The oxygen index (OI) predicts mortality or the need for extracorporeal membrane oxygenation (ECMO) support in newborns with hypoxic respiratory failure and associated pulmonary hypertension (PH). Echocardiography (Echo) provides additional information related to the cardiac response to-and degree of--PH. We hypothesized that a score based on Echo indicators of PH and OI would be superior to OI alone in predicting death or the need for ECMO in this population.

We retrospectively reviewed the entry Echo data and OI of 235 newborns with hypoxic respiratory failure enrolled into the multi-center, randomized, Neonatal Inhaled Nitric Oxide Study. Univariate relationships between the primary outcome (death ≤ 120 days or ECMO) and the scoring of Echo data based on R>L atrial shunt, R>L ductal shunt, elevated tricuspid regurgitation (TR) velocity, septal flattening and right ventricular (RV) dysfunction were analyzed. A logistic model was developed to obtain optimal weighting of the parameters to predict the primary outcome. Predicted error rates (PER) and p-values were calculated.

R>L atrial shunt, presence of TR, TR velocity >3.5 m/s, septal flattening, presence of PDA, and presence of RV dysfunction were not predictive of primary outcome. The only univariate relationships significant to the primary outcome were R>L ductal shunt (p=0.0348) and OI (p=0.0006). The equation for the combined score predicting the primary outcome is 1/(1+exp(-0.0410 * OI - 0.6064 * PDA score)). The results are displayed below:Table Conclusion: In a heterogeneous population of newborns with hypoxic respiratory failure, initial Echo analysis does not significantly add to the prognostic ability of the OI alone.

Table 1
Full size table