Clinical chemistry

Question 1

Hypercalcaemia

Answer 1

calcium >2.65mmol/L

Question 2

Causes of hypercalcaemia

Answer 2

Primary/ tertiary hyperparathyroidism
Malignancy
Osteolytic bone lesions
Thyrotoxicosis
Sarcoidosis
Dehydration
Rhabdomyolysis
Immobilisation
Adrenal insufficiency
Pheochromocytoma

Question 3

Medication/vitamin causes of hypercalcaemia

Answer 3

High Vitamin D
High Vitamin A
Lithium
Thiazides
Theophylline toxicity

Question 4

Hypercalcemia symptoms

Answer 4

Renal stones
Pissing thones ( polyuria and thirst)
Painful bones
Abdominal moans ( constipation, cramps , anorexia, nausea)
Listless groans
Psychiatric overtones (Mood disturbance, cognitive dysfunction, confusion and coma)

Question 5

Hypercalcaemia Mx

Answer 5

Aggressive IV Fluids
Bisphosphonates
Calcitonin
Glucocorticoids In lymphoma, other granulomatous diseases or 25OHD poisoning
Calcimimetics
Cinacalcet
Parathyroidectomy
Dialysis

Question 6

Hypocalcaemia

Answer 6

serum calcium level is <2.1mmol/L

Question 7

Causes of hypocalcaemia

Answer 7

Vitamin D deficiency
Malnutrition
Increased loses
Hypoparathyroidism
Hyperphosphatemia
Increased calcitonin

Question 8

Medication causes of hypocalcaemia

Answer 8

Bisphosphonates
PPI (hypomagnesia, Mg required for PTH production/release)

Question 9

Trousseau’s sign

Answer 9

Hypocalcaemia sign
carpopedal spasm that results from ischemia, such as that induced by pressure applied to the upper arm from an in- flated sphygmomanometer cuff

Question 10

Chvostek’s

Answer 10

Hypocalcemia sign
tapping over parotid (CN7) causes facial muscles to twitch

Question 11

Hypocalcemia clinical features

Answer 11

SPASMODIC - Decreased calcium makes nerves more excitable

Spasm
Perioral paresthesia and extremity numbness
Anxiety
Seizure
Muscle tone increase
Orientation impaired
Dermatitis
Impetigo herpetiformis ( pustular psoriasis)
Chvostek’s

Question 12

Mild Hypocalcaemia Mx
>1.9mmol/L and asymptomatic

Answer 12

Oral calcium
Replace vitamin D if low
Consider phosphate binder in CKD patients
Replace magnesium if low

Question 13

Severe Hypocalcaemia Mx
<1.9mmol/L or symptomatic at any level

Answer 13

IV calcium
Ca gluconate or Ca Chloride

Question 14

Causes of hypoglycaemia

Answer 14

EXPLAIN

Exogenous drugs (typically sulfonylureas or insulin)
Pituitary insufficiency
Liver failure
Addison’s disease
Islet cell tumours (insulinomas)
Non-pancreatic neoplasms

Question 15

Hyperkalaemia

Answer 15

blood potassium level ≥ 5.5 mmol/L

Question 16

Causes of hyperkalaemia

Answer 16

Impaired excretion (i.e. renal)
Mineralocorticoid deficiency (i.e. a lack of aldosterone which would normally promote potassium secretion)
Addison’s disease
DKA
Rhabdomyolysis
Insulin deficiency
Massive haemolysis

Question 17

Medications causing hyperkalaemia

Answer 17

Medications that inhibit aldosterone/RAS (i.e. spironolactone, ACEi, NSAID)
Ketoconazole
Ciclosporin, tacrolimus
High dose trimethoprim
Heparin
Beta blockers
Digoxin

Question 18

Hyperkalaemia clinical features

Answer 18

frequently asymptomatic
Fatigue
Generalised weakness
Chest pain
Palpitations - can lead to VF

Question 19

ECG in patients with hyperkalaemia

Answer 19

Peaked or ‘tall tented’ T waves
Flattened P-waves
Prolonged PR interval
Widening of the QRS interval
AV dissociation
Sine wave pattern
Asystole/VF

Question 20

K>6.5/ECG changes Mx

Answer 20

Calcium gluconate (10ml of 10% over 10 mins)
Intravenous insulin in 25g glucose
Nebulised salbutamol 5mg

Question 21

Hypokalaemia

Answer 21

serum potassium concentration <3.5mmol/L

Question 22

Causes of abnormal losses causing hypokalaemia

Answer 22

Gut losses (e.g. diarrhoea, vomiting, ileostomy)
Renal losses( mineralocaorticoid XS,RTA, polydypisa, dialysis)
Hypomagnesamiea

Question 23

Abnormal losses Medications causes of Hypokalaemia

Answer 23

drugs (loop or thiazide diuretics)
laxatives/enemas
Corticosteroids

Question 24

Transcellular shift causes of hypokalaemia

Answer 24

Refeeding syndrome
Increased B2 stimulation eg delirium tremens
alkalosis

Question 25

Redistribution into cell/ transcellular shifts Medications causes of hypokalaemia

Answer 25

beta agonists Insulin Theophylline,caffeine decongestants

Question 26

Clinical features of hypokalaemia

Answer 26

Absent reflexes Constipation Cramps in legs Muscle Weakness Tiredness Arrythmias Heart failure

Question 27

ECG hypokalaemia

Answer 27

Increased pr interval (can cause heart blocks) , t wave inversion or small t waves and u waves , st depression severe hypokalaemia - supraventricular/ventricular ectopics, VT,VF,Torsades de pointes

Question 28

Mild hypokalameia >3 Mx

Answer 28

Oral slow release potassium chloride- SANDO K 2 tablets

Question 29

Severe hypokalaemia <3 Mx

Answer 29

IV infusion of 1L 0.9% saline containing 40mmol potassium chloride Check and correct magnesium (low magnesium causes renal potassium wasting) Continuous cardiac monitoring

Question 30

Hypernatraemia

Answer 30

>145mmol/L

Question 31

Hypernatraemia causes

Answer 31

Excess water loss Excessive hypertonic fluid Decreased thirst Hyperaldosteronism

Question 32

Hypernatraemia Mx

Answer 32

fluids (oral or IV)

Question 33

Hyponatremia

Answer 33

<135mmol/L

Question 34

Symptoms of hyponatraemia

Answer 34

Confusion Dizziness Anorexia N&V Headache Lethargy Muscle weakness and cramps look for dehydration late symptoms may include: seizures, coma, and respiratory arrest

Question 35

Causes of Pseudohyponatraemia

Answer 35

Hypertriglycidaemia(increase in serum volume) hyperparaproteinaemia in multiple myeloma

Question 36

Causes of Hypovolaemic hyponatraemia

Answer 36

Urinary Na> 20 indicates renal loss: eg Diuretic use, Osmotic diuresis, Mineralocorticoid deficiency Urinary Na< 20 indicates extra renal loss: eg burns, Sweating, Diarrhoea

Question 37

Causes of Euvolaemic hyponatraemia

Answer 37

Syndrome of inappropriate ADH release Glucocorticoid insufficiency (cortisol has an inhibitory effect on ADH)

Question 38

Causes of Hypervolaemic hyponataemia

Answer 38

Oedematous disorders: eg Renal failure, Heart failure , Liver failure

Question 39

hypotonic Hypovolaemic hyponatraemia Mx

Answer 39

IV normal saline Stop diuretic use Treat underlying cause Steroid replacement therapy for addisons

Question 40

hypotonic Euvoleamic hyponatraemia Mx

Answer 40

Fluid restriction If severe- hypertonic sodium chloride 1.8% Demeclocycline Consider vaptans

Question 41

hypotonic hypervolaemic hyponatraemia Mx

Answer 41

Fluid restriction Treat underlying cause consider loop diuretics consider vaptans Sodium restriction

Question 42

Osmotic demyelination syndrome (central pontine myelinolysis)

Answer 42

usually occur after 2 days, usually irreversible, dysarthria, dysphagia, paraparesis or quadriparesis, seizures, confusion, and coma patients are awake but are unable to move or verbally communicate, called 'Locked-in syndrome’

Question 43

For correcting Na+ too quickly:

Answer 43

Low to high - pons will die (myelinolysis) High to low - brain will blow (oedema)

Question 44

Base excess

Answer 44

This is the amount of strong acid which would need to be added or subtracted from a substance in order to return the pH to normal (7.40).

Question 45

anion gap

Answer 45

calculated by Na+ – (Cl- + HCO3-) The normal range is 10-18mmol/L

Question 46

Causes of normal anion gap metabolic acidosis include

Answer 46

diarrhoea, renal tubular acidosis, chloride excess and certain medications including acetazolamide.

Question 47

Causes of raised anion gap metabolic acidosis include

Answer 47

lactic acidosis, diabetic ketoacidosis and metformin. An increased anion gap indicates increased acid production or ingestion

Question 48

severe hypophosphataemia can lead to

Answer 48

arrythmias

Question 49

Blood markers of re-feeding syndrome include:

Answer 49

Low phosphate levels Low magnesium levels Low potassium levels Hyperglycaemia

Question 50

Furosemide therapy can cause

Answer 50

hypokalaemia, hyponatraemia, hypocalcaemia and hypomagnesaemia.

Question 51

Tumour lysis syndrome

Answer 51

hyperkalaemia, hyperphosphataemia hyperuricaemia Hypocalcaemia.