The type of vascular access and the effectiveness of haemodialysis

INTRODUCTION

Based on epidemiology data on chronic kidney disease (CKD), the occurrence rate oscillates between 9% and 15% of the studied population, which allows conclusion that about 10-11% of the global population has a certain stage of this condition. The results of the worldwide Global Burden of Disease 2017 research show that in 2017 the disease was present in about 697.5 million people (9.1%), as compared to 549.2 million in 2007, i.e. the incidence increased by 27%, and there were 1.2 million deaths due to this condition, as compared to 920 thousand in 2007 (increase by 34%) [1, 2]. In Poland, based on the NFZ (National Health Fund) registry, as well as epidemiology data, it is estimated that about 4.3 million people suffer from CKD at different stages, with about 15 thousand patients requiring renal replace-ment therapy each year [3]. Haemodialysis is a renal replacement therapy broadly used worldwide. Each dialysis should provide adequate elimination of medium- and small-molecule uraemic toxins [4]. The best way to determine whether the dialysis technique used in a given site is effective is to analyse patient survival, which depends on various factors, including age, comorbidities, the underlying cause of renal failure, therapy compliance, and the proficiency of the healthcare personnel taking care of the patient [5]. Dialysis efficiency can be determined based on urea reduction rate (URR) and urea clearance of the dialyser (Kt/V). These values are regularly calculated in most dialysis centres after patient blood tests performed monthly, where morphology parameters, such as electrolytes, including urea and potassi-um before and after the completed dialysis, are assayed. By assaying these parameters, one may check whether the dialysis parameters are suitable for the patient [6, 7]. Some factors that must be considered when adjusting the dialysis settings for the patient, include time, frequency of dialysis, type of biocompatible materials used, balance of calcium-magnesium metabolism, anaemia equilibration, and, most importantly, choosing the correct type of vascular access. Adequate dialysis is performed at least 3 times a week, and a single procedure is at least 4 hours long. Indices that show dialysis efficiency includes a urea dialysis rate that should be at least 70%. The second index is Kt/V, which should be above 1.3 [8, 11].

AIM OF THE STUDY

To ascertain whether the type of vascular access influences the effectiveness of haemodialysis.

MATERIAL AND METHODS

The research was retrospective. The study used the method of analysing medical records of patients undergoing dia-lysis at the University Hospital in the Department of Haemodialysis. Approval for the conduct of this study was obta-ined from the head of the Nephrology Clinic: Prof. Marek Kuźniewski, MD, PhD, and the head of the Department: Grzegorz Chmiel, MD, PhD. The study was conducted in concordance with the Declaration of Helsinki. The tools used included the following: discharge summaries, procedure protocols after exposure of vascular access, dialysis cards and results of laboratory tests from a period of 3 months (December, January, February) in 2018/2019. In order to verify whether various vascular access types influence the haemodialysis efficiency, the basic descriptive analyses were cal-culated as well as single-factor variance analysis. Tuckey’s multiple post-hoc comparison test was also used. For varia-bles measured in the nominal scale, structure numbers and indices – percentage values – were calculated. For all analy-ses, a significance value of 0.05 was adopted. The Fisher Snedecor test was used for the analysis – it examines whether the differences between the data are significant.

RESULTS

The study was conducted at the University Hospital in a group of 61 haemodialysed patients. In the study group 38 (61.67%) were men and 23 (38.33%) were women. Among 61 patients with grade 5 renal failure treated with haemo-dialysis, in 37 (i.e. 61.67%) the procedure was performed using arterio-venous shunt in the forearm. In 18 (i.e. 30%) patients, haemodialysis was performed using an indwelling catheter; in 4 (i.e. 6.67%) patients, arterio-venous shunt in the arm was used; only 1 (i.e. 1.67%) patient had a Gero-trex type implanted artificial vessel (Fig. 1).
The analyses that compared vascular access types with results of laboratory tests performed in December 2018 showed that the vascular access type influences the haemodialysis adequacy. Based on the analysis of urea re-moval rate and distribution volume clearance, the most effective dialysis was obtained via the arterio-venous shunt in the arm, and the least effective dialysis was that performed using the artificial vessel. In terms of potassium removal rate, dialysis using the indwelling catheter proved most effective (see Table 1).
Table 2 shows that there is a statistically significant relationship between the variety of vascular accesses and the value of iron (p = 0.03), while there is no statistically significant difference between the other variables depending on the vascular access used (p > 0.05).
Statistical analyses performed based on laboratory tests in 61 patients haemodialysed in January 2019 provi-ded results similar to those obtained earlier. The most effective dialysis was that via the arterio-venous shunt in the arm; slightly worse results were found in patients haemodialysed using the arterio-venous shunt in the forearm. The worst results were found for the patient haemodialysed using the artificial vessel (Table 3).
Analysing the results from January, a statistically significant difference was shown between the use of a particular type of vascular access and the value of iron (p = 0.001) and potassium after haemodialysis (p = 0.01). However, there is no statistically significant difference between the other variables depending on the given vascular access used (p > 0.05) (Table 4).
The analysis shown in Table 4 allowed us to conclude that a variety of venous access types significantly influ-ence the results of the potassium variable after haemodialysis (p = 0.01). To determine the groups with the largest signi-ficant differences, Tuckey’s multiple post-hoc comparison tests were applied.
Tuckey’s post-hoc multiple comparison test was used for a more detailed comparison of how particular vascu-lar accesses differentiated iron values, as can be seen in Table 5. The analysis shows that in the group with an arte-riovenous fistula on the arm, the iron level was statistically significantly higher than in the group with an arteriovenous fistula on the forearm (p = 0.04). In the arm arteriovenous fistula group, the average iron level was M = 16.288, while in the forearm arteriovenous fistula group, the average iron level was M = 9.4841. In the case of other artificial uses of the Gero-trex vessel or permanent catheter, no statistically significant differences were found at p > 0.05 (Table 5).
Data analysis allowed us to conclude that in the group with the arterio-venous shunt in the arm, the potassium level after the haemodialysis was statistically significantly higher than in the case of the indwelling catheter (p = 0.044). In the case of the other interactions, statistically significant differences were not found (p > 0.05).
The statistical analyses performed for chosen patients haemodialysed in February 2019 confirmed that the best haemodialysis results were obtained for patients with arterio-venous shunts in the arm, and slightly worse results were found for patients dialysed using the indwelling catheter and using the artificial vessel (Table 6).
Table 7 presents the results of the analysis comparing the influence of the variety of vascular accesses on the effectiveness of haemodialysis. It was found that the diversity of vascular accesses significantly differentiated only the results of the variable iron value (p = 0.002), while it did not differentiate the other values (p > 0.05).

DISCUSSION

The performed study shows that vascular access influences the efficiency of the performed haemodialysis. Based on statistical analyses, it was unequivocally found that the haemodialysis performed using an arterio-venous shunt made from the patient’s own vessels is the most efficient. In the study group, 61.67% of patients were dialysed using an arterio-venous shunt in the arm. This group obtained the best results. Mean median Kt/V value in patients with arterio-venous shunt in the arm was 1.6-1.7. In the group of patients with arterio-venous shunt in the forearm, which compri-sed 6.67% of the study population, Kt/V was 1.5-1.6. Patients with indwelling catheter comprised 30% of the study population; in this group the mean Kt/V was 1.4-1.5. The smallest group comprised 1 patient (1.67%) dialysed using an artificial vessel; here, the mean Kt/V values were the lowest, at 1.3. According to recommendations given in the source data, Kt/V in dialysed patients should be 1.3-1.4 [12].
All study patients had good results confirming that the procedure of systemic clearance was adequately indivi-dually chosen for each of them. Patients with organism detoxication via shunts had higher values than the recommen-ded ones. A study was performed in 2009 at the dialysis centre of the Public Regional Hospital in Suwałki, where dialy-sis adequacy was assessed using the Kt/V ratio. The study included 106 patients dialysed using an arterio-venous shunt and indwelling catheter. Blood flow and chemistry parameters were assayed; these analyses were the basis for assess-ment of dialysis adequacy. Better blood flow was found in patients dialysed via vascular access made using the pa-tient’s own vessels. The blood flow was slightly worse in patients with an indwelling catheter. In the study group, no rela-tionship between the type of vascular access and Kt/V value was found [13]. In a work by Ifudu et al., comparing the efficiency of dialysis in patients with naturally made vascular access and patients with implanted artificial PTFE prostheses, the authors concluded that artificial vessels do not allow a more efficient dialysis [14]. The results obtained in the study, similarly to the KDOQI recommendations, indicate that arterio-venous shunt made from the patient’s own vessels is the best type of vascular access, which should be used to dialyse patients. KDOQI indicates that up to 90% of patients should be dialysed using such access. It must be noted, however, that for various reasons, such as age or co-morbidities, it is not always possible to make a permanent vascular access. Vascular access must always be chosen individually for each patient [15].

CONCLUSIONS

Analysis of medical records performed between December 2018 and February 2019 has shown that the vascular access type influences the haemodialysis efficiency in patients dialysed at the University Hospital in Cracow. The va-scular access type influences the haemodialysis efficiency; the best results were obtained for patients dialysed using arterio-venous shunts, while the worst results were seen in patients haemodialysed using the artificial vessels. The ana-lyses show that in the group of patients with an arteriovenous fistula in the arm, the iron level was statistically signifi-cantly higher than in the group of patients with an arteriovenous fistula in the forearm. In the group with an arteriove-nous fistula in the arm, the average iron level was M = 16.288, while in the group with an arterio-venous fistula in the forearm, the average iron level was M = 9.4841, which was statistically significantly higher than in the case of perma-nent catheter (p = 0.044). In the case of other interactions, no statistically significant differences were found (p > 0.05).

Disclosure

The author declares no conflict of interest.