What pharmacologic interventions can be made to decrease the risk of aspiration?
Pharmacologic agents may be administered to decrease gastric volume (either by decreasing production or by increasing emptying), increase gastric pH, or increase LES tone.
· Metoclopramide, a derivative of procainamide, facilitates gastric emptying by causing gastric peristalsis and relax-ation at the pylorus. Metoclopramide also increases LES tone. It should be avoided in cases of bowel obstruction. Because it is a dopaminergic antagonist, it should be avoided in patients with Parkinson’s disease or depres-sion. It can also cause extrapyramidal side-effects. The positive effects of this drug are inhibited by narcotics, which delay gastric emptying.
· Cimetidine or ranitidine are competitive H2-blockers that will decrease basal gastric acid secretions that occur in response to gastrin and food, thereby increasing gas-tric pH. They should be administered 30–60 minutes prior to induction of general anesthesia.
· Sodium citrate is a non-particulate antacid that will increase gastric pH. A non-particulate formulation is important since aspiration of the particulate alkalis may also produce a chemical pneumonitis. One drawback of this antacid is that it must be taken orally, thereby increasing gastric volume. It should be administered within 30 minutes of the induction of general anesthesia.
· Omeprazole, rabeprazole, and lansoprazole are proton pump inhibitors that block H+-K+-adenosine triphos-phatase activity at the secretory surface of the parietal cells in the stomach. These drugs decrease the volume and increase the pH of gastric secretions.
· Glycopyrrolate, an anticholinergic, will increase gastric pH by inhibiting vagally mediated gastric acid produc-tion. Atropine, however, is ineffective.