Impact of ketogenesis and strong ion difference on acid-base in our CICU.

Persistence of a mild metabolic acidosis or base deficit was occasionally observed in our otherwise well patients post cardiac surgery, sometimes delaying discharge. We hypothesised that this metabolic abnormality may be due to either ketogenesis caused by a combination of starvation and the surgical stress response, or strong ion imbalances following fluid administration. The administration of large volumes of chloride-rich fluids (as may occur during cardiac surgery to prime the cardiopulmonary bypass circuit or resuscitate the patient) is known to induce hyperchloraemic metabolic acidosis [1]. Using simplifications of the original Fencl-Stewart's equations, it is possible to partition the base deficit into its constituent parts, subsequently determining the relative contribution of chloride, albumin and unmeasured anions to acidosis [2,3]. Ketone production may contribute significantly to the unmeasured anion component.