Association between urine pH and risk of contrast-associated acute kidney injury among patients after emergency percutaneous coronary intervention: a V-shape relationship?

AIM: We investigated whether perioperative urine pH was associated with contrast-associated acute kidney injury (CA-AKI) in patients undergoing emergency percutaneous coronary intervention (PCI). METHODS: The study enrolled 1109 consecutive patients undergoing emergency PCI. Patients were divided into three groups based on perioperative urine pH (5.0–6.0, 6.5– 7.0, 7.5–8.5). The primary endpoint was the development of CA-AKI, defined as an absolute increase ≥ 0.3 mg/dL or a relative increase ≥ 50% from baseline serum creatinine within 48 h after contrast medium exposure. RESULTS: Overall, 181 patients (16.3%) developed contrast-associated acute kidney injury. The incidences of CA-AKI in patients with urine pH 5.0–6.0, 6.5–7.0, and 7.5–8.5 were 19.7%, 9.8%, and 23.3%, respectively. After adjustment for potential confounding factors, perioperative urine pH 5.0–6.0 and 7.5–8.5 remained independently associated with CA-AKI [odds ratio (OR)1.86, 95% confidence interval (CI) 1.25–2.82, P = 0.003; OR 2.70, 95% CI 1.5–4.68, P < 0.001, respectively]. The association was consistent in subgroups of patients stratified by several CA-AKI risk predictors. However, the risk of CA-AKI associated with urine pH 7.5–8.5 was stronger in patients with worse renal function (estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73m(2)) (HR 5.587, 95% CI 1.178–30.599 vs. HR 2.487, 95% CI 1.331–4.579; overall interaction P < 0.05). CONCLUSION: The urine pH and CA-AKI may underlie the V-shape relationship.