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

From the Guidelines

The next step for a morbidly obese patient developing increased airway pressures during prone positioning for PCNL would be to immediately reposition the patient to a modified supine or lateral position to relieve respiratory compromise. This decision is based on the need to prioritize the patient's respiratory status and prevent further complications. The anesthesiologist should increase the fraction of inspired oxygen (FiO2) to maintain oxygen saturation above 92% and consider adjusting ventilator settings with lower tidal volumes (6-8 mL/kg ideal body weight) and higher respiratory rates to maintain adequate minute ventilation, as recommended by the international expert panel-based consensus recommendations for lung-protective ventilation for the surgical patient 1. If respiratory parameters don't improve, the procedure should be temporarily paused to allow for stabilization. Alternative approaches include using the Valdivia supine position or endoscopic combined intrarenal surgery (ECIRS) technique, which places less pressure on the abdomen and thorax. For subsequent management, consider staged procedures with shorter operative times, regional anesthesia when feasible, and preoperative optimization of the patient's respiratory status. The increased airway pressures occur because prone positioning in obese patients causes abdominal compression against the operating table, pushing the diaphragm cephalad and reducing lung compliance, which is particularly problematic when managing large stones like struvite staghorn calculi that typically require longer operative times. Some key considerations for the management of staghorn calculi include the use of percutaneous nephrolithotomy (PNL) as the first-line treatment, with flexible nephroscopy as a routine part of standard PNL, and the use of normal saline irrigation for PNL and ureteroscopy (URS) 1. However, in this specific scenario, the primary concern is the patient's respiratory status, and the management strategy should be focused on relieving the respiratory compromise and preventing further complications.

From the Research

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

The patient in question develops markedly increased airway pressures during prone positioning for PCNL, which normalizes upon returning to the supine position. Considering the provided evidence, the next step would involve alternatives that accommodate the patient's condition, specifically focusing on positioning that minimizes respiratory complications.

• Supine PCNL: This approach has been shown to be effective and safe, especially in high-risk and obese patients 2. It allows for optimal cardiovascular and airway control, which is crucial in this scenario. The supine position can facilitate simultaneous management of renal and ureteral stones, making it a viable option for patients with complex stone disease.
• Comparison with Prone Position: While the prone position offers a broader surface area for percutaneous access and more space for manipulating the nephroscope and lithotripters, its limitations in terms of airway control and potential for increased respiratory complications in morbidly obese patients make supine PCNL a more suitable choice in this context 3.
• Outcomes in Obese Patients: Studies have demonstrated that PCNL outcomes are statistically independent of body mass index (BMI), indicating that the procedure can be safely performed in morbidly obese patients with appropriate positioning and care 4, 5. This supports the consideration of supine PCNL as a next step.
• Technique and Effectiveness: The effectiveness of supine PCNL, including its ability to achieve high stone-free rates comparable to those in non-obese patients, further supports its use in this patient population 2, 6.

Given these considerations, the most appropriate next step for the morbidly obese patient who develops increased airway pressures during prone PCNL positioning would be to proceed with the procedure in the supine position, which is expected to mitigate the respiratory issues while effectively treating the struvite partial staghorn renal calculus.