Copeptin as a marker of relative arginine vasopressin deficiency after pediatric cardiac surgery

Relative arginine vasopressin (AVP) deficiency after pediatric cardiac surgery has recently been described. Copeptin, a more stable and easily measured product of pro-AVP processing, may be a means of identifying these patients. We aimed to determine if copeptin was correlated with AVP in these children and whether it can be a surrogate marker of relative AVP deficiency. Patients < 6 years of age with basic Aristotle scores a parts per thousand yen7 requiring surgery with cardiopulmonary bypass were prospectively enrolled. Plasma AVP and copeptin concentrations were measured pre-cardiopulmonary bypass and 4 and 24 h post-cardiopulmonary bypass. Relative AVP deficiency was defined a priori based on our previous work as AVP < 9.2 pg/ml at 4 h post-cardiopulmonary bypass. Of 41 children enrolled, relative AVP deficiency was present in 13 (32 %). AVP and copeptin concentrations were significantly lower in these 13 children at 4 h post-cardiopulmonary bypass as compared to the other 28 patients. A significant positive association between plasma AVP and copeptin concentrations over time was determined. Based on log-transformed analyses, a 1 % increase in plasma AVP led to a 0.19 % increase in copeptin. Further, copeptin < 1.12 ng/ml at 4 h post-cardiopulmonary bypass had a sensitivity of 92 % and a negative predictive value of 95 % for relative AVP deficiency. Plasma AVP and copeptin are positively associated in children undergoing cardiac surgery. Copeptin may represent a useful means of identifying relative AVP deficiency in these patients.