Identical complement concentrations in blood obtained from central venous catheters, arterial lines, and antecubital...

In vitro complement activation has been detected during passage of blood through tubing used in hemodialysis and cardiopulmonary bypass surgery, in addition to tubing being investigated for vascular grafts. Because tubing from arterial lines and central venous catheters are composed of similar materials and are used when blood is withdrawn from patients for complement assays, a study was undertaken to assess the degree of complement activation in blood obtained from these sites. Complement activation was determined by a terminal complement complex enzyme-linked immunosorbent assay (ELISA), C1rC1s-C1 inhibitor complex ELISA, and 50% complement hemolytic activity (CH50) assay. Blood simultaneously obtained from the arterial lines and central venous catheters had identical terminal complement complex, C1rC1s-C1 inhibitor complex, and CH50 levels when compared with blood withdrawn by antecubital phlebotomy. Because blood may be obtained from the arterial lines and central venous catheters for complement assays, the pain and possible bruising from antecubital phlebotomy could be eliminated. Furthermore, blood may now be withdrawn from indwelling catheters without fear of in vitro complement activation causing a misinterpretation of results.