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Potassium levels critical in heart surgery

IHN logoIt is well-established that heart attack patients with low blood levels of potassium are more prone to develop serious (ventricular) arrhythmias than are patients with normal levels. A major study just released by a group of researchers from 24 American medical centers concludes that preoperative potassium levels are also of great importance in predicting the severity of complications in bypass surgery. The study involved 2402 patients (24 per cent female) who underwent elective coronary artery bypass grafting in a two-year period from September 1991 to September 1993. More than half (53.7 per cent) of the patients developed some form of arrhythmia either during or after surgery. The mortality rate (from any cause) during the hospital stay was 3.6 per cent and 3.5 per cent of the patients needed CPR (cardiopulmonary resuscitation) in order to survive the surgery. All patients had their blood (serum) levels of potassium checked prior to surgery. The researchers found that patients with potassium levels below 3.5 mmol/L were 2.2 times more likely to suffer a serious arrhythmia during or after their operation (perioperative) than were patients with normal levels. They also noticed that patients with low potassium levels tended to be female, users of diuretics, and have a history of arrhythmias and hypertension. High potassium levels, on the other hand, were associated with a history of congestive heart failure, age, and a history of renal disease. The researchers also found a weak correlation between low potassium levels and an increased risk of death during or after surgery. They conclude that adjusting abnormal potassium levels prior to heart surgery could significantly improve the outcome for the 500,000 or so patients undergoing cardiac surgery in the United States each year.
Wahr, Joyce A., et al. Preoperative serum potassium levels and perioperative outcomes in cardiac surgery patients. Journal of the American Medical Association, Vol. 281, June 16, 1999, pp. 2203-10

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