Potassium disorders

 

Hypokalaemia:

Cause

·      ↓Intake

·      ↑Output (urine, vomit)

·      Cell influx (alkalosis, b2 agonist, insulin)

·      Artefact (dilution)

Severity

·      Mild: 3-3.5

·      Mod: 2.5-3

·      Sev: <2.5

ECG

·      ST depression

·      T wave flattening

·      U waves

·      AV block

·      Ectopics

·      VT if severe

Significance

·      Common

·      Only dangerous if cardiac disease

Treatment

·      Check ECG

·      Asymptomatic: PO 20-80mmol/day in divided doses

·      Arrhythmia: IV 20mmol over 10 mins, then 10mmol over 10 mins

·      Arrest: IV 20mmol over 2 mins AND Mg 10mmol over 2 mins

 

Hyperkalaemia:

Cause

·      ↑Intake

·      ↓Output (renal failure, MRA, Addison’s)

·      Cell efflux (acidosis, digoxin, many drugs)

·      Artefact (haemolysis)

Severity

·      Mild: 5.5-6.5

·      Mod: 6.5-7.5

·      Sev: >7.5

ECG

·      Tall, tented T waves

·      Small or absent P waves

·      Widened PR

·      Widened QRS

·      Sine wave

·      Asystole

Significance

·      Common

·      Often dangerous

Treatment

Options:

·      Salbutamol 5mg neb (~↓1mM 2 mins)

·      Insulin 10 units over 20 mins + 50mL 50% Dex (~↓1mM 20 min)

·      CaCl 10mmol over 5 mins (stabilizes membrane)

·      Resonium: garbage

Indications:

·      Mild-mod: insulin + dextrose

·      Life-threatening: CaCl + salbutamol + insulin

·      Arrest: CaCl stat + salbutamol (how?) + insulin