Hyperkalemia and Hypokalemia in CKD: Prevalence, Risk Factors, and Clinical Outcomes.

Abnormalities of serum potassium are common in patients with CKD. Although hyperkalemia is a well-recognized complication of CKD, the prevalence rates of hyperkalemia (14%-20%) and hypokalemia (12%-18%) are similar. CKD severity, use of medications such as renin-angiotensin-aldosterone system inhibitors and diuretics, and dietary potassium intake are major determinants of serum potassium concentration in CKD. Demographic factors, acid-base status, blood glucose, and other comorbidities contribute as well. Both hyperkalemia and hypokalemia are associated with similarly increased risks of death, cardiovascular disease, and hospitalization. On the other hand, limited evidence suggests a link between hypokalemia, but not hyperkalemia, and progression of CKD. This article reviews the prevalence rates and risk factors for hyperkalemia and hypokalemia, and their associations with adverse outcomes in CKD.

Race influences the safety and efficacy of spironolactone in severe heart failure.

BACKGROUND: The incidence of hyperkalemia caused by mineralocorticoid receptor antagonists may vary by race, but whether race influences efficacy of mineralocorticoid receptor antagonists in heart failure (HF) is unknown. METHODS AND RESULTS: We assessed hyperkalemia and outcomes in African Americans (AAs; n=120) and non-AAs (n=1543; white 93%) with New York Heart Association (NYHA) class III or IV HF and left ventricular dysfunction who were randomized to spironolactone, titrated to 25 or 50 mg daily or placebo, in the Randomized Aldactone Evaluation Study (RALES). AA participants were significantly younger, less likely to have an ischemic HF pathogenesis, more likely to be NYHA functional class IV, and more likely to have a higher estimated glomerular filtration rate and heart rate, less hypertension, diabetes mellitus, or history of myocardial infarction compared with non-AA participants. Potassium increased with spironolactone in non-AAs (4.29±0.5-4.55±0.49 mmol/L) but not in AAs (4.32±0.54-4.31±0.49 mmol/L; race by treatment interaction, P=0.03) during the first month and remained higher throughout the trial. Compared with AAs, non-AAs were more likely to attain maximal spironolactone dose (13.9% versus 5.8%; P=0.04) and had higher rates of hyperkalemia (potassium>5.5 mmol/L; 9.7% versus 4.2%; P<0.046), as well as lower rates of hypokalemia (potassium<3.5 mmol/L; 5.6% versus 17.9%; P<0.001). After adjustment for differences in baseline characteristics and achieved study drug dose, spironolactone reduced the combined end point of death or hospitalization for HF in non-AAs (hazard ratio, 0.63; 95% confidence interval, 0.55-0.73) but not in AAs (hazard ratio, 1.07; 95% confidence interval, 0.67-1.71; P value for interaction=0.032). CONCLUSIONS: AAs with HF exhibited less hyperkalemia and more hypokalemia with spironolactone compared with non-AAs and seemed to derive less clinical benefit. These hypothesis-generating findings suggest that safety and efficacy of mineralocorticoid receptor antagonists may differ by race.

Phenotype-genotype correlation in antenatal and neonatal variants of Bartter syndrome.

BACKGROUND: Ante/neonatal Bartter syndrome (BS) is a hereditary salt-losing tubulopathy due to mutations in genes encoding proteins involved in NaCl reabsorption in the thick ascending limb of Henle's loop. Our aim was to study the frequency, clinical characteristics and outcome of each genetic subtype. METHODS: Charts of 42 children with mutations in KCNJ1 (n = 19), SLC12A1 (n = 13) CLCNKB (n = 6) or BSND (n = 4) were retrospectively analysed. The median follow-up was 8.3 [0.4-18.0] years. RESULTS: We describe 24 new mutations: 10 in KCNJ1, 11 in SLC12A1 and 3 in CLCNKB. The onset of polyhydramnios, birth term, height and weight were similar for all groups; three patients had no history of polyhydramnios or premature birth and had CLCNKB mutations according to a less severe renal sodium wasting. Contrasting with these data, patients with CLCNKB had the lowest potassium (P = 0.006 versus KCNJ1 and P = 0.034 versus SLC12A1) and chloride plasma concentrations (P = 0.039 versus KCNJ1 and P = 0.024 versus SLC12A1) and the highest bicarbonataemia (P = 0.026 versus KCNJ1 and P = 0.014 versus SLC12A1). Deafness at diagnosis was constant in patients with BSND mutations; transient neonatal hyperkalaemia was present in two-thirds of the children with KCNJ1 mutations. Nephrocalcinosis was constant in KCNJ1 and SLC12A1 but not in BSND and CLCNKB patients. In most cases, water/electrolyte supplementation + indomethacin led to catch-up growth. Three patients developed chronic renal failure: one with KCNJ1 mutations during the second decade of age and two with CLCNKB and BSND mutations and without nephrocalcinosis during the first year of life. CONCLUSIONS: We confirmed in a large cohort of ante/ neonatal BS that deafness, transient hyperkalaemia and severe hypokalaemic hypochloraemic alkalosis orientate molecular investigations to BSND, KCNJ1 and CLCNKB genes, respectively. Chronic renal failure is a rare event, associated in this cohort with three genotypes and not always associated with nephrocalcinosis.