Challenges in accurately assessing acute vasoreactivity in paediatric pulmonary arterial hypertension: case reports highlighting the impact of sedation on diagnostic accuracy.

Background: Initial treatment based on acute vasoreactivity test results is essential for idiopathic or hereditary pulmonary arterial hypertension. In paediatric patients who are usually examined under sedation, accurately identifying those who are positive in the acute vasoreactivity test is often difficult. Case summary: Patient 1: A 10-year-old boy was diagnosed with heritable pulmonary arterial hypertension at the age of 5 years, following symptoms of exertional dyspnoea and fatigue. During the initial right heart catheterization, his mean pulmonary artery pressure was 21 mmHg under sedation. After pulmonary hypertension-targeted therapy was initiated, symptoms improved. However, during a follow-up examination at 10 years of age, the patient was awake, causing the pulmonary artery pressure to rise from 33/10 (21) to 99/55 (70) mmHg. Nonetheless, under nitric oxide inhalation, the rise in pulmonary artery pressure was minimal, even when the patient was awake. Subsequently, he responded well to calcium channel blockers. Patient 2: A 5-year-old girl experienced syncope and exertional cyanosis. Under sedation, initial right heart catheterization showed a pulmonary artery pressure of 44/15 (27) mmHg, which increased to 82/49 (57) mmHg upon awakening and reduced to 38/12 (22) mmHg after nitric oxide inhalation. Diagnosed with idiopathic pulmonary arterial hypertension positive for the acute vasoreactivity test, she responded well to calcium channel blockers. Discussion: Acute vasoreactivity test may be potentially underestimated during sedation in paediatric patients with pulmonary arterial hypertension. Thus, evaluating pulmonary artery pressure by reducing anaesthesia depth or stimulating wakefulness can lead to an appropriate diagnosis and treatment.