Hypokalaemia
OVERVIEW
- the most common electrolyte abnormality in hospitalised patients
- mostly caused by drugs and GI disease
- most abundant cation on the body
- 2% of total body K+ is found in the extracellular space
- K+ homeostatsis largely regulated by the kidney (90% of daily K+ loss)
- rest eliminated via GI tract
- normal K+ = 3.5-5.0mmol/L
SEVERITY
- MILD – 3.0-3.5
- MODERATE – 2.5-3.0
- SEVERE
-> upper GI – vomiting
-> mid GI – fistula
-> lower GI – diarrhoea
-> other – sweat, burns, bleeding, RRT
ALL CAUSES (Dr from MIT)
Decreased K+ Intake – poor dietary intake, starvation,
Magnesium depletion -> increases renal potassium loss – poor diet, increased Mg2+ loss
Mineralocorticoid excess
- primary aldosteronism
- Cushing’s syndrome
- accelerated hypertension
- renal vascular hypertension
- renin producing tumour
- adrenogenital syndrome
- licorice excess
- Bartter syndrome
- Liddle syndrome
Increased Loss
- Drugs – diuretics, laxatives, liquorice, steroids, antibiotics (carbapenems, gentamicin, amphortericin B)
- Skin – profuse sweating, extensive burns
- GI – diarrhoea, vomiting, ileostomy, intestinal fistula, villous adenoma, laxatives
- Renal – tubular disorders, nephrogenic DI, various syndromes
- Endocrine – hyperaldosteronism, Cushing’s disease, Conn’s syndrome
- Dialysis – haemodialysis on low K+ dialysate, peritoneal dialysis
Transcellular Shift
- insulin/glucose therapy
- beta-agonists
- alkalosis: respiratory and metabolic
- hypokalaemic periodic paralysis
HISTORY
- mild: no symptoms
- fatigue
- muscle cramps
- weakness
- constipation
- rhabdomyolysis
- ascending paralysis
- respiratory failure
- arrhythmias
- symptoms more likely in pre-existing heart disease (IHD, CHF, LVH)
- medications: cause of hypokalaemia and also anti-arrhythmics (sotalol -> increased risk of arrhythmias)
EXAMINATION
- CVS: instability, arrhythmias
- NEURO: weakness, sensation
INVESTIGATIONS
- quantify severity and find cause
- K+
- Mg2+
- Ca2+, phosphate
- ECG: on seen in severe hypokalaemia, U waves, T wave flattening, ST depression -> VT/VF, long QT and Torsades
- digoxin level -> particularly at risk if become hypokalaemic
MANAGEMENT
- replace Mg2+ as facilitates a more rapid correction of hypokalaemia
- non-acute situation – 10-20mmol/hr
- life threatening arrhythmia:
-> K+ 20mol over 10 min
-> Mg2+ 10mmol over 10 min
References and Links
LITFL
- CCC – Hyperkalaemia management
- CCC – Hyperkalaemia DDx
- CCC – Hypokalaemia
- CCC – Hypokalaemia Mind Map
- ECG Library – Hyperkalaemia
- ECG Library – Hypokalaemia
- Clinical Case – Hyperkalaemia
- CCC – Potassium
Critical Care
Compendium
Chris is an Intensivist and ECMO specialist at The Alfred ICU, where he is Deputy Director (Education). He is a Clinical Adjunct Associate Professor at Monash University, the Lead for the Clinician Educator Incubator programme, and a CICM First Part Examiner.
He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives. He was one of the founders of the FOAM movement (Free Open-Access Medical education) has been recognised for his contributions to education with awards from ANZICS, ANZAHPE, and ACEM.
His one great achievement is being the father of three amazing children.
On Bluesky, he is @precordialthump.bsky.social and on the site that Elon has screwed up, he is @precordialthump.
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