Characterization of hepatic and cardiac iron deposition during standard treatment of anaemia in haemodialysis.

BACKGROUND: Parenteral iron is integral in the treatment of anaemia of chronic kidney disease patients on haemodialysis (HD). However, increased liver iron concentration (LIC) can result from such treatment, and this correlates poorly with serum ferritin or transferrin saturation values. It is unclear whether increased cardiac iron concentration also occurs in this setting. We aimed to evaluate the relationship of intravenous iron supplementation to hepatic and cardiac iron deposition in chronic HD subjects. METHODS: A cohort of 10 patients on chronic HD for at least 1 year underwent MRI-based quantitation of hepatic and cardiac iron content to evaluate the relationship between intravenous iron supplements and hepatic and cardiac iron deposition. The results were compared against the cumulative parenteral iron dose and serum iron markers. RESULTS: The median age was 61 years (95% confidence interval (CI) 50-71), HD time 2.5 years (95%CI 2.0-5.3) and cumulative iron dose 4300 mg (95%CI 2110-9045). Hepatic iron concentration was elevated in eight of 10 subjects (median 46 mmol/kg, range 31-76). Cardiac iron levels were within the reference range in all subjects. There was poor correlation between conventional haematinic values and either LIC or cardiac iron levels. None of the study subjects exhibited elevated cardiac iron concentration. CONCLUSION: Whilst HD patients receiving standard parenteral iron therapy have elevated LICs, this is not associated with cardiac iron deposition. Transferrin saturation and serum ferritin levels are poor markers of either liver or cardiac iron deposition in HD subjects.

Therapeutic zinc and copper supplementation in acute diarrhea does not influence short-term morbidity and growth: double-blind randomized controlled trial.

Our objective was to evaluate the effect of zinc and copper supplementation in acute diarrhea on morbidity and growth during 12 weeks of follow-up. In a double-blind randomized controlled clinical trial of 724 children aged 6-59 months, none of the 11 evaluated outcomes showed significant association with zinc or zinc and copper supplementation. Thus, therapeutic zinc supplementation may not always yield short-term -benefits.

Roles of zinc in the pathophysiology of acute diarrhea.

Zinc has caught wide scientific attention for the conceptual promise it has to offer for prevention, control and treatment of acute diarrhea. This review focuses on the mechanisms by which zinc might contribute to the pathogenesis of acute diarrhea and the degree of success achieved in diarrhea control and treatment by zinc supplementation. Animal and in vitro studies have continued to fascinate the scientific fraternity and form a solid basis for the potential use of zinc supplementation against diarrhea. However, emerging evidence in terms of controlled studies in humans beckons a more complete understanding of the mechanistic basis for zinc supplementation. Current evidence indicates that studies specifically addressing the variability in response to zinc supplementation need to be undertaken to better comprehend these mechanisms.

What zinc supplementation does and does not achieve in diarrhea prevention: a systematic review and meta-analysis.

BACKGROUND: Prevention of diarrhea has presented indomitable challenges. A preventive strategy that has received significant interest is zinc supplementation. Existing literature including quantitative meta-analyses and systematic reviews tend to show that zinc supplementation is beneficial however evidence to the contrary is augmenting. We therefore conducted an updated and comprehensive meta-analytical synthesis of the existing literature on the effect of zinc supplementation in prevention of diarrhea. METHODS: EMBASE®, MEDLINE ® and CINAHL® databases were searched for published reviews and meta-analyses on the use of zinc supplementation for the prevention childhood diarrhea. Additional RCTs published following the meta-analyses were also sought. Effect of zinc supplementation on the following five outcomes was studied: incidence of diarrhea, prevalence of diarrhea, incidence of persistent diarrhea, incidence of dysentery and incidence of mortality. The published RCTs were combined using random-effects meta-analyses, subgroup meta-analyses, meta-regression, cumulative meta-analyses and restricted meta-analyses to quantify and characterize the role of zinc supplementation with the afore stated outcomes. RESULTS: We found that zinc supplementation has a modest beneficial association (9% reduction) with incidence of diarrhea, a stronger beneficial association (19% reduction) with prevalence of diarrhea and occurrence of multiple diarrheal episodes (28% reduction) but there was significant unexplained heterogeneity across the studies for these associations. Age, continent of study origin, zinc salt and risk of bias contributed significantly to between studies heterogeneity. Zinc supplementation did not show statistically significant benefit in reducing the incidence of persistent diarrhea, dysentery or mortality. In most instances, the 95% prediction intervals for summary relative risk estimates straddled unity. CONCLUSIONS: Demonstrable benefit of preventive zinc supplementation was observed against two of the five diarrhea-related outcomes but the prediction intervals straddled unity. Thus the evidence for a preventive benefit of zinc against diarrhea is inconclusive. Continued efforts are needed to better understand the sources of heterogeneity. The outcomes of zinc supplementation may be improved by identifying subgroups that need zinc supplementation.

Serum iron markers are inadequate for guiding iron repletion in chronic kidney disease.

BACKGROUND AND OBJECTIVES: Iron (Fe) overload may complicate parenteral Fe therapy used to enhance the efficacy of erythropoietic-stimulating agents in the treatment of anemia of chronic kidney disease. However, serum Fe markers are influenced by inflammation or malignancy and may not accurately reflect the amount of body Fe. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: We studied the relationship between parenteral Fe therapy, conventional serum Fe markers, and liver iron concentration (LIC) measured using magnetic resonance R2 relaxometry (FerriScan) in 25 Fe-deficient predialysis chronic kidney disease patients before and 2 and 12 weeks after single high-dose intravenous Fe and in 15 chronic hemodialysis patients with elevated serum ferritin (>500 µg/L). RESULTS: In predialysis patients, there was strong dose dependency between the administered Fe dose and changes in LIC at weeks 2 and 12; however, no dose dependency between Fe dose and changes in ferritin or transferrin saturation (TSAT) were observed. In hemodialysis patients, LIC correlated with the cumulative Fe dose and duration of dialysis but not with current ferritin or TSAT. The cumulative Fe dose remained a significant independent predictor of LIC in a multiple regression model. Two dialysis patients who received >6 g parenteral Fe had substantially elevated LIC >130 µmol/g, which is associated with hemochromatosis. CONCLUSIONS: In Fe-deficient predialysis patients, intravenous Fe therapy is associated with increases in LIC unrelated to changes in conventional Fe markers. In hemodialysis patients, TSAT and ferritin are poor indicators of body Fe load, and some patients have LICs similar to those found in hemochromatosis.

Influence of zinc supplementation in acute diarrhea differs by the isolated organism.

Zinc supplementation is recommended in all acute diarrheas in children from developing countries. We aimed to assess whether zinc supplementation would be equally effective against all the common organisms associated with acute diarrheas. We used data on 801 children with acute diarrhea recruited in a randomized, double blind controlled trial (ISRCTN85071383) of zinc and copper supplementation. Using prespecified subgroup analyses, multidimensionality reduction analyses, tests of heterogeneity, and stepwise logistic regression for tests of interactions, we found that the influence of zinc on the risk of diarrhea for more than 3 days depended on the isolated organism-beneficial in Klebsiella, neutral in Esherichia coli and parasitic infections, and detrimental in rotavirus coinfections. Although we found similar results for the outcome of high stool volume, the results did not reach statistical significance. Our findings suggest that the current strategy of zinc supplementation in all cases of acute diarrheas in children may need appropriate fine tuning to optimize the therapeutic benefit based on the causative organism, but further studies need to confirm and extend our findings.

Therapeutic value of zinc supplementation in acute and persistent diarrhea: a systematic review.

BACKGROUND: For over a decade, the importance of zinc in the treatment of acute and persistent diarrhea has been recognized. In spite of recently published reviews, there remain several unanswered questions about the role of zinc supplementation in childhood diarrhea in the developing countries. Our study aimed to assess the therapeutic benefits of zinc supplementation in the treatment of acute or persistent diarrhea in children, and to examine the causes of any heterogeneity of response to zinc supplementation. METHODS AND FINDINGS: EMBASE, MEDLINE and CINAHL databases were searched for published reviews and meta-analyses on the use of zinc supplementation for the prevention and treatment of childhood diarrhea. Additional RCTs published following the meta-analyses were also sought. The reviews and published RCTs were qualitatively mapped followed by updated random-effects meta-analyses, subgroup meta-analyses and meta-regression to quantify and characterize the role of zinc supplementation with diarrhea-related outcomes. We found that although there was evidence to support the use of zinc to treat diarrhea in children, there was significant unexplained heterogeneity across the studies for the effect of zinc supplementation in reducing important diarrhea outcomes. Zinc supplementation reduced the mean duration of diarrhea by 19.7% but had no effect on stool frequency or stool output, and increased the risk of vomiting. Our subgroup meta-analyses and meta-regression showed that age, stunting, breast-feeding and baseline zinc levels could not explain the heterogeneity associated with differential reduction in the mean diarrheal duration. However, the baseline zinc levels may not be representative of the existing zinc deficiency state. CONCLUSIONS: Understanding the predictors of zinc efficacy including the role of diarrheal disease etiology on the response to zinc would help to identify the populations most likely to benefit from supplementation. To improve the programmatic use of zinc, further evaluations of the zinc salts used, the dose, the frequency and duration of supplementation, and its acceptability are required. The significant heterogeneity of responses to zinc suggests the need to revisit the strategy of universal zinc supplementation in the treatment children with acute diarrhea in developing countries.

Zinc and copper supplementation in acute diarrhea in children: a double-blind randomized controlled trial.

BACKGROUND: Diarrhea causes an estimated 2.5 million child deaths in developing countries each year, 35% of which are due to acute diarrhea. Zinc and copper stores in the body are known to be depleted during acute diarrhea. Our objectives were to evaluate the efficacy of zinc and copper supplementation when given with standard treatment to children with acute watery or bloody diarrhea. METHODS: We conducted a double-blind randomized controlled clinical trial in the Department of Pediatrics at Indira Gandhi Government Medical College Nagpur, India. Eight hundred and eight children aged 6 months to 59 months with acute diarrhea were individually randomized to placebo (Pl), zinc (Zn) only, and zinc and copper (Zn+Cu) together with standard treatment for acute diarrhea. RESULTS: The mean duration of diarrhea from enrollment and the mean stool weight during hospital stay were 63.7 hours and 940 grams, respectively, and there were no significant differences in the adjusted means across treatment groups. Similarly, the adjusted means of the amount of oral rehydration solution or intravenous fluids used, the proportion of participants with diarrhea more than 7 days from onset, and the severity of diarrhea indicated by more than three episodes of some dehydration or any episode of severe dehydration after enrollment, did not differ across the three groups. CONCLUSION: The expected beneficial effects of zinc supplementation for acute diarrhea were not observed. Therapeutic Zn or Zn and Cu supplementation may not have a universal beneficial impact on the duration of acute diarrhea in children.

Influence of iron chelators on myocardial iron and cardiac function in transfusion-dependent thalassaemia: a systematic review and meta-analysis.

Iron chelators have dramatically prolonged the life expectancy of patients with transfusion-dependent thalassaemia, but their precise clinical benefit in reducing the myocardial iron burden and improving cardiac function is unknown. This systematic review and meta-analysis included published clinical trials that assessed the efficacy of iron chelators in regularly transfused patients of thalassaemia major for two commonly reported outcomes - myocardial iron content and left ventricular ejection fraction (LVEF). The meta-analysis of 392 patients for myocardial iron content and 291 patients for LVEF showed that (i) iron chelators reduced cardiac iron content by 23.9% (95% confidence interval 17.3-29.8%); (ii) there was no significant difference between the amount of iron reduced by deferoxamine and deferiprone (P = 0.9504); and (iii) LVEF was not significantly influenced by iron chelators - summary Hedge's g 0.13 (95% confidence interval -0.10-0.36). A significant publication bias existed for LVEF (Egger's P = 0.049) but not for myocardial iron (Egger's P = 0.871). Our results indicate that iron chelators significantly reduce myocardial iron content. Further, the choice of deferoxamine versus deferiprone may rest on factors other than their efficacy to reduce cardiac iron load.

High prevalence of ascorbate deficiency in an Australian peritoneal dialysis population.

BACKGROUND: An adequate total body pool of ascorbate is essential for optimum health in humans. Requirements for ascorbate are increased in peritoneal dialysis (PD) patients most likely due to a combination of poor nutrition and increased dialysate losses. METHODS: We measured serum ascorbate levels in 45 clinically stable PD patients to assess the prevalence of ascorbate insufficiency (level between 2 and 4 mg/L) and deficiency (level <2 mg/L). We also assessed the efficacy of subsequent supplementation and patients' adherence to the prescribed supplementation. All patients were advised on commencement of dialysis to take a multivitamin tablet containing 100-120 mg ascorbate. RESULTS: Eighteen (41%) PD patients were regularly taking ascorbate-containing multivitamins, while 27 (59%) patients did not take ascorbate supplements. Serum ascorbate levels ranged from <0.2 to 41 mg/L, with wide variations in serum ascorbate at any given intake level. Ascorbate deficiency was present in 1/3 of the current PD population (44% of patients not taking supplements and in 16% of those on supplements), although none of the patients demonstrated clinical manifestations of scurvy. Targeted supplementation of ascorbate insufficient patients increased the median serum ascorbate level from 1.7 mg/L (IQR 1.2-2.2) to 22.5 mg/L (IQR 16.7-32.9). CONCLUSION: Our results show that, in PD patients, ascorbate deficiency is common and can readily be identified with serum ascorbate measurements. Oral supplements in the form of inexpensive multivitamin preparations restore adequate serum ascorbate levels in the majority of these patients. We therefore suggest measurement of ascorbate levels in all PD patients at the commencement of dialysis with a target level in the normal range (4-14 mg/L).