Journal of Postgraduate Medicine Medknow Publications and Staff Society of Seth GS Medical College and KEM Hospital, Mumbai, India ISSN: 0022-3859 EISSN: 0972-2823 Vol. 46, Num. 3, 2000, pp. 179-180

Journal of Postgraduate Medicine, Vol. 46, No. 3, July-September, 2000, pp. 179-180

Brief Report

Hypomagnesaemia in Paediatric Population in an Intensive Care Unit

Deshmukh CT, Rane SA*, Gurav MN

Departments of Paediatrics and Biochemistry*, Seth G. S. Medical college and K. E. M. Hospital, Parel, Mumbai- 400 012.
Address for correspondence: C. T. Deshmukh, MD, Department of Paediatrics, Seth G. S. Medical College and K. E. M. Hospital, Parel, Mumbai - 400 012, India.

Code Number: jp00064

Abstract

AIMS: To determine incidence and risk factors for hypomagnesaemia in children admitted in Paediatric Intensive Care Unit, (PICU). SUBJECTS AND METHODS: Prospective study was carried out on 80 children admitted in PICU. The patients were patients were clinically assessed for nutritional status, neurological status on Glasgow coma scale, congestive cardiac failure, etc. and relevant biochemical parameters including serum and red cell magnesium levels were done. 25 patients of the same age group admitted in general ward who were not in critical state were included as a control group. RESULTS: 70% of PICU patients had hypomagnesaemia, which was more common in paitents on aminoglycosides and diuretics. CONCLUSION: In view of complications of magnesium depletion and benign nature of appropriate magnesium therapy critically ill children should have their magnesium level monitored. (J Postgrad Med 2000; 46:179-180)

Key words: Serum and RBC magnesium, Hypomagnesaemia, critically ill children, diuretic therapy.

Magnesium is second most common cation necessary in large number of metabolic processes including oxidative phosphorylation, enzymatic reactions, nucleic acid metabolism, protein synthesis and others.^1,2 Because of its importance in metabolism, deficiency of magnesium can have consequences such as neuromuscular irritability, tetany, refractory seizures, ECG changes and refractory hypokalaemia.^1-3 Hypomagne-saemia is observed in conditions like malabsorption syndrome, primary hyperaldosteronism, primary hyperthyroidism and in association with long term therapy of diuretics and aminoglycosides.^3-6 This study was performed to investigate the prevalence of serum and RBC magnesium derangements in paediatric intensive care unit (PICU) and to determine if any biochemical and clinical correlates of hypomagnesaemia existed.

Subjects and Methods

The study was conducted over period of 8 months during which 80 patients between 29 days to 12 years age groups in critically ill non-surgical conditions and not on calcium and magnesium therapy were selected. Permission for the study was taken from local hospital ethics committee. The patients were clinically assessed by the PICU team and biochemical parameters like serum calcium, phosphorus, alkaline phosphatase, electrolytes, renal and liver function tests were done. Twenty five patients of the same age group admitted in general ward who were not in critical state were included in the study to serve as a control group.

Serum and read blood cell (RBC) magnesium levels were estimated by titan yellow method.^7,8 Serum magnesium levels were expressed as milligram per decilitre while RBC magnesium was expressed as magnesium in 100 ml of packed RBCs. The values considered for hypomagnesaemia were 1.4 mg/dl for serum and 2.8 mg/100cc of packed RBCs for RBC magensium.

Hypomagnesaemia was evaluated in various clinical groups like protein energy malnutrition, altered sensorium expressed in Glasgow coma scale, cardiac arrhythmias, congestive cardiac failure, duration of PICU stay, diuretic and aminoglycoside therapy.

The Z value difference between mean values of serum and RBC magnesium in patient and control group were estimated by standard error of difference of mean p value <0. 001 was considered statistically significant.

Results

Out of 80 patients, 47 were male and 33 female with mean age of 3.5 years. The range of duration of stay in PICU was 1 to 42 days respectively (mean 4.5 days). The number of patients belonged to protein energy malnutrition grade I, II, III and IV were 35, 36, 7 and 2 respectively.

Serum and RBC magnesium levels were significantly lowered in PICU patients as compared to control group; p<0.001, (Table-1). 55 out of 80 patients in the PICU group had hypomagnesaemia, compared to only three out of 25 children in the control group.

Table 2

Hypomagnesaemia was documented in six out of nine patients with Glasgow coma scale below three (60%), six out of eleven patients with score between four and seven (58%), 35 out of 60 patients with score above seven (60%). All children with control group had score above seven and only three had hypomagnesemia (12%). Thirty two out of 54 patients in PICU with duration of stay in PICU more than 72 hours had hypomagnesaemia (64. 8%). Nine out of 18 patients in PICU with duration of stay between 24 to 72 hours had hypomagnesaemia(50%). Three out of eight patients with duration of PICU stay less than 24 hours had hypomagnesaemia.

Twenty eight out of 80 patients in PICU had died out of which 15 patients had hypomagnesaemia (53.5%).

Discussion

Previous studies have showed high prevalence of hypomagnesaemia in severely ill patients.^2,9 A wide spectrum of conditions predisposing to magnesium depletion, are frequently present in patients admitted in PICU.

In the present study 55 out of 80 patients had hypomagnesaemia i.e. 70% of all critically ill children admitted in PICU. When compared with control group it was statistically significant. Previous studies in critical care units mostly conducted in adult patients have shown prevalence of hypomagnesaemia from 9.4% to 50%. There are various factors apart from nutrition which play part in hypomagnesaemia in PICU patients viz. aminoglycoside and diuretic use, gastrointestinal losses, withholding feeds and prior nutritional status.^4-6,9

The lowest value of magnesium (serum, 1.1 mg/dl;RBC, 2. 7 mg/100 cc of packed RBCs) were found in PICU patients with aminoglycoside and diuretic therapy. Similar results were documented in adult patients.^4-6

It was also found that incident of hypomagnesaemia went on increasing in direct proportion to duration of PICU stay, 24 hours - 37.5%, 24 to 48 hours - 50% and 48 to 72 hours-64.8%.

Most of the studies done in the past were in adult. Lim et al had shown hypomagnesaemia in nearly 50% of all patients on diuretics. Zaloga et al showed that aminoglycoside therapy for an average of 7 days or more produced hypomagnesemia in 40% of patients compared to our study in which 57.6 % had hypomagnesaemia.⁶

The incidence of hypomagnesemia in PICU was more in patients with convulsions, in patients with severe grades of altered sensorium, metabolic acidosis or hypokalaemia.

In view of high incidence of hypomagnesaemia with its clinical and biochemical correlates in PICU patients and simple nature of magnesium estimation, the study recommends screening for hypomagnesaemia in at least selective high risk groups if not all PICU patients.

References

1. Lister George, Fontan JP. Paediatric critical Care. In: Nelson WE,Kliegman RM, Arvin AM. editors. Textbook of Paediatrics. 15th Ed. Pennsylvania: Saunders Company; 1996, pp 239-290.
2. Paschall JA, Melvin Tyrone. Fluid and electrolyte therapy. In: Holbrook PR, editor. Textbook of Paediatric Critical Care. 2nd Ed. Pennsylvania: Saunders Company; 1993, pp 653-702.
3. Seller RH, Cangiano J, Kim KE, Mendelssohn S, Brest AN, Swartz C. Digitalistoxicity and hypomagnesemia. Am Heart J 1970; 79, 57-68.
4. Sheehan J, White A. Diuretic associated hypomagnesemia. Br Med J (Clin Res Ed) 1982; 285: 1157-1159.
5. Lim P, Jacob E. Magnesium deficiency in patients on long-term diuretic therapy for heart failure. Br Med J 1972;3:620-622.
6. Zaloga GP, Chernow B, Pock A, Wood B, Zaritsky A, Zucker A.. Hypomagnesaemia as a common complication of aminoglycoside therapy. Surg Gynecol Obstet 1984;158;561-565.
7. Spare PD. Determination of serum magnesium by titan yellow method. Am J Clin Pathol 1962; 37; 232-236.
8. Evan A. On determination of magnesium in serum and urine by titan yellow method. Scand J Clin Lab Invest 1957;9:138-142.
9. Ryzen E. Wagers PW, Singer FR, Rude RK. Magnesium deficiency in medical ICU population. Crit Care Med 1985;13:19-21.

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