A comparison of inhaled nitric oxide with intravenous vasodilators in the assessment of pulmonary haemodynamics prior to cardiac transplantation

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Abstract
OBJECTIVE: Elevated pulmonary vascular resistance and transpulmonarygradient are predictors of increased perioperative mortality in patientsundergoing orthotopic heart transplantation. Sodium nitroprusside andprostacyclin PGI2 are routinely used to assess the reversibility ofpulmonary vascular resistance and transpulmonary gradient in hearttransplant candidates, but their use is limited by their systemicvasodilatory effect. The aim of this study was to evaluate the systemic andpulmonary haemodynamic effects of low concentration (10 and 20 parts permillion) inhaled nitric oxide in patients with severe heart failure withelevated transpulmonary gradient and pulmonary vascular resistanceundergoing assessment for cardiac transplantation, and to compare thehaemodynamic effects of inhaled nitric oxide with those of sodiumnitroprusside and prostacyclin PGI2. METHOD: In 10 consecutive patientswith elevated transpulmonary gradient (16+/-2 mm Hg) and pulmonary vascularresistance (3.6 +/-0.3 Wood units (WU)) nitric oxide (10 and 20 parts permillion in 23% inspired oxygen (O2) via a tight fitting facemask) andincreasing doses of intravenous sodium nitroprusside and prostacyclin wereadministered in a random, single-blinded fashion. RESULTS: Inhalation ofnitric oxide (10 ppm) reduced the transpulmonary gradient (-7+/-2 mm Hg;P<0.01) and pulmonary vascular resistance (- 1.8+/-0.4 WU; P<0.001)but did not affect the systemic vascular resistance (-0.3+/-1 WU) or meansystemic arterial pressure (-1.3 5 mm Hg). Sodium nitroprusside andprostacyclin reduced the transpulmonary gradient (-4.5+/-2 mm Hg; P<0.01and -3.6+/-2 mm Hg; P<0.05), pulmonary vascular resistance (-1.5+/-0.4WU; P<0.001 and -1.3+/-0.4 WU; P<0.01), systemic vascular resistance(-7+/-2 WU; P<0.01 and -7.2+/-2 WU; P<0.01) and mean systemicarterial pressure (-15+/-5 mm Hg; P<0.01 and - 18+/-4 mm Hg; P<0.01).CONCLUSION: Low-concentration inhaled nitric oxide is as effective assodium nitroprusside and prostacyclin in reducing transpulmonary gradientand pulmonary vascular resistance, and is highly pulmonaryvasoselective.

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