Severe underweight status predicts adverse postoperative outcomes after congenital heart surgery in children

Background: Malnutrition significantly affects children with congenital heart disease (CHD). Severe underweight status may prolong postoperative recovery and increase complications after cardiac surgery. Identifying modifiable risk factors may help improve outcomes. Patients and Methods: Between January 2022 and December 2024, we included all children with a weight-for-age Z score (WAZ) <−3 who underwent palliative or corrective cardiac surgery (group 1). Demographic, laboratory, physiological, and clinical parameters were collected. Outcomes were compared with age- and risk-adjustment for congenital heart surgery-matched controls (group 2) with a normal WAZ (>−2). The severely underweight group was subdivided into two subgroups, complicated (1a) and noncomplicated (1b), to analyze potential risk factors. Results: A total of 170 children were included; 86 were severely underweight. Means WAZ and weight-for-height Z scores for group 1 were −4.4 ± 0.16 and −3.75 ± 0.43, respectively. The total complication rate was more in group (1), although it was not statistically different; cardiac and respiratory complications were higher in the severely underweight group. There were no differences in major cardiac events, unplanned interventions, or mortality. Severely underweight children had longer mechanical ventilation (MV), longer ICU and hospital stays, and more feeding difficulties. Conclusions: Severe underweight significantly increases postoperative morbidity after congenital heart surgery. Factors that elevate oxidative stress in this fragile population may further amplify surgical risk. Large-scale studies are essential to better identify and understand the contributing risk factors.