Clinical Chemistry

Question 1

Causes/ Investigations prolonged QT

Answer 1

Electrolytes Ca, K, Mg

Question 2

ECG features of hypokalaemia

Answer 2

U waves
small or absent T waves (occasionally inversion)
prolong PR interval
ST depression
long QT

(In Hypokalaemia, U have no Pot and no T, but a long PR and a long QT)

Question 3

Hyponatraemia, hyperkalaemia and raised creatinine along with fatigue and weight loss

Answer 3

Addisons

Question 4

Biochemical/ haematological abnormalities in anorexia nervosa

Answer 4

Hypokalaemia
Hypochloraemic alkalosis (both due to vomiting and/or diuretic/laxative abuse)
Hypercholesterolaemia (mechanism unknown).

The erythrocyte sedimentation rate (ESR) is normal or reduced.
The white cell count may be low.

Question 5

Explain how urine pH can act as a promoter or inhibitor of stone formation

Answer 5

Acidic urine reduces formation of calcium stones

Acidic urine increases formation of urate stones.

Question 6

Expected biochemistry in a myeloma patient (Ca, P, PTH, urea, creatinine, albumin and total protein)

Answer 6

Elevated total protein with low albumin - abnormally high globulins

High serum calcium

Suppressed parathyroid hormone consistent with hypercalcaemia of malignancy

High phosphate - common in haematological malignancy where there is a large amount of cell turnover

Renal impairment - usually chronic kidney deterioration due to the deposition of myeloma casts in the nephrons. However, the hypercalcaemia can cause dehydration in addition to this.

Question 7

Biochemical abnormalities expected in Addison’s

Answer 7

Hyponatraemia
Hyperkalaemia
Hyperuricaemia
Hypoglycaemia

Question 8

Causes of hyperkalaemia

Answer 8

Renal failure
k+ sparing diuretics
Excess k+ therapy
Addison's disease, and
Massive blood transfusions