Pharmacokinetics in ECMO Patients: Dosing and Monitoring of Antibacterials

A systematic review data indicate that extracorporeal membrane oxygenation (ECMO) seldom drives antibacterial pharmacokinetic variability — dosing decisions should reflect sepsis and organ dysfunction rather than circuit parameters.

Across population pharmacokinetic studies, antibacterial exposure varied predictably with critical-illness covariates: renal function, fluid shifts, and extracorporeal renal replacement therapy explained most between-patient variability. ECMO-specific parameters (mode, flow, oxygenator type) had limited consistent impact. Secondary, mechanistic modifiers included drug adsorption to tubing and oxygenators, sequestration of highly lipophilic or protein-bound drugs, and altered free fraction from hypoalbuminemia.

In practice, that evidence reframes dosing logic toward an initial correction for expanded volume of distribution and then physiology-guided maintenance. Give higher or weight-based loading doses for hydrophilic agents (for example, many beta-lactams and aminoglycosides) when extracellular volume is increased. After the loading dose, adjust maintenance regimens based on objective changes in clearance — notably augmented renal clearance or progressive renal failure — rather than on ECMO settings alone.

When available, routine therapeutic drug monitoring (TDM) converts PK uncertainty into individualized targets. TDM offers the best return for agents with narrow therapeutic indices or well-defined PK–PD targets: vancomycin and aminoglycosides consistently benefit from concentration-guided strategies, and beta-lactam TDM is useful where feasible. Sample early after the loading dose or target troughs for concentration-dependent drugs; for time-dependent agents, use steady-state or trough sampling and repeat after renal-function changes, circuit exchanges, or dose adjustments.

Key Takeaways:

• ECMO itself rarely dictates antibacterial PK changes; critical-illness covariates now explain most variability — shift focus from circuit parameters to patient physiology.
• Adults on ECMO with sepsis, altered volume status, or changing renal function are most affected; those receiving concurrent renal replacement therapy are at particular risk for exposure variability.
• Move toward individualized loading doses and physiology-guided maintenance, supported by routine TDM for high-risk agents to optimize exposure and anticipate dose adjustments as organ function or circuit events evolve.