Persistent pulmonary hypertension of the newborn

SAQ 1 (10 marks)

A term male infant (birth weight 3.4 kg) born by emergency Caesarean section for fetal distress develops cyanosis and respiratory distress at 2 hours of life. Pre-ductal SpO₂ is 88% on 80% FiO₂; post-ductal SpO₂ is 72%. Chest X-ray shows clear lung fields with a normal heart size. ^[1]

a) What is the most likely diagnosis and what bedside finding supports it? (2 marks) — The pre–post ductal SpO₂ gradient of 16% (88% versus 72%) in the setting of refractory hypoxaemia with clear chest X-ray strongly suggests persistent pulmonary hypertension of the newborn (PPHN). The right-to-left ductal shunt produces the differential cyanosis. ^[1]

b) List four risk factors for this condition. (2 marks) — Risk factors include emergency Caesarean delivery without labour, perinatal asphyxia (fetal distress was noted antenatally), late-preterm or early-term gestation, and meconium aspiration, neonatal sepsis, or maternal SSRI use. ^[1]

c) What investigation is essential before starting inhaled nitric oxide, and why? (2 marks) — An echocardiogram is mandatory before iNO to exclude cyanotic congenital heart disease — particularly duct-dependent lesions where reducing PVR can steal systemic output through the ductus and precipitate cardiovascular collapse. The echo also confirms PPHN by estimating pulmonary artery pressure and visualising shunting. ^[4]

d) Outline your stepwise management of this infant. (4 marks) — First, optimise lung inflation and oxygenation with FiO₂ titrated to pre-ductal SpO₂ at or above 85% and gentle ventilation with permissive hypercapnia targeting pH 7.35–7.50. Second, correct metabolic derangements including glucose, calcium, temperature, and treat acidosis. Third, support systemic blood pressure with inotropes or vasopressors to keep mean BP above gestational age in weeks. Fourth, start inhaled nitric oxide at 20 ppm if OI exceeds 15 or SpO₂ remains below 85%, and refer for ECMO if OI exceeds 25–40 despite maximal therapy. ^[5]