Dalesio, Nicholas M. MD*; Kattail, Deepa MD*; Ishman, Stacey L. MD, MPH, FAAP†; Greenberg, Robert S. MD*
From the *Department of Anesthesiology and Critical Care Medicine, The Johns Hopkins University; and †Departments of Otolaryngology—Head and Neck Surgery, Pediatrics and Internal Medicine—Division of Pulmonary and Critical Care Medicine, and Anesthesiology and Critical Care Medicine, and Center for Snoring and Sleep Surgery, Johns Hopkins School of Medicine, Baltimore, Maryland.
Accepted for publication May 28, 2013.
The authors declare no conflicts of interest.
Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's Web site.
Address correspondence to Nicholas M. Dalesio, MD, Department of Anesthesiology and Critical Care Medicine, The Johns Hopkins University, 1800 Orleans St., Room 6368, Baltimore, MD 21287. Address e-mail to Ndalesi1@jhmi.edu.
Advancements in ultrasonography and increasing familiarity with its use in the operating room (vascular access and regional neural blockade) suggest its feasibility as an adjunct in pediatric airway evaluation and intervention. We report 3 cases demonstrating the usefulness of ultrasound techniques in this setting. We show key elements of airway anatomy, noninvasive observation of vocal cord motion, and percutaneous periglottic steroid injection via the cricothyroid membrane in 3 different patients. This report reveals the possible usefulness of ultrasound imaging in clinical anesthesia care, specifically airway management, in children.
Evaluation of the pediatric airway is critical for safe, effective, and efficient management of routine and rare conditions involving the oro- and hypopharynx, as well as the larynx and trachea. Comprehensive assessment of the airway often requires general anesthesia, exposing the patient to potential risks of medications and clinical situations. Definitive evaluation involves either direct visualization under anesthesia or imaging modalities, such as computed tomography, with the added risk of radiation exposure. Patients with airway pathology, such as subglottic stenosis, require frequent evaluation and treatment, necessitating repeated exposure to anesthetics and/or radiation.
Ultrasonography, a technology widely used to assess anatomic and dynamic changes inside the body, is a nonradiating, well-tolerated, and readily available technology that permits image acquisition and real-time evaluation of the anatomy. Ultrasonography is widely used in various aspects of clinical medicine, including invasive procedures, such as vascular catheter insertion and regional anesthetic nerve blockade. Advancements and developments in ultrasound technology should now allow for accurate and descriptive evaluation of the pediatric airway, including assessment of the static and dynamic anatomical features as well as an adjunct to real-time visualization of airway interventions. In addition, the readily available ultrasound devices in the clinical setting, as well as the increasing familiarity of practitioners in the bedside use of the technology, puts it in position for consideration in the management of the pediatric airway. We report 3 patients in whom we demonstrate the feasibility of using ultrasound to identify key anatomic features, static and moving diagnostic characteristics, as well as a noninvasive means to observe the performance of intralaryngeal procedures. Throughout our assessments we used a Sonosite M-Turbo monitor with a linear ultrasound probe (Sonosite L25x, 13–6 MHz) to capture airway images.
IRB approval was not necessary for this study. Individual consent forms were signed to use ultrasonography in patients already scheduled for surgery.
The airway of an awake 3-year-old child was evaluated to demonstrate basic, clinically important anatomic features using a standardized probe placement based on easily recognizable external features in children. Using the linear ultrasound probe in the sagittal and axial planes over the mid-laryngeal area, we are able to visualize anatomic structures (Figs. 1 and 2). Of note, the structure of the tongue, hyoid, laryngeal structures (true vocal cords, arytenoids, anterior/posterior commisures, thyroid and cricoid cartilage [including cricothyroid membrane], and tracheal airspace) are readily identified.
Case 2—Vocal Cord Paralysis
A 10-month-old boy with previously diagnosed spina bifida, oropharyngeal dysphagia, hydrocephalus and chiari malformation, as well as bilateral vocal cord impairment presented to the otolaryngology clinic for follow-up evaluation with flexible fiberoptic laryngoscopy. The patient received no sedation or anesthetic for the procedure. Ultrasonography was performed in addition to flexible fiberoptic evaluation, recording video of the procedures. Ultrasound video imaging accurately depicted the findings seen with fiberoptic evaluation, showing left-sided vocal cord paresis with right-sided movement intact. (see Video 1, Supplemental Digital Content 1, http://links.lww.com/AACR/A5).
Case 3—Periglottic Steroid Injections
We evaluated a 20-month-old girl with a history of laryngotracheomalacia electively scheduled to receive periglottic steroid injection under general anesthesia. After inhaled induction of general anesthesia, spontaneous ventilation was maintained. Ultrasound evaluation was performed in the axial plane, with the center of the probe approximately placed at the level of the cricothyroid cartilage. Next, under real-time ultrasound guidance, a 20-gauge needle was placed percutaneously through the cricothyroid membrane and advanced caudal to the vocal cords. Needle location was confirmed by simultaneous direct visualization via rigid bronchoscopy by the otolaryngologist (see Video 2, Supplemental Digital Content 2, http://links.lww.com/AACR/A6). Steroid injection was then performed in the periglottic area under ultrasound and direct visualization. The procedure was performed without complication, and she was discharged home from the postanesthesia care unit on the day of the procedure.
We suggest that ultrasonography, a technology readily available in the operating room environment, can be used to identify anatomic structures of the pediatric airway. Pathologic conditions can also be visualized, specifically vocal cord paralysis as described here. In addition to describing structures within the airway, ultrasound can be used to visualize needle placement during airway procedures.
Since first used by Ludwig in the 1940s,1 ultrasound probes and machines have become smaller and easier to manipulate. In the 1990s, 3-dimensional and 4-dimensional (including time) probes were developed, and image quality and device portability improved substantially. With subsequent digitization of the imaging process and the addition of filtering technologies, “noise” from the images has been reduced and imaging quality has improved dramatically permitting identification of structures of varying densities and materials.2,3
Use of ultrasound technology to assist with therapeutic and diagnostic interventions by anesthesiologists has become common. Ultrasonography during central venous cannulation has been well studied, with the American Society of Anesthesiologists strongly recommending real-time ultrasound to be used for guidance during venous access when either the internal jugular or femoral veins are selected for cannulation.4 Peripheral nerve blocks and catheter placement are readily performed with ultrasound guidance as well. Ultrasonography of the pediatric airway was described in 1991, evaluating anatomy and pathology within the cavity.5,6 The image quality was poor, creating grainy pictures that made differentiating structures difficult to perform. With improvements in resolution and image quality, researchers have begun reinvestigating ultrasound use for airway management in adults7; however, this has not been done in children.
For a child with suspected or confirmed airway pathology, repeated evaluations inevitably involve multiple procedures or imaging modalities, such as computed tomography or magnetic resonance imaging, usually in combination with general anesthesia. Ultrasound technology enables noninvasive and well-tolerated evaluation without radiation exposure to the patient or clinician.
The prospect of using ultrasonography in the assessment of the pediatric airway can have significant implications in current clinical practice. The current practice has children undergo nasal fiberoptic evaluation without sedation, often requiring patient restraint to successfully obtain images. The standard of care for treatment of airway pathology involves general anesthetics with visualization via either rigid or flexible bronchoscopy or direct laryngoscopy. Ultrasonography could be used for both static and real-time dynamic studies, for pathologies such as vocal cord paralysis, suggested by our case series. By effectively using a simple, painless, easily available modality, airway evaluation may be performed in the absence of anesthetics.
We also demonstrate the use of ultrasound for interventional procedures of the airway, such as vocal cord steroid injections. Although this procedure has limited relevance within the scope of anesthesiology, our demonstration of an ultrasound-guided needle insertion through the cricothyroid membrane suggests potential use as a means of gaining access to the airway in the emergency situation. The ultimate recommendation in the American Society of Anesthesiology’s Difficult Airway Algorithm8 when intubation has failed is to obtain surgical access of the airway. Despite this algorithm, emergency surgical access to the airway has been discouraged in neonates and young children due to the complexity of the anatomy and the high risk of damaging vital,9 adjacent structures when the procedure is performed blindly. Our demonstration of ultrasound-guided cricothyroid puncture raises the notion that real-time placement using ultrasound guidance may be of use in the emergency situation, providing a rational technique in an otherwise potentially disastrous situation. This report reveals the possible usefulness of ultrasound imaging in clinical anesthesia care, specifically airway management, in children.
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