Nephrol Dial Transplant (2001) 16: 1112-1116
© 2001 European Renal Association-European Dialysis and Transplant Association
Personal Opinion
The hypertensive patient with hypokalaemia: the search for hyperaldosteronism
Division of Nephrology/Hypertension, University Hospital of Berne, Berne, Switzerland
Introduction
Factitious normokalaemia
The physical chemical determination of plasma potassium concentration is very precise. However, the matrix where potassium is determined, the plasma, is a notoriously unreliable partner. This fact is generally recognized when patients with hyperkalaemia are considered. Because potassium concentrations are 20-fold higher within the cell than outside, the potassium concentration is facticiously high whenever potassium shifts from the intra- to the extracellular compartment during or after venipuncture. As a corollary, in a subject with hypokalaemia in vivo one might measure ‘normal’ potassium concentrations when such a factitious potassium shift has occurred. Patients like this may in reality be hypokalaemic. Thus, in clinical practice we have to ascertain that normokalaemia is not an artifact in patients with hypertension. The mechanisms accounting for factitious normalkalaemia are: (i) repeated fist clenching with or without tourniquet; (ii) traumata venipuncture with a small gauge needle; (iii) delayed centrifugation or placing the sample on ice; (iv)
Transtubular potassium gradient (TTKG) and related tests
Magnetic resonance angiography
Hormones
Personal history or therapy ‘exjuvantibus’
Conclusions
Acknowledgments
Notes
References
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