Contents
The Basics
- 98% is intracellular
- Serum range 3.5 – 5 mmol/L
- K+ and H+ tend to vary together
- Most body secretion is in urine – from distal tubules
Shifts K+ INSIDE cells
- Insulin
- Aldosterone
- β-adrenergic stimulation
- Alkalosis
Shifts K+ OUTSIDE cells
- Addison’s disease
- β-blockade
- Acidosis
- Cell lysis
Hypokalaemia
ΔΔ
- Usually due to Excess Losses
- GI losses
- Diarrhoea
- Vomiting
- Renal losses
- Diuretics
- Excess mineralocorticoids
- Intracellular shift
- β2– adrenergic stimulation
- Insulin
- Alkalosis
Signs & Symptoms
- Muscular dysfunction
- Weakness
- Cramping
- Fasciculation
- Tetany
- ECG changes
- T wave depression
- ST sagging
- U wave prominence
- Prolonged P-R interval
Management
- Correct any potential cause e.g. diuretics
- Mild – Oral K+ supplements
- routine K+ replacement is not needed in most patients on diuretics
- Severe – Cautious IV K+
- Must be: < 20mmol/h and < 40 mmol/L
Hyperkalaemia
ΔΔ
- Renal
- Oliguric renal failure
- K+ sparing diuretics
- Metabolic acidosis
- Adrenal Insufficiency – e.g. Addison’s
- Drugs
- ACE-inhibitors
- B- blockers
- NSAIDS
- Iatrogenic K+
- Rhabdomyolysis
- Artefact – Haemolysis
Signs & Symptoms
- ECG changes
- Tall Tented T waves (TTT)
- Small P waves
- Wide QRS complexes
- Ventricular Fibrillation!!!
- Weakness
- Occasional paralysis
- Usually death first
Management
- Correct any potential cause e.g. beta-blockers
- If mild simply reduce intake
K+ > 6.5 mmol/L OR ECG changes –> URGENT TREATMENT
- Calcium Gluconate (10ml-10%)
- IV over 2 mins
- Repeat as necessary (stabilises the heart)
- Insulin & Glucose IV
- Drives K+ into cells
- Nebulised Salbutamol
- Polystyrene sulfonate resin (trade name- Calcium resonium)
- Orally or enema if N&V
References
- Guyton & Hall. Textbook of Medical Physiology
- The Merck manual
- Oxford Handbook of Clinical medicine.
- Patient.co.uk