Biochemistry Flashcards
Sodium follows water everywhere. True/False?
False
Water follows sodium!(WafS)
Concentration of Na inside the cell is more than concentration of Na outside the cell. True/False?
False
Concn of Na outside cell is greater than inside
What does mineralocorticoid activity refer to?
Sodium retention in exchange for potassium and/or hydrogen ions
What is the main steroid in the body with mineralocorticoid activity?
Aldosterone
Excess mineralocorticoid activity causes what?
Sodium retention
What effect does sodium loss have upon water?
Sodium loss means water loss (water follows sodium!)
Outline what happens in terms of sodium and water when blood pressure drops
Decreased blood pressure causes sodium + water retention in order to compensate and bring blood pressure up
Which hormone controls water reabsorption?
ADH
What effect does ADH have on water reabsorption and thus urine output?
Causes increased water reabsorption (anti-diuresis), producing low-volume concentrated urine
Concentrated/small volume urine has a high omolality. True/False?
True
What are the main causes of decreased sodium levels?
Too much water
Too little sodium
What are the main causes of increased sodium levels?
Too little water
Too much sodium
Decreased sodium levels can be due to too much water. How can this arise?
SIADH (inappropriate ADH secretion)
Compulsive water drinking
Decreased sodium levels can be due to too little sodium. How can this arise?
Sodium loss (renal insufficiency, gut fistulae) Decreased sodium intake (rare)
Increased sodium levels can be due to too little water. How can this arise?
Water loss (diabetes insipidus) Decreased water intake
Increased sodium levels can be due to too much sodium. How can this arise?
IV medication
Drowning in sea
High-salt feeds
Outline pathogenesis of Addison’s disease
Adrenal insufficiency;can’t make enough aldosterone;can’t retain enough sodium;lose sodium + water;low ECF volume, so patient is dehydrated + dizzy
What is the main osmotic stimulus for ADH release?
High sodium (high osmolality) causes increased ADH
Does hypovolaemia cause increased or decreased ADH release?
Increased ADH release (to compensate for loss of fluid)
Outline the main treatment for too much sodium
Loop diuretic
Outline the treatment for SIADH
Fluid restrict to 0.5l
Sodium should rise
Outline the treatment for diabetes insipidus
Desmopressin (synthetic ADH)
Outline the treatment for too little sodium
Sodium supplement
List features of Addison’s disease
Skin pigmentation (high ACTH) Dizziness Low BP Hyponatraemia Hyperkalaemia
State the diagnostic test for adrenal insufficiency
Short synacthen test
What are the two types of adrenal insufficiency?
Primary e.g. Addison’s
Secondary e.g. long-term use of CCS
List ECG changes found in hyperkalaemia
Tall tented T waves
Broad QRS
Give symptoms of hyperkalaemia
Muscle weakness
Paraesthesia
List causes of hyperkalaemia
Reduced excretion (renal failure, hypoaldosteronism) Redistribution (metabolic acidosis, rhabdomyolysis, insulin deficiency) Increased intake (potassium salts)
List treatment options for hyperkalaemia
Calcium gluconate
Insulin
50% dextrose
Dialysis
What is pseudohyperkalaemia?
Increase in concentration of potassium due to its movement out of cells in a haemolysed blood sample
List symptoms of hypercalcaemia
Confusion Abdominal pain Renal stones Polyuria, polydipsia Constipation
List the common causes of hypercalcaemia
Primary hyperparathyroidism
Hypercalcaemia of malignancy
Thiazide diuretic therapy
Sarcoidosis
Outline treatment for hypercalcaemia
IV fluids
Biphosphonates
Treat cause e.g. surgery
What is familial benign hypercalcaemia?
High calcium is sensed by the parathyroid as normal, therefore the patient has normal PTH and high calcium
By what mechanisms, does the kidney regulate blood volume?
Renal excretion of sodium
Renal excretion of water
via RAAS system
List ways in which hyponatraemia is assessed
Serum sodium (plasma osmolality) Urine sodium (volume status)
How do you distinguish between hyponatraemia and pseudohyponatraemia?
Measure serum osmolality (normal in pseudo)
How do you distinguish between central and nephrogenic diabetes insipidus?
DDAVP, synthetic analogue of ADH
Central is due to a lack of ADH
Nephrogenic is due to reduced response to ADH
What type of lung cancer is most associated with the production of ADH?
Small cell carcinoma
What type of lung cancer is most associated with hypercalcaemia?
Squamous cell carcinoma
Patients with adrenal insufficiency are less able to retain infused saline (sodium) than normal subjects. True/ False?
True
Addison’s patients are unable to hold onto sodium
How do you distinguish between primary and secondary adrenal insufficiency?
Measure ACTH
Reduced in secondary insufficiency
List the role of PTH
Bone resorption (increase calcium)
Activate vitamin D in kidneys (increase calcium)
Increase GI calcium absorption
Why is rehydration so important in hypercalcaemia patients?
It interferes with proximal tubular reabsorption of sodium and so causes loss of sodium and water patients are usually dehydrated
List drugs that are at risk of causing hyperkalaemia
Potassium-sparing diuretics (eg, spironolactone)
NSAIDs
ACE inhibitors.
Angiotensin-receptor blockers (ARBs)
Give two side effects of rhabdomyolysis
Acute renal failure
Disseminated intravascular coagulation
What gross findings suggest contamination with potassium EDTA, the anticoagulant used in the purple top (FBC) bottle?
Gross hypocalcaemia
Gross hyperkalaemia
What is meant by a high vs low urine osmolality?
High = concentrated urine Low = dilute urine
How do you test for secondary adrenal insufficiency?
Short synacthen test
It would show a suppressed ACTH
