OTAC: Optimization of Antibiotic Therapy in Critically ill Patients. Using beta-lactam antibiotics by continuous...

To determine the percentage of patients given standard doses of piperacillin/tazobactam or meropenem by continuous  infusion who achieved the target pharmacokinetic/pharmacodynamic  (PK/PD) index, which was defined as free concentrations four times  more than the minimum inhibitory concentration (CMI) for 100% of the  dosing interval (100% fT≥ 4 x MIC).

Preliminary data from a larger prospective clinical study  analysing the PK/PD behaviour of β-lactams antibiotics continuous  infusion (CI) in critical patients. The study was conducted in the  intensive care units of a tertiary university hospital for adults (June  2015-May 2017). Inclusion criteria: normal renal function (glomerular  renal function (GFR) CKD-EPI formula ≥ 60 mL/min/1.73 m2) and  treatment with standard dose β-lactams CI. Concentrations at steady  state (Css) conditions were determined using UHPLC-MS/MS. We  selected the highest susceptible MIC for all likely organisms according to  European Commitee on Antimicrobial Susceptibility Testing's (i.e.  piperacillin/tazobactam: 8 mg/L for enterobacteriaceae and 16 mg/L for  Pseudomonas aeruginosa; meropenem: 2 mg/L for any  microorganism). In addition, a subanalysis of patients was conducted using actual MIC values.

61 patients were enrolled (25 to meropenem and 36 to  piperacillin/tazobactam). Average age was 59 (15) years and median  GFR rate was 95 mL/min/1.73 m2 (83-115). Median meropenem and  piperacillin free concentrations were 16 mg/L (11-29) and 40 mg/L (21- 51), respectively. 88% of patients treated with meropenem reached the  PK/PD target, without differences between both microorganisms. For  piperacillin/tazobactam, 61% and 11% of patients reached the target,  with enterobacteriaceae and Pseudomonas as suspected  microorganisms, respectively. The pathogen was isolated in 35 (57%)  patients: 94% reached the target PK/PD, without differences between  both antibiotic therapies.

Standard doses of meropenem CI are sufficient to  achieve a PK/PD target of 100% fT≥ 4 x MIC in suspected infections  with high MICs (Pseudomonas aeruginosa or enterobacteriaceae).  However, higher doses of piperacillin/tazobactam could be considered to  achieve this goal. In patients with isolated microorganisms, a  standard dose of both antibiotic therapies would be sufficient to achieve  the target. Therapeutic drug monitoring is highly recommended for  therapeutic optimization.