Arterial oxygenation associated with portopulmonary hypertension

Study objectives: To characterize arterial oxygenation in patients referred to Mayo Clinic for liver transplantation with a diagnosis of portopulmonary hypertension (portoPH). Design: Prospective study. Setting: Liver transplantation program and pulmonary hypertension clinic in a tertiary referral center. Participants: Twenty consecutive patients with abnormal pulmonary hemodynamics documented by right-heart catheterization (mean pulmonary artery pressure [MPAP] ≥ 25 mm Hg, pulmonary vascular resistance [PVR] ≥ 120 dyne·s·cm-⁵, and pulmonary capillary wedge pressure [PCWP] ≤ 15 mm Hg). Liver transplant candidates with normal pulmonary hemodynamics via screening Doppler echocardiography (n = 40) served as control subjects. A subgroup of patients underwent postural and inspired 100% oxygen blood gas analysis, contrast echocardiography, and technetium-labeled macroaggregated albumin (^99mTcMAA) lung/brain scanning to identify and quantitate the degree of intracardiac or intrapulmonary shunting. Measurements and results: portoPH was moderate to severe (MPAP ≥ 35 mm Hg) in 18 of 20 patients (90%). Arterial-alveolar oxygen pressure gradient (P[A-a]O₂) was abnormal (≥ 20 mm Hg) in 16 of 20 patients (80%). PaO₂ was abnormal (≤ 70 mm Hg) in 3 of 20 patients (15%). PaO₂ was significantly less and P(A-a)O₂ was significantly greater compared to control subjects (p ≤ 0.001). All patients had normal _99mTcMAA brain uptake (≤ 6%) and negative transthoracic contrast echocardiographic findings. No significant correlations were found between oxygenation and hemodynamic variables (MPAP, PVR, PVR index, and transpulmonary gradient). Conclusions: Arterial oxygenation associated with portoPH was frequently abnormal and significantly worse when compared to patients with normal pulmonary hemodynamics by Doppler echocardiography. Hypoxemia, as measured by PaO₂ and P(A-a)O₂, was usually mild even in the setting of moderate-to-severe portoPH.