ANN ARBOR, Mich.-- A new study shows that patients undergoing cardiac surgery were twice as likely to experience certain complications when their pre-surgical potassium levels were below accepted standards. The study is published in the June 16, 1999, issue of The Journal of the American Medical Association.
A group of researchers from leading medical institutions in the United States examined the potassium levels of more than 2,400 patients undergoing cardiac surgery. They found that arrhythmias, including atrial fibrillation, during and after surgery doubled when a patient's serum potassium level fell below 3.5 millimoles per liter (mmol/L). At levels below 3.3 mmol/L, the need for cardiopulmonary resuscitation (CPR) also doubled.
Investigators concluded that screening and replenishing a patient's serum potassium is a low-risk, low-cost intervention that should be considered on a case by case basis for all cardiac surgery cases.
"We hope these results will change the impression that mild decreases in potassium are within normal limits," says Joyce Wahr, M.D., principal investigator and associate professor of anesthesiology in the University of Michigan Health System. "There is a consequence and we should have a heightened awareness that it could be harmful to patients with heart disease."
The large, multi-center study is the first to identify a specific low potassium level prior to surgery that is significantly associated with perioperative arrhythmias---arrhythmias during and after cardiac surgery---and to validate an association between low serum potassium levels and the risk of adverse outcomes in cardiac patients.
Potassium is essential to maintaining a normal heart rhythm, and is responsible
for the conduction of nerve impulses and muscle contraction. The ratio of
potassium outside the cell to that inside the cell maintains polarity, allowing
an electrical charge to conduct along a row of cells, causing the heart to beat.
Contact: Peter Barkey
University of Michigan