Measurement of gastric contents

Fasting from midnight – the history behind the dogma

The purpose of this chapter is to review historical fasting guidelines and how the dogma of fasting from midnight arose and came to be challenged by randomized clinical trials of preoperative clear liquids versus overnight fast. Medical and anaesthesia textbooks and journals from the 19th and 20th centuries were consulted, and the results of clinical trials and the reaction to them are reviewed. The dogma appeared to result from extrapolation of pulmonary aspiration risk in 'full-stomach' emergency cases to healthy elective cases. This was reinforced when 25 mL in the stomach, present in half of all healthy fasting patients, was used as a surrogate marker for high risk of aspiration. Subsequent large-scale studies showed the risk to be minimal. Meta-analysis of randomized clinical trials demonstrated the safety of clear oral liquids until 2 hr preoperatively in healthy patients undergoing elective surgery. Reaction was cautious but led to eventual acceptance of evidence-based fasting guidelines.

Metoclopramide in trauma CT scanning: preventing emesis of oral radiographic contrast

Vomiting of gastric contents is common among multisystem trauma patients and may cause significant morbidity. A study was conducted to examine whether metoclopramide (Reglan), an antiemetic and promotility agent, could decrease vomiting after administration of oral radiographic contrast in stable multisystem trauma patients undergoing computed tomography (CT) of the abdomen ("trauma CT patients"). The charts of 193 patients listed in the Duke Trauma Registry who underwent abdominal CT scanning from January, 1992 until February, 1993 were reviewed. The emergency department record was reviewed for documentation of vomiting, use of intravenous metoclopramide, and other potential confounders of vomiting such as age, pharmacologic paralysis, and head injury as measured by the Glasgow Coma Scale (GCS). Patients who received intravenous metoclopramide were six times less likely to vomit after administration of oral radiographic contrast than those who did not receive the drug. This effect increased to a twelvefold protective effect after correcting for age, pharmacologic paralysis, and GCS. These preliminary findings strongly suggest that routine use of metoclopramide may prevent vomiting of gastric contents after administration of oral radiographic contrast in trauma CT patients. A future prospective study is recommended to confirm these results.