GASTRIC ULTRASOUND. A Point-of-care tool for aspiration risk assessment.

Transcription

1 GASTRIC ULTRASOUND A Point-of-care tool for aspiration risk assessment edu@gastricultrasound.org

2 Indications Any clinical situation where aspiration risk is uncertain. For example: Lack of adherence to fasting instructions: emergency/urgent procedure miscommunication Unreliable / unclear fasting history: altered sensorium language barrier cognitive dysfunction Potential delay in gastric emptying: pregnancy/labour diabetes severe liver or kidney dysfunction neuromuscular disorders

3 Scanning Technique Scan the epigastrium in a sagittal plane Sweep the transducer from the left to the right subcostal margins Identify the gastric antrum see anatomy Patient position: Start in the supine position Follow with the right lateral decubitus (RLD). Never call an empty stomach based on the supine position alone

4 Anatomy The gastric antrum: Is the most amenable to sonographic examination and accurately reflects the content of the entire stomach Hollow viscus with a prominent multi-layer wall Between the liver (anteriorly) and the pancreas (posteriorly) Important landmarks: Left lobe of the liver Pancreas Aorta Inferior vena cava Superior mesenteric artery and vein Is usually located superficially (3-4 cm) Sma Blue line: scanning plane; A: antrum; Ao: aorta; L: liver; P: pancreas; Sma: superior mesenteric artery

5 Image GASTRIC WALL Characteristic five-layered wall Sets the organ apart from other hollow viscus Best appreciated with a high-frequency transducer in the fasting state. 1: serosa; 2: muscularis propriae; 3: submucosa; 4: muscularis mucosa; 5: mucusal air interface

6 Gastric Content Types

7 Empty Stomach The antrum has no appreciable content in both supine and RLD (Grade 0 antrum) It appears flat and collapsed or with a round-to-ovoid shape ( bull s eye or target pattern) A: antrum; Ao: aorta; D: diaphragm; L: liver; P: pancreas; R: rectus abdominis muscle; Sma: superior mesenteric artery

8 Solid Early Stage Stomach Content The antrum appears distended with thin walls The content is of high or mixed echogenicity Specific patterns: Frosted-glass pattern (usually shortly after a solid meal). It is due to a mix of air and solid along the anterior wall, blurring the posterior wall and deeper structures A: antrum; Ao: aorta; L: liver; R: rectus abdominis muscle

9 Solid Late Stage Stomach Content Heterogeneous, particulate content (usually after 1-2 hours following a solid meal) Homogeneous hyperechoic content: characteristic of dairy products or particulate fluids Milk curdles and can have a typical biphasic (hyperechoic/hypoechoic) appearance (see additional material) A: antrum; Ao: aorta; L: liver; P: pancreas; R: Rectus Abdominis muscle; S: spine; Sma: superior mesenteric artery

10 Clear Fluid Stomach Content The antrum is round and distended with thin walls The content appears anechoic or hypoechoic The size of the antrum is proportional to the gastric volume The antrum will appear larger in the RLD compared to the supine position A: antrum; Ao: aorta; L: liver; P: pancreas; R: Rectus Abdominis muscle; D: Diaphragm

11 Fluid with Air Bubbles Stomach Content Special pattern: Starry night (multiple air bubbles on a hypoechoic background) usually seen shortly after ingestion of clear fluids or effervescent drinks A volume assessment can differentiate a low (normal) quantity of baseline gastric secretions from a higher (non-fasting)volume A: antrum; Ao: aorta; L: liver; P: pancreas; R: Rectus Abdominis muscle; D: Diaphragm; S: Spine; Sma: Superior Mesenteric Artery

12 Gastric Volume Assessment The cross-sectional area of the antrum (CSA) has a linear correlation with the gastric volume To measure the CSA: Identify the antrum at the level of the aorta in the RLD Obtain a still image of the antrum at rest (between peristaltic contractions) Use the free-tracing tool of the ultrasound machine to measure the CSA including the full thickness of the gastric wall (from serosa to serosa) Use a predictive model to assess the gastric volume The following model and related table are applicable to non-pregnant adults for gastric volumes up to 500 ml: VOLUME (ML) = X RIGHT-LAT CSA 1.28 X AGE

13 Gastric Volume Chart VOLUME (ML) = X RIGHT-LAT CSA 1.28 X AGE

14 Antral Grading Systems (Grades 0 2) Most fasted individuals (> 95 %) present a grade 0 or 1 antrum which correlates with low gastric volume A grade 2 antrum is rarely seen in fasted patients and is suggestive of significant gastric volume

15 Interpretation of Findings Defining the type of content (empty, clear fluid or thick fluid/solid) is the first step. An empty stomach s suggestive of low aspiration risk. Solid content is suggestive of a high aspiration risk. Clinical data suggest that a volume of up to 1.5 ml/kg (100 ml for the average adult) is normal in fasted patients

16 Limitations Gastric ultrasound findings may be inaccurate in subjects with abnormal underlying gastric anatomy. For example: previous gastric resection or bypass gastric band in situ previous fundoplication large hiatus hernia

17 Empty

18 Clear Fluid

19 Clear Fluid with Air Bubbles

20 Solid Late Stage

21 Solid Early Stage

22 Acknowledgements All content within this PowerPoint is derived from Gastric Ultrasound.org with permission. Please visit the site and see more. Links: