Total parenteral nutrition (TPN) as a cause of depletion of trace metal ions. Computer-based interpretation and treatment

Micronutrient Alterations During Continuous Renal Replacement Therapy in Critically Ill Adults: A Retrospective Study

BACKGROUND

Continuous renal replacement therapy (CRRT) is commonly used to provide renal replacement therapy in the intensive care unit. Limited published data suggest that CRRT may lead to depletion of water-soluble vitamins and trace elements. The goal of this study was to identify the incidence of trace element and vitamin deficiencies in critically ill patients during CRRT.

MATERIALS AND METHODS

This study is based on a retrospective chart review of patients who were referred to Emory University Hospital's nutrition support services and had at least 1 serum micronutrient level measured during CRRT (thiamin, pyridoxine, ascorbic acid, folate, zinc, and copper) between April 1, 2009, and June 1, 2012.

RESULTS

Seventy-five patients were included in the study. Nine of 56 patients (16%) had below-normal whole blood thiamin concentrations, and 38 of 57 patients (67%) had below-normal serum pyridoxine levels. Serum ascorbic acid and folate deficiencies were identified among 87% (13 of 15) and 33% (3 of 9) of the study patients, respectively. Nine of 24 patients had zinc deficiency (38%), and 41 of 68 patients had copper deficiency (60%). Of the 75 total subjects, 60 patients (80%) had below-normal levels of at least 1 of the micronutrients measured.

CONCLUSIONS

The incidence of various micronutrient deficiencies in critically ill patients who required CRRT was higher than previously reported. Prospective studies are needed to determine the impact of CRRT on micronutrient status and the potential clinical and metabolic efficacy of supplementation in the intensive care unit setting.

Metal ion-tetracycline interactions in biological fluids. Part 5. Formation of zinc complexes with tetracycline and some of its derivatives and assessment of their biological significance

A series of studies was previously devoted to the dependence of the bioavailability of various tetracyclines on their coordination with calcium and magnesium ions. Several clinical investigations have also shown zinc to interfere with the gastrointestinal absorption of the drug in humans. On the other hand, the administration of tetracycline to rats was reported to result in the increase of the elimination rate of zinc, which could originate in zinc-tetracycline interactions in blood plasma. Formation constants for zinc complexes with tetracycline, oxytetracycline, doxycycline, minocycline, chlortetracycline and demethylchlortetracycline were thus determined at 37 degrees C in NaCl 0.15 mol. dm-3 aqueous medium. Computer simulations were then carried out to investigate the drug influence on the distribution of the low-molecular-weight fraction of zinc in human blood plasma. Zinc-tetracycline interactions in the gastrointestinal fluid were also simulated, using clinical data relative to fasting subjects as taken from the literature. No significant effect can be expected from tetracyclines on the distribution of zinc in plasma at the usual therapeutic levels. However, zinc-tetracycline interactions have been found to be determining factors for the bioavailabilities of the metal as well as of the antibiotic in the gastrointestinal fluid.