Goncalves-Pereira and Povoa meta-reviewed 57 reviews of pharmacokinetics of common beta-lactam antibiotics (piperacillin, meropenem, cefepime, ceftazidime, etc.) on patients in ICUs.

The results were troubling or at least confusing: studies reported wide variability in pharmacokinetics of beta-lactam antibiotics in critically ill patients, with volume of distribution and drug clearance varying more than 2-fold for the same drugs in similar patient populations.

The net result is that the time spent above minimum inhibitory concentration (T>MIC) -- i.e., the expectation that therapeutic levels are present at usual dosing -- was totally unpredictable. Tissue penetration was also compromised in patients with septic shock.

Their conclusion: Check levels often and dose drugs accordingly. My conclusion: get to know and love your friendly neighborhood ICU pharmacist.

Joao Goncalves-Pereira and Pedro Povoa. Antibiotics in critically ill patients - a systematic review of the pharmacokinetics of beta-Lactams. Critical Care 2011, 15:R206. FREE FULL TEXT