Summary

This report describes a patient with gastroparesia and frequent emesis admitted with severe metabolic alkalaemia, hyperlactataemia and acute renal failure. Metabolic alkalaemia was not only due to hypochloraemia but also due to unmeasured cations. These cations were found to be present by calculating anion gap and strong ion gap (both were negative, which is rare). After massive gastric bleeding the patient had a cardiac arrest; following cardiopulmonary resuscitation and infusion of a large volume of normal saline, new blood tests revealed improvement in chloraemia but also a significant increase in the anion gap, suggesting that unmeasured anions rapidly overcame unmeasured cations. The patient died after sequential episodes of cardiac arrest. Anion gap and strong ion gap were useful in the diagnosis of this “hidden” unusual cause of metabolic alkalosis and also in the diagnosis of metabolic acidosis after cardiac arrest, even with normal/high values of base excess and bicarbonate.