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Specialist in Nephrology Nephrology Department Hospital General Universitario de Elche Elche (Alicante), Spain
Specialist in Hospital Pharmacy Pharmacy Service Hospital de Sagunto Avda Ramon y Cajal s/n Sagunto 46520 (Valencia), Spain fax 34 962659428 jborrasb{at}sefh.es
Specialist in Nephrology Nephrology Section Hospital General Universitario de Elche
Specialist in Hospital Pharmacy Pharmacy Service Hospital General Universitario de Elche
Specialist in Nephrology Nephrology Section Hospital General Universitario de Elche
Published Online, November 28, 2006. www.theannals.com, DOI 10.1345/aph.1H193
Case Report. A 48-year-old woman with diffuse proliferative lupus glomerulonephritis developed end-stage renal disease. Two months prior to admission, she had begun hemodialysis. Hemodialysis sessions, each 3 hours long, were performed 3-4 days/wk using a low-flux polysulphone capillary of 1.8 m2. She was empirically treated with intravenous vancomycin 1 g for 7 days due to fever with negative cultures. Using the Abbottbase Pharmacokinetic Systems bayesian program, the patient's vancomycin pharmacokinetic parameters were calculated. Before the second hemodialysis session, vancomycin plasma concentrations were 7.71 µg/mL. Based on this pharmacokinetic value, vancomycin 1 g, administered intravenously every 5 days, vancomycin 1 g/5 days was prescribed.
She was admitted to the hospital with Coombs-negative hemolytic anemia and thrombocytopenia that was refractory to corticosteroids and cyclophosphamide. Laboratory studies revealed hemoglobin 6.7 g/dL, leukocytes 12.2 x 103/mm3, urea 216 mg/dL, creatinine 7.21 mg/dL, and albumin 3.82 g/dL. Anticardiolipin and lupus anticoagulant were negative. All other biochemistry values determined were normal, and serology testing for infectious agents was negative. Plasmapheresis was initiated. Hemodialysis sessions were scheduled every 48 hours, alternating days with plasmapheresis sessions. Plasma separation was done by a continuous blood flow system using a capillary plasma filter. A mean plasma removal rate of 35 mL/min was achieved through a left arteriovenous fistula. Mean plasma volume exchange was 3.1 L per session, corresponding to one volume of the circulating plasma calculated for hematocrit and weight. Fresh frozen plasma, equal to the amount of plasma removed, was administered as replacement.
After the eighth plasmapheresis session, the patient was diagnosed with subcutaneous tunnel infection of the central catheter, and it was removed. Methicillin-resistant Staphylococcus aureus (MRSA) was identified by blood and catheter tip cultures. Intravenous vancomycin 1 g, administered intravenously every 5 days, was started. Serum vancomycin concentrations were obtained immediately prior to and 2 hours after plasmapheresis. Table 1 shows the effect of plasmapheresis on serum vancomycin concentrations. The concentrations were reduced on average by 48.5% following each plasmapheresis session. To compensate for this reduction, vancomycin 250 mg was administered intravenously after each plasmapheresis session. After the fourteenth plasma exchange session, plasmapheresis was stopped. Hemodialysis was continued, and vancomycin plasma concentrations were obtained before and 3 hours after hemodialysis (Table 1). On day 43, when MRSA cultures were negative, vancomycin treatment was discontinued.
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Discussion. Plasmapheresis removes drugs that have a low volume of distribution and that are highly protein bound. Vancomycin has a volume of distribution that ranges from 0.4 to 1.1 L/kg. After an intravenous dose of vancomycin is administered, 55% of the drug is bound to plasma proteins.1 It is plausible that plasmapheresis could remove a significant amount of vancomycin. However, there are conflicting reports in the literature regarding the removal of vancomycin during plasmapheresis.2-5 The results of a study by McClellan et al.2 showed that the amount of vancomycin removed during a single one volume plasmapheresis session represented less than 10% of the administered dose. Osman and Lew4 reported an average of 27% vancomycin removed following plasmapheresis. That amount of vancomycin removal during plasmapheresis may be clinically significant. This larger reduction in serum vancomycin concentrations could not be explained by a larger volume of plasma being removed compared with the volumes reported in other studies. To rule out a redistribution phenomenon, vancomycin serum concentrations had been determined in the study by Osman and Lew 2 hours after the procedure.
Ours is the third reported case that demonstrates a potential increase in vancomycin elimination during plasmapheresis. It is advisable to obtain postplasmapheresis vancomycin serum concentrations. To achieve therapeutic vancomycin concentrations, dosage adjustment may be necessary in patients who receive plasmapheresis
References
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