Can blood gas values predict pulmonary hypoplasia in antenatally diagnosed congenital diaphragmatic hernia?

The prognosis of antenatally diagnosed congenital diaphragmatic hernias (CDH) is clearly related to the degree of pulmonary hypoplasia (PH). After birth, controversies remain regarding the implementation of various therapies, especially the use of extracorporeal membrane oxygenation (ECMO). In the literature, the persistence of a Pao2 below 100 mm Hg and of Paco2 above 40 mm Hg despite optimal conventional therapy indicates poor prognosis. Therefore, since 1992, published and personal experiences led the authors to exclude CDH patients from ECMO when conventional therapy (including high-frequency oscillatory ventilation and nitric oxide) did not obtain Pao2 of above 80 mm Hg and Paco2 of below 60 mm Hg. The aim of this retrospective study is to determine whether blood gas results correlate with postmortem findings. Between July 1990 and July 1994, 32 cases of CDH were monitored antenatally and managed postnatally at the authors' institution. Six patients survived; 26 died, including one immediately at birth. Thirteen were treated by ECMO. Seventeen had a best Pao2 of above 80 mm Hg, including the six survivors. Fourteen did not reach this level, and none of them survived. Twenty-three infants underwent postmortem examination. PH was assessed using two criteria: (1) lung weight to body weight ratio (LW/BW) and (2) radial alveolar count (RAC). Two patients did not have hypoplasia (LW/BW > 0.018). Twenty-one patients had PH; 12 of them had an LW/BW ratio of less than .009; for 9, the LW/BW ratio was between .009 and .018, and the RAC (< 3.1) confirmed PH. All infants with a best Pao2 of less than 80 mm Hg had PH. Patients with a best Pao2 of greater than 80 mm Hg included two infants who died from complications without PH, eight infants with demonstrated PH, and the six survivors. In conclusion. (1) No infant with nonhypoplastic lungs has been deprived of ECMO by the authors' criteria. (2) Adequate values of blood gases may not eliminate PH. Therefore, this probably justifies starting ECMO when conventional therapy fails. (3) Conversely, permanent poor values of Pao2 allowed the prediction of PH in all cases. Such patients probably can be excluded from ECMO treatment.