Preoperative point-of-care ultrasound and its impact on arteriovenous fistula maturation outcomes

Pre-operative ultrasound mapping before arteriovenous fistula formation: an updated systematic review and meta-analysis

BACKGROUND

Arteriovenous fistula represents the preferred vascular access for patients with kidney failure requiring hemodialysis. Surgeons have traditionally used physical examination to identify the most suitable vessels. This meta-analysis aims to evaluate whether ultrasound mapping should be routinely performed before arteriovenous fistula creation.

METHODS

Medline, Scopus, Web of Science and CENTRAL were systematically searched from inception to November 1, 2022. Randomized controlled trials and cohort studies comparing routine ultrasound mapping to physical examination in terms of arteriovenous fistula patency were included. Meta-analysis was performed by fitting random-effects models. The study protocol has been prospectively registered in PROSPERO (CRD42023402390).

RESULTS

Overall, 18 studies were included, comprising 3655 participants. Routine pre-operative ultrasound mapping was associated with significantly lower rates of primary arteriovenous fistula failure (Risk Ratio-RR: 0.56, 95% confidence intervals-CI: 0.37-0.84, low certainty). A significant outcome was observed by separately pooling randomized controlled trials (RR: 0.37, 95% CI: 0.25-0.54). Routine ultrasound mapping was also associated with significantly higher rates of 1-year primary arteriovenous fistula patency (RR: 1.33, 95% CI: 1.19-1.47, moderate certainty). This effect remained significant in the analysis of randomized controlled trials (RR: 1.26, 95% CI: 1.02-1.56).

CONCLUSIONS

Implementing routine pre-operative ultrasound mapping of vessels is associated with significantly better outcomes in terms of early arteriovenous fistula failure and primary patency rates at 12 months. Further research should confirm the long-term benefits of routine ultrasound examination and evaluate its cost-effectiveness in different populations.

Hemodialysis Access: US for Preprocedural Mapping and Evaluation of Maturity and Access Dysfunction

Patients with kidney failure require kidney replacement therapy. While renal transplantation remains the treatment of choice for kidney failure, renal replacement therapy with hemodialysis may be required owing to the limited availability and length of time patients may wait for allografts or for patients ineligible for transplant owing to advanced age or comorbidities. The ideal hemodialysis access should provide complication-free dialysis by creating a direct connection between an artery and vein with adequate blood flow that can be reliably and easily accessed percutaneously several times a week. Surgical arteriovenous fistulas and grafts are commonly created for hemodialysis access, with newer techniques that involve the use of minimally invasive endovascular approaches. The emphasis on proactive planning for the placement, protection, and preservation of the next vascular access before the current one fails has increased the use of US for preoperative mapping and monitoring of complications for potential interventions. Preoperative US of the extremity vasculature helps assess anatomic suitability before vascular access creation, increasing the rates of successful maturation. A US mapping protocol ensures reliable measurements and clear communication of anatomic variants that may alter surgical planning. Postoperative imaging helps assess fistula maturation before cannulation for dialysis and evaluates for early and late complications associated with arteriovenous access. Clinical and US findings can suggest developing stenosis that may progress to thrombosis and loss of access function, which can be treated with percutaneous vascular interventions to preserve access patency. Vascular access steal, aneurysms and pseudoaneurysms, and fluid collections are other complications amenable to US evaluation. ©RSNA, 2023 Supplemental material is available for this article. Test Your Knowledge questions for this article are available through the Online Learning Center.

Point-of-care ultrasound-guided cannulation versus standard cannulation in hemodialysis vascular access: A controlled random order crossover pilot feasibility study

BACKGROUND

Standard cannulation practice for hemodialysis consists of inserting needles "blindly" through skin into an arteriovenous fistula (AVF), which is more likely to cause damage. Point-of-care ultrasound (POCUS) guided cannulation has potential for less damage; however, efficacy of this technique has not been explored. Our purpose was to test the feasibility and effectiveness of POCUS guidance for cannulation of AVFs in hemodialysis patients.

METHODS

A random-order crossover research design was used; patients and nurses acted as their own control. Sample included 13 patients with functioning AVFs and 9 nurses, recruited from a single hemodialysis center. All nurses cannulated all patients using standard and POCUS-guided cannulation. Data were collected at each cannulation (time taken, nurse position, probe direction, pressures, patient satisfaction, pain scores). Ultrasound images of needle position were collected from which needle tip locations inside vessels were measured. Nurses were surveyed at three timepoints and were interviewed at conclusion of data collection. Analysis involved linear mixed-models for clinical data, descriptive statistics for binary and feasibility data, and content analysis for interview data.

RESULTS

Eleven patients and seven nurses completed. Protocol adherence was 94.4%. Two miscannulations occurred, both during standard cannulation. Cannulation time using POCUS guidance was significantly higher than standard cannulation (p = 0.008, 95% CI 39-166). All other variables showed no statistically significant difference. Content analysis of interview data showed cultural shift toward use of POCUS; nurses gained confidence and become more proficient in their POCUS technique.

CONCLUSIONS

Random-order crossover is a feasible design to measure differences in POCUS-guided and standard cannulation. It is also feasible to implement POCUS into hemodialysis centers and whilst POCUS guidance takes longer, nurses become more proficient, and confident with persistent use.

Evaluating the Effect of Nursing-Performed Point-of-Care Ultrasound on Septic Emergency Department Patients

Introduction Nursing-performed point-of-care ultrasound (NP-POCUS) studies have been performed on applications such as ultrasound-guided peripheral intravenous line placement and assessing bladder volume. However, research on the use of NP-POCUS in the management of septic patients remains limited. The purpose of this quality improvement study was to investigate how NP-POCUS could impact fluid treatment decisions affecting septic patients in the emergency department (ED) using a focused IVC and lung ultrasound protocol. Methods Nurses received standardized training in POCUS and performed inferior vena cava (IVC) and lung ultrasound scans on septic patients in the ED at predetermined intervals (hours: zero, three, and six). Based on their findings, they were asked to make recommendations on fluid management. Emergency physicians (EPs), both residents and attendings, are providing recommendations for fluid management without the use of ultrasound, which is being compared to the nurse-driven POCUS assessment of fluid management. EPs reviewed the NP-POCUS assessments of patient fluid status to determine nursing accuracy. Results A total of 104 patients were scanned, with a mean age of 60.7 years. EPs agreed with nursing ultrasound assessments in 99.1% of cases. Nursing ultrasound images changed management or increased physician confidence in current treatment plans 83.7% and 96.6% of the time, respectively. Before reviewing saved nursing ultrasound images, EPs underestimated fluid tolerance in 37.5% of cases, overestimated fluid tolerance in 26% of cases, and correctly estimated fluid tolerance (within 500 ml) in 36.5% of cases. Throughout resuscitation, IVCs became less collapsible, the number of cases with B-lines was essentially unchanged, and less fluid was recommended. Conclusion  This study demonstrated that nurse-performed POCUS is feasible and may have a meaningful impact on how physicians manage septic patients in the emergency department.

Intraoperative vascular mapping improves patient eligibility for arteriovenous fistula creation

BACKGROUND

We assessed the utility of intraoperative vein mapping performed by the operating surgeon for evaluating vessel suitability for arteriovenous fistula (AVF) creation.

METHODS

In a retrospective review of 222 AVFs, vein diameter measurements were compared between intraoperative and preoperative mapping in the same anatomical location. AVF creation was based on intraoperative vein diameter ≥2 mm, using a distal to proximal and superficial veins first approach. Potential selection of access type based on preoperative findings alone was analyzed.

RESULTS

The mean diameter of the veins used for AVF creation measured 3.6 ± 0.8 mm on intraoperative duplex versus 2.5 ± 0.9 mm when the same veins were measured on preoperative duplex. Based on preoperative mapping alone, 23% of patients would have received a more proximal AVF and 5% would have needed a graft. AVFs created more distally based on intraoperative findings had similar maturation rates compared to the rest of the cohort, 79% versus 84% (p = 0.2).

CONCLUSIONS

Intraoperative vein mapping can be used to evaluate vessel suitability for AVF and compared to pre-operative vein mapping may increase the eligibility of distal veins for fistula creation while reducing the need for AV grafts.

Vascular access management of hemodialysis patients at the bedside using point-of-care ultrasound

When vascular access (VA) for hemodialysis is established using an autologous fistula or synthetic graft, repeated damage from needle insertion at each dialysis session can lead to thrombosis, resulting in vascular stenosis or occlusion that can cause poor blood removal, elevated venous pressure, and other impairments of blood flow. Compact, high-performance ultrasound devices have been developed in recent years. Such devices are used for point-of-care ultrasound (POCUS), which has been used on many occasions for emergency evaluation in the dialysis room and is becoming an important tool in VA management. POCUS provides a wealth of imaging information, such as needle position, whether the needle is inside or outside the blood vessel, and lesion position, width, and depth. This allows clinicians to detect VA problems early and take suitable measures, such as changing the cannulation site, thereby avoiding the need for unnecessary and highly invasive angiography or surgical procedures.

Association of preoperative vein mapping with hemodialysis access characteristics and outcomes in the Vascular Quality Initiative

BACKGROUND

Preoperative vein mapping before arteriovenous fistula (AVF) or arteriovenous graft (AVG) placement has been debated as a possible method of improving hemodialysis access outcomes for patients. However, high-quality national studies that have addressed this relationship are lacking. Thus, we assessed the association of preoperative vein mapping with hemodialysis access configuration and outcomes.

METHODS

In the present cohort study, we analyzed all patients who had undergone AVF or AVG placement with data captured in the Vascular Quality Initiative hemodialysis access dataset from August 2011 to September 2019. The patients were stratified by whether they had undergone preoperative vein mapping. The primary (configuration) outcomes were access type (AVF vs AVG) and location (upper arm vs forearm). The secondary (longitudinal) outcomes were the successful initiation of hemodialysis, maintenance of secondary patency, and the need for reintervention 1 year after the index operation.

RESULTS

Overall, 85.6% of the 46,010 included patients had undergone preoperative vein mapping. Of the 46,010 patients, 76.1% and 23.9% had undergone AVF and AVG creation, respectively. AVF creation (77.6% vs 67.3%) and forearm location (54.6% vs 47.3%) were more frequent for the patients who had undergone preoperative vein mapping than for those who had not (P < .001). After adjusting for baseline differences between the groups, preoperative vein mapping was associated with increased odds of receiving an AVF vs AVG (adjusted odds ratio, 1.64; 95% confidence interval [CI], 1.55-1.75) and forearm vs upper arm access (adjusted odds ratio, 1.22; 95% CI, 1.16-1.30). The incidence of the loss of secondary patency was lower for patients with preoperative vein mapping (P < .001), and persisted after risk adjustment (adjusted hazard ratio, 0.81; 95% CI, 0.75-0.88).

CONCLUSIONS

Preoperative vein mapping was associated with favorable hemodialysis access configurations and outcomes in real-world practice. These data suggest that the use of preoperative vein mapping could improve the likelihood of favorable outcomes for patients requiring hemodialysis access.

[Vascular access for shunt devices]

In Germany approximately 70,000 patients with a renal insufficiency are treated by hemodialysis. The most frequent reasons for the need for dialysis are currently diabetic nephropathy and nephrosclerosis. Due to the increasing average age and the resulting multimorbidity of dialysis patients, the difficulties of medical care have also increased. Therefore, an interdisciplinary treatment of these patients is of great importance. An important point in the treatment is the choice of vascular access. This depends on the patient's concomitant diseases and on the urgency of hemodialysis. Vascular access is a prerequisite for dialysis and thus for the survival of the patient. A well-functioning dialysis access not only ensures the patient's survival but it is also important for the quality of life. The surgeon's task is therefore to create the optimal vascular access at the right time together with the treating nephrologist.

Upper limb anatomy and preoperative mapping

Vascular access is absolutely essential for haemodialysis due to its relationship with quality of dialysis and associated morbidity. Therefore, it must be monitored and continuously surveilled from the moment it is created to prevent failure in maturation and thrombosis. Multidisciplinary collaboration is necessary when the main aim is to achieve the adequate vascular access flow with the fewest possible complications. The starting point, and probably the main one, is vascular access planning. This planning requires both a deep understanding of the anatomy of the upper limb and enough skill to examine it by Doppler ultrasound. The aim of this article is to review the anatomical and haemodynamical concepts of the arterial and venous vascular tree and explain how to perform ultrasound mapping, optimising the technical resources provided by this tool. Likewise, adequate access creation criteria that minimise the risk of failure and associated complications will be discussed.

Current role of ultrasound in hemodialysis access evaluation

Physical examination (PE) is considered the backbone before vascular access (VA) placement, during maturation period and for follow-up. However, it may be inadequate in identifying suitable vasculature, mainly in comorbid patients, or in detecting complications. This review highlights the advantages of ultrasound imaging to manage VA before placement, during maturation and follow-up. Furthermore, it analyses the future perspectives in evaluating early and late VA complications thank to the availability of multiparametric platforms, point of care of ultrasound, and portable/wireless systems. Technical improvements and low-cost systems should favor the widespread ultrasound-based VA surveillance programs. This significant turning point needs an adequate training of nephrologists and dialysis nurses and the standardization of exams, parameters, and procedures.

Efficacy and Safety of Plastic Cannulae Compared with Metal Needles in the Initial Use of an Arteriovenous Fistulae in Incident Hemodialysis Patients: A Randomized Controlled Study

INTRODUCTION

Successful cannulation of an arteriovenous fistula (AVF) is important in patients starting hemodialysis (HD). Metal needles have been used for decades, but the usefulness of plastic cannulae has recently been demonstrated as a new technique.

METHODS

This was a prospective, randomized, open-label study of incident HD patients. Eligible patients were randomized into 2 groups in a 1:1 ratio (n = 45/group). Maturation of the AVF was confirmed using Doppler ultrasound prior to first needling, and 2 well-trained nurses implemented the AVF cannulation. The primary endpoint was the initial cannulation failure rate, defined as the failure of successful completion of 3 consecutive dialysis sessions. The secondary endpoints were time for hemostasis at the end of HD, degree of patients' pain, degree of cannulation difficulty felt by the nursing staffs, and achieving optimal HD adequacy.

RESULTS

The mean elapsed time from AVF creation to the first cannulation was 48.1 ± 16.7 days. A total of 17 cases of cannulation failure occurred, and the failure risk tended to be higher in the metal needle group than the plastic cannula group (hazard ratio 2.6, 95% confidence interval 0.95-7.41) after adjusting for age, gender, comorbidities, and AVF location. The overall incidence of vessel injury was higher and time for hemostasis was significantly longer in the metal group than the plastic group. The use of plastic cannula was associated with a better HD adequacy compared to a metal needle. However, the patients' pain score (p = 0.004) and nursing staff's cannulation difficulty score (p = 0.084) were higher in the plastic group, emphasizing the great importance of practice using plastic cannulae.

CONCLUSION

The vascular outcomes of plastic cannulae were much favorable compared to metal needles in incident HD patients. The use of plastic cannulae could be a new and innovative way to improve the quality of dialysis.

Point-of-care ultrasound in nephrology

PURPOSE OF REVIEW

The use of POCUS has grown tremendously with the introduction of innovative, easy-to-carry and maneuver hand-held devices. This review focuses on nephrology-centric applications of POCUS that can be incorporated on a daily basis to make impactful and prompt clinical decisions.

RECENT FINDINGS

We review articles covering use of POCUS in the dialysis unit, the Emergency Department, office, and ICU for assessment of volume status, access issues, stones, obstruction, and to help manage patients with AKI, shock, and heart failure.

SUMMARY

POCUS is a welcome addition to our bedside diagnostic armamentarium and has great utility in nephrology. Trials are ongoing in evaluating outcomes with POCUS and physicians' clinical experience using it has been extremely positive.