Overview
The Physiology Behind the Presentation
A blue newborn does not always have a lung problem.
A blue newborn does not always have a lung problem. In this group of critical congenital heart defects, blood may be travelling in parallel circuits, failing to reach the lungs or body, mixing inadequately, or flooding the lungs while systemic flow falls. That single question—where is blood flow failing?—organizes the bedside response. d-TGA needs mixing between two separate circulations. HLHS needs the ductus arteriosus to supply systemic flow. TAPVC becomes immediately unstable when pulmonary venous return is obstructed. Truncus mixes oxygenated and deoxygenated blood and often sends too much blood to the lungs. Tricuspid atresia requires mixing and may depend on ductal flow for pulmonary circulation. The same infant can therefore be cyanotic, tachypnoeic, poorly perfused, and unable to feed, but the reason and first treatment are not identical. Read the saturation together with pulses, blood pressure, urine output, work of breathing, lactate, and acid-base status.