Search

Background: Posterior variants of abdominal wall block include the quadratus lumborum type I, quadratus lumborum type II and quadratus lumborum transmuscular blocks. Our objectives were to compare the spread of injectate and nerve involvement, after conducting blocks using ultrasound guidance in soft embalmed cadavers.Methods: After randomization, an experienced anaesthetist conducted three quadratus lumborum 1, three quadratus lumborum 2 and four transmuscular blocks on the left or right sides of five cadavers. All cadavers were placed in the lateral position and the quadratus lumborum muscle seen using a 3-9 MHz ultrasound probe placed in the flank. For each block, a 20 ml mixture of 17.75 ml water, 2 mls latex and 0.25 ml India ink was injected. The lumbar region and abdominal flank were dissected 72 h later.Results: We conducted 10 blocks. Two quadratus lumborum 1 and two quadratus lumborum 2 blocks were associated with spread of dye within the TAP plane. One quadratus lumborum 1 block spread to the deep muscles of the back and one quadratus lumborum 2 block dispersed within the subcutaneous tissue surrounding the abdominal flank. All transmuscular quadratus lumborum blocks spread consistently to L1 and L3 nerve roots and within psoas major and quadratus lumborum muscles.Conclusions: Consistent spread to lumbar nerve roots was achieved using the transmuscular approach through the quadratus lumborum. [ABSTRACT FROM AUTHOR]

Background: Few data describe the pharmacological interactions between local anaesthetics and opioids. The aim of this study was to measure the median effective concentration (MEC) of diamorphine and levobupivacaine when given separately and as mixtures for epidural analgesia, and determine whether the combination is additive or synergistic.Methods: One hundred and twenty patients were enrolled in this prospective randomized, two-phase, double-blind study. In the first phase, 60 women were randomized to receive a fixed 20 ml volume of either levobupivacaine or diamorphine epidurally . Dosing was determined using up-down sequential allocation with testing intervals, respectively, of 0.01%w/v and 12.5 microg ml(-1). After estimations of the MEC of levobupivacaine and diamorphine, a further 60 patients were randomized in the second phase to one of the three mixtures: (a) diamorphine 70 microg ml(-1) (fixed) and levobupivacaine (testing interval 0.004%w/v, starting at 0.044%w/v); (b) levobupivacaine 0.044%w/v (fixed) and diamorphine (testing interval 7 microg ml(-1), starting at 70 microg ml(-1)); and (c) bivariate diamorphine and levobupivacaine (testing intervals of 7 microg ml(-1) and 0.004%w/v starting at 70 microg ml(-1) and 0.044% w/v respectively).Results: The MEC estimates from the first phase were 143.8 microg ml(-1) (95% CI 122.2-165.3) for diamorphine and 0.083%w/v (95% CI 0.071-0.095) for levobupivacaine. In the second phase, the MEC and interaction index (gamma) of the three combinations were: diamorphine 65.5 microg ml(-1) (56.8-74.2), gamma = 0.99; levobupivacaine 0.041%w/v (0.037-0.049), gamma = 0.98; and for the fixed combination diamorphine 69.5 microg ml(-1) (60.5-78.5) and levobupivacaine 0.044%w/v (0.039-0.049), gamma = 1.02.Conclusion: The combination of diamorphine and levobupivacaine is additive and not synergistic when used for epidural analgesia in the first stage of labour. [ABSTRACT FROM AUTHOR]

Background: Errors may occur during regional anaesthesia whilst searching for nerves, needle tips, and test doses. Poor visual search impacts on decision making, clinical intervention, and patient safety.Methods: We conducted a randomised single-blind study in a single university hospital. Twenty trainees and two consultants examined the paired B-mode and fused B-mode and elastography video recordings of 24 interscalene and 24 femoral blocks conducted on two soft embalmed cadavers. Perineural injection was randomised equally to 0.25, 0.5, and 1.0 ml volumes. Tissue displacement perceived on both imaging modalities was defined as 'target' or 'distractor'. Our primary objective was to test the anaesthetists' perception of the number and proportion of targets and distractors on B-mode and fused elastography videos collected during femoral and sciatic nerve block on soft embalmed cadavers. Our secondary objectives were to determine the differences between novices and experts, and between test-dose volumes, and to measure the area and brightness of spread and strain patterns.Results: All anaesthetists recognised perineural spread using 0.25 ml volumes. Distractor patterns were recognised in 133 (12%) of B-mode and in 403 (38%) of fused B-mode and elastography patterns; P<0.001. With elastography, novice recognition improved from 12 to 37% (P<0.001), and consultant recognition increased from 24 to 53%; P<0.001. Distractor recognition improved from 8 to 31% using 0.25 ml volumes (P<0.001), and from 15 to 45% using 1 ml volumes (P<0.001).Conclusions: Visual search improved with fusion elastography, increased volume, and consultants. A need exists to investigate image search strategies. [ABSTRACT FROM AUTHOR]

Background: The incidence of intraneural injection during trainee anaesthetist ultrasound guided nerve block varies between 16% in experts and up to 35% in trainees. We hypothesized that elastography, an ultrasound-based technology that presents colour images of tissue strain, had the potential to improve trainee diagnosis of intraneural injection during UGRA, when integrated with B-Mode ultrasound onto a single image.Methods: We recorded 40 median nerve blocks randomly allocated to 0.25 ml, 0.5 ml, 1 ml volumes to five sites, on both arms of two soft embalmed cadavers, using a dedicated B-Mode ultrasound and elastography transducer. We wrote software to fuse elastogram and B-Mode videos, then asked 20 trainee anaesthetists whether injection was intraneural or extraneural when seeing B-Mode videos, adjacent B-Mode and elastogram videos, fusion elastography videos or repeated B-Mode ultrasound videos.Results: Fusion elastography improved the diagnosis of intraneural injection compared with B-Mode ultrasound, Diagnostic Odds Ratio (DOR) (95%CI) 21.7 (14.5 - 33.3) vs DOR 7.4 (5.2 - 10.6), P < 0.001. Compared with extraneural injection, intraneural injection was identified on fusion elastography as a distinct, brighter translucent image, geometric ratio 0.33 (95%CI: 0.16 - 0.49) P < 0.001. Fusion elastography was associated with greater trainee diagnostic confidence, OR (95%CI) 1.89 (1.69 - 2.11), P < 0.001, and an improvement in reliability, Kappa 0.60 (0.55 - 0.66).Conclusions: Fusion elastography improved the accuracy, reliability and confidence of trainee anaesthetist diagnosis of intraneural injection. [ABSTRACT FROM AUTHOR]

Background: We evaluated the physical properties and functional alignment of the soft-embalmed Thiel cadaver as follows: by assessing tissue visibility; by measuring its acoustic, mechanical and elastic properties; by evaluating its durability in response to repeated injection; and by aligning images with humans.Methods: In four soft-embalmed Thiel cadavers, we conducted three independent studies. We assessed the following factors: (i) soft tissue visibility in a single cadaver for 28 weeks after embalming; (ii) the displacement of tissues in response to 1 and 5 ml interscalene and femoral nerve blocks in a single cadaver; and (iii) the stiffness of nerves and perineural tissue in two cadavers. We aligned our findings with ultrasound images from three patients and one volunteer. Durability was qualified by assessing B-mode images from repetitive injections during supervised training.Results: There was no difference in visibility of nerves between 2 and 28 weeks after embalming {geometric mean ratio 1.13 [95% confidence interval (CI): 0.75-1.68], P=1.0}. Mean tissue displacement was similar for cadaver femoral and interscalene blocks [geometric mean ratio 1.02 (95% CI: 0.59-1.78), P=0.86], and for 1 and 5 ml injection volumes [geometric mean ratio 0.84 (95% CI: 0.70-1.01), P=0.19]. Cadavers had higher intraneural than extraneural stiffness [Young's modulus; geometric mean ratio 3.05 (95% CI: 2.98-3.12), P<0.001] and minimal distortion of anatomy when conducting 934 left-sided interscalene blocks on the same cadaver throughout a 10 day period.Conclusions: The soft-embalmed Thiel cadaver is a highly durable simulator that has excellent physical and functional properties that allow repeated injection for intensive ultrasound-guided regional anaesthesia training. [ABSTRACT FROM AUTHOR]

Regional anaesthesia provides many benefits, but there remain serious transient or long-lasting clinical side-effects. Ultrasound-guided regional anaesthesia has improved block efficacy, but has not been universally accepted because anaesthetists have difficulty visualizing needles. Two echogenic needles from Braun (denoted BE) and Pajunk (PE), aiming to provide high reflection at steep and flat puncture angles, have been introduced. The primary aim of our study was to compare the visibility of these needles with a standard Braun needle (denoted BS) using the Thiel cadaver as our anatomical model. These retain full flexibility of the limbs, and have demonstrated high-quality ultrasound images, ready tracing of peripheral nerves and spread of solution, and recognizable intraneural injection. Neck rotation for interscalene block, external shoulder rotation for axillary block, and hip and knee flexion for sciatic block are all possible. We first conducted a pilot study of 48 i.m. needle injections inserted in-plane and out of plane at four angles (30°, 45°, 60°, and 75°), using an engineered block. The visibility of the needle was assessed by two independent observers with a five-point Likert scale. The pilot study showed a non-parametric distribution of data using the Shapiro-Wilk test. Median visibility scores were higher for the PE needle inserted at 758 out of plane and 308 in plane. With these data, we calculated an effect size of 0.47 for 'needle' and an effect size of 0.43 for 'angle', α=0.5, β=0.2, and using a randomized block ANOVA power analysis (PASS, UT, USA), we required a total of six blocks, that is, 72 injections in plane and out of plane. For the formal study, a total of 144 observations were made. Intraclass correlation between observers was 0.91. In plane, the median visibility scores were 1, 1, and 3 for the BS, BE, and PE needles, respectively, Friedman's Q 6.50, P=0.04. Post hoc tests showed a difference between BS and PE needles. Out of plane, the median visibility scores were 1, 1, and 3 for the BS, BE, and PE needles, respectively, Friedman's Q 7.50, P=0.02. Post hoc tests showed differences between the PE and both Braun needles. In conclusion the PE needle was found to be more visible than the BS needle in-plane, and more visible than both the BS and BE needles out of plane. [ABSTRACT FROM AUTHOR]

Shorter working hours and shift systems are limiting trainee clinical experience. Essential technical skills are being developed in environments other than the operating theatre. The ideal model for regional anaesthesia training should simulate the passive and dynamic components of nerve block such as nerve anatomy, needle movement, fascial penetration, perineural fluid injection, and inadvertent intraneural and intravascular injection. A new development in regional anaesthesia simulation is the Thiel embalmed cadaver, preserved using a novel technique which minimizes formaldehyde use, enables full flexibility of the limbs, and is compatible with ultrasound imaging, unlike cadavers preserved conventionally. As the University of Dundee is the first to introduce Thiel cadavers to the UK, an opportunity existed to evaluate the visibility of anatomical structures during cadaver regional anaesthesia. The interscalene axillary, femoral, and popliteal nerves were scanned at 2, 3, 5, 8, 11, and 14 weeks after embalming. Scanning of all nerves was performed with a 10-5 MHz linear probe using a self-optimization facility. Once the best image site was identified, 1 ml of Thiel moistening solution was injected around each nerve, and a 30 s video recording made. Visibility of nerves, muscle, fascia, blood vessels, and needle passage was ranked using a seven-point ordinal scale. Rater agreement was assessed using the intraclass correlation. In addition, nerve visibility was assessed with the Vienna score, an ordinal scale from 1 to 4, the spread of solution measured as the log area under the curve of spread using ultrasound elastography (log AUC), and Zone Speed Index (ZSI). Distribution of data used the Shapiro- Wilk test, parametric data were analysed by the t-test (SD), non-parametric with Mann-Whitney, and paired comparisons with the Wilcoxon signed-rank test. Correlation of data used Pearson's and Spearman's test as appropriate. Results are presented for the interscalene block. All blocks were performed on the left side of the body. Full rotation of the neck was possible. Mean (SD) distance from the skin was 1.2 (0.3) cm. With regard to ultrasound image quality, mean (SD) visibility score for scalenus anterior was 5 (0.9), scalenus medius 4.8 (1.2), sternocleidomastoid 5.3 (0.8), and nerve roots 5.2 (1.2). Median (IQR) Vienna score for nerve roots was 2.5 (2-3). With regard to nerve block, mean (SD) needle visibility was 2.8 (1.2), needle tip visibility 1.3 (0.5). There was a difference in median (IQR) visibility of spread for B-mode ultrasound 4.5 (3-5) and elastography 7 (6.25-7), P¼0.04. This pilot study of Thiel cadavers has shown good image quality of nerves, muscle, and vasculature over an initial 12 week period. Subjective visibility scores correlated well with elastography and Zone Speed Index. On the basis of these findings, the Thiel cadaver should be considered. [ABSTRACT FROM AUTHOR]

Despite the undoubted benefits of regional anaesthesia, there remain possible serious clinical side-effects which suggest the need for optimum methods of application of the anaesthetic. In ultrasound-guided regional anaesthesia, in particular, the need to visualize the tip of the needle and anaesthetic flood has been highlighted. A high-quality medical ultrasound imaging system is used (Zonare Inc., CA, USA) with an early implementation of sono-elastography to visualize the flow of anaesthetic agent. The anechogenic nature of the injection liquid means that it cannot be visualized by elastography, unlike surrounding tissue. Sono-elastography is thus able to enhance contrast between it and tissue. The outcome of this work has been evaluated in Thiel cadavers which have proved particularly suitable for ultrasound imaging and have been shown to be a valid model. The study was performed with interscalene, femoral, and median nerve-blocks on Thiel cadavers, each representing a typical clinical anaesthesia approach. Results have shown that it is possible to improve the hydrolocalization method by processing the echo-elastography data using MATLAB®. This involves the identification of a region of interest and adaptive filtering of the data map to increase the contrast of the liquid volume. An adaptive filtering algorithm for enhanced elastography is realized through the acquisition of a dynamic elastography noise profile which is subtracted from the regular elastography frame. Furthermore, an additional two-dimensional median filter is applied to reduce unwanted elastography image artifacts. The map of this restricted area can then be superimposed on the B-scan image highlighting and corresponding to the area of fluid (anaesthetic) spread (Fig. 7). The image processing is carried out in real time and displayed on a computer screen positioned adjacent to the ultrasound imaging system. This enables very sensitive verification of the needle tip position. The necessary confirmation volume can be reduced to 0.25 ml. This sensitivity also means that it is possible to see if the local anaesthetic spreads in the wrong direction and reposition the needle accordingly. [ABSTRACT FROM AUTHOR]