Ian Latham, MS4
The Article: Mackenzie, David C., et al. "Test performance of point-of-care ultrasound for gastric content." The American journal of emergency medicine 37.1 (2019): 123-126.
The Idea: On occasion, it is clinically important to determine a patient’s last oral intake, particularly in the case of sedation for emergent or semi-elective procedures. We can often rely on the patient’s own recollection of their last intake, but some patients cannot provide this information or are unsure. In this situation, there are few modalities to identify patients who are high-risk for aspiration under sedation. In these cases, can bedside ultrasound accurately detect the presence or absence of gastric contents?
The Study: 45 healthy volunteers were randomized to fast for 10 hours or to ingest 50g of carbohydrates and 300mL of water before the study. Any subjects with conditions that may affect gastric emptying (history of gastric/esophageal surgery, diabetes, pregnancy, etc) were excluded. A sonologist trained in emergency ultrasound performed a study within ten minutes of oral intake, examining three gastric views (subxiphoid, right lateral decubitus, and left upper quadrant). The sonologist recorded an interpretation for each view and an overall impression. The images were later reviewed by two blinded emergency medicine physicians who interpreted each view and recorded a general impression.
The Results: Overall, bedside gastric ultrasound performed and interpreted by a trained sonologist was 92% sensitive and 85% specific. Performance was comparable between the subxiphoid and right lateral decubitus views, but the LUQ view was only 69% sensitive and was discordant from the other two views in 23% (n=10) of cases. Later reviews of the images had excellent sensitivity of more than 96%, but were only 35% specific. Performance of the LUQ view was once again poorer than the other two views.
The Takeaway: This study asks and answers a very simple question: can bedside ultrasound accurately detect the presence or absence of gastric contents? The results show that gastric ultrasound can be suitably sensitive for gastric contents, which is appropriate in the context of a quick screening test to determine which patients are at a high aspiration risk. The authors note a lack of experience in gastric ultrasound and the presence of gas bubbles in the stomach as limitations of the study, which may impact how well this study can be implemented broadly. Most importantly, the authors note that the data presented here do not support the delay of a critical procedure requiring sedation based on the outcome of a bedside gastric ultrasound, thus limiting the utility of these results. In an emergency department setting, it is rarely appropriate to delay sedation due of a patient needing an emergent procedure due to gastric contents, thus making a gastric ultrasound unnecessary. While it is interesting to see the discordant sensitivities of specific views of the stomach on ultrasound, more work will need to be done on gastric ultrasound to determine utility in an emergency department setting.