An evaluation of the effectiveness of the sonogram and the clinical determination of the arterio-venous fistula site in the diabetic population entering the chronic haemodialysis program

Abstract

Diabetic nephropathy is a serious complication of diabetes that can lead to end stage renal failure (ESRF). It is now the most common cause of ESRF in patients accepted onto renal replacement therapy (RRT) programmes. Kidney disease is common in South Africa. 60-65% is due to inherited hypertension and 20-25% due to Type 2 diabetes (National Kidney Foundation of South Africa, 2002). The renal replacement therapies include haemodialysis, peritoneal dialysis and transplantation.

Successful long-term haemodialysis in patients with end stage renal disease (ESRD) depends to a large extent upon a trouble- free vascular access. Achieving a successful vascular access remains a challenge especially in the diabetic population.

Current Kidney Dialysis Outcome Quality Initiative (KDOQI) guidelines encourage placing Arterio-Venous Fistula (AVF) in more haemodialysis patients. While the upper limb is the preferred site for AVF creation, researchers are undecided on which is the ideal location (distal or proximal arm) in the diabetic population. Many new fistulae fail to mature sufficiently to be usable for haemodialysis. Pre-insertion work-up with regard to haemodialysis access is important in maintaining the most appropriate access in the growing diabetic population requiring haemodialysis. Pre-operative vascular mapping to identify suitable vessels has been reported to improve vascular access outcomes . In South Africa, duplex scanning is not routinely done, and a clinical judgement by the surgeon remains in most instances the deciding factor on the site of the AVF. Whilst conducting this research, it has been found that while diabetic patients may have AVF created, the maturation time is of a much extended period, and a challenge to achieve the desired dose of dialysis.

This is a prospective, quantitative and qualitative study of 21 diabetic patients. These included patients that were starting on the chronic haemodialysis program and limited to patients that were having first attempt of AVF creation and aims to

establish if sonogram testing provides a more accurate measure of the ideal location for the AVF, or if a clinical evaluation alone by the surgeon is sufficient. Surgical techniques are different amongst surgeons and clinical evaluation is more a subjective decision. By limiting the surgeons performing the AVF, a standardized surgical procedure was established. If an ideal AVF access for the patient is created, haemodialysis efficiency is increased and ultimately patient outcome improved.

The AVF was created according to the clinical evaluation as is the current process, and the surgeons were not aware of the duplex sonogram results. Failure and success of AVF were analysed according to primary patency and functional success. A primary patency success of the AVF does not guarantee functional success.

If an AVF is not able to complete an entire haemodialysis session trouble free at the prescribed dialysis dose, the AVF is considered a failure irrespective of primary patency success. This was evident with 10% of patients who had primary patency but functional success was not achieved. With a 55% functional success in this study with AVF created on clinical evaluation, there was no significance difference (p=0.795) if AVFs were based on duplex sonogram findings. However, there was evidence of increased AVF success in 33% of the failed AVFs when the new AVFs were created at the duplex sonogram site. 95% of patients in this study had commenced haemodialysis with a Central Venous Catheter (CVC). AVF success could be increased if early referral of diabetic patients for permanent access to the surgeon occurred. Maturation rate of AVF differed from KDOQI guidelines with AVF first cannulation only after 17 weeks, and not after the recommended time of 6 weeks. Blood flow rates on dialysis also varied with international standards, with only maximum of 400mls/min reached after one year. With distal arm AVF, diameter of radial artery of less than 2mm and cephalic vein less than 3mm was associated with AVF failure. This research study represents the first of its kind in Kwazulu Natal looking at vascular access sites in diabetic patients with End Stage Renal Disease on haemodialysis.