Zinc and copper urinary excretions in children with burns and scalds

Toward revising dietary zinc recommendations for children aged 0 to 3 years: a systematic review and meta-analysis of zinc absorption, excretion, and requirements for growth

CONTEXT

The Food and Agriculture Organization of the United Nations and the World Health Organization are updating their dietary zinc recommendations for children aged 0 to 3 years.

OBJECTIVE

The aim of this review was to retrieve and synthesize evidence regarding zinc needs for growth as well as zinc losses, absorption, and bioavailability from the diet.

DATA SOURCES

MEDLINE, Embase, and Cochrane Library databases were searched electronically from inception to August 2020. Studies assessing the above factors in healthy children aged 0 to 9 years were included, with no limits on study design or language.

DATA EXTRACTION

Ninety-four studies reporting on zinc content in tissue (n = 27); zinc absorption (n = 47); factors affecting zinc bioavailability (n = 30); and endogenous zinc losses via urine, feces, or integument (n = 40) met the inclusion criteria. Four reviewers extracted data and two reviewers checked for accuracy.

DATA ANALYSES

Studies were synthesized narratively, and meta-analyses of zinc losses and gains as well the subgroups of age, type of feeding, country's income, and molar ratio of phytate to zinc were conducted. Meta-analysis revealed an overall mean (95%CI) urinary and endogenous fecal zinc excretion of 17.48 µg/kg/d (11.80-23.15; I2 = 94%) and 0.07 mg/kg/d (0.06-0.08; I2 = 82%), respectively, with a mean fractional zinc absorption of 26.75% (23.69-29.81; I2 = 99%). Subgrouping by age revealed differences in mean values associated with the transition from milk-based diets to solid food during the first 3 years of life.

CONCLUSION

This review synthesizes data that may be used to formulate zinc requirements in young children. Results should be interpreted with caution because of considerable heterogeneity in the evidence.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration number CRD42020215236.

Impaired zinc and copper status in children with burn injuries: need to reassess nutritional requirements

Major burns are associated with impaired Zn and Cu status. These micronutrients are essential for bone matrix formation, linear growth, and wound healing. This study evaluated the status of Zn and Cu in burned children and assessed adequacy of supplementation. Six children, mean total body surface area (TBSA), 54+/-9% (S.D.), were recruited. Nutrient intakes, plasma, wound exudate, and 24h urine samples were collected and analyzed for Zn and Cu. Bone mineral content was assessed by dual energy X-ray absorptiometry. Dietary Zn and Cu were three times the dietary reference, and mean plasma concentrations of Zn and Cu were low at admission and discharge. Urinary Zn was elevated at admission, whereas Cu was elevated at both times. Wound Zn and Cu concentrations exceeded plasma concentrations, suggesting that inflammatory wound exudate was a primary route of loss. We demonstrate that burn injury in children results in low plasma levels of Zn and Cu that are inadequately compensated during hospitalization.

Cyclopentanone Thiosemicarbazone, a New Complexing Agent for Copper Determination in Biological Samples by Adsorptive Stripping Voltammetry

A selective and sensitive stripping voltammetric method for the determination of trace amounts of copper(II) with cyclopentanone thiosemicarbazone (CPTSC) is presented. The method is based on the adsorptive accumulation of the resulting copper-CPTSC complex on a hanging mercury drop electrode, followed by the stripping voltammetric measurements at the reduction current of the adsorbed complex at -0.37 V vs. Ag/AgCl. The optimal conditions for the stripping analysis of copper include pH 9.3, deposition time of 120 s, and a deposition potential of -0.1 V (vs. Ag/AgCl). The peak current is linearly proportional to the copper concentration over a range 3.14 x 10(-9) M to 1.57 x 10(-6) M with a limit of detection of 1.57 x 10(-9) M. The technique has been applied to the determination of copper in biological samples, like urine and whole blood.

Sampling conditions for biological fluids for trace elements monitoring in hospital patients: a critical approach

Lack of coherence in the results of trace element (TE) analyses produced by various laboratories has been such as to necessitate much needed technical improvements and more detailed control over sample preparations. For too long, except for a few praiseworthy researchers, the importance of sampling conditions has been underestimated as a source of erroneous TE results. Many of the precautionary procedures for previously studied TE collection materials have proven to be so cumbersome that they cannot be applied in a hospital setting. This report deals with sampling material and conditions from a workday standpoint; a rigorous description of the contaminating roles of ambient air and routine handling of specimens places emphasis on the practical. While some metals, including cobalt, copper, iron, and selenium, present no significant risk of contamination, others, such as aluminum, cadmium, chromium, manganese, and nickel, pose quite a significant risk. They warrant attention with respect not only to the sampling itself but also the selection of the material to be used. Drawing on our hospital experience, we propose a critical approach toward the collection of samples of biological fluids (blood, urine, dialysis fluids). Needles, catheters, tubes (open and evacuated systems), and anticoagulants on the market are likewise assessed in terms of their contaminative roles. For each one elementary rules as well as realistic choices of materials and methods for a hospital environment are proposed.

Zinc excretion in osteoporotic women

The relation of zinc to the aging skeleton was investigated in 140 women aged 36-85 years, mostly postmenopausal, who attended the Jerusalem Osteoporosis Center. Osteoporosis was determined by lumbar spine radiograms (Smith index). Bone density (BD) of the distal radius was assessed by Compton spectroscopy and bone mineral content (BMC) at the same site by single-photon absorptiometry. Urine samples (24 h) were analyzed for zinc (UZn), hydroxyproline (UHP), calcium (UCa), magnesium (UMg), and phosphorus (UP) and expressed per gram creatinine. Patients with definite osteoporosis (n = 94) compared to subjects with borderline or no osteoporosis (n = 34) had a significantly higher mean age (67.4 versus 58.6 years), postmenopausal age (PMA, 19.9 versus 11.0), UZn (811 versus 581), UHP (23.5 versus 18.2), and UMg (90.4 versus 74.3). Urinary calcium UCa and phosphorus UP were similar in both groups. The bone mass measurements BD, BMC, and CI were lower in the osteoporotic group. Hyperzincuria (UZn above 800 micrograms/g creatinine) was found in 41 osteoporotic patients (45%) compared to 6 subjects in the control group (17%). In view of the positive correlation between UZn and age (r = 0.35, p = 0.001) and to eliminate the effect of age, a separate analysis was performed for 66 subjects under the age of 65 in whom the mean age was similar for the osteoporosis patients (n = 38) and control group (n = 28). Nevertheless, the osteoporosis patients still had a significantly higher mean UZn and UHP.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical aspects of vitamin and trace element metabolism

An adequate provision of all micronutrients, vitamins and essential trace elements is necessary for maintenance of normal tissue function. In patients requiring nutritional support, these factors are essential for optimal utilization of the major nutrients and play a role in all aspects of intermediary metabolism. In this chapter, some of the main features of the micronutrients have been described, together with suggestions regarding their provision enterally or parenterally. For most of these nutrients, diagnostic methods are not available to permit accurate assessment of status and hence the level of provision necessary for optimal results. However, there is now sufficient understanding of nutritional requirements such that few patients should now develop clinical or biochemical signs of under- or overprovision of micronutrients.

Serum and urinary selenium levels in thermal injury

Information concerning selenium status in thermal injury patients is limited. Therefore, both serum selenium concentration and 24 h urinary excretion of selenium were evaluated throughout the hospital course for 23 patients with partial and full skin thickness thermal burns. Serum selenium levels were depressed throughout the hospital course in the majority of patients, and only two patients' serum selenium levels had reached the normal range by discharge. Urinary selenium losses were essentially within normal range throughout the same period and thus were not responsible for the observed depression in serum selenium levels. A possible antagonistic relationship between selenium and silver is discussed.

Clinical studies on zinc metabolism during total parenteral nutrition as related to zinc deficiency

In 99 adult patients receiving controlled total parenteral nutrition (TPN), a study was made on the time course of concentrations of zinc in plasma, erythrocyte and urine in relation to the development of zinc deficiency. Zinc deficiency developed in 11 cases receiving TPN solutions not containing zinc. The plasma zinc level was significantly lower at the time of onset of zinc deficiency than in normal subjects, before the procedure of TPN, or at the time of symptomatic relief achieved by administration of zinc. The erythrocyte zinc level was slightly but not significantly lower at time of onset of zinc deficiency than in normal subjects, before TPN or at time of symptomatic relief. The urinary zinc level at time of onset of zinc deficiency was significantly lower than that in normal subjects or at the time of symptomatic relief but not significantly lower than that before TPN. A comparison between patients developing and those not developing zinc deficiency within 4 wk of the outset of TPN showed that only the plasma zinc level was significantly lower in the former than the latter group. The urinary zinc level also tended to be lower, although not significantly, in the former than the latter group but varied widely. No difference was present between the groups as to the erythrocyte zinc level. Zinc deficiency developed in none of those patients who had a plasma zinc level of 50 micrograms/dl or more but in five of 10 (50%) patients with less than 50 micrograms/dl and in all three with less than 30 micrograms/dl of zinc in plasma.(ABSTRACT TRUNCATED AT 250 WORDS)

Determination of copper in urine by graphite furnace atomic absorption spectrometry

Two methods are described for the determination of copper in urine by graphite furnace atomic absorption spectrometry. The first, suitable for spectrometers capable of making good background correction at 325 nm, involves a direct determination against simple aqueous standards after 2 X dilution of the sample. The second requires no background correction and can be used when background correction is not available or is inadequate. The copper is extracted from the urine with ammonium tetramethylenedithiocarbamate into methylisobutylketone and the extract is analysed for copper. No significant matrix effect was observed for either method. Analysis of random urine samples from 16 normal subjects gave a mean concentration of 0.42 mumol/l with a range of 0.06--1.04 mumol/l.

[Evolution of serum copper and zinc levels in burn patients (author's transl)]

The study of copper and zinc in 35 patients, over periods of up to 21 days following thermal injury, is marked by an important and early fall in serum copper and zinc levels. The maximum intensity of the biological disturbance appears about two days after the injury. Reversion to near normal values coincides with recovery from the large part of the lesions. The comparison of the evolution of serum levels does not permit any definite relationship to be established between copper and zinc metabolism.