The Journal of ExtraCorporeal Technology No 56-4 | Page 31

A . J . Whelan et al .: J Extra Corpor Technol 2024 , 56 , 167 – 173 169

Figure 1 . Schematic of ECMO and CRRT ex vivo circuit configurations : A . ECMO circuit configuration including oxygenator , reservoir , and pump . B . CRRT circuit configuration including reservoir and PrisMax ( pump , hemofilter , thermax and fluids ). PBP = pre-blood pump , EFF = effluent , DIA = dialysate , REP = replacement fluid .

Table 1 . ECMO and CRRT circuit components and parameters .

a Polymethylpentene fibers ; b Bioline coating : covalently bonded recombinant human albumin and heparin ; c Polyvinyl chloride ; d Smart-X

coating : tribloc copolymer ( polycaprolactone-polydimethylsiloxane-polycaprolactone ) e PolyarylEtherSulfone fibres , plasticized polyvinyl chloride tubing ; f Ethylene vinyl acetate ; g Polyurethane . PBP : pre-blood pump flow rate ; BFR : blood flow rate ; PFR : patient fluid removal flow rate ; DIA : dialysate volumetric flow rate ; REP : replacement fluid flow rate .

Control samples were dosed with milrinone at time = �5 min , gently rotated to ensure adequate mixing , and then placed in a water bath for the duration of the experiment . At each sample time point , the tube was removed from the water bath , gently inverted five times , and the sample was collected .

Milrinone assay

Calibrators and quality control samples were prepared using standard reference materials . Milrinone and the internal standard ( milrinone-d3 ) were obtained from Cayman Chemical ( Cat # 13357 and 25429 , respectively ). Calibration standards were prepared in Mass Spect Gold Human Plasma ( Cat #: MSG7000 ; Golden West Diagnostics ) and were used to generate an external 7-point calibration curve ( 2 , 6 , 13.5 , 30 , 75 , 300 , and 600 ng / mL ) using linear regression ( 1 / x weighting ) to plot the peak area ratio versus concentration . The calibration curves were linear ( R 2 0.99 ) over the analytically measurable range ( AMR ) of 2 – 600ng / mL . Within-run precision of quality control samples ( QCs , n = 3 ) was determined at 3 different concentrations in plasma ( Low QC : 4.5 ng / mL , Mid QC : 45 ng / mL , High QC : 450 ng / mL ) were observed at 6.3 %, 14.2 %, and 7.3 %, respectively . Quantitative determination of milrinone in plasma and effluent samples was determined by multiple reaction monitoring ( MRM ) LC-MS / MS ( Agilent Infinity II 1290 – Sciex QTrap 6500 +). MRM was performed in positive electrospray ionization mode by monitoring the following transition ions : milrinone ( quantifier : 212.05 m / z > 142.0 m / z ; qualifier : 212.05 m / z > 104.0 m / z ; milrinone-d3 ( IS ): 215.07 m / z > 142.1 m / z ).

Milrinone recovery over time

Due to slight differences in initial concentrations for circuit and control experiments , concentrations were normalized using drug percent recovery using the following equation :

Recovery ð% Þ ¼ C t

100 ð1Þ

C ref

where C t is the concentration at time t and C ref is the initial concentration of milrinone at time 1 min .

Saturation coefficient

The saturation coefficient and transmembrane clearance were calculated for the CRRT experiments using paired plasma and effluent samples with the following equations :

S aðHDFÞ ¼ C eff

C p

Q eff ¼ Q PBP þ Q REP þ Q PFR þ Q DIA ð2Þ

ð3Þ

CL CVVHDF ¼ Q eff S aðHDFÞ ð4Þ

where S a ( HDF ) is the saturation coefficient for hemodiafiltration and C eff and C P are the effluent and plasma milrinone concentrations , respectively . Q eff , Q PBP , Q REP , Q PFR and Q DIA are the effluent , pre-blood pump , replacement fluid , patient fluid removal , and dialysate volumetric flow rates , respectively . CL CVVHDF is the transmembrane clearance .