Effects of Anesthesia on Gastrointestinal System

Effects of Anesthesia on Gastrointestinal System

Effects of Anesthesia on the Liver

a. Premedications with morphine, scopolamine, atropine or a barbiturate will usually not change hepatic blood flow. Chronic treatment with barbiturates will increase hepatic blood flow as well as induce hepatic enzymes.

b. Spinal or epidural anesthesia to a mid-thoracic level will result in a 20-25% decrease in hepatic blood flow due predominantly to lower systemic blood pressure

c. General Anesthesia with a barbiturate, narcotic, nitrous oxide, and relaxant seem to have little or no effect on hepatic blood flow, as long as anesthesia is sufficiently deep and patients are normocarbic. Sympathetic discharge from light anesthesia will cause vasoconstriction and decreased hepatic blood flow. Methoxyflorane produces the most marked decrease in hepatic blood flow among volatile agents followed ( in descending order by ) halothane, enfurane, and isoflurane. Halothane has been documented angiographyically to cause hepatic artery spasm in some patients. The metabolism and clearance of some drugs (eg, fentanyl, phenytoin, verapamil) appear to be impaired by halothane

d. Other Factors causing decreased hepatic blood flow include: alph-adrenergic agonists, beta blocker, hypocarbia, positive-pressure ventilation and surgical manipulation of the abdomen.( both by direct compression of vessels and stimulation of splanchinic nerves)

e. Narcotics: Morphine, codeine and their synthetic derivatives can cause spasm of sphincter of Oddi and the bile ducts.