Should drugs be administered to empty the stomach or change gastric acidity or volume before the administration of an anesthetic?

Should drugs be administered to empty the stomach or change gastric acidity or volume before the administration of an anesthetic?

Studies regarding differences in the resting gastric volume between the inpatient and ambulatory population have yielded conflicting results. Whereas some anesthesiol-ogists administer liquid antacids before the induction of anesthesia, no evidence supports the notion that every patient must receive a soluble agent (0.3 molar sodium citrate, 30 ml). A soluble antacid is substituted for the conventional nonabsorbable antacid containing aluminum, magnesium, or calcium hydroxide to avoid the severe chemical pneumonitis that may result from aspiration of these particulate substances. Other pharmacologic agents include the H₂-receptor blockers (ranitidine or famoti-dine), which inhibit gastric acid production and decrease gastric volume. Mental confusion has been reported after intravenous administration of cimetidine in geriatric patients. Ranitidine is more potent and specific and has a longer duration of action than cimetidine. Metoclopramide increases the tone of the lower esophageal sphincter as well as facilitating gastric emptying. However, it does not guar-antee a stomach free of gastric contents. It also possesses anti-emetic properties. Metoclopramide, in conjunction with an H₂-receptor blocker, may be more efficacious. However, the routine use of any of these drugs in patients without specific risk factors is not currently recommended.

Diabetes mellitus with evidence of autonomic dysfunc-tion or gastric atony, documented hiatal hernia, a history of symptomatic gastroesophageal reflux, pregnancy, signifi-cant obesity, acute abdomen, or current opioid use or abuse are examples of diseases or conditions that appear to increase the incidence of aspiration during induction or emergence from general anesthesia or during heavy sedation. Therefore, prophylaxis in these situations is recommended. There is no advantage to administration of triple prophylaxis with H₂-receptor antagonists, soluble antacids, and metoclo-pramide. If prophylaxis with an H₂-blocker is employed, it should be given 1–2 hours preoperatively. Another effective regimen combines metoclopramide on the morning of sur-gery and a nonparticulate antacid immediately prior to surgery.

Despite the administration of pharmacologic agents and imposition of fasting, significant amounts of acidic gastric contents may still be present. Fortunately, aspiration of gastric material remains a relatively rare occurrence. If a patient is observed to aspirate and if symptoms of cough, wheeze, or hypoxemia while breathing room air do not develop within 2 hours, the development of significant respiratory sequelae is unlikely. Therefore, reliable and otherwise healthy ambulatory patients can probably be discharged after several hours of observation in the postanesthesia care area with the proviso that they immedi-ately contact their physician at the onset of any symptoms.