A fractional dialysate collection method to estimate solute removal in continuous venovenous hemodialysis

A new technique for low-volume continuous sampling of spent dialysate: a validation study

The measure of hemodialysis (HD) adequacy recommended nowadays by most guidelines, Kt/V-urea, presents significant drawbacks. Direct dialysis quantification (DDQ) through total dialysate collection (TDC), considered the gold standard measure of HD adequacy, is cumbersome, which precludes its widespread use in clinical practice. The present study aims to validate a low-volume continuous sampling of spent dialysate (CSSD). Cross-sectional study carried out at a university hospital. Throughout 4-h hemodialysis sessions, urea removal was measured by three DDQ methods: TDC, CSSD, and fractional sampling of dialysate (FSD). The primary outcome was the comparison between the total mass of urea removed measured by TDC and the dialysate sampling techniques. The comparison between urea distribution volume (UDV) estimated by anthropometric method and through DDQ was a secondary outcome. The analysis was done through linear regression and Bland-Altman concordance method. Twenty HD sessions were studied. The mean amount of urea collected in TDC and calculated from the 40-mL sample of CSSD were 33.70 ± 11.70 g and 33.90 ± 11.70 g, respectively [r 0.96, p < 0.0001; bias - 0.2 (95% CI - 1.8 to 1.4); limits of agreement - 6.8 to 6.4]. The anthropometric measure, when compared with DDQ method, underestimated UDV in patients with smaller body size. This new simple, inexpensive, and small volume CSSD technique can provide accurate information about the total amount of solutes removed by hemodialysis.

Fluids for Continuous Renal Replacement Therapy – an Evaluation of Microbial Integrity

Purpose

We have previously demonstrated widespread microbial contamination in the dialysis and replacement fluid circuits of bicarbonate-buffered, continuous renal replacement therapies (CRRTs). It is not known whether different CRRT fluids have an impact on bacterial activity.

Methods

In this study the in vitro growth and biofilm formation associated with seven strains of bacteria ( Burkholderia cepacia, Escherichia coli, Staphylococcus aureus, Stenotrophomonas maltophilia, Pseudomonas aeruginosa, Pseudomonas fluorescens, and Staphylococcus epidermidis) in five CRRT fluids (Prismocitrate, Monosol S, Accusol 35, tri-sodium citrate and Ci-Ca K2) were studied. The fluids were each inoculated with light and heavy concentrations of each of the bacterial strains and incubated at 22 or 37°C for up to 72 h with and without bacterial growth medium. Bacterial growth was assessed by spectrophotometry. Biofilm formation was assessed by a standard microtiter plate assay.

Results

Unsupplemented fluids did not support bacterial growth or biofilm formation after 72 h incubation. When supplemented with bacterial growth medium, some fluids, in particular Accusol 35, Ci-Ca K2, and tri-sodium citrate, had an inhibitory effect on bacterial growth, although none suppressed growths across the panel of tested organisms.

Conclusions

Different CRRT fluids have different impacts on bacterial growth and biofilm formation, but all remain susceptible to extrinsic contamination.

Removal of linezolid by conventional intermittent hemodialysis, sustained low-efficiency dialysis, or continuous venovenous hemofiltration in patients with acute renal failure

OBJECTIVE

To study the removal of linezolid, a new oxazolidinone antibiotic, by renal replacement therapy in patients with acute renal failure.

DESIGN

Prospective, single-dose pharmacokinetic study.

SETTING

Renal intensive care unit of a tertiary university hospital.

PATIENTS

Fifteen critically ill patients with oliguric acute renal failure on renal replacement therapy (seven males, mean age 72.3 yrs, range 60-94; Acute Physiology and Chronic Health Evaluation II score 24.9, range 18-36; mechanical ventilation ten of 15).

INTERVENTIONS

All patients received 600 mg of intravenous linezolid before starting renal replacement therapy, which consisted of intermittent hemodialysis lasting 3-4 hrs in eight patients, sustained low-efficiency dialysis lasting 8 hrs in five patients, and continuous venovenous hemofiltration lasting 10.5-12 hrs in two patients.

MEASUREMENTS AND MAIN RESULTS

Linezolid concentrations were measured by liquid chromatography/mass spectrometry methods on serum and dialysate/ultrafiltrate samples. At the start of renal replacement therapy, serum levels averaged 11.91 mg/L (range 5.49-21.52) and dropped at the end to levels <4 mg/dL (90% minimum inhibitory concentration values for Staphylococcus aureus) in three of eight patients on hemodialysis, three of five patients on sustained low-efficiency dialysis, and two of two patients on continuous venovenous hemofiltration. Mean removal of the drug was 193.7 mg with hemodialysis (32.3% of the dose administered), 205 mg with sustained low-efficiency dialysis (33.9%), and 74.8 mg (12.4%) and 105 (17.5%) mg following a continuous venovenous hemofiltration session lasting 10.5 and 12 hrs, respectively.

CONCLUSIONS

In patients with acute renal failure, serum levels of linezolid can be reduced to the subtherapeutic range following renal replacement therapy.

Dialysis in acute renal failure: is more better?

An increasing body of evidence indicates therapy dose and intensity influence the outcome of dialyzed ARF patients. However, a number of unanswered questions remain on this issue. These questions need to be addressed in future prospective, controlled trials that assess the effect of dose and intensity on outcome both within and between the various ARF renal replacement therapies, with appropriate and clinically relevant control arms. Such investigations should provide guidelines ultimately for the dialytic management of critically ill patients with ARF.