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The stimulator

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We use the new Stimuplex® HNS 12 nerve stimulator (B. Braun Melsungen) which features the following functions among others:

  • Exact amplitude ranges are selectable between 0 and 1 mA (or 5 mA). The device displays the actual current.
  • Pulse durations of 0.1, 0.3 or 1.0 msec are selectable.
  • The pulse frequency can be set to between 1 or 2 Hz.

At a given current, the electrical current required to trigger muscle contractions correlates with the distance of the tip of the needle to the nerve. That means that the closer the needle is to the nerve, the lower the electrical current that is required to induce contractions or sensory responses. In routine clinical practice, an 1.2 Electrical nerve stimulation Fundamentals Class Function Chronaxie Aa Motor 0.05–0.1 ms Ab Touch, pressure Ag Touch Ad Pain, temperature 0.150 ms B Sympathetic nervous system C Sympathetic nervous system, pain, temperature 0.4 ms 12 initial electrical current, called threshold current, of 1 mA is used to elicit a response. The stimulation needle has reached the desired position at the nerve when contractions of the effector muscle are induced at a threshold current of 0.2 - 0.3 (pulse duration of 0.1 ms). Lower pulse amplitudes may cause injury to the nerve. Therefore, as a general rule, the lowest stimulation current should be determined: This will allow the user to correct the needle position by retracting the needle if it gets too close to the nerve.

We use the new Stimuplex® HNS 12 nerve stimulator (B. Braun Melsungen) which features the following functions among others:

  • Exact amplitude ranges are selectable between 0 and 1 mA (or 5 mA). The device displays the actual current.
  • Pulse durations of 0.1, 0.3 or 1.0 msec are selectable.
  • The pulse frequency can be set to between 1 or 2 Hz.

At a given current, the electrical current required to trigger muscle contractions correlates with the distance of the tip of the needle to the nerve. That means that the closer the needle is to the nerve, the lower the electrical current that is required to induce contractions or sensory responses. In routine clinical practice, an initial electrical current, called threshold current, of 1 mA is used to elicit a response. The stimulation needle has reached the desired position at the nerve when contractions of the effector muscle are induced at a threshold current of 0.2 - 0.3 (pulse duration of 0.1 ms). Lower pulse amplitudes may cause injury to the nerve. Therefore, as a general rule, the lowest stimulation current should be determined: This will allow the user to correct the needle position by retracting the needle if it gets too close to the nerve. At this threshold current, motor fibres can be selectively stimulated by setting a pulse duration of < 150 μs on the nerve stimulator. Pain fibres are not affected at this pulse duration, thereby allowing the patient to experience the electrical nerve stimulation more pleasantly. A pulse duration of >150 μs is selected when a purely sensory nerve, such as the lateral femoral cutaneous nerve, is targeted. The patient will then notice the corresponding paraesthesia in the supply area of the sensory nerve. The pulse duration is usually set at 2 Hz. A higher pulse duration is better for stimulation because a rapid pulse sequence allows a more precise localisation. This virtually eliminates the danger of slipping past the nerve. A lower pulse duration (1 Hz) may be preferable in traumatised patients in order to minimise the pain caused by contractions of the muscle.

stimulator