Do we meet the goal of pharmacokinetics and pharmacodynamics in critically ill patients receiving beta-lactam antibiotics?

Abstract

Introduction: critically ill patients have physiopathological changes that upset the concentrations of beta-lactam antibiotics. The aim was to determine if the doses of usual use in critically ill patients reach the concentrations associated with maximal activity and to establish the variables of PK/PD that are associated with suboptimal concentrations of antibiotic. Methods: prospective study conducted in an intensive therapy of adults in a period of 13 months. Patients who received cefazolin, ceftriaxone, ceftazidime or meropenem were included. Dosage of antibiotic concentration in plasma was performed at 50% of the dose interval. The concentration of free antibiotic was calculated and compared with the objective 50% fT>MIC and the objective 50% fT>MIC x 4 for susceptible microorganisms, according to CLSI criteria. The group of patients who met the 50% objective fT>MIC x 4 was compared with the one who did not, in terms of PK/PD variables. Results: 29 determinations and 55 comparisons were included. The objective 50% fT>MIC was reached in 92.7% of the cases and the target 50% fT>MIC x 4 was achieved in 61.8%. In the worst scenario, that is, considering the germ susceptible with MIC higher, only 48.3% of patients met the objective 50% fT>MIC x 4. Patients who did not reach the goal 50% fT>MIC x 4 had greater renal clearance than those who reached the goal (160 vs 108.5 ml/min/1.73m2, p=0.01). Conclusions: a large percentage of critically ill patients receiving beta-lactams do not reach the PK/PD goals recommended nowadays.