Acid-Base Balance and Electrolytes

Diuretic therapy can result in intravascular volume depletion, hyponatremia, and hypokalemia. Excessive antidiuretic hormone activity can contribute to the hyponatremia, which should be corrected very slowly to avoid central pontine myelinolysis. Hypokalemia rarely requires potassium administration. Hyperkalemia can be present in patients with renal failure, and usually requires dialysis. Metabolic alkalosis is due to hypokalemia and drainage of gastric secretions, and metabolic acidosis can be the result of compromised tissue perfusion in severely ill patients. Correction of all these problems is difficult preoperatively.

Carbohydrate Metabolism

Hypoglycemia can occur with fulminant hepatic failure. Chronic liver disease may lead to insulin resistance and high glucagon levels, although hyperglycemia is rarely seen.

Hematology and Coagulation

Almost all candidates for liver transplantation have synthetic liver dysfunction, and therefore have coagulopathy as a result of decreased production of coagulation factors (especially factors II, V, VII, IX, and X). Fibrinogen levels may be high, normal, or low. In addition, portal hypertension leads to sequestration of platelets in the spleen, and therefore thrombocytopenia contributes to the coagulopathy. However, coagulation changes are complex because the liver also produces inhibitors of coagulation and fibrinolytic proteins (plasminogen and alpha2-antiplasmin), and because activated coagulation factors are normally cleared by the liver. This may lead to varying degrees of disseminated intravascular coagulation. Correction of the coagulopathy is best done intraoperatively, except when patients are bleeding acutely or when coagulopathy is extreme (prothrombin time [PT] > 20 s, platelet count < 20,000,000/mL). Anemia may be the result of continuing gastrointestinal bleeding, erythrocyte destruction in the spleen, and reduced production in the bone marrow. Preoperatively patients need routine hemostatic evaluation, with special analyses for items such as preexisting red cell alloantibodies. If HLA antibodies are present they will not only affect graft survival but also reduce in vivo yields of transfused platelets, unless special products are selected. Patients with broadly reactive red cell or HLA antibodies require careful preoperative planning between surgeons, anesthesiologists, and coagulation/ transfusion specialists. Rare circulating anticoagulants can sometimes be managed by preoperative plasmapheresis.

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