Hepatopulmonary syndrome (HPS) is considered present when the following triad exists –
- Liver disease
- Impaired oxygenation
- Intrapulmonary vascular abnormalities, referred to as intrapulmonary vascular dilatations (IPVDs)
The unique pathological feature of hepatopulmonary syndrome (visualized by autopsy) is gross dilatation of the pulmonary precapillary and capillary vessels, as well as an absolute increase in the number of dilated vessels. A few pleural and pulmonary arteriovenous shunts and portopulmonary anastomoses may also be seen.
The hepatopulmonary syndrome results from the formation of microscopic intrapulmonary arteriovenous dilations in patients with chronic liver disease. The mechanism is unknown but is thought to be due to increased hepatic production or decreased hepatic clearance of vasodilators. The vascular dilations cause overperfusion relative to ventilation, leading to hypoxemia, particularly because patients have an increased cardiac output resulting from systemic vasodilation. Because the lesions frequently are more numerous at the lung bases, the hepatopulmonary syndrome can cause platypnea (dyspnea) and orthodeoxia (hypoxemia), which occur when the patient is seated or standing and are relieved by recumbency. Most patients also have characteristic findings of chronic liver disease, such as spider angiomas. About 20% of patients present with pulmonary symptoms alone.
The condition is said to be in two forms:
- Type I – The condition involves the right to left shunting of the lungs. This is known as the most common type of hepatopulmonary syndrome which basically involves dilatation of the capillaries during the exchange of oxygen. As a result, there is less oxygen containment in the alveoli- where gas exchange is the primary role, and the ventilation process is altered.
- Type II – This accumulates about 10% of hepatopulmonary syndrome cases. The oxygen exchange is yet again not attained normally, as arteriovenous shunts in the circulatory system have not attained its purpose. The anatomic shunts place the ineffective oxygen exchange, making this type of the syndrome as very grave one.
Causes
Presence of an arteriovenous shunt – This shunt is basically a product from a surgical intervention that provides a vessel indicated to provide a pathway for blood exchange between an artery and vein. This is highly indicated for patients for hemodiaysis.
Impaired function of the alveolocapillary in maintaining the diffusion-perfusion process – The pulmonary vessels are quite affected when a vasodilator takes place and acts in desaturating the oxygen. Making the erythrocytes incapable of providing adequate oxygenated blood.
Ventilation and perfusion process is uneven – When there is an underlying lung condition, it is expected that one will suffer from perfusion problems. In cases of liver cirrhosis, there shall be adecrease in perfusion in specific lung areas as ventilation is poor.
Others – Portal hypertension is considered a significant cause of hepatopulmonary syndrome. The chronic use of substances for vasodilatation can induce the syndrome.
Symptom
Those with hepatopulmonary syndrome are expected to present pulmonary symptoms as well as liver problem manifestations. The following present the characteristics of the disease –
- Hypoxemia is a prominent presentation. This is most recognizable especially when a person is suffering from liver cirrhosis.
- Cyanosis is noted among patients. This is described as the bluish or purple discoloration of our skin. The inside membranes or tissues of our body is also affected of the discoloration and is primary caused by a deficient flow of oxygenated blood.
- Digital clubbing (a known manifestation of hypoxemia and is described as the fingers’ tips are enlarged) is observed. This is due to the lack of oxygenation.
- Plethora of spider nevi is noted. This is identified as spider angioma where there are small angiomata on the skin. This is the spider-like appearance of the vessels visible on the skin. This is basically a manifestation of a hepatic problem.
- Platypnea is noted or simply known as dyspnea upon standing.
- Orthodeoxia is a manifestation. This is the sudden fall of the partial oxygen of the patient while in standing position.
- Increased Nitric oxide levels. This is noted due to its vasodilator component.
- Esophageal varices might develop. These are dilated veins found in the esophagus.
- Increased heart rate is noted as a sign of compensation from hypoxemia.
Treatment
Supplemental O 2 – The main treatment is supplemental O 2 for symptoms. Other therapies, such as somatostatin to inhibit vasodilation, are of modest benefit in only some patients. Coil embolization is virtually impossible because of the number and size of the lesions. Inhaled nitric oxide synthesis inhibitors may be a future treatment option. Hepatopulmonary syndrome may regress after liver transplantation or if the underlying liver disease subsides. Prognosis is poor without treatment.
Nitrous oxide inhibitor is provided. Even though there has been less support with this treatment, it has been found to reverse vasodilatation.
Control of the hypertension. Providing the suitable treatment for the client is a great help in managing the disease.
Orthotopic liver transplantation. This is considered as a treatment of choice when no other interventions seem to work. This is simply known as liver transplant.
Studies show that there is about 24 months to 5 years of survival rate among the reported cases of HPS. When surgical intervention such as liver transplant has not been performed, the survival rate shall be lower than expected.
Reference –
http://www.hindawi.com/journals/bmri/2013/670139/
http://www.atsjournals.org/doi/full/10.1164/rccm.201302-0245LE#.VrHI8_l97IU
http://lifeinthefastlane.com/ccc/hepatopulmonary-syndrome/
http://www.nature.com/nrgastro/journal/v9/n9/pdf/nrgastro.2012.123.pdf%3FWT.ec_id%3DNRGASTRO-201209
http://ehjcimaging.oxfordjournals.org/content/8/5/408
http://www.thelancet.com/pdfs/journals/lancet/PIIS0140673604161072.pdf