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Endocrinology > Ion imbalances > Flashcards

Ion imbalances Flashcards

1
Q

What does SIADH stand for?

A

Syndrome of inappropriate ADH secretion

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2
Q

What is SIADH?

A

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

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3
Q

When is vasopressin secreted in healthy people?

What does it do?
Where does it act?

A

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

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4
Q

Causes of SIADH?

A

Brain damage: meningitis, SAH

Malignancy: small-cell lung cancer

Drugs: carbemazepine, SSRIs, amitriptyline

Infectious: atypical pneumonia, lung abscess, cerebral abscess

Hypothyroid

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5
Q

Clinical features of SIADH?

A

Nausea, headache, irritability

Hyponatraemia caused by the increased amount of water
(Na conc doesn’t change, but water conc increases)

Concentrated urine

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6
Q

What can hyponatraemia cause?

A

Fits and coma

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7
Q

Investigation of SIADH?

A

Blood:

  • low serum Na
  • low plasma osmolality

Urine:

  • concentrated
  • contains a lot of Na

MRI: to check state of hypothalamus and pituitary

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8
Q

Treatment of SIADH?

A

Restrict water intake
Treat underlying cause

Demeclocycline: drug that inhibits action of vasopressin at kidney

Vasopressin antagonist: tolvaptan

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9
Q

Causes of hyponatraemia?

A

Low sodium

SIADH
Sodium deficiency
Renal failure
Malignancy
Addison's
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10
Q

What is a detrimental impact that hyponatraemia can have on the brain?

A

Osmotic demyelination

Which can cause irreversible brain dysfunction

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11
Q

Clinical features of hypercalcaemia?

A 
Asymptomatic
Bones: pain
Stones: renal calculi
Abdo groans: constipation, pain
Psychic moans: depression, fatigue
Thrones: polyuria
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12
Q

Causes of hypercalcaemia?

A

Hyperparathyroidism

Bone metastases

Dehydration: loss of water, and no change in Ca conc will cause hypercalcaemia

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13
Q

Investigation of hypercalcaemia?

A

Raised calcium in blood

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14
Q

Management of hypercalcaemia?

A

Treat the cause

Rehydrate with IV saline

Loop diuretics, not thiazide
Removal of parathyroid to treat hyperparathyroidism

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15
Q

Clinical features of hypocalcaemia?

A

Increased excitability of nervous system: muscle twitching, spasms, seizures

Numbness around the mouth, extremities, cramps

Can cause death if extreme and untreated

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16
Q

Causes of hypocalcaemia?

A

Renal failure and CKD

Parathyroid deficiency

Insufficient vitamin D

17
Q

Investigation of hypocalcaemia?

A

Blood: low calcium

eGFR to check for CKD

18
Q

Treatment of hypocalcaemia?

A

Treat the cause

Give calcium gluconate

19
Q

What calcium imbalance is caused by:

Hyperparathyroidism
Hypoparathyroidism?

A

HYPER = HYPERcalcaemia

HYPO = HYPOcalcaemia

20
Q

Clinical features of hyperkalaemia?

A

Asymptomatic until it can cause arrhythmias and MI

Impaired neuromuscular transmission: weakness and paralysis

Can cause death due to heart problems

21
Q

Causes of hyperkalaemia?

A

Renal problems

Metabolic acidosis
Adrenal insufficiency
Drugs: K sparing diuretics

22
Q

Investigation of hyperkalaemia?

A

Bloods: check potassium

ECG: peaked T waves, prolonged PR, widened QRS and reduced P

23
Q

Treatment of hyperkalaemia?

A

IV fluid bolus
Calcium gluconate to protect the heart
10u insulin + IV dextrose
Salbutamol

24
Q

Clinical features of hypokalaemia?

A

Asymptomatic usually

Muscle weakness
Cardiac arrhythmias and sudden death

Polyuria

25
Q

Causes of hypokalaemia?

A

Diuretic therapy causing excessive loss of K in kidneys

Hyperaldosteronism: increased loss of K in kidneys

GI fluid loss: vomiting and diarrhoea

26
Q

Investigations of hypokalaemia?

A

Blood: low potassium

ECG: flat T waves, ST depression, prominent U waves

27
Q

Treatment of hypokalaemia?

A

Treat underlying cause

Withdraw harmful diuretic medication

SandoK

28
Q

Describe the ECG abnormalities you’d see in hyper and hypokalaemia?

A

Hyper:

  • peaked T waves
  • prolonged PR
  • widened QRS

Hypo:

  • flat T waves
  • ST depression
  • prominent U waves
29
Q

Where are K+ ions usually found?

A

Inside cells

30
Q

By what route are K+ ions removed from the body?

A

Urine

31
Q

Where is calcium stored in the body?

A

Bone

32
Q

What is the role of parathyroid hormone in calcium levels?

A

PTH raises blood calcium levels!

Stimulates release of Ca2+ from bone into the blood stream

It also reduces loss of Ca2+ in urine and increases absorption of Ca2+ into intestine

33
Q

Why does bone cancer cause hypercalcaemia?

A

Bone malignancy causes breakdown of bone which releases Ca2+ into the blood when no more Ca2+ is needed

Resulting in hypercalcaemia

34
Q

Why does renal failure cause hyperkalaemia?

A

Renal failure causes impaired filtration in the nephrons

Usually, K+ is absorbed from the blood into the nephron where it is then excreted

In renal failure this doesn’t happen so K+ remains in the blood: hyperkalaemia

35
Q

What is crush syndrome?

A

Problems that occur as a result of a crush injury, prolonged continuous pressure on muscle tissue

36
Q

What happens in crush syndrome?

A

Crush causes:

Ischaemia-reperfusion
Hyperkalaemia
Hypovolaemic shock

37
Q

What is ischaemia-reperfusion injury?

A

When pressure is released from crushed muscle, blood can return to the vessels

The tissue is once again perfused with oxygen after a period of anoxia

Causes damage to the tissue

38
Q

Why does crush injury cause hyperkalaemia?

A

When muscle cells are injured potassium (which is stored in the muscle cells) escapes and leaks into bloodstream

High levels of K

Endocrinology (19 decks)

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