Davidson JA, et al. - The researchers aimed to define the kinetics of alkaline phosphatase (AP) activity and concentration after infant cardiopulmonary bypass, including isoform-specific changes. Furthermore, they measured the association between postoperative AP activity and major postoperative cardiovascular events, organ injury/dysfunction, and postoperative support requirements. During infant cardiopulmonary bypass, AP activity decreased and could continue to decrease for 24 hours. Activity loss was secondary to decreased bone and liver 2 isoform concentrations. Early low AP activity was correlated independently with subsequent postoperative support and organ injury/dysfunction. At 72 hours, the persistence of AP activity ≤80 U/L was associated independently with increased odds of major cardiovascular events.

• The researchers performed a prospective cohort study of 120 infants ≤120 days of age undergoing cardiopulmonary bypass.
• They evaluated AP total and isoform-specific activity at 6-time points (preoperation, rewarming, 6, 24, 48, and 72 hours postoperation).
• They defined low AP activity as ≤80 U/L.
• Through 24 hours postoperation, AP concentrations and biomarkers of organ injury/dysfunction were collected.
• They defined major cardiovascular events as cardiac arrest, mechanical circulatory support, or death.

• Secondary to the decreased bone and liver 2 isoforms, AP activity loss occurred primarily during the operation (median decrease 89 U/L; P < .0001).
• Through 24 hours, activity declined in 27% of patients.
• AP activity strongly associated with serum concentration (r = 0.87-0.91; P < .0001).
• At 72 hours, persistent low AP activity was correlated independently with the occurrence of a major cardiac event (OR 5.6; P < .05).
• Early AP activity was correlated independently with the subsequent vasoactive-inotropic score (P < .001), peak lactate (P < .0001), peak creatinine (P < .0005), N-terminal pro-brain natriuretic peptide (P < .05), and intestinal fatty acid binding protein (P < .005).