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.
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