To the Editor:—
I read with great interest the case report by Augoustides et al. 1published in the April issue of Anesthesiology. They highlight the important issue of rebound pulmonary hypertension after withdrawal of inhaled prostacyclin and make a case for the use of inhaled iloprost. They propose that inhaled iloprost may allow gradual controlled withdrawal of perioperative inhaled selective pulmonary vasodilation, probably as a result of its favorable pharmacokinetics. Hence, in their opinion it has great promise in the management of perioperative pulmonary hypertension after cardiac surgery. However, I think that if the authors had highlighted the advantages of using sildenafil, instead of iloprost, in this scenario their case report would have made a more lasting and useful contribution to the existing literature on the topic of management of rebound pulmonary hypertension.
Pulmonary hypertension remains a major complication after surgical correction of congenital and long-standing valvular heart disease. Inhaled nitric oxide has been shown to reduce, but not eliminate, potentially life-threatening episodic pulmonary hypertensive crises.2Nitric oxide increases intracellular cyclic guanosine monophosphate, resulting in smooth muscle vasodilation. Phosphodiesterase type 5 is responsible for cyclic guanosine monophosphate breakdown in lung tissue. Abrupt discontinuation of nitric oxide may be complicated by life-threatening events, and phosphodiesterase activity may play a role in this phenomenon.3Sildenafil (Viagra; Pfizer Laboratories, New York, NY), a selective and potent inhibitor of phosphodiesterase type 5, augments pulmonary vasodilation with nitric oxide and reduces the risk of pulmonary hypertensive crises in an at-risk postoperative patient.4Furthermore, it ameliorates the rebound pulmonary hypertension caused by withdrawal of inhaled pulmonary vasodilators.5
Compared with the standard treatment, inhaled nitric oxide, sildenafil is superior in decreasing the mean pulmonary artery pressure and equally effective and selective in reducing pulmonary vascular resistance.6It also causes a significant increase in the cardiac index.6Its availability in oral, inhaled and intravenous forms, longer half-life of 4 h,4and proven efficacy in randomized controlled trials7–9are some of the distinguishing features which make sildenafil first-choice agent for managing rebound pulmonary hypertension.
Thus, my question for Augoustides et al. is “Why inhaled iloprost and not sildenafil?”
Alder Hey Hospital, Liverpool, United Kingdom. firstname.lastname@example.org