THE AIRWAYS AND GASTRIC CONTENTS IN OBESE PATIENTS The Airways and Gastric Contents in Obese Patients

Classically, obese patients have been considered as having a potential full stomach, and it has been believed that abdominal pressure and gastric volume have a similar behavior to that of pregnant patients. However, in parturients, gastric emptying is slowed, not only as a consequence of the anatomical changes secondary to the cephalad displacement of the stomach by the uterus, but also due to the actions of progesterone. In 1983, Wright1 demonstrated that gastric emptying in obese patients is faster than in non-obese patients, especially in males. However, the anesthetic literature still considers obese patients as having a potential full stomach. Those statements are based, mainly, on a study by Vauhan’s2 who, in 1975, observed greater gastric contents and lower pH in obese patients. Based on the study of Roberts and Shirley3, published in 1974, who reported gastric contents greater than 25 mL and pH lower than 2.5 as risk factors for aspiration of gastric contents, Vaughan reported that 75% of obese patients (compared to none of non-obese patients) presented this relationship. Methodologically, the study of Vaughan failed, as pointed by Schreiner4, by the blind aspiration of the stomach to determine the volume of the gastric contents. Very few studies correlating the body mass index and gastric contents can be found in the literature. Several studies published after 1975 reinforced the concept that obese patients should be considered as having a potential full stomach, but those statements are based on the study by Vaughan5-9. In the present review, we tried to analyze the literature looking for more studies on the subject and its repercussions on the anesthetic technique, especially on techniques to access the airways.