Epidural Filters Research Articles

The efficacy and safety of epidural filter catheters when used for post-operative intra-articular anaesthesia

There are concerns about the risk of iatrogenic infection when employing local anaesthetic techniques with post-operative intra-articular infusions in total knee arthroplasty. This study aimed to determine the efficacy of intact epidural filters in preventing transit of bacteria and to develop a technique of administration which would prevent membrane rupture.Filter efficacy was assessed using a standardised test suspension of Pseudomonas aeruginosa. Twenty millilitres of suspension was injected through isolated epidural filters (n=10) or filters with 40cm of catheter tubing attached (n=30). For each filter, injections were carried out at 0, 8 and 24h. Filtrates were collected, incubated, sub-cultured onto Columbia horse blood agar and examined for bacterial growth.Three delivery techniques were tested: manually controlled syringe with 5ml of water at 20ml/min, forced administration syringe with 5ml of water at >240ml/min and an automated syringe driver delivering 40ml of water at 6.7ml/min. For the two techniques using syringes, three syringe sizes, 5ml, 10ml and 20ml, were tested. Each test condition was carried out on 10 filters (total n=70). Filters were examined for rupture.Intact epidural filters prevented bacterial transit in all cases. Manual controlled and automated syringe driver administration generated no filter ruptures. Manual forced administration generated 93% filter rupture. Ruptures occurred at peak pressures of approximately 620kPa.Epidural filters can be used to prevent bacterial transit. These results suggest automated devices remove the risk of filter rupture. This study is relevant to all specialties that utilise these filters during infiltration such as epidurals or other regional anaesthetic techniques. Clinical relevanceThis study identified that filters are prone to rupture with high infusion rates and that manual techniques are particularly vulnerable. From these results, it is recommended that pumps are used to minimise risk of filter rupture.

Aspiration testing and epidural filters

Aspiration testing and epidural filters

An investigation into the antibacterial efficacy of three makes of epidural filters

Objective This study investigated and compared the efficacy of three locally available epidural filters as bacterial barriers over a three-day period of simulated use and tested whether aspiration through the filters could damage them.

Adsorption of sufentanil to epidural filters and catheters.

Stable drug concentrations must be administered to provide adequate patient-controlled epidural analgesia. This study investigated the stability of sufentanil after the epidural delivery system had been flushed with solutions containing the drug. Sufentanil citrate, 5 microg mL(-1) was injected through an epidural catheter system into a glass container. The concentrations of the drug leaving the system, in 1 mL aliquots (1-5 mL) were measured using high-performance liquid chromatography. In the same manner, sufentanil samples were analysed after flushing the filter, as well as after priming the filter and catheter. ANOVA for repeated measurements demonstrated that sufentanil concentrations remained constant as long as the catheter had been adequately flushed. However, the concentration of sufentanil in the solution exiting the filter was reduced significantly. Hardly any sufentanil could be detected (0.09 +/- 0.01 microg mL(-1), P < 0.001) in the first 1 mL aliquot (probe) leaving the filter. Altogether, 3 mL sufentanil solution was needed to pass through the filter before the baseline values were restored (P > 0.05). The greatest decrease occurred when the whole epidural delivery apparatus (catheter and filter) was primed; to regain baseline values, as much as 4 mL solution was needed to flush the system. Sufentanil citrate is adsorbed by the materials used to manufacture systems (catheters, filters) used in epidural anaesthesia. Hence, the epidural catheter system should be primed with sufentanil before connecting it to the patient so as to deliver reliable concentrations.

Adsorption of sufentanil to epidural filters and catheters

Background and objective: Stable drug concentrations must be administered to provide adequate patient-controlled epidural analgesia. This study investigated the stability of sufentanil after the epidural delivery system had been flushed with solutions containing the drug. Methods: Sufentanil citrate, 5 μg mL−1 was injected through an epidural catheter system into a glass container. The concentrations of the drug leaving the system, in 1 mL aliquots (1-5 mL) were measured using high-performance liquid chromatography. In the same manner, sufentanil samples were analysed after flushing the filter, as well as after priming the filter and catheter. Results: ANOVA for repeated measurements demonstrated that sufentanil concentrations remained constant as long as the catheter had been adequately flushed. However, the concentration of sufentanil in the solution exiting the filter was reduced significantly. Hardly any sufentanil could be detected (0.09 ± 0.01 μg mL−1, P < 0.001) in the first 1 mL aliquot (probe) leaving the filter. Altogether, 3 mL sufentanil solution was needed to pass through the filter before the baseline values were restored (P > 0.05). The greatest decrease occurred when the whole epidural delivery apparatus (catheter and filter) was primed; to regain baseline values, as much as 4 mL solution was needed to flush the system. Conclusions: Sufentanil citrate is adsorbed by the materials used to manufacture systems (catheters, filters) used in epidural anaesthesia. Hence, the epidural catheter system should be primed with sufentanil before connecting it to the patient so as to deliver reliable concentrations.

Electron microscopy in quality control of equipment used in regional anesthesia

We evaluate the use of the scanning electron microscopy to study different materials used in regional anesthesia with the aim of finding an alternative method for quality analysis of such items. We study spinal needles, epidural catheters, and epidural filters of different manufacturers and we verify differences between products labeled with the same denomination. We find fissures, broken tips, and faults in unused spinal needles. The characteristics of the catheters and microcatheters were observed. We observed structural details from pores in epidural filters and the mechanisms involved in the trapping of particles facilitated by the presence of several numbers of pores randomly distributed in layers within the filtering lamina. Copyright 2002, Elsevier Science (USA). All rights reserved.

Cancer pain relief by continuous administration of epidural morphine in a hospital setting and at home

Fifteen patients with severe pain due to malignancy were treated by continuous epidural morphine infusions. A disposable external pump was used. Patients were treated in a hospital setting or at home for a total of 906 days. Pain intensity was estimated by VAS. The pumps functioned well. Bacterial growth was found in 0.6% of the balloon reservoirs used, while the epidural filters were free from growth. There were no clinical infections. It appears that this delivery system is safe, practical and suitable for use in the home environment.