Hypothesis: a simple algorithm to distinguish between hypoaldosteronism and renal aldosterone resistance in patients with persistent hyperkalemia.
OBJECTIVE
Many patients with hyperkalemia have a readily identifiable cause, which leads to appropriate management. In others, particularly those with a reduced glomerular filtration rate, differentiating between (relative) hypoaldosteronism (HA) and renal aldosterone resistance (RAR) can be problematic. The aim of this study was to see if a plasma aldosterone to potassium algorithm could be defined which would help identify patients with hyperkalemia owing to suboptimal levels of aldosterone, thereby validating treatment with 9-alpha-fluhydrocortisone, instead of cation exchange resins, if more conservative treatment fails.


METHODS
A literature search for, and analysis of, studies providing details of plasma aldosterone and plasma potassium in normals (made hyperkalemic)and patients with a plasma potassium >5.3 mmol/L, and a contemporaneous plasma aldosterone.


RESULTS
One study was found in which normals were made significantly hyperkalemic (to 6.3 mmol/L). These subjects, while on a high sodium, low potassium (western) diet (n = 5), provided an arbitrary definition of a simple aldosterone to potassium algorithm for diagnosis (factored aldosterone (FAldo) = plasma aldosterone/(plasma K - 4.2)). The limit for FAldo is set at 280(pmol/L) or 10(ng/dL): results below the limit suggest HA; above the limit, RAR. This algorithm was then tested against, and, when plasma potassium was greater than 5.3, found to be consistent with, reported patients with confirmed HA (n = 33) and pseudohypoaldosteronism (n = 23). The ratios in reported patients with renal failure (n = 43) were consistent with either HA (n = 30) or RAR(n = 13).


OBJECTIVE
In hyperkalemic patients a plasma aldosterone to potassium algorithm may help distinguish HA from RAR, thereby guiding therapy.
University of Melbourne, School of Rural Health, Shepparton, Victoria, Australia. wadam@unimelb.edu.au
William R
WR
Adam
D000450:Aldosterone / Q000097:blood / Q000494:pharmacology*; D000465:Algorithms; D005919:Glomerular Filtration Rate; D006801:Humans; D006947:Hyperkalemia / Q000209:etiology*; D006994:Hypoaldosteronism / Q000145:classification / Q000175:diagnosis*; D007668:Kidney / Q000187:drug effects* / Q000378:metabolism; D011188:Potassium / Q000378:metabolism
D000450:Aldosterone; D011188:Potassium