Incidence and risk factors of acute kidney injury among neurocritical patients in high-altitude regions: a retrospective cohort study

Background Acute kidney injury (AKI) is a frequent complication in intensive care unit (ICU) patients with acute brain injury. High-altitude hypoxia may aggravate renal vulnerability, but relevant evidence is limited. This study aims to investigate the incidence, risk factors, and outcomes of AKI among neurocritical patients at high altitude. Methods Adult neurocritical patients admitted to the ICU of People’s Hospital of Xizang Autonomous Region (3,650 m) from January 2022 to February 2024 were retrospectively analyzed. AKI was defined using the 2012 KDIGO serum creatinine criteria. Multivariable logistic regression identified independent predictors, and hemoglobin levels were modeled with linear spline regression. Propensity score matching (PSM) was performed to evaluate the impact of specific interventions. Results Among 390 patients, 83 (21.3%) developed AKI within 7 days of ICU admission. Independent predictors included older age (OR = 1.058 [1.032–1.087], p < 0.001), higher body mass index (OR = 1.130 [1.030–1.242], p = 0.010), lower Glasgow Coma Scale score (OR = 0.859 [0.795–0.924], p < 0.001), hypotension (OR = 2.659 [1.257–5.579], p = 0.010), contrast agent (OR = 2.480 [1.263–4.867], p = 0.008), high-dose loop diuretics (OR = 1.985 [1.117–3.555], p = 0.020), and baseline eGFR (OR = 1.033 [1.015–1.052], p < 0.001). Both low (<100 g/L, OR = 4.707 [1.020–19.686], p = 0.037) and high (>180 g/L, OR = 2.031 [1.093–3.790], p = 0.025) hemoglobin levels increased AKI risk. PSM sensitivity analysis confirmed the association of high-dose loop diuretics with AKI (OR = 2.009, p = 0.011), while the effect of contrast agents lost significance after matching (OR = 1.505, p = 0.215). Patients with AKI had higher in-hospital mortality (34.9% vs. 11.7%, p < 0.001) and greater hospitalization costs (148.5 vs. 119.4 × 1,000 CNY, p = 0.001). Conclusion At high altitude, AKI is common in neurocritical patients and independently associated with adverse outcomes. Beyond traditional risk factors, altitude-related erythrocytosis significantly contribute to AKI risk, suggesting that tailored renal protection strategies are necessary in high-altitude neurocritical care.