Die axilläre Blockade des Plexus brachialis

Zusammenfassung.

In einer prospektiven Untersuchung wurde überprüft, ob die axilläre Plexus-brachialis-Blockade mit der Technik der elektrischen Nervenstimulation an einer Universitätsklinik mit einer ausreichend hohen Erfolgsrate angewandt werden kann, obwohl der einzelne Anästhesist nur sehr wenige Blockaden durchführt. Von 112 untersuchten Blockaden waren 95 (85%) erfolgreich, 17 (15%) benötigten primär eine Vollnarkose. Bei 8 erfolgreichen Blockaden mußte nach ≥70 min Operationszeit auf ein supplementierendes Verfahren übergegangen werden. Der Blockadeerfolg war nicht abhängig von der Erfahrung des Anästhesisten. Die minimal erreichte Stromstärke für die Nervenstimulation war mit 0,4 vs. 0,6 mA in der erfolgreichen Gruppe signifikant kleiner. Signifikant größer war bei den erfolgreichen Blockaden die Dosis des Lokalanästhetikums 5,9 vs. 5,3 mg/kg KG Mepivacain 1%. Aus dieser Untersuchung sind folgende Schlußfolgerungen zu ziehen: Mit Hilfe der Methode der elektrischen Nervenstimulation ist die axilläre Plexus-brachialis-Blockade auch ein geeignetes Anästhesieverfahren für Ausbildungskliniken, in denen der einzelne Anästhesist nur selten diese Technik durchführt. Die minimal erreichte Stromstärke bei der Nervenstimulation sollte <0,5 mA sein. Um ein ausreichendes Volumen zu injizieren, sollte bei dem Lokalanästhetikum Mepivacain 1% die Dosis wenigstens 6 mg/kg KG betragen.

Abstract.

Axillary block is a common anaesthetic technique for operations on the hand and forearm. In our hospital, with many trainees in anaesthesia, only 250 – 300 axillary blocks per year are performed by about 30 colleagues. This implies a small number of blocks for each anaesthetist. The present study was designed to assess whether it is possible to teach this technique and use it with an adequate degree of success under these conditions. We used a nerve stimulator and studied whether the success of the block under these conditions is independent of anaesthetist's experience in this technique. Furthermore, we examined other factors involved in the success of the block. Methods. The study included 112 patients subjected to elective surgery of the upper extremity; all received an axillary block. We used a nerve stimulator and injected mepivacaine 1% without adrenaline. The following parameters were recorded: the number of blocks to date performed by the anaesthetist; the minimal current required for nerve stimulation; the dose of local anaesthetic; the time between the end of injection and the beginning of surgery; the duration of surgery; and the quality of sensory and motor blockade after 10, 20, and 30 min. Sensory blockade was assessed by the pinprick method (no blockade, analgesia, anaesthesia); motor blockade was judged by comparing the muscle strength of both arms (no blockade, paresis, paralysis). Data were analyzed using the Mann-Whitney test, with P<0.05 considered statistically significant. Results. Of the 112 blocks, 95 (85%) were successful; 17 (15%) failed and the patients required general anaesthesia. Eight of the successful blocks showed a decrease in analgesic quality after ≥70 min and required additional analgesics or general anaesthesia. We found no correlation between the experience of the anaesthetist and the success of the block. The minimal required current for nerve stimulation in the success group was 0.4 mA and differed significantly from the value of 0.6 mA in the failure group (Table 3). The dose of mepivacaine was higher in the success group (5.9 vs. 5.3 mg/kg). Complete sensory blockade was more frequently achieved for the median, ulnar, and radial nerves than for the musculocutaneous and cutaneous brachii medialis (Fig. 3). The frequency of complete sensory blockade (anaesthesia) had increased by 21.9% between the 20th and 30th min. Complete motor blockade was less often achieved than sensory blockade (Fig. 4). Conclusions. Using the method of electrostimulation, the axillary block is an appropriate anaesthetic technique that can be applied in a hospital where each anaesthetist only occasionally performs it. Prior to injection of the local anaesthetic, the current for nerve stimulation should be reduced to <0.5 mA. The time between the end of injection and the beginning of surgery should be no less than 30 min because complete sensory blockade can more often be achieved. The dose of mepivacaine should be no less than 6 mg/kg body weight.