An easy disinfection strategy for pipes connecting hemodialysis equipment

INTRODUCTION

A hemodialysis room has pipes connecting the console and central fluid equipment. While these pipes require disinfection, reports detailing disinfection strategies are unavailable. Therefore, we aimed to compare two easy disinfection strategies differing in sanitization frequency and sanitizer concentration.

METHODS

Reverse osmosis water (ROW) purifying equipment and six dialysis consoles were connected by 20 m of pipes. Only ROW flowed through these pipes, because the dialysate solution was constituted at each console. The pipes were sanitized by two strategies: (1) strong and monthly (hypochlorite concentration: 100 ppm) or (2) weak and weekly (5 ppm). Both strategies were easy because the sodium hypochlorite was simply added to the ROW tank. To estimate sanitization efficacy, endotoxin counts at the ROW tank outlet, the end of the pipe, and the pipe after the endotoxin-cutting filter in each console were measured monthly for six continuous months. These counts were compared between the two sanitization strategies.

RESULTS

The endotoxin counts at the ROW tank outlet and the end of the pipe were 0.004-0.017 and 0.012-0.081 EU/mL, respectively, in the strong and monthly strategy, and 0.001-0.003 and 0.001-0.005 EU/mL, respectively, in the weak and weekly strategy. The endotoxin counts at the pipe after the endotoxin-cutting filter were less than 0.001 EU/mL during the study period in both strategies.

CONCLUSION

A weekly disinfection strategy was more effective than a monthly one, despite the lower hypochlorite concentration. The present study suggests that frequency is the most important factor in the disinfection of pipes in a dialysis room.

Antithrombotic properties of hemofilter coated with polymer having a hydrophilic blood-contacting layer

OBJECTIVE:

Extracorporeal circulation devices are coated with a biocompatible polymer coating agent (BPCA) that has a hydrophilic blood-contacting layer, but hemofilters are not. We aimed to investigate the antithrombotic properties of a BPCA-coated hemofilter.

METHODS:

Four experiments using BPCA-coated circuits and non-coated hemofilters and four experiments using BPCA-coated circuits and BPCA-coated hemofilters were performed with whole human blood and compared by measuring the circuit pressure every 5 min, antithrombin activity every 40 min, and thrombin-antithrombin complex every 40 min, for a total of 240 min of recirculation.

RESULTS:

The mean time required for the pressure at the inlet of the hemofilter to increase sharply was longer in BPCA-coated than in non-coated hemofilters (66 ± 11 min vs 25 ± 9 min, p < 0.01). The mean antithrombin activity value at 200 and 240 min of recirculation was significantly higher in the experiments with BPCA-coated versus non-coated hemofilters (43.3 ± 2.87 vs 33.3 ± 5.74, p = 0.04; 42.8 ± 3.59 vs 31.0 ± 5.35, p = 0.01, respectively); the antithrombin activity values at the other time points were not significantly different. Furthermore, all thrombin-antithrombin complex values in experiments with the BPCA-coated hemofilters achieved overrange at 80 min of recirculation, whereas those with the non-coated hemofilter achieved overrange at 40 min.

CONCLUSION:

This study suggests that BPCA-coated hemofilters can inhibit antithrombin consumption, contributing to antithrombotic effects in extracorporeal circulation circuits.

Hemodialysis membrane coated with a polymer having a hydrophilic blood-contacting layer can enhance diffusional performance

Purpose

Currently, the foreign surfaces of various extracorporeal circulation devices are coated with a biocompatible polymer coating agent (BPA), which creates a hydrophilic blood-contacting layer to reduce thrombogenicity, while the membranes in hemodialyzers are not. We aimed to clarify other side effects of BPA-coated membranes by examining the diffusion performance in in vitro experiments.

Methods

We used a polyethersulfone membrane (sieving coefficient of albumin is ≤0.01) coated with BPA product, SEC-1™ (Toyobo), in a hemodialyzer. To estimate the diffusion rates of a wide range of molecules, 2 L of saline containing vancomycin, lysozyme, and albumin were recirculated in the circuit configured with a hemodialyzer, and dialyzed continuously using water. The concentrations of sodium, vancomycin, lysozyme, and albumin were measured every 5 minutes for 30 minutes and compared in experiments with BPA-coated (n = 4) and BPA-noncoated (n = 4) membranes.

Results

The removal rates of sodium and vancomycin after 5 minutes of dialysis (n = 24) were significantly higher in BPA-coated than noncoated membranes, while those of lysozyme and albumin were not significantly different. The removal rates of sodium and vancomycin after 30 minutes of dialysis (n = 4) were significantly higher, and those of lysozyme were significantly lower in BPA-coated than noncoated membranes, while those of albumin were not significantly different.

Conclusions

The preliminary study suggests that BPA-coated membranes enhanced the diffusion rate of molecules with low and middle molecular weight without affecting the sieving coefficient of albumin. Thus, BPA coating can enhance the dialysis performance of membranes.

Prospects for Clinical Applications of Polymer-Coated Haemoconcentrator on Extracorporeal Circuit in Cardiopulmonary Bypass Surgeries

Purpose

Extracorporeal circulation circuits used in cardiopulmonary bypass surgeries are increasingly being coated with polymer materials to reduce the thrombogenicity of extracorporeal devices. However, a haemoconcentrator, which corrects haematocrit and electrolyte imbalances, is not coated with polymers. In this study, we sought to assess the filtration performance of polymer-coated haemoconcentrators in order to obtain insight into their prospects for use in clinical applications.

Methods

In vitro experiments were performed to evaluate the water pressure and flow properties of polymer-coated haemoconcentrators by comparing 3 polymer-coated haemoconcentrators with 3 non-coated haemoconcentrators. The cross-sectional surfaces of both types of haemoconcentrators were observed using a scanning electron microscope (SEM).

Results

The slopes of the regression lines for estimating the filtrated fluid flow as a function of the transmembrane pressure were 6.286 ± 0.320 for polymer-coated haemoconcentrators and 3.712 ± 0.170 for non-coated haemoconcentrators. These slopes were found to be significantly different and indicate that the filtration velocity is enhanced in polymer-coated haemoconcentrators over that in non-coated haemoconcentrators. However, the hollow fibre damage observed by SEM was not shown to contribute to higher filtration flow in the polymer-coated haemoconcentrator. Taking these results into consideration, we hypothesise that a polymer coating makes a foreign surface on a hollow fibre slippery, owing to the hydrophobicity of the polymer, thereby enhancing the velocity of the filtration.

Conclusions

The results of this preliminary investigation suggest that a polymer coating can enhance the filtration performance of a haemoconcentrator and that polymer-coated haemoconcentrators might be useful in clinical applications.

Is using an open-reservoir cardiopulmonary bypass circuit after 6 days on standby safe?

OBJECTIVES

To investigate the sterility and biocompatibility of a stored open-reservoir cardiopulmonary bypass circuit maintained on standby.

METHODS

A total of four cardiopulmonary bypass circuits were assembled, primed and left to recirculate. One unit was placed in a positive-pressure operating room and the other three were placed in the intensive care unit. The primed solutions, which employed Ringer's acetate, hydroxyethylated starch and hydrate steroid, were sampled after 0, 24, 48, 72, 96, 120 and 144 h in all cardiopulmonary bypass circuits to measure the bacteria count, endotoxin count and chemical substances within the primed solution. Chemical substances were detected by assessing the following: the total organic carbon by the combustion oxidation infrared spectrometry, and molecular weight spread by gel permeation chromatography. The environments were left unattended and were uncovered during the storage period to mimic the clinical scenario.

RESULTS

There were no bacteria in any of the primed solutions, and only very minute concentrations of endotoxins were detected, both in the operating room and in the intensive care unit. The total organic carbon concentration was slightly more concentrated in the 144-h samples when compared with that in the 0-h samples. However, the molecular weight spread of the 0-h sample was identical to that in the 144-h sample.

DISCUSSION

With regard to the presence of bacteria and endotoxins, we noted that the hardshell reservoirs in the cardiopulmonary bypass circuit were effectively sealed and not invaded by bacteria. With regard to the presence of chemical substances, we noted that an increase in total organic carbon concentration was caused by bedewing, and that there was no release of chemical substances such as a polymer-coating agent, or other molecular materials in the primed solution.

CONCLUSIONS

There was no contamination or release of chemical substances in 6-day old cardiopulmonary bypass circuits maintained on standby, confirming that they are safe to use in terms of sterility and biocompatibility.

Features of an alternative hemodialysis method using a hemoconcentrator during cardiopulmonary bypass surgeries

Purpose:

This study clarified the features of a hemoconcentrator-based, alternative hemodialysis (ALTHD) method that improves the speed of serum potassium (K+) concentration adjustments, compared with dilutional ultrafiltration (DUF), during cardiopulmonary bypasses.

Methods:

Standardized bovine blood was recirculated (300 ml/min) through an in vitro hemoconcentrator circuit; hematocrit, K+ and glucose levels were measured at 5–20 min after DUF or ALTHD. We evaluated DUF at dialysis speeds of 50–250 ml/min and ALTHD at speeds of 50–1000 ml/min.

Results:

ALTHD rapidly corrected K+ and glucose concentrations at speeds up to 800 ml/min. ALTHD took 8.9 min to reach a K+ level of 4.5 mmol/L, faster than DUF (12.8 min). The ALTHD efficiency curves plateaued at 600 ml/min.

Conclusion:

ALTHD allowed faster adjustment of electrolyte levels, with peak efficiency at 600 ml/min. ALTHD has possible clinical application if available for potential use during all cardiopulmonary bypass surgeries involving extracorporeal circulation.