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Year 3 Medicine > Electrolytes > Flashcards

Electrolytes Flashcards

1
Q

How are sodium levels controlled?

A

Aldosterone acting on DCT and CD => increased reabsorption of Na via Na/K ATPase

Natriuretic peptides inhibit reabsorption of Na

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2
Q

How does a person with hyponatraemia present?

A

Anorexia, nausea, malaise

Headache, irritability, confusion, seizures

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3
Q

What investigations are done in hyponatraemia?

A 
Serum sodium
Serum osmolality
Urine sodium 
Urine osmolality 
TFTs, 9am cortisol/synacthen test
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4
Q

What are some causes of hyponatraemia?

A

Water overload

GI loss, CCF, cirrhosis

SIADH, ACTH/glucocorticoid deficiency

Addison’s

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5
Q

How is hyponatraemia managed?

A

Asymptomatic - fluid restriction, treat underlying cause

Acute/symptomatic/dehydrated - Rehydrate with 0.9% NaCl

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6
Q

What can happen with rapid rehydration with hyponatraemia?

A

Central pontine myelinolysis

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7
Q

What is SIADH?

A

Excess release of ADH
Results in concentrated urine sodium, with hyponatraemia
No hypovolaemia, diuretic use or oedema

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8
Q

What are some causes of SIADH?

A

Malignancy - small cell lung cancer
CNS disorders - stroke, head injury
Drugs - SSRIs, opiates

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9
Q

How is SIADH managed?

A

Treat underlying cause
Fluid restriction
ADH receptor antagonists (vaptans)

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10
Q

How does a person with hypernatraemia present?

A

Lethargy, thirst, irritability

Signs of dehydration - reduced skin turgor, tachycardia, low BP, dry mucous membranes

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11
Q

What are some causes of hypernatraemia?

A

Dehydration - inadequate intake, diabetes insipidus, thirst impairment
Fluid loss - burns, vomiting, diarrhoea, diuretics
Sodium gain - IV fluids, Primary hyperaldosteronism

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12
Q

How is hypernatraemia managed?

A

Treat underlying condition, correct dehydration

IV 5% glucose
0.9% NaCl if hypovolaemic

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13
Q

What are complications of hypernatraemia?

A

Subarachnoid haemorrhage - shrinkage of brian

Quick correction can lead to cerebral oedema

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14
Q

What is diabetes insipidus?

A

Passing large volumes of dilute urine due to impaired water reabsorption
Renal - kidneys don’t respond to ADH
Cranial - reduced ADH secretion posterior pituitary

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15
Q

What are some cranial causes of diabetes insipidus?

A

Idiopathic
Genetic
Trauma

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16
Q

What are some nephrogenic causes of diabetes insipidus?

A

Inherited
CKD
Electrolyte imbalance

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17
Q

What investigations are done for diabetes insipidus?

A

Urine output >3L/day
U&E - hypernatraemia
Blood glucose - exclude DM

High serum osmolality
Low urine osmolality

Water deprivation test

18
Q

How is diabetes insipidus managed?

A

Treat underlying cause

Cranial - head MRI, check pituitary function
Desmopressin - ADH analogue

Nephrogenic - bendroflumethiazide, reduce salt intake, NSAIDs

19
Q

How are potassium levels controlled?

A

Mainly intracellular
Uptake into cells stimulated by insulin and catecholamines - via Na/K ATPase

Cation shift - fluctuation with H+

20
Q

How does a person with hypokalaemia present?

A

Mild - asymptomatic
Muscle weakness, tetany, hypotonia
Palpitations

21
Q

What ECG changes are seen in hypokalaemia?

A

Small/inverted T waves
U waves
Prolonged PR interval
Depressed ST interval

22
Q

What are some causes of hypokalaemia?

A

Loss of K - Thiazide/loop diuretics, vomiting, diarrhoea, hyperaldosteronism

Transcellular shift - alkalosis, insulin

Inadequate intake

23
Q

How is mild hypokalaemia (>2.5) managed?

A

Do ECG, repeat bloods

Oral K supplements

24
Q

How is severe hypokalaemia (>2.5) managed?

A

ECG, bloods

IV potassium

25
Q

What are complications of hypokalaemia?

A

Arrhythmias
Muscle weakness
Contributes to digoxin toxicity

26
Q

How does a person with hyperkalaemia present?

A

Weakness, fatigue
Palpitations
Chest pain
Bradycardia

27
Q

What are some causes of hyperkalaemia?

A

Renal - AKI, CKD, mineralocorticoid deficiency, drugs eg spironolactone, ACE inhibitors, ARB

Tissue damage => release of K, eg rhabdomyolysis, trauma, burns

Acidosis
Drugs - digoxin, beta blockers

28
Q

What ECG changes are seen in hyperkalaemia?

A

Wide QRS
Tall T waves
Small P waves

Sinusoidal pattern

29
Q

What is the management of hyperkalaemia?

A

ECG, check K levels again with ABG

Stabilise heart - calcium gluconate
Shift K into cells - insulin and dextrose, nebulised salbutamol
Removal of K - calcium resonium, haemodialysis

30
Q

What is the overall effect of parathyroid hormone?

A

Increase Calcium

Decrease phosphate

31
Q

What are specific actions of PTH?

A

Increase osteoclast activity
Increase reabsorption of calcium at kidney
Decrease reabsorption of phosphate in kidney
Increase hydroxylation of calcidiol => calcitriol (vitamin D) in kidney

32
Q

What is the overall effect of vitamin D/calcitriol?

A

Increase Calcium

Increase phosphate

33
Q

What are specific actions of vit D/calcitriol?

A

Increase absorption of Ca and PO4 from gut
Increased reabsorption of Ca and PO4 from kidney
Inhibition of PTH release
Increase bone turnover

34
Q

How does hypercalcaemia present?

A

Moans - depression, lethargy
Bones - pain
Stones - renal colic
Groans - abdo pain, constipation, vomiting

Inc threshold for AP => reduced neuronal activity

35
Q

What are causes of hypercalcaemia?

A

Malignancy
Primary hyperparathyroidism - adenoma
Sarcoidosis
Secondary/tertiary hyperparathyroidism - CKD

36
Q

What investigations are required in hypercalcaemia?

A

FBC, 24hr Ca urine collection, CXR, isotope bone scan

PTH levels

37
Q

How is malignancy identified as a cause of hypercalcaemia?

A

Low PTH levels - release of PTHrP

CT CAP

38
Q

How is acute hypercalcaemia managed?

A

If Ca >3.5 and symptomatic:
Correct dehydration with 0.9% saline
IV bisphosphonates => inhibition of osteoclast

Treat underlying cause eg chemo in malignancy, steroids in sarcoidosis

39
Q

How does hypocalcaemia present?

A 
Peri-oral paraesthesia 
Cramps
Chvostek's sign 
Carpopedal spasm
Laryngospasm

Dec threshold for AP => inc neuronal activity

40
Q

What are causes of hypocalcaemia?

A

CKD, hypoparathyroidism (post-thyroidectomy)

Vit D deficiency, osteomalacia
Respiratory alkalosis - panic attack => hyperventilation => low co2

41
Q

How is hypocalcaemia managed?

A

Mild - PO supplements

Severe - IV calcium gluconate

Year 3 Medicine (11 decks)

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