RU2107459C1 - Method and device for searching nerves and plexus nervosus - Google Patents

Abstract

FIELD: medicine; medical engineering. SUBSTANCE: method involves introducing electrode needle into soft tissues, moving it towards the nerve and acting with pulsating electric current at the point of probable nerve path. The following determination of nerve location is related to muscle contractions observed. The action is carried out by applying current of 0.3-2.0 Hz frequency with pulse duration being equal to 0.1-3.0 ms and voltage of 2.5-9.0 V. The device has master oscillator, circuit for setting pulse duration, amplifying stage and output stage. Tuning members as variable resistors are introduced into the master oscillator and circuit for setting pulse duration. EFFECT: painless search procedure. 2 cl, 1 dwg

Description

 The invention relates to medical equipment and can be used to search for nerves and nerve plexuses, in particular when performing conduction anesthesia.

 There are various ways to search for nerves: for example, Peters suggested using a faradic current, feeding it to a steel needle, varnished to the tip, but this method did not find application in view of its great technical inconveniences. For such purposes, it was proposed to use a pacemaker [1] with a constant rectangular current of 0.3-1 mA. However, the electrical parameters of this device do not allow to search for nerve trunks smoothly without unpleasant sensations for the patient.

 Closest to the proposed technical solution is a method of searching for nerves and nerve plexuses [2], which is carried out by electrical irritation of nerves and plexuses with current pulses with a frequency of 1 Hz and a duration of 0.1 ms.

 However, such parameters of electroirritation do not allow a differentiated approach to the search for nerves and plexuses in various categories of patients, especially in patients with severe limb injuries or, if necessary, repeated blockade of partially anesthetized nerves.

 A device for implementing the method consists of a master oscillator on a chip D1, and in parallel with the elements D1, D2, D3 is connected a resistance that determines the frequency of the generating signal, a differentiation circuit for the pulse duration on the chip D2, which is connected in parallel with the output of the trigger with a resistance that determines the pulse duration, the amplification stage and output stage.

 However, this device has strictly fixed parameters that do not allow you to adjust the duration and frequency of the pulses. In addition, there are no techniques for topography of nerve trunks to the device, which makes it difficult for young specialists to learn regional anesthesia techniques.

 The objective of the invention is the painlessness of the procedure due to the differentiated approach to the search for nerves and nerve plexuses in different categories of patients and its acceleration, as well as expanding the functionality of the device.

 This problem is solved due to the fact that a needle-electrode is inserted into the soft tissues and, advancing it towards the nerve, is affected by a pulsed electric current with a frequency of 0.3-2 Hz, a duration of 0.1-3 ms at a voltage of 2.5 - 9 V.

 At the point of the alleged passage of the nerve and determine its location by the appearance of muscle contractions. Variable resistors are introduced into the master oscillator and into the pulse duration generation circuit, and external landmark circuits for performing regional anesthesia on the upper limbs are applied to the device panels.

 With a decrease in the pulse frequency of less than 0.3 Hz, the time for searching for nerves is lengthened, and with an increase of more than 2 Hz, patients experience unpleasant subjective sensations due to frequent muscle contraction. The pulse duration of less than 0.1 ms in 60% of cases is inefficient and requires an increase in its voltage or current, and an increase of more than 3 ms has no advantages over the proposed parameters.

 The method is as follows: the negative electrode of the device is connected to any skin point of the patient, and the positive one is connected to a sterile injection needle, with which a search is performed. The needle advances in the direction of the proposed location of the nerve trunk during electrical stimulation by electric current pulses, the frequency of which varies from 0.3 to 2.0 Hz, and the duration from 0.1 to 3.0 ms at a voltage of 2.5-9 V. plexus rectangular current pulses of the specified parameters leads to contraction of muscles innervated by the irritated nerve, which serves as an objective criterion for the location of the needle relative to the nerve trunk.

 In patients with severe limb injuries, nerve searching is performed with a decrease in frequency to 0.3-0.5 Hz (1 pulse for 2-3 s) at a voltage of 2.5-3.5 V and a pulse duration of 0.1 ms, due to which rare (1 reduction in 2-3 s) and weak contractions of the muscles innervated by the nerve occur, which do not lead to significant amplitude of limb movements and avoid significant pain and further trauma to the limb when searching for nerve trunks and plexuses.

 If necessary, in the repeated blockade of partially anesthetized nerves (for example, with signs of restoration of sensitivity in the area of surgical intervention during prolonged operations), the pulse duration is extended to 3 ms, which increases the strength of electrical irritation and reduces the probability of needle damage to partially anesthetized nerves.

 The drawing shows a device for searching for nerves.

 It contains a master oscillator 1, a pulse duration 2 generation circuit, a gain stage 3 and an output stage 4. The master oscillator 1 is assembled on a microcircuit 5, in parallel with which a chain of resistors 6 and 7 and a capacitor 8 are connected, and the resistor 7 is variable. The circuit for forming the pulse duration 2 is made on a microcircuit 9, in parallel to which a chain of resistors 10, an alternating 11, and a diode 12 are connected with a capacitance 13 connected in series to it.

 The output of the pulse width formation circuit 2 is connected through a resistor 14 to the input of the amplification stage 3 assembled on the transistor 15, the resistor 16 and the variable resistor 17. The output stage 4, assembled on the transistor 18 and the resistor 19, is used to coordinate the output resistance of the device with the resistance of human tissues .

 The device operates as follows: from the output of the master oscillator 1, the signal arrives at the clock input of the microcircuit 9, the pulse width 2 formation circuit, at the output of which a pulse of positive polarity appears. By changing the value of the variable resistor 11, you can change the pulse duration in the range from 0.1 to 3 ms. The diode 12 serves to quickly discharge the capacitance 13, which affects the steepness of the edges of the generated signal.

 From the output of the pulse forming circuit 2, a sequence of rectangular pulses with an adjustable frequency and duration falls on the amplification stage 3 on the transistor 15, where the signal is amplified by power. The output of the amplification stage 3 is a variable resistor 17, from which part of the signal is fed to the output stage 4.

 Using a variable resistor 17, the amplitude of the output signal is regulated with a range from 0 to 9 V.

 Example 1. Patient Sh., 42 years old (source. Bol. N 160918) was delivered to NNIITO on 10.06.94 with a diagnosis of severe mechanical injury to the right hand. The operation of the primary surgical treatment of wounds of the right hand was decided to be performed under conduction anesthesia.

 In order to quickly search for the brachial plexus, the device we proposed was used. A passive (negative) electrode was superimposed on the inner surface of the right forearm. In the area of the projection of the brachial plexus according to Kulenkampf, a needle is inserted with an active electrode connected to it. The search parameters are set on the device: voltage 4 V, frequency 0.3 Hz, pulse duration 0.1 ms. During electrical irritation of the brachial plexus by current with the above parameters, muscle contractions were noted immediately after the start of the search, they were rare, insignificant in amplitude and painless. 1% 40 ml of lidocaine was injected through a needle, anesthesia occurred after 5 minutes, and the initial surgical treatment of the wound was performed without pain for the patient.

 Example 2. Patient V., 26 years old (source. Bol. N 160973). Operated on 04/05/94. plastic surgery of the median nerve defect with a nerve graft from n. suralis on microanastomoses. To isolate the transplant, sciatic nerve anesthesia was performed on the right, for the search of which the device we proposed was used. A passive electrode was located on the inner surface of the right thigh. An active electrode was attached to the needle, which was punctured in the direction of the alleged location of the nerve trunk. With the given parameters: frequency 1 Hz, pulse duration 0.1 ms, voltage 6 V, weak contractions of the muscles of the back surface of the lower leg appeared without any unpleasant sensations of the patient. Injected 1% 20 ml of lidocaine, after 15 minutes anesthesia occurred. Using the same parameters, a blockade of the right femoral nerve was performed. After 3.5 hours during the operation, the patient developed minor pains, which required repeated blockade of the sciatic nerve. Verification of the position of the needle of the relative nerve trunk was carried out with the following parameters: frequency 2 Hz, pulse duration 3 ms, voltage 9 V. There were weak muscle contractions in response to stimulation. 1% 20 ml of lidocaine was introduced, after which adequate anesthesia occurred.

 After the nerve graft was taken for the period of the median nerve plasty, the patient underwent general anesthesia by intravenous administration of relanium, sodium oxybutyrate and fentanyl.

 Thus, the electric stimulator in our modification allows a differentiated search for nerves and nerve plexuses of different categories of patients due to changing frequency parameters and duration of electrical stimulation at different voltage levels. It allows you to painlessly perform a blockade in urgently admitted patients with severe limb injuries in a shorter time and reduce the number of failures during repionary anesthesia.

 The device can also be used when performing reconstructive operations on peripheral and central nerve trunks, for the diagnosis of anatomical damage or functional capabilities of the nerve.

 On the external surface of the device, external reference points of accesses to the brachial plexus and nerves of the upper limb are plotted, as well as reference points of access to the nerves of the lower limb, which makes it possible to use the proposed device in the process of teaching the technique of conduction anesthesia and, thereby, expand its functionality.

Claims (2)

 1. The method of searching for nerves and nerve plexuses, including the introduction of a needle-electrode into the soft tissues, its advancement towards the nerve, exposure to pulsed electric current at the point of the supposed passage of the nerve and determining its location by the appearance of muscle contractions, characterized in that the exposure current frequency 0.3 - 2.0 Hz, pulse duration 0.1 - 3.0 ms, voltage 2.5 - 9 V.  2. A device for searching for nerves and nerve plexuses, containing a serially connected master oscillator, a pulse shaper, an amplifier and an output unit, characterized in that control elements in the form of variable resistors are introduced into a given generator and a pulse shaper.