Parenteral magnesium load evaluation of malnourished Thai children

Magnesium deficiency. Etiology and clinical spectrum

Magnesium deficiency may complicate many diseases. The causes include the following: inadequate intake during starvation or increased requirement during early childhood, pregnancy, or lactation; excessive losses of magnesium as a result of malabsorption from the gastrointestinal tract or from the kidneys during use of diuretics; and to a combination of the two, as in alcoholism. Most often the etiological factors have been operative for a month or more. Acute hypomagnesemia can occur without previous Mg deficiency after epinephrine, cold stress and stress of serious injury or extensive surgery. The clinical manifestations depend on the age of the patient and may begin insidiously or with dramatic suddenness, or there may be no overt symptoms or signs. The manifestations can be divided into the following categories: totally non-specific symptoms and signs ascribable to the primary disease; neuromuscular hyperactivity including tremor, myoclonic jerks, convulsions, Chvostek sign, Trousseau sign (rarely), spontaneous carpopedal spasm (rarely), ataxia, nystagmus and dysphagia; psychiatric disturbances from apathy and coma to some of all facets of delirium; cardiac arrhythmias including ventricular fibrillation and sudden death; hypocalcemia which is responsive only to Mg therapy; and hypokalemia which is not easily nor completely corrected without Mg therapy. The diversity of etiologies and the multiplicity of manifestations result in confusion and controversy. The documentation of normal renal function is absolutely necessary for maximum doses. The order of magnitude of dose is 1.0 meq Mg/kg on day 1, and 0.3 to 0.5 mEq/kg per day for 3 to 5 days. In emergencies such as convulsions or ventricular arrhythmias, a bolus injection of 1.0 gm (8.1 meq) of MgSO4 is indicated. Therapy of Mg deficiency in the presence of renal insufficiency requires smaller doses and frequent monitoring. Complete repletion occurs slowly.

Management of severe malnutrition and diarrhea

Children with severe malnutrition and diarrhea have high mortality rates that have been attributed to faulty case-management. Health workers are often unaware of the unique treatment requirements of severely malnourished children resulting in improper case-management. Moreover, the lack of prescriptive guidelines promotes the exercise of discretion in case-management that is often detrimental. Appropriate feeding from the start of treatment, routine micronutrient supplementation, broad-spectrum antibiotic therapy, less use of intravenous fluids for rehydration, and careful management of complications are factors that can reduce death, morbidity and cost of treating children with severe malnutrition and acute illnesses including diarrhea. In this paper is discussed a standardized protocol based upon the above mentioned factors for the management of severely malnourished children with acute illnesses including diarrhea. Implementation of the protocol resulted in a 47% reduction in mortality in these children.

Hypomagnesemic disorders

Adequate magnesium stores are vitally important for life. Critically ill patients will almost always have diminished levels of circulating magnesium, and this predisposes them to a variety of adverse effects, some life threatening. The causes of hypomagnesemia are many and varied, but in the critically ill, losses from the kidneys, often secondary to medications and from the gastrointestinal (GI) tract, predominate. The measurement of magnesium is not straightforward, although many clinicians are now switching to the use of ionized magnesium from ion selective electrodes. The use of supplemental magnesium in acute flares of asthma has some support in medical literature, especially for those patients with severe disease who fail traditional therapy. Magnesium holds the preeminent position in the treatment of pre-eclampsia and eclampsia in the minds of most obstetricians, who have decades of experience showing it to be both effective and safe. Magnesium is clearly useful for certain types of ventricular tachycardia, and probably assists in the treatment of several types of supraventricular tachycardia. Its role in acute myocardial ischemia is less certain, although there is no benefit once reperfusion therapy has already been carried out. Finally, the role of magnesium in the treatment of acute cerebral insults is an exciting area of active investigation with initial studies suggesting much promise.

The magnesium loading test: reference values in healthy subjects

The magnesium loading test is a useful tool in the diagnosis of magnesium deficiency. In order to establish a reference range in normal subjects, 88 healthy men and women aged between 18 and 66 years were given 30 mmol magnesium intravenously during eight hours as a loading test, urine was collected from start of infusion for 24 h for measurement of magnesium excretion. The magnesium mean retention was 6.3 +/- 10.3% of the loading dose, and the 0.025 and 0.975 fractiles were -19.5% and 27.5%, respectively. There was no significant difference between the sexes or in the different age groups studied. There was no correlation between the magnesium retention and serum magnesium or with basal urinary magnesium excretion. An excess excretion of magnesium was observed the postload day compared to baseline, but the excretion 24 and 48 h after the magnesium loading were closely correlated, suggesting that 24 h urinary sampling is sufficient. In order to examine the reproducibility of the test 23 of the subjects underwent two magnesium loading tests 4 weeks apart. The mean difference between two repeat magnesium loading tests was 2.0% with a SD of 8.1% and a 95% confidence interval of -1.6-5.5%. Normal saline did not affect baseline magnesium excretion. Concomitant administration of ethanol or physical exercise caused greater variation in magnesium excretion, whereas furosemide was without effect. The 8 h magnesium loading test with 24 h urine sampling seems to be fairly reproducible, is adequate for clinical use, but the normal range is wide.

Magnesium status in healthy free-living elderly Norwegians

OBJECTIVE

Magnesium (Mg) status has previously not been properly assessed among healthy elderly subjects.

METHODS

Thirty-six healthy elderly subjects participated. Their Mg status was assessed by serum Mg, basal urinary Mg output, and with a Mg loading test (30 mmol infused during 8 hours; urine sampled 24 hours), and compared with 53 healthy younger subjects. Their dietary intake was assessed by a quantified food frequency questionnaire. Fourteen of the subjects received 300 mmol Mg to study the effect on Mg status.

RESULTS

With the exception of vitamin D in women, average energy and nutrient intakes were adequate. All subjects had serum Mg levels within the reference value of the laboratory. Basal urinary Mg excretion was 3.3 +/- 1.1 mmol/day and 24-hour Mg retention after a Mg load was 28 +/- 16% compared to 6 +/- 11% in younger controls, suggesting Mg deficiency in the elderly. In the 14 subjects who received oral Mg supplementation there was a statistically significant increase in basal urinary Mg excretion and creatinine clearance, and decreases in Mg retention, serum Mg and serum creatinine.

CONCLUSIONS

This study suggests that a significant subclinical Mg deficit, not detected by serum Mg, was present in many of these healthy elderly subjects. Mg supplementation improved Mg status and renal function.

Magnesium deficiency diagnosed by an intravenous loading test

Magnesium deficiency is common but difficult to diagnose and to assess in clinical practice. The use of a magnesium loading test was therefore evaluated to diagnose magnesium deficiency in 661 hospitalized patients with medical conditions assumed to interfere with magnesium uptake and excretion. Thirty millimoles of magnesium sulphate were administered intravenously during 8 h as a loading test and related to the urinary excretion in the following 24 h. A group of 30 patients without any known predisposition for magnesium deficiency and a group of 27 healthy volunteers served as controls. The mean (with 95% confidence interval) magnesium retention was 4 (-2-10)% in the control group of patients and 3 (-2-8)% in healthy subjects. A significantly higher retention was observed in all the groups of the patients: atrial fibrillation 18 (11-25)%, other arrhythmias 18 (11-24)%, hypertension 27 (20-33)%, coronary artery disease 25 (20-30)%, congestive heart failure 31 (26-37)%, cerebrovascular events 38 (24-51)%, gastrointestinal disorders 22 (14-29)%, diabetes mellitus 16 (9-22)%, and alcoholics 33 (29-36)%. The percentage of patients with a retention greater than mean + 2 SD of the two control groups varied between 22% and 54% among the different patient groups. The mean serum magnesium among the patient groups was similar to the control group of patients, except for the alcoholics, hypertensives and young healthy controls, who had significantly reduced levels. Magnesium retention was significantly correlated to age and renal function, and among the alcoholics negatively correlated to serum magnesium.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of magnesium status in Crohn's disease as assessed by intracellular analysis and intravenous magnesium infusion

The magnesium status was evaluated in 30 subjects with Crohn's disease and in 30 controls. Subjects with Crohn's disease had lower concentrations of magnesium in muscle biopsy specimens (p less than 0.001), mononuclear cells (p less than 0.05), and in urine collected during 24 h (p less than 0.001) as compared with controls. After intravenous infusion of 60 mmol magnesium and 80 mmol potassium to 17 subjects with Crohn's disease a significant increase in concentrations of magnesium in muscle specimens (p less than 0.05), mononuclear cells (p less than 0.01), and plasma (p less than 0.01) was noted. The retention of intravenously infused magnesium was significantly higher in subjects with Crohn's disease than in 11 healthy controls (p less than 0.001) and was inversely correlated with the content of magnesium in muscle specimens (r = -0.52; p less than 0.05). The implication of these findings is that analysis of magnesium in muscle specimens and estimation of magnesium retention during an intravenous magnesium infusion are useful to confirm a suspected magnesium deficiency.

Jejunoileal bypass and electrolytes. A follow-up study of intra- and extra-cellular electrolytes with special emphasis on magnesium

It is generally believed that patients operated on for gross obesity with jejunoileal shunt develop electrolyte malabsorption. In follow-up studies electrolyte abnormalities have been reported in 6-37% of the cases. We have not been able to find any description of simple diagnostic tools to help indicate which patients should be treated with electrolyte supplements. The aim of this study was to evaluate different diagnostic tools to determine whether they would identify which patients to treat. Ten patients with end-to-side jejunoileostomies were investigated. Our attempt failed. We were not able to identify the patients who needed supplementary therapy. The reason for this may be absence of severe electrolyte abnormalities or insufficient diagnostic methods.

Magnesium status in children with insulin-dependent diabetes mellitus

We assessed the magnesium status in 67 children with insulin-dependent diabetes mellitus (IDDM) in various degrees of diabetic control and its changes during the evolution of the disease. This was done by measuring fasting serum magnesium and 24-hr urinary magnesium clearances when patients were first studied, as well as subsequently on follow-up. In 23 of these patients the retention of intramuscular magnesium was also assessed in relation to the degree of diabetic control and the duration of the illness. The mean +/- SD serum magnesium levels were significantly lower in diabetic children as compared to nondiabetic controls (1.91 +/- 0.22 vs 2.12 +/- 0.26 mg/dl, p less than 0.001). Serum magnesium in diabetic children correlated with glycosylated hemoglobins (r = -0.358, p less than 0.001), but not with 24-hr glycosuria (r = -0.296). On follow-up of patients, serum magnesium significantly increased when IDDM control improved and decreased when the control worsened. Diabetic patients had increased urinary magnesium clearances compared to nondiabetic subjects (5.26 +/- 3.58 vs 3.60 +/- 1.36 cc/min, p less than 0.05). All but five of the 23 patients given the magnesium load retained more than 40% of the dose, with a mean +/- SD retention of 58.7 +/- 5.1%. There was no correlation between the amount of retained magnesium and the duration of the illness, degree of diabetic control, amount of glycosuria, magnesuria, magnesemia, glycosylated hemoglobins, or serum lipids. The data confirm that lower than control serum magnesium levels occur frequently among children with poorly controlled IDDM. Moreover, there might be magnesium deficiency in IDDM, as indicated by the high retention of magnesium when given intramuscularly. The deficiency of this ion may or may not be accompanied by decreased serum magnesium levels and may result from increased urinary magnesium losses in children with IDDM.