Anaesthesia for Obesity

Quick Answer

Obesity (BMI >30 kg/m²) affects 30% of Australian adults and presents significant anaesthetic challenges due to physiological changes including reduced functional residual capacity (FRC), increased airway resistance, and obstructive sleep apnoea (OSA) in 40-60% of cases. Airway management is more difficult with higher incidence of difficult mask ventilation (grade 3-4, 5-10% vs. 1-2% non-obese) and difficult intubation (2-3% vs. 0.5-1%). Preoxygenation requires 3-5 minutes in 25-30° head-up position (improves FRC, extends safe apnoea time from 90 seconds to 3-4 minutes). Rapid sequence induction with ramped position (ear-to-sternal notch alignment) improves laryngoscopic view. Drug dosing uses ideal body weight (IBW) for lipophilic drugs (fentanyl, midazolam) and total body weight (TBW) for hydrophilic drugs (succinylcholine, rocuronium), with adjustments for highly lipophilic drugs (propofol induction 2 mg/kg IBW, maintenance 10-15 mg/kg/hour IBW). Positioning with reverse Trendelenburg or beach chair position improves respiratory mechanics. Postoperative care requires CPAP/BiPAP for OSA patients, multimodal analgesia to reduce opioid requirements, early ambulation, and thromboprophylaxis with LMWH (higher doses often required). Indigenous Australians have higher obesity rates (40-50% in remote communities), requiring culturally safe preoperative assessment, involvement of Aboriginal Health Workers, and planning for postoperative care in remote settings. [1-10]