What's the next step for a morbidly obese patient with struvite partial staghorn renal calculus who develops increased airway pressures during prone Percutaneous Nephrolithotomy (PCNL)?

From the Guidelines

The next step for a morbidly obese patient experiencing increased airway pressures during prone PCNL for a struvite partial staghorn calculus is to immediately reposition the patient to improve ventilation, and consider converting to a supine PCNL approach if the surgeon is experienced with this technique. The anesthesiologist should first attempt to optimize ventilation by increasing the FiO2 to 100%, adjusting ventilator settings (decreasing tidal volume, increasing respiratory rate), and ensuring the endotracheal tube is properly positioned. If these measures fail, the procedure should be temporarily paused and the patient repositioned to a modified lateral or supine position with appropriate padding to maintain access to the kidney.

Key Considerations

• The increased airway pressures likely result from the patient's body habitus causing abdominal compression in the prone position, which elevates the diaphragm and reduces lung compliance 1.
• This mechanical compression is particularly problematic in morbidly obese patients and can lead to hypoxemia, hypercarbia, and hemodynamic instability if not promptly addressed.
• Hemodynamic monitoring should be continued throughout with arterial blood gas analysis to assess ventilation status.
• If repositioning fails to improve ventilation, the procedure may need to be aborted and reconsidered using alternative approaches such as retrograde intrarenal surgery or staged procedures.

Alternative Approaches

• Ureteroscopy occasionally is necessary to remove retained ureteral stone fragments that are too large to pass spontaneously 1.
• However, the utilization of both PNL and ureteroscopy in patients with staghorn stones has been reported to be successful.
• Laparoscopic approaches are not anticipated to become a suitable treatment approach in patients with complex staghorn stones in the near future 1.

Recommendations

• Proceed with supine PCNL if the surgeon is experienced with this technique, as it may offer a better alternative to prone PCNL in morbidly obese patients with increased airway pressures.
• Consider alternative approaches such as retrograde intrarenal surgery or staged procedures if repositioning fails to improve ventilation.

From the Research

Next Steps for Morbidly Obese Patient with Struvite Partial Staghorn Renal Calculus

• The patient's condition of developing markedly increased airway pressures during prone PCNL suggests a need for an alternative approach to manage the airway pressures and ensure the patient's safety during the procedure.
• Considering the patient's morbid obesity and the development of increased airway pressures in the prone position, the supine position may offer advantages in terms of airway control and patient comfort, as suggested by studies 2, 3, 4.
• The use of supine PCNL has been shown to be feasible and effective, with benefits including less operation time, less patient handling, and easier access to the urethra and upper calyces, making it a suitable option for morbidly obese patients 3, 5.
• Given the patient's condition and the need for effective management of the struvite partial staghorn renal calculus, proceeding with supine PCNL (option D) appears to be a reasonable next step, as it can provide optimal cardiovascular and airway control while allowing for the treatment of the renal calculus.

Considerations for PCNL in Morbidly Obese Patients

• Morbidly obese patients may require special consideration during PCNL, including the use of alternative positions to manage airway pressures and ensure patient comfort.
• The supine position has been shown to be beneficial for morbidly obese patients, as it can reduce the risk of respiratory complications and provide better access to the urethra and upper calyces 3, 4.
• The decision to use supine PCNL should be based on the patient's individual characteristics and the surgeon's preference and experience, as suggested by study 4.

Treatment of Struvite Stones

• The treatment of struvite stones, such as the one present in this patient, typically involves complete stone eradication in conjunction with antibiotic therapy, as outlined in study 6.
• PCNL is considered the gold-standard approach to treating struvite calculi, but adjuncts may be used when deemed necessary, as noted in study 6.