Supine Versus Prone Positioning in Percutaneous Nephrolithotomy: A Retrospective Cohort Study Comparing Intraoperative Hemodynamic and Respiratory Stability

Background: Percutaneous nephrolithotomy (PCNL) is the gold-standard treatment for large renal stones. The prone position, traditionally used, may impair cardiopulmonary function due to thoracoabdominal compression, whereas the supine position offers potential physiological and practical advantages. Objectives: To compare intraoperative hemodynamic and respiratory stability between supine and prone PCNL. Methods: This single-center retrospective cohort study analyzed 40 patients (supine = 20, prone = 20) undergoing PCNL between January-December 2023. Inclusion criteria were age ≥ 18 years, American Society of Anesthesiologists (ASA) I/II, and renal pelvic stones ≥ 2 cm. Groups were matched for age, sex, BMI, stone size, and ASA status. All procedures followed a standardized anesthetic protocol. Primary outcomes were intraoperative blood pressure, heart rate (HR), oxygen saturation (SpO₂), and end-tidal carbon dioxide (ETCO₂). Secondary outcomes included fluid administration, anesthesia duration, and operative time. Data were analyzed using independent t-tests; estimates are unadjusted. Results: The prone position was associated with significant hemodynamic instability, manifesting as profoundly lower SBP and DBP and a higher HR throughout the procedure (e.g., at 80 min: SBP 89.5 ± 4.6 vs. 133.3 ± 12.4 mmHg, P < 0.001; HR 114.8 ± 11.8 vs. 75.8 ± 3.4 bpm, P < 0.001). Pulmonary function was also compromised in the prone group, as evidenced by significantly lower SpO₂ (nadir: 96.8 ± 1.3% vs. 100%, P < 0.001) and elevated ETCO₂ (peak: 40.9 ± 1.2 vs. 34.9 ± 0.4 mmHg, P < 0.001). Furthermore, patients in the prone position required greater intraoperative fluid resuscitation (1950.0 ± 484.0 mL vs. 1475.0 ± 472.3 mL, P = 0.003) and experienced a longer anesthesia duration (158.3 ± 25.0 vs. 118.3 ± 18.3 min, P < 0.001). Operative time, complications, and stone-free rates (SFRs) were comparable among the groups. Conclusions: Supine PCNL may offer superior intraoperative physiological stability, with improved hemodynamics, preserved respiratory function, reduced fluid needs, and shorter anesthesia duration, without compromising surgical efficacy. These findings support supine positioning as a potentially safer alternative for selected patients, though further prospective validation is warranted.