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CHARLESTON, SOUTH CAROLINA. Administration of magnesium has been
shown to reduce the incidence of heart surgery related arrhythmias
in adults. It has also been observed that the magnesium level in
the right atrial tissue is lower in adult patients with
postoperative cardiac arrhythmias compared to patients without
arrhythmias after heart surgery. Researchers at the Department of
Pediatric Cardiology at the Medical University of South Carolina
now report that children undergoing surgery for congenital heart
defects develop a severe magnesium deficiency immediately after
surgery. This deficiency is associated with a greater incidence
of a serious arrhythmia (junctional ectopic tachycardia) and can
be prevented by an infusion of magnesium sulfate immediately after
completion of the surgery. The study involved 28 pediatric patients (average age of five years) who were scheduled to undergo heart surgery with cardiopulmonary bypass (CPB). The patients were randomly assigned to receive an infusion of magnesium (30 mg/kg body weight of a five per cent saline solution administered over a period of 10 minutes) or an infusion of saline solution immediately after cessation of CPB. Blood levels of magnesium were measured in all patients before surgery, before CPB, after CPB, upon arrival in the intensive care unit (ICU), and then every four hours for 24 hours. Each patient was also monitored for arrhythmias for 24 hours with a Holter monitor.
Comparison of the results for the two treatment groups revealed
that the magnesium level was significantly below normal in
patients who had received saline solution (placebo) when they
arrived in the ICU and for the following 20 hours. Patients who
had received the magnesium infusion, on the other hand, had
magnesium levels that were well within the normal range (1.6 to
2.3 mg/dL) when tested in the ICU and for the following 20 hours.
There were no incidences of junctional ectopic tachycardia in the
magnesium group, but four (27 per cent) of the patients in the
placebo group experienced this serious arrhythmia. It stopped
after a magnesium infusion. The researchers "recommend routine
measurement of magnesium levels after CPB in children undergoing
heart surgery, with timely magnesium supplementation in the
postoperative period." [49 references]
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