MRCP2-0700

MRCP2-0700

A middle-aged homeless man in his early 50s is brought to the emergency department with a six hour history of profuse vomiting. He complains of nausea and headache.

The history available is sketchy. He is of no fixed abode and denies having any previous medical problems. He appears unkempt and is confused – oriented to person but not time or place. He is afebrile. His breath smells of ketones.

Twelve hours after admission his condition deteriorates. He complains of blurred vision and his pupils are fixed and dilated; his respiratory rate increases sharply over the next few minutes and he becomes unconscious.

Investigations show:

Hb 138 g/L (130-180)
WCC 7.1 ×109/L (4-11)
Platelets 401 ×109/L (150-400)
Plasma sodium 135 mmol/L (137-144)
Plasma potassium 5.0 mmol/L (3.5-4.9)
Plasma urea 5.8 mmol/L (2.5-7.5)
Plasma creatinine 110 µmol/L (60-110)
Plasma chloride 100 mmol/L (95-107)
Plasma bicarbonate 12 mmol/L (20-28)
Plasma glucose 5.5 mmol/L (3.0-6.0)
Plasma lactate 4.1 mmol/L (0.6-1.7)
PaO2 12 kPa (11.3-12.6)
PaCO2 4.2 kPa (4.7-6.0)
pH 7.22 (7.36-7.44)
Urine microscopy Crystals seen

What is the calculated anion gap in this case?