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Saudi Journal of Kidney Diseases and Transplantation
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Year : 2015  |  Volume : 26  |  Issue : 1  |  Page : 144-148
Barriers to adequate urea clearance among hemodialysis patients in developing countries: An example from the Sudan

1 Khartoum Teaching Hospital Renal Unit, Khartoum, Sudan
2 Faculty of Medicine, University of Khartoum, Khartoum, Sudan

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Date of Web Publication8-Jan-2015

How to cite this article:
Abdelwahab HH, Shigidi MM. Barriers to adequate urea clearance among hemodialysis patients in developing countries: An example from the Sudan. Saudi J Kidney Dis Transpl 2015;26:144-8

How to cite this URL:
Abdelwahab HH, Shigidi MM. Barriers to adequate urea clearance among hemodialysis patients in developing countries: An example from the Sudan. Saudi J Kidney Dis Transpl [serial online] 2015 [cited 2021 Mar 4];26:144-8. Available from: https://www.sjkdt.org/text.asp?2015/26/1/144/148766
To the Editor,

End-stage renal disease (ESRD) is an emerging health problem in Sudan with extremely limited facilities for treatment. All forms of renal replacement therapy (RRT) are funded by the government of Sudan and provided free of charge. Similar to most developing countries, the cost of treating hemodialysis (HD) patients is escalating and often beyond the proposed budgets. [1],[2],[3],[4]

In Sudan, HD remains the main modality of RRT seen in 69% of the treated ESRD patients. [1],[5] Because of financial constraints, the prescribed HD is often below the recommended number of sessions per week, with most patients being provided twice-weekly HD. [1] For practical purposes, the urea reduction ratio (URR) has been used as an approximate method for assessing urea clearance rather than the formal urea kinetic modeling; it has remained the most commonly used parameter to assess the dialysis dose in all our HD units. [1],[6],[7] As per the National Kidney Foundation Kidney Disease Outcomes Quality Initiative (KDOQI) recommendations, adequate clearance is determined by a URR of not less than 65%. [8]

In order to compensate for the reduced number of weekly dialysis hours, most HD units try to achieve maximum urea clear clearance during individual HD sessions, although limitations are often seen. In this study, we aimed to evaluate the barriers to adequate urea clearance during HD sessions among adult Sudanese patients on maintenance intermittent HD.

A hospital-based cohort study was conducted at the Khartoum Teaching Hospital Renal Unit during the period from June to December 2010. All adult patients with ESRD on maintenance intermittent HD were included in the study. Those who were 15 years of age or below, on HD for < 3 months, refused to give consent for enrollment and/or on other dialysis modalities were excluded from the study.

A total of 210 patients were enrolled in the study. Using a specially designed questionnaire, patients were reviewed regarding their demographic characteristics and followed-up for two months during which their HD treatment data were recorded. After the initial two months of follow-up, 100 patients were randomly selected for the assessment of urea clearance using the simplified URR formula; blood urea concentration preand post-dialysis were measured using the slow pump technique. [6] Randomization of patients was performed using a card withdrawal method. All necessary investigations were performed in the Central Laboratory, Khartoum Teaching Hospital.

Statistical analysis of data was made using Statistical Package for Social Sciences version 17.0 (SPSS Inc., Chicago, IL, USA) computer software. Patients' characteristics and HD treatment data were expressed as frequencies and percentages and correlated with the determined URR. Significance of data was tested using the chi-square test with a P-value < 0.05 being considered as statistically significant.

The study was approved by the ethics committee of the Sudan Medical Specialization Board and Khartoum Teaching Hospital Renal Unit.

Males represented 59% of the studied population; 73% were on maintenance HD for >1 year. Based on the URR, among the 100 adult HD patients studied, 58% were labeled as having adequate solute clearance with URR of not less than 65%. Female patients were having significantly more adequate dialysis compared with males (P < 0.0005). Patients' age, residence, education level, employment and duration on HD did not significantly influence the adequacy of dialysis sessions and urea clearance (P >0.05). Adequate urea clearance was seen in 72.7% of the patients having good residual renal function compared with 40% among those with inadequate residual renal function; the difference was statistically significant (P = 0.001, [Table 1]).
Table 1: Patients' characteristics and the frequency of adequacy urea clearance.

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Regarding HD treatment data, two-thirds of the patients were on twice-weekly HD. Patients on thrice-weekly HD were mostly anuric or could not tolerate fluid overload. All patients were on HD via permanent vascular accesses, with functioning arteriovenous fistulae seen in 74% of the patients. Universal biocompatible polysulfone 1.5 m 2 low-flux dialyzers were used for all patients. All patients were dialyzed using a dialysate flow rate of 500 mL/min and only bicarbonate-based dialysis solutions were used. Reuse of dialyzers is not practiced in our unit. Frequent intra-dialytic complications were seen in 33% of the patients; these were mainly in the form of intra-dialytic hypotension (54.5%), muscle cramps (18.2%) and others (27.3%). Neither the type of permanent vascular access nor the ultrafiltration volume during HD significantly influenced the adequacy of urea clearance (P >0.05). The number of weekly HD sessions, blood flow rate, dialysis hours, patients' dry weight and the presence of intra-dialytic complications were all found to statistically influence the URR (P < 0.05, [Table 2]).
Table 2: Hemodialysis treatment data and its impact on adequate urea clearance.

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The survival and well being of HD patients are strongly related to dialysis adequacy and measurement of the HD dose. [9] According to international guidelines, HD is considered mi nimally adequate when the Kt\v urea is equal to or more than 1.2, which is equivalent to a URR of not less than 65%. [10]

Adequate urea clearance was mostly seen among those between 15 and 30 years of age; this group represented 20% of the studied population. It was clear that the percentage of patients with adequate URR tends to drop with increase in age. These findings were not statistically significant, but remain in consistence with other published reports. [11] Elderly patients tend to have more co-morbid conditions interfering with set dialysis prescriptions and, accordingly, dialysis adequacy.

Patients who were on thrice-weekly HD had better urea clearance when compared with patients receiving twice-weekly sessions (P = 0.01). Various reports have shown increasing morbidity and mortality among HD patients receiving less-frequent weekly sessions. [12] The survival advantage reported with twice-weekly HD by few centers is likely to be confounded by patient selection and the presence of greater residual renal function. [13]

The type of HD vascular access remains one of the important determinants of dialysis adequacy. Certain types of vascular accesses were known to be associated with increased complications, reduced quality of life and patient survival. [14] Among our patients, all were on HD via some form of permanent vascular access; no statistically significant differences in urea clearance were observed among the various types of access used. [6] Significantly higher URR was seen in those dialyzed with blood flow rates of more than 250 mL/min (P = 0.02). The blood flow rate during HD has a considerable relationship to the urea clearance and HD adequacy; however, patients' tolerance, hemodynamic status and the use of suitable size dialyzers should all be taken into consideration. [15]

In Sudan, the total number of patients requiring RRT is by far exceeding the available treatment facilities. Despite that, all patients were prescribed four hours HD sessions. Practically, only 68% of our patients completed the four hours dialysis sessions. The reasons for interrupted HD sessions among our patients included late arrival, delayed initiation of dialysis, intra-dialytic complications and patients' non-adherence, often leading to a large gap between the prescribed and the delivered dialysis dose. [16] Short dialysis sessions often cause impaired control of fluid volume and reduced clearance of middle size molecules, which are known independent predictors of patients' outcome. [17] On the other hand, longer dialysis sessions provide better tolerance of ultrafiltration, less-frequent intra-dialytic hypotensive episodes and better control of blood pressure, and were independently associated with lower mortality. [16] Increasing the duration of HD sessions to more than four hours might be a useful method for improving urea clearance and patients' mortality, but often hindered by patients' intolerance and cost. [18]

A U-shape relationship exists between fluid balance and mortality among HD patients. Excessive ultrafiltration might be a serious threat to the heart and patients' residual renal function. [11] Among our patients, no clear association was found between ultrafiltration rates and the adequacy of urea clearance.

In conclusion, the number of patients with ESRD in Sudan is escalating and is far beyond the estimated budgets for renal care. Most ESRD patients are on twice-weekly HD. Reasons for reduced urea clearance during HD are mostly short or interrupted sessions, reduced dialysis frequency, low blood flow rates, use of small surface area dialyzer and loss of residual renal function.

Conflict of interest: None

   References Top

Elamin S, Obeid W, Abu-Aisha H. Renal Replacement Therapy in Sudan, 2009. Arab J Nephrol Transplant 2010;3:31-6.  Back to cited text no. 1
Naicker S. End-stage renal disease in subSaharan and South Africa. Kidney Int Suppl 2003;83:S119-22.  Back to cited text no. 2
Barsoum RS. End-stage renal disease in North Africa. Kidney Int Suppl 2003;83:S111-4.  Back to cited text no. 3
Bamgboye EL. Hemodialysis: Management problems in developing countries, with Nigeria as a surrogate. Kidney Int Suppl 2003;83:S93-5.  Back to cited text no. 4
Abu-Aisha H, Elhassan EA, Elamin S. The Sudan peritoneal dialysis program: Three years of momentum. Arab J Nephrol Transplant 2009;2:23-7.  Back to cited text no. 5
Couchoud C, Jager KJ, Tomson C, et al. Assessment of urea removal in hemodialysis and the impact of the European Best Practice Guidelines. Nephrol Dial Transplant 2009;24:1267-74.  Back to cited text no. 6
European Best Practice Guideline on dialysis strategies. Nephrol Dial Transplant 2007;22: ii5-21.  Back to cited text no. 7
Port FK, Ashby VB, Dhingra RK, Roys EC, Wolfe RA. Dialysis dose and body mass index are strongly associated with survival in hemodialysis patients J Am Soc Nephrol 2002;13:1061-6.  Back to cited text no. 8
Held PJ, Port FK, Wolfe RA, et al. The dose of hemodialysis and patient mortality. Kidney Int 1996;50:550-6.  Back to cited text no. 9
Frankenfield DL, McClellan WM, Helgerson SD, Lowrie EG, Rocco MV, Owen WF Jr. Relationship between urea reduction ratio, demographic characteristics, and body weight for patients in the 1996 National ESRD Core Indicators Project. Am J Kidney Dis 1999;33:584-91.  Back to cited text no. 10
Termorshuizen F, Dekker FW, van Manen JG, Korevaar JC, Boeschoten EW, Krediet RT, NECOSAD Study Group. Relative contribution of residual renal function and different measures of adequacy to survival in hemodialysis patients: An analysis of the Netherlands Cooperative Study on the Adequacy of Dialysis (NECOSAD)-2. J Am Soc Nephrol 2004;15:1061-70.  Back to cited text no. 11
Lambie SH, Taal MW, Fluck RJ, McIntyre CW. Analysis of factors associated with variability in haemodialysis adequacy. Nephrol Dial Transplant 2004;19:406-12.  Back to cited text no. 12
Lin X, Yan Y, Ni Z, et al. Clinical Outcome of Twice-Weekly Hemodialysis Patients in Shanghai. Blood Purification. Blood Purif 2012;33:66-72.  Back to cited text no. 13
Powers KM, Wilkowski MJ, Helmandollar AW, Koenig KG, Bolton WK. Improved urea reduction ratio and Kt/V in large hemodialysis patients using two dialyzers in parallel. Am J Kidney Dis 2000;35:266-74.  Back to cited text no. 14
Ifudu O, Mayers JD, Matthew JJ, Fowler AM, Homel P, Friedman EA. Standardized hemodialysis prescriptions promote inadequate treatment in patients with large body mass. Ann Intern Med 1998;128:451-4.  Back to cited text no. 15
Charra B, Scribner BH, Twardowsky ZJ, Bergstrom J. The middle molecule hypothesis revisited. Should short, three times weekly hemodialysis be abandoned? Hemodial Int 2002;6:9-14.  Back to cited text no. 16
Twardowski ZJ. Treatment time and ultrafiltration rate are more important in dialysis prescription than small molecule clearance. Blood Purif 2007;25:90-8.  Back to cited text no. 17
Saran R, Bragg-Gresham JL, Levin NW, et al. Longer treatment time and slower ultrafiltration in hemodialysis: Associations with reduce mortality in the DOPPS. Kidney Int 2006;69:1222-8.  Back to cited text no. 18

Correspondence Address:
Dr. Mazin M. T. Shigidi
Department of Medicine, Faculty of Medicine, University of Khartoum, P.O. Box 10179, Post Code 11111, Khartoum, Sudan
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DOI: 10.4103/1319-2442.148766

PMID: 25579738

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