Chemical Pathology Flashcards
What are the causes of hypokalaemia?
GRRR
(GI losses - diarrhoea, vomiting, fluids)
R - Renal losses - MR excess (Hyperaldosteronism/Conn’s, Cushing’s)
Increased Na delivery to the DCT
Osmotic diuresis
Redistribution into cells
- Insulin/insulinoma
-Beta agonists
Alkalosis - Shift of potassium ions into cells in exchange for hydrogen ions
Rare causes
-RTA T1, T2
-Hypomagnesaemia
Renal potassium losses
- Triple = loop diuretics - furosemide
-Cotransporter = Thiazides
Which drugs result in hypokalaemia (through renal losses)
Loop diuretics
Thiaizdes
How does furosemide and thiazides cause hypokalaemia?
Block triple or co-transporters - resulting in a reduction in sodium reabsorption in the ascending LoH
More Na+ reaches the DCT - and is absorbed - resulting in K+ loss down the electrochemical gradient through ROMK channels
What endocrine conditions are associated with hypokalaemia?
Hyperaldosteronism/Conn’s
Cushing’s
How does hypokalaemia cause metabolic alkalosis?
Hydrogen ions shift into cells in exchange for potassium (H+/K+ anti-transporter)
-Increased excretion of hydrogen ions in exchange for sodium
-Acid urine + generation of bicarbonate
What are multinucleated giant cells on histology?
Overactive osteoclasts
What hand radiograph changes are most commonly observed in primary hyperaldosteronism?
Radial aspect cystic changes
What CXR findings are observed in sarcoidosis?
Bilateral lymphadenopathy
What Ca and PTH levels are observed in sarcoidosis?
PTH is suppressed to undetectable levels and calcium is raised >(2.2-2.6)
What is the management of sarcodosis?
Steroids - to normalise calcium and management pulmonary symptoms
What is the pathogenesis of sarcoidosis?
Macrophages express 1-alpha hydroxylase
What is the emergency management for hypercalcaemia?
IV access and rehydrate with 0.9% saline (1L over 1 hour)
Once IV 0.9% saline has been administered what is the second line management for hypercalcaemia?
Bisphosphonates
