Pulmonary vascular complications of chronic liver disease: Pathophysiology, imaging, and treatment

Supine vs upright exercise in patients with hepatopulmonary syndrome and orthodeoxia: study protocol for a randomized controlled crossover trial

BACKGROUND

The hepatopulmonary syndrome (HPS) is a pulmonary complication of liver disease found in 10 to 32% of patients with cirrhosis and is characterized by intrapulmonary vascular dilatations and abnormal oxygenation. Liver transplantation is the only effective therapy for this disease. Patients with HPS have significant exercise limitations, impacting their quality of life and associated with poor liver transplant outcomes. Many patients with HPS exhibit orthodeoxia-an improvement in oxygenation in the supine compared to the upright position. We hypothesize that exercise capacity will be superior in the supine compared to the upright position in such patients.

METHODS

We propose a randomized controlled crossover trial in patients with moderate HPS (PaO₂ < 80 mmHg) and orthodeoxia (supine to upright PaO₂ decrease > 4 mmHg) comparing the effect of supine vs upright position on exercise. Patients with pulmonary hypertension, FEV1/FVC ratio < 0.65, significant coronary artery disease, disorders preventing or contraindicating use of a cycle ergometer, and/or moderate or severe ascites will be excluded. Participants will be randomized to cycle ergometry in either the supine or upright position. After a short washout period (a minimum of 1 day to a maximum of 4 weeks), participants will crossover and perform an exercise in the alternate position. Exercise will be performed at a constant work rate of 70-85% of the predicted peak work rate until the "stopping time" is reached, defined by exhaustion, profound desaturation, or safety concerns (drop in systolic blood pressure or life-threatening arrhythmia). The primary outcome will be the difference in the stopping time between exercise positions, compared with a repeated measures analysis of variance method with a mixed effects model approach. The model will be adjusted for period effects. P < 0.05 will be considered statistically significant.

DISCUSSION

HPS patients have hypoxemia leading to significant exercise limitations. If our study is positive, a supine exercise regimen could become a routine prescription for patients with HPS and orthodeoxia, enabling them to exercise more effectively. Future studies could explore the corresponding effects of a supine exercise training regimen on physiologic variables such as long-term exercise capacity, quality of life, dyspnea, and liver transplantation outcomes.

TRIAL REGISTRATION

ClinicalTrials.gov Protocol Registration and Results System (PRS) NCT04004104 . Registered on 1 July 2019.

Pulmonary Complications in Candidates for Liver Transplantation

The liver plays a pivotal role in maintaining the homeostasis of various organ systems. Also, end-stage liver disease and its complications are major causes of morbidity and mortality among adults. Individuals who develop a chronic liver disease are at increased risk of progression to multi-organ dysfunction, including the pulmonary system. The clinical complications of pulmonary problems related to the presence of liver disease range from mild (such as hypoxemia) to life-threatening diseases (such as portopulmonary hypertension and hepatopulmonary syndrome). Herein, the major pulmonary complications related to liver cirrhosis and considerations for performing liver transplantation are reviewed.

Assessing the kinetics of microbubble appearance in cirrhotic patients using transthoracic saline contrast-enhanced echocardiography

BACKGROUND

The number of cardiac cycles that need to be reviewed by echocardiography before a significant intrapulmonary shunt can be excluded remains unclear.

METHODS

We retrospectively identified patients with cirrhosis who underwent technetium-99 m-labeled macroaggregated albumin scanning. The kinetics of bubble appearance after the injection of agitated saline during transthoracic echocardiograms were assessed in these patients.

RESULTS

For the 64 eligible patients, the mean ± SD age was 56 ± 9 years. The median (IQR) shunt fraction by radionuclide scanning was 7.7% (2.8%-19.9%). Microbubbles were seen in the left atrium (LA) and left ventricle (LV) at a median (IQR) of 4 (2-5) and 4 (2-5) beats, respectively. The number of heart cycles before microbubbles appeared in the LA or LV was inversely associated with the nuclear scanning shunt fraction (R = -0.42, P = .001, R = -0.46, P < .001, respectively). If no microbubbles were detected by heart cycle 7, the shunt fraction was uniformly less than 3%. Patients with arterial oxygen <60 mm Hg, compared to ≥60 mm Hg, had earlier appearance of microbubbles in the left heart chambers (2.6 ± 1.9 vs 4.0 ± 2.3 beats, P = .046).

CONCLUSIONS

In patients with advanced cirrhosis suspected of having hepatopulmonary syndrome, a greater shunt fraction during nuclear scanning was associated with more pronounced hypoxemia and a prompt and more intense appearance of microbubbles in the left-sided heart chambers. Patients with a shunt fraction above 3% have microbubbles in the LA or LV at some point during the first seven heart cycles.

[Portopulmonary hypertension: Updated review]

Portopulmonary hypertension (PPH) is a rare condition worldwide, although epidemiological data are unknown in Mexico. However, chronic liver diseases are very prevalent in Mexico. PPH is the 4th subtype in frequency in the group of pulmonary arterial hypertension. Its diagnosis is made within 2 scenarios: patients with suspected pulmonary hypertension and candidates for orthotopic liver transplantation (OLT). Both echocardiogram and a right cardiac catheterisation are crucial for diagnosis in both cases. PPH is a challenge for OLT, since it can significantly increase perioperative mortality. The use of specific therapy is the cornerstone of this disease, as a measure to improve the outcome of those who become candidates for OLT with moderate to severe PPH. It is important to recognise that PPH can be a contraindication to OLT. The role of lung-liver transplantation or heart-lung-liver transplantation as a measure to heal pulmonary vascular disease in patients with PPH is still uncertain.

Intrapulmonary vascular dilation in children with chronic liver diseases: pre- and post-liver transplantation

BACKGROUND AND STUDY AIMS

Chronic liver disease (CLD) can cause hepatopulmonary syndrome (HPS), defined as triad of liver disease, hypoxemia, and intrapulmonary vascular dilation (IPVD). The aim of this study was to determine the evidence of IPVD in a cohort of pediatric patients with CLD pre- and post-liver transplantation (LT).

MATERIAL AND METHODS

All pediatric patients with CLD listed for LT were studied. Pulse oxygen saturation (SpO(2)), technetium-99m-labeled macroaggregated albumin ((99m)Tc- MAA) perfusión scan (positive test: uptake of the isotope ≥ 6% in the brain), and echocardiography with saline bubble test (SBT) were performed. SBT was re-evaluated at 3-6 months after LT. Grading of SBT included grade 0 (no bubble), I (1-9 bubbles), grade II (10-20 bubbles), and grade III (> 20 bubbles).

RESULTS

Eighteen patients, median age 22.5 months (8-108), were enrolled. Most had biliary atresia (77.8%). Pre-LT, all patients had SpO(2) of 100% and none had positive (99)mTc- MAA perfusion scan. Two patients (11%) had negative SBT (grade 0), 1 (5.5%) had grade I, 3 (16.5%) had grade II, and 12 (67%) had grade III, respectively. Post-LT SBT became negative in all survivors (n = 16), (p = 0.0001).

CONCLUSIONS

Most cirrhotic children in this cohort study had evidence of IPVD by positive SBT. However, none of these met the criteria for diagnosis of HPS. This evidence of IPVD subsided after LT.

Hepatopulmonary Syndrome

Hepatopulmonary syndrome (HPS) is a pulmonary complication observed in patients with chronic liver disease and/or portal hypertension, attributable to an intrapulmonary vascular dilatation that may induce severe hypoxemia. Microvascular dilation and angiogenesis in the lung have been identified as pathologic features that drive gas exchange abnormalities in experimental HPS. Pulse oximetry is a useful screening test for HPS, which can guide subsequent use of arterial blood gases. Contrast-enhanced echocardiography, perfusion lung scanning, and pulmonary arteriography are three currently used diagnostic imaging modalities that identify the presence of intrapulmonary vascular abnormalities. The presence of HPS increases mortality and impairs quality of life, but is reversible with liver transplantation. No medical therapy is established as effective for HPS. At the present time, liver transplantation is the only available treatment for HPS.

Cirrhosis and hepatopulmonary syndrome

Hepatopulmonary syndrome (HPS) is characterized as a triad: liver disease, intrapulmonary vascular dilatation and arterial hypoxemia. HPS is reported to be present in 4% to 32% of adult patients with end-stage liver disease and in 9%-20% of children. The pathogenesis of HPS has not been clearly identified. Portal hypertension causes impairment in the perfusion of the bowel and increases the enteral translocation of Gram (-) bacteria and endotoxins. This stimulates the release of vasoactive mediators, such as tumor necrosis factor-alpha, heme oxygenase-derived carbon monoxide and nitric oxide. Genetic alterations have not been associated with this syndrome yet; however, cytokines and chemokines have been suggested to play a role. Recently, it was reported that cumulated monocytes lead to the activation of vascular endothelial growth factor-dependent signaling pathways and pulmonary angiogenesis, which plays an important role in HPS pathogenesis. At present, the most effective and only radical treatment is a liver transplant (LT). Cirrhotic patients who are on the waiting list for an LT have a shorter survival period if they develop HPS. Therefore, it is suggested that all cirrhotic cases should be followed closely for HPS and they should have priority in the waiting list.

The end-organ impairment in liver cirrhosis: appointments for critical care

Liver cirrhosis (LC) can lead to a clinical state of liver failure, which can exacerbate through the course of the disease. New therapies aimed to control the diverse etiologies are now more effective, although the disease may result in advanced stages of liver failure, where liver transplantation (LT) remains the most effective treatment. The extended lifespan of these patients and the extended possibilities of liver support devices make their admission to an intensive care unit (ICU) more probable. In this paper the LC is approached from the point of view of the pathophysiological alterations present in LC patients previous to ICU admission, particularly cardiovascular, but also renal, coagulopathic, and encephalopathic. Infections and available liver detoxifications devices also deserve mentioning. We intend to contribute towards ICU physician readiness to the care for this particular type of patients, possibly in dedicated ICUs.