F Portosystemic shunts
Portosystemic shunt procedures are performed to prevent or cease variceal hemorrhage resulting from portal hypertension in patients with liver disease, cirrhosis, ascites, and hypersplenism. The redistribution of blood from the portal vein to the inferior vena cava causes variations in flow and resistance of the liver, intestine, and spleen. This hemodynamic alteration aids portal perfusion and oxygenation with the net effects of increased venous return and cardiac output. Variations in procedures include portocaval, end-to-end, end-to-side, mesocaval, mesorenal, and splenorenal shunts.
2. Preoperative assessment and patient preparation
a) History and physical examination
(1) Cardiac: Associated conditions include increased heart rate, circulating blood volume, and intrathoracic pressure. Variations of cardiac output, cardiomyopathy, congestive heart failure, CAD, and decreased response to catecholamines and SVR may be present.
(2) Respiratory: Hypoxemia may be related to ventilation/perfusion mismatch, increased closing volume, decreased functional residual capacity, atelectasis, right-to-left pulmonary shunting, increased diphosphoglycerate, pulmonary infections, and impaired hypoxic pulmonary vasoconstriction.
(3) Neurologic: Manifestations may include hepatic encephalopathy with associated confusion and obtundation.
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