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Combined Procedure (“Dual Guidance“)

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Time and again the question arises whether in the long run ultrasound will ring in the end of the era of electrical nerve stimulation. In our view, this is neither desirable nor to be expected for two reasons.

The first is that simultaneous use of ultrasound and nerve stimulation provides the less experienced user with an additional means of identifying nerve structures. The second is that the combination of difficult anatomic conditions (e.g. massive obesity) and a deep block (e.g. a psoas block, or proximal sciatic block) can make it difficult even for the experienced ultrasonographer to display the target region, thus requiring additional use of a nerve stimulator to provide certainty. Whenever we see it as not only feasible but also extremely appropriate, we refer explicitly to the use of „dual guidance“ in discussing the individual block techniques.

 

Evaluation of Nerve Stimulation and Ultrasound “Dual Guidance“

For many years, electrical nerve stimulation has been an established method for localizing peripheral nerves. When used systematically, success rates of far more than 90% can – and should – be achieved. In addition, few references to persisting nerve damage from the use of nerve stimulation are found in the literature. The method is therefore absolutely well-established from the viewpoint of safety aspects as well. As recent studies have shown, it is doubtful that this reassuring fact is invariably due to maintenance of a safe distance between the nerve and the needle and adherence to certain „rules of stimulation“, as was postulated in the past. In any case, the basic requirement, in addition to use of a suitable needle and stimulator material, is a study of anatomic features and landmarks and regular - at best daily - use in actual practice. The fact that individual anatomic features and potential variations can be shown in an image contributes significantly to the anaesthetist‘s options in (peripheral) regional anaesthesia. In many cases, an improvement in puncture accuracy and patient safety is attributed to the direct visualization of the needle and target structures. It will not escape the notice of colleagues who begin to deal with this technique with due capacity for self-criticism that here too only regular practice can have the result of meeting this requirement. Especially in the case of deep techniques such as proximal sciatic nerve blocks or the psoas block, where ultrasound sometimes reaches its physical limits, nerve stimulation continues to have its place. We speak in this context of a so-called „Dual Guidance“ in which both techniques are used parallel to one another. In summary, ultrasound and nerve stimulation from our point of view are not competitive techniques but rather enhance each other.