OXYGENATION INDEX IN PATIENTS WITH MECONIUM ASPIRATION - CONVENTIONAL AND EXTRACORPOREAL MEMBRANE-OXYGENATION THERAPY

The use of the alveolar-arterial oxygen difference P(A-a)O2 and the oxygenation index (mean airway pressure [Paw] FIO2 x 100/PaO2) have been proposed for selecting infants who will require extracorporeal membrane oxygenation (ECMO) therapy. However, the use of the oxygenation index (OI) in conjunction with Paw in an exclusive population of patients with meconium aspiration syndrome (MAS) has not been reported. Fourteen patients born in our facility and managed with conventional therapy and five infants treated with ECMO were enrolled in the study. All patients had clinical and x-ray evidence of MAS. Infants who received conventional treatment required mechanical ventilation > 48 h, FIO2 1.0, and were under the care and supervision of one neonatologist. Management was directed to minimize barotrauma by avoidance of routine hyperventilation, use of lower Paw, and sufficient expiratory time. One patient died before ECMO and 13 infants survived. Six survivors had an OI > 25 (three had an OI > 40), six had a Paw ≥ 12 cm H2O (12 to 15 cm H2O in five infants) and six patients had a P(A-a)O2 ≥ 610 torr. One surviving infant was transferred for ECMO therapy (OI 67, Paw 20 cm H2O). The five patients treated with ECMO survived (OI 48 to 92, Paw 20 to 29.5 cm H2O, P(A-a)O2 627 to 650 torr). One patient in each group developed chronic lung disease with evidence of resting tachypnea. Our findings indicate that an OI > 40 in association with a Paw ≥ 20 cm H2O may be helpful in predicting which infants with MAS need ECMO, whereas patients requiring a Paw ≤ 15 cm H2O can be managed with conventional therapy. An OI ≥ but < 40 is not associated with high mortality in these patients. The predictive value of Paw of 16 to 20 cm H2O and the duration of an OI > 40 in patients with MAS need further investigation.