[Distal sciatic nerve blocks: randomized comparison of nerve stimulation and ultrasound guided intraepineural block]. / Distale Blockaden des N. ischiadicus : Randomisierter Vergleich zwischen Nervenstimulation und ultraschallgestützter intraepineuraler Blockade.

BACKGROUND AND OBJECTIVES: The design of this study is related to an important current issue: should local anesthetics be intentionally injected into peripheral nerves? Answering this question is not possible without better knowledge regarding classical methods of nerve localization (e.g. cause of paresthesias and nerve stimulation technique). Have intraneural injections ever been avoided? This prospective, randomized comparison of distal sciatic nerve block with ultrasound guidance tested the hypothesis that intraneural injection of local anesthetics using the nerve stimulation technique is common and associated with a higher success rate. MATERIAL AND METHODS: In this study 250 adult patients were randomly allocated either to the nerve stimulation group (group NS, n = 125) or to the ultrasound guidance group (group US, n = 125). The sciatic nerve was anesthetized with 20 ml prilocaine 1% and 10 ml ropivacaine 0.75%. In the US group the goal was an intraepineural needle position. In the NS group progress of the block was observed by a second physician using ultrasound imaging but blinded for the investigator performing the nerve stimulation. The main outcome variables were time until readiness for surgery (performance time and onset time), success rate and frequency of paresthesias. In the NS group needle positions and corresponding stimulation thresholds were recorded. RESULTS: In both groups seven patients were excluded from further analysis because of protocol violation. In the NS group (n = 118) the following needle positions were estimated: intraepineural (NS 1, n = 51), extraparaneural (NS 2, n = 33), needle tip dislocation from intraepineural to extraparaneural while injecting local anesthetic (NS 3, n = 19) and other or not determined needle positions (n = 15). Paresthesias indicated an intraneural needle position with an odds ratio of 27.4 (specificity 98.8%, sensitivity 45.9%). The success rate without supplementation was significantly higher in the US group (94.9% vs. 61.9%, p < 0.001) and the time until readiness for surgery was significantly (p < 0.001) shorter for successful blocks: 15.1 min (95% confidence interval CI 13.6-16.5 min) vs. 28 min (95% CI 24.9-31.1 min). In the NS subgroups the results were as follows (95% CI in brackets): NS1 88.2% and 22.7 min (19.5-25.9 min), NS2 24.2% and 43.3 min (35.5-51.1 min) and NS3 36.8% and 35.3 min (22.1-48.4 min). CONCLUSIONS: For distal sciatic nerve blocks using the nerve stimulation technique, intraepineural injection of local anesthetics is common and associated with significant and clinically important higher success rates as well as shorter times until readiness for surgery. In both groups no block-related nerve damage was observed. The results indicate that for some blocks (e.g. sciatic, supraclavicular) perforation of the outer layers of connective tissue was always an important prerequisite for success using classical methods of nerve localization (cause of paresthesias and nerve stimulation technique). Additional nerve stimulation with an ultrasound-guided distal sciatic nerve block cannot make any additional contribution to the safety or success of the block. New insights concerning the architecture of the sciatic nerve are discussed and associated implications for the performance of distal ultrasound-guided sciatic nerve block are addressed.

[LMA CTrach: initial experiences in patients with difficult-to-manage airways]. / LMA CTrach: Erste Erfahrungen bei Patienten mit schwieriger Atemwegssicherung.

BACKGROUND: The Intubating LMA was designed to facilitate blind intubation and to provide ventilation between two intubation attempts. However, blind intubation can be associated with a risk of oesophageal penetration, therefore, a flexible bronchoscope is frequently used to assist tracheal intubation. This leads to increased burdens on materials and personal resources and prolongs intubation times. Hence the LMA CTrach laryngeal mask airway (CTrach) was developed with an integrated fibreoptic system which can be connected to a monitor for visualisation of the larynx during intubation. METHODS: We detail the initial experience gained with the practical handling of the CTrach and the application in 10 patients with difficult-to-manage airways. Laryngeal views were graduated in a CTrach-specific classification from grade I (clear view of the arytenoids, glottis and epiglottis) to grade IV (no part of the larynx can be identified). Adjusting manoeuvres were defined to improve the view of laryngeal structures. RESULTS: All patients could be successfully ventilated with the CTrach. Ventilation quality was rated adequate in nine and possible in one patient. The initial distribution of the laryngeal view between grades I-IV was 1/2/1/6 and after adjusting manoeuvres to improve the laryngeal view the grade distribution was 3/5/0/2. Intubation through the CTrach was successful in all patients, nine at first and one at the second attempt. CONCLUSION: In this small sample of patients with difficult-to-manage airways, the CTrach yielded high success rates for both ventilation and tracheal intubation. Adjusting manoeuvres can improve the laryngeal view further.