Hypomagnesemia in ICU.

M a key mineral, is the second most abundant intracellular cation. It is a cofactor of various enzymes, is essential for maintenance of membrane potentials and modification of vascular tone.1It helps to maintain normal nerve and muscle function and supports a healthy immune system. The tota l magnes ium content in humans is 25 mEq (12.4 mmol) per kilogram of body weight. The normal serum magnesium level ranges from 1.5 to 2.3 mg/dl (0.62 – 0.95 mmol/L).2 The importance of magnesium is being increasingly recognized. A number of studies, especially related to critical care, have shown high prevalence of low magnesium levels and have linked the same with poor outcome. Hypomagnesemia may present with neuromuscular, n e u r o l o g i c , p s y c h i a t r i c a n d cardiac manifestat ions, which may considerably increase the morbidity of such patients. The etiology of magnesium deficiency in ICU is multifactorial. Drugs ( d i u r e t i c s , a m i n o g l y c o s i d e s ) , renal and gastrointestinal losses, c o m o r b i d i t i e s l i k e d i a b e t e s mellitus and chronic alcoholism, metabolic disorders like Barter’s and Gittleman’s syndromes and magnesium redistribution are the postulated causes.3 T h e u s e o f I V m a g n e s i u m in cardiovascular therapy was explored way back in 1990’s. The results of Leicester Intravenous Magnesium Intervention Trial (LIMIT-2)4 and a meta-analysis of seven smaller trials5 depicted a reduct ion in mortal i ty with a decreased incidence of heart failure and arrhythmias in acute myocardial infarction. In this issue of the journal, B. Sheba Charles et al6 determined t h e m a g n e s i u m l e v e l s i n 5 0 healthy subjects and 96 critically ill study patients. They infused IV magnesium as a therapeutic intervent ion in 23 pat ients of h y p o m a g n e s e m i a ( s e r u m magnes ium ≤1 .7 mg/dL) . The o u t c o m e p a r a m e t e r s n a m e l y duration of ICU stay, need and duration of mechanical ventilation and overall ICU mortality were compared with a control group of 96 patients satisfying the inclusionexclusion criteria, admitted serially in the same ICU prior to the study. In this study the mean serum magnesium in a sample of healthy I n d i a n p o p u l a t i o n wa s 2 . 1 1 2 mg/dL (range 1.8-2.6 mg/dL) by using colorimetric method with Xylidyl blue. This was found to be marginally higher than the western data.2 31.7% of diabetics and 43.7% of alcoholics had hypomagnesemia.