electrolyte imbalance Flashcards
Give 5 causes of hyperkalaemia
- acute kidney injury
- drugs
- metabolic acidosis
- Addison’s disease
- rhabdomyolysis
- massive blood transfusion
Name 4 drugs that cause hyperkalaemia
- potassium sparing diuretics
- ACE inhibitors
- angiotensin 2 receptor blockers, * spironolactone
- ciclosporin
- heparin
What foods are high in potassium
- salt substitutes
- bananas, oranges, kiwi,
- avocado, spinach, tomatoes
ECG findings of hyperkalaemia
- Peaked or ‘tall-tented’ T waves (occurs first)
- Loss of P waves
- Broad QRS complexes
- Sinusoidal wave pattern
What is the main complication of untreated hyperkalaemia
arrhythmias e.g. ventricular fibrillation
How is hyperkalaemia classified
mild: 5.5 - 5.9 mmol/L
moderate: 6.0 - 6.4 mmol/L
severe: ≥ 6.5 mmol/L
When should emergency treatment be given for hyperkalaemia
All patients with severe hyperkalaemia (≥ 6.5 mmol/L) or with ECG changes should have emergency treatment
What is the mainstay of hyperkalaemia treatment
- IV calcium gluconate - Stabilisation of the cardiac membrane (does’t lower K+)
- Insulin and dextrose infusion: short term shift in potassium from ECF to ICF
What other treatment are used in the management of hyperkalaemia
- oral/rectal calcium resonium: removes K+ from the body
- nebulised salbutamol: ECF -> ICF
- haemodialysis
- stop exacerbating drugs
Give 4 causes of hypokalaemia with alkalosis
- vomiting
- thiazide and loop diuretics
- Cushing’s syndrome
- Conn’s syndrome (primary hyperaldosteronism)
Give 4 causes of hypokalaemia with acidosis
- diarrhoea
- renal tubular acidosis
- acetazolamide
- partially treated diabetic ketoacidosis
What electrolyte distrubance can cause hypokalaemia
hypomagnesemia prevents potassium absorption
Signs and symptoms of hypokalaemia
- muscle weakness
- hypotonia
ECG features of hypokalaemia
- U waves
- small or absent T waves
- prolonged PR interval
- ST depression
- Long QT
Causes of hypocalcaemia
- vitamin D deficiency (osteomalacia)
- chronic kidney disease
- hypoparathyroidism and pseudohypoparathyroidism
- rhabdomyolysis (initial stages)
- magnesium deficiency
- massive blood transfusion
- acute pancreatitis
Features of hypocalcaemia
- tetany: muscle twitching, cramping and spasm
- perioral paraesthesia
- if chronic: depression, cataracts
- Trousseau’s and Chvostek’s sign
What is Trousseau’s sign
carpopedal spasm caused by inflating the blood-pressure cuff to a level above systolic blood pressure in patients with hypocalcaemia
What is Chvostek’s sign
tapping over parotid causes facial muscles to twitch
ECG findings of hypocalcaemia
prolonged QT interval
How is hypocalcaemia managed
- Severe hypocalcaemia (e.g. tetany, prolonged QT, seizures): IV calcium gluconate 10ml of 10% solution over 10 mins
- ECG monitoring
- further management depends on underling cause
2 most common causes of hypercalcaemia
- Primary hyperparathyroidism: commonest cause in non-hospitalised patients
- Malignancy: the commonest cause in hospitalised patients
Which malignancies causes hypercalcaemia
- PTHrP from the tumour e.g. squamous cell lung cancer
- bone metastases
- myeloma
Apart from malignancy and primary hyperparathyroidism, give 5 other causes of hypercalcaemia
- sarcoidosis
- vitamin D intoxication
- acromegaly
- thyrotoxicosis
- drugs: thiazides, calcium-containing antacids
- dehydration
- Addison’s disease
Features of hypercalcaemia
- painful bones
- renal stones
- abdominal groans (constipation, N+V)
- psychic moans
- corneal calcification
- hypertension
ECG signs of hypercalcaemia
short QT interval
Investigations for hypercalcaemia
- measuring serum PTH
- measuring serum calcium
How is hypercalcaemia managed
- rehydration with normal saline, typically 3-4 litres/day
- bisphosphonates
- calcitonin
