What are the guidelines for anesthesia management in patients with morbid obesity (Body Mass Index (BMI) ≥ 40) undergoing surgery?

Guidelines for Anesthesia Management in Morbidly Obese Patients

Every anesthesiologist managing morbidly obese patients should follow the comprehensive guidelines established by the Association of Anaesthetists of Great Britain and Ireland and the Society for Obesity and Bariatric Anaesthesia, which provide a structured approach to reduce morbidity and mortality in this high-risk population. 1

Organizational Recommendations

• Every hospital should nominate an anesthesia lead for obesity to ensure appropriate equipment availability and training standards 1
• Operating lists should include patients' weight and BMI to facilitate proper preparation 1
• Experienced anesthetic and surgical staff should manage obese patients, with patients having an Obesity Surgery Mortality Risk Score (OS-MRS) >3 requiring discussion with a consultant 1
• Specific training on managing and moving morbidly obese patients should be provided to all staff involved in their care 1

Pre-operative Assessment and Risk Stratification

• Central obesity and metabolic syndrome should be identified as specific risk factors that increase perioperative complications 1
• Sleep-disordered breathing must always be evaluated, as severe obstructive sleep apnea occurs in 10-20% of patients with BMI >35 kg/m² and is often undiagnosed 1, 2
• Respiratory assessment should consider that obesity reduces functional residual capacity while increasing metabolic rate and work of breathing, leading to rapid desaturation 1
• Distinguish between true asthma and obesity-related wheeze, as 50% of obese patients diagnosed with asthma "recover" with weight loss 1

Equipment Requirements

• Specialized equipment must be available and readily accessible, including:
  • Bariatric operating tables with appropriate weight limits and positioning attachments 1
  • Ramping devices/pillows for proper positioning 1
  • Specialized beds with pressure-relieving mattresses 1
  • Long spinal/epidural needles and arterial lines 1
  • Difficult airway equipment 1
  • Neuromuscular blockade monitors 1
  • Depth of anesthesia monitoring 1

Airway Management

• A robust airway strategy must be planned and discussed with the team, as desaturation occurs quickly and airway management can be difficult in obese patients 1, 2
• Position patients in the ramped position with the tragus of the ear level with the sternum to optimize laryngoscopy conditions 1
• Consider anesthetizing the patient in the operating theater rather than in an induction room to avoid transport-related complications 1
• NAP4 findings highlighted that airway complications in obese patients occur rapidly and potentially catastrophically, with increased failure rates of rescue techniques 1

Anesthetic Technique

• Regional anesthesia is recommended when possible, though technically more challenging in obese patients 1, 3
• For neuraxial techniques:
  • Use the sitting position for improved success rates 1
  • Leave at least 5 cm of catheter in the epidural space to reduce migration 1
  • Calculate local anesthetic doses using lean body weight despite standard doses being recommended for central neuraxial blockade 1
• When general anesthesia is required:
  • Use easily reversible drugs with fast onset and offset 1, 4
  • Drug dosing should be based on lean body weight and titrated to effect, not total body weight 1, 4
  • Exercise caution with long-acting opioids and sedatives 1, 2
  • Always use neuromuscular monitoring when administering neuromuscular blocking drugs 1
  • Consider depth of anesthesia monitoring, especially with total intravenous anesthesia 1

Positioning

• Use ramped or sitting position during induction and recovery to improve respiratory mechanics 1
• Protect pressure points with gel pads and padding 1
• Secure patients to the operating table with wide Velcro strapping 1

Postoperative Care

• Implement appropriate venous thromboembolism prophylaxis and early mobilization as obesity increases VTE risk 1
• Consider postoperative intensive care support based on comorbidities and surgical factors rather than obesity alone 1
• Patients requiring longer-acting opioids need closer monitoring for developing hypercapnia 1
• High-flow oxygen delivery devices or CPAP should be available in the post-anesthesia care unit 1

Common Pitfalls and Caveats

• Underestimating the rapid desaturation that occurs in obese patients during apnea 1
• Failing to plan for difficult airway management and rescue techniques 1
• Inappropriate drug dosing based on total body weight rather than lean body weight 1, 4
• Inadequate positioning leading to difficult intubation and ventilation 1
• Insufficient monitoring for residual neuromuscular blockade 1
• Overlooking sleep-disordered breathing in the postoperative period 1

By following these guidelines, anesthesiologists can significantly reduce morbidity and mortality risks when managing morbidly obese patients undergoing surgery.