Hypo/hyperkalaemia Flashcards
What is the definition of hyperkalaemia?
serum potassium concentration >5.5 mmol/L
What are 3 groups of causes of hyperkalaemia?
- Imapired excretion from the kidney
- Increased release from cells
- Pseudohyperkalaemia/ artefact
What are 10 causes of hyperkalaemia due to impaired excretion?
- AKI
- CKD
- ACE inhibitors
- Potassium sparing diuretics e.g. spironoclactone
- NSAIDs
- Heparin/ LMWH
- Ciclosporin
- High dose trimethoprim
- Hypoaldosteronism (e.g. renal tubular acidosis type 4)
- Addison’s disease
What are 7 causes of hyperkalaemia due to increased release from cells?
- Lactic acidosis
- Insulin deficiency
- Rhabdomyolysis
- Tumour lysis syndrome
- Massive haemolysis
- Digoxin toxicity (NB: this can be precipitated by hypokalaemia)
- Beta blockers
What are 4 causes of pseudohyperkalaemia/artefact causes of hyperkalaemia?
- Haemolysis (traumatic venepuncture, prolonged tourniquet use, fist clenching)
- Delayed analysis (K+ leaks out of red blood cells)
- Contamination with potassium EDTA anticoagulant in FBC bottles
- Thrombocytopenia (K+ leaks out of platelets during clotting)
What are 7 ECG changes in hyperkalaemia?
- Tall, tented T waves
- Broad QRS complexes
- Prolonged PR interval
- Flattened p waves
- Idioventricular rhythms
- sine wave paterns
- VF/ asystole
What are 4 aspects of management of hyperkaelamia?
- Give 10ml 10% calcium gluconate over 10 minutes - cardioprotective
- IV insulin: 10 units of Actrapid in 50ml of 50% dextrose
- Nebulised salbutamol
- Calcium resonium 15g orally (or rectally)
When should you treat for hyperkalaemia?
potassium >6.5 or any ECG changes
What is the mechanism of action of calcium gluconate when treating hyperkalaemia?
cardioprotective (does’t reverse hyperkalaemia)
What is the mechanism of IV insulin + dextrose infusion when treating hyperkalaemia?
causing intracellular shift of potassium - only transient (also need to treat underlying cause)
What is the mechanism of action of nebulised salbutamol to treat hyperkalaemia?
intracellular shift of potassium - transient
In addition to the 4 initial steps of management of hyperkalaemia, what are 3 further aspects of management?
- check contributing drugs e.g. ACEi, spironolactone
- Once initial measures completed, recheck U+Es and ECG and glucose
- Check urinary potassium
Why can heparin/ LMWH cause hyperkalaemia?
inhibits aldosterone release
What are 5 types of drugs which can cause hyperkalaemia?
- Potassium sparing diuretics e.g. spironolactone
- Angiotensin-converting enzyme inhibitors
- Angiotensin-II receptor blockers e.g. losartan
- Ciclosporin
- Heparin
Why is metabolic acidosis associated with hyperkalaemia?
hydrogen and potassium ions compete with each other for exchange with sodium ions across cell membranes and in the distal tubule
What are 7 foods that are high in potassium?
- Salt substitutes - i.e. contain potassium rather than sodium
- Bananas
- Oranges
- Kiwi fruit
- Avocado
- Spinach
- Tomatoes
What is a type of drug which can potentially cause hyperkalaemia in patients with renal failure and why?
beta blockers - interfere with potassium transport into cells (hence why salbutamol, a beta agonist, can be used as emergency treatment)
What is more effect, oral or rectal (enema) calcium resonium?
rectal - because potassium is secreted by the rectum
How does calcium resonium work to treat hyperkalaemia?
it’s a resin that binds potassium in the gut to increase excretion in the rectum
What is the management for persistent hyperkalaemia in patients with AKI when all other methods have failed?
dialysis: haemofiltration/haemodialysis
What is the definition of hypokalaemia?
serum potassium <3.5 mmol/L
What are 2 ways that causes of hypokalaemia can be split?
- renal and extra-renal
- with or without hypertension
What is the difference between renal and extra-renal causes of hypokalaemia in terms of investigations?
urinary potassium; >20 mEq/L in renal causes, <20 mEq/L in extra-renal
What are 5 renal causes of hypokalaemia?
- Diuretis (e.g. furosemide, thiazides)
- Renal tubular acidosis
- Bartter’s, Liddle’s and Gitelman’s syndromes
- Endocrine causes (hyperaldosteronism, Cushing’s)
- Hypomagnesaemia
What are 3 extra-renal causes of hypokalaemia?
- Inadequate oral intake
- Gut losses (e.g. diarrhoea, vomiting, ileostomy, VIPoma, Zollinger-Ellison syndrome)
- Redistribution into cells (e.g. beta agonists, insulin, theophylline, alkalosis)
What are 4 causes of hypokalaemia with hypertension?
- Cushing’s sndrome
- Conn’s syndrome (primary hyperaldosteronism)
- Liddle’s syndrome
- 11-beta hydroxylase deficiency (accounts for 90% of congenital adrenal hyperplasia cases but this is NOT assoc/w HTN)
What is a drug which can potentially cause hypokalaemia associated with hypertension?
Carbenoxolone (anti-ulcer drug)
also liquorice excess
What are 5 causes of hypokalaemia without hypertension?
- Diuretics
- GI loss (e.g. diarrhoea, vomiting)
- Renal tubular acidosis (type 1 and 2)
- Bartter’s syndrome
- Gitelman syndrome
What are 2 clinical features of hypokalaemia?
- Muscle weakness
- Hypotonia
Which drug must you be careful with in hypokalaemia?
digoxin toxicity - hypokalaemia prediposes to digoin toxicity
also take care if on diuretics
What are 5 ECG features of hypokalaemia?
- U waves
- small or absent T waves
- prolonged PR interval
- ST depression
- long QT
(U have no P and no T but long PR and long QT)
What are 4 causes of hypokalaemia with alkalosis?
- Vomiting
- Thiazide and loop diuretics
- Cushing’s syndrome
- Conn’s syndrome (primary hyperaldosteronism)
What are 4 causes of hypokalaemia with acidosis?
- Diarhoea
- Renal tubular acidosis
- Acetazolamide
- Partially treated DKA
What should be the approach when treating hypokalaemia caused by magnesium deficiency?
may need to correct magnesium deficiency before potassium level can be normalised
What are 6 investigations to perform in hypokalaemia?
- ECG
- U+Es
- chloride
- bicarbonate
- glucose
- Urinary potassium and chloride
What is the treatment of mild hypokalaemia?
oral slow release potassium chloride (Sando K)
treat causes, check potassium regularly
What is the management of severe hypokalaemia? 5 aspects
- Continuous cardiac monitoring
- Check and correct magnesium (low Mg causes renal K+ wasting)
- IV infusion of 1L 0.9% saline containing 40 mmol KCl
- Avoid glucose and bicarbonate solutions
- Treat cause(s)
What is the maximum rate of potassium replacement in hypokalaemia?
10 mmol/L hour
What will need to be done to treat hypokalaemia if a faster rate of potassium replacement is required than 10 mmol per hour?
central line will need to be inserted - ITU/ call seniors etc.
