44 Diuretics, hypokalemia and ventricular tachycardia: don't forget the PPI’s and magnesium
Matten, B.C. van der, Kerker, J.P., Dees, A.
Locatie(s): Auditorium 1
Categorie(ën): Parallelsessie
Case: A 49-year old woman presented at the emergency room with malaise, diarrhea, nausea and vomitus. Her medical history included an ischemic CVA and hypertension. The medication consisted of platelet aggregation inhibitors combined with a proton pump inhibitor (PPI), diuretics and a beta-blocker.
Retrospectively, she had been suffering from malaise and dizziness for several months. When visiting her GP for blood pressure monitoring, weeks before admission, she had severe cramps in her hand when inflating the cuff. Hypokalemia was found and diuretics were discontinued.
At presentation hypertension, tachycardia and a positive sign of Trousseau were observed. Her ECG showed diffuse abnormalities of repolarization. The laboratory results revealed a potassium level of 2.1 mmol/l, magnesium level of 0.15 mmol/l and calcium level of 1,78 mmol/l with normal albumin. Liver enzymes, kidney function and cardiac enzymes were all normal. Urine potassium was 52 mmol/l while the urine magnesium was < 0.50 mmol/l. The fractional the urine magnesium excretion was 2%, suggesting extra renal loss.
During vigorous electrolyte suppletion a short asymptomatic non sustained ventricular tachycardia was observed twice. After a couple of days, she made a complete recovery without any symptoms.
Discussion: Hypokalemia is a well known complication of diuretics. In about 40% of these patients a concomitant low serum level of magnesium will be found. This impairs the potassium repletion in the distal nephron and therefore increases the urine potassium level resulting in a refractory hypokalemia. When magnesium is administered the renal excretion of potassium decreases, even without potassium suppletion.
In this case, the persistent hypokalemia is most likely caused by renal loss due to PPI related hypomagnesemia and exaggerated by incidental gastrointestinal loss due to diarrhea and vomiting. PPI probably inhibit the mucosal absorption of magnesium, although the exact mechanism remains unclear.
The differential diagnosis of magnesium deficiency varies widely. It differs from low intake, redistribution changes, e.g. hungry bone syndrome, refeeding syndrome and alcoholism, to gastrointestinal losses, such as diarrhea and bypass surgery. Iatrogenic causes are known too, such as impaired absorption (PPI) or renal loss, (e.g. diuretics, antibiotics, hyperaldosteronism). Our patient most likely developed magnesium deficiency due the long-term use of a PPI in combination with gastro intestinal loss.
Conclusion: Hypokalemia is frequently accompanied by low magnesium. This might result in refractory hypokalemia and life threatening arrhythmias. The widespread use of PPI’s should alert the clinician to marked side effects of prescription of these drugs, especially in patients who are already treated with diuretics.