Inhaled nitric oxide reduces the intrapulmonary shunt to ameliorate severe hypoxemia after acute type A aortic dissection surgery.

Abstract Background To assess the relationship between the intrapulmonary shunt and PaO2/FiO2 in severe hypoxemic patients after acute type A aortic dissection (ATAAD) surgery and to evaluate the effect of inhaled nitric oxide (iNO) on intrapulmonary shunt. Methods Postoperative ATAAD patients with PaO2/FiO2 ≤ 150 mmHg were enrolled. Intrapulmonary shunt was calculated from oxygen content of different sites (artery [CaO2], mixed venous [CvO2], and alveolar capillary [CcO2]) using the Fick equation, where intrapulmonary shunt = (CcO2-CaO2)/(CcO2-CvO2). Related variables were measured at baseline (positive end expiratory pressure [PEEP] 5 cm H2O), 30 min after increasing PEEP (PEEP 10 cm H2O), 30 min after 5 ppm iNO therapy (PEEP 10 cm H2O + iNO), and 30 min after decreasing PEEP (PEEP 5 cm H2O + iNO). Results A total of 20 patients were enrolled between April 2019 and December 2019. Intrapulmonary shunt and PaO2/FiO2 were correlated in severe hypoxemic, postoperative ATAAD patients (adjusted R2 = 0.467, p Conclusions This study showed that intrapulmonary shunt and PaO2/FiO2 were correlated in severe hypoxemic, postoperative ATAAD patients. Furthermore, iNO, rather than increasing PEEP, significantly decreased the intrapulmonary shunt to improve severe hypoxemic conditions.