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 700 6

Critical Care

Compendium

Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also the Innovation Lead for the Australian Centre for Health Innovation at Alfred Health and Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.

After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.

He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE.  He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.

His one great achievement is being the father of two amazing children.

On Twitter, he is @precordialthump.

| INTENSIVE | RAGE | Resuscitology | SMACC

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