Ultrasonic Assessment of the Cricothyroid Membrane Better than Landmarking? Dr ZHANG Jinbin MMED (Anaes) Consultant Department of Anaesthesiology, Intensive Care and Pain Medicine Tan Tock Seng Hospital, Singapore
Outline Anatomy n Locating the cricothyroid membrane (CTM) using ultrasound n Limitations of landmark palpation n Is ultrasound useful? n
Why is the Cricothyroid Membrane (CTM) important? n Surgical airway access n Transtracheal injection of LA
Anatomy of the CTM
Conventionally… n Landmark Technique n Between the thyroid and cricoid cartilages Superior Thyroid artery Superior Laryngeal artery Cricothyroid artery
Limitations of Palpation n Poorly discernible landmarks Thick neck n Thick subcutaneous tissue n Obese patients n Females n n Distorted anatomy Previous radiotherapy to neck n Tracheal deviation due to head & neck tumours n Infection n
Landmark palpation is inaccurate n 6 volunteers n BMI from 24 -53 kg/m 2 n 18 participants n 30% within defined area 10% on target n n n 51% missed above 35% missed below Elliot et al. Anaesthesia 2010; 65
Landmark palpation is inaccurate n 56 females, child-bearing age n n 24 participants n n n 17 anesthesiologists 7 OB/GYN trainees Neutral: n n n 15 obese (mean BMI 40. 5 + 9. 9 kg/m 2) 25% in non-obese 0% in obese group Hyperextended: n 29% vs 6% Aslani et al. Anesth Analg 2012: 114
n Range of values extensive n Ease of ultrasonic assessment did not differ with BMI
Landmark palpation is inaccurate n NAP 4 study 15/29 (52%) of the cricothyroidotomies performed by anaesthetists failed n 100% success in those done by surgeons n
How can Ultrasound help us?
Ultrasound – Tissue air interface M. S Kristensen, W. H. L Teoh. Airway Management 1 st Edition, Springer 2014
Advantages Safe n Quick n Reproducible n Non-invasive n Portable n Available by bedside n Gives dynamic images n
Localize Cricothyroid membrane
Ultrasound Helps Ease of image acquisition not affected by BMI n Quick image acquisition n 24. 32 s + 20. 18 s (95% CI 18. 59 – 30. 05) Nicholls et al. Am J Emerg Med 2008; 26 Poorly discernible landmarks n Easier to locate CTM, retention of training n Barbe et al. Ann Fr Anesth Reanim 2014; 33
Limitations of Ultrasound Expertise n Subcutaneous air – image interference n Preparation and boot-up time? n Role for Emergency CICO? n Minimum training required? n
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