Do plastc cannulae have beter outcomes than metal needles in haemodialysis? A retrospectve review.
Haemodialysis patients are becoming frailer, starting haemodialysis at an older age and with more co-morbidities than ever before. The increase in patients with diabetes and peripheral vascular disease has meant that there is an increase in the amount of underdeveloped arteriovenous fistulae (AVF) due to arterial calcification, poorer cardiac output, smaller vessel size and poorer healing properties. These events can have a significant effect on the ability of the nurse to cannulate the AVF, particularly when patients are new to haemodialysis. One relatively new initiative, which has the potential to decrease some of the issues with cannulation in these frailer vessels, is the introduction of plastic cannulae for AVF cannulation.
Plastic cannulae for haemodialysis vascular access cannulation have been used in Japan for over 25 years and have now been available to Australian renal units for over five years (Du Toit, 2013). The uptake of the plastic cannula has been ad hoc throughout the nation due to the cost of cannulae in comparison to metal needle ($3.90 per cannula compared to $1 per metal needle), and the learning curve required for renal nurses to learn this new skill. An extensive comparison of the available types, dimension and pros and cons of the plastic cannulae, along with specific indications for their use in particular patients, have been detailed in a recent editorial paper (Parisotto et al., 2016).
The vascular health nurse at Barwon Health introduced plastic cannulae into the renal unit in 2013 as a quality improvement initiative. History has shown that the use of metal needles for cannulation has contributed to extravasation of the vessel, thrombus, aneurysm, pseudoaneurysm and stenosis formation and also patient anxiety when starting haemodialysis, particularly related to the pain of needle insertion (Lee Barker & Allon, 2006; Marticorena & Donnelly, 2016; van Loon et al., 2009). The vascular health nurse had noted that, although there was scant information available about plastic cannulae, the information was positive in relation to a decrease in cannulation issues such as extravasation and the ability to cannulate a greater length of vessel into the antecubital fossa. The initial clinical reports also noted that patients were able to move their arm around more during the haemodialysis session, thus decreasing intra-dialysis extravasation of the vessel (Donnelly & Marticorena, 2012; Du Toit, 2013; Grainer, 2014).
Barwon Health renal services introduced an initial training program, which took a period of 16 months for all staff to reach a level of competence. Smith and Schoch (2016) detailed that their training program took longer than anticipated, some staff were averse to change and outcomes for the use of plastic cannulae, in this early stage, were positive. At the end of the training period a protocol was introduced for staff to use the plastic cannulae on all patients starting haemodialysis with an AVF in the first six treatments (2 weeks). This is the time when most extravasations and adverse events occur (Letachowicz, et al., 2015; van Loon et al., 2009) and the most affordable option due to the higher cost of the plastic cannulae.
Once the training program was completed, and considering that published data up to this point were only related to initial introduction of plastic cannula into renal units (Letachowicz et al., 2015; Smith & Schoch, 2016), it was of interest to investigate the hypothesis of whether there was an improvement in the number of miscannulations, aborted dialysis sessions and adverse events, between the 16-month time period following the completion of staff training and the 16-month time period prior to the introduction of plastic cannulae (Figure 1). Essentially, this compared the outcomes between plastic cannula and metal needle cannulations.
Figure 1 Period 1 Prior to the introduction of plastic November 2012-February 2014 cannulas at Barwon Health Training period Introduction of plastic cannulas at March 2014-June 2015 Barwon Health Period 2 Post introduction of plastic July 2015-September 2016 cannulas at Barwon Health
The study design was a retrospective observational study and ethics approval was granted by the research, ethics, governance and integrity unit (REGI) at Barwon Health. Data were collected from the digital medical record (RenalNET) from the end of the staff plastic cannula-training period to the current date (16 months). Data collected were: number of miscannulations, number of mid-dialysis extravasations and number of aborted dialysis sessions. These data were then compared with the 16-month period prior to the introduction of plastic cannulae when only metal needles were available to use on new AVFs.
Patients were included in the study if they were over 18 years of age and had begun haemodialysis with an AVF during the 16-month time periods (Period 1: November 2012 -- February 2014 and Period 2: June 2015 -- September 2016).
Patients under the age of 18 years and those with CVC or AVG in situ at the beginning of haemodialysis were excluded.
Cannulation success rate was defined as the insertion of two needles or cannulae only and the successful completion of the haemodialysis session without requiring re-cannulation. Miscannulation was defined as the needle or cannula requiring removal and replacement. An aborted dialysis session was defined as the inability of two final needles or cannulae to be successfully inserted, resulting in the patient being sent home to return at a later date. These were measured in two different groups as either an aborted session before dialysis started or an aborted session once dialysis had begun. Whilst ultrasound machines were present in the unit, there was no documented evidence of ultrasound being used for either the metal or plastic cannulations.
During the time periods selected, a total of 28 patients started haemodialysis and were eligible to be included in the study, 16 in the metal needle group (prior to the plastic cannula training period) and 12 in the plastic cannulae group (post the end of the 16-month staff training period). The mean age of the patients in the plastic cannulae group was 75.3 years and the metal group was 62 years. Over half the patients (58%) in the plastic cannula group had diabetes as a co-morbidity as opposed to just over a third (37.5%) of the patients in the metal group; however, the rates of peripheral vascular disease (PVD) were marginally higher in the metal group (18%), compared to the plastic cannulae group (8%) (Table 1). Two-thirds of the patients in the plastic cannulae group had a radiocephalic AVF (66%) with the remainder of that cohort having brachiocephalic AVF (34%). The metal group had a bigger range of types of AVF with only 44% radiocephalic, 37.5% brachiocephalic, 12.5% brachiobasilic and 6% classed as "other". There were also differences between the cohorts in relation to the age of the AVF with over half (56%) of the metal group being less than 6 months old (since surgical creation) compared to only a third (33%) of the plastic cannulae group (Table 1).
Over the two 16-month periods measured, there were 96 dialysis sessions where metal needles were used for cannulation in the first two-week period of beginning haemodialysis and 72 dialysis sessions where the plastic cannula was used in this initial two-week period. The overall cannulation success rate (with two cannulations only) was higher in the metal needle cohort (62.5%) compared to the plastic cannulae cohort (50%); however, in the plastic cannulae cohort there were no aborted dialysis sessions either at the beginning of dialysis or during dialysis and no patient required re-cannulation during a dialysis session. The metal needle group had 8 (8.3%) sessions where the patient had to be sent home to rest the AVF and return to dialyse on another day, two sessions (2.1%) where dialysis had to be aborted as the AVF could not be re-cannulated and two patients (2.1%) who required re-cannulation during the dialysis session (Table 2). There was also one patient in the metal needle cohort who was counted in the successful group who had a significant bleed into the tissues post metal needle removal, which resulted in the patient being unable to dialyse for a week. One patient in the metal needle cohort required CVC insertion related to the inability to successfully cannulate the AVF and one in the plastic cannula cohort also had a CVC inserted due to cannulation issues. There was one patient in the metal needle cohort who underwent cardiac surgery and had a CVC inserted where the staff chose to use the CVC until the patient recovered from the surgery. In addition, there were no recorded data related to bleeding into the tissues following the removal of the plastic cannulae at the end of the haemodialysis sessions.
The initial hypothesis for this study was that there would be fewer miscannulations and more overall cannulation success with the plastic cannulae, particularly as all staff had finished the training period and had reached a level of competence. The overall results showed that the use of plastic cannulae for arteriovenous cannulation was less successful than the use of metal needles (50% versus 62.5%). However, positive outcomes identified were: miscannulations are much less catastrophic, no patients had aborted dialysis sessions at the beginning, or mid dialysis, nor were any patients sent home to "rest" the AVF to try again at a later date. This is a vast improvement on the 12.5% of patients who were sent home for various cannulation issues with metal needles, prior to the introduction of the plastic cannulae into the unit. Aborted dialysis sessions are significant adverse events as they can lead to increased fluid and electrolytes, which, in turn, increases the risk of fluid overload, cardiac arrhythmias and neurological side effects (Bennett et al., 2017). An aborted dialysis session could also have an impact on the renal unit, with increased use of consumables and the inconvenience to the patient and staff when reallocated to their non-scheduled day.
We looked into the differences in the cohorts to try to ascertain whether there were other factors that may have influenced success or miscannulations, such as the prevalence of co-morbidities that may affect the quality of the vessels, for example, diabetes and/or PVD. The plastic cannulae group did have a higher percentage of patients with diabetes and PVD (66%), compared with the metal group (55.5%) and a larger percentage of the metal group's AVF were less than six months old (56% versus 33%), which may have had an effect on the quality of the vessels to cannulate. Another factor which could have had an effect is the age of the vessels, as the plastic cannula group's mean age was 13.5 years older than the metal needle group. Previous studies have noted that an increased age correlates with more miscannulations (Lee et al., 2006); therefore, the fact that the plastic cannulae group had older patients with more co-morbidities and more radiocephalic AVFs (smaller vessels) may have contributed to the poorer overall cannulation success rate.
Another factor that may have contributed to the difference in the overall cannulation success is the experience of the staff in use of plastic cannulae. Whilst the training period was complete and all staff were signed off as competent, the fact that plastic cannulae are only used on new patients in the first two weeks of starting dialysis means that there are very few opportunities for staff to become "expert". Those who are more adept at using the plastic cannulae are the ones who are usually assigned to do the cannulating, which leads to de-skilling of other staff within in the unit. Wilson, Harwood, Oudshoorn and Thompson (2010) referred to this phenomenon as the "perpetual novice" where personal, environmental or contextual factors affected the experience of the nurse and therefore their confidence in cannulation. The part-time nature of the workforce would also decrease the opportunities for staff to increase their skill level in relation to plastic cannulation. We also noted that when some staff had difficulty with cannulation with the plastic cannulae they reverted back to metal needles (even though this is not unit protocol), rather than persevering with the plastic option. This was similar in the training phase where we found that staff would revert back to use of the CVC if one was in situ rather than have another attempt with the plastic cannulae (Smith & Schoch, 2016). Wilson, Harwood and Oudshoorn (2012) also studied a similar issue, referred to as "cannulation avoidance", where their staff avoided cannulation of AVF in their unit. Wilson et al. (2012) explored the reasons behind this behaviour and their qualitative results indicated that the staff were influenced by: their own confidence in their skills; the time pressures of the production line atmosphere; and the limited learning opportunities due to low numbers of AVF. These results may well be the reasons that our staff reverted to CVC in the training period and metal needles post-training, but without the qualitative data to compare, it is difficult to know exactly why the reversions took place.
Another possible reason for the lower rate of cannulation success with the plastic cannula is that once the plastic cannula is inserted and the introducer is pulled back there is limited ability to manipulate the plastic into a different position. This requires removal of the cannula and another cannula inserted. Whilst two successful metal needles can be counted in a session, there is no indication in the database notes whether either of those needles required manipulation to get them into place. All we know is that they did not require removing and re-siting.
Limitatons to this study
The study only included a small sample population at a single site and as an observational study variables and confounders have not been controlled for. Retrospective data collection relied on the accuracy of the data input into the digital medical record. Only descriptive statistics have been used to analyse the data. The study only counted quantitative data and did not compare the qualitative experiences of the patients and nurses.
The results of this study are favourable towards the use of plastic cannulae in haemodialysis in relation to: fewer catastrophic extravasations and fewer aborted haemodialysis sessions. There were differences in the age of the participants and the age of the AVFs (older in the plastic cannulae cohort) and the co-morbidities of the patients (more in the plastic cannulae cohort), which could have affected the cannulation success rates of in the plastic cannulae cohort. Future studies, including randomised controlled trials with larger, multi-site arms need to be undertaken to provide more detailed data collection and analysis. Qualitative studies also need to be undertaken to measure the end-user data related to patient pain perception and nurse perception related to the use of plastic cannulae. Plastic cannulae are more commonly used in haemodialysis units around Australia in the initial two-week period only, due to the cost of the cannulae in comparison to the cheaper metal needle. It is hoped that the higher the unit uptake of the plastic cannulae around the world, the more affordable it will become, leading to more experienced staff in the technique, and better patient outcomes.
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Vicki Smith RN, MNurs, BN
Barwon Health Renal Department, Geelong, VIC, Australia
Monica Schoch RN, PhD (c), MNurs, BN(Hons)
Deakin University, Waterfront Campus, Geelong, VIC, Australia
Correspondence to: Vicki Smith, Vascular Health Nurse, Renal Department, Barwon Health, VIC, Australia
Submitted: 31 May 2017, Accepted: 4 July 2017
Table 1: Demographics Plastic (n=12) Metal (n=16) Male 7 58% 9 56% Female 5 42% 7 44% Mean age 75.3 62 Co-morbidities Diabetes 7 58% 6 37.5% PVD 1 8% 3 18% Type of AVF Radiocephalic AVF 8 66% 7 44% Brachiocephalic AVF 4 34% 6 37.5% Brachiobasilic AVF 0 0 2 12.5% Other AVF 0 0 1 6% Age of AVF 6 weeks-3 months 1 8% 3 18% 3-6 months 3 25% 6 38% 6-9 months 1 8% 0 0 9-12 months 3 25% 0 0 > 12 months 4 34% 7 44% Table 2: Results Plastic cannula Haemodialysis sessions 72 Aborted dialysis sessions (not started) 0 0% Aborted dialysis session (mid-dialysis extravasation) 0 0% Re-cannulation during dialysis session 0 0% CVC insertion required due to cannulation issues 1 1.5% Successful dialysis sessions requiring more than 2 31 43% cannulations at beginning Plastic cannula cohort cannulated with metal when 4 5.5% plastic fail Cannulation success rate (2 needles/cannula ONLY and 36 50% dialysis able to be completed) Metal needle Haemodialysis sessions 96 Aborted dialysis sessions (not started) 8 8.3% Aborted dialysis session (mid-dialysis extravasation) 2 2.1% Re-cannulation during dialysis session 2 2.1% CVC insertion required due to cannulation issues 2 4.2% Successful dialysis sessions requiring more than 2 20 20.8% cannulations at beginning Plastic cannula cohort cannulated with metal when N/A N/A plastic fail Cannulation success rate (2 needles/cannula ONLY and 60 62.5% dialysis able to be completed)
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|Author:||Smith, Vicki; Schoch, Monica|
|Publication:||Renal Society of Australasia Journal|
|Date:||Nov 1, 2017|
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