STUDY CHARACTERISTICS
The characteristics of our included studies are summarised inTable 1 . In most cases, patients were commenced on CRRT for acute kidney injury or known end-stage renal disease with multi-organ failure. 16 out of 24 patients were treated with CVVHF with 8 other patients treated with CVVHDF. Two patients [25,34] were receiving simultaneous extracorporeal membrane oxygenation (ECMO). In most patients (17 out of 24) a 1,000mg twelve-hourly dose of levetiracetam was administered as intravenous bolus infusions. One patient received enteral levetiracetam.
Sampling strategies across studies varied significantly. Pre-filter, post-filter and effluent samples were collected in four studies while in three studies only plasma samples (either peak or trough levels) were taken. In most studies, levetiracetam levels were not taken until steady state had been achieved. One compartmental modelling for pharmacokinetic analysis was used in three studies [25, 34, 35] , while Kalaria et. al used a non-compartmental approach.
The recommended delivered dose in CRRT varies but is considered to be between 20 – 35 ml/kg/hr. The median delivered dose in these studies ranged from 26.7 – 37.1 ml/kg/hr with significant variation seen in Chappell et al. and Kalaria et al. Blood flow rates ranged from 180 – 250 ml/min and were broadly consistent across studies. The majority of patients were either anuric or oliguric (defined as urine output <400ml in 24 hours) but it should be noted that these data were not collected by Chappell et al.