Sun28November0333PM 3

A 65-year-old male is admitted after being found by the police collapsed in the centre of town. He is a known alcoholic and is dishevelled and dirty.

Examination reveals a confused male with a Glasgow coma scale of 13, a temperature of 37°C, a pulse of 110 bpm regular and a blood pressure of 138/96 mmHg with oxygen saturations of 98%. There are no specific abnormalities on examination, with normal reflexes, tone and down going plantars. He has a respiratory rate of 30 per minute.

Investigations show:

Haemoglobin 115 g/L (130-180)

MCV 102 fL (80-96)

White cell count 8.2 ×109/L (4-11)

Platelets 150 ×109/L (150-400)

Serum sodium 136 mmol/L (137-144)

Serum potassium 3.6 mmol/L (3.5-4.9)

Serum urea 7.0 mmol/L (2.5-7.5)

Serum creatinine 120 µmol/L (60-110)

Plasma glucose 5.2 mmol/L (3.0-6.0)

Arterial blood gas analysis shows:

pH 7.24 (7.36-7.44)

pO2 14.7 kPa / 110 mmHg (11.3-12.6)

pCO2 4.0 kPa / 30 mmHg (4.7-6.0)

Standard HCO3 17 mmol/L (20-28)

Which investigation is most likely to assist with a diagnosis?

(Please select 1 option)

Benzodiazepine concentration

Vitamin B12 levels

Methanol concentration Correct

Ammonia concentration

Salicylate concentration

Explanation

This patient has a metabolic acidosis and reduced conscious level that exceeds the metabolic derangement.

His alcohol history and appearance suggests consumption of methanol which is a weak acid and would account for this clinical picture and the biochemical abnormalities.

Salicylate overdose is another possibility but less likely.

Benzodiazepines would be expected to cause respiratory depression and respiratory acidosis.

His increased mean corpuscular volume (MCV) is more than likely due to his alcohol abuse and B12 concentrations would not be helpful.

This presentation is not typical of hepatic encephalopathy as flapping tremor is expected and extensor plantar responses.

Answer Statistics

1

8%

2

73%

3

12%

4

9%

Times answered: 324