What's the next step for a morbidly obese patient with increased airway pressures during prone positioning for Percutaneous Nephrolithotomy (PCNL) access to treat a struvite, partial staghorn kidney stone?

Management of Increased Airway Pressures in Morbidly Obese Patient During Prone Positioning for PCNL

The next step after returning the morbidly obese patient to supine position and normalizing airway pressures is to consider alternative surgical positioning approaches, with awake intubation and patient self-positioning in prone position being the most appropriate option to safely proceed with the PCNL procedure. 1

Assessment of the Situation

• The patient experienced markedly increased airway pressures in prone position, which resolved upon returning to supine position, indicating positioning-related respiratory compromise 2
• Morbidly obese patients are at higher risk for airway complications during anesthesia, with complications occurring rapidly and potentially catastrophically 2
• The patient still requires treatment for the struvite, partial staghorn kidney stone, which necessitates prone positioning for PCNL access 3

Alternative Positioning Options

Awake Intubation with Patient Self-Positioning

• The most appropriate next step is to perform awake intubation followed by allowing the patient to position themselves prone before inducing general anesthesia 1
• This technique involves:
  • Detailed preoperative counseling about the procedure
  • Premedication with a sedative and antisialagogue
  • Airway topicalization to suppress gag reflex and pain
  • Fiberoptic bronchoscope intubation while the patient is awake
  • Patient self-positioning in prone position before induction of general anesthesia 1

Benefits of Awake Intubation and Self-Positioning

• Allows the patient to find a comfortable position that minimizes respiratory compromise 1
• Reduces the risk of airway complications that occur during positioning by anesthesia staff 2
• Maintains patient's spontaneous ventilation during the critical positioning phase 1
• Has been shown to be safe and effective in properly selected morbidly obese patients 1

Ventilation Strategies if Proceeding with Prone Position

• Use ideal body weight to calculate tidal volume (5-7 ml/kg) during controlled ventilation 2
• Ensure peak inspiratory pressure remains <35 cmH2O 2
• Consider pressure-controlled ventilation rather than volume-controlled ventilation, as it often achieves greater tidal volumes for a given peak pressure 2
• Add sufficient PEEP and recruitment maneuvers to reduce intra- and postoperative atelectasis 2
• Maintain ramped position principles even in prone position, ensuring optimal positioning of the chest and abdomen to allow for maximum respiratory excursion 2

Considerations for Prone Positioning in Obese Patients

• Prone positioning can be safely performed in morbidly obese patients with proper technique and preparation 4
• Studies show that prone positioning in obese patients with respiratory issues may actually improve oxygenation more significantly than in non-obese patients 4
• Ensure adequate support under the chest and pelvis to allow free movement of the abdomen during ventilation 2
• Monitor for increases in intra-abdominal pressure, which can rise from baseline during prone positioning in obese patients 2

Alternative Surgical Approaches to Consider

• If awake intubation with self-positioning is not feasible or fails to maintain adequate ventilation:
  • Consider regional anesthesia where possible, which is preferred to general anesthesia in obese patients, though this may be challenging for PCNL 2
  • Discuss with the surgical team about alternative approaches to stone removal that don't require prone positioning 3
  • Consider modified supine or lateral decubitus positioning for PCNL, which may be better tolerated in this patient 3

Common Pitfalls and Caveats

• Failure to recognize the severity of positioning-related airway compromise can lead to rapid desaturation and catastrophic outcomes in morbidly obese patients 2
• Rescue techniques such as supraglottic airway devices and emergency cricothyroidotomy have increased failure rates in obese patients 2
• Attempting to force prone positioning without addressing the underlying cause of airway pressure increases may lead to severe respiratory compromise 2
• Inadequate pre-oxygenation and positioning during induction can significantly reduce the safe apnea period in morbidly obese patients 5

By implementing awake intubation with patient self-positioning, you can safely proceed with the PCNL procedure while minimizing the risk of respiratory complications in this morbidly obese patient.