[Stocktaking of local anesthetics 2020]. / Bestandsaufnahme der Lokalanästhetika 2020.

For decades local anesthetics have proven to be safe and effective drugs in the clinical practice, crucially promoting the enormous achievements in regional anesthesia. Meanwhile, it is a well-known fact that local anesthetics are much more than just "simple" sodium channel blockers. They also interact with numerous other ion channels and subcellular structures, enhancing nerve blockade and resulting in systemic "alternative" effects, which can sometimes even be clinically used. By the simultaneous administration of various adjuvants (e.g., opioids, corticosteroids and α2-receptor agonists) attempts are made to prolong the time of action of local anesthetics after a single administration in order to achieve the best possible improvement in postoperative analgesia. In this context, ultralong-acting local anesthetics, such as liposomal bupivacaine, which at least theoretically can provide a sensory nerve block for several days, have been developed and clinically introduced. The coming years will show whether these approaches will develop into genuine alternatives to the personnel and cost-intensive continuous nerve blockades.Local anesthetic-induced systemic toxicity is meanwhile rare but still a potentially life-threatening event, frequently resulting from accidental intravascular injection or extensive systemic resorption. Consequently, slow and fractional application of these agents with intermittent aspiration helps to prevent toxic sequelae. If toxic symptoms occur, however, the intravenous infusion of 20% lipid solutions in addition to basic treatment measures can enhance the success of treatment.

[Peripheral truncal blocks-Overview and assessment]. / Periphere Rumpfwandblockaden ­ Übersicht und Bewertung.

By implementation of sonography for regional anesthesia, truncal blocks became more relevant in the daily practice of anesthesia and pain therapy. Due to visualized needle guidance ultrasound supports more safety and helps to avoid complications during needle placement. Additionally, complex punctures are possible that were associated with higher risk using landmarks alone. Next to the blocking of specific nerve structures, interfascial and compartment blocks have also become established, whereby the visualization of individual nerves and plexus structures is not of relevance. The present review article describes published and clinically established puncture techniques with respect to the indications and procedures. The clinical value is reported according to the scientific evidence and the analgesic profile. Moreover, the authors explain potential risks, complications and dosing of local anesthetic agents.

Pre-operative fluid bolus for improved haemodynamic stability during minor surgery: A prospectively randomized clinical trial.

BACKGROUND: Haemodynamic instability during the induction of anaesthesia and surgery is common and may be related to hypovolaemia caused by pre-operative fasting or chronic diuretic therapy. The aim of our prospective, controlled, randomized study was to test the hypothesis that a predefined fluid bolus given prior to general anaesthesia for minor surgery would increase haemodynamic stability during anaesthetic induction. METHODS: Two hundred and nineteen fairly healthy adult patients requiring minor surgery were enrolled. All received standard treatment, including a pulse contour analysing device for non-invasive measurement of cardiac index. Infusion therapy was started in all patients at induction. The intervention group (106 patients) was randomized to receive an additional fluid bolus of 8 mL/kg Ringer's acetate solution before the induction of anaesthesia. The primary endpoint was the incidence of haemodynamic instability, defined as a significant reduction of blood pressure or cardiac index during induction of anaesthesia. RESULTS: The interventional group had a lesser incidence of haemodynamic instability during induction (41.5% vs 56.6%, P = .025). This group also had higher cardiac index, stroke volume index, systolic and mean blood pressure and a greater left ventricular end-diastolic area. CONCLUSIONS: A fluid bolus prior to anaesthesia reduced the incidence of haemodynamic instability during induction of general anaesthesia. The total fluid volume was slightly greater in the intervention group compared to the control group (1370 ± 439 mL vs 1219 ± 483 mL, P = .007). We conclude that a defined fluid bolus can help stabilizing haemodynamics in patients undergoing general anaesthesia.

Intraneural injection of a test dose of local anesthetic in peripheral nerves - does it induce histological changes in nerve tissue?

BACKGROUND & OBJECTIVES: Most anesthesiologists use the injection of a test dose of local anesthetic in order to evaluate the final needle tip position. Thus, the intraneural injection of a full dose can be avoided. The aim of this study was to analyze whether an intraneural injection of a test dose of bupivacaine could trigger histological changes. METHODS: Intraneural injections under direct vision were performed in 40 brachial plexus nerves in seven anesthetized pigs. Tibial nerves served as positive and negative controls. Two milliliter of bupivacaine 0.5% was injected in three nerves on the left brachial plexus. For control of local anesthetic's toxicity Ringer's solution was applied intraneurally on the right side. After maintaining 48 h of general anesthesia, the nerves were resected. The specimens were processed for histological examination and assessed for inflammation (hematoxylin and eosin stain, CD68-immunohistochemistry) and myelin damage (Kluver-Barrera stain). The degree of nerve injury was rated on a scale from 0 (no injury) to 4 (severe injury). RESULTS: Statistical analysis showed no significant differences between the bupivacaine group [median (interquartile range) 1 (1-1.5)] and the Ringer's solution group [1 (0.5-2) P = 0.772]. Mild myelin alteration was found in 12.5% of all specimens following intraneural injection, irrespective of the applied substance. CONCLUSIONS: "In our experimental study, intraneural injection of 2 ml of bupivacaine or Ringer's solution showed comparable mild inflammation. Nevertheless, inflammation can only be prevented by strictly avoiding nerve perforation followed by intraneural injection, as mechanical nerve perforation is a key factor for evolving inflammation.

Tunnelling of thoracic epidural catheters is associated with fewer catheter-related infections: a retrospective registry analysis.

BACKGROUND: Catheter-related infections are a serious complication of continuous thoracic epidural analgesia. Tunnelling catheters subcutaneously may reduce infection risk. We thus tested the hypothesis that tunnelling of thoracic epidural catheters is associated with a lower risk of catheter-related infections. METHODS: Twenty-two thousand, four hundred and eleven surgical patients with continuous thoracic epidural analgesia included in the German Network for Regional Anaesthesia registry between 2007 and 2014 were grouped by whether their catheters were tunnelled (n=12 870) or not (n=9541). Catheter-related infections in each group were compared with Student's unpaired t and χ(2) tests. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated with logistic regression, adjusting for potential confounding factors, including age, ASA physical status score, use of catheter for ≥4 days, multiple skin puncture, hospital, and surgical department. RESULTS: There were fewer catheter-related infections in patients with tunnelled catheters (4.5 vs 5.5%, P<0.001). Mild infections were also less common (4.0 vs 4.6%, P=0.009), as were moderate infections (0.4 vs 0.8%, P<0.001). After adjustment for potential confounding factors, tunnelling remained an independent prevention for any grade of infection (adjusted OR 0.51, 95% CI 0.42-0.61, P<0.001) and for mild infections (adjusted OR 0.54, 95% CI 0.43-0.66, P<0.001) and moderate and severe infections (adjusted OR 0.44, 95% CI 0.28-0.70, P=0.001). CONCLUSION: Tunnelling was associated with a lower risk of thoracic epidural catheter-related infections.

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).

Phrenic palsy and analgesic quality of continuous supraclavicular vs. interscalene plexus blocks after shoulder surgery.

BACKGROUND: Hemidiaphragmatic palsy is a common consequence of the interscalene brachial plexus block. It occurs less commonly with the supraclavicular approach. Register data suggest that the analgesic quality of a supraclavicular blockade is sufficient for arthroscopic shoulder surgery, although data on the post-operative analgesic effect are lacking. METHODS: After approval by the ethics committee, patients having arthroscopic shoulder surgery under general anaesthesia were randomized to receive a continuous interscalene or supraclavicular blockade. Phrenic nerve function was evaluated through ultrasound examination of the diaphragm in combination with spirometry. Pain scores at rest and activity etc. were determined before catheter insertion, during observation in the post- anaesthesia care unit (PACU) and on post-operative day 1 (POD1). The initial application of 10 ml of ropivacaine 0.2% was followed by continuous application of 4 ml of ropivacaine 0.2%, plus a patient controlled analgesia (PCA) bolus of 4 ml/h. RESULTS: One hundred and twenty patients were randomized, of which 114 data sets were analysed. Complete hemidiaphragmatic paresis occurred in 43% of the interscalene group vs. 24% in the supraclavicular group during PACU stay. Rates of dyspnoea and hoarseness were similar. Horner's syndrome occurred in 21% of the interscalene but only 3% of the supraclavicular group on POD1. Pain scores were comparable for pain at rest and during stress at each time point. CONCLUSIONS: This trial showed a significantly greater incidence of phrenic nerve palsy of the interscalene group in PACU, but not on POD1. Post-operative analgesic quality was similar in both groups. Continuous supraclavicular blockade is a suitable alternative to the continuous interscalene technique.

Investigations of initial airtightness after non-anatomic resection of lung parenchyma using a thulium-doped laser with different optical fibres.

Lung metastases in healthy patients should be removed non-anatomically whenever possible. This can be done with a laser. Lung parenchyma can be cut very well, because of its high energy absorption at a wavelength of 1940 nm. A coagulation layer is created on the resected surface. It is not clear, whether this surface also needs to be sutured to ensure that it remains airtight even at higher ventilation pressures. It would be helpful, if suturing could be avoided, because the lung can become too puckered, especially with multiple resections, resulting in considerable restriction. We carried out our experiments on isolated and ventilated paracardiac lung lobes of pigs. Non-anatomic resection was carried out reproducibly using three different thulium laser fibres (230, 365 and 600 µm) at two different laser power levels (10 W, 30 W) and three different resection depths (0.5, 1.0 and 2.0 cm). Initial airtightness was investigated while ventilating at normal frequency. We also investigated the bursting pressures of the resected areas by increasing the inspiratory pressure. When 230- and 365-µm fibres were used with a power of 10 W, 70 % of samples were initially airtight up to a resection depth of 1 cm. This rate fell at depths of up to 2 cm. All resected surfaces remained airtight during ventilation when 600-µm fibres were used at both laser power levels (10 and 30 W). The bursting pressures achieved with 600-µm fibres were higher than with the other fibres used: 0.5 cm, 41.6 ± 3.2 mbar; 1 cm, 38.2 ± 2.5 mbar; 2 cm, 33.7 ± 4.8 mbar. As laser power and thickness of laser fibre increased, so the coagulation zone became thicker. With a 600-µm fibre, it measured 145.0 ± 8.2 µm with 10 W power and 315.5 ± 6.4 µm with 30 W power. Closure with sutures after non-anatomic resection of lung parenchyma is not necessary when a thulium laser is used provided a 600-µm fibre and adequate laser power (30 W) are employed. At deeper resection levels, the risk of cutting small segmental bronchi is considerably increased. They must always be closed with sutures.

[Glucocorticoids as an adjunct in peripheral regional anesthesia. Move to the "Holy Grail of perineural analgesia"?!]. / Glucocorticoide als Adjuvanz in der peripheren Regionalanästhesie : Unterwegs zum "Heiligen Gral der perineuralen Analgesie"?!

BACKGROUND: The role of dexamethasone as an adjunct in peripheral nerve blockades is still unclear. OBJECTIVES: This article reviews the actual knowledge and scientific evidence for dexamethasone as an adjunct in peripheral regional anesthesia. Moreover, it discusses the benefits of the systemic versus the perineural mode of application. RESULTS: Dexamethasone prolongs sensible as well as motor blockades in peripheral nerve blocks when applied intravenously or perineurally. Regarding potentially local neurotoxicity, published patient data are not sufficient for final conclusions. CONCLUSIONS: After reviewing the actual literature, the authors prefer a systemic application mode (intravenously) over a perineural route of administration of dexamethasone as an adjunct for peripheral nerve blocks. This is due to the better understanding of potential side effects of the drug when applied intravenously. Dexamethasone might be a useful drug adjunct to prolong peripheral single shot nerve blocks.

[Bipolar Sealing of Lung Veins with 5 mm and 10 mm Instruments - Bursting Pressures Measured in an Ex-Vivo Model]. / Bipolare Versiegelung von Lungenvenen mit einem 5- und -10-mm-Instrument - Bestimmung der Berstdrücke an einem Ex-vivo-Modell.

BACKGROUND: In every anatomic lung resection, lung veins need to be sealed and divided. If open surgery is performed, veins are usually treated with ligatures. In minimally-invasive procedures a vascular stapler is used. Blood vessels can be securely closed with modern bipolar sealing technology. Since this method has rarely been used in lung veins, we carried out the present study on an ex-vivo model to test whether satisfactory bursting pressures can be achieved using 5 mm and 10 mm MARSEAL® sealing instruments. MATERIAL AND METHODS: The experimental investigations were carried out on heart-lung preparations (including both lungs) from freshly-slaughtered pigs (weight: 199 lbs). After the lung veins were dissected, three groups were formed according to size: group 1: 1-7 mm, group 2: 8-10 mm and group 3: > 10 mm. Bipolar sealing was performed with a 5 mm or 10 mm MARSEAL® sealing device and the special SealSafe® G5 electric current. Vessels closed by simple ligation served as a control group. A pressure sensor was implanted into the unsealed end of the blood vessel. Air was pumped into the blood vessel and the bursting pressure - the pressure (in mbar) at which the vessel began to leak - was determined digitally. The mean bursting pressures were compared using the non-parametric Mann Whitney U test (the level of significance was p < 0.05). RESULTS: In group 1 the mean bursting pressures for the 5 mm and 10 mm instruments were found to be 167.1 ± 38.7 mbar and 113.8 ± 23.3 mbar, respectively. Both were significantly inferior to the pressure of 178.8 ± 44.5 mbar achieved by the control group. In group 2 the bursting pressures were 122.7 ± 27.8 mbar with the 5 mm instrument and 93.5 ± 39.6 mbar with the 10 mm instrument. The mean bursting pressure for the control group was 180.7 ± 35.8.mbar. In group 3 the mean bursting pressures were 98.2 ± 28.8 mbar with the 5 mm instrument and 65.5 ± 19.7 mbar with the 10 mm instrument. All attempts to seal the entire left atrium failed. CONCLUSION: In our ex-vivo model of lung veins, acceptable bursting pressures were achieved in blood vessels with a maximum diameter of 10 mm. Bipolar impedance-controlled sealing may create an adequate seal on pulmonary veins up to a diameter of 10 mm. The use of a 10 mm instrument has no advantage compared to a 5 mm instrument. Secure sealing of the left atrium is not possible.

Bipolar sealing of lung parenchyma: tests in an ex vivo model.

BACKGROUND: Almost every pulmonary lobe resection requires cutting the lung parenchyma in the area of a lung fissure. A monopolar cutter or stapler is often used for this purpose. The seal should be absolutely airtight to prevent post-operative pulmonary fistulas. In the present study, the bipolar sealing technique was evaluated regarding air tightness of the seals during normal ventilation and its burst pressure in an ex vivo animal model. MATERIALS AND METHODS: The investigations were carried out on paracardial lung lobes obtained from heart-lung preparations taken from freshly killed pigs at a slaughter house. In the laboratory, each individual lobe was perfused with Ringer's solution at body temperature and protectively ventilated through a tube (frequency: 20 1/min, p insp = 20 mbar, PEEP +5 mbar). Non-anatomic resection was carried out in the periphery of the lung lobe. The two control groups (12 lobes per group; Group 1-stapler, Group 2-parenchyma suture) were compared to three groups in which different bipolar sealing instruments were used. They were Group 3-MARSEAL(®) 10 mm (KLS Martin, Tuttlingen); Group 4-MARSEAL(®) 5 mm; and Group 5-MARCLAMP(®) (KLS Martin, Tuttlingen). The SealSafe(®) G3 electric current was used in all cases. Ventilation was continued for 20 min following parenchymal resection. Parenchymal sealing was then judged visually in a water bath and given a score (0-3). Burst pressure (mbar) was measured by increasing the inspiration pressure stepwise. Group mean values were compared (nonparametric Mann-Whitney U test, p < 0.005). RESULTS: Parenchymal seals were airtight under ventilation throughout the observation period in all groups. Mean burst pressures were as follows: Group 1: 47.1 ± 6.2 mbar; Group 2: 32.9 ± 3.9 mbar; Group 3: 38.8 ± 2.2 mbar; Group 4: 25.0 ± 6.4 mbar; and Group 5: 32.9 ± 5.8 mbar. Group 1, the stapler group, thus exhibited the highest burst pressures. Burst pressures for Group 3 were significantly greater than those for Group 2 (p < 0.006). Burst pressures for groups 2 and 5 were similar (p = 0.97). However, the burst pressures for Group 4 were significantly lower than those for Group 2 (p < 0.001). CONCLUSION: MARSEAL(®) 10 mm and MARCLAMP(®) achieved adequate burst pressures compared to the two control groups and thus might be suitable for clinical use.

Obesity in regional anesthesia--a risk factor for peripheral catheter-related infections.

BACKGROUND: Obesity is believed to increase the risk of surgical site infections and possibly increase the risk of catheter-related infections in regional anesthesia. We, therefore, analyzed the influence of obesity on catheter-related infections defined within a national registry for regional anesthesia. METHODS: The German Network for Regional Anesthesia database with 25 participating clinical centers was analyzed between 2007 and 2012. Exactly, 28,249 cases (13,239 peripheral nerve and 15,010 neuraxial blocks) of patients ≥ 14 years were grouped in I: underweight (BMI 13.2-18.49 kg/m(2) , n = 597), II: normal weight (BMI 18.5-24.9 kg/m(2) , n = 9272), III: overweight (BMI 25.0-29.9 kg/m(2) , n = 10,632), and IV: obese (BMI 30.0-70.3 kg/m(2) , n = 7,744). The analysis focused on peripheral and neuraxial catheter-related infections. Differences between the groups were tested with non-parametric ANOVA and chi-square (P < 0.05). Binary logistic regression was used to compare obese, overweight, or underweight patients with normal weight patients. Odds ratios (OR and 95% confidence interval) were calculated and adjusted for potential confounders. RESULTS: Confounders with significant influence on the risk for catheter-related infections were gender, age, ASA score, diabetes, preoperative infection, multiple skin puncture, and prolonged catheter use. The incidence (normal weight: 2.1%, obese: 3.6%; P < 0.001) and the risk of peripheral catheter-related infection was increased in obese compared to normal weight patients [adjusted OR: 1.69 (1.25-2.28); P < 0.001]. In neuraxial sites, the incidence of catheter-related infections differed significantly between normal weight and obese patients (normal weight: 3.2%, obese: 2.3%; P = 0.01), whereas the risk was comparable [adjusted OR: 0.95 (0.71-1.28); P = 0.92]. CONCLUSION: This retrospective cohort study suggests that obesity is an independent risk factor for peripheral, but not neuraxial, catheter-related infections.

Local inflammation in fracture hematoma: results from a combined trauma model in pigs.

Background. Previous studies showed significant interaction between the local and systemic inflammatory response after severe trauma in small animal models. The purpose of this study was to establish a new combined trauma model in pigs to investigate fracture-associated local inflammation and gain information about the early inflammatory stages after polytrauma. Material and Methods. Combined trauma consisted of tibial fracture, lung contusion, liver laceration, and controlled hemorrhage. Animals were mechanically ventilated and under ICU-monitoring for 48 h. Blood and fracture hematoma samples were collected during the time course of the study. Local and systemic levels of serum cytokines and diverse alarmins were measured by ELISA kit. Results. A statistical significant difference in the systemic serum values of IL-6 and HMGB1 was observed when compared to the sham. Moreover, there was a statistical significant difference in the serum values of the fracture hematoma of IL-6, IL-8, IL-10, and HMGB1 when compared to the systemic inflammatory response. However a decrease of local proinflammatory concentrations was observed while anti-inflammatory mediators increased. Conclusion. Our data showed a time-dependent activation of the local and systemic inflammatory response. Indeed it is the first study focusing on the local and systemic inflammatory response to multiple-trauma in a large animal model.

[Improvement of sonographic visualization of cannula needle tips by alignment of the needle lumen : In vitro investigation of established needle tip forms]. / Verbesserung der sonographischen Sichtbarkeit von Kanülenspitzen durch Ausrichtung der Öffnungsfläche : In-vitro-Untersuchung etablierter Schliffformen.

BACKGROUND: In the context of ultrasound-guided peripheral nerve blocks (regional anesthesia), clear visualization of the needle tip and the target structure are mandatory for the performance of a safe puncture and injection. The purpose of this in vitro study was to analyze the visualization of different forms of needle tips and calibers of cannulas in a phantom simulating human tissue, with the help of a standardized image analysis system. Different depths and angles of the puncture needle in relation to the ultrasound probe were tested. MATERIAL AND METHODS: Cannula needles established for use in regional anesthesia with different surfaces, diameters and needle tip form in 23 different combinations were analyzed. A gelatine-based phantom was used to simulate human tissue. The standardized visualization of the needle tip with the ultrasound probe was performed in plane at different angles (30°, 45° and 60°), depths of penetration (1 cm, 2 cm and 3 cm) and two different alignments of the cannula needle lumen to the ultrasound probe (0° and 180°). The screenshots of the ultrasound pictures were analyzed by quantifying the pixel brightness around the needle tip (region of interest) with a standardized software (score 0-255). RESULTS: In this study 1104 ultrasound images of cannula needles were analyzed. Diminished scores (reduced pixel brightness) of the needle tips were documented with increasing distance from the ultrasound probe. Comparison of punctures at angles of 30° and 45° showed no differences in needle tip visibility (same scores) but punctures at an angle of 60° were poorly visualized compared with 30° and 45° (mean scores 87.90 ± 11.60 vs. 78.40 ± 12.07, p < 0.001 and 81.85 ± 11.79 vs. 78.40 ± 12.07, p < 0.001, respectively). The direct alignment of the cannula lumen towards the ultrasound probe (0°) was significantly more easily visualized when compared with the reverse alignment of 180° (mean scores 86.90 ± 12.74 vs. 84.80 ± 11.66, p = 0.003, respectively). No differences in visibility were detected between the different cannula needle diameters examined. The Sprotte cannula showed the best visibility score with respect to the cut of the needle tip (mean score 89.40 ± 11.72). CONCLUSION: The visibility of cannulas in ultrasound scans depends on the ultrasound frequency, angle of the puncture in relation to the ultrasound probe and the depth of penetration. The results of this study showed that direct alignment of the cannula needle lumen towards the ultrasound probe (0°) independently improved needle tip visualization. This simple measure allows a significant improvement in the safe performance of ultrasound-guided peripheral nerve blocks.

Peripheral nerve blocks on the upper extremity: Technique of landmark-based and ultrasound-guided approaches.

The German Society of Anaesthesiology and Intensive Care Medicine (Deutsche Gesellschaft für Anästhesiologie und Intensivmedizin, DGAI) established an expert panel to develop preliminary recommendations for the application of peripheral nerve blocks on the upper extremity. The present recommendations state in different variations how ultrasound and/or electrical nerve stimulation guided nerve blocks should be performed. The description of each procedure is rather a recommendation than a guideline. The anaesthesiologist should select the variation of block which provides the highest grade of safety according to his individual opportunities. The first section comprises recommendations regarding dosages of local anaesthetics, general indications and contraindications for peripheral nerve blocks and informations about complications. In the following sections most common blocks techniques on the upper extremity are described.

[Localization of peripheral nerves. Success and safety with electrical nerve stimulation]. / Lokalisation peripherer Nerven. Erfolg und Sicherheit mit elektrischer Nervenstimulation.

Peripheral electrical nerve stimulation is one of the standard applications in peripheral regional anesthesia in addition to the ultrasound technique. Among other findings, the visualization of needle and nerve during ultrasound-guided blockade caused a change in clinical practice of peripheral nerve stimulation in the last decade. In the present article old and new aspects of principles and clinical practice of the nerve stimulation technique are presented and summarized in a total clinical concept in order to achieve safe and successful peripheral regional anesthesia using electrical peripheral nerve stimulation.

[Seeing more : Technical innovations in regional anesthesia]. / Mehr sehen : Technische Innovationen in der Regionalanästhesie.

Visualization and verification are key factors since the implementation of ultrasound-guided regional anesthesia. This article reviews and discusses newer technical innovations in regional anesthesia with regard to optimization of needle guidance, improvements in needle visibility, technical improvements in ultrasound techniques and innovative technologies in regional anesthesia. Clinically available applications are presented as well as experimental tools and techniques with a potential for clinical implementation in the future. Mechanical needle guides are used to improve alignment of needle axis and ultrasound beam axis. Compound imaging technology improves needle visibility in steep needle insertion angles and is already implemented in daily clinical practice. Sonoelastography improves tissue discrimination and detection of small amounts of fluids. Benefits of 3D and 4D ultrasound in regional anesthesia are discussed as well as experimental tools for tissue discrimination, such as optical reflection spectrophotometry.

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

The German Society of Anaesthesiology and Intensive Care Medicine (Deutsche Gesellschaft für Anästhesiologie und Intensivmedizin, DGAI) established an expert panel to develop preliminary recommendations for nerve localization in peripheral regional anesthesia. Based on expert knowledge and the relatively limited data, the recommendations state how ultrasound and/or electrical nerve stimulation should be used in daily practice, and where and when local anesthetics should be injected. Moreover, it was defined under which conditions a peripheral nerve block under general anesthesia or deep sedation is applicable.Regarding the use of ultrasound the expert opinion was that out-of-plane and in-plane-techniques can be considered equal with respect to patient safety. Nevertheless, the direct or indirect visualization of the needle tip has to be assured. The injection of local anesthetics has to be visualized. Injections into nerves or those requiring an injection pressure should be avoided. The sole use of electrical nerve stimulation or ultrasound for nerve localization is still a suitable option as well as their combined use. To avoid accidental intraneural needle placement, an electrical current threshold ≥ 0.5 mA should be used. Moreover, it was stated that peripheral nerve blocks or continuous nerve block techniques under sedation or general anesthesia are applicable in adult patients who are unable to tolerate the block being performed in an awake state or have difficulty cooperating.This article is published in English.

[Peripheral regional anesthesia in patients under general anesthesia: risk assessment with respect to parasthesia, injection pain and nerve damage]. / Periphere Regionalanästhesie beim Patienten in Allgemeinanästhesie : Risikobewertung bezüglich Parästhesie, Injektionsschmerz und Nervenschäden.

Nerve injury after peripheral regional anesthesia is rare and is not usually permanent. Some authors believe that inducing peripheral nerve blocks in patients during general anesthesia or analgosedation adds an additional risk factor for neuronal damage. This is based on published case reports showing that there is a positive correlation between paresthesia experienced during regional anesthesia and subsequent nerve injury. Therefore, many sources recommend that regional nerve blocks should only be performed in awake or lightly sedated patients, at least in adults. However, there is no scientific basis for this recommendation. Furthermore, there is no proof that regional anesthesia performed in patients under general anesthesia or deep sedation bears a greater risk than in awake or lightly sedated patients. Currently anesthesiologists are free to follow personal preferences in this matter as there is no good evidence favoring one approach over the other. The risk of systemic toxicity of local anesthetic agents is not higher in patients who receive regional anesthesia under general anesthesia or deep sedation. Finally, in children and uncooperative adults the administration of peripheral nerve blocks under general anesthesia or deep sedation is widely accepted.