Insufficient penetration of systemic vancomycin into the PermCath lumen

Background. Catheter infection is a major cause of morbidity and catheter l oss in chronic haemodialysis patients. There has been a large discrepancy i n the catheter salvage rate, after an episode of documented bacteraemia, wh ether the patients receive systemic antibiotic alone or systemic antibiotic s concomitant with 'antibiotic-lock technique' (20 30% vs 100%, respectivel y). To test the hypothesis that vancomycin may not adequately penetrate int o the lumen of the catheter, despite therapeutic plasma levels, a series of in-vivo, ex-vivo, and in-vitro experiments were performed. Methods. We compared serum and intralumenal (0.3-0.5 ml aspirate from venou s port of the catheter) vancomycin concentrations in 24 chronic haemodialys is patients, with documented bacteraemia, who had received Drier systemic v ancomycin therapy with 14 similar patients who had additionally received 'v ancomycin-lock technique' (100 mu g/ml of vancomycin in heparin solution) a fter each haemodialysis session. Results, Despite serum vancomycin concentration of similar to 17 mu g/ml in each group, the vancomycin concentration in the venous hub of the catheter was only 0.2+/-0.6 mu g/ml in the former group, in sharp contrast to 125.6 +/-13 mu g/ml in the latter group. In the ex-vivo experiment, four uninfect ed PermCaths which had been removed were immediately fixed and studied with scanning electron microscopy. No cellular or fibrin barrier could be found at the terminal pore of the catheter interfering with the diffusion of van comycin from plasma into the catheter lumen. In the in-vitro experiments, t hree PermCaths filled with standard heparin solution were incubated for 48 h in 100 ml of plasma containing 20 mu g/ml of vancomycin. Vancomycin conce ntration was measured in 0.3-0.5 ml solution aspirated from each port of th e catheters. Vancomycin concentration was 0.2+/-0.1 mu g/ml in the aspirate d samples. Finally, two PermCaths filled with the standard heparin solution were incubated for 48 h in 100 ml of plasma containing 20 mu g/ml of vanco mycin, after which the catheters were sectioned at 4-cm intervals. Only the distal 4 cm of the catheters had vancomycin concentrations of 2 and 5 mu g /ml, the remaining segments had levels less than or equal to 0.5 mu g/ml. Conclusion, Our results indicate that diffusion of vancomycin from plasma i nto the haemodialysis catheter is negligible. Thus, haemodialysis patients with central venous catheter who have to be treated for bacteraemia with sy stemic antibiotic therapy must always receive 'antibiotic-lock technique' o f the catheter after each haemodialysis session.