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Abstract
Forty-three patients on chronic hemodialysis who before the present study had only
received a low-dose supplement of folic and ascorbic acid were studied prospectively
for one year. After baseline values were obtained in month one, increasing doses of
postdialysis vitamin supplements were prescribed for the vitamins which were found
to be insufficient in order to determine the minimal amount of oral postdialysis supplement
necessary to normalize vitamin levels. According to our results no systematic supplement
was indicated for biotin, riboflavin or vitamin B12. For folic acid and vitamin C,
supplementation with lower doses than those prescribed in many dialysis units allowed
optimal vitamin levels in the majority of patients; 2 to 3 mg/week (300 to 400 micrograms/day)
of folic acid and of 1000 to 1500 mg/week (150 to 200 mg/day) of vitamin C was considered
sufficient. A severe pyridoxine deficiency was present in most (> 80%) unsupplemented
patients, either as judged by pyridoxal-5-phosphate determinations in plasma or determination
of specific enzyme activation in erythrocytes (EGOTo and alpha-EGOT); a postdialysis
supplement of at least 100 to 150 mg/week of pyridoxine hydrochloride (> 15 to 20
mg/day) corrects this deficiency. The activity of the thiamine-dependent enzyme transketolase
in erythrocytes (ETKo) was insufficient in 35% and marginal in 21% of the patients,
while whole blood thiamine determined simultaneously in 10 of the ETKo-deficient patients
was within the normal range. These results suggest that in uremia insufficient transketolase
activity may be related to inhibition of the enzymatic system rather than to true
vitamin deficiency. On a long-term basis a supplement of 200 to 300 mg/week of thiamine
hydrochloride (30 to 45 mg/day) restored ETKo to satisfactory levels in most patients;
whether this supplement is to be recommended warrants further studies.