Lab case 28 – Interpretation

This patient has a severe hypochloraemic metabolic alkalosis,  with an additional respiratory alkalosis. There is also a severe lactic acidosis (so there must be an additional component of a metabolic acidosis present)

consistent with severe vomiting.

Severe metabolic alkalosis – pH 7.68, HCO3 65, BE 40

Expected CO2 = 65.78, actual is 55 (however venous gas – CO2 may be up to 10 mmHg higher than arterial, so confirmation needed)

Mild hyponatraemia – shifts, loss

Severe hypochloraemia – loss of HCl from stomach

Very high lactate reflecting fluid depletion and shock, secondary to severe vomiting or other causes of lactic acidosis.

Osmolality likely to be high – 274+Urea (expected to be elevated from severe dehydration)

K normal, often low with severe vomiting

In this patient you must consider gastric outlet obstruction as a cause of the vomiting in view of the severe acid base abnormality present. Is there a history of drug/ alcohol abuse, NSAID overuse.

Respiratory alkalosis may be due to hyperventilation from pain, central causes (CVA, ICH, tumour, infection), aspiration and chest infection.

He requires resuscitation and investigation of underlying causes, including drug and alcohol withdrawal (THC, oipiod), CNS (bleed, tumour, infection), sepsis

Unable to calculate A-a gradient or interpret pO2 (venous gas).