Potassium and Electrolytes Flashcards
A 67-year-old man was started on bendroflumethiazide for hypertension 2 weeks ago. He has had D& V for 2 days. He has dry mucous membranes and decreased skin turgor.
Urea & electrolytes: Na+: 129 mmol/L K+: 3.5 mmol/L Ur: 8.0 mmol/L Cr: 100 micromol/L
Management?
Clinical assessment = hypovolaemic
DD: diarrhoea, vomiting, diuretics, salt
Management: Volume replacement with 0.9% saline
A 57-year-old woman has breathlessness worse on lying flat. Her past medical history includes a Non-STEMI. She is on ramipril, bisoprolol, aspirin and simvastatin. She has elevated JVP, bibasal crackles and bilateral leg oedema. Urea & electrolytes: Na+: 128 mmol/L K+: 4.5 mmol/L Ur: 8.0 mmol/L Cr: 100 micromol/L
Management?
Clinical assessment = hypervolaemic
DD: cardiac failure
Management: fluid restriction and treat the underlying cause
A 55-year-old man has jaundice. He has a past history of excessive alcohol intake. He has multiple spider naevi, shifting dullness and splenomegaly.
Urea & electrolytes: Na+: 122 mmol/L K+: 3.5 mmol/L Ur: 2.0 mmol/L Cr: 80 micromol/L
Management?
Clinical assessment = hypervolaemic
DD: Cirrhosis
Management: fluid restriction, treat the underlying cause
A 40-year-old woman presents with fatigue, weight gain, dry skin and cold intolerance. On examination she looks pale.
Urea & electrolytes: Na+: 130 mmol/L K+: 4.2 mmol/L Ur: 5.0 mmol/L Cr: 65 micromol/L
Management?
Clinical assessment = euvolaemia
DD: hypothyroidism
Management: TFTs, treat the underlying cause (thyroxine replacement)
A 45-yeard-old woman presents with dizziness and nausea. On examination she looks tanned and has postural hypotension.
Urea & electrolytes: Na+: 128 mmol/L K+: 5.5 mmol/L Ur: 9.0 mmol/L Cr: 110 micromol/L
Management?
Clinical assessment = euvolaemia
DD: Adrenal insufficiency
Management: Short synacthen test, treat the underlying cause (hydrocostisone and fludrocortisone)
A 62-year-old man has chest pain, cough and weight loss. He looks cachectic. He has a 30 pack year smoking history. Urea & electrolytes: Na+: 125 mmol/L K+: 3.5 mmol/L Ur: 7.0 mmol/L Cr: 85 micromol/L
Management?
Clinical assessment = euvolaemic
DD: SIADH
Management: Plasma and urine osmolality, treat the underlying cause
A 20-year-old man presents with polyuria and polydipsia. On examination he has bitemporal hemianopia.
Urea & electrolytes: Na+: 150 mmol/L K+: 4.0 mmol/L Ur: 5.0 mmol/L Cr: 70 micromol/L
Management?
Clinical assessment = Hypernatraemia
DD: DI
Management: Serum glucose (exclude diabetes mellitus) Serum potassium (exclude hypokalaemia) Serum calcium (exclude hypercalcaemia) Plasma & urine osmolality Water deprivation test
Causes of hyperkalaemia
Renal impairment: reduced renal excretion
Drugs: ACE inhibitors, ARBs, spironolactone
Low aldosterone (Addison’s disease, type 4 renal tubular acidosis - low renin, low aldosterone)
Released from cells: rhabdomyelosis, acidosis
ECG in hyperkalaemia
Peaked T wave
Management of hyperkalaemia
10ml 10% calcium gluconate
50ml 50% dextrose + 10 units of insulin
Nebulized salbutamol
Treat the underlying cause
Initial investigation in hypertension with hypokalaemia
Aldosterone: Renin ratio
Normal serum concentration of potassium
Potassium is the most abundant intracellular cation
Serum concentrations: 3.5-5mmol/L
Which hormones are involved in renal regulation of potassium
Angiotensin II
Aldosterone
Renin-angiotensin-aldosterone system
Angiotensinogen (from liver) –> angiotensin I (renin from JGA)
Angiotensin I –> angiotensin II (ACE) (in lungs)
Angiotensin II –> aldosterone (from adrenal)
Aldosterone increases secretion of renin from JGA
What stimulates renin secretion in the kidney
Na+ and H2O retention
Increased blood volume/pressure
