Pulmonary Aspiration of Gastric Contents: Anesthesiologists Worry About Mendelson’s Syndrome

Pulmonary aspiration of gastric contents is a proverbial complication of anesthesia patient care! Because it is of such clinical significance to anesthesiologists, the study of aspiration of gastric contents has a long history: (reference 1)

• 1781 – John Hunter performed the first scientific experiments investigating the pathophysiology of aspiration. (Reference 1)

• 1848 – Sir James Simpson identified pulmonary aspiration as a most probable cause of the first recorded anesthetic death of Hannah Greener. (Reference 1)

• 1946 – Curtis Mendelson, an obstetrician, “became the first investigator to rigorously study the pathogenesis of the disease [gastric acid aspiration] using both patient case reports and experimental animals.” (Reference 2)

Scientific investigation of the clinically relevant safety issues related to aspiration of gastric contents continues to date; the May issue of Anesthesiology presents current clinical research in this area by Lionel Bouvet et al. in an article entitled “Clinical Assessment of the Ultrasonographic Measurement of Antral Area for Estimating Preoperative Gastric Content and Volume”. (Reference 3)

The authors set out to answer several questions including whether a) clinical non-invasive ultrasonographic sizing of the stomach can be reliably accomplished, b) there is a relationship between the measured size of the stomach and its contents quantitatively, and c) this clinically collected data can alert anesthesiologists to the patient at risk (gastric volume 0.4-0.8 ml/kg) for aspiration of gastric contents. (Reference 4, 5) Bouvet and colleagues studied 183 patients; preoperative ultrasonographic measurement of the antral cross-sectional area (CSA) was followed by the induction of general endotracheal anesthesia and active suctioning of the stomach to measure the quantity of its contents. The gastric dimensions and volumes were compared with attention paid to whether the surgery was elective or emergent. Measurement of the antral CSA was possible in 180/183 patients. The mean volume of gastric aspirate for all patients was 57+43 ml and, as would be anticipated, was increased in emergency (69+51 ml) compared to elective (23+19 ml) surgical patients; regurgitation or aspiration did not occur in any studied patient. Antral CSA was well correlated linearly with volume (the correlation coefficient was 0.72) and was significantly increased in emergency compared to elective surgical patients. In this study, antral gastric measurement established a cross-sectional area of 340 mm2 as diagnostic for the “risk stomach”, i.e., the presence of gastric volume >0.8 ml/kg, which was the setting for 60 of 76 (78.9%) emergency and 3 of 104 (2.9%) elective surgical patients.

When you are the clinical anesthesiologist considering the likelihood that your patients are at risk for aspiration of gastric contents, you have at least 3 basic approaches to follow: a) base the risk analysis and subsequent clinical care solely on clinical history, b) assume there is a “risk stomach” and proceed with clinical management including a rapid sequence induction, an “awake” intubation or some method to empty the stomach prior to anesthetic induction, or c) perform an preanesthetic ultrasonographic measurement of the antral CSA to indicate whether your patient requires special precautions to reduce a more likely occurrence of gastric regurgitation and pulmonary soiling. Do you utilize ultrasonographic measurement of the gastric antral cross-sectional area, a strategysuggested as feasible by Bouvet and colleagues? How do you make sure that a “risk stomach” is not present in your patients? Share with your colleagues and our readers the gastric aspiration safety net that you employ.

References
1. Knight Paul R (September 1999). “Curtis L. Mendelson, M.D.: Aspiration Investigator (1913- ). ASA Newsletter.
2. Mendelson CL: The aspiration of stomach contents into the lungs during obstetric anesthesia. American Journal of Obstetrics and Gynecology 1946; 52: 191-205
3. Bouvet L, Mazoit JX, Chassard D, Allaouchiche B, Boselli E, Benhamou D: Clinical Assessment of the Ultrasonographic Measurement of Antral Area for Estimating Preoperative Gastric Content and Volume. Anesthesiology 2011; 114: 1086-92
4. Engelhardt T, Webster NR: Pulmonary aspiration of gastric contents in anaesthesia. Br J Anaesth 1999; 83:453– 60
5. Raidoo DM, Rocke DA, Brock-Utne JG, Marszalek A, Engelbrecht HE: Critical volume for pulmonary acid aspiration: Reappraisal in a primate model. Br J Anaesth 1990; 65: 248 –50