Revision Topics

Question 1

Define hypernatraemia?

Answer 1

sodium > 145mmol/L

Question 2

2 broad causes of hypernatraemia? What is it more commonly due to?

Answer 2

low water or too much sodium

Hypernatraemia is more commonly due to low water as opposed to sodium overload

Question 3

In hypernatraemia the serum osmolality is always?

Answer 3

high

Question 4

Causes of hypernatraemia?

Answer 4

dehydration
osmotic diuresis e.g. HHS in diabetes
diabetes insipidus
excess IV saline

Question 5

Most common cause of hypernatraemia in the elderly?

Answer 5

dehydration

Question 6

Presentation of hypernatraemia?

Answer 6

in diabetes insipidus there is thirst, polydipsia and polyuria
other signs include CNS dysfunction - lethargy, weakness, confusion, myoclonic jerks and seizures
signs of dehydration and hypovolaemia may be present

Question 7

Management of hypernatraemia?

Answer 7

correct with caution so not to upset brain tissue, treat any underlying disorder and treat any dehydration

Question 8

In cranial DI, nephrogenic DI and psychogenic polydipsia what is urine, serum osmolality and sodium concentration?

Answer 8

hypernatraemia
high serum osmolality
low urine osmolality

Question 9

What are some reversible causes of nephrogenic diabetes insipidus?

Answer 9

hypercalcaemia and hypokalaemia
lithium is another cause and it is usually reversible on cessation of therapy but not always

Question 10

Define hyponatraemia?

Answer 10

serum sodium < 135 mmol/L

Question 11

Overview of the causes of hyponatraemia?

Answer 11

Too little sodium:
Renal loss - addisons, diuretics, diuretic stage of renal failure
Extra renal loss - diarrhoea, vomiting, sweating, burns

Too much water:
Euvolaemic - SIADH or hypothyroid
Hypervolaemic - fluid overload in heart failure, liver failure and nephrotic syndrome

Question 12

In true hyponatraemia the serum osmolality is?

Answer 12

low

Question 13

Causes of hyponatraemia with a low urinary sodium (<20 mmol/L)?

Answer 13

Extra renal loss - diarrhoea, vomiting, sweating, burns
Hypervolaemic - fluid overload in heart failure, liver failure and nephrotic syndrome

Question 14

Causes of hyponatraemia with a high urinary sodium? (> 20 mmol/L)

Answer 14

Renal loss - addisons, diuretics, diuretic stage of renal failure
Euvolaemic - SIADH or hypothyroid

Question 15

Investigations for hyponatraemia?

Answer 15

in low sodium result first measure urine sodium, urine osmolality and plasma osmolality
if the plasma osmolality this is a pseudohyponatraemia
check then for addisions disease - are they hyperkalaemic, do a synacthen test
check their thyroid function
then look for signs of fluid overload
drug review - are they on diuretics
are there any obvious losses e.g. diarrhoea, burns

Question 16

Presentation of hyponatraemia?

Answer 16

confusion, lethargy, cognitive impairment, focal or generalised seizures
signs of hypo or hypervolaemia

Question 17

Causes of SIADH?

Answer 17

Neoplastic - ADH secretion by cancer - most commonly small cell lung cancer

Pulmonary - pneumonia, abscess, TB, aspergillosis, asthma, CF, positive pressure ventilation

CNS - abscess, meningitis, AIDs, subdural, SAH, CVA, head trauma, MS, GBS, Shy-Drager syndrome

Drugs
1. AVP analogues e.g. desmopressin, oxytocin, vasopression
2. stimulate AVP release/ action e.g. SSRIs, antipsychotics, anti-epileptics, NSAIDs, MDMA

Hereditary SIADH

Idiopathic SIADH

Question 18

Management of acute hyponatraemia?

Answer 18

acute symptomatic hyponatraemia is a medical emergency and should be corrected carefully using hypertonic saline

Question 19

What do you need to assess in non acute hyponatraemia to decide treatment?

Answer 19

volume status
hypovolaemic
euvolaemic
hypervolaemic

Question 20

Causes of hyponatraemia where the patient will be hypovolaemic?

Answer 20

addisons, diuretics, diarrhoea, vomiting, sweating, burns

Question 21

Causes of hyponatraemia where the patient is hypervolaemic?

Answer 21

fluid overload in heart failure, liver failure or nephrotic syndrome

Question 22

Causes of hyponatraemia where the patient is euvolaemic?

Answer 22

SIADH or hypothyroid

Question 23

Treatment of hypovolaemic hyponatraemia?

Answer 23

IV saline replacement

Question 24

Treatment of normovolaemic hyponatraemia (SIADH)?

Answer 24

fluid restrict 1-1.5L
Demeclocycline - old fashioned antibiotic that uncouples AQP2 from vasopressin receptor
Tolvaptan - vasopressin receptor antagonist - may be useful but can induce thirst, are expensive, have limited availability and potentially may increase sodium levels too rapidly

Question 25

Treatment of hypervolaemic hyponatraemia?

Answer 25

the underlying cause should be treated which is usually HF, AKI or liver cirrhosis, loop diuretics are often beneficial

Question 26

Explain what central pontine myelitis is and what happens?

Answer 26

this occurs if you correct low sodium levels too quickly sodium correction should be no more than 8 mmol/L per 24 hours symptoms usually occur after 2 days and are often irreversible presentation is seizures, disturbed consciousness, gait trouble, dysphagia, dysarthria, diplopia, acute tetraparesis

Question 27

Explain what pseudohyponatraemia is?

Answer 27

sodium is low but osmolality is normal (or high) physiological drop in sodium because another solute is high e.g. high glucose and urea in diabetes or high urea in renal disease

Question 28

4 causes of acute liver failure?

Answer 28

paracetamol OD alcohol viral hepatitis (usually A or B) acute fatty liver of pregnancy

Question 29

Features of acute liver failure?

Answer 29

jaundice drowsiness/ possible confusion encephalopathy coagulopathy - raised PT hypoalbuminaemia renal failure is common (hepatorenal syndrome)

Question 30

Some reasons someone with acute liver failure might be referred for transplant?

Answer 30

encephalopathy oliguria or AKI hypoglycaemia metabolic acidosis ph < 7.3 or bicarb < 18

Question 31

In paracetamol OD when do you give acetylcysteine?

Answer 31

the plasma paracetamol concentration is on or above a single treatment line joining points of 100 mg/L at 4 hours and 15 mg/L at 15 hours, regardless of risk factors of hepatotoxicity there is a staggered overdose* or there is doubt over the time of paracetamol ingestion, regardless of the plasma paracetamol concentration; or patients who present 8-24 hours after ingestion of an acute overdose of more than 150 mg/kg of paracetamol even if the plasma-paracetamol concentration is not yet available patients who present > 24 hours if they are clearly jaundiced or have hepatic tenderness, their ALT is above the upper limit of normal acetylcysteine should be continued if the paracetamol concentration or ALT remains elevated whilst seeking specialist advice

Question 32

Activated charcoal can be used within _______

Answer 32

1hr of paracetamol overdose

Question 33

What is the most prognostic factor in paracetamol overdose?

Answer 33

arterial ph

Question 34

Who has increased risk of developing hepatotoxicity following paracetamol OD?

Answer 34

enzyme inducing drugs rifampicin, phenytoin, carbamazepine malnourished patients chronic alcohol intake acute alcohol intake is not a risk factor and may actually be protective

Question 35

Risk with acetylcysteine treatment? Management of this?

Answer 35

acetylcysteine can cause a non-IgE anaphylactoid reaction (ie a reaction that looks like anaphylaxis but is not IgE mediated) this is treated by stopping the infusion and restarting at a lower rate

Question 36

Explain what carcinoid syndrome is caused by?

Answer 36

this is a syndrome caused by secretion of serotonin and bradykinin from a carcinoid/ neuroendocrine tumour (in some parts of body name carcinoid tumour is no longer used) note that not all carcinoid tumours secrete hormones - most in the lungs dont secrete anything they can secrete more hormones than just serotonin and bradykinin but carcinoid syndrome is specifically caused by secretion of these two hormones

Question 37

Explain what vitamin deficiency can be caused by carcinoid syndrome and how this presents?

Answer 37

carcinoid syndrome can cause vitamin B3 (niacin) deficiency. This is because increased serotonin production uses up the things needed for niacin production. This presents as the 3ds - dementia, diarrhoea and dermatitis.

Question 38

Predominant symptoms of carcinoid syndrome?

Answer 38

diarrhoea, SOB, flushing and itching

Question 39

NICE reccomendations for routine fluid maintenance?

Answer 39

25-30ml/kg of water 1mmol/kg/day of sodium, potassium, chloride 50-100g/day glucose Up to a maximum weight of 100kg

Question 40

NICE reccomendations for routine fluid maintenance?

Answer 40

25-30ml/kg of water 1mmol/kg/day of sodium, potassium, chloride 50-100g/day glucose Up to a maximum weight of 100kg

Question 41

Crystalloid vs colloids?

Answer 41

Colloid vs crystalloid Colloids are designed to stay in intravascular space as has bigger molecules colloid examples: starches, dextrans, gelatins; or naturally occurring, such as human albumin or fresh frozen plasma (FFP Crystalloids go across all compartments which you want in resuscitation crystalloid examples: NaCl 0.9% and Hartmanns, 5% dextrose

Question 42

What should be used for fluid resus?

Answer 42

* NICE recommends that fluid resus is best approached with a crystalloid solution rather than a colloid * Most experts would recommend a balanced crystalloid e.g. Hartmanns because excessive amounts of 0.9% sodium chloride can result in hyperchloraemic metabolic acidosis * Exception includes rhabdomyolysis (and AKI/ CKD) when 0.9% sodium chloride would be preferred initially because of the risk of hyperkalaemia

Question 43

How should you give initial fluid for resus?

Answer 43

500ml over less than 15 minutes if AKI would want to give NaCl 0.9% over Hartmanns otherwise Hartmanns is probably better

Question 44

ECG changes with hypocalcaemia?

Answer 44

prolongation of the QT interval

Question 45

ECG changes with hypercalcaemia?

Answer 45

shortening of the QT interval

Question 46

Causes of hypomagnaesemia?

Answer 46

diuretics PPIs TPN diarrhoea (acute or chronic) alcohol secondary to hypercalcaemia and hyperparathyroidism

Question 47

Presentation of hypomagnaesemia?

Answer 47

similar to features of hypocalcaemia (could then go on to actually cause hypocalcaemia as the parathyroids need magnesium)

Question 48

Is hypermagnaesmia common?

Answer 48

no much less common than hypo and severe presentations only really encountered in patients with end stage kidney disease. In healthy individuals excess intake is excreted by the kidneys.

Question 49

Management of hypomagnaesemia?

Answer 49

if < 0.4 mmol/L or tetany or arrhythmias or seizure need IV replacement if > 0.4 can give magnesium salts but should note that these cause diarrhoea

Question 50

Presentation of hypocalcaemia?

Answer 50

tetany, cramps, perioral paraesthesia, Trosseaus (BP cuff inflation causes tetany) and Chvosteks sign (tapping over facial nerve causes twitching)

Question 51

Causes of hypokalaemia?

Answer 51

hypokalaemia with alkalosis: vomiting, thiazides, and loops, cushings, conns with acidosis: diarrhoea, renal tubular acidosis, acetazolamide, partially treated DKA (insulin pushes K into cells) magnesium deficiency can also cause hypokalaemia in such cases normalising potassium level may be difficult until deficiency has been corrected

Question 52

Presentation of hypokalaemia?

Answer 52

muscle weakness, hypotonia, increased risk of digoxin toxicity

Question 53

What is important to consider about hypokalaemia?

Answer 53

it increases risk of digoxin toxicity so if someone is on a diuretic that causes hypokalaemia and on digoxin need to consider this

Question 54

ECG changes on hypokalaemia?

Answer 54

u waves, small or absent T waves, prolonged PR interval, ST depression

Question 55

What is a u wave on ECG?

Answer 55

deflection immediately following the T wave

Question 56

Causes of hyperkalaemia?

Answer 56

AKI Potassium sparing diuretics (spironolactone, eplerenone) ARBs metabolic acidosis Addisons rhabdomyolysis massive blood transfusion foods (salt substitutes, bananas etc)

Question 57

Px of hyperkalaemia?

Answer 57

weakness, paralysis, intestinal cramping

Question 58

ECG changes for hyperkalaemia?

Answer 58

tall tented t waves