Serum magnesium in critically ill cardiac patients: prevalence and prognostic implications

ABSTRACT

Serum levels of magnesium [Mg] and potassium [K] have been measured in 100 critically ill cardiac patients [pts] consecutively admitted to the Critical Care Center of Cairo University including 70 males, 30 females whose ages ranged from 25 to 78 [mean 52 years]. Diagnoses included acute myocardial infarction [AMI] in 50 pts, and miscellaneous cardiac disorders [without infarction] in the other 50 pts. Serum electrolytes [Mg and K] were measured daily on admission, whenever possible and at times of crises. The prevalence of hypomagnesemia in the two groups of patients was 56%, and that of hypokalemia was 34%. The incidence of ventricular arrhythmias in normomagnesemic AMI pts was 18.2% compared with 39.2% in hypomagnesemic pts with AIMI, with p-value 0.05 and 2.15 relative risk. There was a 41.1% incidence of ventricular arrhythmias with hypokalemia in AMI pts against 22.6% of the normokaliemic AMI pts, with p-value 0.07 and 1.86 relative risk. The AMI pts have a significantly higher incidence of ventricular arrhythmias in the patients with both Mg and K deficiencies [53.9%], than pts with single electrolyte deficiency [23.8%] or without electrolyte abnormalities [18.8%], p= 0.02. On the other hand, in the other cardiac disease, there was no significant difference between pts with arrhythmias and those without, in terms of hypo Mg and K. The mortality rate, however, of any group of pts showed no significant deviations when each electrolyte was analyzed separately