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Hypokalaemia- Low potassium

Hypokalaemia is serum potassium concentration of less than 3.5 mmol/ L. Mild hypokalemia is a K+ level of 3.0 to 3.4 mmol/ L. Moderate is 2.5 to 2.9 mmol/L and severe is > 2.5 mmol/L

Causes – redistribution in cells. Acid-base metabolic acidosis

Hormonal -Insulin ( ↑↑ K+ entry into cells ) Beta 2 adrenergic agonists Alpha adrenergic antagonists. Anabolic state -Vitamin B12 or folic acid therapy ( ↑ RBC prod’n ) Granulocyte-
macrophage colony stimulating factor ( WBC production ) Total parenteral nutrition. Other – Pseudo-hypokalaemia Hyperthermia Hypokalaemic periodic paralysis Thyrotoxic periodic paralysis Barium toxicity

dietary –Low intake ( eg starvation , anorexia , old-tea & toast diet )
Daily minimum requirement is considered to be ~ 1600 to 2000 mg
 ( 40-50 mmol or mEq )

Drugs –Amphotericin B Beta agonists Diuretics ( particularly thiazide ) Glucocorticoids ( at high doses ) or mineralocorticoids Aminoglycosides Lithium Insulin overdose Verapamil intoxication Xanthines Decongestants Laxatives

Skin loss –Excessive perspiration
 ( strenous exercise , severe heat stress )

gastrointestinal loss –Vomiting or NG loss Diarrhoe or laxative abuse Ostomy losses Villous adenoma VIPoma

Others – ↑ ed mineralocorticoid activity 
♦ hyperaldosteronism 1ary and 2ary
♦ Cushing’s
♦ congenital adrenal hyperplasia
♦ Bartter’s , Gitelman’s synd Renal tubular acidosis 
( type 1 and 2 ) Salt wasting nephropathy Polyuria Hypomagnesemia

 

History -assessment –Full history Focus on medications ( eg diuretics , laxatives etc ) Associated symptoms ( eg diarrhoea ) Examination- flaccid muscle weakness , arrythmia
○ BP
○ Volume status Initial investigations
○ Us and Es , Bl glucose
○ Bicarbonate
○ Urinary potassium
♦ low urinary K + ( < 20 mEq/L ) → suggests GI loss , poor intake or a shift of EC K+ to IC
♦ ↑ urinary K+ ( > 40 mEq/L ) → suggests renal loss
○ Calcium
○ Magnesium → if cause not obvious and moderate to severe hypokalaemia ECG

ECG Ask for an ECG if < 3.0 mmol/L Flat or inverted T waves Prominent U waves Depressed ST segment Prolonged QT interval 1st or 2nd degree heart block
Changes usually appear 
when K + < 2.7 mmol/ L
 Arrhythmias -commonly seen due to hypokalaemia include
○ atrial tachycardia with or without block
○ AV dissociation
○ Ventricular tachycardia
○ Ventricular fibrillation

General approach –Level of severity-
 speed of onset-What is the trend ? is there a rapid decline ?
compare to previous levels-What is the trend ? is there a rapid decline ?
compare to previous levels

Common causes –Most common cause seen in general practice is use of loop / thiazide diuretics
 Hypoaldosteronism – due to heart failure or liver disease is also common- 

consider Conns syndrome if ○ high serum sodium ○ normal or low potassium ○ refractory hypertension
 Increased losses eg from GI tract
Vomiting – if prolonged & patient is frail
 Movement of potassium into the intracelluluar fuid e.g alkalosis , burns or other trauma , medicines e.g high dose insulin

Groups at increased risk of arrhythmia –Some people are at ↑ ed risk of arrhythmia due to hypokalaemia – these include those who are taking Digoxin
the arrhytjmogenic potential of dogoxin is enhanced by hypokalaemia in patients with heart failure
 people with cardiac disease as
○ ischaemic heart disease
○ heart failure
○ left ventricular hypertrophy
 Co-existing hypomagnesemia -↓ Mg can induce renal K wasting. A combined deficiency may potentiate the risk of cardiac arrhythmias – both are pro-arrhythmic



management – based on level of potassium –

3.0 to 3.4 mmol/ L In most patients usually asymptomatic No ECG changes Consider oral replacement ( see hypokalaemia in adults- treatment ) Monitor and adjust treatment accordingly Correct any other co-existing electrolyte abnormality for e.g magnesium

2.5 to 2.9 mmol / L None or minor symptoms Refer for IV replacement if patient cannot tolerate oral preparations Decide on an individual basis based on circumstances Ensure more close monitoring if replacing with oral potassium in the community

Less than 2.5 mmol / L Intravenous replacement is indicated Immediate goal is to prevent or correct cardiac electrical disturbances and serious neuromuscular weakness Monitoring under hospital environment Arrange admission/ transfer

Discussion –Hypokalaemia is the most frequently seen electrolyte abnormality founs in hospitalised patients – occurring in up to 20 % of patients and is associated with an increased mortality in this group
 Consider additional tests if cause is unclear ( in 1ary care )
○ urinary potassium excretion ( not usually ordered in 1° care )
○ serum magnesium
○ serum bicarbonate ( if an acid-base disorder suspected )
○ check serum digoxin level is patient is on digitalis

Two common components of diagnostic evaluation are







 Trudge carefully in complicated scenarios for e.g
○ hypokalaemia in patient with heart failure who is taking digoxin in combination with a loop diuretic and an ACE inhibitor – decision of whether to administer potassium replacement can be complex
○ CKD patients
 Further evaluation of patients with persistent hypokalaemia can be complex and involve checking serum aldosterone , renin and imaging tests as CT. MRI of adrenal glands- Refer these patients to secondary care


LINKS AND RESOURCES

PATIENT INFORMATION

PILs on this topic are a bit hard to find- few useful ones are listed below

PDF from Cheshire and Wirral Partnership NHS Foundation Trust http://www.cwp.nhs.uk/media/2934/hypokalemia-a-h-14-637.pdf

Cleveland Clinic has a useful page for patients https://my.clevelandclinic.org/health/diseases/17740-low-potassium-levels-in-your-blood-hypokalemia

Advice on Potassium-rich food from Michigan Medicine UOM https://www.uofmhealth.org/health-library/abo9047

This is a discharge instruction for patients with hypokalaemia who are being sent home from Fairview -list of food with high potassium contents https://www.fairview.org/patient-education/86379

INFORMATION FOR HEALTHCARE PROFESSIONALS

U Wave – an excellent article from Life in the Fast Lane https://litfl.com/u-wave-ecg-library/

ECG changes in hypokalemia from the Permanente Journal https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3383164/

1-minute video on hypokalaemia https://www.youtube.com/watch?v=ZTX11aMtz7o
Another 5-minute video from EKG guy https://www.youtube.com/watch?v=otYd3khMAYI

Article available via Researchgate Kardalas, Efstratios & Paschou, Stavroula & Anagnostis, Panagiotis & Muscogiuri, Giovanna & Siasos, Gerasimos & Vryonidou – Bompota, Andromachi. (2018). Hypokalemia: A clinical update. Endocrine Connections. 7. EC-18. 10.1530/EC-18-0109. https://www.researchgate.net/publication/323766229_Hypokalemia_A_clinical_update

Potassium physiology – hungry for knowledge ? master the topic

A 59 page PPt presentation by Dr Wingo https://kdigo.org/wp-content/uploads/2018/04/3-Wingo-KDIGO-Potassium-HomeostasisFn1w.pdf

American Journal of Kidney Disease- Core curriculum Physiology and Pathophysiology of
Potassium Homeostasis: Core Curriculum https://www.ajkd.org/article/S0272-6386(19)30715-2/pdf

 

References;

  1. Harrison’s manual of medicine -Dennis L. Kasper , Tinsley R Harrison McGraw-Hill
  2. Professional Making sense of the ECG -Andrew R.Houghton , David . Gray
  3. The ECG in practice- John R. Hampton ; With Contributions by David Adlam
  4. Hypokalaemia E Medicine accessed via http://emedicine.medscape.com/article/242008-overview?
pa=weHKMk1EXh%2FiUtWGpAhdEFzlkpn9QrYrwdlgLpJMgPXczVkfbtlOBwr
DeyfdoPkyvYv0Rcg53ELI2WxcHuupIychrzF%2F7vlnSF6AEX%2F09M8%3D#a3
  5. Acid-base, fluids , and electrolytes- Robert F Reilly , Jr.,Mark A Perazella
  6. Medicine compendium Sando-K accessed via https://www.medicines.org.uk/emc/medicine/812
  7. Investigating hypokalaemia BMJ 2013 ;347:f5137
  8. ABC of intravenous fluids , elctrolytes disorders and AKI management in adults via http://www.wasd.org.uk/wp-content/uploads/2017/03/C05-Hypokalaemia.pdf
  9. Serum potassium imbalance BPAC org via https://bpac.org.nz/BT/2011/September/imbalance.aspx 
  10. Kardalas E, Paschou SA, Anagnostis P, Muscogiuri G, Siasos G, Vryonidou A. Hypokalemia: a clinical update. Endocr Connect. 2018;7(4):R135–R146. doi:10.1530/EC-18-0109 via https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5881435/
  11. Management of hypokalaemia Dr Anthony Crosse GMJ journal via https://www.gmjournal.co.uk/media/21661/feb2010p103.pdf

 

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