|Year : 1996 | Volume
| Issue : 2 | Page : 29-33
The effect of hematocrit on the efficiency of hemodialysis in cases of chronic renal failure@
N Nand, S Arya, SK Mahajan, M Sharma, HK Aggarwal, P Kumar
Department of Medicine, Nephrology & Biochemistry, Pt. B.D. Sharma Medical College, Rohtak-124001, India
|Date of Submission||09-Aug-1995|
3/7 J Medical Enclave, Rohtak-124001
|How to cite this article:|
Nand N, Arya S, Mahajan S K, Sharma M, Aggarwal H K, Kumar P. The effect of hematocrit on the efficiency of hemodialysis in cases of chronic renal failure@. Indian J Med Sci 1996;50:29-33
|How to cite this URL:|
Nand N, Arya S, Mahajan S K, Sharma M, Aggarwal H K, Kumar P. The effect of hematocrit on the efficiency of hemodialysis in cases of chronic renal failure@. Indian J Med Sci [serial online] 1996 [cited 2013 May 24];50:29-33. Available from: http://www.indianjmedsci.org/text.asp?1996/50/2/29/11601
Chronic Renal failure is associated with high degree of mortality and morbidity. Dialysis is an important mode of treatment in these cases. As most of the patients of chronic renal failure are anemic and most of the studies , done in them were with low hematocrit, very little is known about the effect of rise in hematocrit on the efficiency of dialysis. Anemia could be corrected by either recombinant human erythropoietin , or transfusion of whole blood. Kt/V which is an index of the adequacy of dialysis and is being used frequency of dialysis, where K is the clearance of a particular solute (ml/mt), V is the volume of distribution of solute and T is the Cialysis time (min.).  Therefore, to know whether there was any change in the efficiency of hemodialysis following rise in the hematocrit, we studied 20 cases of chronic renal failure where he Kt/V of urea, creatinine and phosphates was compared following I and II dialysis (low Hct vs high Hct) by increasing the hematocrit by transfusion of 2 units (600700 ml) of whole blood.
| ¤ Materials and Methods|| |
Twenty adult patients (14 males, 6 females) of chronic renal failure participated in the study. The mean age of males was 44.2±14.31 years (range 25-70 years) and that of females was 33.5±3.14 (range 28-37 years). Study included 20 cases with chronic renal failure (12 chronic glomerulonephritis, 3 chronic pyelonephritis, 2 obstructive uropathy and 3 miscellaneous). Patients with bleeding tendencies, positive surface antigen, positive for antibody to human immunodeficiency virus, unstable hemodynamically were excluded from the study.
The amount of solute removed during hemodialysis was assessed by Kt/V. It was determined twice in individual patients i.e. once with a low hematocrit level and again when the hematocrit was raised by a minimum of 10% by transfusion of 2 units of whole blood. Each dialysis was of 4 hours duration with an interdialytic interval of 4872 hours. The parameters like blood flow rate (approx. 200 ml/ min), dialysate flow rate (approx. 500 ml/min), temperature, conductivity, pressure of dialysate, tubings, angioaccess, recirculation time, duration of dialysis, heparinisation schedule, were kept constant during both the dialysis. Kt/v was calculated following individual dialysis, and was compared between the two dialysis (low Hct vs. high Hct). Kt/v was also correlated with hematocrit. Blood was collected at 0 minute (predialysis), 60 minutes, 120 minutes (mid dialysis), 180 minutes, 240 minutes (post dialysis), during both the dialysis and urea, creatinine and phosphates were estimated. Henceforth blood clearances (kb), dialysate clearances (kd), fractional decrement of solutes (urea, creatinine and phosphates) were calculated and compared between I and it dialysis. Dialysis was done by Drake Willock hemodialysis machine, by using 1 m2 cuprophane hollow fibre dialyser and with acetate as buffer. The dialyser was not reused. A written informed consent was obtained from the patients and the study was duly approved by the Research Committee and Ethics Committee.
Calculations : The following formula were used to calculate blood clearance (kb), dialysate clearances (kd), volume of distribution of solute (V), Fractional decrement. 1. kb = pre-post-post x blood flow rate. 2. kd = V/Td. log (n) C 2 /C 2 3. V = Total body water (TbW) (Its) (men = 0.297 B.W. (kg) + 0.195 height (cms) - 14.013 (women) = 0.184 B.W. (kg) + 0.345 height (cms) - 35.27. 4. Fractional decrement = pre-post/pre x 100.
C 2 and C 2 are solutes concentration at the beginning and end of hemodialysis. Td is the duration of dialysis. The data are expressed as mean ±SD. Linear regression analysis and students 't' test for paired data were employed for statistical evaluation.
| ¤ Results|| |
Changes in Hematocrit : All the patients were transfused 2 units (600-700 ml) of whole blood after the dialysis and hematocrit was raised from a mean of 22.2 ± 5.09% to 33.02 ± 4.95%. It was observed that the blood clearances of urea, creatinine and phosphates decreased significantly and there was a significant decrease in dialysate clearances of solutes (urea, creatinine and phosphates) following an increase in hematocrit. The fractional decrement of solutes when compared between the I and II dialysis also showed a significant decrease. [Table 1].
Effect of Kt/v of solutes : Urea kinetics as shown in [Table 1], depicts a significant decrease in Kt/v of solutes following rise in the hematocrit. The Kt/v when plotted with Hct, showed that the linear regression analysis of urea, creatinine and phosphates had negative correlation, which was very significant in case of creatinine and phosphate and insignificant in case of urea, meaning Thereby that an increase in the hematocrit following blood transfusion lead to a significant decrease in the removal of creaticiency of dialysis decreased signinine& phosphate i.e. the efficantly, whereas no change in the efficiency of dialysis was pobserved as regards to urea.
| ¤ Discussion|| |
In the present study there was a significant decrease in the efficiency of hemodialysis, following increase in hematocrit. It was highly significant for all solutes (urea, creatinine and phosphate) p<0.001 [Table 1]. Similarly blood clearances, dialysate clearances and fractional decrement also showed a significant fall with high hematocrit hemodialysis. The efficacy of hemodialysis is dependant on several factors like duration of dialysis, dialysate/blood flow rates, ultrafiltration, recirculation time, dialysate pressure, arterial & venous pressure& viscosity of blood etc. In the present study all the above mentioned factors were kept constant except the viscosity of blood, which was mainly dependant on the type and the amount of plasma proteins and the hematocrit. Vonalbertini et al  showed negligible effect of plasma proteins on the efficiency of dialysis in uremic subjects. Hence for all practical purposes viscosity is mainly dependant on the hematocrit of blood.
Therefore, increase in hematocrot results in an increase in the viscosity of blood, which further increases the red cell mass and the whole blood volume. This leads to an increase in obligatory fluid loss and perhaps back diffusion of dialysate, leading thereby to decrease in clearances and the efficiency of high hematocrit hemodialysis. Since the results of National Cooperative Dialysis study have been published, Kt/V and urea kinetics modeling are used to evaluate the efficiency of dialysis. In this study Kt/V of 20 patients of renal failure with a mean hematocrit of 22.2 ± 5.09 following an hematocrit. The Kt/V of creatinine and phosphates showed significant inverse correlation with hematocrit whereas Kt/V of urea did, not show a significant negative correlations meaning thereby that the efficiency of dialysis was reduced, as creatinine and phosphates were underdialysed and no effect was observed in cases of urea by increasing hematocrit. Movilli et al  similarly showed a fall in Kt/V solutes as hematocrit was increased. This could be probably explained by lesser degree of equilibrium in the levels of solutes (creatinine and phosphate) between R.B.C. and plasma as compared to urea which has a higher degree of equilibrium at high hematocrit levels. , This variation could also be explained by the different rates of diffusion of solutes across the red blood cells, e.g. clearance of molecules or solutes with slower red cell to plasma transfer rates would be more susceptible and there removal following dialysis would be affected. Creatinine has a RBC/ plasma ratio of 0.731 with a red cell to plasma transfer rate of 4.4% min, as compared to urea which has a much higher ratio of 0.859 and it diffuses from RBC to plasma instantaneously. Hence when hernatocrit was raised the Kt/V of creatinine and phosphate decreased more as compared to urea. The Kt/V, which is an indicator of the efficiency of dialysis showed a significant decrease with high hematocrit dialysis, especially for solutes having slow coefficient of transfer. This could suggest the possibility of underdialysis and decreased efficiency of hemodialysis for creatinine, phosphates and other solutes in renal failure associated with normal hematocrit such as patents of acute renal failure, chronic renal failure with polycystic kidney. Therefore, in such situations the prescription of hemodialysis needs to be modified in order to improve the efficiency of hemodialysis.
| ¤ Summary|| |
Twenty patients of chronic renal failure were evaluated to study the effect of increase in hematocrit (Hct) on the efficiency of hemodialysis. All the patients were subjected to two hemodialysis of identical duration with an interdialytic interval of 48 hours. All were anemic with a mean hemoglobin of 6.73 gm% and a hematocrit of 22.2%. Hematocrit was raised to a mean of 32.02% following transfusion of 2 units (600-700 ml) of whole blood (p<0.001) in the interdialytic interval. Blood clearances (Kb). Dialysate clearance (Kd), fractional decrement and Kt/V ratio of solutes (urea, creatinine and phosphates) were calculated during both the dialysis and compared with each other. Kt/V of urea decreased from 1.0589 ± 0.24 to 0.89 ± 0.15 (p< 0.001), and that of creatinine 1.003 ± 0.19 to 0.832 ± 0.009 (p< 0.001) and phosphates 0.992 ± 0.16 to 0.826 ± 0.006 (p<0.001) and it showed a negative correlation with rise in hematocrit. It was significant for creatinine and phosphates and insignificant for urea, suggesting thereby that the efficiency of dialysis decreased with increase in hematocrit. This is important in view of under dialysis in patients of normal or near normal hematocrit and suggests the need for modification of dialysis prescription in such situations.
| ¤ References|| |
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|2.||Lim VS, Flanigan MJ, Fangman J. Effect of hematocrit on solute removal during high efficiency hemodialysis. Kidney Int 1990; 37:1557-1559. [PUBMED] [FULLTEXT] |
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