Management of Newborn with MAS Presenting with Hypoxia and Respiratory Distress
Begin with supplemental oxygen and non-invasive positive pressure ventilation (NIVPP), reserving intubation and mechanical ventilation for infants who fail to respond to initial measures or develop persistent bradycardia. 1, 2
Initial Resuscitation Approach
Start resuscitation with room air (21% oxygen) for term infants rather than 100% oxygen, as this approach reduces mortality without compromising outcomes 1
Apply pulse oximetry to the right upper extremity (preductal site) within 1-2 minutes of birth to guide oxygen titration 1
Titrate supplemental oxygen to achieve preductal oxygen saturations that approximate healthy term infant values: 70-80% in the first few minutes, gradually rising to >90% by 10 minutes 1, 3
Do NOT perform routine tracheal intubation and suctioning for nonvigorous infants born through meconium-stained amniotic fluid, as this practice delays ventilation without improving outcomes 1, 2
Respiratory Support Strategy
Initiate positive pressure ventilation promptly if the infant has inadequate respiratory effort, as the emphasis should be on establishing ventilation within the first minute of life 1, 2
Consider using positive end-expiratory pressure (PEEP) during ventilation to assist in establishing functional residual capacity, which can be delivered via self-inflating bag, flow-inflating bag, or T-piece 1
Reserve intubation for specific indications: evidence of airway obstruction from meconium plug, failure to respond to bag-mask ventilation, or persistent bradycardia despite adequate ventilation attempts 1, 2
If attempted intubation is prolonged and unsuccessful, immediately return to bag-mask ventilation, particularly when bradycardia persists 1
Escalation of Respiratory Support
Approximately 30-50% of infants with MAS will require continuous positive airway pressure (CPAP) or mechanical ventilation 4
For infants requiring mechanical ventilation, high ventilator pressures, relatively long inspiratory times, and slow ventilator rates may be necessary to achieve adequate oxygenation 5
Consider high-frequency ventilation for infants with refractory hypoxemia and/or gas trapping who fail conventional ventilation 5, 6
Management of Pulmonary Hypertension
Recognize that pulmonary hypertension is a critical complication of MAS requiring prompt identification and treatment 6, 7
Inhaled nitric oxide (20 ppm) is indicated for term and near-term infants with hypoxic respiratory failure and pulmonary hypertension associated with MAS, as it significantly reduces the need for ECMO (39% vs 55%, p=0.014) 8
In clinical trials of MAS with hypoxic respiratory failure, inhaled nitric oxide reduced the combined endpoint of death or ECMO from 64% to 46% (p=0.006) 8
Monitor methemoglobin levels when using inhaled nitric oxide, as levels can increase during the first 8 hours of exposure, though they typically remain below 1% at the recommended 20 ppm dose 8
Adjunctive Therapies
Consider surfactant administration in selected cases, as it has been shown to improve gas exchange, resolve pulmonary hypertension, and decrease oxygenation index 6
Maintain normothermia throughout resuscitation and stabilization, as hypothermia increases oxygen consumption and mortality risk 2, 3
Critical Pitfalls to Avoid
Do not delay positive pressure ventilation to perform tracheal suctioning, as the insufficient evidence for benefit does not justify the harm of delayed ventilation 1, 2
Avoid routine suctioning with bulb syringe unless secretions are visibly obstructing the airway, as unnecessary suctioning can induce bradycardia 1
Do not start with 100% oxygen, as room air resuscitation has demonstrated superior outcomes in term infants 1
Be aware that infants with MAS undergoing therapeutic hypothermia for concurrent HIE may develop worsened pulmonary hypertension due to increased pulmonary vascular resistance, requiring especially close hemodynamic monitoring 7