I originally learned to use ultrasound for vascular mapping and arteriovenous (AV) fistula assessment during a fellowship in Vancouver, before taking up a position as a consultant in the regional nephrology unit at Belfast City Hospital – which helps to manage vascular access for 700 haemodialysis patients across Northern Ireland – in 2011. Since then, I have developed a special interest in vascular access for dialysis and home haemodialysis, honing the scanning and interpreting skills I had learnt in Canada.
Arteriovenous fistulas are created surgically by connecting an artery with a vein, usually in the arm. This makes the vessel larger, stronger and more robust for transferring the blood into the dialysis machine and back into the patient. Fully functioning fistulas are essential for effective dialysis. Prior to the use of ultrasound blood vessel assessment, patients often had attempted AV fistula creations that subsequently failed to work well enough for dialysis treatment. Failed AV creation procedures potentially cause distress to the patient and also impact on the efficient management of surgical lists. For many individuals, it is difficult to assess their veins by clinical observation and touch alone; some sit deep within the tissue, others can be tortuous or anatomically deviated from a typical position. Using POCUS has transformed the process for these ‘trickier’ cases.
For many individuals, it is difficult to assess their veins by clinical observation and touch alone; using POCUS has transformed the process for these cases
In the first instance, we use ultrasound to accurately map the patient’s veins and arteries, identify the best location for the fistula, and then monitor its maturation after creation. It also allows us to puncture a fistula with pinpoint accuracy, particularly when the patient first starts on dialysis treatment, and to assess the appearance and performance of vessels over time to judge whether it is still viable, looking out for problem areas that will need ultrasound guidance in subsequent sessions, as well as such things as stenoses that require intervention to improve the fistula function. In my experience, we can now use and maintain the viability of AV fistulas that would simply not be possible to access without POCUS. If we do need to refer on for surgical or radiological intervention – to create a new fistula, to use an AV graft if the veins are not suitable for a fistula, or to angioplasty a stenosis – we are now able to provide accurate and detailed descriptions in the referral because of the knowledge gleaned from the ultrasound.
We have several systems from FUJIFILM SonoSite in the nephrology department in Belfast, including a SonoSite M-Turbo – carried around in its bag to different wards and outpatient clinics, as well as outside the hospital – and a SonoSite X-Porte system that is used in the procedure room for dialysis line insertions and kidney biopsies, and in the operating theatre to assess kidney transplants. Technology has developed so much over the years, with today’s handheld machines being small, lightweight, easy to pick up and, like the larger X-Porte, move quickly between patients or locations. The systems are also robust enough to withstand the everyday bumps that inevitably happen when they are accidentally dropped or knocked around the bedside area.
It has become clear in most dialysis units that nurses should be trained to use POCUS, as they are the ones who carry out most of the needle insertions. Local radiologists or nephrologists should always be available as expert back-up but, to really reap the rewards of POCUS, I believe that nurses should use it widely too. I regularly provide on-the-job training for nurses in our unit, as well as running workshops as part of the VASBI (Vascular Access Society of Britain and Ireland) conference, which prove very popular each year. In small groups of mostly nurses, we cover the basics of scanning on real patients and encourage staff to seek further training and hands-on experience in their own work setting.
Using POCUS afterwards can show why it (cannulation) was difficult, so that the user can work out what was going wrong and seek an alternative method or technique
The interesting thing I have noticed from my experience in training people, particularly the nurses providing dialysis treatment, is not only the clinical benefits of POCUS – which are indisputable – but also the effect it has on the confidence and approach of the users. Anyone can feel really deflated after a failed attempt at cannulation, but using POCUS afterwards can show why it was difficult, so that the user can work out what was going wrong and seek an alternative method or technique. Knowing why it didn’t work the first time motivates you to try again, hopefully with better success.
I have frequently observed the benefits ultrasound offers to patients as well; it guides the angle and accuracy of a puncture, which undoubtedly reduces the number of attempts required to get a needle placed, making the whole experience less distressing and painful for the patient. I like to show them the images when I scan and explain why their veins are problematic, or why we need to try a different site. With knowledge of their own anatomy, they feel empowered to guide treatments in future sessions and become more involved in the decisions being made around them. Taking everything into consideration – the numerous clinical benefits, enhanced user confidence, and less pain and distress for the patient – it is not an overstatement to say that POCUS has revolutionised vascular access management for haemodialysis.