MXPA97005839A

MXPA97005839A - Two level loading impulse apparatus to facilitate nerve localization during peripheral nerve blocking procedures

Info

Publication number: MXPA97005839A
Application number: MXPA/A/1997/005839A
Authority: MX
Inventors: C Houghton Frederick; L Griffith Richard; J Strowe Robert; C Newell Jonathan; M Edic Peter; F Messina Ralph
Original assignee: Becton Dickinson And Company
Priority date: 1996-08-05
Filing date: 1997-07-31
Publication date: 1998-02-01

Abstract

An electrolocation device is provided to locate a nerve to which anesthesia can be delivered. The apparatus includes a needle assembly having a non-conductive tube with electrically conductive needle cannula secured through the needle cannula, and conductive galvanization in the tube. The conductors are connected with a stimulator that generates high and low alternative load impulses with a constant low current level. The high load impulses generate perceptible muscle jerks immediately after inserting the needle into the patient. The muscle jerks that respond to the high load impulses will reach the maximum in magnitude and the muscle jerks that respond to the low load impulses will become observable as the needle approaches the reference nerve and can not be distinguished from the jolts muscles that respond to high load impulses when the needle is in a position for anesthetic administration

Description

"LOADING IMPULSE TO TWO LEVELS TO FACILITATE THE LOCALIZATION OF THE NERVE DURING THE PROCEDURES OF BLOCKING OF THE PERIPHERAL NERVE " BACKGROUND OF THE INVENTION 1. Field of Invention The present invention relates to an apparatus for efficiently locating a nerve and subsequently supplying an anesthetic to the nerve. 2. Description of the Prior Art. Many medical procedures require that a patient be at least locally anesthetized. A regional anesthesia or nerve block offers advantages in relation to general anesthesia for many medical procedures. For example, a regional anesthesia or nerve block is typically less traumatic for a patient undergoing surgery, and often allows a shorter post-operative recovery. A regional anesthesia or nerve block necessarily requires the location of the nerve to which the anesthetic agent must be administered. The prior art includes methods for locating the nerve. In most methods of the prior art, the doctor typically uses his general knowledge of physical anatomy to locate approximately the reference nerve. In accordance with a method of the prior art, an electrically conductive pad is placed on the skin in a portion of the patient's body at a distance from the reference nerve. For example, if the reference ridge is in the shoulder, the electrically conductive pad can be secured at a distant portion of the arm. The electrically conductive pad is connected by a wire with a stimulator box of the prior art which is capable of generating an electric current, as will be further explained herein. An electrically isolated needle cannula with a non-isolated conductive tip is then pushed through the skin and subcutaneous tissue in the general direction of the nerve to be anesthetized. The needle of the prior art is connected by a wire with an electrical stimulator box of the prior art. The stimulator box of the prior art is electrically energized and operates to produce an adjustable current pulse over a duration of about 100 to 200 microseconds ("uS"). The current pulse is initially graduated to a level of approximately 1.0 to 5.0 iliampers ("mA"). This level of current is typically sufficient to stimulate the reference nerve when the needle has been placed within the tissue in the approximate area of the reference nerve. The stimulus will cause a perceptible muscular shock in the areas of the body controlled by the reference nerve (eg, the fingers). The current is then slowly discharged until the shaking disappears. The needle of the prior art is then advanced slowly towards the reference nerve until the shaking reappears. This iterative procedure continues until the needle of the prior art is capable of generating perceptible muscle shocks at a current level of about 0.2 to 0.3 milliamper. At this point, the needle of the prior art is considered to be close enough to the reference nerve for administration of the anesthetic agent. The anesthetic agent is then delivered directly through the needle, while the needle continues to produce current pulses. The cessation of muscle shaking is typically considered to indicate satisfactory nerve localization. The electrolocation method of the prior art is intended to ensure the exact placement of a needle for the anesthetic delivery. However, the prior art device and the prior art method for electrolocation of a reference nerve have several drawbacks. For example, the electrolocation device of the prior art including the stimulator box, is a rather large, expensive and reusable piece of equipment that is not easily sterilized. Therefore, there are problems using the prior art electro location device in the sterile environment of an operating room. Typically it is necessary to employ two technicians to carry out this prior art method, namely, a first technician operating under sterile conditions and having the needle manipulated, and a second technician separated from the first technician and operating under non-sterile conditions. to decrease the level of the current incrementally. The use of two technicians necessarily requires rather high costs and requires considerable coordination and communication between the two technicians. Second, the electrolocation device of the prior art does not provide a definitive indication of when the needle has been properly positioned to inject the anesthetic. The attending physician must depend on his judgment and experience to determine when the needle is in the optimal position. Third, the considerable distance between the isolated needle and the conductive pad of the prior art requires the generation of a relatively high voltage to achieve the level of the desired current. A voltage of at least 25 volts ("V") is common in the electrolocation apparatus of the prior art. These relatively high voltage levels limit the use of the prior art apparatus. For example, high voltage levels can affect the operation of spacers and other implanted electronic devices. In this way, the electrolocalization device of the technique, in general, can not be used in patients with implanted electronics. In addition, relatively high energy creates the risk of arcing. Therefore, the electro-localization apparatus of the prior art can not be used in many surgical environments, such as those where oxygen is being used, due to the risk of fire or explosion. High current levels can also create the potential for tissue damage in proximity to the needle.

COMPENDIUM OF THE INVENTION The present invention is directed to an electro-localization apparatus for accurately and efficiently locating a nerve to which an anesthetic agent can be administered. The apparatus employs energy levels low enough to avoid potential tissue damage and to allow use of the apparatus in situations where a patient has an implanted electronic device. The apparatus is also small and economical enough to be manufactured for single use and can be made sterile enough to be used in the sterile field of an operating room. In addition, the device can be used by only one technician. As mentioned above, the voltage required for the electrolocation apparatus is a function of the distance between two conductors and the resistance to contact with the patient. To minimize the distance considerably, the present invention provides both conductors in the needle cannula. More particularly, the electro-location apparatus of the present invention can employ a needle assembly having a pair of conductors coaxially positioned. An internal conductor of the pair of coaxial conductors can be defined by the needle. The non-conductive liner or tube can then be mounted above the inner conductor and can be galvanized, coated, co-extruded or otherwise provided with an electrically conductive material that functions as the external conduit. A chamfer or chamfer can be defined at the distal end of the non-conductive tube. The bevel can be defined by a non-conductive adhesive at the distal end of the tube. The beveled adhesive works to hold the tube in place and also facilitates the entry of the needle assembly into the patient. The spacing between the conductors of the electrolocation device is defined by the distance from the distant edge of the bevel to the conductive liner, which is preferably lighter than 1.0 millimeter ("mm"). In view of this very small distance, a very low voltage can be used to generate the required current. It is believed by the present inventors that this aspect of the invention makes the present electro-localization apparatus suitable for use with patients having implanted electronic devices, such as spacers. In addition, the low energy level allows the present electro-localization apparatus to be used eventually in all environments of the operating rooms, including those where the prior art electrolocation apparatus has created the combustion potential. In addition, the low voltage allows a simple electronic circuit to be conveniently provided in a small package. As mentioned above, the prior art electrolocation device has required two technicians, namely a first technician to have the needle handled carefully, and a second technician to carefully vary the level of the current. The present electro-localization apparatus employs entirely a different structure that operates under entirely different principles and allows the use of an electro-localization device present by a single technician. The electrolocation device takes advantage of the determination that the threshold electrical parameter for generating a muscle jerk is measured more accurately in terms of the electric charge instead of the electric current. The electric charge is the product of current and time and the charge can be varied by changing either the current level or the duration of time. In a first preferred embodiment, the present electro-localization apparatus generates constant current pulses; however, the pulses in sequence alternate between a relatively long duration and a relatively short duration. In this way, the constant current pulses in sequence alternate between the relatively high load and a relatively low load. In a second modality, the electro-localization apparatus functions to alternatively supply relatively high current pulses (eg, 0.5 ph) to relatively low current pulses (eg, 0.1 to 0.2 mA). Each pulse can be of the same duration (eg, 0.1 to 0.2 millisecond ("S")) and the pulses can be generated at uniform intervals (eg, from 0.25 to 2.0 seconds). An approach for using the electro-localization device of the present invention may include pushing the needle toward the patient and toward the reference nerve. Relatively high charge impulses will generate muscle jerks at a distant site of the nerve after having penetrated the skin (e.g., when the tip of the needle is at a distance of approximately 1.0 centimeter from the reference nerve). The relatively low charge impulses, however, will not produce a sufficient load to generate muscle jerks at this initial distance. The pulses can be separated, for example, by approximately half a second (then "1/2" or "0.5" second (s)). Therefore, the doctor will initially observe the muscle jerks at intervals of approximately one second, coinciding with the high load impulses. As the needle moves toward the reference nerve, the physician may see a slight increase in the magnitude of the muscle jerks observed initially caused by the high load impulses. Simultaneously, the doctor will begin to observe small muscle jerks in response to the impulse of low load - lo ¬ which follows each high load impulse. In this way, using the example above, the physician will observe a large jolt in response to a high load impulse followed by 0.5 second later by a smaller jolt in response to a low load impulse followed then 0.5 second later by another jolt larger in response to a high load impulse. The jerks generated in response to the high load impulses will quickly reach the maximum such that further movement of the needle towards the reference nerve will not synificantly increase the magnitude or seriousness of the resultant jerks of the high load impulses. The jerks generated in response to low load impulses will gradually increase in magnitude and intensity as the needle continues to approach the reference nerve. These changes in the magnitude and intensity of the shakes of low load will be easily observable by the doctor who inserts the needle. As the tip of the needle approaches the reference nerve, the major and small shakes will become essentially indistinguishable, and the physician will only observe essentially identical muscle jerks at intervals of approximately 0.5 second or twice the interval initially observed. This will indicate to the physician that the needle tip is properly placed for the administration of the specified anesthetic. The anesthetic agent can then be pushed through the needle and into the reference nerve. The anesthetized nerve will then stop shaking, thus providing the physician with a clear indication that the reference nerve has been reached and that the anesthetic has made the intended effect. The physician can then simply activate a switch on the small control of the electro-localization device to terminate the flow of current to the needle. Although the present has been described primarily with the concept of generating alternative charge pulses in high and low sequence of sequences, it will be appreciated by one skilled in the art that the construction of the electrolocation device and the components described herein can be configured to produce a pattern. of repetition of graduated load impulses depending on the desired application. For example, depending on the anatomy of the region surrounding the nerve being sought, it can be shown beneficial to have a repetition pattern of gradual decrease in the charge impulse as it approaches the nerve instead of an alternate series of pulses of high level and low absolute load as it approaches the rib, ie the apparatus and the associated components can be configured in such a way that instead of supplying an alternative series of high and low level load pulses, it will supply a pattern of repetition of graduated load impulses with the graduation in each pattern declining from a load impulse to the selected maximum level up to a selected minimum level load impulse. In this way, for certain anatomies, the physician is provided with a larger scale of clinical observations regarding the nerve reaction, the load impulses, thus providing a more accurate knowledge for the physician of the location of the apparatus with respect to to the nerve. Other patterns are also possible.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of a bipolar electro-localization apparatus in accordance with the present invention. Figure 2 is a cross-sectional view of a needle in accordance with the present invention. Figure 3 is a functional diagram of a set of circuit components whose function is to produce appropriate load pulses through the needle of Figure 2, in accordance with the present invention.

Figure 4 illustrates an example of a combination of the operating circuit components within the blocks of Figure 3. Figure 5 is a graph showing a pulse generation pattern according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED MODALITY An electrolocation apparatus in accordance with the present invention is generally identified by the number 10 of Figure 1. The apparatus 10 includes a needle assembly 12, a stimulator 14 and a tube 16 for delivering a dose of the anesthetic through the assembly 12. of needle The needle assembly 12, as shown more clearly in Figure 2, includes an elongated needle cannula 20 having opposite and distant ends 22 and 24 and a lumen 26 extending continuously therebetween. The needle cannula 20 is formed of an electrically conductive material and preferably of stainless steel. The proximal proportions of the needle cannula 20 are mounted securely on the stimulator 14 with the proximal and distal ends of the needle cannula 20 remaining on opposite sides of the stimulator 14. The distal end 24 of the needle cannula 20 is bevelled to a point that facilitates the perforation of the tissue to have access to the reference nerve. The needle assembly 12 further includes a thin-walled tube 28 positioned coaxially above the cannula 20 of the needle. The tube 28 has opposed and proximal ends 30 and 32 respectively and is formed of a non-conductive material such as polyimide. The proximal end 30 of the tube 28 is placed in the stimulator 14 as further explained herein. The distal end 32 of the tube 28 is approximately spaced from the beveled distal end 24 of the needle cannula 20. The tube 28 is dimensioned to be tightly coupled against the outer cylindrical surface of the cannula 20 of the needle. However, secure retention of the tube 28 in the cannula 20 of the needle is achieved by non-conductive epoxy 34 or other adhesive extending between the distal end 32 of the plastic tube 28 and the outer cylindrical surface of the needle cannula 20 . Epoxy 34 is chamfered to facilitate entry of needle assembly 12 into a patient. The chamfering preferably defines a length of approximately 1.0 millimeter. The tube 28 includes a conductive layer 36 on its external cylindrical surface which can be applied by electroplating or coating. The layer 36 is preferably gold and extends continuously from the proximal end 30 to the distal end 32 of the tube 28, to a thickness of approximately 550 angstroms. The needle assembly 12 functions effectively as a pair of coaxial conductors as explained hereinabove. In particular, the stainless steel needle cannula 20 functions as an internal conductor, while the gold layer 36 in the tube 28 functions as an external conductor. The tube 28 defines a non-conductive insulating material that separates the inner and outer conductors defined respectively by the stainless steel needle cannula 20 and the gold layer 36. As mentioned above, the stainless steel needle cannula 12 extends continuously through the stimulator 14 such that the proximal end 22 of the needle cannula is placed on one side of the stimulator 14, while the distant end 24 is Place on the opposite side of it. The proximal end 30 of the plastic tube 28 is placed inside the stimulator 14. As a result, both the stainless steel needle cannula 12 and the gold layer 36 are exposed for electrical contact within the stimulator 14. The stimulator 14 includes a housing 38 generally rectangular which may have length and width dimensions, for example, of about 19.84 millimeters and a thickness dimension, for example, of about 9.57 millimeters. The housing 38 can be formed of two halves 40 and 42 of the molded thermoplastic housing which are welded or adhered to one another. The upper and lower walls respectively may include concave regions to facilitate holding by the digits of the hand. The accommodation 38 carries out multiple functions, including providing structural support for the needle assembly 12, providing a convenient hold for handling the needle assembly 12 and secure closing of the electronic components of the electro-location apparatus 10. The electronic circuit of the stimulator 14 includes an on / off switch 48 and a light-emitting diode (LED) 50 both of which are accessible and / or visible from the outside of the housing 38. The on / off switch 48 operates to completing the circuit between a battery and other portions of the circuit, as will be described further below, and optionally to allow switching between high and low load levels, the LED 50 operates to generate a light pulse with each energy pulse electrical so that the technician or attending physician can compare the energy impulses with the muscular jerks in the patient. Figure 3 is representative of a circuit that can be used in simulator 14. As will be appreciated by an expert, one way to implement this circuit is to digitize it using CMOS technology as active elements. Other implementations, such as customary integrated circuits ("ICs") are also possible. Here, the on / off switch 48 is connected to a 3 volt lithium cell battery 52. In the disconnected state, the quiescent current is less than 1 icroamper ("uA") providing a battery life in excess of eight years, and thus ensuring adequate shelf life for the electrolocation apparatus 10. In the connected state, the oscillator and counter described below are capacitated and the battery will operate the stimulator 14 for approximately 100 hours. The modulation of the time duration pulse is achieved by a counter 54. Using the outputs of the counter 54 it is possible to generate a pulse as short as 122uS. Since the outputs of the counter 54 are periodic signals, the time selection gate network 56 selects only one period of the output signal and applies the same to the network 58 of the current source. In the embodiment shown in Figure 3, the network 56 may alternatively allow either a low charge pulse or a high charge impulse. As shown schematically in Figure 5, the stimulator 14 functions to alternatively generate pulses of short and long duration. All the impulses will be of a constant current but they will be of different durations. For example, stimulator 14 can operate to generate a pulse at a current level of 0.2mA for 122uS to produce a relatively low load of 24.4 nanocoulombs ("nC") followed by a current pulse of 0.2mA for approximately 488uS to produce a relatively high load of 97nC. It will be understood by a person skilled in the art that depending on the components selected to generate the pulses, the duration of the pulses may vary within a time scale, for example, of about +/- 20 percent of the durations that manifest themselves at the moment. Other pulses of constant current pairs for different durations can be used to produce low and high alternative loads. The circuit of Figure 3 is also designed to optionally provide constant education impulses with modulation of the amplitude of the current. For example, the 0.2mA low current pulse can be generated for 122uS to produce a relatively low load of 24.4nC and can be followed by a high current pulse of 0.8mA for 122uS in order to produce a relatively high load of 97nC . It will be noted that the loads produced by the option of the current level modulation are equal to the loads produced by the modulation option of time duration. Figure 3 is a functional diagram of a set of circuit components in the stimulator 14 that function to produce appropriate load pulses through the bipolar needle 12, and Figure 4 illustrates an example of a combination of operating circuit components within the blocks of Figure 3. As seen in Figure 3, an on / off control 51 operated by the switch 48 has an output that activates an oscillator 53 to activate the counter 54 and another output that capacites and incapacitates the counter 54. A third output is supplied to a control circuit 55 that receives an output from the counter 54 and activates a constant current sink 58 coupled with an electrode 20 or 36 of the bipolar 12 needle. The indicator circuit 57 that drives the LED 50 receives the inputs of the oscillator 53, the counter 54 and the current source V +, which through a load limiter 59 is coupled to another electrode (36 or 20) of the bipolar needle 12 . The time and magnitude of the charge pulses are modulated by a time selection gate component 56 which is coupled with the control circuit 55. Returning to the details of the circuit of Figure 4, the on / off control 51 may consist of the on / off switch 48 which couples the voltage V + of the battery 52 to a circuit including a vascular circuit A1B and an RC combination ( Rl, C3). When the apparatus 10 is to be used, the switch 48 is placed in the connected position and remains connected to avoid any of the abnormal transient currents in the needle. The tilting circuit A1B controls the time of the oscillator 53 which may comprise a Schimit A3A trip and capacitance and disable the counter 54 which may be in the form of a 12-bit counter A2 and the control circuit 55 sink, may comprise a vasculatory circuit A1A. When A and B is connected, the output line 12 is low or zero, so that the readjustment of the counter A2 is off and therefore, it is free to count, and the readjustment of A1A is disconnected so that it is free to change state. Concomitantly, the output line 13 of A1A is high or positive so that the oscillator A3A operates, v, gr, at 4,096 ilohertz ("kHz") to cause the counter A2 to count, after which the pin 1 of A2 is caused to change state every half second and pin 15 goes to the positive state every half second. In this way the pin 15 changes state to twice the speed of the pin 1. When A1B is disconnected, line 13 goes to the low state stopping the output of A3A and line 12 goes to the raised state by readjusting A2 and A1A. When the pin 15 of A2 goes to the positive state, the clock signal to the A1A causes the output line 1 to go to the high state by means of the voltage V +, supplying the base current to the transistor Q3, through the resistors R4 and R5. Q3 is caused in this way to drive by closing a current path so that current flows through needle 12 from battery V +, through capacitor C4 and through resistor R7 to ground. If the voltage in R7 goes to more than 0.55 V, the base of transistor Q2 will be driven through resistor R6 to connect Q2 which in turn decreases the base current to Q3, thereby maintaining the voltage across R7. at 0.55 V. Therefore, the current through the needle A2 remains essentially constant. In the event of a short circuit or failure of the needle current path, capacitor C4 acts to charge the limiter by charging to a preselected maximum load and limiting the current level.

The timing and shape of the current pulses is determined through the use of the time selection gate component 56 comprising three gates A3B, A3C and A3D which receive the inputs of the oscillator A3A and the counter A2 and provide an output to the Vascular circuit A1A of the dissipation control circuit 55. The gate A3B controls the short pulses shown in the timing diagram of Figure 5. It will be until the input pin 10 to the counter A2 works on the negative pulses so that when the output of A3A on the pin 3 goes to the state negative, the output pin of A2 goes to the positive state driving A1A to connect the current through the needle path as explained just above. The output on the pin 3 of A3A is also supplied to the input pin 6 of the gate A3B, the other input pin 5 from which the pin 1 of A2 receives the output. If the signal on the pin 1 and in turn on the pin 5 is raised, A3B can operate when the pin 6 goes towards the raised state. If pin 1 is low or zero, then pin 5 is low and A3B can not work. The operation of A3B can be used to control the alternation of short and long charge pulses. When pin 1 is in an elevated state, short pulses will occur.

More particularly, when the A3A pin 3 goes to the low state, the counter 54 will go to its next state. The pin 15 goes to the raised state so that the current begins to flow through the needle and the pin 1 goes to the raised state so that the pin 5 of A3B is in the raised state, while the pin 6 is in the raised state. low zero state together with pin 3. The output of A3B on pin 4 will be 1, it is the input on pin 13 to gate A3D. With an elevated entry in the pin 12, the output of the gate A3D in the pin 11 will be zero. Now, when the oscillator A3A sends a high state on the pin 3, the counter A2 does not change its state, but the pins 5 and 6 of A3B will both be in the raised state so that the output on the pin 4 will go to zero causing the entry to pin 13 to be zero. If the entry in the pin 12 is still raised, the output of A3D in the pin 11 goes towards the raised state. The high signal on the pin 11 is coupled through the capacitor C2 with the readjustment of the vascular circuit ALA causing its output on the pin 1 to go to zero, disconnecting the constant current dissipation 58 and the current through the needle 12. A short current pulse will then have to occur for a duration of 122uS.

To produce longer impulses, gate A3C is used and gate A3B becomes disabled. Since A3B can only function when the pin 1 of A2 is in the raised state, the signal on pin 1 is caused to go to the low state by disconnecting A3B. In this condition, the readjustment of the AlA function is controlled only by A3C. The output of A3C can be controlled according to the pulse ratio chart shown adjacent to A3C in Figure 4. By appropriately connecting the A (8) and B (9) inputs of A3C with the enumerated combination of pins of the counter A2, the time relationships between the short and prolonged pulses shown in the left-hand column of the frame can be achieved, thereby obtaining pulse width modulation of the load impulses. To achieve pulse amplitude modulation, inputs A and B to A3C can both connect to pin 10 of A2 to produce a pulse time ratio of 1 to 1, with pulses of 122 uS. An RIO resistor in the constant current dissipation 58 is connected in the circuit between the pin 1 of A2 and the emitter of the transistor Q3, closing a switch SW1. When pin 1 is in high condition, current flows through RIO and resistance R7 to ground. The current in the path of the current through the needle 12 therefore decreases since the voltage across R7 remains constant and the current through R7 is constituted by two sources. Consequently, the magnitude of the current pulse through the needle 12 becomes a comparatively low current pulse. When the pin 1 of A2 is in the low state, that is, it is going to ground, RIO is configured in parallel with R7 with respect to ground, so that the resistance through R7 and RIO decreases with respect to the current path . Since the 0.55V volt is maintained at its junction point, as explained above, a greater amount of current is needed through both resistors. Therefore, the magnitude of the current pulse through the needle 12 is increased resulting in a comparatively high current pulse. Therefore, pulse amplitude modulation can be achieved within this circuit. If desired, both pulse width modulation and pulse amplitude can be produced by selecting pulse ratios in the pulse ratio frame and switching the RIO resistor to the circuit. Finally, the indicator circuit 57 is configured to be activated when an impulse has occurred, independently of the modulation, and to produce a simple connection or disconnection indication. In this way, the LED 50 will turn on CONNECT NDOSE upon occurrence of a charging pulse or the buzzer 60 will produce a sound in accordance with the synchronization and change of state of the outputs on the pin 3 of A3A and the pin 15 of A2. As mentioned above, the proximal end 22 of the stainless steel needle cannula 20 projects entirely through the housing 38 of the stimulator 14. As shown in Figure 1, the proximal end 22 of the cannula 20 of The stainless steel needle is connected to a flexible pipe 16 which extends to a plug that is connectable with a syringe to deliver a selected dose of anesthetic. In an alternative embodiment, the proximal end 22 of the stainless steel needle cannula 20 can be mounted directly on a needle plug that is connectable with a syringe to deliver a selected dose of the anesthetic. During use, an anesthesiologist or nurse anesthetist inserts the beveled distant tip 24 of the stainless steel needle 20 in a patient and into the reference nerve. No wires or a conductive pad are used. In the constant current mode described herein, the switch 48 on the stimulator 14 is then operated to generate the constant low current pulses of electrical energy. The proper functioning of the electro-localization device 10 is confirmed by the turning on of the LED 50 which generates a light pulse or simultaneously with each respective energy pulse. The respective energy pulses are generated at 1/2 second intervals. The high load impulses of 0.2mA during 488uS will generate a load of 97nC. The low charge impulses are of the same current of 0.2mA, but they last only 122uS and will generate a charge of only 24.4nC. Higher load impulses of 97nC will be sufficient to generate observable muscle jerks in an essentially superficial location after the skin has been penetrated by gold layer 34, while lower loads, 24.4nC impulses will not be sufficient to generate initially no observable muscle jerks at this distance from the nerve. In this way, the anesthesiologist or nurse anesthetist will observe the muscular jerks at intervals of approximately one second coinciding with the high load impulses. The needle assembly 12 is pushed further towards the reference nerve. This advance of the needle assembly 12 will show a gradual increase in the magnitude of the jerks that occur at one second intervals. Nevertheless, these shakes in response to the high load will soon reach the maximum. The anesthesiologist or nurse will then observe muscle shaking of small magnitude between shakes of larger magnitude. Therefore, small and large alternative shakes of magnitude can easily be observed. As the needle assembly 12 is further advanced towards the patient, muscle shaking of small magnitude will increase in magnitude to approximate the magnitude of the maximal large magnitude muscle shaking generated by the high load impulses. At the distal tip 24 of the stainless steel needle cannula 20 near the reference nerve, the muscle jerks generated in response to the low load impulses will not be essentially distinguishable from the muscle jerks generated in response to the load energy impulses. elevated Therefore, the anesthesiologist or nurse will observe almost identical muscle jerks at 0.5 second intervals. This readily observable response will indicate to the anesthesiologist or nurse that the beveled distant tip of the needle cannula 20 is sufficiently close to the reference nerve for administration of the anesthetic. The anesthetic is supplied in the conventional manner by driving the hypodermic syringe communicating with the proximal end 22 of the stainless steel needle cannula 20. The exact procedure can be carried out by the alternative mode that modulates the level of the current. Although the invention has been described with respect to a preferred embodiment, it is clear that various changes can be made without departing from the scope of the invention as defined by the appended claims. For example, the stimulator may have switching mechanisms for changing the level of the current or the pulse width to vary the respective levels of the loads delivered to the patient. In addition, other impulse generation indications may be provided including an audible buzzer instead of or in addition to the LED described above.

Claims

CLAIMS:

1. An integral electro-localization apparatus comprising: an electrically conductive needle cannula having a proximal end, a distal end and a hollow perforation therethrough; a non-conductive tube having a proximal end, a distal end and an open passage therethrough, the tube is mounted above the needle cannula so that the distal end of the non-conductive tube is close to the distal end of the needle cannula; a conductive layer having a distal end in the non-conductive tube whereby the needle cannula and the conductive layer respectively define first and second electrodes separated coaxially from one another by the non-conductive tube; a handle fixedly fixed to the needle cannula for manipulating the apparatus, the handle comprises a casing; and an electrical stimulus generating circuit within the envelope and electrically communicating with the first conductor and the second conductor, the stimulus generator being able to apply pre-selected loads to the conductors so that when the needle is placed in a tissue of the In the patient, the charges are sufficient to induce a preselected current between the distal end of the conductive layer and the distal end of the needle cannula through the patient's tissue, this current being sufficient to induce a shaking response in the patient. The apparatus according to claim 1, wherein the distance between the distal end of the cannula of the conductive needle and the distal end of the conductive layer is approximately 1.0 millimeter. 3. The electrolocation apparatus according to claim 1, wherein the electroconductive cannula projects proximal beyond the handle and includes a connector for connecting a drug delivery device to the perforation of the electroconductive needle. 4. The electro-location apparatus according to claim 3, wherein the connector further includes a flexible tube. The electro-localization apparatus according to claim 1, wherein the stimulus generating circuit includes an on / off switch accessible by the pressure of the physician's finger. 6. The electro-location location apparatus of claim 1, wherein the circuit provides the preselected load pulses in pre-selected repeatable patterns. 7. The electro-location apparatus according to claim 6, wherein the preselected patterns include different load current pulses. The electro-location apparatus according to claim 7, wherein the charge pulses are controlled by the circuit to comprise preselected constant currents. 9. The electro-location apparatus according to claim 8 wherein the preselected constant currents are between about 0.1 milliamper of about 0.8 milliamper. The electro-localization apparatus according to claim 6, wherein the preselected patterns include pulses of different durations. The electro-location apparatus according to claim 10, wherein the pulse durations are between about 100 microseconds and 1,000 microseconds. The electro-localization apparatus according to claim 6, wherein the preselected charge pulse pattern includes preselected time intervals between the pulses. The electro-localization apparatus according to claim 12, wherein the preselected time intervals are between about 0.25 second to about 2.0 seconds. 14. The electro-location apparatus according to claim 6, wherein the circuit further comprises an indication of the charge pulse. The electro-localization apparatus according to claim 14, wherein the indication further comprises an audible sound to the physician using that apparatus. The electro-localization apparatus according to claim 14, wherein the indication further comprises an emission of visible light to a physician using the apparatus.