Comparison of the endoscopic surgical monitoring system and blood parameters for evaluating irrigation fluid absorption during bipolar plasmakinetic transurethral resection of the prostate: a prospective observational study

Irrigation fluid absorption is an unpredictable complication during transurethral resection of the prostate (TURP). This prospective study aimed to compare the Endoscopic Surgical Monitoring System (ESMS) and blood parameters for evaluating fluid absorption volume in patients undergoing bipolar plasmakinetic TURP. Bipolar TURP was performed using 0.9% saline for bladder irrigation. The ESMS measured fluid absorption volumes in real time. In addition, arterial blood samples were collected for blood gas analysis immediately before irrigation and after surgery, with the absorption volume calculated using equations based on changes in plasma sodium, chloride, potassium, calcium, and hemoglobin concentrations. A total of 420 patients (mean age 69.8 ± 7.7 years) were included. All calculated volumes based on blood parameters were higher than the ESMS-measured volume. The volume calculated from plasma chloride concentration changes showed the closest agreement with the ESMS volume (867.5 ± 748.9 vs. 843.3 ± 722.1 mL, P = 0.416), with a mean bias of 14.4 mL and 95% agreement limits of -385.7 to 414.5 mL. Regression analysis demonstrated a strong linear relationship between plasma chloride elevation and actual absorption volumes (R²=0.776, P = 0.001). However, further analysis revealed a mean percentage bias of + 19%, indicating a systematic overestimation tendency in blood chloride method. Furthermore, a clinically significant discrepancy (> 300 mL) between the blood chloride method and ESMS was associated with altered clinical management, including increased diuretic use (36.7% vs. 15.0%, P < 0.001) and limitation of intravenous fluids (33.3% vs. 17.5%, P = 0.004). Among the blood parameters, plasma chloride provides the most accurate estimation of irrigation fluid absorption and can serve as a practical hematologic indicator when ESMS is unavailable. However, clinicians should be aware of its inherent overestimation tendency and the potential for clinically significant discrepancies to impact patient management. This study was prospectively registered in the Chinese Clinical Trial Registry on December 25, 2023 (www.chictr.org.cn; Registration Number: ChiCTR2300079095).