Association between hyperchloremia and metabolic acidification in patients undergoing bipolar transurethral resection of the prostate: a prospective observational study

Irrigation fluid absorption during transurethral resection of the prostate (TURP) may cause systemic disturbances. This study evaluated perioperative plasma acid-base alterations in patients undergoing bipolar plasmakinetic TURP. Bipolar TURP was performed with 0.9% saline irrigation. Arterial blood gas and biochemistry were measured before and immediately after surgery. Based on the direction of pH change (ΔpH), patients were categorized into the Acidifying Group (ΔpH < 0) or Non-Acidifying Group (ΔpH ≥ 0). Standard base excess (SBE) was analyzed using a simplified Stewart approach. Among 609 patients, 378 (62.1%) in the Acidifying Group (postoperative pH 7.31 ± 0.08) had significant decreases in SBE (from 1.10 ± 1.32 to -3.87 ± 2.06 mmol/L; P < 0.001). Stewart analysis showed that this acidifying process was mainly associated with a reduced Na + -Cl − difference (34.4 ± 5.9 to 28.6 ± 6.2 mmol/L; base excess effect from − 0.61 ± 1.05 to -6.44 ± 3.43 mmol/L; P < 0.001). These changes were not observed in the Non-Acidifying Group. Linear regression showed that the change in postoperative plasma chloride concentration (ΔCl − ) increased significantly with irrigation fluid absorption volume ( R 2 = 0.8243, P < 0.001), whereas postoperative pH decreased significantly as ΔCl − increased ( R 2 = 0.6703, P < 0.001). Multivariable logistic regression identified surgical duration (OR 3.067 per 10-min, 95% CI 1.306 to 9.956; P = 0.013) and resected tissue weight (OR 3.203 per 10-g, 95% CI 1.041 to 9.855; P = 0.042) as factors significantly associated with postoperative acidification. The Acidifying Group had significantly higher rates of postoperative hypotension (14.3% vs. 6.9%) and longer PACU stays (1.44 ± 0.56 vs. 0.96 ± 0.45 h) (both P < 0.05). Hyperchloremia-associated acidifying effect is the predominant acid-base alteration in patients after bipolar TURP, related to irrigation fluid absorption, may affect postoperative outcomes and warrants greater attention during perioperative care. Real-time monitoring of irrigation fluid absorption may be necessary in this particular surgical population. Chinese Clinical Trial Registry ( www.chictr.org.cn ; Registration Number: ChiCTR2300079095; Registration Date: December 25, 2023).