Endothelial dysfunction in critically ill patients: the effect of haemofiltration
Objectives: To examine the effect of a single episode of continuous venovenous haemofiltration (CVVH) on indicators of endothelial injury and the protein C/S system in critically ill patients. Design: Observational study. Setting: University teaching hospital intensive care unit. Patients: 12 critically ill patients with acute renal failure receiving their first episode of CVVH. Interventions: Blood samples were collected prior to starting CVVH and at 15 min and 1, 3–4, 8–12, and 24 h, and at 24-h intervals thereafter until the filter clotted. Measurements and results: Soluble tissue factor, soluble thrombomodulin, E-selectin and endothelin-1 were measured as indicators of endothelial injury. Changes in the protein C/S system were assessed by measurement of protein C (PC) and both free and total protein S (PS). Levels of PC and both free and total PS were subnormal in 6 and 11 patients, respectively, prior to CVVH, but there were no further changes during CVVH. Levels of tissue factor, thrombomodulin, E-selectin, and endothelin-1 were raised prior to haemofiltration in 9, 10, 9 and 9 patients, respectively. There were further increases during CVVH in at least one, but not all, of the markers of endothelial injury in most patients. There was no consistency between the changes in different markers of endothelial injury during haemofiltration in individual patients. Conclusions: The PC/PS system and endothelial integrity is compromised in critically ill patients prior to haemofiltration, but a single episode of CVVH has little effect on the PC/PS system. The increase in markers of endothelial dysfunction seen during CVVH is more likely to be related to the underlying condition of the patient rather than any specific consequence arising from the technique itself.
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