Magnesium therapy in premature neonates with apnea neonatorum

New Data on the Importance of Gestational Mg Deficiency

Chronic primary Mg deficiency is frequent. About 20% of the population consumes less than two-thirds of the RDA for Mg. Women, particularly, have low intakes. For example, in France, 23% of women and 18% of men have inadequate intakes. Mg deficiency during pregnancy can induce maternal, fetal, and pediatric consequences that might last throughout life. Studies of gestational Mg deficiency in animals show that Mg deficiency may have marked effects on parturition and postuterine involution. It has interfered with fetal growth and development, and caused morbidity from hematological effects and disturbances in temperature regulation, to teratogenic effects. Emphasis, here, is on effects of chronic clinical gestational Mg deficiency as it affects the infant. Premature labor, contributed to by uterine hyperexcitability caused by chronic maternal Mg deficiency, that can be intensified by stress, gives rise to preterm birth. If the only cause of uterine overactivity is Mg deficiency, its supplementation constitutes nontoxic tocolytic treatment, as an adjuvant treatment, that is devoid of toxicity and enhances efficacy and safety of tocolytic drugs such as beta-2 mimetics. Evidence is considered that Mg deficiency or Mg depletion can contribute to the Sudden Infant Death Syndrome (SIDS). SIDS may be a fetal consequence of maternal Mg deficiency through impaired control of Brown Adipose Tissue (BAT) thermoregulation mechanisms leading to a modified temperature set point. SIDS can result from dysthermias: hypo- or hyperthermic forms. Possibly, simple nutritional Mg supplements might be preventive. Various stresses in an infant can transform simple Mg deficiency into Mg depletion. For example, lying prone can be stressful for the baby, as can parental smoking. The role of chronopathological stress appears to be often neglected, as it constitutes a clinical form of primary hypofunction of the biological clock [with its anatomical and clinical stigma such as reduced production of melatonin (MT) and of its urinary metabolite: 6 Sulfatoxy-Melatonin (6 SMT)]. SIDS might be linked to impaired maturation of both the photoneuroendocrine system and BAT. Prophylaxis of this form of SIDS should include atoxic nutritional Mg therapy for pregnant women with total light deprivation at night for the infant. Consequences of maternal primary Mg deficiency have been inadequately studied. To determine ultimate outcomes of gestational Mg deficiency in infants, a long-term multicenter placebo-controlled prospective study should undertaken on effects of maternal nutritional Mg supplementation on lethality/morbidity in fetus, neonates, infants, children and adults, not only during pregnancy and the baby's first year, but throughout life.

Nutrient requirements for preterm infant formulas

Achieving appropriate growth and nutrient accretion of preterm and low birth weight (LBW) infants is often difficult during hospitalization because of metabolic and gastrointestinal immaturity and other complicating medical conditions. Advances in the care of preterm-LBW infants, including improved nutrition, have reduced mortality rates for these infants from 9.6 to 6.2% from 1983 to 1997. The Food and Drug Administration (FDA) has responsibility for ensuring the safety and nutritional quality of infant formulas based on current scientific knowledge. Consequently, under FDA contract, an ad hoc Expert Panel was convened by the Life Sciences Research Office of the American Society for Nutritional Sciences to make recommendations for the nutrient content of formulas for preterm-LBW infants based on current scientific knowledge and expert opinion. Recommendations were developed from different criteria than that used for recommendations for term infant formula. To ensure nutrient adequacy, the Panel considered intrauterine accretion rate, organ development, factorial estimates of requirements, nutrient interactions and supplemental feeding studies. Consideration was also given to long-term developmental outcome. Some recommendations were based on current use in domestic preterm formula. Included were recommendations for nutrients not required in formula for term infants such as lactose and arginine. Recommendations, examples, and sample calculations were based on a 1000 g preterm infant consuming 120 kcal/kg and 150 mL/d of an 810 kcal/L formula. A summary of recommendations for energy and 45 nutrient components of enteral formulas for preterm-LBW infants are presented. Recommendations for five nutrient:nutrient ratios are also presented. In addition, critical areas for future research on the nutritional requirements specific for preterm-LBW infants are identified.

Consequences of magnesium deficiency on the enhancement of stress reactions; preventive and therapeutic implications (a review)

Stress intensifies release of catecholamines and corticosteroids that increase survival of normal animals when their lives are threatened. When magnesium (Mg) deficiency exists, stress paradoxically increases risk of cardiovascular damage including hypertension, cerebrovascular and coronary constriction and occlusion, arrhythmias and sudden cardiac death (SCD). In affluent societies, severe dietary Mg deficiency is uncommon, but dietary imbalances such as high intakes of fat and/or calcium (Ca) can intensify Mg inadequacy, especially under conditions of stress. Adrenergic stimulation of lipolysis can intensify its deficiency by complexing Mg with liberated fatty acids (FA), A low Mg/Ca ratio increases release of catecholamines, which lowers tissue (i.e. myocardial) Mg levels. It also favors excess release or formation of factors (derived both from FA metabolism and the endothelium), that are vasoconstrictive and platelet aggregating; a high Ca/Mg ratio also directly favors blood coagulation, which is also favored by excess fat and its mobilization during adrenergic lipolysis. Auto-oxidation of catecholamines yields free radicals, which explains the enhancement of the protective effect of Mg by anti-oxidant nutrients against cardiac damage caused by beta-catecholamines. Thus, stress, whether physical (i.e. exertion, heat, cold, trauma--accidental or surgical, burns), or emotional (i.e. pain, anxiety, excitement or depression) and dyspnea as in asthma increases need for Mg. Genetic differences in Mg utilization may account for differences in vulnerability to Mg deficiency and differences in body responses to stress.

Role of magnesium in regulation of lung function

Magnesium and calcium play multiple dynamic roles in pulmonary structure and function. When magnesium is deficient, the action of calcium is enhanced. In contrast, an excess of magnesium blocks calcium. These interactions are important to the respiratory patient because the intracellular influx of calcium causes bronchial smooth-muscle contraction. The possibility exists that magnesium deficiency contributes to pulmonary complications. During the past few years, there has been an increase in calcium consumption in the US population but little change in magnesium intake, which has caused an imbalance in the calcium:magnesium ratio. Although serum levels are used to assess magnesium deficiency, cells can be deficient despite normal serum values. These findings indicate that pulmonary patients should be monitored routinely for magnesium deficiency.

Effects of hypomagnesemia on reactivity of bovine and ovine platelets: possible relevance to infantile apnea and sudden infant death syndrome

Blood platelet function and possible involvement in death of hypomagnesemic ruminants was investigated with 26 Angus cows, 15 mature Hampshire wethers, eight Finnish-Hampshire ewes, and 36 growing Dorset lambs. Hypomagnesemia was induced by feeding vegetative spring tall fescue to 13 cows and semipurified diets low in Mg to nine wethers, four ewes, and 18 lambs. In comparison with controls, dietary treatments reduced plasma Mg concentrations 55% in cows, 36% in wethers, 66% in ewes, and 78% in lambs. Hypomagnesemia reduced in vitro reactivity of cow and lamb platelets to thrombin, ADP, and platelet active collagen, but in vitro tests may not accurately reflect in vivo platelet reactivity. Microscopic examination of platelet-rich plasma revealed a threefold increase in clumped platelets from four hypomagnesemic ewes compared to four normomagnesemic ewes. This suggests that in vivo activation and exhaustion of platelets may have contributed to reduced in vitro platelet reactivity. Six of 18 hypomagnesemic lambs died spontaneously in tetany after 2-12 months on low-Mg diets. Heart and lung lesions were markedly similar to pathological changes induced in other lambs by intravascular activation of platelets with 500 micrograms of vascular collagen fibrils per kg body weight injected intravenously. These results suggest the possibility of abnormal blood platelet activation as a significant mortality risk factor in severe hypomagnesemia.