Abstract
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.
Supplementary Information
The online version contains supplementary material available at 10.1007/s40477-023-00840-1.
Keywords: Airway ultrasound, Neck ultrasound, Preanesthetic evaluation, Ultrasound in anesthesiology
Introduction
Point-of-care ultrasound (POCUS) is now a widely used tool in anesthesiology daily practice, since it is cheap, non-invasive and feasible in a wide variety of clinical settings. POCUS is gaining increasing popularity in preoperative anesthetic evaluation as it gives information that may be relevant for patient management such as patients’ cardiovascular function, respiratory pathology, aspiration risk, the presence of deep venous thrombosis or abdominal and genitourinary abnormalities [1, 2].
One of the most interesting applications of pre-anesthesia POCUS is undoubtedly the airway assessment. Preoperative airway evaluation relies on clinical and morphological predictors that often lack of high sensitivity and specificity when utilized alone [3]. Several echographic parameters have been proposed as part of the airway assessment and some of these have demonstrated to be useful in reducing the incidence of unanticipated difficult laryngoscopy [4] or mask ventilation [5, 6]. As a result, airway ultrasound has been included in the latest American Society of Anesthesiologists (ASA) Guidelines for the management of difficult airway [7]. Other applications of airway ultrasound have been recently demonstrated and these include predicting the correct size of the endotracheal tube, confirming tracheal intubation [8] and establishing the correct tube depth [9].
To perform preoperative airway ultrasound evaluation, longitudinal and transverse scans are used, with both medial and lateral approaches. These scans also allow to evaluate anatomical structures close to the airway, providing a lot of additional useful information. These structures include the great vessels (internal jugular veins and carotid arteries), the thyroid gland and the soft tissues of the neck. Anatomical variations or anomalies in these structures may be relevant to the patient’s perioperative management and may alert the physician about unknown or underestimated pathologies. For example, the detection of unknown carotid plaques can help to better define the cardiovascular risk, direct further investigations and modify the anesthetic management. Preoperative visualization of the internal jugular veins can also be useful in identifying unrecognized cardiovascular pathologies as well as defining the best vascular access strategy. Thyroid gland, lymph nodes and soft tissues masses and abnormalities may be relevant in the airway evaluation but can also be useful in recognizing thyroid pathologies that can affect perioperative patient management and in identifying potentially unrecognized oncological pathology which may need further investigation.
In this paper we report a series of relevant ultrasound findings made during a previous study by our group, which focused on the preoperative airway ultrasound evaluation. These findings were in structures close to the airway, included both pathological features and normal anatomical variants and were considered relevant by the practitioner who performed the examination, therefore were properly reported because of their importance in the anesthesia management or in view of potential further investigations. With these data, we would like to discuss the utility of a systematic extension of preoperative airway ultrasound to the important structures adjacent to the airway.
Methods
We performed and subsequently published a prospective observational study, enrolling 230 adult patients selected for abdominal elective surgery between 2017 and 2018 [6]. The primary goal was to verify whether preoperative upper airway ultrasound measurements was useful to predict difficult face mask ventilation (Ethical approval N. 58/2017/O/Sper Protocol VAD). Two anesthetists experienced in airway ultrasound performed an echographic assessment following a standardized protocol. The exam was carried out during the preoperative evaluation, which, according to our hospital protocol, was within the month prior to the scheduled date of surgery. Various ultrasound parameters of the airway were detected. The thickness of the base of the tongue was found to be a predictive parameter of difficult ventilation (cut-off 50 mm) while the jomental distance a protective parameter.
Additionally, using the same ultrasound settings, we extended the assessment to areas close to the airway, excluding the posterior and cranial regions of the neck. Pathological features or unfavorable anatomical variants of the jugular veins, carotid arteries, thyroid, lymph nodes and soft tissues were noted and properly reported. We have termed this evaluation preoperative point-of-care neck ultrasound assessment.
Preoperative point-of-care neck ultrasound is not a comprehensive ultrasound evaluation, but is a quick assessment that answers to specific clinical questions such as:
- Are there vascular anomalies of position and size?
- Are there carotid atheromatous plaques?
- Are there any abnormalities in the jugular venous flow?
- Are there masses?
Preoperative point-of-care neck ultrasound is very rapid (about 1 min) and allows the identification of unknown pathologies or anatomical variants that can play an important role in the patient's perioperative management.
Results
Table 1 shows the main unknown pathological aspects and anatomical alterations detected by preoperative point-of-care neck ultrasound examination of 230 patients awaiting abdominal elective surgery.
Table 1.
Main unknown pathological aspects and anatomical alterations detected by PEAUS examination
| IJV | Total Sample | Medial IJV | SAr posterior to IJVr | Both VJI dilated | IJV echo-contrast | IJV reversed flow | Absence of IJV | IJV thrombosis |
|---|---|---|---|---|---|---|---|---|
| Number | 230 | 14 (6%) | 6 (2.6%) | 8(3.5%) | 3 (1.2%) | 2 (0.9%) | 2(0.9%) | 1 (0.4%) |
| Male/Female | 116/114 | 8(3.4%)/6(2.6%) | 4(1.7%)/2(0.9) | 4(1.7%)/4(1.7%) | 2(0.9%)/1(0.4%) | 1(0.4%)/1(0.4) | 1(0.4)/1(0.4) | 1(0.4%)/0(%) |
| Age (mean) | 54.6 ± 17.1 | 57.1 ± 17.0 | 60.3 ± 11.0 | 58.1 ± 38.1 | 45 ± 16.5 | 56.5 ± 16.3 | 41.5 ± 33.2 | 70 |
| CAROTID | Total Sample | Unknown carotid plaques | NASCET < 50% | NASCET > 50% | Kinked carotid artery | |||
| Number | 230 | 20 (8.6%) | 14(6%) | 6(2.6%) | 1 (0.4%) | |||
| Male/Female | 116/114 | 11(4.8%)/9(3.9%) | 8(3.4%)/6(2.6) | 3(1.2%)/3(1.2) | 0(0%)/1(0.4%) | |||
| Age (mean) | 54.6 ± 17.1 | 64.9 ± 9.6 | 66 ± 8.7 | 62.5 ± 12 | 50 | |||
| THYROID | Total Sample | Unknown nodules | Nodules < 1 cm | Nodules ≥ 1 cm | Large Nodules | I/H risk nodules | Diffuse disease | |
| Number | 230 | 46(20%) | 26(11.3%) | 20(8.7%) | 3(1.3%) | 6 (2.6%) | 7(3.0%) | |
| Male/Female | 116/114 | 22(9.5%)/24(10.4%) | 10(4.3%)/16(7%) | 12(5.2%)/8(3.5%) | 0(0%)/3(1.3%) | 2(0.9%)/4(1.7%) | 2(0.9%)/5(2.1%) | |
| Age (mean) | 54.6 ± 17.1 | 46.4 ± 21 | 43.3 ± 20.6 | 50.5 ± 21.4 | 54.7 ± 15.0 | 40.8 ± 22.5 | 40 ± 13.2 | |
|
CYSTS MASSES |
Total Sample | Thyroglossal duct cyst | Solid lesion | |||||
| Number | 230 | 5(2.2%) | 1(0.4%) | |||||
| Male/Female | 116/114 | 2(0.9%)/3(1.2%) | 0(0%)/1(0.4%) | |||||
| Age (mean) | 54.6 ± 17.1 | 68.4 ± 15.8 | 63 |
Internal jugular veins
The internal jugular veins (IJVs) were visualized in the tract adjacent to the trachea and larynx. Alterations of position, caliber, flow and other pathological aspects were noted. We found that 14 patients (6%) had one or both IJVs medial or antero-medial to the ipsilateral Carotid artery. 6 patients (2.6%) had the distal right internal jugular vein (rIJV) anterior to the right subclavian artery (Fig. 1). 2 patients (0,86%) did not have an internal jugular vein (IJV), while one had partial thrombosis of the rIJV (previous central venous catheter site, Online Resource 1). In 8 patients (3.5%) the IJVs were both dilated with reduced respiratory variation and in 3 of them (1.2%) we found spontaneous echo contrast (Fig. 2A,Online Resource 2). In 2 patients we documented reversed venous flow and one of them also phlebectasia (Fig. 3, Online Resource 3).
Fig. 1.
Right Subclavian Artery (SA) located posterior to the Internal Jugular Vein (IJV) in the distal portion of the neck. This vascular location increases the risk of arterial puncture
Fig. 2.
A Dilation of both internal jugular veins with spontaneous echo contrast. Right Internal Jugular Vein: rIJV, Left Internal Jugular Vein: lIJV, Carotid Artery: CA. B Cardiac POCUS shows a severe pericardial effusion in the same paucisymptomatic patient. See supplementary material (Online Resource 2)
Fig. 3.
Ectasia of the left internal jugular vein (IJV) with reversed flow. CA: Carotid artery A Longitudinal scan B Transverse scan. See supplementary material (Online Resource 3)
Carotid arteries
The carotid arteries were visualized in the tract adjacent to the trachea and larynx. The common carotid artery, the carotid bulb and the proximal part of the internal carotid artery were evaluated. We found that 22 patients (9.6%, 12 male and 10 female) had unknown carotid plaques with thickness > 1.5 mm (Fig. 4). The patients’ mean body mass index was BMIm = 31.5 ± 6. 6 patients (2.6%) had asymptomatic plaques with > 50% NASCET stenosis. In one patient we found a kinked carotid artery.
Fig. 4.
Preoperative point-of-care neck ultrasound allowed to identify an unknown hypoechoic plaque in the distal internal carotid artery. No haemodynamic alterations, NASCET 10%
Thyroid gland
We found that 46 patients (20%) had unknown thyroid nodules. 26 patients had nodules < 1 cm, while 20 had nodules ≥ 1 cm. 3 patients (1.3%) had large nodules displacing the trachea (Online Resource 4). 6 patients (2.6%) had at least one nodule with intermediate to high risk of malignancy (5 of them had an EU-TIRADS 4 nodule while 1 patient had an EU-TIRADS 5 nodule) [10]. We found 7 patients (3.0%) with ultrasound patterns of unknown diffuse thyroid disease (hypoechoic thyroid, irregular echo-structure, irregular margins, increased size).
Extrathyroid soft tissue cysts and masses
We found 5 patients (2.2%) with unknown laryngeal cyst or thyroglossal duct cysts (Fig. 5A, Online Resource 5). In 3 patients the cysts were located anterior to the epiglottis. We also identified a patient with an unknown solid mass anterior to the epiglottis resulting in difficult intubation (Online Resource 6). All these lesions were asymptomatic.
Fig. 5.
A Large cyst of the epiglottis found during preoperative point-of-care neck ultrasound examination. C cyst, M sternohyoid and homohyoidmuscles, E epiglottis. B Direct laryngoscopy. See Online Resource 5
Discussion
Preoperative airway ultrasound is a useful tool for predicting difficult laryngoscopy and / or ventilation, in order to establish an appropriate airway management strategy. Furthermore, extending the evaluation to a preoperative point-of-care neck ultrasound allows for rapid identification of unknown pathologies or anatomical variants useful in the perioperative patient management. Considering the findings shown by this study, a systematic preoperative point-of-care neck ultrasound can always be considered during preoperative airway ultrasound evaluation.
Preoperative ultrasound evaluation of the internal jugular vein is currently recommended as part of the Rapid Central Vein Assessment (RaCeVA) [11] to choose the site for central vascular access (CVA) [12]. Abnormalities such as thrombosis, phlebectasia or complete absence of IJV affect the choice of the insertion site as well as indicate increased thromboembolic risk. Furthermore, changes in the anatomical relationship of the IJV to the carotid or subclavian artery can alert the physician about an increased risk of involuntary arterial puncture and therefore the risk of life-threatening complications such as hematoma, stroke or airway obstruction [13–15]. Including the IJV exam in a preoperative point-of-care neck ultrasound can be helpful in planning the CVA positioning procedure, reducing preparation time for surgery and guide anticoagulant therapy in case of increased thromboembolic or haemorrhagic risk. In addition, preoperative point-of-care neck ultrasound becomes essential if, for any reason, ultrasound is not available in the operating room or if ultrasound is no longer feasible (e.g., appearance of subcutaneous emphysema). Evaluation of IJV during preoperative point-of-care neck ultrasound can also provide important information on volume status and heart function. An increase in the IJV diameter with reduced respiratory variation may indicate central venous congestion due to, for example, systolic or diastolic cardiac dysfunction or right ventricular dysfunction [16–18]. These findings may lead to a preoperative focused cardiology study using a POCUS cardiac approach or a comprehensive echocardiography exam. In our experience, for example, severe pericardial effusion (circumferential 2 cm) was diagnosed with a preoperative cardiac POCUS in a paucisymptomatic patient with dilated IJV, reduced IJVs respiratory variation and IJVs spontaneous echo contrast. (Fig. 2, Online Resource 2). In our case series, patients with IJV impaired flow or thrombosis performed a complete venous color-doppler ultrasound before surgery, while patients with both dilated and rigid IJV (with or without spontaneous ultrasound contrast) also performed an echocardiogram.
Preoperative point-of-care neck ultrasound also evaluated the presence of unknown carotid plaques in the tract adjacent to the trachea and larynx. Both common carotid, carotid bifurcation and distal internal carotid artery have usually been visualized. According to the 2022 ESC Guidelines on cardiovascular assessment of patients undergoing non-cardiac surgery, routine preoperative carotid imaging is not recommended [19], although the presence of carotid plaques is a predictor of cardiovascular and cerebrovascular events [20, 21] and can be used to improve patient cardiovascular risk classification [22]. In our case series, the recognition of atherosclerotic disease helped to better understand the patients' cardiovascular risk and consequently improve the perioperative management. Some patients with unknown carotid plaques underwent a complete supra-aortic trunk ultrasound and cardiac consultation prior to surgery.
Preoperative point-of-care neck ultrasound also includes a brief exploration of the thyroid gland, normally visualized during transverse tracheal scans. Preoperative point-of-care neck ultrasound allows to quickly identify abnormalities in size and structure of the thyroid gland. The finding of large thyroid nodules can be responsible for tracheal deviation and lead to difficult intubation while the finding of diffuse glandular structure alterations can alert about thyroid dysfunction. Currently, thyroid function testing is not routinely recommended in pre-anesthesia examination, however it is indicated when thyroid disease is suspected since hypo or hyperthyroidism have several anesthesiologic implications [23, 24]. For this reason, we have suggested a dosage of thyroid hormones and TSH in patients with ultrasound pattern of diffuse thyroid disease (hypoechoic thyroid, irregular echo structure, irregular margins, increase in size). Finally, ENT surgeon evaluation was required in patients with suspicious unknown thyroid nodules to assess whether further examination was indicated. Note that many unknown thyroid nodules were visualized and some of them had an intermediate to high risk of malignancy.
Finally, a preoperative point-of-care neck ultrasound allowed to identify unknown soft tissue masses or cysts in asymptomatic patients. Those patients were evaluated by the ENT surgeon prior to abdominal surgery. None of them had indication for the removal of the cyst / mass before surgery as they were asymptomatic and with preserved airway. Patients with lesions anterior to the epiglottis had difficult intubation (Fig. 5) as there was an increase in the thickness of the soft tissues anterior to the airway (the thickness of the soft tissues anterior to the epiglottis is a predictor of difficult laryngoscopy [25]).
Limitations
These findings are ancillary to the ultrasound parameters that we searched in our primary study, which was centered on difficult face mask ventilation prediction; so, as a matter of fact, this is an uncontrolled case series and not an observational study. For the same reason, a standardized follow-up was not foreseen after the required additional examinations (e.g., echocardiography, vascular doppler, ENT consultation), so we do not know the real impact of preoperative point-of-care neck ultrasound on subsequent management and patient outcome. Randomized controlled trials are needed to achieve this goal.
Conclusion
Preoperative point-of-care neck ultrasound is fast, inexpensive and non-invasive and can be easily performed by a properly trained professional during the preoperative airway ultrasound evaluation. Although preoperative point-of-care neck ultrasound needs further investigations in order demonstrate its real impact on patients’ perioperative management, it may seem illogical to preclude the knowledge of certain pathological features or anatomical variants, especially if this knowledge can be easily achieved during a valuable preoperative evaluation such as airway ultrasound.
Supplementary Information
Below is the link to the electronic supplementary material.
Author contributions
All authors contributed to the study conception and design.
Funding
The authors declare that no funds, grants, or other support were received during the preparation of this manuscript.
Data availability
The data that support the findings of this study are available from the corresponding author, Filippo Susi, upon reasonable request.
Declarations
Conflict of interest
The authors have no relevant financial or non-financial interests to disclose.
Ethical approval
These data are ancillary to an observational study carried out by our group (Ethical approval N. 58/2017/O/Sper Protocol VAD). Written informed consent was obtained from all the patients, including the possibility of image publication in an anonymous form.
Footnotes
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Data Availability Statement
The data that support the findings of this study are available from the corresponding author, Filippo Susi, upon reasonable request.