"Benign" lactic acidosis is common in adolescents and children following congenital heart surgery

Lactic acidosis is commonly observed in children following congenital heart surgery. Serum lactate is a surrogate measure of cardiac output and tissue oxygen delivery. Children and adolescents frequently have elevated lactate levels postoperatively without clinical signs of low cardiac output. Our objective was to evaluate children with postoperative lactic acidosis and to describe a distinct group of patients with lactic acidosis and low inotropic scores we named "benign" lactic acidosis. We conducted a retrospective chart review of 105 patients, 5 to 21 years old, who had undergone open-heart surgery from 05/2011 to 05/2013. Based on highest postoperative lactate levels ( > 4.4 mmol/L or 40 mg/dl) and inotrope scores (>= 15) in the first 48 postoperative hours we defined three groups: classic lactic acidosis (elevated lactate and inotrope score, n = 9), benign lactic acidosis (elevated lactate and low inotrope score, n = 25) and a control group (low lactate and low inotrope score, n = 71). Lactic acidosis in the benign group was less pronounced and resolved earlier than in the classic group. The classic and benign groups had significantly elevated serum glucose. The classic group had significantly longer cardiopulmonary bypass time, time to extubation and hospital length of stay compared to the benign and control groups. The classic group had significantly lower systolic blood pressure, higher heart rate and central venous pressure, and lower urine output than the benign and control groups. Benign lactic acidosis is clinically distinct from classic lactic acidosis. It has faster resolution and patients exhibit stable postoperative hemodynamics with similar clinical outcomes as patients in the control group.