Lactate Clearance of the Adsorber Cytosorb® in Critically Ill Patients: A Post-Hoc Analysis of the Cyto-SOLVE Trial

<b>Background/Objectives</b>: Patients with shock suffer from hyperlactatemia, which can lead to endothelial dysfunction. The use of the adsorber Cytosorb^® (CS) is recommended in these patients as it may contribute to higher lactate clearance and hemodynamic stabilization. However, it is unclear whether CS can directly adsorb lactate and can therefore increase lactate clearance. <b>Methods</b>: The Cyto-SOLVE trial included patients undergoing continuous kidney replacement therapy combined with CS application. Patients with a lactate concentration > 2 mmol/L and measurements of lactate pre- and post-adsorber, as well as measurements in the blood 10 min and 1, 3, 6, and 12 h after initiation were selected. Lactate clearance was calculated using the following formula: bloodflow_(mL/min) × concentration_pre-post/concentration_pre. A <i>t</i>-test was used with the collected samples. Changes in the lactate concentration and vasopressor requirement were recorded before initiation and at the end of therapy. <b>Results</b>: Sixty-five lactate concentrations were measured pre- and post-CS application, as well as in patients' blood, in a total of 14 patients (median age of 52 years, 10 males, median SAPS-II 67). There was no significant change in the lactate concentration pre- and post-CS application (mean pre-CS: 6.7 mmol/L, mean post-CS: 6.9 mmol/L, RR: -0.2, 95% confidence interval (CI): -0.4-0.1, <i>p</i> = 0.13, Cohen's d: 0.90). The mean lactate clearance was -6 mL/min (standard deviation (SD): 21 mL/min), with no correlation with the initial lactate concentration or blood flow. In contrast, the mean lactate clearance measured using the dialyzer was 39 mL/min (SD: 28 mL/min). When comparing values before and after treatment, no significant change was observed in the lactate blood concentrations (mean of 9.0 vs. 8.5 mmol/L), nor in the requirement for vasopressin (median of 1.9 vs. 1.8 IE/h) or norepinephrine (mean of 2.7 vs. 2.6 mg/h). <b>Conclusions</b>: The adsorber CS cannot directly adsorb lactate, unlike kidney replacement therapy. Therefore, it is not suitable for achieving faster extracorporeal lactate elimination. Understanding the adsorption spectrum is of great relevance and should be considered when using CS in clinical practice.