Upper Airway Ultrasound to Predict Difficult Laryngoscopy in Neonates and Infants

Upper airway ultrasound (UA-US) has been utilized in adults to predict difficult laryngoscopy (Cormick-Lehane view 3 or 4) and difficult tracheal intubation (DTI) (≥3 intubation attempts) and with moderate-to-high sensitivity and specificity. This bedside technique is reproducible, easy-to-do without any additional radiation risk, and was added to the most recent American Society of Anesthesiologists (ASA) Practice Guidelines for Difficult Airway Management in Adults. However, UA-US has only been applied to older children ages 5-12 and has not been examined in neonates and infants. Thus, the aim of this observational study using UA-US to predict difficult laryngoscopy and tracheal intubation in neonates and infants presenting for diagnostic, procedural or surgical care under general anesthesia requiring endotracheal intubation.

Neonates and infants have a higher incidence of difficult laryngoscopy and DTI compared to older children and adults. Classical methods of screening for difficult laryngoscopy or DTI in adults, such as a Mallampati score, thyromental distance, and neck circumference are poorly applied to our smallest patients. UA-US has emerged as a technique to measure several UA parameters at the bedside with impressive sensitivity and specificity for identifying a difficult airway in adult patients, with higher UA-US measurements correlating with higher Cormick-Lehane laryngoscopy scores. UA-US was recently added to the 2022 ASA Practice Guidelines for Difficult Airway Management, specifically distance from the skin to the epiglottis (DSE), distance from the skin to the hyoid bone (DSHB), and tongue thickness (TTh). While UA-US has been minimally studied in children, one study showed high positive and negative predictive values for DTI with DSE and hyomental distance (HMD) in children aged 5-12 years. UA-US has the potential to identify unanticipated difficult airways in neonates and infants but has not been studied in this vulnerable population. Despite the adoption of video laryngoscopy (VL) for intubation of neonates and infants in many clinical settings, there remains a substantial incidence of difficult glottic exposure and DTI. Garcia-Marcinkiewicz et al. found an incidence of difficult laryngoscopy, defined as a percentage of glottic opening (POGO) score \<100 in 33% of neonates and infants intubated with VL. The NEonatal and Children AudiT of Anaesthesia pRactice (NECTARINE) trial, a multicenter prospective study performed in Europe, found a DTI rate of 5.8% amongst neonates and infants requiring intubation for a surgical procedure. Of these difficult intubations, nearly 70% were unplanned, unanticipated difficult airways. Repeated attempts at intubation are correlated with an increased rate of serious complications like severe hypoxemia, airway trauma, and cardiac arrest, and those youngest in age are at highest risk. Unanticipated difficult airways are more likely to increase the number of tracheal intubation attempts required for success. UA-US could be utilized as a non-invasive, bedside tool to screen neonates and infants for unanticipated difficult laryngoscopy and intubation, facilitating multidisciplinary airway planning, in and out of the operating room, potentially reducing the need for multiple intubation attempts and patient harm. However, UA-US has never been applied to this patient population. This would be an innovative application of a point-of-care ultrasound modality that is currently being utilized in multiple adult care settings (operating room, emergency department and intensive care units). UA-US has similarly broad potential functions in pediatric medicine that are currently being underutilized. As this is a novel application of this technique in this patient population, the aims of this study are to examine the differences in distribution of UA-US measurements between neonates and infants with and without difficult glottic exposure (POGO score 0-50%) with VL. In adult studies, direct laryngoscopy (DL) is commonly used and difficulty of laryngoscopy typically graded using the Cormick-Lehane grading scale (I-IV). However, airway management differs in neonates and infants. The First-Attempt Success Rate of Video Laryngoscopy In Small Infants (VISI) trial performed in 2020 found a significantly higher success rate of first-intubation success utilizing VL over DL (93% versus 88%, P=0.024.) in neonates and infant presenting for tracheal intubation during surgery. As a result, VL is considered standard of care in this patient population. Further, to test whether UA-US measurements correlate accurately to difficult laryngoscopy and DTI, it is pertinent to standardize the intubation technique to reduce confounding. The investigators hypothesize that higher UA-US values will be associated with higher odds of having worse POGO scores in neonates and infants intubated with VL.