title: Comparison of the incidence of combined "risk factors" for gastric acid aspiration: influence of two anesthetic techniques.
abstract: Gastric fluid pH and volume were studied on induction of anesthesia, during maintenance and at the end of the anesthesia in 50 elective surgical patients. All the patients were premedicated with meperidine, 1 mg/kg, and atropine 0.006 mg/kg, administered intramuscularly 45 minutes before induction of anesthesia. Half of the patients had incremental doses of meperidine; the other half had enflurane 1% to 2%; all had 70% nitrous oxide in oxygen during anesthesia maintenance. The incidence of a gastric fluid pH below 2.5 was 68% at the time of induction of anesthesia, 30% after 1 hour anesthesia, and 60% at the end of anesthesia. The incidence of a combination of pH below 2.5 and a volume above 25 ml was 30% on induction and 50% at the end of the anesthetic. There was no difference between the results in the two groups. It was concluded that although there was a decrease of gastric acidity during the anesthetic, the incidence of risk factors for aspiration pneumonitis at the end of the operation is at least as great as that on induction. Emptying the stomach before extubation may decrease this risk.
mesh_terms: D000758:Anesthesia / Q000009:adverse effects*; D004737:Enflurane; D005744:Gastric Acid / Q000378:metabolism*; D005745:Gastric Acidity Determination; D006801:Humans; D001239:Inhalation; D008614:Meperidine; D009609:Nitrous Oxide; D011014:Pneumonia / Q000139:chemically induced; D012119:Respiration; D012306:Risk
chemical_list: D004737:Enflurane; D008614:Meperidine; D009609:Nitrous Oxide