedure-specific
OG tube placement coordinated with surgeon (bougie sizing) — communicate, don't push past resistance.
Leak test at end.
Position considerations: lithotomy/split-leg, ramped — pressure-injury risk.
DVT prophylaxis essential — sequential compression + heparin/LMWH (consider higher dose: enoxaparin 40 mg BID for class III obesity).
Rhabdomyolysis risk in super-obese (long supine cases) — check CK if reduced UOP.
Postop nausea (high rate) — multimodal antiemetics, dexamethasone, ondansetron, scopolamine patch.
⚠ Common pitfalls
- Standard dose-per-TBW in bariatric — many drugs use IBW or LBW.
- Pre-O2 supine in obese — inadequate; HELP position essential.
- Heavy opioid post-op in OSA — respiratory depression risk.
- Forgetting GLP-1 agonist hold in bariatric — recent meds class warrants modified NPO.
💎 Clinical pearls
- Propofol induction by LBW, maintenance by TBW; sux by TBW; NMB by IBW; opioids by IBW.
- Ramped (HELP — head elevated, tragus aligned with sternum) position pre-induction.
- Aspiration prophylaxis: famotidine + metoclopramide + sodium citrate before induction.
- CPAP available + ready post-extubation; admit OSA patients to monitored bed.
Recap
- Propofol induction by LBW, maintenance by TBW; sux by TBW; NMB by IBW; opioids by IBW.
- Ramped (HELP — head elevated, tragus aligned with sternum) position pre-induction.
- Aspiration prophylaxis: famotidine + metoclopramide + sodium citrate before induction.
- CPAP available + ready post-extubation; admit OSA patients to monitored bed.
Mark each section done to complete the module.