- 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
- 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