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%). Pa02 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.