Q: Why inhaled intrinsic Nitric oxide should always be weaned instead of abrupt discontinuation

Answer:  Abrupt discontinuation of inhaled NO may cause severe rebound pulmonary hypertension, an increase in intrapulmonary right-to-left shunting, and a decreased PaO2.

Exact mechanism is not known but It has been suggested that downregulation of endogenous NO synthesis and/or elevated endothelin-1 levels by inhaled NO is probably responsible for this rebound.

Slow stepwise weaning of the inhaled NO concentration is recommended.

References;

1. Rossaint R, Falke KJ, Lopez F, et al. Inhaled nitric oxide for the adult respiratory distress syndrome. N Engl J Med. 1993; 328: 399–405.

2. Black SM, Heidersbach RS, McMullan DM, et al. Inhaled nitric oxide inhibits NOS activity in lambs: potential mechanism for rebound pulmonary hypertension. Am J Physiol Heart Circ Physiol. 1999; 277: H1849–H1856.

3. McMullan DM, Bekker JM, Johengen MJ, et al. Inhaled nitric oxide-induced rebound pulmonary hypertension: role for endothelin-1. Am J Physiol Heart Circ Physiol. 2001; 280: H777–H785.