Nitric oxide is a molecule normally made by vascular endothelial cells to decrease vascular resistance in both the systemic and pulmonary circulations. Inhaled nitric oxide (iNO) is an (expensive) pulmonary dilator I frequently use in the OR and ICU settings for patients with acute right heart failure, refractory hypoxemia, pulmonary hypertension with superimposed lung pathology (ie, ARDS), cardiac/lung transplantation, and sometimes following mitral valve surgery. My colleagues in other disciplines use iNO to test pulmonary reactivity during right heart catheterizations and as a therapeutic option in persistent pulmonary hypertension of the newborn (PPHN).
iNO only reaches alveolar units which are well ventilated to dilate the associated pulmonary arterioles/capillaries improving V/Q matching. Since iNO is also short acting, I usually don’t worry about systemic side effects although platelet dysfunction, methemoglobinemia, and rebound pulmonary hypertension after withdrawal of iNO are possibilities.
A mixture of oxygen and iNO (on the order of parts per million concentration) are delivered through nasal prongs to spontaneously breathing patients or via an endotracheal tube in those on mechanical ventilation. Thank you to the respiratory therapists for dragging these tanks around!
Does your institution use iNO? Drop me a comment below with questions! 🙂