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3 Is hypokalaemia during acute exacerbations of heart failure predictable or preventable?
  1. D O'Hare,
  2. C O'Connor,
  3. Z Coyne,
  4. G Balan,
  5. C Mac Sweeney,
  6. K Tuite,
  7. R Murphy,
  8. C Daly
  1. St. James's Hospital, Dublin, Ireland


Introduction Heart failure activates the renin-angiotensin aldosterone system, which leads to hypokalaemia. This is aggravated by upregulated sympathetic drive and the use of increased amounts non-potassium sparing diuretics during acute exacerbations. Mild hypokalaemia has been shown to increase cardiovascular events in a treated heart failure population. In patients with NYHA class I to III patients, elevations of serum potassium have been shown to reduce the incidence of fatal arrhythmias and sudden cardiac death. Serum potassium levels should be maintained above 4 mmol/l in heart failure patients. The aim of this study was to assess the prevalence of hypokalaemia in a cohort of patients admitted with decompensated heart failure.

Methods We performed a retrospective review of all patients admitted to St. James’s Hospital during a one year period from 1st January 2015 to 31st December 2015, with a principal diagnosis of congestive cardiac failure. A total of 330 patients were included. Blood results on admission, 24 hours and the final result prior to discharge were included for analysis.

Results On admission, 67 (22%) of the 309 patients with admission bloods had a serum potassium value of less than 4.0 mmol/l. Of the sub-group of patients that had bloods taken at both admission and 24 hours, (n=287) the percentage of patients with a serum potassium less than 4.0 mmol/l at 24 hours significantly increased from 21% to 36% (p < 0.001).

The average serum potassium of all patients fell significantly during the first 24 hours from 4.44 mmol/L to 4.17 mmol/l (p < 0.0001). This resulted in significantly more patients (11% vs 5%) with a potassium value of less than 3.5 mmol/l after 24 hours. (p<0.001).

Patients who had a serum potassium of less 3.5 mmol/l after 24 hours had a significantly lower serum magnesium on admission than the patients whose 24 hour potassium result was within the normal range. (0.71 mmol/L vs 0.81 mmol/L, p < 0.001).

Of the patients surviving to discharge, over 33% were discharged with serum potassium values less than 4.0 mmol/l.

Conclusion Our results demonstrate that a significant number of patients with heart failure have lower than desirable serum potassium levels on admission, through their inpatient stay and on discharge (figure 2). Within a cohort of patients hospitalised for exacerbations of heart failure, serum potassium levels fall during the first 24 hours (figure 1). There is a significant correlation between hypomagnesaemia on admission and the prediction of hypokalaemia 24 hours later. Hypokalaemia has been shown to be an independent predictor of mortality in heart failure. This study highlights the importance of close monitoring of serum potassium levels early in the admission, and suggests that identification of hypomagnesaemia can predict hypokalaemia at 24 hours. The authors advise early consideration of aldosterone antagonists or potassium replacement in these patients.

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