In ICU setting, most empiric antibiotic treatments include a combination of anti-Gram-positive and -negative bacteria, according to the different clinical scenarios. Thus, there are different possible regimen combinations, including two different drugs. We considered meropenem/linezolid (or daptomycin) as the drugs of choice in septic shock empiric treatment.
The motivation for the use of HA380 was to remove inflammatory cytokines. Only one HA 380 application (=12 hours) will be evaluated in this study.
Hemadsorption will be performed using a BBraun OMNI machine: a Jafron HA380 cartridge is assembled in series with a BBraun OMNI PLUS 'open' filter.
Hemadsorption lasts from 2 to 12 hours maximum, at the end the cartridge can be disassembled and CRRT treatment alone can be carried forward.
CRRT is performed according to the Omni machine BBraun protocol . CVVHD is the technique of choice because the diffusion method guarantees membrane stability.
A predilution Trisodium Citrate 4% infusion is performed, and filter anticoagulation is monitored via post filter blood samples with a target post filter ionized calcium (iCa+) values between 0,2- and 0,4 mmol/L. The citrate plasmatic starting dose is 4 mmol/L: the Omni machine automatically adjusts citrate flow in the predilution pump according to blood flow value, and vice versa. Post filter iCa+ values are checked 5 minutes after treatment institution and 5 minutes after every citrate's dose change; periodic checks are performed every 6 to 8 hours.
Blood flow varies according to patients' weight, dialysate to blood flow (expressed in ml/h) is kept constant in a 1:3 ratio, a table with reference values is provided by the manufacturer. A calcium free dialysate solution with an HCO3 concentration \< 25 mmol/l is used.
A Calcium Chloride infusion is performed to restore a normal plasmatic iCa+ concentration. Calcium infusion takes place directly in the Omni circuit's venous line via a dedicated tubing. Starting calcium infusion dose is 1,7 mmol/l, patient's plasmatic iCa+ levels are checked before treatment's start, 30 minutes and 2 hours after treatment's start. Routine monitoring samples are performed every 6 to 8 hours.
When antibiotic treatment includes a loading dose, blood samples will be taken one hour after starting the continuous infusion.
Samples will be taken pre cartridge, post cartridge (pre filter) and after filter at baseline (at least 30 minutes after the beginning of CRRT treatment) and after 4-8 and 12 hours, according to the theoretical cartridge saturation time.
Samples will be processed at the same time, at the end of the recruitment time.
The samples will be processed by a company with expertise in antibiotic TDM. To ensure the highest standards of accuracy and reliability in our data, blood samples collected during this study will be evaluated using state-of-the-art Liquid Chromatography - Tandem Mass Spectrometry (LC-MS/MS) techniques. This advanced analytical method allows for the precise quantification and identification of biochemical compounds within complex biological matrices, providing unparalleled sensitivity and specificity. Following collection, blood is centrifuged to separate serum or plasma, which is then aliquoted to avoid degradation from freeze-thaw cycles. Aliquots are stored at -80°C to preserve sample integrity until analysis. This meticulous pre-analytical preparation ensures that all samples can be analyzed simultaneously, reducing analytical variability, and maintaining the quality of the samples for LC-MS/MS analysis.
Sample size calculation
To assess the variability in concentration levels in patients undergoing Continuous Renal Replacement Therapy (CRRT), a study will be conducted to compare the concentration levels in the blood before and after passing through the CRRT filter. Given the preliminary nature of this study and logistical limitations, the sample size will be set at 10 patients. This sample size is determined based on the ability to detect a clinically significant difference in concentrations of at least 12.53 units, with an assumed standard deviation of 10 units, while maintaining a significance level (α) of 0.05 and a study power (1-β) of 80%. This configuration ensures that the study has the capacity to identify significant differences of relevant magnitude, despite the relatively small number of participants. The decision to limit the sample size to 10 subjects reflects a balance between operational feasibility and the goal of obtaining valid and informative statistical results.
