Variation in the accuracy of ultrasound for the detection of intubation by endotracheal tube size.

INTRODUCTION: Rapid and accurate confirmation of endotracheal tube (ETT) placement is a fundamental step in definitive airway management. Multiple techniques with different limitations have been reported. Recent studies have evaluated the accuracy, time to performance, and physician confidence for ultrasound in both cadaveric models and live patients. However, no study to date has measured the effect of ETT size. Our study is the first to measure the accuracy of ultrasound for ETT confirmation based on ETT size. METHODS: This study was performed in a cadaver lab using three different cadavers chosen to represent varying neck circumferences. Cadavers were intubated in a random sequence with respect to both the location of intubation (i.e., tracheal vs esophageal) and sizes of ETT. Three ETT sizes were utilized: 6.0-, 7.0-, and 8.0-mm. Blinded sonographers assessed the location of the ETT using the static technique. Accuracy of sonographer identification, time to identification, and operator confidence were assessed. RESULTS: 453 assessments were performed. Overall, ultrasound was 99.1% (95% CI 97.8% to 99.7%) accurate in identification of correct location of intubation. The mean time to placement was 6.45 s (95% CI 5.62 to 7.28). The mean operator confidence level was 4.72/5.0 (95% CI 4.65 to 4.78). There was no significant difference between ETT sizes with respect to any of the outcomes. CONCLUSION: The diagnostic accuracy of ultrasound for ETT confirmation did not vary with the use of different ETT sizes. Further studies are needed to determine if the accuracy would change with more novice providers or in specific patient populations.

Comparison of Static versus Dynamic Ultrasound for the Detection of Endotracheal Intubation.

INTRODUCTION: In the emergency department setting, it is essential to rapidly and accurately confirm correct endotracheal tube (ETT) placement. Ultrasound is an increasingly studied modality for identifying ETT location. However, there has been significant variation in techniques between studies, with some using the dynamic technique, while others use a static approach. This study compared the static and dynamic techniques to determine which was more accurate for ETT identification. METHODS: We performed this study in a cadaver lab using three different cadavers to represent variations in neck circumference. Cadavers were randomized to either tracheal or esophageal intubation in equal proportions. Blinded sonographers then assessed the location of the ETT using either static or dynamic sonography. We assessed accuracy of sonographer identification of ETT location, time to identification, and operator confidence. RESULTS: A total of 120 intubations were performed: 62 tracheal intubations and 58 esophageal intubations. The static technique was 93.6% (95% confidence interval [CI] [84.3% to 98.2%]) sensitive and 98.3% specific (95% CI [90.8% to 99.9%]). The dynamic technique was 92.1% (95% CI [82.4% to 97.4%]) sensitive and 91.2% specific (95% CI [80.7% to 97.1%]). The mean time to identification was 6.72 seconds (95% CI [5.53 to 7.9] seconds) in the static technique and 6.4 seconds (95% CI [5.65 to 7.16] seconds) in the dynamic technique. Operator confidence was 4.9/5.0 (95% CI [4.83 to 4.97]) in the static technique and 4.86/5.0 (95% CI [4.78 to 4.94]) in the dynamic technique. There was no statistically significant difference between groups for any of the outcomes. CONCLUSION: This study demonstrated that both the static and dynamic sonography approaches were rapid and accurate for confirming ETT location with no statistically significant difference between modalities. Further studies are recommended to compare these techniques in ED patients and with more novice sonographers.

Comparison of color flow with standard ultrasound for the detection of endotracheal intubation.

INTRODUCTION: Intubation is a frequently performed procedure in emergency medicine that is associated with significant morbidity and mortality when unrecognized esophageal intubation occurs. However, it may be difficult to visualize the endotracheal tube (ETT) in some patients. This study assessed whether the addition of color Doppler was able to improve the ability to visualize the ETT location. METHODS: This study was performed in a cadaver lab using three different cadavers chosen to represent varying neck circumference. Cadavers were randomized to tracheal or esophageal intubation. Blinded sonographers then assessed the location of the ETT using either grayscale or color Doppler imaging. Accuracy of sonographer identification of ETT location, time to identification, and operator confidence were assessed. RESULTS: One hundred and fifty intubations were performed and each was assessed by both standard and color Doppler techniques. There were 78 tracheal intubations and 72 esophageal intubations. The standard technique was 99.3% (95% CI 96.3 to 99.9%) accurate. The color flow technique was also 99.3% (95% CI 96.3 to 99.9%) accurate. The mean operator time to identification was 3.24s (95% CI 2.97 to 3.51s) in the standard approach and 5.75s (95% CI 5.16 to 6.33s) in the color flow technique. The mean operator confidence was 4.99/5.00 (95% CI 4.98 to 5.00) in the standard approach and 4.94/5.00 (95% CI 4.90 to 4.98) in the color flow technique. CONCLUSION: When added to standard ultrasound imaging, color flow did not improve accuracy or operator confidence for identifying ETT location and resulted in a longer examination time.

What Protects Certain Nerves from Stretch Injury?

The human tibial nerves is less prone to injury following joint arthroplasty compared with the peroneal nerves. Besides the anatomical distribution, other features may confer protection from stretch injury. We therefore examined the size, shape and connective tissue distribution for the two nerves. The tibial and peroneal nerves from each side of nine fresh human cadavers we reharvested mid-thigh. Proximal segments manually stretched 20%-25% were fixed in aldehyde, while the adjacent distal segments were fixed in their natural length. Paraffin sections stained by Masson's trichrome method for connective tissue were examined by light microscopy. Tibial nerves had 2X more fascicles compared with the peroneal, but the axonal content appeared similar. Analysis showed that neither nerve had a significant reduction in cross sectional area of the fascicles following stretch. However, fascicles from stretched tibial nerves become significantly more oval compared with those from unstretched controls and peroneal nerves. Tibial nerves had a greater proportion that was extrafascicular tissue (50-55%) compared with peroneal nerves (38%-42%). This epineurium was typically adipose tissue. Perineurial thickness in both nerves was directly related to fascicular size. Tibial nerves have several unique histological features associated with size, shape and tissue composition compared with the peroneal nerve. We suggest that more fascicles with their tightly bound perineurium and more robust epineurium afford protection against stretch injury. Mechanical studies should clarify how size and shape contribute to nerve protection and/or neurapraxia.

Frameless neuronavigation based only on 3D digital subtraction angiography using surface-based facial registration.

OBJECT: Cerebrovascular lesions can have complicated abnormal anatomy that is not completely characterized by CT or MR angiography. Although 3D rotational angiography provides superior spatial and temporal resolution, catheter angiograms are not easily registered to the patient, limiting the use of these images as a source for neuronavigation. However, 3D digital subtraction angiography (DSA) contains not only vascular anatomy but also facial surface anatomy data. The authors report a novel technique to register 3D DSA images by using only the surface anatomy contained within the data set without having to fuse the DSA image set to other imaging modalities or use fiducial markers. METHODS: A cadaver model was first created to assess the accuracy of neuronavigation based on 3D DSA images registered by facial surface anatomy. A 3D DSA scan was obtained of a formalin-fixed cadaver head, with acquisitions of mask and contrast runs. The right common carotid artery was injected prior to the contrast run with a 45% contrast solution diluted with water-soluble red liquid latex. One week later, the head was registered to a neuronavigation system loaded with the 3D DSA images acquired earlier using facial surface anatomy. A right pterional craniotomy was performed and 10 different vascular landmarks were identified and measured for accuracy using the neuronavigation system. Neuronavigation based only on 3D DSA was then used to guide an open clipping procedure for a patient who presented with a ruptured distal lenticulostriate aneurysm. RESULTS: The accuracy of the measurements for the cadaver model was 0.71 ± 0.25 mm (mean ± SE), which is superior to the 1.8-5 mm reported for neuronavigation. The 3D DSA-based navigation-assisted surgery for the distal lenticulostriate aneurysm aided in localization, resulting in a small craniotomy and minimal brain dissection. CONCLUSIONS: This is the first example of frameless neuronavigation based on 3D catheter angiography registered by only the surface anatomy data contained within the 3D DSA image set. This is an easily applied technique that is beneficial for accurately locating vascular pathological entities and reducing the dissection burden of vascular lesions.

Trans-sphenoidal Approach to the Supraclinoid Internal Carotid Artery for Endovascular Access in a Cadaver.

PURPOSE: Sometimes, intracranial pathology in the distal vasculature cannot be accessed by standard endovascular techniques because of occlusion or insurmountable tortuosity of theinternal carotid artery (ICA). A trans-sphenoidal surgical approach can follow a similar trajectory to the course of the supraclinoid ICA. This study evaluates the feasibility of a trans-sphenoidal approach to the supraclinoid ICA for endovascular access. MATERIALS AND METHODS: In a fresh cadaver head, the sphenoid sinus was dissected through a trans-sphenoidal route. Bone over the carotid prominence was removed to expose the ICA. The artery was catheterized using the Seldinger technique, and three-dimensional digital subtraction angiography was performed to evaluate the procedure. RESULTS: The catheter was successfully inserted into the supraclinoid ICA via the trans-sphenoidal route. Three-dimensional radiographic reconstruction confirmed placement of the catheter and the trajectory of the sheath into the supraclinoid ICA. CONCLUSION: While the trans-sphenoidal route has innumerable disadvantages over the standard endovascular access techniques, this route could be considered when other treatment options are too risky or impractical.

Microsurgical anatomy of the transsylvian translimen insula approach to the mediobasal temporal lobe: Technical considerations and case illustration.

BACKGROUND: Various vascular, neoplastic, and epileptogenic pathologies occur in the mediobasal temporal region. A transsylvian translimen insula (TTI) approach can be used as an alternative to temporal transcortical approach to the mediobasal temporal region. The aim of this study was to demonstrate the surgical anatomy of the TTI approach, including the gyral, sulcal, and vascular anatomy in and around the limen insula. The use of this approach is illustrated in the resection of a complex arteriovenous malformation. METHODS: The TTI approach to the mediobasal temporal region was performed on three silicone-injected cadaveric heads. The gyral, sulcal, and arterial anatomy of the limen insula was studied in six formalin-fixed injected hemispheres. RESULTS: The TTI approach provided access to the anterior and middle segments of the mediobasal temporal lobe region as well as allowing access to temporal horn of the lateral ventricle. Using this approach we were able to successfully resect an arteriovenous malformation of the dominant medial temporal lobe. CONCLUSION: The TTI approach provides a viable surgical route to the region of mediobasal temporal lobe region. This approach offers an advantage over the temporal transcortical route in that there is less risk of damage to optic radiations and speech area in the dominant hemisphere.