Hemodialysis clearance of total and unbound lidocaine

The hemodialysis clearance and protein binding of lidocaine was determined in two acutely ill patients with end-stage renal disease. Patient A was a 74-year-old white man admitted for severe thrombocytopenia; lidocaine was started to control ventricular tachycardia. Patient B was a 66-year-old white man admitted for a myocardial infarction (MI); prophylactic treatment with lidocaine was begun after a second MI. Lidocaine hemodialysis clearance was evaluated during a five-hour dialysis procedure. Paired arterial and venous blood samples for lidocaine concentrations were collected at the midpoint of each hour of dialysis. Before dialysis and two hours after dialysis, venous samples were collected and assayed for alpha-1-acid glycoprotein (AAG) and lidocaine. The hemodialysis clearance of total and unbound lidocaine was calculated. The total amount of lidocaine removed was 8.9 and 12.5 mg for patients A and B, respectively. These amounts represented the removal of 5.6 and 2.8% of the total lidocaine dose administered to patients A and B, respectively, during the dialysis procedure. For patient A, the mean plasma dialysis clearance (Clp) was 28.2 +/- 6.3 ml/min for total lidocaine and 41.3 +/- 15.6 ml/min for unbound lidocaine. The Clp could not be calculated for patient B. The mean dialysate clearance (Cld) of total lidocaine was 28.6 +/- 7.8 and 26.3 +/- 6.5 ml/min for patients A and B, respectively. The Cld of unbound lidocaine was 42.7 +/- 6.7 and 44.5 +/- 9.9 for patients A and B, respectively. Although both patients A and B had substantial elevations in AAG concentrations (254 and 247 mg/dl, respectively), they exhibited high lidocaine unbound fractions of 0.55 and 0.68 before dialysis. The lidocaine unbound fraction was further increased in patient A after fat emulsion infusion to 0.80 and in patient B after heparin administration to 0.90. The clearance of lidocaine by hemodialysis in these two patients was negligible and clinically unimportant. No dose adjustment or supplementation was required after hemodialysis.