The adsorption of vancomycin by polyacrylonitrile, polyamide, and polysulfone hemofilters

Different distances between central venous catheter tips can affect antibiotic clearance during continuous renal replacement therapy

BACKGROUND

The aim of this experimental study was to elucidate whether different distances between central venous catheter tips can affect drug clearance during continuous renal replacement therapy (CRRT). Central venous catheters (CVCs) are widely used in intensive care patients for drug infusion. If a patient receives CRRT, a second central dialysis catheter (CDC) is required. Where to insert CVCs is directed by guidelines, but recommendations regarding how to place multiple catheters are scarce. There are indications that a drug infused in a CVC with the tip close to the tip of the CDC, could be directly aspirated into the dialysis machine, with a risk of increased clearance. However, studies on whether clearance is affected by different CVC and CDC tip positions, when the two catheters are in the same vessel, are few.

METHODS

In this model with 18 piglets, gentamicin (GM) and vancomycin (VM) were infused through a CVC during CRRT. The CVC tip was placed in different positions in relation to the CDC tip from caudal, i.e., proximal to the heart, to cranial, i.e., distal to the heart. Serum and dialysate concentrations were sampled after approximately 30 min of CRRT at four different positions: when the CVC tip was 2 cm caudally (+ 2), at the same level (0), and at 2 (- 2) and 4 (- 4) cm cranially of the tip of the CDC. Clearance was calculated. A mixed linear model was performed, and level of significance was set to p < 0.05.

RESULTS

Clearance of GM had median values at + 2 cm, 0 cm, - 2 cm and - 4 cm of 17.3 (5.2), 18.6 (7.4), 20.0 (16.2) and 26.2 (12.2) ml/min, respectively (p = 0.04). Clearance of VM had median values at + 2 cm, 0 cm, - 2 cm and - 4 cm of 16.2 (4.5), 14.7 (4.9), 19.0 (10.2) and 21.2 (11.4) ml/min, respectively (p = 0.02).

CONCLUSIONS

The distance between CVC and CDC tips can affect drug clearance during CRRT. A cranial versus a caudal tip position of the CVC in relation to the tip of the CDC led to the highest clearance.

Contribution of diafiltration and adsorption to vancomycin clearance in a continuous hemodiafiltration circuit model in vitro

BACKGROUND

Vancomycin (VCM) is eliminated mainly by diafiltration under continuous hemodiafiltration (CHDF), but the contribution of adsorption to CHDF clearance (CL_CHDF ) of VCM using a polyacrylonitrile and sodium methallyl sulfonate copolymer membrane coated with polyethylenimine (AN69ST) or a polymethylmethacrylate (PMMA) membrane is unknown. This study sought to investigate the contribution of diafiltration and adsorption to the CL_CHDF of VCM using AN69ST and PMMA membranes in vitro.

METHODS

An in vitro CHDF circuit model was developed. The initial concentration of VCM was 50 μg/mL and human serum albumin (HSA) was prepared at a concentration of 0, 2.5, or 5.0 g/dL. The effluent flow rate (Qe) was set at 800, 1500, or 3000 mL/h. The CL_CHDF , diafiltration rate, and adsorption rate of VCM were calculated.

RESULTS

Total CL_CHDF of VCM using the AN69ST membrane increased and decreased with increasing Qe and HSA concentration, respectively. Diafiltration and adsorption rates were 82.1 ± 9.8% and 12.1 ± 6.1% under all conditions, respectively. Total CL_CHDF using the PMMA membrane increased with increasing Qe. Diafiltration and adsorption rates were 89.2 ± 20.4% and 4.6 ± 17.0% under all conditions, respectively. The observed CL_CHDF values significantly correlated with the predicted CL_CHDF , calculated according to a previous study as the product of Qe and the plasma unbound fraction.

CONCLUSIONS

Diafiltration predominantly contributed to CL_CHDF of VCM using AN69ST and PMMA membranes. When diafiltration rather than adsorption mainly contributes to the CL_CHDF of VCM, the CL_CHDF could be predicted from the Qe and HSA concentration, at least in vitro.

Adsorption of vancomycin, gentamycin, ciprofloxacin and tygecycline on the filters in continuous renal replacement therapy circuits: in full blood in vitro study

The aim of this study was to assess the in vitro adsorption of antibiotics: vancomycin, gentamicin, ciprofloxacin and tigecycline on both polyethyleneimine-treated polyacrylonitrile membrane of AN69ST filter and polysulfone membrane of AV1000 filter using porcine blood as a model close to in vivo conditions. The porcine blood with antibiotic dissolved in it was pumped into hemofiltration circuit (with AN69ST or AV1000 filter), ultrafiltration fluid was continuously returned to the reservoir containing blood with antibiotic. Blood samples to determine antibiotic concentrations were taken at minutes 0, 5, 15, 30, 45, 60, 90 and 120 from the pre- blood pump of the hemofiltration circuit. To assess possible spontaneous degradation of the drug in the solution there was an additional reservoir prepared for each antibiotic, containing blood with the drug, which was not connected to the circuit. In the case of vancomycin, ciprofloxacine and tigecycline, a statistically significant decrease in the drug concentration in the hemofiltration circuit in comparison to initial value as well as to the concentrations in the control blood was observed, both for polyacrylonitrile and plolysulfone membrane. In the case of gentamicin, significant adsorption was noted only on polyacrylonitrile membrane. Our studies demonstrated that in full blood adsorption of antibiotics may be big enough to be of clinical significance. In particular in the case of polyacrylonitrile membrane.

Comparison of adsorption of selected antibiotics on the filters in continuous renal replacement therapy circuits: in vitro studies

The aim of this study was to assess the adsorption of selected antibiotics: vancomycin, gentamicin, ciprofloxacine and tigecycline in an experimental continuous veno-venous hemofiltration circuit with the use of both polyethyleneimine-treated polyacrylonitrile (PAN) and the polysulfone (PS) filter membranes. The crystalloid fluid dosed with one of antibiotic was pumped from a reservoir through a hemofiltration circuit (with PAN or PS membrane) and back to reservoir. All ultrafiltrate was also returned to the reservoir. During the procedures samples were collected from the post-hemofilter port at 5, 15, 30, 45, 60, 90, and 120 min. To determine spontaneous degradation of the antimicrobials, an additional bag with each study drug was prepared, which was not attached to the hemofiltration circuit. The samples from these bags were used as controls. In the case of vancomycin, gentamycin and tigecycline there was a statistically significant decrease in the drug concentration in the hemofiltration circuit in comparison to the control for PAN membrane (P < 0.05, P < 0.001, P < 0.001, respectively). In the case of ciprofloxacine adsorption was reversible and the drug concentrations increase to achieve the initial level for both membranes. Our studies indicated that a large portion of the administered dose of antibiotics may be adsorbed on a PAN membrane. In the case of gentamicin and tigecycline this amount is sufficiently big (over 90% of the administered dose) to be of clinical importance. In turn, adsorption on PS membranes is clearly lower (up to 10%) and may be clinically unimportant.

Treatment with echinocandins during continuous renal replacement therapy

Echinocandins are indicated as first-line treatment for invasive candidiasis in moderate to severe illness. As sepsis is the main cause of acute kidney injury, the combination of echinocandin treatment and continuous renal replacement therapy (CRRT) is common. Optimizing antibiotic dosage in critically ill patients receiving CRRT is challenging. The pharmacokinetics of echinocandins have been studied under various clinical conditions; however, data for CRRT patients are scarce. Classically, drugs like echinocandins with high protein binding and predominantly non-renal elimination are not removed by CRRT, indicating that no dosage adjustment is required. However, recent studies report different proportions of echinocandins lost by filter adsorption. Nevertheless, the clinical significance of these findings remains unclear.

Understanding renal replacement therapy and dosing of drugs in pediatric patients with kidney disease

Multifaceted factors need to be considered when prescribing renal replacement therapy (RRT) and dosing of drugs in pediatric patients with kidney disease. RRTs in pediatrics such as intermittent hemodialysis, continuous venovenous hemofiltration, continuous venovenous hemodialysis, and continuous venovenous hemodiafiltration affect solute and drug clearance. Drug properties such as molecular weight, molecular charge, volume of distribution, and protein binding affect drug clearance. RRT prescription parameters such as blood flow rate, ultrafiltration rate, membrane size, and pore size can also influence drug clearance. Furthermore, the pediatric patient presents additional concerns because of developmental factors in children that affect both pharmacokinetics of drugs.

Longitudinal hemodiafilter performance in modeled continuous renal replacement therapy

BACKGROUND/AIMS

With advanced anticoagulation, many institutions operate continuous renal replacement therapy (CRRT) circuits longer than manufacturers' recommendations. This extended use may change hemodiafilter performance and clearance properties. However, hemodiafilter performance over time has not been assessed. We investigated solute clearance over time in modeled CRRT.

METHODS

In vitro continuous hemofiltration (CH) and continuous hemodialysis (CD) were operated for 48 h using AN69 polyacrylonitrile, cellulose triacetate, F70 polysulfone, and Optiflux F160NR polysulfone hemodiafilters with citrated bovine blood. Urea, creatinine, gentamicin, vancomycin, and albumin clearances were assessed in CH (ultrafiltration rates = 1 and 3 l/h). Clearances of urea, creatinine, gentamicin, and albumin, were assessed in CD with dialysate flow rate of 2 l/h.

RESULTS

Solute CH clearances were significantly higher at 3 l/h. Only creatinine and gentamicin clearances were affected by time. Creatinine CD clearance significantly declined at 48 h for all hemodiafilters, especially polysulfone hemodiafilters.

CONCLUSIONS

CRRT duration affects solute transmembrane clearance. Clinicians should consider hemodiafilter age when assessing hemodialysis dose or drug clearance.

The use of SDS-PAGE scanning of spent dialysate to assess uraemic toxin removal by dialysis

Background. Uraemic toxins in the 8 to 60 kDa molecular weight range have been attracting increasing attention in dialysis therapy. However, there are no available standardized methods to evaluate their removal. Using new filtering membranes, we evaluated SDS–PAGE of spent dialysate to assess cut-off ranges and removal capacities into dialysate, while also measuring classical markers of dialyser function.

Methods. Eighteen dialysis patients were washed out for 2 weeks with FX 100 (Helixone^®), followed by randomization to Xevonta Hi 23 (Amembris^®) or FX dialysers for 2 weeks, then crossed over for an additional 2 weeks, and finally placed on Xenium 210 (Purema^®) for 2 weeks. SDS–PAGE scanning of the removed proteins contained in the spent dialysate was performed during all dialysis sessions. Total mass of urea, creatinine, total proteins, beta 2 microglobulin (β2m), retinol-binding protein (RBP) and albumin were measured. The reduction rates of serum urea, creatinine, β2m, leptin, RBP, alpha 1-antitrypsin, albumin and total proteins were also determined.

Results. SDS–PAGE scanning identified four major protein peaks (10–18, 20–22.5, 23–30 and 60–80 kDa molecular weight) and showed clear differences in the amounts of removed proteins between the dialysers, particularly in the 20–22.5, 23–30 and 60–80 kDa ranges. Total mass of removed β2m, RBP and albumin were in agreement with SDS–PAGE, while serum assays showed differing results.

Conclusions. SDS–PAGE scanning provided a good characterization of protein patterns in the spent dialysate; it extended and agreed with protein determinations and allowed a better assessment of dialyser performance in removing 10 to 80 kDa molecular weight substances. It also identified differences between the three mainly filtrating polysulfone dialysers that were not detected with blood measurements.