Anesthesia Considerations 

Obesity 

 

 

Definitions (WHO, NIH)  

 

• Overweight: BMI ≥25.0 to 29.9 

• Obesity: BMI ≥30 

• Obesity class I: BMI of 30.0 to 34.9 

• Obesity class II: BMI of 35.0 to 39.9

• Obesity class III (severe obesity, massive obesity): BMI ≥40 

 

 

Considerations 

 

• Potentially difficult airway 

• Physiologic changes of obesity:

  • ↓ FRC →  fast desaturation

  • ↑ cardiac demand & output with limited reserve

  • ↑ gastric volume & abdominal pressure → ↑ aspiration risk

  • ↑ postoperative morbidity & mortality (respiratory failure, wound infections, thromboembolism risk) 

• Co-morbid diseases:

  • Airway: OSA

  • Respiratory: obesity hypoventilation syndrome (OHS), pickwickian syndrome, pulmonary hypertension, restrictive lung disease

  • Cardiac: hypertension, coronary artery disease, left ventricular hypertrophy, biventricular failure 

  • Endocrine: diabetes

  • GI: reflux, non-alcoholic fatty liver disease 

  • Altered pharmacology:

    • Implications for loading vs. steady state infusions (IBW vs TBW)

    • Sensitivity to sedatives & opioids

    • ↓ neuraxial dose may be needed

• Potential technical difficulties: 

  • Vascular access

  • Monitoring (NIBP)

  • Regional

 

 

Anesthetic Goals 

 

• Safe airway management; avoid hypoxemia & aspiration

• Evaluate physiologic impact of obesity on patient

• Establish whether regional technique is feasible

• Minimize perioperative complications:

  • Minimize postoperative airway obstruction/hypoventilation (ensure no residual anesthetic, extubate & nurse semi-recumbent, continuous oxygen saturation monitoring postoperatively & effective postoperative analgesia)

  • Avoid thrombotic complications

  • Avoid peripheral nerve injury 

 

 

Potential Conflicts 

 

• Difficult airway vs. aspiration risk (RSI)

• OSA vs. opioid requirements postoperatively & difficulty with regional procedures