Hemodynamic Effects of Surgical Position in Prone vs. Supine Percutaneous Nephrolithotomy

Percutaneous nephrolithotomy (PNL) is a widely used minimally invasive surgical technique for the treatment of large and complex renal calculi. Traditionally, PNL has been performed in the prone position; however, the supine position has gained popularity in recent years due to potential anesthetic and surgical advantages. Surgical positioning can significantly influence cardiovascular and respiratory function, potentially leading to intraoperative and postoperative hemodynamic fluctuations.

Previous literature suggests that the prone position may increase intrathoracic pressure and impair venous return, potentially compromising hemodynamic stability, while the supine position may provide a more stable cardiovascular profile. However, existing data are limited, and results remain inconclusive, particularly in direct comparative studies.

This prospective, randomized controlled clinical trial aims to compare the effects of prone and supine positions during PNL on patients' intraoperative and postoperative hemodynamic parameters. The study will enroll 84 patients aged 18-80 years with American Society of Anesthesiologists (ASA) physical status I-III undergoing elective PNL. Patients will be randomly assigned to either the prone (n=42) or supine (n=42) position.

Inclusion criteria

include patients with renal calculi suitable for PNL and meeting the study's eligibility requirements. Exclusion criteria include pregnancy, uncontrolled coagulopathy, previous renal surgery, severe cardiac, pulmonary, or neurological disease, preoperative urinary tract infection, surgery duration outside 60-120 minutes, and multiple access tracts.

Preoperative evaluation will include demographic data, stone characteristics, and relevant laboratory and imaging findings. Intraoperative data will include systolic and diastolic blood pressure, heart rate, arterial blood gas analysis, operative time, anesthesia duration, access details, irrigation volume, and any transfusion or complications. Postoperative parameters will include nephrostomy duration, length of hospital stay, and presence of residual stones as assessed by postoperative CT scan.

Surgical techniques will be standardized for both positions. Prone PNL will involve initial lithotomy positioning for ureteral catheter placement followed by prone positioning for renal access under fluoroscopic guidance. Supine PNL will be performed in the Galdakao-modified Valdivia position with similar access and fragmentation protocols.

The primary outcome is the difference in intraoperative and postoperative hemodynamic stability between positions. Secondary outcomes include complication rates, residual stone rates, and hospital stay duration.

This study aims to provide high-quality evidence to guide surgeons and anesthesiologists in selecting the optimal patient position for PNL, particularly in individuals with higher hemodynamic risk.

Inclusion criteria

• ASA physical status I-III
• Presence of renal calculi indicated for PNL

Exclusion criteria

• Pregnancy
• Uncontrolled coagulopathy
• Previous renal surgery
• Severe cardiac, pulmonary, or neurological disease
• Preoperative urinary tract infection (non-sterile urine culture)
• Surgery duration <60 minutes or >120 minutes
• Preoperative blood transfusion
• Multiple access tracts