1 What is the Model for End-stage Liver Disease MELD?

The Model for End-stage Liver Disease (MELD) is a scoring system for prioritizing patients for liver transplantation. The MELD score is an objective model that predicts a patient’s 90-day mortality while waiting for a liver transplant. It is a better predictor of perioperative mortality than the Child’s scoring system and therefore has replaced it. MELD is calculated using bilirubin, international normalized ratio, and creatinine (the MELD calculator can be accessed at www.UNOS.org). There are four listing status categories for patients with liver disease:

Status 1 includes patients with acute liver failure/disease with an estimated survival of less than 7 days (highest priority for liver transplantation).

Status 2a (MELD score >29) includes patients with end-stage liver disease, severely ill, and potentially hospitalized.

Status 2b (MELD score 24–29) includes patients with end-stage liver disease, severely ill, but not requiring hospitalization.

Status 3 (MELD score <24) includes patients with liver disease that is too early for cadaveric transplantation but may be a suitable live donor transplantation candidate.

2 Describe some indications and contraindications for liver transplantation

Indications for liver transplantation include end-stage liver disease from hepatocellular disease, cholestatic disease, vascular disease, or polycystic disease. In addition, some nonresectable hepatic malignancies, metabolic liver diseases, and fulminant hepatic failure are indications (Table 69-1). Over time relative and absolute contraindications for liver transplantation have evolved (Table 69-2). Because MELD predicts 3-month survival, those with the highest scores have the greatest chance of dying from liver disease and thus have the best risk-benefit ratio for undergoing liver transplantation.

TABLE 69-1 Indications for Liver Transplantation

TABLE 69-2 Contraindications to Liver Transplantation

3 How does the cardiovascular physiology of a patient with end-stage liver disease differ from that of a normal patient?

Patients with end-stage liver disease have a hyperdynamic circulation, characterized by increased cardiac index and decreased systemic vascular resistance. This results in a consistently lower blood pressure and increased heart rate. Patients are significantly less responsive to catecholamines. Cirrhotic patients tend to be overloaded with total body water but arterially dehydrated. Pulmonary blood flow is increased and can result in increased pulmonary artery pressures; pulmonary vascular resistance usually remains normal. Coronary artery disease with resulting impaired myocardial function (previously thought to be uncommon in patients with liver disease) may be present, especially when the patient has diabetes. Coronary artery disease in liver transplant patients older than 50 years occurs in a range of 5% to 27%. Abnormalities in both systolic and diastolic function may be present and result in an inadequate cardiac output for the degree of vasodilation. This is especially true in patients with a history of alcohol abuse.

4 What are some preanesthetic considerations in a liver transplant patient?

Optimal anesthetic management of these complex, critically ill patients requires management of the pathophysiologic changes of liver disease, comorbid conditions, and the physiologic changes associated with the surgery. In some instances (e.g., pulmonary hypertension, hepatorenal syndrome), hepatic disease may be overshadowed by the severity of the comorbid conditions. Prior abdominal surgeries and encephalopathy are important features to note, as are coagulation deficits (factor deficiencies and thrombocytopenia). The thromboelastogram (TEG) provides valuable insight into the patient’s entire clotting process. The TEG graphs the viscoelastic properties of a clot from the formation of the first fibrin strands to the full hemostatic plug. Thus the TEG is a dynamic test showing the evolution of clot formation. Because the TEG examines multiple phases of clot formation within a single test, it reflects information that is otherwise available only in multiple tests. The TEG is the best laboratory assessment of qualitative platelet function.

Electrolyte abnormalities are common. Hypokalemia is commonly seen in earlier stages of liver disease since hepatic injury leads to hyperaldosteronism. Hyperkalemia may be caused by the use of potassium-sparing diuretics to treat ascites and hepatorenal syndrome. Hyponatremia may result from diuretic use, hyperaldosteronism, or volume overload. Renal dysfunction should be assessed since intraoperative dialysis may be necessary. In fulminant hepatic failure, cerebral cytotoxic edema is a common complication, and there must be aggressive preoperative control of intracranial pressure to prevent brainstem herniation, a common cause of death. Patients with cerebral edema should have an intracranial pressure monitoring device.

Pulmonary hypertension associated with cirrhosis occurs in approximately 8% of patients and is a cause of significant intraoperative morbidity and mortality. Many liver failure patients are hypoxemic secondary to atelectasis and hepatopulmonary syndrome. All potential transplant candidates should undergo a screening transthoracic echocardiogram to assess pulmonary arterial pressures, left ventricular function, and intrapulmonary shunting. If pulmonary arterial pressures are elevated or right ventricular function is decreased, a right heart catheterization may be indicated.

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