Many hospitalists will be asked to assess the operative risk of patients who have acute or chronic liver disease. The following chapter outlines an assessment plan and a basis for predicting operative morbidity and mortality. Evaluation of patients with liver disease prior to surgery is crucial to estimate perioperative morbidity and mortality. The operative risk of liver disease can be related to the rapid changes in liver function that can occur in acute hepatitis, or can be related to chronic complications of portal hypertension and parenchymal liver disease in patients with cirrhosis. Therefore, establishment of a risk profile should be based on the etiology of the underlying liver disease, the degree of hepatic decompensation associated with the presence of cirrhosis and portal hypertension, and the type of surgery the patient is undergoing.
FACTORS THAT AFFECT PERIOPERATIVE OUTCOMES IN LIVER DISEASE PATIENTS
CHANGES IN HEPATIC BLOOD FLOW
The liver receives dual blood supply from the portal vein and the hepatic artery. Unlike most other organs, the majority of hepatic oxygen supply in normal individuals is venous, via the portal vein. Administration of anesthesia and surgery influences both portal and hepatic blood flow; usually, when flow through the portal vein is reduced, the hepatic artery vasodilates to increase oxygen supply to the liver. This compensatory vasodilatation is reduced in patients with altered hepatic architecture (such as fibrosis and nodular formation associated with cirrhosis). Due to intraoperative decreases in blood pressure and cardiac output, blood flow in patients with cirrhosis is decreased in the portal vein, splanchnic vessels, and hepatic artery; anesthetics also reduce the hepatic artery’s ability to vasodilate in response to these changes in portal blood flow.
These changes in hepatic blood flow may lead to hepatic ischemia and necrosis. The release of inflammatory mediators may result in multiorgan system failure. In a study of 733 cirrhosis patients undergoing surgery, Ziser et al found an 11.6% mortality rate. Intraoperative hypotension correlated strongly with perioperative complications and decreased survival.
Postoperative morbidity and mortality in patients with cirrhosis is also influenced by the type of surgery.
During abdominal surgery, direct trauma due to surgical retraction can lead to hepatic injury. Manipulation of the splachnic and portal vasculature may also reduce portal or hepatic flow leading to ischemic injury. In particular, patients with Child-Pugh class C cirrhosis who undergo abdominal surgery have a 75% perioperative mortality.
Cardiovascular surgery, due to effects on portal and hepatic artery blood flow, is also associated with high perioperative morbidity and mortality. The need for perioperative pressor support and prolonged cardiopulmonary bypass are factors that strongly correlate with hepatic injury.