No abstract

These data suggest that iNO increased plasma ET-1 levels, which subsequently decreased when iNO was discontinued. Increased circulating ET-1 levels might contribute to rebound pulmonary hypertension upon iNO withdrawal.

No abstract

Background —Hemodynamic stability after Norwood palliation often requires manipulation of pulmonary vascular resistance to alter the pulmonary-to-systemic blood flow ratio (Q̇p:Q̇s). Q̇p:Q̇s is often estimated from arterial saturation (Sa o 2 ), a practice based on 2 untested assumptions: constant systemic arteriovenous O 2 difference and normal pulmonary venous saturation. Methods and Results —In 12 patients early (≤3 days) after Norwood palliation, simultaneous arterial, superior vena caval (Ssvc o 2 ), and pulmonary venous (Spv o 2 ) oximetry was used to test whether Sa o 2 accurately predicts Q̇p:Q̇s. Stepwise multiple regression assessed the contributions of Sa o 2 , Ssvc o 2 , and Spv o 2 to Q̇p:Q̇s determination. Sa o 2 correlated weakly with Q̇p:Q̇s ( R 2 =0.08, P <0.05). Inclusion of Ssvc o 2 and Spv o 2 improved Q̇p:Q̇s prediction accuracy. Pulmonary venous desaturation (Spv o 2 <95%) was observed frequently (30%), especially at Fi o 2 ≤0.21, but normalized with higher Fi o 2 or PEEP in all patients. In 6 patients, Fi o 2 was increased incrementally from 0.17 to 0.50 to determine whether this was an effective means to manipulate Q̇p:Q̇s. Q̇p:Q̇s failed to change predictably with increased Fi o 2 . In 5 of 6 patients, however, higher Spv o 2 and Sa o 2 enhanced systemic oxygen delivery, as demonstrated by improvement in oxygen extraction. Conclusions —Sa o 2 correlated poorly with Q̇p:Q̇s because of variability in Ssvc o 2 and Spv o 2 . A novel observation was that pulmonary venous desaturation occurred frequently early after Norwood palliation but normalized with higher Fi o 2 or PEEP. Because unrecognized pulmonary venous desaturation confounds Q̇p:Q̇s assessment and compromises Sa o 2 and oxygen delivery, judicious use of inspired oxygen and PEEP may be beneficial in selected patients early after Norwood palliation.