{'fraction_non_alphanumeric': 0.01846337105419893, 'fraction_numerical': 0.01171332142148104, 'mean_word_length': 5.699468085106383, 'pattern_counts': {'":': 0, '<': 1, '<?xml version=': 0, '>': 1, 'https://': 0, 'lorem ipsum': 0, 'www.': 1, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 1, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
The Hidden Value of Ultrasound?

December 2018 • Volume 127 • Number 6 www.anesthesia-analgesia.org 1285 DOI: 10.1213/ANE.0000000000003748 Of the many recent advances in anesthesia technology, real-time 2-dimensional ultrasound visualization is arguably one of the most prominent. Expert use of ultrasound can allow diagnosis of intrathoracic and intraabdominal abnormalities,1 assess and monitor cardiac and circulatory function, identify potentially life-threatening conditions, and facilitate invasive procedures. In anesthesia, ultrasound has revolutionized the diagnosis of cardiorespiratory abnormalities, and performance of both peripheral nerve blocks and central venous access procedures.1 Few technologies have become as indispensible as ultrasound for improving the safety and efficiency of such procedures. The effect of widespread use of ultrasound on the blind performance of those same procedures, however, has not been as clearly identified. With respect to central line insertion, for example, use of ultrasound may worsen subsequent performance of the same procedure without ultrasound guidance, in part, because clinicians may lose familiarity with the blind procedure through lack of practice.2 Conversely, ultrasound may improve the success and complication rates of central line insertion without ultrasound guidance by providing better feedback during vessel localization and missed attempts and allowing insight into how complications occur. Multiple studies document the surprisingly variable course of vessels such as the internal jugular vein, suggesting that one potential role of ultrasound localization may be to teach clinicians to efficiently identify the correct needle path. It is not an impossible leap to imagine that with ultrasound feedback, clinicians might also refine their ability to localize the vein without ultrasound. Few data exist to determine whether ultrasound use improves or degrades subsequent performance of the same procedure without ultrasound. Comparative studies from early and later periods during the ultrasound era find similar carotid puncture and failure rates in control groups, suggesting little deterioration over time. However, such studies were not designed to identify atrophying “blind” central line insertion skills and do not shed light on this issue. Such a question is important because it informs the role of ultrasound in procedural teaching and learning, and the relative safety of not using ultrasound. In this issue of Anesthesia & Analgesia, You-Ten et al3 study the effect of including ultrasound localization on the efficacy of a simulation-based training program to identify the midpoint of the cricothyroid membrane. The stated goal was to familiarize learners with aspects of performing a successful cricothyroidotomy. After developing a teaching course using both didactic presentations and guided practice (on each other), You-Ten et al3 randomized 15 anesthesia residents, fellows, and assistants to receive the training course with and without the addition of ultrasound guidance. In groups without ultrasound guidance, an instructor would demonstrate the location of the cricothyroid membrane on a model and participants would practice on each other until the instructor confirmed their ability to correctly identify the midpoint of the cricothyroid membrane. In groups with ultrasound assistance, an instructor would use a 10–5 linear array transducer and portable ultrasound machine to demonstrate the location and dimensions of the cricothyroid membrane and to guide manual palpation of the membrane. Participants would practice ultrasoundguided manual palpation until their ability to correctly identify the midpoint of the cricothyroid membrane using ultrasound was confirmed by the instructor. Each participant in both groups was then assessed by their ability to identify the midpoint of the cricothyroid membrane in 10 volunteers using palpation only. The midpoint was preidentified using ultrasound, marked with invisible ink, and accuracy was defined as the distance between the midpoint identified by the participant and the preidentified location. The authors powered their study using a baseline 70% accuracy rate and an anticipated 30% increase in accuracy to 90% with ultrasound. The results clearly favored the ultrasound group. After adjustment for clinical experience, model characteristics, and previous airway ultrasound training, participants who received ultrasound training were considerably more accurate (defined as <5 mm from the preidentified location). Overall distance from target (including misses >5 mm from the target) was also lower in participants trained using ultrasound. The result by You-Ten et al3 is consistent with studies of ultrasound-assisted learning in other domains. Existing data suggest that ultrasound training can improve the subsequent blind estimation of liver size,4 femoral artery location,5 and biceps tendon.6 In addition, in patients with difficult anatomic The Hidden Value of Ultrasound?