Hepatopulmonary syndrome: the paradigm of liver-induced hypoxaemia

The utility of the macro-aggregated albumin lung perfusion scan in the diagnosis and prognosis of hepatopulmonary syndrome in cirrhotic patients candidates for liver transplantation

BACKGROUND

The macro-aggregated albumin lung perfusion scan (99mTc-MAA) is a diagnostic method for hepatopulmonary syndrome (HPS).

GOAL

To determine the sensitivity of 99mTc-MAA in diagnosing HPS, to establish the utility of 99mTc-MAA in determining the influence of HPS on hypoxemia in patients with concomitant pulmonary disease and to determine the correlation between 99mTc-MAA values and other respiratory parameters.

METHODS

Data from 115 cirrhotic patients who were eligible for liver transplantation (LT) were prospectively analyzed. A transthoracic contrast echocardiography and 99mTc-MAA were performed in 85 patients, and 74 patients were diagnosed with HPS.

RESULTS

The overall sensitivity of 99mTc-MAA for the diagnosis of HPS was 18.9% (14/74) in all of the HPS cases and 66.7% (4/6) in the severe to very severe cases. In HPS patients who did not have lung disease, the degree of brain uptake of 99mTc-MAA was correlated with the alveolar-arterial oxygen gradient (A-a PO2) (r = 0.32, p < 0.05) and estimated oxygen shunt (r = 0.41, p < 0.05) and inversely correlated with partial pressure of arterial oxygen (PaO2) while breathing 100% O2 (r = -0.43, p < 0.05). The 99mTc-MAA was positive in 20.6% (7/36) of the patients with HPS and lung disease. The brain uptake of 99mTc-MAA was not associated with mortality and normalized in all cases six months after LT.

CONCLUSIONS

The 99mTc-MAA is a low sensitivity test for the diagnosis of HPS that can be useful in patients who have concomitant lung disease and in severe to very severe cases of HPS. It was not related to mortality, and brain uptake normalized after LT.

Síndrome hepatopulmonar: patogenia, diagnóstico e tratamento

RACIONAL: A síndrome hepatopulmonar é caracterizada por tríade clínica que consiste em: 1) doença hepática e/ou hipertensão portal, 2) dilatações vasculares intra-pulmonares, e 3) anormalidades da oxigenação arterial (pressão parcial de oxigênio <70 mm Hg ou gradiente alvéolo-arterial de oxigênio >20 mm Hg). Sua freqüência varia de acordo com os métodos diagnósticos utilizados. OBJETIVOS: Fazer revisão da literatura sobre patogenia, diagnóstico e tratamento da síndrome hepatopulmonar. MÉTODOS: Levantamento no MEDLINE das publicações nacionais e internacionais mais relevantes sobre a síndrome hepatopulmonar. RESULTADOS: A prevalência da síndrome hepatopulmonar varia de 4% a 17,5%, a depender dos critérios diagnósticos utilizados. A doença hepática associada mais comum é a cirrose. O gradiente alvéolo-arterial de oxigênio parece ser o melhor parâmetro para avaliação das anormalidades da oxigenação arterial. Em relação à detecção das dilatações vasculares intra-pulmonares, a ecocardiografia com contraste é o método de escolha, pois é de fácil realização e pode diferenciar as comunicações intra-pulmonares das intra-cardíacas. No tratamento da síndrome hepatopulmonar, poucos relatos bem sucedidos puderam ser reproduzidos e confirmados utilizando terapia farmacológica e/ou radiologia intervencionista. Atualmente, o transplante de fígado é considerado a principal opção terapêutica desses pacientes, com resultados animadores. CONCLUSÕES: A síndrome hepatopulmonar é uma enfermidade freqüente. Exames gasométricos são necessários para o seu diagnóstico. O transplante de fígado é o tratamento de escolha para os portadores da síndrome.

Implications of estradiol and progesterone in pulmonary vasodilatation in cirrhotic patients

The derangement of sex hormone serum levels in cirrhotic patients is well-delineated, and increased levels of progesterone and estradiol have been associated to hyperventilation in cirrhotic patients. These hormones have a well-known role in the regulation of vascular tone. The aim of this study was to evaluate whether sex hormone levels contribute to pulmonary vasodilatation (PV) and gas exchange abnormalities in cirrhosis. Contrast transesophageal echocardiography, arterial blood gases, parameters of liver function, pulmonary function test, estradiol and progesterone levels were determined in 45 male cirrhotic patients. Nineteen of 45 patients (42.2%) presented PV. Hyperventilation (pressure arterial of CO2< or =35 mmHg) was correlated to progesterone levels (p<0.05) and pressure arterial of CO2 was high in patients with PV (p<0.005) and Child class B and C (p<0.01). Hypoxemia (pressure arterial of O2<80 mmHg) had inverse correlation with progesterone (p<0.05) and estradiol (p<0.05) levels and pressure arterial of O2 was low in patients with Child class B and C (p<0.05). PV was present in patients with high estradiol levels (p<0.05), high progesterone levels (p<0.005) and Pugh class B and C (p<0.05). Logistic regression analysis identified progesterone as the sole independent factor associated to PV (p<0.0005). Multivariate linear regression showed that PV was the sole independent factor related to both pressure arterial of CO2 (p<0.05) and pressure arterial of O2 (p<0.01) levels. PV was independently associated to gas exchange abnormalities in cirrhosis. Progesterone and estradiol were related with PV in cirrhotic patients.

Presence of a nitric oxide synthase inhibitor in the graft efflux during reperfusion in human liver transplantation

Involvement of the nitric oxide (NO) system in complications following human orthotopic liver transplants (OLT) has been reported, but the contribution of the graft to the modulation of the NO system during reperfusion in normal OLT has not been characterized. We have studied the contribution of the graft efflux to the modulation of the NO system in 20 consecutive OLT. We evaluated its effects on isolated vascular reactivity of the rabbit and on rat cultured macrophages stimulated with lipopolysaccharide (LPS). In none of the donor liver biopsies was expression of inducible NO synthase (iNOS) activity by Northern or Western blot analysis found. Graft efflux after the onset of liver reperfusion, but not pre-transplant patient plasma, reversibly inhibited the acetylcholine-induced relaxation of norepinephrine-contracted rabbit aortic rings. Moreover, graft efflux reversibly inhibited NO production in rat macrophages treated with LPS, as evidenced by both a decrease in nitrite plus nitrate formation and a decrease in the production of [14C]citrulline from [14C]arginine. Addition of a 10% dilution of graft efflux to cultured rat macrophages incubated with LPS increased iNOS mRNA levels, suggesting direct inhibition of the enzyme but not of its expression. These results cannot be ascribed to the depletion of arginine the iNOS substrate since they can be reproduced even in the presence of an excess (10 mM) of exogenously added arginine. No correlation was found between the iNOS inhibitory activity in each sample and the corresponding clinical parameters related to either the graft function after the OLT or the existence of post-reperfusion syndrome. Our results indicate the existence of a soluble factor in the graft efflux from human OLT that reversibly and unspecifically inhibits NOS activity. Its involvement in the physiology and/or pathology of human liver diseases deserves further study.

Hepatopulmonary syndrome associated with cardiorespiratory disease

BACKGROUND/AIMS

Hepatopulmonary syndrome is defined as a clinical triad including chronic liver disease, abnormal pulmonary gas exchange resulting ultimately in profound arterial hypoxaemia, and evidence of intrapulmonary vascular dilatations. We report five patients with liver cirrhosis diagnosed with hepatopulmonary syndrome who had associated chronic obstructive or restrictive respiratory diseases.

METHODS

Clinical, radiographic and constrast-enhanced echocardiographic findings, and systemic and pulmonary haemodynamic and gas exchange, including ventilation-perfusion distributions, measurements were assessed in all five patients.

RESULTS

Echocardiography was consistent with the presence of intrapulmonary vasodilation without intracardiac abnormalities, and high resolution computed tomographic scan features were compatible with clinical (3 cases) or histopathological diagnoses (2 cases) of associated respiratory disorders. The most common prominent functional findings were moderate to severe arterial hypoxaemia, caused by moderately to severely increased intrapulmonary shunting and/or mild to moderate low ventilation-perfusion areas, and hypocarbia along with an increased cardiac output and a low pulmonary artery pressure and vascular resistance.

CONCLUSIONS

These functional characteristics, classically reported in the setting of clinically stable, uncomplicated hepatopulmonary syndrome, conform to a distinctively unique, chronic gas exchange pattern. Equally important, these pulmonary haemodynamic-gas exchange hallmarks are not influenced by the co-existence of chronic cardiorespiratory disease states. These data may have clinical relevance for elective indication of hepatic transplantation in patients with life-threatening hepatopulmonary syndrome.

The hepatopulmonary syndrome

The hepatopulmonary syndrome is a disease entity seen in association with liver failure and other disease entities. It is a devastating consequence of liver failure that results in a significant morbidity for affected patients. Currently, there are no identified medications that ameliorate the symptoms of hypoxemia in this disease state. Recent research, however, has begun to unravel the pathobiology of the vascular dilations that arise in the lungs of patients with liver failure. In this article, a compendium of current knowledge is presented, as well as the contemporary methods for identifying and treating patients.