Cervical spine movement during laryngoscopy using the Airway Scope compared with the Macintosh laryngoscope

A comparative study to evaluate the cervical spine movements during laryngoscopy using Macintosh and Airtraq laryngoscopes

Background and Aim

Intubation with Macintosh requires flexing the lower cervical spine and extending the atlanto-occipital joint to create a "line of sight." Primary aim of study was to compare the extent of cervical spine movement during laryngoscopy using conventional Macintosh laryngoscope and Airtraq.

Material and Methods

A total of 25 patients of either sex between the age group of 18 and 60 years, having American Society of Anesthesiologists (ASA) physical status of Grade-I and Grade-II, scheduled for elective surgery under image control requiring general anesthesia and intubation were enrolled. A baseline image of the lateral cervical spine including the first four cervical vertebrae was taken by an image intensifier. After administration of general anesthesia, laryngoscopy was first performed using a Macintosh laryngoscope and a second X-ray image of the lateral cervical spine was taken. The second laryngoscopy using a Airtraq laryngoscope was done and the third image of the lateral cervical spine was taken. Angles between occiput and C1; C1 and C2; C2 and C3; C3 and C4; and occiput and C4 were calculated. Atlanto-occipital distance (AOD) was calculated as the distance between occiput and C1.

Results

Macintosh showed greater cervical movement as compared with Airtraq but a significant difference in the movement was observed at C2-C3 and C0-C4. Baseline mean AOD was 2.21 ± 1.25 mm, after Macintosh and Airtraq laryngoscopy was found to be 1.13 ± 0.60 and 1.6 ± 0.78 mm, respectively, and was found to be significant (P < 0.05).

Conclusion

We conclude that Airtraq allows intubation with less movement of the upper cervical spine makes Airtraq preferred equipment for intubation in patients with a potential cervical spine injury.

Cervical spine movements during laryngoscopy and orotracheal intubation: a systematic review and meta-analysis

BACKGROUND

Airway management is challenging in trauma patients because of the fear of worsening cervical spinal cord damage. Video-integrated and optic-integrated devices and intubation laryngeal mask airways have been proposed as alternatives to direct laryngoscopy with the Macintosh laryngoscope (MAC). We performed a meta-analysis to clarify which devices cause less cervical movement during airway management.

METHODS

We searched MEDLINE, Cochrane Central, Embase and LILACS from inception to January 2022. We selected randomised controlled trials comparing alternative devices with the MAC for cervical movement from C0 to C5 in adult patients, evaluated by radiological examination. Additionally, cervical spine immobilisation (CSI) techniques were evaluated. We used the Cochrane Risk of Bias Tool to evaluate the risk of bias, and the principles of the Grading of Recommendations, Assessment, Development, and Evaluations system to assess the quality of the body of evidence.

RESULTS

Twenty-one studies (530 patients) were included. Alternative devices caused statistically significantly less cervical movement than MAC during laryngoscopy with mean differences of -3.43 (95% CI -4.93 to -1.92) at C0-C1, -3.19 (-4.04 to -2.35) at C1-C2, -1.35 (-2.19 to -0.51) at C2-C3, and -2.61 (-3.62 to -1.60) at C3-C4; and during intubation: -3.60 (-5.08 to -2.12) at C0-C1, -2.38 (-3.17 to -1.58) at C1-C2, -1.20 (-2.09 to -0.31) at C2-C3. The Airtraq and the Intubation Laryngeal Mask Airway caused statistically significant less movement than MAC restricted to some cervical segments, as well as CSI. Heterogeneity was low to moderate in most results. The quality of the body of evidence was 'low' and 'very low'.

CONCLUSIONS

Compared with the MAC, alternative devices caused less movement during laryngoscopy (C0-C4) and intubation (C0-C3). Due to the high risk of bias and the very low grade of evidence of the studies, further research is necessary to clarify the benefit of each device and to determine the efficacy of cervical immobilisation during airway management.

Intubation biomechanics: Computational modeling to identify methods to minimize cervical spine motion and spinal cord strain during laryngoscopy and tracheal intubation in an intact cervical spine

STUDY OBJECTIVE

To minimize the risk of cervical spinal cord injury in patients who have cervical spine pathology, minimizing cervical spine motion during laryngoscopy and tracheal intubation is commonly recommended. However, clinicians may better aim to reduce cervical spinal cord strain during airway management of their patients. The aim of this study was to predict laryngoscope force characteristics (location, magnitude, and direction) that would minimize cervical spine motions and cord strains.

DESIGN

We utilized a computational model of the adult human cervical spine and spinal cord to predict intervertebral motions (rotation [flexion/extension] and translation [subluxation]) and cord strains (stretch and compression) during laryngoscopy.

INTERVENTIONS

Routine direct (Macintosh) laryngoscopy conditions were defined by a specific force application location (mid-C3 vertebral body), magnitude (48.8 N), and direction (70 degrees). Sixty laryngoscope force conditions were simulated using 4 force locations (cephalad and caudad of routine), 5 magnitudes (25-200% of routine), and 3 directions (50, 70, 90 degrees).

MAIN RESULTS

Under all conditions, extension at Oc-C1 and C1-C2 were greater than in all other cervical segments. Decreasing force magnitude to values reported for indirect laryngoscopes (8-17 N) decreased cervical extension to ~50% of routine values. The cervical cord was most likely to experience potentially injurious compressive strain at C3, but force magnitudes ≤50% of routine (≤24.4 N) decreased strain in C3 and all other cord regions to non-injurious values. Changing laryngoscope force locations and directions had minor effects on motion and strain.

CONCLUSIONS

The model predicts clinicians can most effectively minimize cervical spine motion and cord strain during laryngoscopy by decreasing laryngoscope force magnitude. Very low force magnitudes (<5 N, ~10% of routine) are necessary to decrease overall cervical extension to <50% of routine values. Force magnitudes ≤24.4 N (≤50% of routine) are predicted to help prevent potentially injurious compressive cord strain.

A two-handed airway maneuver of mandibular advancement and mouth opening in the neutral neck position for immobilization of the cervical spine

PURPOSE

Immobilization of the cervical spine after trauma is recommended as standard care to prevent secondary injury. We tested the hypothesis that a two-handed airway maneuver, consisting of mandibular advancement and mouth opening in the neutral neck position, would minimize changes in the angle of the cervical vertebrae at the C0/4 level and tidal volume in non-obese patients under anesthesia with neuromuscular blockade.

METHODS

Twenty consecutive patients without cervical spine injury undergoing general anesthesia were enrolled and evaluated. The primary variable was change in the angle of the cervical vertebrae at the C0/4 level during mask ventilation using the modified two-handed technique. Secondary variables included changes in the angles of the cervical vertebrae at each level between C0 and C4, anterior movement of the vertebral bodies, change in the angle between the head and neck, change in the pharyngeal airway space, and tidal volume during mask ventilation.

RESULTS

The two-handed airway maneuver of mandibular advancement and mouth opening resulted in statistically significant changes in the angle of the cervical spine at the C0/4 level (3.2 ± 3.0 degrees, P < 0.001) and the C3/4 level (1.4 ± 2.2 degrees, P = 0.01). The two-handed airway maneuver provided adequate mask ventilation without anterior movement of the vertebral bodies.

CONCLUSION

Our study suggests that a two-handed airway maneuver of mandibular advancement and mouth opening in the neutral neck position results in only slight change in the cervical vertebral angle at the C0/4 level in non-obese patients under general anesthesia with neuromuscular blockade.

Practice and outcomes of airway management in patients with cervical orthoses

BACKGROUND/PURPOSE

Increasing evidence indicates an association of video laryngoscopy with the success rate of airway management in patients with neck immobilization. Nevertheless, clinical practice protocols for tracheal intubation in patients immobilized using various types of cervical orthoses and the outcomes remain unclear.

METHODS

We retrospectively assessed the tracheal intubation techniques selected for patients immobilized using cervical orthoses from 2015 to 2018. The endpoints were the intubation outcomes of the different techniques and the factors associated with the selection of the technique.

RESULTS

We included 218 patients, 118 of whom wore halo vest braces (halo vest group) and 100 wore cervical collars (collar group). GlideScope video laryngoscopy (GVL) and fiberoptic bronchoscopy (FOB) were the initial intubation methods in 98 and 120 patients, respectively. GVL had a higher first-attempt success rate than did FOB in the collar group (p = 0.002) but not in the halo vest group (p = 0.522). GVL was associated with a lower risk of episodes of SaO₂< 90% (adjusted relative risk [aRR], 0.11; 95% CI, 0.02-0.67; p = 0.016) and shorter intubation time (aRR, -3.52; 95% CI, -4.79∼-2.25; p < 0.001) in the collar group. However, in the halo vest group, more frequent requirement of a rescue technique (p = 0.002) and necessity of patient awakening (p = 0.001) was noted when GVL was used. Use of the halo vest brace and noting of severe cord compression were independent predictors of the initial selection of FOB.

CONCLUSION

Caution should be exercised when using GVL for tracheal intubation in patients immobilized using halo vest braces.

Comparison of the Contact Force Exerted on Teeth by Conventional Macintosh Laryngoscope Versus Video Laryngoscopes

During laryngoscopy, the laryngoscope blade sometimes comes in contact with the teeth, fracturing or dislocating them. However, no studies have compared the effects of newly marketed video laryngoscopes and the Macintosh laryngoscope (Mac) on teeth. In this study, we measured and compared the force exerted on the teeth of an intubating manikin by the Mac, the Airway Scope (Pentax), and the McGrath MAC (Covidien). The mean force exerted was 141.1 ± 15.7 kg by the Mac, 39.2 ± 10.3 kg by the Airway Scope, and 48.7 ± 6.7 kg by the McGrath MAC. No significant difference was observed between the Airway Scope and the McGrath MAC. When the Mac is inserted, the glottis has to be visually located from outside the oral cavity. However, a significant force is not necessary when inserting video laryngoscopes because a camera is mounted on the blade tip. In this laboratory model, the lower force exerted by the video laryngoscopes should contribute to a reduction in their impact on fracture or dislocation of teeth.

Management of Anaesthesia

Surgical treatment of the craniovertebral junction (CVJ) requires excellent management by the anaesthetist. Patients undergoing this type of surgery have a wide range of concomitant diseases. Therefore, before proceeding to CVJ surgery, it is recommended to analyse the clinical aspects of the patient that could complicate the outcome of the surgical procedure.In this paper we aim to establish what constitutes the best surgical and anaesthesia management of these patients. We consider airway management, trying to identify the gold standard for the patient. We also consider the most appropriate intraoperative approach to guarantee the best management of the patient.

Efficacy of Pentax airway scope versus Macintosh laryngoscope when used by novice personnel: A prospective randomized controlled study

Objective

To determine whether intubation education using the Pentax Airway Scope (AWS) in normal airways is more useful than direct laryngoscopy (Macintosh laryngoscope) in novice personnel.

Methods

Eleven intern doctors without intubation experience performed 60 sequential intubations with each device on a manikin and 10 sequential intubations in adult patients. The time required for successful intubation, percentage of glottic opening (POGO) score, number of intubation attempts, and number of dental injuries were analyzed for each intubation technique.

Results

The mean (standard deviation) time required for successful intubation decreased as the number of intubations increased and was significantly shorter with the Pentax AWS than direct laryngoscope [22.6 (7.3) vs. 29.6 (10.0) and 33.0 (8.0) vs. 44.7 (5.6) s, respectively] in both the manikin and clinical studies. The Pentax AWS was also associated with higher POGO scores than the direct laryngoscope [81.7 (8.9) vs. 55.1 (13.2) and 80.9 (9.7) vs. 49.6 (16.5), respectively] and fewer intubation attempts. Fewer dental injuries occurred with the Pentax AWS in the manikin study.

Conclusions

Novices performed intubation more rapidly and easily with an improved laryngeal view using the Pentax AWS. We suggest that intubation education with video laryngoscopy should be mandatory along with direct laryngoscope training.

Anesthetic considerations for patients with acute cervical spinal cord injury

Anesthesiologists work to prevent or minimize secondary injury of the nervous system and improve the outcome of medical procedures. To this end, anesthesiologists must have a thorough understanding of pathophysiology and optimize their skills and equipment to make an anesthesia plan. Anesthesiologists should conduct careful physical examinations of patients and consider neuroprotection at preoperative interviews, consider cervical spinal cord movement and compression during airway management, and suggest awake fiberoptic bronchoscope intubation for stable patients and direct laryngoscopy with manual in-line immobilization in emergency situations. During induction, anesthesiologists should avoid hypotension and depolarizing muscle relaxants. Mean artery pressure should be maintained within 85-90 mmHg (1 mmHg = 0.133 kPa; vasoactive drug selection and fluid management). Normal arterial carbon dioxide pressure and normal blood glucose levels should be maintained. Intraoperative neurophysiological monitoring is a useful option. Anesthesiologists should be attentive to postoperative respiratory insufficiency (carefully considering postoperative extubation), thrombus, and infection. In conclusion, anesthesiologists should carefully plan the treatment of patients with acute cervical spinal cord injuries to protect the nervous system and improve patient outcome.

Videolaryngoscopy versus direct laryngoscopy for adult patients requiring tracheal intubation

BACKGROUND

Successful tracheal intubation during general anaesthesia traditionally requires a line of sight to the larynx attained by positioning the head and neck and using a laryngoscope to retract the tongue and soft tissues of the floor of the mouth. Difficulties with intubation commonly arise, and alternative laryngoscopes that use digital and/or fibreoptic technology have been designed to improve visibility when airway difficulty is predicted or encountered. Among these devices, a rigid videolaryngoscope (VLS) uses a blade to retract the soft tissues and transmits a lighted video image to a screen.

OBJECTIVES

Our primary objective was to assess whether use of videolaryngoscopy for tracheal intubation in adults requiring general anaesthesia reduces risks of complications and failure compared with direct laryngoscopy. Our secondary aim was to assess the benefits and risks of these devices in selected population groups, such as adults with obesity and those with a known or predicted difficult airway.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE and Embase on 10 February 2015. Our search terms were relevant to the review question and were not limited by outcomes. We carried out clinical trials register searches and forward and backward citation tracking. We reran the search on 12 January 2016; we added potential new studies of interest from the 2016 search to a list of 'Studies awaiting classification', and we will incorporate these studies into the formal review during the review update.

SELECTION CRITERIA

We considered all randomized controlled trials and quasi-randomized studies with adult patients undergoing laryngoscopy performed with a VLS or a Macintosh laryngoscope in a clinical, emergency or out-of-hospital setting. We included parallel and cross-over study designs.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data, consulting a third review author to resolve disagreements. We used standard Cochrane methodological procedures, including assessment of risk of bias.

MAIN RESULTS

We included 64 studies identified during the 2015 search that enrolled 7044 adult participants and compared a VLS of one or more designs with a Macintosh laryngoscope. We identified 38 studies awaiting classification and seven ongoing studies. Of the 64 included studies, 61 included elective surgical patients, and three were conducted in an emergency setting. Among 48 studies that included participants without a predicted difficult airway, 15 used techniques to simulate a difficult airway. Seven recruited participants with a known or predicted difficult airway, and the remaining studies did not specify or included both predicted and not predicted difficult airways. Only two studies specifically recruited obese participants. It was not possible to blind the intubator to the device, and we noted a high level of inevitable heterogeneity, given the large number of studies.Statistically significantly fewer failed intubations were reported when a VLS was used (Mantel-Haenszel (M-H) odds ratio (OR), random-effects 0.35, 95% confidence Interval (CI) 0.19 to 0.65; 38 studies; 4127 participants), and fewer failed intubations occurred when a VLS was used in participants with an anticipated difficult airway (M-H OR, random-effects 0.28, 95% CI 0.15 to 0.55; six studies; 830 participants). We graded the quality of this evidence as moderate on the basis of the GRADE system. Failed intubations were fewer when a VLS was used in participants with a simulated difficult airway (M-H OR, random-effects 0.18, 95% CI 0.04 to 0.77; nine studies; 810 participants), but groups with no predicted difficult airway provided no significant results (M-H OR, random-effects 0.61, 95% CI 0.22 to 1.67; 19 studies; 1743 participants).Eight studies reported on hypoxia, and only three of these described any events; results showed no differences between devices for this outcome (M-H OR, random-effects 0.39, 95% CI 0.10 to 1.44; 1319 participants). Similarly, few studies reported on mortality, noting no differences between devices (M-H OR, fixed-effect 1.09, 95% CI 0.65 to 1.82; two studies; 663 participants), and only one study reporting on the occurrence of respiratory complications (78 participants); we graded these three outcomes as very low quality owing to lack of data. We found no statistically significant differences between devices in the proportion of successful first attempts (M-H OR, random-effects 1.27, 95% CI 0.77 to 2.09; 36 studies; 4731 participants) nor in those needing more than one attempt. We graded the quality of this evidence as moderate. Studies reported no statistically significant differences in the incidence of sore throat in the postanaesthesia care unit (PACU) (M-H OR, random-effects 1.00 (95% CI 0.73 to 1.38); 10 studies; 1548 participants) nor at 24 hours postoperatively (M-H OR random-effects 0.54, 95% CI 0.27 to 1.07; eight studies; 844 participants); we graded the quality of this evidence as moderate. Data combined to include studies of cross-over design revealed statistically significantly fewer laryngeal or airway traumas (M-H OR, random-effects 0.68, 95% CI 0.48 to 0.96; 29 studies; 3110 participants) and fewer incidences of postoperative hoarseness (M-H OR, fixed-effect 0.57, 95% CI 0.36 to 0.88; six studies; 527 participants) when a VLS was used. A greater number of laryngoscopies performed with a VLS achieved a view of most of the glottis (M-H OR, random-effects 6.77, 95% CI 4.17 to 10.98; 22 studies; 2240 participants), fewer laryngoscopies performed with a VLS achieved no view of the glottis (M-H OR, random-effects 0.18, 95% CI 0.13 to 0.27; 22 studies; 2240 participants) and the VLS was easier to use (M-H OR, random-effects 7.13, 95% CI 3.12 to 16.31; seven studies; 568 participants).Although a large number of studies reported time required for tracheal intubation (55 studies; 6249 participants), we did not present an effects estimate for this outcome owing to the extremely high level of statistical heterogeneity (I2 = 96%).

AUTHORS' CONCLUSIONS

Videolaryngoscopes may reduce the number of failed intubations, particularly among patients presenting with a difficult airway. They improve the glottic view and may reduce laryngeal/airway trauma. Currently, no evidence indicates that use of a VLS reduces the number of intubation attempts or the incidence of hypoxia or respiratory complications, and no evidence indicates that use of a VLS affects time required for intubation.

Airway management in a patient with nuchal, interspinous, and flavum ligament rupture by a sickle: a case report

BACKGROUND

Penetrating neck injury is an important trauma subset but is relatively rare, especially when involving the posterior cervical column. Rupture of the neck restraints, including the interspinous and flavum ligaments, can create serious cervical instability that requires special consideration when managing the airway. However, no detailed information regarding airway management in patients with profound posterior neck muscle laceration and direct cervical ligament disruption by an edged weapon is yet available in the literature.

CASE PRESENTATION

A 63-year-old Japanese man attempted to cut off his head using a sickle after drinking a copious amount of alcohol. On admission, his posterior vertebral column was grossly exposed and the lacerated tissues were actively bleeding, resulting in severe hypovolemic shock. We used a rapid-sequence intubation technique with direct laryngoscopy while manual in-line stabilization of his head and neck was maintained by several people. Surgical exploration revealed nuchal, interspinous, and flavum ligament rupture between his fourth and fifth cervical vertebrae, but no injury to the great vessels was present. The major source of bleeding was a site of oozing from his trapezius and splenius muscles. After surgical hemostasis, wound repair, and subsequent intensive care, our patient was discharged home without any neurological sequelae.

CONCLUSIONS

Deficits of the neck restraints can cause cervical spine subluxation and dislocation secondary to neck movement. Thus, the key to successful airway management in such a scenario is minimization of neck movement to prevent further neurological impairment. We successfully managed an airway using a conventional but trusted endotracheal intubation strategy in a patient with multiple traumas and a suspected spinal cord injury. This case also illustrates that, even when great vessel injury is absent, severe hypovolemic shock may occur after profound neck muscle laceration, requiring immediate surgical intervention.

Anesthetic Management of a Patient With Takayasu Arteritis

Takayasu arteritis is a rare chronic progressive panendarteritis involving the aorta and its main branches. Anesthesia in patients with this disease can be complicated by severe uncontrolled hypertension, end-organ dysfunction, and stenosis of major blood vessels. In this case, general anesthesia was induced with sevoflurane and remifentanil without complications. To prevent intraoperative complications, we conducted intubation with a rigid video laryngoscope with careful consideration of the concentrations of analgesics and sedatives used. This case demonstrates the importance of anesthetic techniques for maintaining adequate tissue perfusion without hemodynamic changes in the anesthetic management of patients with Takayasu arteritis.

Lateral Cervical Spine Radiography to Demonstrate Absence of Bony Displacement After Intubation in a Patient with an Acute Type III Odontoid Fracture

A 72-year-old patient with an acute traumatic Type III odontoid fracture presented to the operating room for an urgent orthopedic procedure with a history of uncontrolled gastroesophageal reflux, a full stomach, and active vomiting. Rather than fiberoptic intubation, a rapid sequence intubation with manual inline stabilization was performed using a videolaryngoscope. A lateral cervical spine radiograph immediately after intubation showed no change in alignment of the fracture of C1-C2. In the presence of cervical spine instability, a postintubation radiograph provides assurance that the cervical spine is appropriately aligned during subsequent surgery.

Alternative intubation techniques vs Macintosh laryngoscopy in patients with cervical spine immobilization: systematic review and meta-analysis of randomized controlled trials

Background. Immobilization of the cervical spine worsens tracheal intubation conditions. Various intubation devices have been tested in this setting. Their relative usefulness remains unclear.

Methods. We searched MEDLINE, EMBASE, and the Cochrane Library for randomized controlled trials comparing any intubation device with the Macintosh laryngoscope in human subjects with cervical spine immobilization. The primary outcome was the risk of tracheal intubation failure at the first attempt. Secondary outcomes were quality of glottis visualization, time until successful intubation, and risk of oropharyngeal complications.

Results. Twenty-four trials (1866 patients) met inclusion criteria. With alternative intubation devices, the risk of intubation failure was lower compared with Macintosh laryngoscopy [risk ratio (RR) 0.53; 95% confidence interval (CI) 0.35–0.80]. Meta-analyses could be performed for five intubation devices (Airtraq, Airwayscope, C-Mac, Glidescope, and McGrath). The Airtraq was associated with a statistically significant reduction of the risk of intubation failure at the first attempt (RR 0.14; 95% CI 0.06–0.33), a higher rate of Cormack–Lehane grade 1 (RR 2.98; 95% CI 1.94–4.56), a reduction of time until successful intubation (weighted mean difference −10.1 s; 95% CI −3.2 to −17.0), and a reduction of oropharyngeal complications (RR 0.24; 95% CI 0.06–0.93). Other devices were associated with improved glottis visualization but no statistically significant differences in intubation failure or time to intubation compared with conventional laryngoscopy.

Conclusions. In situations where the spine is immobilized, the Airtraq device reduces the risk of intubation failure. There is a lack of evidence for the usefulness of other intubation devices.

Neurological deterioration during intubation in cervical spine disorders

Anaesthesiologists are often involved in the management of patients with cervical spine disorders. Airway management is often implicated in the deterioration of spinal cord function. Most evidence on neurological deterioration resulting from intubation is from case reports which suggest only association, but not causation. Most anaesthesiologists and surgeons probably believe that the risk of spinal cord injury (SCI) during intubation is largely due to mechanical compression produced by movement of the cervical spine. But it is questionable that the small and brief deformations produced during intubation can produce SCI. Difficult intubation, more frequently encountered in patients with cervical spine disorders, is likely to produce greater movement of spine. Several alternative intubation techniques are shown to improve ease and success, and reduce cervical spine movement but their role in limiting SCI is not studied. The current opinion is that most neurological injuries during anaesthesia are the result of prolonged deformation, impaired perfusion of the cord, or both. To prevent further neurological injury to the spinal cord and preserve spinal cord function, minimizing movement during intubation and positioning for surgery are essential. The features that diagnose laryngoscopy induced SCI are myelopathy present on recovery, short period of unconsciousness, autonomic disturbances following laryngoscopy, cranio-cervical junction disease or gross instability below C3. It is difficult to accept or refute the claim that neurological deterioration was induced by intubation. Hence, a record of adequate care at laryngoscopy and also perioperative period are important in the event of later medico-legal proceedings.

Intubation biomechanics: laryngoscope force and cervical spine motion during intubation with Macintosh and Airtraq laryngoscopes

INTRODUCTION

Laryngoscopy and endotracheal intubation in the presence of cervical spine instability may put patients at risk of cervical cord injury. Nevertheless, the biomechanics of intubation (cervical spine motion as a function of applied force) have not been characterized. This study characterized and compared the relationship between laryngoscope force and cervical spine motion using two laryngoscopes hypothesized to differ in force.

METHODS

Fourteen adults undergoing elective surgery were intubated twice (Macintosh, Airtraq). During each intubation, laryngoscope force, cervical spine motion, and glottic view were recorded. Force and motion were referenced to a preintubation baseline (stage 1) and were characterized at three stages: stage 2 (laryngoscope introduction); stage 3 (best glottic view); and stage 4 (endotracheal tube in trachea).

RESULTS

Maximal force and motion occurred at stage 3 and differed between the Macintosh and Airtraq: (1) force: 48.8 ± 15.8 versus 10.4 ± 2.8 N, respectively, P = 0.0001; (2) occiput-C5 extension: 29.5 ± 8.5 versus 19.1 ± 8.7 degrees, respectively, P = 0.0023. Between stages 2 and 3, the motion/force ratio differed between Macintosh and Airtraq: 0.5 ± 0.2 versus 2.0 ± 1.4 degrees/N, respectively; P = 0.0006.

DISCUSSION

The relationship between laryngoscope force and cervical spine motion is: (1) nonlinear and (2) differs between laryngoscopes. Differences between laryngoscopes in motion/force relationships are likely due to: (1) laryngoscope-specific cervical extension needed for intubation, (2) laryngoscope-specific airway displacement/deformation needed for intubation, and (3) cervical spine and airway tissue viscoelastic properties. Cervical spine motion during endotracheal intubation is not directly proportional to force. Low-force laryngoscopes cannot be assumed to result in proportionally low cervical spine motion.

Awake tracheal intubation using Pentax airway scope in 30 patients: A Case series

BACKGROUND AND AIMS

Pentax airway scope (AWS) has been successfully used for managing difficult intubations. In this case series, we aimed to evaluate the success rate and time taken to complete intubation, when AWS was used for awake tracheal intubation.

METHODS

We prospectively evaluated the use of AWS for awake tracheal intubation in 30 patients. Indication for awake intubation, intubation time, total time to complete tracheal intubation, laryngoscopic view (Cormack and Lehane grade), total dose of local anaesthetic used, anaesthetists rating and patient's tolerance of the procedure were recorded.

RESULTS

The procedure was successful in 25 out of the 30 patients (83%). The mean (standard deviation) intubation time and total time to complete the tracheal intubation was 5.4 (2.4) and 13.9 (3.7) min, respectively in successful cases. The laryngeal view was grade 1 in 24 and grade 2 in one of 25 successful intubations. In three out of the five patients where the AWS failed, awake tracheal intubation was successfully completed with the assistance of flexible fibre optic scope (FOS).

CONCLUSION

Awake tracheal intubation using AWS was successful in 83% of patients. Success rate can be further improved using a combination of AWS and FOS. Anaesthesiologists who do not routinely use FOS may find AWS easier to use for awake tracheal intubation using an oral route.

A review of video laryngoscopes relevant to the intensive care unit

The incidence of difficult direct intubation in the intensive care unit (ICU) is estimated to be as high as 20%. Recent advances in video-technology have led to the development of video laryngoscopes as new intubation devices to assist in difficult airway management. Clinical studies indicate superiority of video laryngoscopes relative to conventional direct laryngoscopy in selected patients. They are therefore an important addition to the armamentarium of any clinician performing endotracheal intubation. We present a practical review of commonly available video laryngoscopes with respect to design, clinical efficacy, and safety aspects relevant to their use in the ICU.

Assessment of cervical spine movement during laryngoscopy with Macintosh and Truview laryngoscopes

Background:

Truview laryngoscope provides an indirect view of the glottis and will cause less cervical spine movement since a ventral lifting force will not be required to visualize the glottis compared to Macintosh laryngoscope.

Materials and Methods:

A randomized crossover study to assess the degree of movement of cervical spine during endotracheal intubation with Truview laryngoscope was conducted in 25 adult ASA-I patients. After a standard anesthetic technique laryngoscopy was performed twice in each patient using in turn both the Macintosh and Truview laryngoscopes. A baseline radiograph with the head and neck in a neutral position was followed by a second radiograph taken during each laryngoscopy. An experienced radiologist analyzed and measured the cervical movement.

Results:

Significant cervical spine movement occurred at all segments when compared to the baseline with both the Macintosh and Truview laryngoscopes (P < 0.001). However, the movement was significantly less with Truview compared to the Macintosh laryngoscope at C₀–C₁ (21%; P = 0.005) and C₁–C₂ levels (32%; P = 0.009). The atlantooccipital distance (AOD) traversed while using Truview laryngoscope was significantly less than with Macintosh blade (26%; P = 0.001). Truview blade produced a better laryngoscopic view (P = 0.005) than Macintosh blade, but had a longer time to laryngoscopy (P = 0.04).

Conclusion:

Truview laryngoscope produced a better laryngoscopic view of glottis as compared with Macintosh laryngoscopy. It also produced significantly less cervical spine movement at C₀–C₁ and C₁–C₂ levels than with Macintosh laryngoscope in patients without cervical spine injury and without manual in-line stabilization (MILS). Further studies are warranted with Truview laryngoscope using MILS.

Anesthetic considerations in acute spinal cord trauma

Patients with actual or potential spinal cord injury (SCI) are frequently seen at adult trauma centers, and a large number of these patients require operative intervention. All polytrauma patients should be assumed to have an SCI until proven otherwise. Pre-hospital providers should take adequate measures to immobilize the spine for all trauma patients at the site of the accident. Stabilization of the spine facilitates the treatment of other major injuries both in and outside the hospital. The presiding goal of perioperative management is to prevent iatrogenic deterioration of existing injury and limit the development of secondary injury whilst providing overall organ support, which may be adversely affected by the injury. This review article explores the anesthetic implications of the patient with acute SCI. A comprehensive literature search of Medline, Embase, Cochrane database of systematic reviews, conference proceedings and internet sites for relevant literature was performed. Reference lists of relevant published articles were also examined. Searches were carried out in October 2010 and there were no restrictions by study design or country of origin. Publication date of included studies was limited to 1990–2010.

Upper cervical spine movement during intubation with different airway devices

Prevention of secondary neurologic injury is critical during the airway management of a trauma patient. Trauma patients are assumed to have an unstable cervical spine (C-spine) until proven otherwise: orotracheal intubation during airway management may result in a certain amount of C-spine movement. This study, therefore, aimed to compare C-spine movement within different advanced airway devices (Macintosh blade, McCoy Blade, LMA, I-LMA, and Combitube) during airway management.

MATERIALS AND METHODS

A total of 3 fresh frozen cadavers were used. The cadavers were consecutively intubated by 4 different postgraduate year residents with LMA4, I-LMA5, Combitube (37F), Macintosh 3, and McCoy blades. The cinefluoroscopic view of the entire intubation process was recorded, and vertebral body angles were calculated.

RESULTS

At the C0C1 level, compared with the McCoy laryngoscope (median, 7°), the LMA (median, 2.5°) and the Combitube (median, 1.5°) caused less extension of the cervical vertebra. In addition, the Combitube (median, -1°) and the I-LMA (median, -2°) caused less extension of the C2C3 region when compared with the Macintosh laryngoscope (median, 3°). There was no significant difference between groups at the C1C2, C3C4, and C4C5 segments.

CONCLUSION

Supraglottic devices used during airway management cause C-spine movement less or equal to conventional laryngoscopes. Furthermore, because of ease of training and blind insertion, supraglottic devices can be safely used with trauma patients when C-spine integrity is a concern.

[Anesthesiological considerations for patients with trisomy 21 (Down syndrome)]

The most common chromosomal abnormality is trisomy 21 which is also known as Down syndrome and occurs in approximately 1 in 800 births. The majority of the resulting disabling conditions cannot be cured and affect people of all ages, ethnicity and economic levels. Life expectancy has increased with advances in medical care in the same way as in the rest of the population. One of the major tasks for health care professionals is to help these differently abled children and their families function in the most effective way possible as they learn to accept the limitations imposed by a persistent disability. Signs and symptoms of trisomy 21 are very variable based on the trias of mental retardation to a variable degree, hand anomalies and cardiac complications. Other abnormalities are atlantoaxial instability (AAI), tracheal stenosis, a predisposition to respiratory complications, chronic hypothyroidism, microgenia and macroglossia. These conditions are relevant to anesthetic procedures and patients with Down syndrome and their families have specific expectations and attitudes towards medical and anesthetic treatment.

Use of video-assisted intubation devices in the management of patients with trauma

Patients with trauma may have airways that are difficult to manage. Patients with blunt trauma are at increased risk of unrecognized cervical spine injury, especially patients with head trauma. Manual in-line stabilization reduces cervical motion and should be applied whenever a cervical collar is removed. All airway interventions cause some degree of cervical spine motion. Flexible fiberoptic intubation causes the least cervical motion of all intubation approaches, and rigid video laryngoscopy provides a good laryngeal view and eases intubation difficulty. In emergency medicine departments, video laryngoscopy use is growing and observational data suggest an improved success rate compared with direct laryngoscopy.

Video Laryngoscopy in the Prehospital Setting

In the prehospital setting, the emergency care provider must anticipate that some patients will manifest with difficult airways. The use of video laryngoscopy to secure an airway in the prehospital setting has not been explored widely, but has the potential to be a useful tool. This article briefly reviews some of the major video laryngoscopes on the market and their usefulness in the prehospital setting. Studies and case reports indicate that the video laryngoscope is a promising device for emergency intubation, and it has been predicted that, in the future, video laryngoscopy will dominate the field of emergency airway management.

Direct laryngoscopy always should be retained as a primary skill; however, the video laryngoscope has the potential to be a good primary choice for the patient with potential cervical spine injuries or limited jaw or spine mobility, and in the difficult-to-access patient.The role of video laryngoscopes in securing an airway in head and neck trauma victims in the prehospital setting has yet to be determined, but offers interesting possibilities. Further clinical studies are necessary to evaluate its role in airway management by prehospital emergency medical services.

Airway management in neuroanesthesiology

Airway management for neuroanesthesiology brings together some key principles that are shared throughout neuroanesthesiology. This article appropriately targets the cervical spine with associated injury and the challenges surrounding airway management. The primary focus of this article is on the unique airway management obstacles encountered with cervical spine injury or cervical spine surgery, and unique considerations regarding functional neurosurgery are addressed. Furthermore, topics related to difficult airway management for those with rheumatoid arthritis or pituitary surgery are reviewed.

Airway scope laryngoscopy under manual inline stabilization and cervical collar immobilization: a crossover in vivo cinefluoroscopic study

BACKGROUND

Direct laryngoscopy along with manual inline stabilization (MIS) is currently the standard care for patients with suspected neck injuries. However, cervical collar immobilization is more commonly performed in the prehospital environment, and its early removal is necessary before intubation. We hypothesized that if usability of Airway Scope (AWS) in a difficult airway could also bring merits to intubation under cervical collar immobilization, unnecessary risk caused by the removal of a neck collar may be prevented.

METHODS

In this crossover study, 30 consenting patients presenting for surgery were assigned to undergo intubation using AWS. Neck was stabilized manually and by a neck collar in a random order before laryngoscopy was performed by the same anesthesiologist. Measurements include interincisor distance (IID), success rate, intubation time, and fluoroscopic examination of the upper and middle cervical spine.

RESULTS

IID was notably narrower after application of a neck collar (mean ± SE: MIS, 19 mm ± 1 mm; collar, 10 mm ± 1 mm; p < 0.01). One and 9 failures were encountered in MIS and collar groups, respectively (p = 0.012). Intubation time proved no statistical significance. Extension of craniocervical junction was observed in both groups, but occipitoatlantal joint was significantly more extended in collar group (median [range]: AWS, 10-degree angle [-1 to 20-degree angle]; collar, 14-degree angle [5 to 26-degree angle]; p < 0.01).

DISCUSSION

AWS laryngoscopy under cervical collar immobilization fails to meet our expectation. Intubation failed in 30% of the cases in collar group whereas only 3.3% of the cases in MIS group. Significant difference of mouth opening limitation is probably the major reason, as 7 of 9 failed cases in collar group had IID <10 mm. This was insufficient to insert the 18-mm blade of AWS. In addition, occipitoatlantal joint suffered a greater extension when wearing a neck collar. Differences in the method to stabilize the neck may be the reason.

CONCLUSION

When compared with cervical collar immobilization, AWS laryngoscopy along with MIS seems to be a safer and more definite method to secure airway of neck-injured trauma patients because it limits less mouth opening and upper cervical spine movement.

New device for pentax-airway scope in pediatric intubation

The PBLADE which is a component used with Pentax-Airway Scope (AWS) has only one size that is essentially for use in adults. It cannot be used in children and neonates. We have made a new device to fit the Pentax-AWS for use in children and neonates. This new device will provide a good indirect visualization for intubation in pediatric patients.

Airway scope versus macintosh laryngoscope in patients with simulated limitation of neck movements

BACKGROUND

Tracheal intubation in patients with suspected neck injuries should achieve two contradicting goals-sufficient laryngeal exposure and the least cervical spine movement. Because the former involves displacements of the cervical vertebrae, intubation under immobilization is widely performed today to prevent exacerbation of spinal code injuries. The unique curving blade of the Airway Scope (AWS) is designed to fit the oropharyngeal anatomy. A camera at the tip of the blade displays the view of the larynx, but unlike the direct laryngoscope, it needs no line-of-sight of the oral, pharyngeal, and tracheal axis. Our purpose is to determine whether AWS could be a suitable airway device for the intubation of patients with potential neck injury.

METHODS

Thirty-six patients scheduled for surgery were randomly assigned to undergo intubation using either AWS or Macintosh laryngoscope (MLS). After general anesthetic induction, the patient's head was set in a neutral position, and an appropriately sized semi-rigid neck collar was placed. Measurements include intubation time, number of attempts, success rate, Cormack-Lehane classification, airway optimization maneuver, Intubation Difficulty Scale scores, and complications.

RESULTS

Intubation time proved no statistical significance (mean ± SD, AWS, 62.9 seconds ± 26.0 seconds, MLS, 55.6 seconds ± 26.0 seconds; p = 0.42). AWS scored less in Cormack-Lehane classification (median [range], AWS I [I-I], MLS IIIa [I-IIIb]; p < 0.0001), required fewer additional airway optimization maneuvers (p = 0.0003), and scored less in Intubation Difficulty Scale scores (AWS 0 [0-1], MLS 2 [0-5]; p < 0.0001).

CONCLUSIONS

In neck-immobilized patients using semi-rigid cervical collars, AWS improves laryngeal exposure and facilitates tracheal intubation. AWS may be a suitable intubation device for trauma patients.

Comparison of Flexiblade and Macintosh laryngoscopes: cervical extension angles during orotracheal intubation

SUMMARY

The Flexiblade(TM) is a new laryngoscope with a flexible blade, a handle and a lever, allowing gradual flexion over the distal half of the blade. In this study, we aimed to compare cervical vertebral movements during tracheal intubation with the Flexiblade and Macintosh laryngoscope in 32 patients undergoing elective surgery requiring general anaesthesia (n = 16 per group). Fluoroscopic images of cervical movement were captured before, during and after intubation and evaluated by a radiologist. C1-C2 cervical vertebral movement was significantly reduced during the intubation in the Flexiblade group (p < 0.0001). C2-C3 cervical movement was similar in both groups (p = 0.81). No significant differences were noted in success rates for intubation, oxygen saturation levels, haemodynamic variables or intubation-related injury. The decreased extension angle between C1-C2 during Flexiblade laryngoscopy compared with Macintosh laryngoscopy may be an advantage where neurological damage with cervical movement is a concern.

Tracheal intubation using Airway Scope in two patients with difficult airway during cardiopulmonary resuscitation

The Airway Scope AWS-S100 (AWS, Pentax, Tokyo), a rigid video laryngoscope with integrated tube guidance that has recently become commercially available, helped the authors to establish airways in two patients with in-hospital cardiopulmonary arrest, after failed attempts to intubate the patients using the Macintosh laryngoscope (that only commanded the Cormack-Lehane grade 4 glottic views), the laryngeal mask airway, and even surgical cricothyroidotomy for the second case. This showed the utility of the AWS in the management of difficult airway cases even in emergency settings.

Distortion of anterior airway anatomy during laryngoscopy with the GlideScope videolaryngoscope

PURPOSE

A non-line-of-sight view is expected to cause less movement of the anterior airway anatomy and cervical spine during laryngeal visualization. Reduced distortion of anterior airway anatomy during laryngoscopy with the GlideScope videolaryngoscope (GVL), compared with the Macintosh laryngoscope, could explain the relatively easier nasotracheal intubation with the GVL. The purpose of this radiographic study was to compare the degree of anterior airway distortion and cervical spine movement during laryngoscopy with the GVL and the conventional Macintosh laryngoscope.

METHODS

Twenty patients requiring general anesthesia and tracheal intubation were studied. Each patient underwent laryngoscopy using the first-generation GVL and a direct laryngoscope with a Macintosh blade. During each laryngoscopy, a radiograph was taken when the best view of the larynx was obtained. Independent radiologists with subspeciality training in musculoskeletal imaging evaluated anterior airway distortion and cervical spine movement.

RESULTS

The distance between the epiglottis and the posterior pharyngeal wall during the GlideScope procedure was 21% less than that during the Macintosh laryngoscopy (P < 0.05). Anterior deviations of the vertebral bodies from baseline were 27, 32, 36, and 39% less at the atlas, C2, C3, and C4 vertebrae, respectively, during the GlideScope procedure than those measured during Macintosh laryngoscopy (P < 0.01). Cervical extension between the occiput and C4 during the GlideScope procedure was 23% less than that during Macintosh laryngoscopy (P < 0.05).

CONCLUSION

Both anterior airway distortion and cervical spine movement during laryngeal visualization were less with the GVL than with the Macintosh laryngoscope.

Comparison of the Airway Scope and Macintosh laryngoscope with in-line cervical stabilization by the semisolid neck collar: manikin study

BACKGROUND

The usefulness of Airway Scope (AWS) and Macintosh direct laryngoscope (ML) for patients with trauma requiring intubation with in-line cervical stabilization for protection of the cervical spine was compared.

METHODS

Thirty-three residents performed orotracheal intubation using ML and AWS in an intubation model with in-line cervical stabilization. The tracheal intubation success rate, time required for tracheal intubation, and number of trials of inserting the tracheal tube into the trachea were measured in individual residents.

RESULTS

Two residents inserted the tube into the esophagus using ML (success rate: 93.9%), but all residents succeeded in tracheal intubation using AWS (success rate: 100%) (p = 0.492). The time required for intubation was similar using AWS and ML (15 seconds vs. 20 seconds, p = 0.261). The number of trials using AWS was significantly lower (2.0 times vs. 1.0 times, p = 0.001).

CONCLUSION

The usefulness of AWS may be comparable with or greater than that of ML for oral intubation in trauma patients with in-line cervical stabilization.

Pentax-AWS videolaryngoscope for awake nasal intubation in patients with unstable necks

In patients with unstable necks and at risk of pulmonary aspiration, awake fibreoptic intubation is often appropriate. However, stabilization of the neck can make fibreoptic intubation more difficult. I report the use of awake nasal intubation using the Pentax-Aiway Scope (AWS) in three patients with restricted neck movement, in whom awake fibreoptic intubation had failed. Case 1: a 59-yr-old man, at risk of aspiration, required an emergency cervical laminectomy. Awake fibreoptic intubation was attempted while a Halo vest was being applied, but it was impossible to see the glottis, mainly due to pharyngeal and laryngeal oedema. The Pentax-AWS was easily inserted orally, and nasotracheal intubation was achieved within 20 s. Case 2: an 85-yr-old woman with neck injury required emergency surgical stabilization. A retropharyngeal haematoma prevented a fibreoptic bronchoscope from being advanced beyond the epiglottis. Nasotracheal intubation using the Pentax-AWS (with the aid of a gum elastic bougie) was achieved within 1 min. Case 3: a 22-yr-old man, with partial spinal cord damage, was undergoing cervical laminoplasty. He was at risk of aspiration and had an oedematous larynx. Although it was possible to insert a fibreoptic bronchoscope into the trachea while the neck was stabilized with a Halo vest, it was impossible to advance a tube over the fibrescope. Awake nasotracheal intubation using the Pentax-AWS was achieved within 15 s. The Pentax-AWS may be useful for nasotracheal intubation in awake patients with restricted necks.

Video and optic laryngoscopy assisted tracheal intubation--the new era

With advances in technology, videoscopy and optic intubation have been gaining popularity particularly in patients with difficult airways or as rescue devices in failed intubation attempts. Their routine use is, however an uncommon occurrence. This review paper will summarise some of those newly developed devices currently available to assist tracheal intubation, their advantages, disadvantages when compared with the conventional laryngoscope and finally, evidence to support their use in both elective and emergency airway management.

Pentax-AWS, a new videolaryngoscope, is more effective than the Macintosh laryngoscope for tracheal intubation in patients with restricted neck movements: a randomized comparative study

BACKGROUND

We studied whether laryngoscopy and tracheal intubation were easier when using the Pentax-AWS (Tokyo, Japan), a new videolaryngoscope, than when applying the Macintosh laryngoscope, during manual in-line neck stabilization.

METHODS

In 203 anaesthetized patients with manual in-line neck stabilization, we inserted the Pentax-AWS and a Macintosh laryngoscope, in turn, and recorded the view of the glottis and time taken to laryngoscopy. The success rate of tracheal intubation (within 120 s) and time to intubation were also recorded.

RESULTS

The view of the glottis was significantly better with the Pentax-AWS than with the Macintosh laryngoscope (P<0.001). For the Macintosh laryngoscope, the view was obscured in 22 of 203 patients (11%) (Grade 3 in 21 patients and Grade 4 in one patient), whereas for the Pentax-AWS, the glottis was always clearly seen (Grade 1). Time taken to see the glottis with the Pentax-AWS [mean (sd): 6.0 (3.1) s] was significantly shorter than with the Macintosh laryngoscope [11.0 (5.0) s] (95% CI for difference: 4-6 s). The success rate of tracheal intubation with the Pentax-AWS (all of 99 patients) was significantly higher than with the Macintosh laryngoscope (93 of 104 patients) (P=0.001). Time taken for intubation was similar between the Macintosh laryngoscope [51 (27) s] and the Pentax-AWS [54 (14) s] (95% CI for difference: -9 to 3 s).

CONCLUSIONS

In patients with stabilized neck, the Pentax-AWS provided a better view of the glottis and a higher success rate of tracheal intubation, compared with the conventional Macintosh laryngoscope.