Biochem

Question 1

Which test must be performed before an ABG?

Answer 1

Allen’s test; raise arm with radial+ulnar arteries occluded, then release ulnar and look for perfusion (=collateral circulation)

Question 2

How long would it take for respiratory compensation to correct pH?

Answer 2

3-6hrs for maximal response

Question 3

Time to maximum renal acid base correction?

Answer 3

3 days

Question 4

What happens to Na when HCO3- and H+ are absorbed?

Answer 4

HCO3- absorbed WITH Na, H+ absorbed in exchange for Na

Question 5

Causes of high anion gap acidosis?

Answer 5

KUSMAL
Ketoacidosis 
Uraemia 
aSpirin
Metformin 
Alcohol
Lactic acidosis

Question 6

Causes of normal anion gap acidosis?

Answer 6

Loss of HCO3-; RTA or diarrhoea

Question 7

How might you distinguish metabolic alkalosis and respiratory acidosis with normal pH?

Answer 7

Look at K+, if low probably metabolic alkalosis.

Question 8

Glucose may falsely affect Na level, how do we correct for this?

Answer 8

True Na = Na + (glucose/4)

Question 9

How can we make the diagnosis of SIADH?

Answer 9

Low serum osmolality
Urine osmo>serum
Urine Na>30 mOsm/L
Not on diuretics

Question 10

Hypertension, high Na, low K+; what is the diagnosis?

Answer 10

Conn’s Syndrome

Question 11

What are the TRUE tests of liver function?

Answer 11

Bilirubin, Albumin

Question 12

Normal adult fraction of conjugated bilirubin?

Answer 12

25-50%

Question 13

What is Gilbert’s syndrome?

Answer 13

UDP-glucoronosyl transferase deficiency

Question 14

In descending order, which sorts of liver disease increase AST/ALT the most?

Answer 14

Toxic/Ischaemic (500-10,000)
Acute viral hep (300-3,000)
alcoholic hep
chronic hep
cirrhosis
normal (<30)

Question 15

Differentials for reduced albumin?

Answer 15

Inflammation
Severe liver disease (2-3years)
Nephrotic syndrome
Haemodilution in pregnancy

Question 16

Raised ALP + Bilirubin?

Answer 16

Cholestasis

Question 17

Physiological cause of raised ALP?

Answer 17

Advanced pregnancy, patients <20y/o

Question 18

Raised ALP with normal Bilirubin and GGT?

Answer 18

Bone source - Paget’s, malignancy, Lung Ca

Question 19

Drugs which cause Cholestasis?

Answer 19

Erythromycin, oestrogen, gold, NSAIDs, benzos

Question 20

Causes of high LDH

Answer 20

ARTEFACT
liver disease, esp. EBV
Cardiac muscle injury
Malignancy
Haemolysis
Renal infarct
Rhabdo
B12 deficiency