4CPS-055 Impact of extracorporeal membrane oxygenation circuit on fentanyl pharmacokinetics in critically ill patients

<h3>Background and Importance</h3> Fentanyl’s lipophilicity and protein binding may contribute to a sequestration of the drug in the extracorporeal membrane oxygenation (ECMO) circuit, which could impact to pharmacokinetic and response in critically ill patients. <h3>Aim and Objectives</h3> To assess the impact of ECMO circuit on the plasma concentration (Pk) of fentanyl in critically ill patients. <h3>Material and Methods</h3> Observational, prospective, multidisciplinary, cohort study. Adult critically ill patients in treatment with standard fentanyl perfusion for more than 48h between 2020–2021 were included. Demographical and clinical variables, concomitant treatments(sedative/CYP3A4 inducer-inhibitor metabolism), mechanical ventilation (VM) and continuous renal replacement techniques (CRRT) were collected. Pk was determined at 24h (pk1) and 48h (pk2) after the start of perfusion by ultra-high performance liquid chromatography-mass spectrometry. Pain was evaluated with Escala de conductas indicadoras de dolor (ESCID score). Two cohorts were differentiated: ECMO and non-ECMO. Variables were expressed as mean (standard deviation) or median(range)/absolute (relative) frequency. The Student´s t-test/Mann-Whitney test was used to compare quantitative variables, Pearson´s Chi-squared/Fisher´s exact test for qualitative (STATAv.14.2). Statistically significant was considered if p≤0.05 <h3>Results</h3> Seventy-six patients were included of 55.49 (13.52) years; 54 (71.05) male; 13 (17.11) with ECMO support. No significant differences for clinical variables (SAPS3, predisposing conditions, body mass index, liver or renal function) were found, however patients in the ECMO group were younger (48.68vs56.90, p=0.045), all male (p=0.015). Median fentanyl infusion rate was 0.64 (0.14) in ECMO vs 0.53(0.03) mcg/kg/h in non-ECMO p=0.212) during first 24h, 0.41(0.05) vs 0.49 (0.04) mcg/kg/h (p=0.444) during next 24h. Plasma levels at 24h were higher in non-ECMO group: pk1: 3.88 (11.01) vs2.07(0.99) ng/mL, but no significative differences were found (p=0.557), nevertheless higher levels was reached at 48h in ECMO: pk2: 1.92 (1.24) vs2.41(1.29) ng/mL, p=0.261. No differences were found with regarding to the use of CRRT, MV or concomitant treatment. No differences on the ESCID scale were found (at 24h): non-ECMO 0(0–5)vs ECMO 0 (0–3), p=0.463; (at 48h): non-ECMO 0 (0–4) vs ECMO 0 (0–3),p=0.774 because most of the patients had correct pain control (ESCID&lt;3): 24h: 96%;48h: 95.52% <h3>Conclusion and Relevance</h3> In our series, the use of ECMO had no significant impact on fentanyl Pk during the first 48h. Using a standard perfusion in patients on extracorporeal support to dose according to the response guided by the ESCID scale is safe to achieve adequate pain control. <h3>References and/or Acknowledgements</h3> <h3>Conflict of Interest</h3> No conflict of interest