A 78-year-old diabetic lady presents with reduced conscious level and confusion that has been insidious of onset over the past week. Her diabetes is normally controlled with metformin 500 mg bd. She has recently been treated for a urinary tract infection by her GP and her relatives state that she has been very thirsty. She has vomited several times today. Her urine dipstick reveals a trace of leucocytes and 2+ ketones. Her arterial blood gas results are as follows:

 

pH: 7.29

pO₂: 11.1 kPa

pCO₂: 4.6 kPa

HCO₃-: 22 mmol/l

Na⁺: 154 mmol/l

K⁺: 3.2 mmol/l

Cl^-: 100 mmol/l

Urea: 17.6 mmol/l

Glucose: 32 mmol/l