Ultrasonography in the preoperative difficult airway assessment

Evaluation of the cutaneous-epiglottic distance obtained by ultrasound in predicting difficult laryngoscopy in adult patients: an observational study

BACKGROUND

Ultrasound (US) allows for rapid bedside airway assessment. We aimed to evaluate the US-measured Cutaneous-Epiglottic Distance (CED) in predicting difficult laryngoscopy (Cormack-Lehane grades 3‒4). We also evaluated the potential association between CED, sex, patient's Body Mass Index (BMI), and the independent associations between CED and increased odds for Cormack-Lehane grades 3‒4 (secondary outcomes).

METHODS

Patients aged 18‒70 years scheduled for elective surgeries under general anesthesia with tracheal intubation were included. Those with a BMI > 35 kg.m-2 and/or previous history of difficult intubation were excluded. CED was measured with patients anesthetized before tracheal intubation. Age, sex, BMI, type of surgery, and number of attempts until successful tracheal intubation were recorded. Receiver Operator Characteristic (ROC) curve analysis was performed to evaluate CED's clinical relevance. Secondary analyses compared the association between CED and BMI in patients with Cormack-Lehane grades 1‒2 versus those with grades 3‒4. The relationship between CED and BMI was assessed using multiple linear regression. Binary logistic regression was employed for predicting Cormack-Lehane grades 3‒4 as a dichotomous outcome with CED and BMI as a covariate.

RESULTS

ROC curve analysis revealed an AUC of 0.899 (p < 0.001). The maximum CED cut-off point (by Youden index) was 25.6 mm. CED and BMI were positively correlated, and both were independently associated with an increased odds for difficult laryngoscopy (OR for CED = 1.81, 95% CI 1.35‒2.41; BMI = 1.30, 95%CI 1.05‒1.59).

CONCLUSION

US-measured CED has a high discriminatory capability for predicting lower (1‒2) and higher (3‒4) Cormack-Lehane grades during direct laryngoscopy. CED was positively correlated with BMI and was independently associated with higher odds for difficult laryngoscopy.

Ultrasound-based airway assessment in obese patients as a valuable tool for predicting difficult airway: an observational study

BACKGROUND

Difficult airway, characterized by difficult mask ventilation and intubation, is common in obese patients undergoing surgery. The purpose of this study was to evaluate and compare the prognostic efficiency of ultrasound-measured anterior cervical soft tissue parameters as an indicator of difficult airway during anesthesia induction in obese patients.

METHODS

This prospective, double-blind, observational study was conducted at Balikesir University Faculty of Medicine Hospital between March 2020 and March 2022. A total of 157 patients age ≥ 18 (BMI ≥ 30 kg.m-2), without previous head and neck surgery were included in the study. Anterior cervical soft tissue measurements were performed at three levels; minimum distance between the hyoid bone and skin at the level of the hyoid bone; (DSHB), distance between the midpoint of the epiglottis and skin at the level of the thyrohyoid membrane; (DSE), distance between the anterior commissure of vocal cords and skin at the vocal cord level; (DSV). The Han scale was used to assess difficult mask ventilation and the Cormack-Lehane scale was used to assess difficult laryngoscopy.

RESULTS

In the difficult laryngoscopy group, the mean values of DSHB, DSE and DSV were 18.5 ± 3.5, 18.3 ± 3.8, and 18.6 ± 3.4, respectively. The AUC values for DSHB, DSE, and DSV were 0.845, 0.827, and 0.850, respectively. Anterior cervical measurements showed a better predictive value for difficult laryngoscopy compared to difficult mask ventilation.

CONCLUSION

Ultrasonographic measurements were predictive for difficult laryngoscopy and ventilation with better correlation in laryngoscopy.

A Comparison of Airway Ultrasound and Clinical Parameters for Predicting Difficult Laryngoscopy in the Emergency Department: A Study Protocol

BACKGROUND

 Airway assessment plays an important part in airway management. Over the years, ultrasound has emerged as an alternative modality for airway assessment. We aim to assess the accuracy of clinical parameters, ultrasonographic upper airway parameters, and laryngoscopic grade, using the Cormack-Lehane classification, to predict difficult laryngoscopy in the emergency department (ED). The primary objective is to determine the accuracy of ultrasonography parameters compared to Cormack-Lehane grading in predicting difficult laryngoscopy in adults. The secondary objective is to assess the accuracy of clinical parameters compared to Cormack-Lehane grading in predicting difficult laryngoscopy in adults.

METHODS

A sample of 62 adult patients over 18 years who come to the emergency department and require endotracheal intubation will undergo an ultrasonographic examination of the upper airway. During this examination, an emergency medicine physician will measure the skin-to-epiglottis distance and tongue thickness using the GE Healthcare (Chicago, IL) ultrasound and color Doppler (model: Logic E).

RESULTS

The results of the study will be drawn in 2025 upon its completion.

CONCLUSIONS

The conclusion will be drawn regarding the correlation between ultrasound parameters and Cormack-Lehane grading and clinical parameters in predicting difficult laryngoscopy.

Evaluation of neck ultrasound measurements as a difficult airway predictor: A prospective observational study

This study aimed to investigate the relationship between cervical measurements and difficult airways using ultrasonographic measurements. American Society of Anesthesiologists grade I to III, male or female, 120 adult patients, undergoing elective surgery were enrolled in the study. The study involved measuring the distance of the trachea, cricoid cartilage, thyroid cartilage, vocal cord anterior commissure, and hyoid bone to the skin using a 10 to 13 MHz linear ultrasound probe in the transverse plane. Additionally, the length of the cricothyroid and thyrohyoid membranes, along with their distance from the skin, were measured using the probe in the sagittal plane. Subsequently, another experienced anesthesiologist conducted mask ventilation and intubation after the patient's induction of general anesthesia. Throughout this process, the patient was assessed for difficulties in mask ventilation, laryngoscopy, and intubation. 28 (23.3%) patients had a difficult airway. Analyzing the measurements associated with difficult airways, the most reliable predictor was the epiglottis midline-skin distance [AUC (area under the curve): 0.847, P < .001, cutoff: >19.9, sensitivity: 78.6%, specificity: 79.4%]. Additionally, other factors such as hyoid bone to skin distance, thyroid cartilage to skin distance, thyrohyoid membrane to skin distance, and vocal cord anterior commissure-skin distance were also identified as predictors for a difficult airway. The increase in the distance of the epiglottis midline, vocal cord anterior commissure, hyoid bone, thyrohyoid membrane, and thyroid cartilage to the skin at the level of the isthmus measured by ultrasonography is predictive of difficult airways. Based on our study outcomes, we assert that ultrasonographic evaluation can be used in the prediction of difficult airways.

Preoperative point-of-care neck ultrasound: beyond the airway

PURPOSE

A preoperative point-of-care neck ultrasound, carried out during preoperative airway evaluation by extending the scans to the regions close to the larynx and trachea, can allow for the rapid identification of unknown pathologies or abnormalities in a cost-effective and non-invasive manner. This prospective, observational study examines a series of ultrasound findings in structures close to the airway, made through preoperative point-of-care neck ultrasound in a cohort of 230 patients.

METHODS

We conducted a prospective observational study, enrolling 230 adult patients selected for elective abdominal surgery. The primary goal was to verify the predictive role of airway ultrasound in identifying difficult airways, while the secondary goal was to evaluate structures close to the airway such as jugular veins, carotid arteries, thyroid gland and soft tissues.

RESULTS

Overall, preoperative point-of-care neck ultrasound proved to be an effective and reliable method of obtaining details about local or systemic pathologies, which could affect perioperative care. For example, the exam consistently revealed the presence of carotid plaques or venous congestion, which could be used to best determine the patient's cardiovascular risk or to instigate further investigations. It also allowed for more accurate central venous catheter placement planning and better airway management and it warned about possible thyroid or neoplastic pathologies that would have otherwise remained unknown. In some cases, information from preoperative point-of-care neck ultrasound has even led to modifications in perioperative therapy.

CONCLUSION

Preoperative point-of-care neck ultrasound is fast, inexpensive, and non-invasive, and it can be easily performed by a properly trained professional during the preoperative airway ultrasound evaluation. It can be considered as a new preoperative assessment tool.

Spanish Society of Anesthesiology, Reanimation and Pain Therapy (SEDAR), Spanish Society of Emergency and Emergency Medicine (SEMES) and Spanish Society of Otolaryngology, Head and Neck Surgery (SEORL-CCC) Guideline for difficult airway management. Part I

The Airway Management section of the Spanish Society of Anesthesiology, Resuscitation, and Pain Therapy (SEDAR), the Spanish Society of Emergency Medicine (SEMES), and the Spanish Society of Otorhinolaryngology and Head and Neck Surgery (SEORL-CCC) present the Guide for the comprehensive management of difficult airway in adult patients. Its principles are focused on the human factors, cognitive processes for decision-making in critical situations, and optimization in the progression of strategies application to preserve adequate alveolar oxygenation in order to enhance safety and the quality of care. The document provides evidence-based recommendations, theoretical-educational tools, and implementation tools, mainly cognitive aids, applicable to airway management in the fields of anesthesiology, critical care, emergencies, and prehospital medicine. For this purpose, an extensive literature search was conducted following PRISMA-R guidelines and was analyzed using the GRADE methodology. Recommendations were formulated according to the GRADE methodology. Recommendations for sections with low-quality evidence were based on expert opinion through consensus reached via a Delphi questionnaire.

Factors that determine first intubation attempt success in high-risk neonates

BACKGROUND

Approximately 50% of all neonatal endotracheal intubation attempts are unsuccessful and associated with airway injury and cardiorespiratory instability. The aim of this study was to describe intubation practice at a high-risk Neonatal Intensive Care Unit (NICU) and identify factors associated with successful intubation at the first attempt.

METHODS

Retrospective cohort study of all infants requiring intubation within the Royal Children's Hospital NICU over three years. Data was collected from the National Emergency Airway Registry for Neonates (NEAR4NEOS). Outcomes were number of attempts, level of operator training, equipment used, difficult airway grade, and clinical factors. Univariate and multivariate analysis were performed to determine factors independently associated with first attempt success.

RESULTS

Three hundred and sixty intubation courses, with 538 attempts, were identified. Two hundred and twenty-five (62.5%) were successful on first attempt, with similar rates at subsequent attempts. On multivariate analysis, increasing operator seniority increased the chance of first attempt success. Higher glottic airway grades were associated with lower chance of first attempt success, but neither a known difficult airway nor use of a stylet were associated with first attempt success.

CONCLUSION

In a NICU with a high rate of difficult airways, operator experience rather than equipment was the greatest determinant of intubation success.

IMPACT

Neonatal intubation is a high-risk lifesaving procedure, and this is the first report of intubation practices at a quaternary surgical NICU that provides regional referral services for complex medical and surgical admissions. Our results showed that increasing operator seniority and lower glottic airway grades were associated with increased first attempt intubation success rates, while factors such as gestational age, weight, stylet use, and known history of difficult airway were not. Operator factors rather than equipment factors were the greatest determinants of first attempt success, highlighting the importance of team selection for neonatal intubations in a high-risk cohort of infants.

Prediction of Difficult Laryngoscopy Using Ultrasound: A Systematic Review and Meta-Analysis

OBJECTIVES

Evaluate associations between ultrasound measures and difficult laryngoscopy.

DATA SOURCES

MEDLINE, Embase, Google Scholar, Web of Science, and the Cochrane Library were searched using MeSH terms and keywords.

STUDY SELECTION

Studies published in English describing the use of airway ultrasound for identifying difficult laryngoscopy, with sufficient data to calculate sensitivity and specificity using 2 × 2 tables.

DATA EXTRACTION

We assigned the described indices of airway dimension to one of three domains based on methodology characteristics: anterior tissue thickness domain, anatomical position domain, and oral space domain. We then performed a bivariate random-effects meta-analysis, deriving pooled sensitivity, specificity, diagnostic odds ratio, positive likelihood ratio, and negative likelihood ratio estimates. We assessed risks of bias using Quality Assessment of Diagnostic Accuracy Studies-2 analysis.

DATA SYNTHESIS

Thirty-three studies evaluating 27 unique indices were included in the meta-analysis. The ultrasound protocols of the included studies were heterogeneous. Anterior tissue thickness demonstrated a pooled sensitivity of 76% (95% CI, 71-81%), specificity of 77% (95% CI, 72-81%), and an area under the receiver operating characteristic curve (AUROC) of 0.83 (95% CI, 0.80-0.86). Anatomical position demonstrated a pooled sensitivity of 74% (95% CI, 61-84%), specificity of 86% (95% CI, 78-91%), and an AUROC of 0.87 (95% CI, 0.84-0.90). Oral space demonstrated a pooled sensitivity of 53% (95% CI, 0.36-0.69), specificity of 77% (95% CI, 0.67-0.85), and an AUROC of 0.73 (95% CI, 0.69-0.77).

CONCLUSIONS

Airway ultrasound metrics associate with difficult laryngoscopy in three domains: anterior tissue thickness, anatomic position, and oral space. An assessment instrument combining clinical and ultrasound assessments may be an accurate screening tool for difficult laryngoscopy.

Airway Ultrasound for Anesthesia and in Intensive Care Patients-A Narrative Review of the Literature

Ultrasound is an everyday diagnostic tool. In anesthesia and intensive care, it has a role as an adjuvant for many procedures, including the evaluation of the airway. Ultrasound airway evaluation can help predict a difficult airway, visualize the proper positioning of an intubation cannula, or evaluate the airway post-intubation. Protocols need to be established for the better integration of ultrasound in the airway evaluation, however until a consensus is reached in this respect, the ultrasound is a reliable aid in anesthesia and intensive care.

Comparison of Airway Ultrasound Indices and Clinical Assessment for the Prediction of Difficult Laryngoscopy in Elective Surgical Patients: A Prospective Observational Study

Background:

Ultrasound is evolving as a probable tool in airway assessment. The upper airway is a superficial structure and has sonographically identifiable structures which makes it ideal for evaluation with the ultrasound.

Aims:

The aim of this study was to evaluate the role of skin to hyoid and skin to thyrohyoid membrane distance in prediction of difficult laryngoscopy.

Settings and Design:

This is a prospective observational study included 150 patients aged 18–60 years of American Society of Anesthesiologists Physical Status I and II scheduled to undergo surgery under general anesthesia requiring laryngoscopy and endotracheal intubation.

Materials and Methods:

The modified Mallampati score, mouth opening, mentohyoid distance, thyromental distance were noted. Skin to hyoid bone distance and skin to thyrohyoid membrane distance were measured by ultrasound. Patients were clubbed retrospectively into easy and difficult laryngoscopy groups on the basis of Cormack Lehane grading, and the characteristics of both groups were compared.

Statistical Analysis:

Statistical Package for the Social Sciences, Version 23 was used for statistical analysis. Independent samples t-test was used to compare the means between difficult and easy laryngoscopy patients. Diagnostic accuracy of the significant (P < 0.05) variables between difficult and easy laryngoscopy patients was calculated using receiver operating characteristics curve in terms of their area under curve. Appropriate cutoff values (with corresponding sensitivity, specificity, and overall accuracy) were also identified.

Results:

Out of 150 patients, 13 (8.7%) were identified as difficult laryngoscopy whereas 137 patients (91.3%) were identified as easy laryngoscopy. The demographics of both groups were comparable. Mentohyoid distance, skin to hyoid bone distance, and skin to thyrohyoid distance were statistically different between easy and difficult laryngoscopy patients, with lower mentohyoid distance and higher skin to hyoid bone distance and skin to thyrohyoid distance in difficult laryngoscopy patients. Diagnostic accuracy of the mentohyoid distance (70.3%) was slightly superior to skin to hyoid bone distance (67.1%) and skin to thyrohyoid distance (68.1%).

Conclusion:

Ultrasound measurements of skin to hyoid bone and skin to thyrohyoid membrane distance fail to eclipse clinical parameters in accurately predicting a difficult laryngoscopy.

Submental Ultrasound Is Effective in Predicting Difficult Mask Ventilation but Not in Difficult Laryngoscopy

The goal of this study was to determine the utility of submental ultrasound parameters in distinguishing difficult airway management from easy airway management. Forty-one adult patients who underwent elective surgery under general anesthesia with endotracheal intubation from March to December 2018 were included. We used submental ultrasound to measure tongue base thickness (TBT) in the midsagittal plane and the distance between lingual arteries (DLA) in the transverse dimension. The primary outcome was difficult laryngoscopy, and the secondary outcome was difficult mask ventilation. Receiver operating characteristic curve analysis and logistic regression revealed no correlation between difficult laryngoscopy and SMUS measurements. Nevertheless, patients with difficult mask ventilation had significantly higher TBT (p = 0.009) and longer DLA (p = 0.010). After adjustment of confounding factors, increased TBT (>69.6 mm) was the sole independent predictor of difficult mask ventilation. The results indicated that SMUS is effective in predicting difficult mask ventilation but not difficult laryngoscopy.

Complex Pathology and Management in the Obstetric Patient: A Narrative Review for the Anesthesiologist

Pregnant patients may present with multiple complex comorbidities that can affect peripartum management and anesthetic care. The preanesthesia clinic is the ideal setting for early evaluation of high-risk pregnant patients. Comorbidities may include cardiovascular pathology such as valvular abnormalities, septal defects, aortopathies, arrythmias and cardiomyopathies. Additional comorbidities include pulmonary conditions such as obstructive sleep apnea as well as preexisting neuromuscular and skeletal disorders that may impact anesthetic management. Hematologic conditions involving both bleeding diathesis and thrombophilias may present unique challenges for the anesthesiologist. Patients may also present with endocrinopathies including diabetes and obesity. While not as common, high-risk patients may also have preexisting gastrointestinal conditions such as liver dysfunction, renal failure, and even post-transplant status. Ongoing and prior substance abuse, obstetric conditions such as placenta accreta spectrum disorders, and fetal conditions needing ex utero Intrapartum treatment also require advanced planning. Preanesthesia evaluations also help address important ethical and cultural considerations. Counseling patients regarding anesthetic considerations as well as addressing concerns will play a role in reducing racial and ethnic disparities. Anticipatory guidance by means of pre-anesthetic planning can facilitate multidisciplinary communication and planning. This can allow for an impactful and meaningful role in the care provided, allowing for safe maternal care and optimal outcomes.

Comparative Study of Clinical and Ultrasound Parameters for Defining a Difficult Airway in Patients with Obesity

INTRODUCTION

Patients with obesity have anatomical changes due to increased adipose tissue that negatively affect airway accessibility, making it difficult to establish an advanced airway through orotracheal intubation. This article aims to evaluate the correlation of clinical and sonographic parameters as predictors of difficult airway management (DAM) in patients with obesity and to establish the predictive value of the skin-epiglottis distance as an indicator of a probable DAM.

METHODS

This is an observational, prospective study of 100 patients with obesity who underwent bariatric surgery over a 12-month period. The patients were categorized into the easy airway and the difficult airway groups, according to the Cormack-Lehane classification in the laryngoscopy evaluation, and the clinical and sonographic variables collected were statistically evaluated to obtain the relation with the presence of DAM, according to the Cormack-Lehane classification.

RESULTS

The mouth opening (p = 0.010) and the skin-epiglottis distance (p = 0.019) were statistically significant when comparing the easy airway and the difficult airway groups of the Cormack-Lehane classification. The predictive value of the skin-epiglottis distance for difficult airway assessment was 29.3 mm. The neck circumference (p = 0.225), the Mallampati index (p = 0.260), and the other clinical variables showed no statistical relevance when compared in isolation with the Cormack-Lehane groups.

CONCLUSION

The ultrasound method as a predictor of difficult intubation is promising in anesthetic practice when used according to standardized measurements evaluation and cutoff values.

Useful Ultrasonographic Parameters to Predict Difficult Laryngoscopy and Difficult Tracheal Intubation-A Systematic Review and Meta-Analysis

Unexpected difficult airway management can cause significant morbidity and mortality in patients admitted for elective procedures. Ultrasonography is a promising tool for perioperative airway assessment, nevertheless it is still unclear which sonographic parameters are useful predictors of difficult laryngoscopy and tracheal intubation. To determine the ultrasonographic predictors of a difficult airway that could be applied for routine practice, a systematic review and meta-analysis was conducted. Literature search was performed on PubMED, Web of Science and Embase using the selected keywords. Human primary studies, published in English with the use of ultrasonography to prediction of difficult laryngoscopy or tracheal intubation were included. A total of 19 articles (4,570 patients) were analyzed for the systematic review and 12 articles (1,141 patients) for the meta-analysis. Standardized mean differences between easy and difficult laryngoscopy groups were calculated and the parameter effect size quantified. A PRISMA methodology was used and the critical appraisal tool from Joanna Briggs Institute was applied. Twenty-six sonographic parameters were studied. The overall effect of the distance from skin to hyoid bone (p = 0.02); skin to epiglottis (p = 0.02); skin to the anterior commissure of vocal cords (p = 0.02), pre-epiglottis space to distance between epiglottis and midpoint between vocal cords (p = 0.01), hyomental distance in neutral (p < 0.0001), and extended (p = 0.0002) positions and ratio of hyomental distance in neutral to extended (p = 0.001) was significant. This study shows that hyomental distance in the neutral position is the most reliable parameter for pre-operative airway ultrasound assessment. The main limitations of the study are the small sample size, heterogeneity of studies, and absence of a standardized ultrasonographic evaluation method [Registered at International prospective register of systematic reviews (PROSPERO): number 167931].

Effectiveness and validity of midsagittal tongue cross-sectional area and width measured by ultrasound to predict difficult airways

BACKGROUND

Increased tongue volume measured by ultrasound has been proven to be related to difficult airways. Tongue volume is an indirect parameter and is derived from multiplying the midsagittal tongue cross-sectional area (CSA) by the tongue width. However, few studies have focused on the ability of tongue CSA and tongue width to predict difficult airways. This study aimed to investigate the predictive value of tongue CSA and tongue width for predicting difficult laryngoscopy and difficult intubation.

METHODS

This study included 244 adult patients who underwent general anesthesia and endotracheal intubation. Demographic variables were collected, and clinical airway assessments were performed. A curvilinear low-frequency probe was used for ultrasonography, and midsagittal tongue CSA and tongue width were measured before anesthesia. The laryngoscopic view and the difficulty of intubation was graded or scored after induction of anesthesia.

RESULTS

A total of 230 patients were analyzed. Twenty-eight (12.2%) patients experienced difficult laryngoscopy and twelve (5.2%) patients experienced difficult intubation. Midsagittal tongue CSA evaluated by ultrasonography could help identify patients with difficult laryngoscopy (sensitivity 0.71, specificity 0.60) and patients with difficult intubation (sensitivity 0.50, specificity 0.97). And tongue width could help identify patients with difficult laryngoscopy (sensitivity 0.39, specificity 0.89).

CONCLUSIONS

Ultrasonic measurement of midsagittal tongue CSA may be a valuable predictor of difficult laryngoscopy and difficult intubation. By contrast, tongue width measured by ultrasound may be a weak predictor of difficult laryngoscopy, but its predictive ability was questionable.

Ultrasonography for airway management

Ultrasonography (USG) allows a new approach to the airway in anaesthesia and intensive care. USG visualises the airway from the mouth to the lungs. By exploring the entire airway, USG proposes new criteria (1) to assess the risk of difficult laryngoscopy, (2) to anticipate the management of a difficult airway, (3) to confirm the position of the endotracheal tube (ETT), and (4) to confirm that the lungs are effectively ventilated. Intraoperatively, USG may also help to resolve acute ventilatory problems such as pneumothorax, delayed selective bronchial intubation after patient positioning (Trendelenburg, prone or lateral position) or acute pulmonary oedema.

Airways ultrasound in predicting difficult face mask ventilation

BACKGROUND

Unanticipated difficult airway is a potentially life-threatening event during elective surgery or management of critical conditions. Nevertheless, predicting difficult mask ventilation currently remains a challenge due to the poor sensitivity of available clinical tests. Our primary goal was to verify whether preoperative upper airway ultrasound measurements were useful to predict difficult face mask ventilation. Our secondary goal was to evaluate clinical characteristics and differences between patients who are difficult to ventilate and patients who are not.

METHODS

We performed a prospective observational study, enrolling 250 adult patients selected for colorectal, gastric, bariatric and pancreatic elective surgery between September 2017 and October 2018. We performed a preoperative US assessment of the airways, following a standardized protocol. We measured the hyomental distance (DIM), the thickness of the base of the tongue (SBL), the thickness of the soft tissues anterior to the hyoid bone (STTi), thyro-hyoid distance (DTI), the thickness of soft tissue anterior to the epiglottis (STTe), to the arytenoid (STTa) and to the commissure of the vocal cords (STTcv).

RESULTS

SBL had a predictive role of difficult mask ventilation in curarized and noncurarized patients for values higher than 50 mm. Hyomental distance with hyperextension of the head and subluxation of the mandible (DIMs) had a predictive role in the curarized patient (protective parameter).

CONCLUSIONS

Airways ultrasound evaluation could be an important tool to predict difficult mask ventilation. Further studies are necessary to validate the parameters found and correlate them to the preoperative clinical evaluation.

Point-of-care ultrasound in pediatric anesthesia: perioperative considerations

PURPOSE OF REVIEW

To review the perioperative applications of point-of-care ultrasound (POCUS).

RECENT FINDINGS

The role of point-of-care ultrasonography for perioperative care is expanding with respect to perioperative application. The imaging approach can complement the physical exam and provide additional information for decision-making in pediatric perioperative medicine. This review will focus on applications in the following organ systems: airway, cardiac, pulmonary and gastric. Specifically, POCUS of the airway has been used to optimize endotracheal tube depth, aid in tube size selection and predict difficulty with laryngoscopy and intubation. Lung POCUS has been used to assess for causes hypoxemia as well as to optimize ventilatory mechanics. Cardiac POCUS has been used for assessment of hemodynamics, valvular and ventricular function. Gastric ultrasound has emerged as an evaluative mechanism of gastric content in the setting of fasting as well as to confirm placement of gastric tubes. The applications of POCUS in the perioperative setting continue to evolve as a reliable diagnostic tool that can assist in timely diagnosis, improve procedural safety and has the potential to improve patient outcomes.

SUMMARY

The utility of perioperative POCUS has been well demonstrated, specifically for examination of the airway, stomach and cardiopulmonary system. It is advisable for the novice sonographer to perform POCUS within the guidelines set by the American Society of Echocardiography regarding basic POCUS. As with all diagnostic modalities, understanding the limitations of ultrasound and POCUS as well as continuous self-assessment is crucial.

Point-of-care ultrasound in the preoperative setting

Point-of-care ultrasound (POCUS) is a widely used diagnostic tool, especially in emergency and critical care medicine, and it is increasingly being used in the perioperative setting. Its specific role in preoperative assessment of patients, however, has not yet been defined. While some data show innovative use of the technique in the preoperative setting, higher-level evidence to underscore potential advantages is still limited. We review and discuss a range of POCUS examinations which can potentially help anaesthesiologists in the preoperative clinic decide whether to perform additional testing, can assist in selecting the best anaesthetic approach, and can support perioperative and postoperative monitoring.

Perioperative Point-of-Care Ultrasound

This clinical focus review targets all anesthesiologists and seeks to highlight the following aspects of perioperative point-of-care ultrasound: clinical utility, technology advancements, training/certification, education, reporting/billing, and limitations.

The usefulness of point of care ultrasound (POCUS) in preanaesthetic airway assessment

Background and Aims:

Point of care ultrasound has the potential to become reliable airway assessment tool by accurate prediction of difficult laryngoscopy. We aimed to determine the feasibility of ultrasound in preoperative airway assessment.

Methods:

This prospective, observational study was conducted on 200 patients requiring general anaesthesia and tracheal intubation. The thickness of anterior soft tissue neck at the level of hyoid bone (DSHB), epiglottis (DSEM), and Pre-E/E-VC[depth of the pre-epiglottic space (Pre-E)/distance from the epiglottis to the midpoint of the distance between the vocal cords (E-VC)] were measured sonographically. The hyomental distance ratio (HMDR) was measured utilising distances with head in neutral and extended position. The primary outcome was the efficacy of the parameters in predicting difficult laryngoscopy[Cormack Lehane 3,4]. The secondary outcome was to correlate the parameters to CL grading.

Results:

Utilising receiver operating curves, cutoff value of HMDR for predicting difficult laryngoscopy was ≤1.0870 with sensitivity of 65%, specificity of 77%. The cutoff value, sensitivity andspecificity for Pre-E/E-VC were ≥1.785, 82.8% and 83.8%., respectively. The cutoff value of DSHB was ≥0.99 with sensitivity of 48% and specificity of 82%. The cutoff, sensitivity and specificity for DSEM were ≥1.615, 89.7%, and 64.8%, respectively. There was moderate positive correlations of DSHB, DSEM, and Pre-E/E-VC (r = 0.551 and 0.701, 0.787: P = 0.00), whereas moderate negative correlation observed with HMDR (r = -.0671: P = 0.00).

Conclusion:

The strong positive correlation of Pre-E/E-VC, DSEM, and moderate negative correlation of HMDR makes these ultrasound parameters reliable predictors for difficult laryngoscopy.

Ultrasound for predicting difficult airway in obstetric anesthesia: Protocol and methods for a prospective observational clinical study

BACKGROUND

Failed intubation and ventilation during cesarean deliveries are important causes of anesthetic-related maternal mortality. Due to the physiological changes in airway anatomy, parturient had higher incidences of difficult airway than non-obstetric population. Accurate airway assessment is the first step and the most important in airway management. However, the common clinical screening tests, shown low sensitivity and specificity with a limited predictive value. Ultrasound is a quick, noninvasive, inexpensive tool, with the advancement of ultrasound technology, modern ultrasound machine is more portable with better resolution and enhanced tissue penetration, provide better imaging in tissues like epiglottis, vocal cords, ring-shaped membrane, and can be used in airway assessment. Here, the aim of the current study was to find whether preoperative ultrasound assessment of neck anatomy can predict difficult airway in parturient, and provide new ideas and a theoretical basis in the airway management of obstetric anesthesia.

METHODS

This is a prospective, observational single-blinded study in a single-center. Subjects will be recruited from patients aged from 18 to 60 years, gestational age ≥ 36 weeks, scheduled for cesarean section under general anesthesia and tracheal intubation. Ultrasound measurement will be performed to detect anterior cervical soft tissue thickness at five anatomical levels (hyoid bone, epiglottis, cricothyroid membrane, thyroid isthmus and suprasternal notch) in the upper airway. The thickness of the soft tissue in the front of the neck and clinical airway measurements will be compared between the "easy intubation" and "difficult intubation" group divided by Cormack-Lehane grade. Receiver-operating characteristic curves were used to determine the sensitivity and specificity of "difficulty prediction capability" of each sonographic and physical measurements. Clinical factors associated with difficult intubation will be determined by univariate analyses. Multiple logistic regression analysis performed to determine independent predictors of difficult intubation.

CONCLUSIONS

The study outlined in this protocol will explore the possibility of ultrasound for predicting difficult airway in obstetric anesthesia. This may provide new insight into the practice of airway management.

TRIAL REGISTRATION

Chinese Clinical Trial Registry, ChiCTR1800018949.

Anterior neck soft tissue thickness for airway evaluation measured by MRI in patients with cervical spondylosis: prospective cohort study

OBJECTIVES

Anterior neck soft tissue thickness, usually measured by ultrasound, is increasingly being investigated to predict difficult laryngoscopy, but the results have not been validated. Considering the conflicting measurement data, different measuring body positions and lack of a standard ultrasound procedure, we used MRI to verify the efficacy of these popular ultrasonographic parameters.

DESIGN

Prospective cohort study.

SETTING

A tertiary hospital in Beijing, China.

METHODS

We enrolled 315 adult patients who underwent cervical spinal surgery in Peking University Third Hospital from April to October 2016. We analysed MRI data to predict difficult laryngoscopy. Cormack-Lehane scales were assessed during intubation, and patients with a class III or IV view were assigned to the difficult laryngoscopy group.

RESULTS

Univariate analysis showed that male sex (p<0.01), older age (p=0.03) and body weight (p=0.02) were associated with difficult laryngoscopy. MRI data consisted of five common ultrasonographic variables used to predict difficult laryngoscopy, but none was a valuable predictor: skin to hyoid (p=0.18), skin to midpoint of epiglottis (p=0.72), skin to thyroid cartilage at the level of the vocal cords (p=0.10), skin to vocal cords (p=0.44) or skin to anterior to the trachea at the level of suprasternal notch (p=0.92). Adjusted by sex, age and body weight, none of the five MRI indicators had predictive value (p>0.05).

CONCLUSION

The five most commonly studied ultrasonographic indicators of anterior soft tissue thickness appeared unreliable to predict difficult laryngoscopy in patients with cervical spondylosis. Further study is needed to validate the most valuable indicator to predict difficult laryngoscopy.

TRIAL REGISTRATION NUMBER

ChiCTRROC-16008598; Pre-results.

Radiological evaluation of airway - What an anaesthesiologist needs to know!

Airway management forms the foundation of any anaesthetic management. However, unanticipated difficult airway (DA) and its sequelae continue to dread any anaesthesiologist. In spite of development of various clinical parameters to judge DA, no single parameter has proved to be accurate in predicting it. Radiological evaluation may help assess the aspects of patient's airway not visualised through the naked eye. Starting from traditional roentgenogram to ultramodern three-dimensional printing, imaging may assist the anaesthesiologists in predicting DA and formulate plan for its management. Right from predicting DA, it has been used for estimating endotracheal tube sizes, assessing airway pathologies in paediatric patients and planning extubation strategies. This article attempts to provide exhaustive overview on radiological parameters which can be utilised by anaesthesiologists for prediction of DA.

The Use of Point-of-Care Ultrasonography in Trauma Anesthesia

Caring for the trauma patient requires an in-depth knowledge of the pathophysiology of trauma, the ability to rapidly diagnose and intervene to reverse the derangements caused by shock states, and an aptitude for the use of advanced monitoring techniques and perioperative point-of-care ultrasonography (P-POCUS) to assist in diagnosis and delivery of care. Historically, anesthesiology has lagged behind in wholly embracing this technology. P-POCUS has the potential to allow the trauma anesthesiologist to diagnose numerous injuries, quickly guide the placement of central vascular catheters and invasive monitors, and assess the efficacy of interventions.

Journal of Clinical Monitoring and Computing 2017 end of year summary: respiration

This paper reviews 32 papers or commentaries published in Journal of Clinical Monitoring and Computing in 2016, within the field of respiration. Papers were published covering airway management, ventilation and respiratory rate monitoring, lung mechanics and gas exchange monitoring, in vitro monitoring of lung mechanics, CO2 monitoring, and respiratory and metabolic monitoring techniques.

Ultrasound evaluation of the airway in the ED: a feasibility study

Background

Recognition of the difficult airway is a critical element of emergency practice. Mallampati score and body mass index (BMI) are not always predictive and they may be unavailable in critically ill patients. Ultrasonography provides high-resolution images that are rapidly obtainable, mobile, and non-invasive. Studies have shown correlation of ultrasound measurements with difficult laryngoscopy; however, none have been performed in the Emergency Department (ED) using a consistent scanning protocol.

Objectives

This study seeks to determine the feasibility of ultrasound measurements of the upper airway performed in the ED by emergency physicians, the inter-rater reliability of such measurements, and their relationship with Mallampati score and BMI.

Methods

A convenience sample of volunteer ED patients and healthy volunteers with no known airway issues, aged > 18 years, had images taken of their airway using a standardized ultrasound scanning protocol by two EM ultrasound fellowship trained physicians. Measurements consisted of tongue base, tongue base-to-skin, epiglottic width and thickness, and pre-epiglottic space. Mean and standard deviation (SD) were used to summarize measurements. Inter-rater reliability was assessed by intraclass correlation coefficients (ICCs). Analysis of variance with linear contrasts was used to compare measurements with Mallampati scores and linear regression with BMI.

Results

Of 39 participants, 50% were female, 50% white, 42% black, with median age 32.5 years (range 19–90), and BMI 26.0 (range 19–47). Mean ± SD for each measurement (mm) was as follows: tongue base (44.6 ± 5.1), tongue base-to-skin (60.9 ± 5.3), epiglottic width (15.0 ± 2.8) and thickness (2.0 ± 0.37), and pre-epiglottic space (11.4 ± 2.4). ICCs ranged from 0.76 to 0.88 for all measurements except epiglottis thickness (ICC = 0.57). Tongue base and tongue base-to-skin thickness were found to increase with increasing Mallampati score (p = .04, .01), whereas only tongue-to-skin thickness was loosely correlated with BMI (r = .38).

Conclusions

A standardized ultrasound scanning protocol demonstrates that the airway can be measured by emergency sonologists with good inter-operator reliability in all but epiglottic thickness. The measurements correlate with Mallampati score but not with BMI. Future investigation might focus on ultrasound evaluation of the airway in patients receiving airway management to determine whether ultrasound can predict challenging or abnormal airway anatomy prior to laryngoscopy.

Neck fat volume as a potential indicator of difficult intubation: A pilot study

Background:

Direct laryngoscopy is the gold standard of the airway management in patients without predicted difficulties. If unpredicted difficulties are encountered instead, different algorithms to follow have been developed. To date, no single predictor is sufficiently valid. In clinical practice, it is used a combination of them to enhance the estimate, and despite the variety of parameters used, not all the difficult intubations are predicted. The aim of this work is to retrospectively analyze neck computed tomography scans of 37 patients who have had tracheal intubation and search for anatomic neck fat compartments that correlate with the intubation difficulty, and eventually find a suitable, clinical parameter that can potentially enhance the prediction of a difficult airway when used in combination of the preexisting scores.

Materials and Methods:

the patients are divided by direct laryngoscopy view into two groups: Group A (n = 31): Normal airway, with a Cormack Lehane, Score I or II; Group B (n = 6): Difficult airway, with a Cormack Lehane Score III or IV. In the zone of interest, it was measured the neck volume parameter and other subparameters.

Results:

Despite a positive trend is shown for anterior fat volume (AFV) (P = 0.23) and fat volume (FV) (P = 0.28), statistically significant differences (P < 0.05) were not found between Group A and B in any of the measurements acquired.

Conclusions:

According to the literature, our results confirmed that there is still no single element that can predict a difficult intubation. Although no statistical significance was found, the AFV and FV have shown to have a potential predictive role for difficult intubation. Further studies with bigger samples are advisable to confirm this encouraging result.

Can thyromental distance be measured accurately?

Using the thyromental distance (TMD) measured based on the ultrasonographic location of the thyroid cartilage prominence as the criterion, we investigated the accuracy of TMD measurement by surface landmark identification of the thyroid cartilage prominence. Twenty-nine anesthetist resident volunteers were recruited, including 10 first-year residents, 9 second-year residents and 10 third-year residents. Each volunteer measured the other 28 volunteers’ TMD. Then, the thyroid cartilage prominence of each volunteer was identified by ultrasonography of the junction of the vocal cord and thyroid cartilage, and the TMD was measured precisely. The error of the TMD measurement was determined by the minimal detectable difference (MDD) compared to the ultrasound measurement. A difference of greater than 5.4 mm between the TMD measured by volunteers and that based on ultrasound localization was defined as a measurement error. The measurement error rate of females’ TMD was significantly higher than that of males’ (50 vs 10%, P < 0.001). The error rates of anesthetist residents of first-year, second-year and third-year were 34, 27, and 31%, respectively, and were not significantly different. The error of TMD measurement by surface landmark identification is often, especially for women. More clinic experience don’t improve it.

Usefulness of Ultrasound View of Larynx in Pre-Anesthetic Airway Assessment: A Comparison With Cormack-Lehane Classification During Direct Laryngoscopy

Background

One of the main challenges in anesthesiology is difficult intubation. There are many anatomical parameters for evaluating the feasibility of tracheal intubation; one that can reliably predict a difficult intubation is the Cormack-Lehane classification obtained during direct laryngoscopy. This is an invasive procedure that cannot be performed in an awake patient or for pre-anesthetic airway assessments in patients with no prior history of tracheal intubation. Recently, ultrasound has been successfully used for several airway-related applications.

Objectives

The aim of this study was to compare and correlate the ultrasound view of the larynx with the Mallampati classification before anesthesia and the Cormack-Lehane classification during direct laryngoscopy under general anesthesia.

Methods

This cross-sectional descriptive-analytic study included 53 ASA class I - III patients aged 18 - 70 years who were scheduled for tracheal intubation under general anesthesia. Before anesthesia, an oblique transverse ultrasound view of the airway was obtained; in addition, the total time taken to achieve the final plane, the depth of the pre-epiglottic space, and the distance from the epiglottis to the mid-point between the vocal cords were all recorded. The ultrasound measurements were then compared with the Mallampati class on the preoperative evaluation and with the Cormack-Lehane grade during direct laryngoscopy under general anesthesia.

Results

It was observed that correlations between the pre-epiglottic space (PE) and Cormack-Lehane grades I, II, and III were weak. Correlations between the distance from the epiglottis to the vocal cords (E-VC) and Cormack-Lehane grades I, II, and III were also weak. The PE/E-VC ratio for correlations between the sonographic view and laryngoscopy had 87.5% sensitivity and 30% specificity. There was no correlation between Mallampati class and the PE/E-VC ratio (P = 0.566).

Conclusions

Our study revealed weak correlation between PE/E-VC and Cormack-Lehane grade, with 87% sensitivity and 30% specificity. Therefore, we concluded that sonographic measurement criteria are not accurate in airway evaluations before anesthesia.