Does Cricoid Pressure Reduce the Risk of Aspiration?

Gastric-to-pulmonary aspiration during induction of anesthesia remains a significant risk in the modern practice of anesthesia.(1) Macroaspiration (grossly visible aspiration) has been clearly associated with severe pulmonary injury.(1-4) More recently, microaspiration (aspiration without grossly visible gastric material) has also been associated with significant morbidity.(2) Specifically, microaspiration has been associated with acute respiratory distress syndrome (ARDS)(5), ventilator associated pneumonia (VAP)(6) and acute respiratory failure due to bronchoconstriction and ventilation-perfusion mismatching. Pepsin A has been shown to be a very specific biochemical marker for gastric-to-pulmonary aspiration.(7) In our previous studies, we demonstrated the rate of microaspiration in normal elective surgical patients without risk factors for aspiration was 4% as detected by the ELISA assay for pepsin A.(8) This compared with a rate of 12.5% in patients with risk factors for microaspiration including obesity, GERD (gastroesophageal reflux disease) and diabetes. One proposed technique to prevent gastric-to-pulmonary aspiration is cricoid pressure. Recently, there has been growing evidence which calls into question the effectiveness of cricoid pressure. Radiologic studies by Smith et al yield indirect evidence to suggest that cricoid pressure may not reliably occlude the esophagus.(9,10) Currently, cricoid pressure for patients with risk factors for microaspiration (obesity, GERD and diabetes) is used commonly but inconsistently.(11) By using the same sampling and analysis techniques employed in our previous microaspiration studies, the currently proposed study will provide a very sensitive and specific assessment of the effectiveness of cricoid pressure to prevent aspiration during elective induction of anesthesia and intubation. Our proposed study would enroll patients with risk factors for microaspiration who are scheduled to undergo high-risk (for pulmonary complications) elective surgery requiring endotracheal intubation. We will exclude those with risk factors for macroaspiration (including bowel obstruction, non-fasting status and esophageal pathology associated with increased risk for macroaspiration such as achalasia and hiatal hernia), because cricoid pressure remains the standard of care for those at risk for macroaspiration at our institution. Those patients enrolled will be randomized to receive cricoid pressure versus no cricoid pressure. Immediately following elective intubation, a sample of tracheal secretions from each patient will be obtained and the pepsin A concentration determined. The primary outcome will be the rate of microaspiration determined by the presence of pepsin A in the trachea. Secondary outcomes of interest will be rates of postoperative pulmonary complications including acute respiratory distress syndrome (ARDS) and hospital-acquired pneumonia (HAP). The findings of this study will provide the most direct evidence yet regarding the effectiveness of cricoid pressure for the prevention of gastric-to-pulmonary aspiration during induction of anesthesia and endotracheal intubation. Ultimately, the findings of this study will improve patient safety by providing accurate prospective evidence regarding the effectiveness and safety of cricoid pressure in this setting, and will further explore the clinical significance of microaspiration.