Diabetes may be independent risk factor for hyperkalaemia

Editor—Wrenger et al reported severe hyperkalaemia in patients taking spironolactone in combination with angiotensin converting enzyme inhibitors or angiotensin-II antagonists.¹ The strikingly high prevalence of diabetes in these patients (80%) is likely to be important.

In a study of the prevalence of hyperkalaemia in an unselected diabetic outpatient population we found that hyperkalaemia was comparatively common in patients with both type 1 and type 2 diabetes.² Among 1764 consecutive patients attending a hospital diabetic clinic over one year, serum potassium concentration was > 5.0 mmol/l in 270 patients (15%) and > 5.4 mmol/l in 67 (4%). Six patients had a serum potassium concentration > 6.0 mmol/l. In contrast, only four patients had a serum potassium concentration of < 3.4 mmol/l.

A comparatively small proportion of patients were receiving drugs that could increase potassium (20% of patients with hyperkalaemia) because angiotensin-II antagonists were not available and the use of ACE inhibitors in patients with diabetes was less well established.

These data indicate that diabetes is an independent risk factor for hyperkalaemia. Dangerous hyperkalaemia after taking ACE inhibitor drugs and potassium sparing diuretics is well described in diabetic patients,³,⁴ and the British National Formulary advises caution prescribing amiloride for diabetic patients.

The report by Wrenger et al reinforces the concern that patients with diabetes seem to be particularly sensitive to the hyperkalaemic effect of drugs that block potassium excretion, particularly when used in combination. Doctors treating patients with diabetes should be aware of the dangers of precipitating life-threatening hyperkalaemia when prescribing for them, the combination of spironolactone with ACE inhibitors or angiotensin-II antagonists for heart failure being used with extreme caution.