Ion imbalances Flashcards
(38 cards)
What does SIADH stand for?
Syndrome of inappropriate ADH secretion
What is SIADH?
Continued ADH excretion when there is no need,
I.e. there is normal plasma volume and the plasma is hypotonic (low concentration)
The urine is inappropriately concentrated and excess water is not lost
When is vasopressin secreted in healthy people?
What does it do?
Where does it act?
When the body senses that there is low plasma volume or that the plasma is of a high concentration (there is not enough water in the blood)
Vasopressin/ADH controls water reabsorption via its action on the kidney nephrons, causing the retention of water (but not the retention of solutes). Therefore by increasing water retention, ADH causes dilution of the blood and in turn decreases the concentration of solutes
Distal convoluted tubule
Causes of SIADH?
Brain damage: meningitis, SAH
Malignancy: small-cell lung cancer
Drugs: carbemazepine, SSRIs, amitriptyline
Infectious: atypical pneumonia, lung abscess, cerebral abscess
Hypothyroid
Clinical features of SIADH?
Nausea, headache, irritability
Hyponatraemia caused by the increased amount of water
(Na conc doesn’t change, but water conc increases)
Concentrated urine
What can hyponatraemia cause?
Fits and coma
Investigation of SIADH?
Blood:
- low serum Na
- low plasma osmolality
Urine:
- concentrated
- contains a lot of Na
MRI: to check state of hypothalamus and pituitary
Treatment of SIADH?
Restrict water intake
Treat underlying cause
Demeclocycline: drug that inhibits action of vasopressin at kidney
Vasopressin antagonist: tolvaptan
Causes of hyponatraemia?
Low sodium
SIADH Sodium deficiency Renal failure Malignancy Addison's
What is a detrimental impact that hyponatraemia can have on the brain?
Osmotic demyelination
Which can cause irreversible brain dysfunction
Clinical features of hypercalcaemia?
Asymptomatic Bones: pain Stones: renal calculi Abdo groans: constipation, pain Psychic moans: depression, fatigue Thrones: polyuria
Causes of hypercalcaemia?
Hyperparathyroidism
Bone metastases
Dehydration: loss of water, and no change in Ca conc will cause hypercalcaemia
Investigation of hypercalcaemia?
Raised calcium in blood
Management of hypercalcaemia?
Treat the cause
Rehydrate with IV saline
Loop diuretics, not thiazide
Removal of parathyroid to treat hyperparathyroidism
Clinical features of hypocalcaemia?
Increased excitability of nervous system: muscle twitching, spasms, seizures
Numbness around the mouth, extremities, cramps
Can cause death if extreme and untreated
Causes of hypocalcaemia?
Renal failure and CKD
Parathyroid deficiency
Insufficient vitamin D
Investigation of hypocalcaemia?
Blood: low calcium
eGFR to check for CKD
Treatment of hypocalcaemia?
Treat the cause
Give calcium gluconate
What calcium imbalance is caused by:
Hyperparathyroidism
Hypoparathyroidism?
HYPER = HYPERcalcaemia
HYPO = HYPOcalcaemia
Clinical features of hyperkalaemia?
Asymptomatic until it can cause arrhythmias and MI
Impaired neuromuscular transmission: weakness and paralysis
Can cause death due to heart problems
Causes of hyperkalaemia?
Renal problems
Metabolic acidosis
Adrenal insufficiency
Drugs: K sparing diuretics
Investigation of hyperkalaemia?
Bloods: check potassium
ECG: peaked T waves, prolonged PR, widened QRS and reduced P
Treatment of hyperkalaemia?
IV fluid bolus
Calcium gluconate to protect the heart
10u insulin + IV dextrose
Salbutamol
Clinical features of hypokalaemia?
Asymptomatic usually
Muscle weakness
Cardiac arrhythmias and sudden death
Polyuria
