Pharmacokinetics of cefazolin delivery via the cardiopulmonary bypass circuit priming solution in infants and children.

Our aim was to describe the pharmacokinetics of cefazolin in paediatric patients undergoing cardiac surgery with cardiopulmonary bypass (CPB) who received cefazolin for peri-operative surgical prophylaxis in addition to having cefazolin added to the CPB circuit priming solution. Secondary aims were to determine the pharmacodynamic exposure associated with the addition of cefazolin to the CPB priming solution and to assess whether a target cefazolin concentration range for the CPB priming solution could be identified. A multicentre, prospective, open-label pharmacokinetic study was carried out in children from birth to 16 years of age undergoing cardiac surgery. Forty-one patients met the inclusion criteria and accounted for 492 samples for analysis. Cefazolin concentrations were best described by a one-compartment model with weight as a covariate on the volume of distribution (Vd) with allometric scaling. The mean ± standard deviation (SD) total body CL for the birth-6 month cohort was 0.009 ± 0.006 mL/min/kg with a mean ± SD Vd of 0.59 ± 0.26 L/kg, the mean ± SD total body CL for the 7 month-3 year cohort was 0.01 ± 0.005 mL/min/kg with a mean ± SD Vd of 0.79 ± 0.15 L/kg, and the mean ± SD total body CL for the 4-16 year cohort was 0.007 ± 0.004 mL/min/kg with a mean ± SD Vd of 3.4 ± 0.94 L/kg. The median cefazolin loss in the CPB circuit ranged from 78% to 95% and the median patient cefazolin concentration after CPB circuit detachment ranged from 92 to 197 mg/L. These data demonstrate that mixing cefazolin in the CPB circuit priming solution was effective in maintaining cefazolin serum concentrations during surgery. If this practice is utilized, re-dosing of cefazolin during the CPB run and upon CPB circuit detachment is most probably not needed. Larger pharmacokinetic studies are warranted.

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