Association between estimated plasma volume status and 90-day outcomes in patients with acute-on-chronic liver failure treated with artificial liver support system: a retrospective cohort study

Water and electrolyte imbalance is a common complication of liver failure. Estimated plasma volume status (ePVS) has shown significant prognostic value in conditions characterized by fluid redistribution and inflammation; however, its association with clinical outcomes in acute-on-chronic liver failure (ACLF) remains incompletely understood. This study adopted a retrospective cohort design in patients meeting the COSSH ACLF criteria who were treated with ALSS. The relationship between ePVS and 90-day clinical outcomes was examined using Cox regression, restricted cubic splines (RCS), and the Fine-Gray competing risk model. This study was reported following the STROBE guidelines. The 90-day transplant-free and overall survival rates among the 258 eligible patients were 58.5% and 66.3%, respectively. The ePVS in 90-day transplant-free survivors was significantly lower than that in patients who underwent transplant or died [5.33 (4.74–6.20) vs. 5.78 (4.74–6.76), P = 0.036]. In the fully adjusted Cox model, a higher ePVS showed a marginally significant association with an increased risk of 90-day overall mortality [adjusted HR: 1.12 (95% CI: 1.01–1.26), P = 0.048]. When using the cutoff value of 6.30, patients with ePVS > 6.30 had significantly poorer 90-day transplant-free survival [adjusted HR for transplant or death: 1.69 (95% CI: 1.10–2.60), P = 0.017] and 90-day overall survival [adjusted HR for death: 1.91 (95% CI: 1.19–3.08), P = 0.008] compared to those with ePVS ≤ 6.30. This association remained statistically significant in the Fine-Gray competing risks analysis, with liver transplantation treated as a competing event [adjusted subdistribution HR: 1.77 (95% CI: 1.05–2.99), P = 0.031]. An elevated ePVS showed a marginally significant association with worse 90-day prognosis in COSSH ACLF patients receiving ALSS therapy, although the borderline significance of some estimates and the single-center design warrant cautious interpretation.