BCC Lam, NS Tsoi, CY Yeung

Meconium staining of the amniotic fluid is a common problem affecting 10-15% of all deliveries. The incidence of meconium-stained liquor (MSL) in Tsan Yuk Maternity Hospital based on 3270 consecutive deliveries is 13.1%. It has been variously reported that as many as 7-22% of infants born with MSL developed meconium aspiration syndrome (MAS). In a local survey of 427 infants with MSL managed by combined obstetric and paediatric suctioning of the oropharynx and trachea, 49 infants developed MAS (11.5%). Among the various perinatal factors examined, low apgar score at 5 mm, apnoea before intubation and thick MSL were identified as important perinatal risk factors for the syndrome. Our results further show that intrauterine gasping, secondary to fetal distress, places the fetus with MSL at risk for aspiration. The pathophysiology of MAS includes mechanical obstruction of airways, displacement and inactivation of alveolar surfactant and chemical pneumonitis. Most babies with MAS ran a benign course. Twelve percent required ventilatory support and 18% developed air leak complications. Persistent pulmonary hypertension of newborn (PPHN) complicating MAS is uncommon in Chinese (8%) but when occurs it can cause mortality and chronic respiratory morbidity. Recent advances in the treatment of severe MAS include high-frequency oscillatory ventilation, surfactant replacement therapy, surfactant lavage and nitric oxide therapy. MAS is also one of the most common indications for extracorporeal membrane oxygenation in newborn. We have treated five term neonates with severe MAS necessitating mechanical ventilation soon after birth with surfactant lavage. They were compared with five consecutive historic controls with comparable initial mean oxygenation index and arterial alveolar oxygen tension ratio. All five patients in the treatment group survived without sequelae. This compared favourably with only one intact sunivor, two fatalities and two sunivors with sequelae in the control group. The mean oxygenation index, mean airway pressure, FiO₂ and arterial alveolar oxygen tension ratio at 48 hours improved significantly in the lavage group. The process of administering the surfactant lavage was generally well tolerated with no air leak complication. Recent randomised control studies on surfactant replacement therapy for MAS have also shown promising results. Infants with PPHN complicating MAS have also been shown to benefit from inhaled nitric oxide therapy. Two babies referred to Queen Mary Hospital for treatment of PPHN complicating MAS were treated with inhaled nitric oxide on Day 2 and Day 3 of life. Both babies showed favourable response with improvement of oxygen index and arterial alveolar oxygen gradient. In summary, meconium aspiration remains a problem even with an aggressive combined obstetric and paediatric approach. Most of the aspiration occurs as intrauterine events. Surfactant lavage, if performed early, appears to be an effective and safe method for treatment of severe MAS. Nitric oxide therapy may also benefit patients complicated by PPHN.