ENDOCRINE: Electrolyte abnormalities incl parathyroid Flashcards
SIADH, calcium NEED TO ADD MORE ON PARATHYROIDISM
What is the relevance of hyponatraemia?
Very commonly affects hospital patients, up to 30% of hosp patients will have hyponatraemia
Hyponatraemia is characterised by a low concentration of sodium in the serum, specifically less than 135mmol/L.
What are the symptoms of hyponatraemia?
Early symptoms: headache nausea vomitting general malaise
Later signs:
confusion
agitation
drowsiness
What serious symptoms can acute severe hyponatraemia cause?
Seizures
Resp depression
Coma
Death
What common medication can cause hyponatraemia?
thiazide like diuretics
ACEi
SSRIs
Furosemide
What is osmolality?
How salty the blood is, low osmolality means less salt
What is a complication of acute severe hyponatraemia?
cerebral oedema
In patient with severe acute hyponatraemia what would always prescribe?
Hypertonic saline
What are the hallmark biochemical features of primary adrenal failure?
Hyperkalaemia, hyponatraemia, raised urea and mild anaemia, hypoglycaemia
What biochemical investigations would you do in a patient with hyponatraemia?
Serum osmolality, urine osmolality, urine sodium, thyroid function and assessment of cortisol response
What is the first thing to do if a patient presents with low serum osmolality?
Rule out non-hypo- osmolar hyponatraemia e.g. hyperglycaemia
What would a low serum osmolality and urine osmolality of less than 100mosmol/kg indicate?
primary polydipsia or inappropriate IV fluid administration
What is the next steps in investigation if a patient has low serum osmolality and a urine osmolality of greater than 100mosmol/kg?
You need to measure their urine sodium
What would a low serum osmolality and a urine osmolality of greater than 100mosmol/kg (100= concentrated) and urine sodium of less than 30mmol/kg?
True dehydration e.g. GI salt loss
OR
clinically overloaded but intravascular depletion e.g. in congestive cardiac failure, cirrhosis or nephrotic syndrome
Urine sodium of <30 mmol/L suggests low effective arterial volume
What would a patient with SIADH look like biochemically (serum osmolality, urine osmolality, urine sodium and their fluid balance)
Low serum osmolality
Urine osmolality> 100mosmol/kg
Urine sodium> 30mmol/L
Euvolaemic
What is the next steps in investigation if a patient has low serum osmolality and a urine osmolality of greater than 100mosmol/kg and urine sodium of greater than 30mmol/kg?
Need to work out - are they EUVOLAEMIC or DEHYDRATED?
A patient low serum osmolality and a urine osmolality of greater than 100mosmol/kg and urine sodium of greater than 30mmol/kg and they are dehydrated, what do you need to consider?
Addison’s disease, renal or cerebral salt wasting or does the patient have a history of vomitting
What do you need to rule out before you make a diagnosis of SIADH?
Hypothyroidism - elevated ADH due to decreased Cardiac output
Total salt depletion
ACTH deficiency- check serum cortisol as low cortisol causes less -ve feedback on CRH and Cortisol directly suppresses ADH secretion )
Why does ACTH deficiency present like SIADH?
Cortisol deficiency leads to increased ADH secretion
What are the causes of SIADH?
- Pituitary tumour
- Tumours: small cell lung cancer, thymoma, lymphoma
- Pulmonary disease: infections, pneumothorax, asthma, cystic fibrosis
- CNS disease: infection (SE of meningitis/encephalitis), head injury
- Drugs: chemotherapy, psychiatric drugs (lithium = nephrogenic cause)
- Idiopathic
What malignancy is know to cause SIADH?
small cell lung cancer
How do you treat SIADH?
Fluid restriction- however in practice this is quite poorly tolerated
ADH antagonists- Tolvaptan
Demeclocycine- tetracycline antibiotic that inhibits ADH
How do you treat hyponatraemia?
Hypovolaemic hyponatraemia- normal saline
Hypervolaemic hyponatraemia- needs specialist treatment to treat the underlying cause of CCF, nephrotic syndrome or cirrhosis
What is Trousseau’s sign? What is relevance?
Due to Hypocalcaemia
When inflate BP cuff above systolic pressure. Brachial artery is occluded. Causes carpal spasm (e.g. wrist flexing and fingers abducting)