Chapter 34

• The hepatic artery supplies 45–50% of the liver’s oxygen requirements and the portal vein supplies the remaining 50–55%.
• All coagulation factors—with the exception of factor VIII and von Willebrand factor—are produced by the liver. Vitamin K is a necessary cofactor in the synthesis of prothrombin (factor II) and factors VII, IX, and X.
• Liver tests that measure hepatic synthetic function include serum albumin, prothrombin time (PT, or international normalized ratio [INR]), cholesterol, and pseudocholinesterase.
• Albumin values less than 2.5 g/dL are generally indicative of chronic liver disease, acute stress, or severe malnutrition.
• The PT, which is normally 11–14 s (depending on the control), measures the activity of fibrinogen, prothrombin, and factors V, VII, and X.
• If an adequate intravascular volume is maintained, spinal and epidural anesthesia decrease hepatic blood flow primarily by lowering arterial blood pressure, whereas general anesthesia usually decreases it through reductions in blood pressure and cardiac output and sympathetic stimulation.
• The surgical stress response is characterized by elevated circulating levels of catecholamines, glucagon, and cortisol. Mobilization of carbohydrate stores and proteins results in hyperglycemia and a negative nitrogen balance (catabolism), respectively.
• Anesthetic interactions with bile formation and storage have not been reported. However, all opioids can potentially cause spasm of the sphincter of Oddi and increase biliary pressure (fentanyl > morphine > meperidine > butorphanol > nalbuphine).
• When the results of liver tests are elevated postoperatively, the usual cause is underlying liver disease or the surgical procedure itself.
• Epidemiological studies have identified several risk factors that are associated with halothane-associated hepatitis, including middle age, obesity, female sex, and a repeat exposure to halothane (particularly within 28 days).

The liver, which weighs approximately 1500–1600 g in adults, is the largest organ in the body. It is responsible for a seemingly endless number of complex and interrelated functions. Fortunately, because of the liver’s large functional reserves, clinically significant hepatic dysfunction following anesthesia and surgery is uncommon. Such dysfunction is limited primarily to patients with preexisting hepatic impairment and to those with rare idiosyncratic reactions to halogenated volatile anesthetics. This chapter reviews normal hepatic physiology, laboratory evaluation of hepatic function, and the effects of anesthesia on hepatic function. The anesthetic management of patients with liver disease is discussed in Chapter 35.

The liver is separated by the falciform ligament into right and left anatomic lobes; the larger right lobe has two additional smaller lobes at its posterior–inferior surface, the caudate and quadrate lobes. In contrast, surgical anatomy divides the liver based on its blood supply. Thus the right and left surgical lobes are defined by the point of bifurcation of the hepatic artery and portal vein (porta hepatis); the falciform ligament therefore divides the left surgical lobe into medial and lateral segments. Surgical anatomy defines a total of eight segments.

The liver is made up of 50,000–100,000 discrete anatomic units called lobules. Each lobule is composed of plates of hepatocytes arranged cylindrically around a centrilobular vein (Figure 34–1...

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