Perfusion variables and hemodynamic phenotypes during fluid removal via net ultrafiltration in continuous renal replacement therapy: a retrospective single-center cohort study.

BACKGROUND: Fluid removal could induce iatrogenic hypovolemia and impaired perfusion in critically ill patients. Aims of the study were to describe the occurrence of impairment in perfusion variables during fluid removal via net ultrafiltration with continuous renal replacement therapy, to analyze whether they enable to differentiate hemodynamic phenotypes, and to assess the relationship with mortality at day 30.

METHODS: A single-center, retrospective cohort study of critically ill adult patients of a cardiovascular and thoracic center. Patients had fluid overload, undergone continuous renal replacement therapy for acute kidney injury, and had an institutional de-resuscitation protocol combining intake restriction with a moderate net ultrafiltration. The occurrence of impairment in perfusion variables (mottling score, capillary refill time, arterial lactate and central venous oxygen saturation) was reported for each variable. Their association with mortality at day 30 was explored after adjustment on macrohemodynamic variables with logistic regression. The hemodynamic phenotypes were determined using hierarchical clustering on principal components from macrohemodynamic and perfusion variables.

RESULTS: A total of 99 patients were included between February 2021 and November 2023 (1258 measurement timepoints). Ninety-eight (99 %, 95 %CI 94 to 100 %) patients and 865 timepoints (69 %, 95 %CI 66 to 71 %) exhibited impairment in at least one perfusion variable. The cumulative value of mottling score > 0 was the only perfusion variable associated with mortality at day 30. Three hemodynamic phenotypes were differentiated, highlighting significant differences in macrohemodynamic variables, and perfusion parameters.

CONCLUSIONS: Impaired perfusion is highly frequent during fluid removal via net ultrafiltration.