Electrolyte abnormalities

Question 1

What defines hyponatraemia?

Answer 1

serum sodium concentration of <135 mmol/L

most common electrolyte abnormality

disorder of water balance reflected by an excess of total body water relative to electrolytes

Low plasma osmolality

Question 2

What is a medical emergency associated with hyponatraemia?

Answer 2

Cerebral oedema

Question 3

What factors are at play in hyponatraemia?

Answer 3

Loss of sodium
Increase in fluid - most important
BUT hyponatraemia can happen in eu or hypovolaemic states too

Question 4

What are RFs for hyponatraemia?

Answer 4

Older age
Hospitalisation
Long term conditions e.g. DM, CHF
Medications e.g. SSRIs, Thiazide diuretics, PPIs
High fluid intake

Question 5

What are some presenting features of hyponatraemia?

Answer 5

N+V - cerebral oedema
Mild cog symptos
Orthostatic hypotension
Abnormal JVP
Reduced urine output
Oedema
Lung crackles
Abnormal JVP

Question 6

What is the management for acute onset <48 hours hyponatraemia?

Answer 6

Hypertonic 3% saline infusion
Supportive care
Treat underlying cause

Question 7

What is the management for chronic onset >48 hours hyponatraemia? hypovolaemic

Answer 7

Isotonic fluid infusion

Question 8

What is the management for chronic onset >48 hours hyponatraemia? hypervolaemic

Answer 8

Fluid restricct
Treat underlying cause
+/- loop diuretic or spironolactone

2nd line
Vasopressin receptor antagonist

Question 9

Define hypernatraemia

Answer 9

serum sodium concentration of >145 mmol/L

Question 10

What is the most common presentation of hypernatraemia?

Answer 10

patient in the intensive care unit who is unable to drink water, has a large urine or stool output, and is unable to concentrate urine normally

the older nursing home resident, usually with dementia

Question 11

What are causes of hypernatraemia?

Answer 11

dehydration
osmotic diuresis e.g. hyperosmolar non-ketotic diabetic coma
diabetes insipidus
excess IV saline

Question 12

What are they types of hypokalaemia?

Answer 12

With alkalosis

With acidosis - more associated because K+ levels rise and fewer H+ can enter cells

With/out HTN

Question 13

What causes hypokalaemia with alkalosis?

Answer 13

vomiting
thiazide and loop diuretics
Cushing’s syndrome
Conn’s syndrome (primary hyperaldosteronism)

Question 14

What causes hypokalaemia with acidosis?

Answer 14

diarrhoea
renal tubular acidosis
acetazolamide
partially treated diabetic ketoacidosis

Question 15

What are presenting features of hypokalaemia?

Answer 15

Muscle weakness
Hypotonia
Digoxin toxicity

Question 16

What are the ECG features of hypokalaemia?

Answer 16

U waves
small or absent T waves
prolonged PR interval
ST depression

Question 17

What causes hypokalaemia with hypertension?

Answer 17

Cushing’s syndrome
Conn’s syndrome (primary hyperaldosteronism)
Liddle’s syndrome
11-beta hydroxylase deficiency*

Question 18

What causes hypokalaemia without hypertension?

Answer 18

diuretics
GI loss (e.g. Diarrhoea, vomiting)
renal tubular acidosis

Question 19

What are causes of hyperkalaemia?

Answer 19

AKI
Drugs 
Metabolic acidosis
Addison's
Rhabdomylosis 
Massive blood transfusion

Question 20

What drugs can cause hyperkalaemia?

Answer 20

ACE inhibitors
angiotensin 2 receptor blockers
spironolactone
ciclosporin
heparin

Question 21

How can stages of hyperkalaemia be classified?

Answer 21

mild: 5.5 - 5.9 mmol/L
moderate: 6.0 - 6.4 mmol/L
severe: ≥ 6.5 mmol/L

Question 22

What ECG changes are seen in hyperkalaemia?

Answer 22

peaked or ‘tall-tented’ T waves
loss of P waves
broad QRS complexes
sinusoidal wave pattern

Question 23

What are the management principles for hyperkalaemia?

Answer 23

Stabilise the cardiac membrane - IV calcium gluconate

Shift K+ intracellularly - Insulin/dextrose infusion
Nebulised salbutamol

Remove K+ from body = Calcium resonium (oral or enema), Loop diuretics, dialysis

Question 24

What practically is the emergency treatment for hyperkalaemia?

Answer 24

If >6.5 mmol/L or ECG changes

IV calcium gluconate
Insulin/dextrose infusion

Question 25

What are common differentials for hypercalcaemia?

Answer 25

Primary hyperparathyroidism
Malignancy
Multiple myeloma

Question 26

What are the features of hypercalcaemia?

Answer 26

‘bones, stones, groans and psychic moans’
corneal calcification
shortened QT interval on ECG
hypertension

Question 27

What is the initial management fro hypercalcaemia?

Answer 27

Rehydration with normal saline

Bisphosphonates

Question 28

What are the features of hypocalcaemia?

Answer 28

tetany: muscle twitching, cramping and spasm
perioral paraesthesia
if chronic: depression, cataracts
ECG: prolonged QT interval

Question 29

What signs are seen in hypocalcaemia?

Answer 29

Trousseau’s

Chvostek’s

Question 30

What is Trousseau’s sign?

Answer 30

carpal spasm if the brachial artery occluded by inflating the blood pressure cuff and maintaining pressure above systolic
wrist flexion and fingers are drawn together

Question 31

What is Chvostek’s sign?

Answer 31

tapping over parotid causes facial muscles to twitch

Question 32

What causes hypocalcaemia?

Answer 32

vitamin D deficiency (osteomalacia)

chronic kidney disease

hypoparathyroidism

rhabdomyolysis

magnesium deficiency (due to end organ PTH resistance)

massive blood transfusion

acute pancreatitis

Question 33

How is severe, acute hypocalcaemia managed?

Answer 33

IV replacement (calcium gluconate) 
ECG monitoring