["Dual Guidance"? - parallel combination of ultrasound-guidance and nerve stimulation - Contra]. / "Dual Guidance"? - kombinierte Anwendung von Ultraschall und Nervenstimulator - Contra.

Sonography is a highly user-dependent technology. It presupposes a considerable degree of sonoanatomic and sonographic knowledge and requires good practical skills of the examiner. Sonography allows the identification of the puncture target, observes the needle feed and assesses the spread pattern of the local anesthetic in real time. Peripheral electrical nerve stimulation (PNS) cannot offer these advantages to the same degree, but may allow nerve localization under difficult sonographic conditions. The combination of the two locating techniques is complex in its practical implementation. Partially, the use of one location technique is made even more difficult by the combination with the second. PNS in parallel to sonography serves primarily as a warning technology in the case of an invisible cannula tip. It should not be construed as a compensation technique for the lack of sonographic skills or knowledge. However, PNS may be helpful in the sense of a bridging technology as long as the user is aware of its limitations.

Morphological macrovascular alterations in complex regional pain syndrome type I demonstrated by increased intima-media thickness.

BACKGROUND: Although intima-media thickness (IMT) was increased in several inflammatory diseases, studies investigating whether the inflammatory processes lead to macrovascular alteration with increased IMT in complex regional pain syndrome (CRPS) lack. METHODS: Using ultrasound (high-resolution B-mode), we compared bilaterally the IMT of the common carotid artery (CCA-IMT), the radial artery (RA-IMT), the brachial artery (BRA-IMT) and the quotient QRA/CCA, in CRPS type I (n=17), peripheral nerve injury (PNI, n=17) and pain-free controls (PFC, n=22, matched to CRPS by gender, age and traditional cardiovascular risk factors). STATISTICS: Spearman's correlation, paired t-test, ANOVA (p<0.05). RESULTS: Compared to PFC, RA-IMT were significantly increased in both patient groups bilaterally (mean±standard deviation, CRPS affected side vs. PFC dominant side: 0.32±0.08 mm vs. 0.19±0.08 mm, p<0.001; PNI affected side vs. PFC dominant side: 0.27±0.09 mm vs. 0.19±0.08 mm, p< 0.05; CRPS non-affected side vs. PFC non-dominant side: 0.30±0.10 mm vs. 0.19±0.09 mm, p<0.001; PNI non-affected side vs. PFC non-dominant side: 0.25±0.10 mm vs. 0.19±0.09 mm, p<0.05) and QRA/CCA (CRPS affected-side vs. PFC dominant side: 0.49±0.12 vs. 0.30±0.11, p<0.001; PNI affected side vs. PFC dominant side: 0.41±0.10 vs. 0.30±0.11, p<0.05; CRPS non-affected side vs. PFC non-dominant side: 0.43±0.19 vs. 0.30±0.13, p<0.001; PNI non-affected side vs. PFC non-dominant side: 0.39±0.14 vs. 0.30±0.13, p<0.05), and BRA-IMT - only on the affected side in CRPS (CRPS: 0.42±0.06 mm vs. PFC: 0.35±0.08 mm; p<0.05). In CRPS, QRA/CCA was significantly higher on the affected side compared to PNI (p<0.05). However, only CRPS displayed within-group side-to-side differences with a significantly increased RA-IMT and QRA/CCA on the affected side (p<0.05). The CCA-IMT was comparable between all groups and sides. CONCLUSIONS: The increased IMT of peripheral arteries in CRPS suggests ongoing inflammatory process. Until now, only endothelial dysfunction has been reported. The presented morphological macrovascular alterations might explain the treatment resistance of some CRPS patients.

Relationship of the internal jugular vein to the common carotid artery: implications for ultrasound-guided vascular access.

BACKGROUND AND OBJECTIVE: For cannulation of the internal jugular vein (IJV), ultrasound increases the number of first pass successes and reduces the rate of mechanical complications. A frequent complication of IJV access is the accidental injury of the common carotid artery (CCA), which can be dangerous in some circumstances. Landmarks and palpation of the CCA are used when ultrasound is not available. These conventional methods are based on the lateral position of the IJV to the CCA, and physicians traditionally employ head rotation to increase the success rates of IJV cannulation. Ultrasound scanning strictly from the anterior to posterior is not possible for this process because the probe must be adequately coupled to compensate for the curvature of the neck. Scans have been performed from different angles lateral to the neck, but misleadingly depict the relationship of the IJV to the CCA. In this study, the authors examined the effect of scanning at a 45° angle at the level of the cricoid on the depiction of the IJV in relation to the CCA. Furthermore, the influence of 30° head rotation to the contralateral side was also investigated. METHOD: The relationship of the IJV to the CCA was recorded using ultrasound in 600 patients. Patients were placed in a supine position and the probe was coupled at the level of the cricoid, scanning at an angle of 45° from the lateral side of the neck. Based on the ultrasound images, the position of the IJV in relation to the CCA was recorded using a segmented grid. The centre of the vein (cross-section of the vertical and longitudinal diameter) determined the segment classification, in which the top of the ultrasound image was defined as the anterior. Additionally, in 300 patients, the head was rotated to the contralateral side at 30° to examine the impact of head rotation on the position of the IJV. RESULTS: The IJV was found in the lateral segment in only 3.0-3.3% of the patients. It was found in the anteromedial segment more frequently on the left side compared to the right side (P < 0.005). On the right side, the IJV was shown more frequently in the anterolateral position (P < 0.0001). Head rotation at 30° in 300 of the 600 patients caused a significant change of the IJV position in the left anteromedial segment, in that it frequently placed the IJV towards the anterior and anterolateral segment (P < 0.05). There was no significant impact of head rotation on the IJV representation on the right side. Atypical positions of the IJV (posterior, medial or thrombosis) were found in some cases. CONCLUSION: Ultrasound images used for IJV access usually depict the vein as being anterior to the CCA and only to a minor extent in the lateral position. This positioning is important for needle processing in order to avoid accidental arterial puncture and to identify atypical positions of the IJV. To determine the ideal puncture site, images of the neck vessels along their entire pathway should be obtained when using ultrasound for vascular access.

Ultrasound characteristics of needles for regional anesthesia.

BACKGROUND AND OBJECTIVES: Needle visibility is a crucial requirement for successful and safe ultrasound-guided peripheral nerve blocks. We performed a prospective study on the ultrasonic imaging quality of various commercially available needles. We tested the hypothesis that different nerve block needles would have different ultrasonic appearances. Furthermore, we examined the influence of needle angle with regard to the ultrasound plane, 2 types of media surrounding the needle, and the impact of 3 different ultrasound machines. METHODS: Twelve needles were prospectively tested for 3 ultrasound planes (longitudinal, axial tip, and axial shaft) at 2 different angles (0 degrees and 45 degrees). Quality of needle visibility and ultrasound scans were described by using 6 criteria (visibility score range 0-10): (1) visibility of needle; (2) visibility of surrounding media; (3) consistency of needle surface; (4) formation of artifacts; (5) degree of shadowing; and (6) detection and distinction of the needle from the surrounding media. Additionally, every ultrasound scan was performed in 2 media (water bath and animal model) with 3 ultrasound devices and evaluated by 2 investigators. Evaluation of the ultrasound scans was blinded with regard to needle but not to the ultrasound machine and media. RESULTS: In the animal model, visibility was good at 0 degrees (visibility score greater than 6) but was decreased for all needles at a 45 degree angle (criterion 6). In this setting, 2 needles were difficult to identify (score less than 3; criterion 6) and only 3 of 12 reached a score of 7 or more (criterion 6). Depiction quality for all 3 planes was significantly lower in the animal model when compared with the water bath (P < .001) and at an angle of 45 degrees when compared with 0 degrees (P < .001). There was no significant impact of the ultrasound machine on image quality. CONCLUSIONS: In a tissue-equivalent model we found significant differences among different types of needles at a 45 degree angle. In clinical use, angles between 30 degrees and 60 degrees are required. Because visibility of the needle is a keystone of ultrasound-guided peripheral nerve blocks, our results suggest the need to optimize the echogenicity of needles used for ultrasound-guided nerve blocks.

Ultrasound imaging in vascular access.

Physicians spend a considerable amount of time and effort inserting catheters and needles into patients. Central venous catheters are the mainstay of measuring hemodynamic variables that cannot be assessed by noninvasive procedures. These catheters also allow hemodialysis, parenteral nutritional support, delivery of medications, and catecholamine administration. Arterial pressure catheters are frequently used for hemodynamic monitoring and for obtaining arterial blood gases in critically ill patients. Such use of arterial and central venous catheters, however, is potentially associated with severe complications that can be injurious to patients and expensive to treat. Techniques involving the use of anatomic landmarks have been the traditional mainstay of accessing the central venous system for decades. With the development and refinement of portable and affordable high-resolution ultrasound devices, imaging vascular access has changed the role of the traditional landmark techniques. In this article, we explain the use of ultrasound for vascular access to reduce complications associated with cannulation of veins and arteries. We will also provide a brief overview of the current literature regarding ultrasound-guided vascular access.