Potassium balance and its disorders
Potassium (K) is the most important intracellular cation. Only 2% of total body K are contained in the extracellular space.[i] K participates in a multitude of vital processes in every cell. Disorders of K balance are subdivided in those associated with hypo- and with hyperkalemia.[ii] Hypokalemia causes hyperpolarization, while hyperkalemia on the other hand leads to hypopolarization of the cell membrane. Both states result in cellular nonresponsiveness and dangerous cardiac arrhythmia as a most feared clinical complication.
Hypokalemia may result from reduced K intake associated with eating disorders,[iii] as well as from increased shifts of K into cells due to e.g. insulin administration, stimulation of the sympathetic nervous system,[iv] thyreotoxicosis and familial periodic paralysis.[v] However, the most important mechanism causing hypokalemia remains increased K loss mainly via the kidneys and/or the gastrointestinal tract. Renal K losses may be a consequence of acquired or genetic kidney diseases, such as Bartter´s syndome and endocrine disorders including Cushing´s syndrome. Furthermore, medications leading to renal K loss such as loop, thiazide and osmotic diuretics, amphotericin B, penicillins and theophillin are an often neglected reason for hypokalemia. Gastrointestinal causes of hypokalemia are prolongued vomiting and/or diarrhea during infections, inflammatory, malignant and genetic bowel disease but also as a consequence of laxative abuse.
Hyperkalemia is a frequent clinical abnormality in chronic kidney disease but often is also a consequence of high potassium intake in diets and of drugs known to raise potassium level.[vi] Further risk factors for hyperkalemia are acute kidney injury, cardiovascular disease and diabetes mellitus.[vii]
The main strength of UriSalt’s PoCT lies in particular in population screening and monitoring of groups that are known for increased risk of K imbalance. Therefore, clinically useful indications for K-PoCTs are some of the following:
K-PoCT Market potential focused “only” on patients with high medical need
K depletion (KD) and K overload (KO) focus groups:
(1) More than 700 million people worldwide have been reported in 2016 to be affected by chronic kidney disease (CKD).[viii] 14-20% of these show hypokalemia and a similar percentage manifest with hyperkalemia.[ix]
(2) Diuretics are by far the most common cause of hypokalemia.[x] Particularily thiazides have been reported to cause an 11-fold increase in hypokalemia as compared to patients without this drug.[xi] Patients with hyperkalemia treated with various types of RAAS inhibitors for cardiovascular disorders are another group to be monitored during the respective treatment periods.[xii]
(3) Eating disorders: The reported prevalence of eating disorders in the population is approximately 20/100.000[xiii] with hypokalemia described in 25% of patients.[xiv]
[i] Lang F, Persson PB, Murer H. Regulation des inneren Milieus. In:
Schmidt RF, Lang F, Heckmann M. In:Physiologie des Menschen. 31. Auflage. Heidelberg: Springer, 2010. S. 630-6932
[ii] Okposio MM, Onyiriuka AN, Abhulimhen-Iyoha BI. Point-of-admission serum electrolyte profileof children less than five years old with dehydration due to acute diarrhea. Trop Med Health43:247-52(2015)3
[iii] Heinz-Erian P, Akdar Z, Haerter B, Waldegger S, Giner T, Scholl-Bürgi S, Müller T. Urinaryexcretion markers identify sodium depletion in pediatric acute gastroenteritis. Klin Pädiatr228:24-8(2016)
[iv] Heinz-Erian P, Müller T, Krabichler B, Schranz M, Becker C, Rüschendorf F, Nürnberg P, RossierB, Vujic M, Booth IW, Holmberg C, Wijmenga C, Grigelioniene GG, Kneepkens CMF, Rosipal S, Mistrik M, Kappler M, Michaud L, Dozcy LC, Siu VM, Krantz M, Uterman G, Janecke AR. Mutationsin SPINT2 cause a syndromic form of congenital sodium diarrhea. Am J Hum Genet 84:188-96(2009)
[v] Bilal A, Sadig MA, Haider N. Frequency of decreased hyponatremia and hypokalemia inmalnourished children with acute diarrhea. J Pak Med Assoc 66:1077-80(2016)
[vi] Bower TR, Pringle KC, Soper RT. Sodium deficit causing decreased weight gain and metabolicacidosis in infants with ileostomy. J Pediatr 23:567-72(1988)
[vii] Knepper C, Ellemunter H, Eder J, Niedermayr K, Haerter B, Hofer P, Scholl-Bürgi S, Müller T,Janecke AR, Heinz Erian P. Low sodium status in cystic fibrosis – as assessed by calculatingfractional Na+-excretion – is associated with decreased growth parameters. J Cyst Fibr 14:400-405(2016)
[viii] Coates AJ, Crofton PM, Marshal T. Evaluation of salt supplementation in CF infants. J Cyst Fibr8:382-5(2009)
[ix] Dekker MJ, Marcelli D, Carnaud B, Konings CJ, Leunissen KM, Levin NW, Carioni P, Maheshwari V, Raimann JG,van der Sande FM, Usvyat LA, Kotanko P, Kooman JP. Unraveling the relationship between mortality,hyponatremia, inflammation and malnutrition in hemodialysis patients: results from the international MONDOinitiative. Eur J Clin Nutr 70:779-84(2016)
[x] Mayer CU, Treff G, Fenske WK, Blouin K, Steinaker JM, Allolio B. High incidence of hyponatremia in rowersduring a four-week training camp. Am J Med 128;1144-51(2015)
[xi] Levy-Shraga Y, David D, Vered I, Kochavi B, Stein D, Modan-Moses D. Hyponatremia and decreased bonedensity in adolescent inpatients diagnosed with anorexia nervosa. Nutrition 32:1097-1102(2016)
[xii] Rodriguez MJ, Alcaraz A, Solana MJ, Garcia A. Neurological symptoms in hospitalizedpatients: do we assess hyponatremia with sufficient care? Acta Paediatr 103: e7-e10(2014)
[xiii] Corona G, Guiliani C, Parenti G, Parenti G, Norello D, Verbalis JG, Forti G, Maggi M, Peri A. Moderatehyponatremia is associated with increased risk of mortality: evidence from a meta-analysis. PLOS ONE8:e80451(2013)
[xiv] Wassner SJ, Kulin HE. Diminished linear growth associated with chronic salt depletion. Clin Pediatr29:719-21(1990)
[xv] Thomas L. Messung von Natrium. In: Labor und Diagnose.TH-Books 5th edition, Chapter 8.2, pp 295-303.
[xvi] Subasinghe AK, Arabshani S, Businye D, Evans RG, Walker KZ, Ridell MA, Thrift AG. Association between salt and hypertension in rural and urban populations of low and middle income countries: a systematic review and metaanalysis of population-based studies. Asia Pac J Clin Nutr 25:402-13(2016)
[xvii] http://www.statistik.gv.at/web_de/statistiken/index.html
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