Hepatopulmonary syndrome
In medicine, hepatopulmonary syndrome is a syndrome of shortness of breath and hypoxemia (low oxygen levels in the blood of the arteries) caused by vasodilation (broadening of the blood vessels) in the lungs of patients with liver disease. Dyspnea and hypoxemia are worse in the upright position (which is called platypnea and orthodeoxia, respectively).
Contents |
[edit] Diagnosis
The hepatopulmonary syndrome is suspected in any patient with known liver disease who reports dyspnea (particularly platypnea). Patients with clinically significant symptoms should undergo pulse oximetry. If the syndrome is advanced, arterial blood gasses should be measured on air.
A useful diagnostic test is contrast echocardiography. Intravenous microbubbles (> 10 micrometers in diameter) from agitated normal saline that are normally obstructed by pulmonary capillaries (normally <8 to 15 micrometers) rapidly transit the lung and appear in the left atrium of the heart within 7 heart beats. Similarly, intravenous technetium-99m–labeled albumin may transit the lungs and appear in the kidney and brain. Pulmonary angiography may reveal diffusely fine or blotchy vascular configuration. The distinction has to be made with an intracardiac right-to-left shunt.
[edit] Disease mechanism
The hepatopulmonary syndrome results from the formation of microscopic intrapulmonary arteriovenous dilatations in patients with both chronic and acute liver failure. The mechanism is unknown but is thought to be due to increased hepatic production or decreased hepatic clearance of vasodilators, possibly involving nitric oxide.[1]
The vascular dilatations cause overperfusion relative to ventilation, leading to ventilation-perfusion mismatch and hypoxemia. There is an increased alveolar-arterial partial pressure of oxygen gradient while breathing room air. Additionally, late in cirrhosis, it is common to develop high output failure, which would lead to less time in capillaries per red blood cell, exacerbating the hypoxemia.
[edit] Treatment
Currently the only definitive treatment is liver transplantation.[2] Alternative treatments such as supplemental oxygen or somatostatin to inhibit vasodilation remain anecdotal.
[edit] Prognosis
With liver transplantation, the 5 year survival rate is 76%, which is comparable to patients who undergo liver transplants who do not suffer from hepatopulmonary syndrome.[3]
[edit] See also
[edit] References
- ^ Rodríguez-Roisin, MD, Roberto. "Hepatopulmonary Syndrome — A Liver-Induced Lung Vascular Disorder". New England Journal of Medicine. http://www.nejm.org/doi/full/10.1056/NEJMra0707185. Retrieved 2 March 2011.
- ^ Rodriguez-Roisin, R; Krowka MJ (Rodriguez-Roisin R, Krowka MJ. Is severe arterial hypoxaemia due to hepatic disease an indication for liver transplantation? A new therapeutic approach. Eur Respir J 1994;7:839-842). "Is severe arterial hypoxaemia due to hepatic disease an indication for liver transplantation?". European Respiratory Journal 7 (5): 839–842. PMID 8050537. http://erj.ersjournals.com/content/7/5/839.long. Retrieved 2 March 2011.
- ^ Swanson, KL; Swanson KL, Wiesner RH, Krowka MJ. Natural history of hepatopulmonary syndrome: impact of liver transplantation. Hepatology 2005;41:1122-1129 (12). "Natural history of hepatopulmonary syndrome: impact of liver transplantation". Hepatology 41 (5): Swanson KL, Wiesner RH, Krowka MJ. Natural history of hepatopulmonary syndrome: impact of liver transplantation. Hepatology 2005;41:1122–1129. doi:10.1002/hep.20658. PMID 15828054.
