Author: Thomas Mac Mahon / Editor: Fiona Mendes / Codes: ELC2, ELC8, PhP1, SLO1, SLO3Published: 09/08/2023

You are asked to review an arterial blood gas just performed on a 73-year-old woman in the resuscitation area.

She was treated by her GP in the community for a lower limb cellulitis with flucloxacillin over the preceding five days. She was referred to your ED for assessment due to increasing drowsiness. She has no recent trauma, has been abstinent from alcohol for the preceding fortnight and has not deliberately ingested any toxins or excess medication.

She has a background of hypertension, osteoarthritis, dyslipidaemia and chronic excess alcohol intake. Her medications include amlodipine, atorvastatin and regular paracetamol.

When you see her, she is apyrexial and normotensive, tachycardic (sinus, with a rate of 120bpm), tachypnoeic (23 breaths per minute), drowsy but rousable and mildly confused. She has minor resolving cellulitic changes over a small area of her left calf with an otherwise unremarkable examination.

Her white cell count and CRP are minimally elevated. Her electrolytes, renal function, lactate, serum glucose and ketones are all unremarkable (sodium 132mmol/L, potassium 3.5mmol/L and chloride 103mmol/L). Her albumin is 17g/L (normal 35-50 g/L). Her pH is 7.14, bicarbonate 18mmol/L (normal 22-30mmol/L) and PaCO2 4.5kPa (normal 4.5-6kPa).

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