Patients with serious liver disease are at increased risk for perioperative morbidity and demise. Appropriate preoperative evaluation requires consideration of the effects of anesthesia and surgery on postoperative liver function and of the complications associated with anesthesia and surgery in patients with preexisting liver disease.
THE EFFECTS OF ANESTHESIA & SURGERY ON LIVER FUNCTION
Postoperative elevation of serum aminotransferase levels is a relatively common finding after major surgery. Most of these elevations are transient and not associated with hepatic dysfunction. While direct hepatotoxicity is rare with modern anesthetics agents, these medications may cause deterioration of hepatic function via intraoperative reduction in hepatic blood flow leading to ischemic injury. Intraoperative hypotension, hemorrhage, and hypoxemia may also contribute to liver injury.
RISK ASSESSMENT IN SURGICAL PATIENTS WITH LIVER DISEASE
Screening unselected patients with liver biochemical tests has a low yield and is not recommended. Patients with suspected or known liver disease based on history or physical examination, however, should have measurement of liver enzyme levels as well as tests of hepatic synthetic function performed prior to surgery.
Elective surgery in patients with acute viral or alcoholic hepatitis should be delayed until the acute episode has resolved. In three small series of patients with acute viral hepatitis who underwent abdominal surgery, the mortality rate was roughly 10%. Similarly, patients with undiagnosed alcoholic hepatitis had high mortality rates when undergoing abdominal surgery. In the absence of cirrhosis or synthetic dysfunction, chronic viral hepatitis is unlikely to increase risk significantly. A large cohort study of hepatitis C seropositive patients who underwent surgery found a mortality rate of less than 1%. Similarly, nonalcoholic fatty liver disease without cirrhosis probably does not pose a serious risk in surgical patients.
In patients with cirrhosis, postoperative complication rates correlate with the severity of liver dysfunction. Traditionally, severity of dysfunction has been assessed with the Child-Pugh score (see Chapter 16-11). Patients with Child-Pugh class C cirrhosis who underwent portosystemic shunt surgery, biliary surgery, or trauma surgery during the 1970s and 1980s had a 50–85% mortality rate. Patients with Child-Pugh class A or B cirrhosis who underwent abdominal surgery during the 1990s, however, had relatively low mortality rates (hepatectomy 0–8%, open cholecystectomy 0–1%, laparoscopic cholecystectomy 0–1%). A conservative approach would be to avoid elective surgery in patients with Child-Pugh class C cirrhosis and pursue it with great caution in class B patients. The Model for End-stage Liver Disease (MELD) score, based on serum bilirubin and creatinine levels, and the prothrombin time expressed as the international normalized ratio (INR), also predicted surgical mortality and outperformed the Child-Pugh classification in some studies. A web-based risk assessment calculator incorporating age and MELD score can predict both perioperative and long-term mortality (https://www.mayoclinic.org/medical-professionals/model-end-stage-liver-disease/post-operative-mortality-risk-patients-cirrhosis). Generally, a MELD score less than 10 predicts low risk, whereas a score greater than 16 portends high mortality after elective surgery.