Gastrointestinal Function

Another organ system affected during neuraxial block is the gastrointestinal tract. Nausea and vomiting may be associated with neuraxial block in up to 20% of patients and are primarily related to gastrointestinal hyperperistalsis due to unopposed parasympathetic (vagal) activity.^[51] Atropine is effective in treating nausea associated with high (T5) subarachnoid anesthesia. ^{[52] [53]} This gastrointestinal hyperperistalsis has the advantage of providing excellent surgical conditions because of a contracted gut. An often-cited advantage of regional anesthesia in patients with compromised gastrointestinal function (e.g., hepatic dysfunction) is that less physiologic impairment is possible compared with general anesthesia. Nevertheless, it appears that if intra-abdominal surgery is performed, the magnitude of decrease in hepatic blood flow parallels the site of operation, rather than anesthetic technique chosen. The decrease in hepatic blood flow during spinal anesthesia parallels the decrease in mean arterial blood pressure.^[54] When epidural analgesia is continued into the postoperative period, there may be a protective effect on the gastric mucosa because intramucosal pH is higher during postoperative epidural analgesia than with systemic analgesia.^[55]