Nerve localization for peripheral regional anesthesia: Recommendations of the German Society of Anaesthesiology and Intensive Care Medicine

[Peripheral Regional Anesthesia Techniques - Standards in Flux?!]

This review article provides an overview of current developments in peripheral regional anaesthesia (RA). The authors present a subjective compilation based on discussions at professional events and inquiries to the Working Group on Regional Anaesthesia of the German Society for Anaesthesiology and Intensive Care Medicine (DGAI). The article addresses several relevant topics, including the handling of antithrombotic medication in peripheral blockades with reference to European guidelines, the debate on the discharge timing after plexus anaesthesia, and the consideration of rebound pain as an independent pain entity following RA.Furthermore, the contentious discussion regarding the administration of peripheral nerve blockades under general anaesthesia is illuminated. The authors express no fundamental concerns in this regard but emphasize the importance of preoperative evaluation and individual patient needs. The question of mixing local anaesthetics is also addressed, with the authors critically questioning this tradition and recommending the use of individual, long-acting substances.Another focal point is the application of peripheral nerve blockades in emergency medicine, both in preclinical and emergency room settings. The authors highlight the necessity for high-quality studies and discuss the complex organizational issues associated with the preclinical application of RA techniques.

European Society of Anaesthesiology and Intensive Care Guidelines on peri-operative use of ultrasound for regional anaesthesia (PERSEUS regional anesthesia): Peripheral nerves blocks and neuraxial anaesthesia

Nowadays, ultrasound-guidance is commonly used in regional anaesthesia (USGRA) and to locate the spinal anatomy in neuraxial analgesia. The aim of this second guideline on the PERi-operative uSE of UltraSound (PERSEUS-RA) is to provide evidence as to which areas of regional anaesthesia the use of ultrasound guidance should be considered a gold standard or beneficial to the patient. The PERSEUS Taskforce members were asked to define relevant outcomes and rank the relative importance of outcomes following the GRADE process. Whenever the literature was not able to provide enough evidence, we decided to use the RAND method with a modified Delphi process. Whenever compared with alternative techniques, the use of USGRA is considered well tolerated and effective for some nerve blocks but there are certain areas, such as truncal blocks, where a lack of robust data precludes useful comparison. The new frontiers for further research are represented by the application of USG during epidural analgesia or spinal anaesthesia as, in these cases, the evidence for the value of the use of ultrasound is limited to the preprocedure identification of the anatomy, providing the operator with a better idea of the depth and angle of the epidural or spinal space. USGRA can be considered an essential part of the curriculum of the anaesthesiologist with a defined training and certification path. Our recommendations will require considerable changes to some training programmes, and it will be necessary for these to be phased in before compliance becomes mandatory.

A Swiss nationwide survey shows that dual guidance is the preferred approach for peripheral nerve blocks

Ultrasound has significantly increased safety and effectiveness in regional anesthesia. However, little is known about its clinical use. We studied clinical approaches currently used by anesthesiologists, conducted a nationwide survey, and analyzed data collected in ordered logistic regression models. All active members of the Swiss Society for Anaesthesiology and Resuscitation (SSAR/SGAR) were asked to participate. Reported practice in nerve localization, safety, and techniques used for peripheral nerve blocks (PNB) were main outcome measures. Experience ranged from 3 to >30 years. The mean number of block techniques mastered was 11.5 ± 5.9. Standard monitoring was regularly used, whereas sterile coats were less frequently used by anesthesiologists who self-estimated a higher level of expertise in PNB (ordered logit coefficient −0.05, 95% CI −0.07 to −0.02, P < 0.001; pseudo r2 = 0.019; probability > Chi2 = 0.02). The more self-estimated expertise anesthesiologists had, the less likely they were to use nerve stimulation in combination with ultrasound (dual guidance) (ordered logit coefficient −0.31; 95% CI −0.85 to −0.03: P = 0.03; pseudo r2 = 0.007; probability > Chi2 = 0.05). The high share of reported standard monitoring meets the recommendations of the Helsinki Patient Safety Declaration. Dual guidance appears to be the preferred approach for safely localizing nerves for PNB in Switzerland.

Subparaneural Injection in Popliteal Sciatic Nerve Blocks Evaluated by MRI

Intraneural injection of a local anesthetic can damage the nerve, yet it occurs frequently during distal sciatic block with no neurological sequelae. This has led to a controversy about the optimal needle tip placement that results from the particular anatomy of the sciatic nerve with its paraneural sheath.

The study population included patients undergoing lower extremity surgery under popliteal sciatic nerve block. Ultrasound-guidance was used to position the needle tip subparaneurally and to monitor the injection of the local anesthetic. Sonography and magnetic resonance imaging were used to assess the extent of the subparaneural injection.

Twenty-two patients participated. The median sciatic cross-sectional area increased from 57.8 mm2 pre-block to 110.8 mm² immediately post-block. An intraneural injection according to the current definition was seen in 21 patients. Two patients had sonographic evidence of an intrafascicular injection, which was confirmed by MRI in one patient (the other patient refused further examinations). No patient reported any neurological symptoms.

A subparaneural injection in the popliteal segment of the distal sciatic nerve is actually rarely intraneural, i.e. intrafascicular. This may explain the discrepancy between the conventional sonographic evidence of an intraneural injection and the lack of neurological sequelae.

Risk evaluation for needle-nerve contact related to electrical nerve stimulation in a porcine model

BACKGROUND

For performing peripheral nerve blocks, the risk for needle-nerve contact (NNC) as an adverse event for low and high current thresholds has not yet been clearly defined when nerve stimulator guided techniques were applied. This experimental study aimed to investigate the risk of NNCs when applying stimulation currents between 0.1 and 2 mA (in increments of 0.1 mA).

METHODS

Brachial plexus nerves were exposed surgically in five anesthetized pigs. An insulated needle connected to a nerve stimulator was placed at 10 mm distance to the targeted nerves. Current intensity was adjusted according to randomization (0.1-2.0 mA, increments of 0.1 mA). The needle tip was advanced toward the nerve until a motor response was elicited. The frequencies of NNCs for each of the adjusted current intensities were noted. Risks of NNCs were calculated according to the analysis of 95% confidence intervals (95% CI).

RESULTS

We executed 2000 needle placements with stimulation currents ranging from 0.1 to 2.0 mA. The risks for NNC at low current intensities were 0.85 (95% CI, 0.77-0.91) for 0.3 mA and 0.5 (95% CI, 0.4-0.6) for 0.5 mA, respectively. For high current intensities, risks of 0.13 (95% CI, 0.07-0.21) for 0.9 mA and 0.01 (95% CI, 0-0.05) for 1.1 mA were calculated.

CONCLUSIONS

In this experimental animal study, a relevant reduction in the risk of NNCs could be observed when high current intensities (0.9-1.1 mA) were applied compared to low current intensities (0.3-0.5 mA).

Histological confirmation of needle tip position during ultrasound-guided interscalene block: a randomized comparison between the intraplexus and the periplexus approach

PURPOSE

Ultrasound-guided interscalene block can be performed using either periplexus or intraplexus needle placement. In this novel study, we histologically examined the needle tip position in relation to the neural tissues with the two techniques. Our objective was to investigate the variable risk of subepineurial needle tip placement resulting from the two ultrasound-guided techniques.

METHODS

In an embalmed cadaveric model, periplexus or intraplexus interscalene injections were performed with the side, order, and technique assigned randomly. Under real-time ultrasound guidance, the block needle was placed next to the hyperechoic layer of the plexus (periplexus) or between the hypoechoic nerve roots (intraplexus). Once positioned, 0.1 mL of black acrylic ink was injected. The brachial plexus tissues were then removed and histology sections were prepared and then coded in order to blind two reviewers to group allocation. The area of ink staining was used to determine needle tip location, and the groups were compared for the presence of subepineurial ink.

RESULTS

Twenty-six cadavers had each of the blocks performed on either brachial plexus (i.e., 52 injections). No subepineurial ink deposits were observed in the periplexus group (0%), but subepineurial ink deposition was observed in 3/26 (11.5%) intraplexus injections (odds ratio, 0; 95% confidence interval, 0 to 2.362; P = 0.235). Furthermore, in the intraplexus group, two (of the three) subepineurial ink deposits were observed under the perineurium.

CONCLUSION

Although our study was somewhat underpowered due to a lower than previously reported rate of subepineurial needle tip positioning, our results suggest that there may be an increased likelihood of subepineurial needle tip position with the intraplexus approach. The periplexus technique resulted in no subepineurial spread of ink, suggesting that this approach may be less likely to result in mechanical trauma to nerves from direct needle injury.

Separation of stimulating catheters for continuous peripheral regional anesthesia during their removal - two case reports and a critical appraisal of the use of steel-coil containing stimulating catheters

Purpose

Stimulating catheters are widely used for continuous peripheral nerve block techniques in regional anesthesia. The incidence of reported complications is somewhat similar to that for non-stimulating catheters. However, as many stimulating catheters contain a coiled steel wire for optimal stimulation, they may cause specific complications.

Clinical features

In this report, we present two cases of complicated removals of stimulating catheters. During both removals, a part of the metal wire was left “decoiled” next to the supraclavicular and interscalene plexus, respectively. The strategies used to determine steel wire localization and a description of the successful removal of these steel wires are included in this report.

Conclusion

Catheter separation and problems with residual metal wire components of stimulating catheters seem to be a rare but specific problem during removal. Anesthesiologists should strictly avoid catheter shearing during insertion, adhere to the manufacturer’s instructions, and take care during catheter removal. Manufacturers should focus on technical solutions to avoid rare but relevant complications such as catheter tip decoiling and separation of stimulating catheters during removal.