Small-dose inhaled nitric oxide and pulmonary embolism.

Abstract

We read with interest the elegant case report by Schenk et al 1 Schenk P Mittermayer C Ratheiser K. Inhaled nitric oxide in a patient with severe pulmonary embolism. Ann Emerg Med. 1999; 33: 710-714 PubMed Google Scholar (article #97294) describing the use of inhaled nitric oxide (NO) in a patient with cardiogenic shock resulting from severe pulmonary embolism. Although controlled trials are needed to confirm the positive effects of inhaled NO in this critical setting, 2 Tanus-Santos JE. Inhaled nitric oxide and pulmonary embolism. Intensive Care Med. 1998; 24: 747-748 Crossref PubMed Scopus (2) Google Scholar Schenk et al suggest that NO may decrease the release of vasoconstrictors during pulmonary embolism. In support of this hypothesis, a low dose of inhaled NO (3 ppm) blunted the release of thromboxane A2 (a potent pulmonary vasoconstrictor) after air embolism in dogs. 3 Tanus-Santos JE Moreno Jr, H Moreno RA et al. Inhaled nitric oxide improves hemodynamics during a venous air infusion (VAI) in dogs. Intensive Care Med. 1999; 25: 983-989 Crossref PubMed Scopus (35) Google Scholar However, the suggestion by Schenk et al that NO 50 ppm is more effective than 5 ppm in the reduction of increased right ventricular afterload was not confirmed in a model of pulmonary air embolism in dogs. 3 Tanus-Santos JE Moreno Jr, H Moreno RA et al. Inhaled nitric oxide improves hemodynamics during a venous air infusion (VAI) in dogs. Intensive Care Med. 1999; 25: 983-989 Crossref PubMed Scopus (35) Google Scholar , 4 Tanus-Santos JE Moreno Jr, H Zappellini A et al. Small-dose inhaled nitric oxide attenuates hemodynamic changes after pulmonary air embolism in dogs. Anesth Analg. 1999; 88: 1025-1029 PubMed Google Scholar Therapy with NO 3 ppm or 40 ppm produced similar increases in cardiac index and decreases in pulmonary vascular resistance during air embolism, 3 Tanus-Santos JE Moreno Jr, H Moreno RA et al. Inhaled nitric oxide improves hemodynamics during a venous air infusion (VAI) in dogs. Intensive Care Med. 1999; 25: 983-989 Crossref PubMed Scopus (35) Google Scholar which may reflect the limited efficacy of higher doses of inhaled NO. Further, small-dose NO (3 ppm) attenuated the hemodynamic changes after massive pulmonary air embolism in dogs. 4 Tanus-Santos JE Moreno Jr, H Zappellini A et al. Small-dose inhaled nitric oxide attenuates hemodynamic changes after pulmonary air embolism in dogs. Anesth Analg. 1999; 88: 1025-1029 PubMed Google Scholar In summary, we believe that small-dose inhaled NO may be used as a coadjuvant therapy in massive pulmonary embolism. 5 Tanus-Santos JE Moreno Jr., H Inhaled nitric oxide as a coadjuvant therapy after massive pulmonary embolism. Can J Anaesth. 1999; 46: 906 PubMed Google Scholar Small doses reduce the potential risks of NO therapy, and any adverse effects would be rapidly reversed by withholding its administration.