Prevention during parturition
As previously mentioned, oropharyngeal and nasopharyngeal suctioning is not an ideal preventative treatment for both vigorous and depressed (not breathing) infants. Treatment
Most infants born through MSAF do not require any treatments (other than routine postnatal care) as they show no signs of respiratory distress, as only approximately 5% of infants born through MSAF develop MAS. However, infants which do develop MAS need to be admitted to a neonatal unit where they will be closely observed and provided any treatments needed. Observations include monitoring heart rate, respiratory rate, oxygen saturation and blood glucose (to detect worsening respiratory acidosis or the development of hypoglycemia). In general, treatment of MAS is more supportive in nature. Assisted ventilation techniques
To clear the airways of meconium, tracheal suctioning can be used however, the efficacy of this method is in question and it can cause harm.In cases of MAS, there is a need for supplemental oxygen for at least 12 hours in order to maintain oxygen saturation of haemoglobin at 92% or more. The severity of respiratory distress can vary significantly between newborns with MAS, as some require minimal or no supplemental oxygen requirement and, in severe cases, mechanical ventilation may be needed. The desired oxygen saturation is between 90 and 95% and PaO2 may be as high as 90mmHg. In cases where there is thick meconium deep within the lungs, mechanical ventilation may be required. In extreme cases, extracorporeal membrane oxygenation (ECMO) may be utilised in infants who fail to respond to ventilation therapy.
Therefore, non-selective and selective inhibitors of PDE could potentially be used in MAS therapy. However, the use of PDE inhibitors can cause cardiovascular side effects. Non-selective PDE inhibitors, such as methylxanthines, increase concentrations of cAMP and cGMP in the cells leading to bronchodilation and vasodilation. Additionally, methylxanthines decreases the concentrations of calcium, acetylcholine and monoamines, this controls the release of various mediators of inflammation and bronchoconstriction, including prostaglandins. Selective PDE inhibitors target one subtype of phosphodiesterase and in MAS the activities of PDE-3, PDE-4, PDE-5 and PDE-7 may become enhanced. For example, Milrinone (a selective PDE3 inhibitor) improved oxygenation and survival of neonates with MAS. Inhibitors of cyclooxygenase
Arachidonic acid is metabolised, via cyclooxygenase (COX) and lipoxygenase, to various substances including prostaglandins and leukotrienes, which exhibit potent pro-inflammatory and vasoactive effects. By inhibiting COX, and more specifically COX-2, (either through selective or non-selective drugs) inflammation and oedema can be reduced. However, COX inhibitors may induce peptic ulcers and cause hyperkalemia and hypernatremia. Additionally, COX inhibitors have not shown any great response in the treatment of MAS. Antibiotics
Meconium is typically sterile however, it can contain various cultures of bacteria so appropriate antibiotics may need to be prescribed. Surfactant treatment
Lung lavage with diluted surfactant is a new treatment with potentially beneficial results depending on how early it is administered in newborns with MAS. This treatment shows promise as it has a significant effect on air leaks, pneumothorax, the need for ECMO and death. Early intervention and using it on newborns with mild MAS is more effective.