When Do Plasma Levels of Azotemic Indices Indicate Inadequacy of Peritoneal Dialysis?

Abstract

W h e n D o Plasma Levels of A z o t e m i c Indices Indicate In a d e q u a c y of Peritoneal Dialysis?D ear S i r , P lasm a c o n c e n t r a t i o n s o f creatinine great e r than 1 , 6 0 0 ¡ a m o l/l (18 m g/dl) and urea greater t h a n 3 5 m m o l /l (BUN >100 m g/dl) were p r o p o s e d a s indicators o f inadequate perito n eal d i a l y s i s [I, 2). However, the range o f p la sm a c o n c e n t r a t i o n s o f these two sub stances is a l m o s t id en tical in CAPD patients with c l i n i c a l m a n if e s ta tio n s o f inadequate di alysis a n d t h o s e adeq u ately dialyzed clini cally (3). T h u s , t h e u se o f plasma creatinine or urea c o n c e n t r a t i o n to assess the adequacy of p erito n eal d i a l y s i s is, in general, questionable [3]. We r e p o r t t w o cases illustrating the cir c u m s ta n c e s u n d e r w hich plasma creatinine is a strong i n d i c a t o r o f peritoneal dialysis inade quacy.Both p a t i e n t s w ere men on CAPD. Renal failure w a s c a u s e d by hypertensive nephro sclerosis a n d id io p a th ic proliferative glomer u lo n e p h r i tis . A g e a t onset o f CAPD was 39 and 43 y e a r s , resp ectiv ely . The first patient has h a d n o p e r i t o n i t i s o r exit site infection. The s e c o n d p a t i e n t h ad an exit site infection 7 m o n th s b e f o r e th e first clearance study and lost his p e r i t o n e a l cath eter to C andida parap silo sis p e r i t o n i t i s 6 m onths after the last c le a ra n c e s t u d y . A few m onths after the first study b o t h p a t i e n t s noticed progressive de crease i n d a i l y u rin ary volume followed within 2 -4 -m o n t h s by anorexia, decreased food i n t a k e a n d occasional vomiting. In ad dition, t h e f i r s t p atien t developed severe h y p e r t e n s i o n , w h ic h responded to increasing doses o f a n t i h y p e r t e n s i v e agents only after re d u c tio n o f b o d y w eight by 3 kg. The second patient d e v e l o p e d progressive neuropathy and i m p o t e n c e . Sequential 24-hour frac tional c l e a r a n c e o f urea and creatinine clear ance studies were performed. Instilled dialysate volumes did not change, at 10 l/day, between the first and second study in both patients. However, while the clearance in dices were in the adequate range (weekly fractional clearance of urea > 1.70, weekly creatinine clearance > 5 0 1/1.73 m:) in the first study, the second study produced inade quate clearance indices, primarily because of loss of urinary clearance. After the second study, instillation volume was increased to 16 liters daily in both patients. The first pa tient reported complete disappearance of the symptoms, while uremic symptoms persisted in the second patient. Instillation volume was further increased to 22 liters daily in the second patient with disappearance of an orexia and nausea and improvement of neur opathy.

Effect of Increased Hemodialysis Dose on Endogenous Erythropoietin Production in End-Stage Renal Disease

“…Additionally, clinical studies have shown that uremic anemia improves with better dialysis [5, 13, 14, 15, 16, 17, 18, 19, 20, 21]. Even before the emergence of recombinant erythropoietin, the two groups of patients with high blood urea nitrogen in the National Cooperative Dialysis Study [16] had significantly lower hematocrit values and greater blood transfusion requirements than their counterparts with low blood urea nitrogen levels.…”

“…Uremic anemia improves with good dialysis, with or without concomitant recombinant erythropoietin therapy [5, 13, 14, 15, 16, 17, 18, 19, 20, 21] – this has been attributed to enhanced extraction of uremic inhibitors of erythropoiesis, permitting improved erythropoiesis [22, 23, 24, 25]. …”

Controversies in renal anemia management

“…53 Evidence of the clinical validation of the role of uremic inhibitors of erythropoiesis comes from numerous reports that inadequate dialysis in patients sustained by either HD or continuous ambulatory peritoneal dialysis was associated with a poor response to EPO (persistently low Hb). [60][61][62][63][64][65][66][67][68][69][70][71][72][73][74][75] Several studies have also shown that Hb levels increased with an increase in HD dose in EPO-treated patients with low Hb. 26,62,69,74,75 In fact, the strong relation between Hb and adequacy of dialysis in patients with ESRD treated with EPO has been corroborated by analyses of pooled data at both the dialysis facility and the ESRD Network levels.…”

Evidence that Adequacy of Dialysis Modulates Uremic Anemia

“…Several investigators reported that inadequate dialysis in patients sustained by either hemodialysis [8, 9, 10, 11, 44, 45, 46, 47, 48]or CAPD [49, 50, 51]is associated with a poor response to EPO (persistent low hematocrit). Also, an increase in hemodialysis dose in EPO-treated patients with low hematocrits results in an increase in their hematocrit, simultaneous with a fall in endogenous EPO, suggesting enhanced removal of inhibitors of erythropoiesis [10, 55].…”