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Less hocus, more POCUS:�Gastric Volume

MORGAN MORROW, DNAP, CRNA

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Lecture Objectives

1

Explain the use of point-of-care ultrasound in gastric volume assessment

2

Demonstrate use of gastric volume assessment in the perioperative patient

3

Identify various types of gastric contents (clear liquid versus solid food)

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Fasting Guidelines

NPO guidelines were established by the ASA to minimize the risk of pulmonary aspiration upon the induction of anesthesia prior to instrumentation or manipulation of the patient’s airway.

    • “Full stomach” is a major risk factor for aspiration
    • Aspiration is the leading cause of death from anesthesia airway events (pneumonitis, acute respiratory distress, multiple organ dysfunction, brain damage)

Unfortunately, guidelines are not “one size fits all”

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Fasting Guidelines

Co-existing conditions such as diabetes, hiatal hernias, ileus, trauma, enteral feedings, renal/hepatic dysfunction, or patients with difficult airways may not be appropriate candidates for traditional guidelines

    • Often, routine administration of prokinetic medications is not recommended

Stress, pain, use of opioids, and anxiety impacts mobility of digestive system

Full stomach plus loss of airway reflexes increases the risk of aspiration

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Severity of aspiration

VOLUME

TYPE

ACIDITY

BASAL GASTRIC VOLUME SHOULD BE LESS THAN 1.5 ML/KG TO BE “SAFE” IN FASTED PATIENTS

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Fasting Guidelines

  • Emerging research and ERAS protocols question traditional guidelines and often encourage patients to continue to consume clear liquid, carbohydrate-based drinks up to 2 hours preoperatively.

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Performing a gastric ultrasound

Low frequency, curved probe

Scan supine and right lateral decubitus

Measure in right lateral decubitus position

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POCUS utilization

Application of POCUS as a qualitative assessment can be utilized to answer the question, “does my patient have a full or empty stomach”

Some scenarios where further clarification of NPO status may be helpful include language barriers, decreased level of consciousness, comorbidities that prolong gastric emptying, when decided timing of an urgent versus emergent case

    • In a study by Cieslak et al. (2020), utilization of POCUS changed airway management plans in approximately 9% of case.

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POCUS Utilization

US IS USUALLY READILY AVAILABLE

GASTRIC ULTRASOUND IS MORE ACCURATE INFORMATION REGARDING STOMACH CONTENTS THAN THE ASSUMPTION OF FASTING HOURS

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Image acquisition

Next scan in right lateral decubitus (gastric contents gravitate to stomach antrum in this position!)

Initial scan in supine position to identify anatomy

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Empty Stomach

Clear Fluids

Thick Food

“Frosted Glass”

Hyperechoic food= increased aspiration risk

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Full Stomach, Right Lateral Decubitus Position

Liver

Lunch

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Calculation of allowable gastric volume

  • Allowable gastric volume=27 + (14.6 X Cross-sectional area) – (1.28X age)

27 + (14.6 X 13.7175) – (1.28 X 36)

27+200.3-48.64=179 mL of lasagna and Reece’s peanut butter cups

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From:

Perlas, A., Arzola, C., & Van de Putte, P. (2018). Point-of-care gastric ultrasound and aspiration risk assessment: a narrative review. Canadian Journal of Anesthesia, 65, 437-448.

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References

  • Cieslak, J. R., Rice, A. N., Gadsden, J. C., & Vacchiano, C. A. (2020). Does ultrasonographic measurement of gastric content influence airway management decisions? AANA Journal, 88(2), 107-113.
  • El-Bodghadaly, K., Kruisselbrink, R., Chan, V., & Perlas, A. (2016). Images in Anesthesiology: Gastric Ultrasound. Anesthesiology, 125(3), 595.
  • Perlas, A. (n.d.) Gastric Ultrasound. USRA. http://www.usra.ca/regional-anesthesia/specific-blocks/pocus/gastric.php
  • Perlas, A., Arzola, C., & Van de Putte, P. (2018). Point-of-care gastric ultrasound and aspiration risk assessment: a narrative review. Canadian Journal of Anesthesia, 65, 437-448.
  • Shorbagy, M.S., Kasem, A. A., Gamal Eldin, A. A. et al., (2021). Routine point-of-care ultrasound (POCUS) assessment of gastric antral content in traumatic emergency surgical patients for prevention of aspiration pneumonitis: an observational clinical trial. BMC Anesthesiology, 21(140), 1-10. DOI: https://doi.org/10.1186/s12871-021-01357-y
  • Soni, N.J., Arntfield, R., & Kory, P. (2020). Point of Care Ultrasound. Elsevier.

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Less Hocus, More POCUS:�Airway management

MORGAN MORROW, DNAP, CRNA�

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Utility of POCUS in the airway

Pre-intubation screening for difficult laryngoscopy

Selection of proper ETT size

Confirmation and depth of ETT placement

Detect LMA malrotation

Assist in surgical airway access

Predict post extubation obstruction (edema, stridor, etc.)

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Prediction of difficult laryngoscopy

Visualization of the hyoid bone

    • Inability to visualize using sublingual approach predicts difficult intubation with high sensitivity and specificity

Hyomental distance

    • Shorter hyomental distance ratio in morbidly obese patient predicts difficult intubation with high sensitivity

Anterior neck thickness

    • At the level of vocal cords, hyoid bone, throhyoid membrane
    • Pretracheal tissue exceeding 28+/-2.7mm thickness in obese patients=difficult laryngoscopy

Tongue thickness and tonguethickness:thyromental distance ratio

    • >6.1cm tongue thickness and higher tongue thickness:thyromental distance ratio is predictive of difficult airway

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References

  • Adi, O., Kok, M.S., & Abdull Waha, S. F. (2019). Focused airway ultrasound: an armamentarium in future airway management. Journal of Emergency and Critical Care Medicine, 31(3), 1-10
  • Koundal, V., Rana, S., Thakur, R., Chauhan, V., Ekke, S., & Kumar, M. (2019). The usefulness of point of care ultrasound (POCUS) in preanaestetic airway assessment. Indian Journal of Anesthesia, 63(12), 1022-1028.