Effect of single dose magnesium on arrhythmias in patients undergoing coronary artery bypass surgery. 
To evaluate the safety and role of prophylactic administration of magnesium in preventing arrhythmias.  This double blind randomized placebo controlled clinical trial was conducted at Aga Khan University Hospital on coronary artery bypass surgery patients.  All patients were connected to holter monitor before induction of anaesthesia and this monitoring continued for 24 hours.  Study drug containing either 2-grams of magnesium or normal saline was given after intubation.  Levels of serum magnesium was checked preoperatively and then in ICU at 0, 6, 12, and 24 hours.  Independent t-test and chi square test were used for analysis.  Statistical significance was defined as p-value < 0.05.  A total of 104 patients consented to participate in the study, 53 patients were randomly allocated in magnesium (Mg) group and 51 in placebo group.  Two (3.77%) patients in magnesium group and five patients (9.8%) in placebo group developed atrial fibrillation.  Incidence of ventricular and supraventricular tachycardia was also slightly higher in placebo.  Mg level after arrival in CICU (Cardiac Intensive Care Unit) showed mean of 2.1 in magnesium group and 1.6 in placebo group (p = 0.6).  Low magnesium levels were noticed in the placebo group after cardiopulmonary bypass and although prophylactic administration of magnesium sulphate was relatively safe but significant benefit on prevention of arrhythmias could not be attained.