Operating Manual
38 Pages
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Page 1
Neurosign 100 Operating Manual 9883-23-P16
Neurosign 100
Table of Contents______________________________ Page Number Section 1:
Guarantee
1
Section 2:
Description
2
Section 3:
Warnings and Precautions
3
Section 4:
Front Panel Layout
5
Section 5:
Rear Panel Layout
9
Section 6:
Pre-Amplifier Pod
11
Section 7:
Preparations for Use
12
Section 8:
Sensing Electrodes - Electrode Placement Diagrams
13 14
Section 9:
Stimulator Probe Pod
16
Section 10:
Stimulation Probes
17
Neurosign 100
Page Number Section 11:
Using the Neurosign 100 - Interpreting Audio Signals -Interpreting Neurosign Sounds - Suggested Stimulation Current Settings - Problem Solving Checklist
19 20 21
Section 12:
Electrocautery Mute
23
Section 13:
Maintenance and Servicing - Voltage Selection and Fuses - User Maintenance - Preventative Maintenance - Cleaning and Sterilising - Single- use Product Disposal - Servicing
24 24 24 25 25 25 26
Section 14:
Accessories - Impedance Meter - Dual Pod Switch - Laryngeal Electrode - Needle Electrodes - Probes - Carrying Case - Equipment Trolley
27 27 27 28 29 30 33 33
Section 15:
Specifications
34
21 22
©1999, The Magstim company Limited, Spring Gardens, Whitland, Carmarthemshire, Wales, U.K. All rights reserved. No part of this manual may be reproduced without the written permission of The Magstim Company Limited.
Neurosign 100
SECTION 1:
GUARANTEE_____________________________
Equipment manufactured by The Magstim Company Limited (“The Company”) is fully guaranteed covering materials and workmanship for a period of one year from the date of shipment, excepting those items detailed below. The Company reserves the right to perform guaranteed services in its factory, at an authorised repair station, or at the customer’s installation. Reusable Stimulating Probes are guaranteed covering materials and workmanship for a period of 3 months from the date of shipment. Reusable needle electrodes are guaranteed covering materials and workmanship for a period of 1 month from the date of shipment. Single use electrodes are guaranteed to be free of defect upon use. Sterilisation is guaranteed subject to the packaging being undamaged and the product being within the serviceable life as stated by the sterilisation date shown on the label. The Company’s obligations under this guarantee are limited to the repair or replacement of any defective parts without charge if the defects occur during normal service. Claims for damages during shipment must be filed promptly with the transportation company. All correspondence concerning the equipment must specify both model name and/or number and serial number, as it appears on the invoice. Improper use, mishand ling, tampering with, or operation of the equipment otherwise than in accordance with this Operating Manual will void this guarantee and release the Company from any further guarantee obligations. The Company will only accept responsibility for the safety, reliability and performance of the equipment if: ?
modifications or repairs are carried out by persons authorised by the Company, and
?
the electrical installation of the room in which the equipment is used complies with local regulations, and
?
the equipment is used in accordance with the operating instructions.
No statement in this Guarantee limits the statutory rights of a purchaser of this equipment in the United Kingdom.
The Magstim Company Ltd 9883-23-P16
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Neurosign 100
SECTION 2:
DESCRIPTION_______________________
The NEUROSIGN 100 Nerve Monitor has been designed to meet the needs of operating theatre staff by continuously monitoring motor neural pathways which are at risk during surgical procedures. The instrument gives an audible interpretation of muscle activity, which is sensed by needle electrodes placed into the relevant muscles controlled by those nerves to be monitored. Note: Muscle contractions are only possible if limited or no neuromuscular block is used. The Neurosign 100 cannot be used in instances where the patient is paralysed. The train of four stimulator should not be used as proof that any blockade has dissipated; the Neurosign 100 can detect EMG well below the threshold of visible muscle movement. Activity near the nerve at risk will cause associated motor units to contract and the instrument will emit a distinctive sound, the level of which is proportional to the stimulus applied to the nerve. The nerve may also be directly stimulated using a small current via a Stimulation Probe. There are a number of outputs available on the rear of the machine, to enable an EMG instrument, oscilloscope, chart recorder or computer to be connected. Dedicated software is available to enable an operation to be data-logged and the waveforms analysed. This instrument is supplied with a Bipolar Stimulation Probe, Pre-Amplifier Pod, Stimulator Probe Pod, Needle Electrodes, Mute Sensor and the main signal processing unit. For details on the availability of probe types and recording electrodes and their purchase, please see the Accessories Section 14 on page 25 and contact either The Magstim Company Limited (for the address please see Section 13), or your local distributor if outside the UK.
The Magstim Company Ltd 9883-23-P16
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Neurosign 100
SECTION 3:
WARNINGS AND PRECAUTIONS______
ATTENTION!_____________________________________________________ The Neurosign 100 is designed for use during surgical procedures and must only be used by qualified personnel who have carefully studied this Operating Manual and read this section. This instrument is designed as an aid to surgeons in the identification and monitoring of motor nerves at risk during surgery. It is not a replacement for experience in surgical decision-making. Before use, ensure that the Voltage voltage selector is set correctly. Only use fuses of the correct type and rating (see Section 13). Serious damage may occur and a safety hazard exist if incorrect fuses are used, or the wrong voltage is selected. Do not twist the preamplifier cable around the pod when not in use, as this may fracture the internal cores of the cable. Coil the cable and use the retaining straps supplied with the pod Do not drop the instrument, the Stimulator Pod or the Pre-Amplifier Pod, or otherwise permit any physical damage to occur. Do not permit any liquid to be spilt such that it may enter the casing , via the ventilation slots on the side or through the bottom of the casing. Do not insert objects into holes or slots in the casing for cleaning purposes, as this may cause damage. Do not obstruct the ventilation slots. Use a lint- free cloth damped with alcohol to clean the instrument, the Stimulator Pod and the Pre-Amplifier Pod. Store the instrument in a dry atmosphere within the temperature range of 5°C - 30°C. The reusable Stimulation Probe(s) and the reusable Needle Electrodes (if specifically selected) obtained from The Magstim Company Limited, may be autoclaved (maximum temperature 140°C). Single use electrodes are supplied sterile. If there are any signs of damage to the packaging, the electrodes should be discarded. No attempt should be made to re-sterilise either used electrodes, or electrodes found to be in damaged packing. Needle electrodes should be removed from the patient by holding the heatshrink covering the end of the needle and pulling out the needle at the same angle as it was inserted. The needles should not be removed by pulling the connecting lead. This could cause damage and result in reduced performance or product life expectancy. High levels of RF, usually generated by electrocautery equipment, may interfere with the operation of the Mute Sensor if this device is not connected to the electrocautery cable. Do not connect the Mute Sensor to the Neurosign 100 if the clamp is not to be attached to the electrocautery cable, or spurious muting of the Neurosign 100 may occur. Under extreme conditions, it may be possible that the mute sensor or the pre-amplifier may be affected by RF, in which case a few segments of the bargraph may light. In this case, the offending piece of equipment should be identified and The Magstim Company Ltd 9883-23-P16
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Neurosign 100
replaced; alternatively, an improvement may be achieved by moving the preamplifier pod, stimulating pod, associated cables, or the position of the Mute Sensor. Any attempt to remove the securing screws will invalidate the guarantee. There are no user-serviceable parts inside. There are high voltages present and there is the danger of electric shock if the casing is opened. The use of this instrument other than as described in Section 11 may reduce the level of protection provided by the equipment. Contact The Magstim Company Limited prior to uses not described in the brochure. Before using the instrument, check that there are no signs of physical damage to either the main unit, the Pre-Amplifier Pod, the Stimulation Probe or the needle electrodes. The Stimulation Probe must be inspected after autoclaving for any signs of physical damage or deterioration and the tip(s) checked. They should be straight, parallel and rounded. Check the needle electrodes for physical damage. Replace as necessary. The use of needle electrodes when used near, or in conjunction with, electrosurgical equipment has the potential, under certain fault conditions of the electrosurgical equipment, to give rise to burns at the point of contact between the needle electrodes and tissue. It is therefore strongly recommended that the instructions for preparation and use relating to the electrosurgical equipment are strictly adhered to, and that the equipment itself is regularly checked for electrical safety and correct operation, particularly in relation to any automatic impedance measuring or current sensing safety devices. Only equipment which has an automatic cut-out feature and measures the return pad impedance should be used in conjunction with the Neurosign 100. The particular conditions which could give rise to such a potential risk are concerned with the electrosurgical unit’s return pad, often attached to the patient’s thigh. Thorough preparation of the area to ensure a reliable contact with low impedance is vital for patient safety. Because the risk is related to the return pad and its impedance with regard to the body, the risk is considered to lie exclusively with the use of monopolar electrosurgery. Bipolar electrosurgery, as its name suggests, uses its own active and return electrodes in the same forceps. It should therefore be considered whether monopolar electrosurgery is necessary when using nerve monitoring equipment. In order to reduce any possible induced current in the needle electrode leads from stray RF emitted by the electrosurgical unit, the electrode leads should be kept as far as possible from the unit. In practice, this means that the electrosurgical unit should not be positioned near the head of the patient. Cables from the electrosurgical unit, both active and return, should also be kept as far as possible from the electrode leads, especially whilst monopolar diathermy is being used. Consideration should therefore be given, prior to the surgery, to the balancing of the risks of the surgery to the nerve being monitored, and the possible risk of burns caused by any interaction between the electrosurgical machine and the Neurosign 100.
The Magstim Company Ltd 9883-23-P16
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Neurosign 100
SECTION 4:
FRONT PANEL LAYOUT____________
FREQUENCY This switch has two positions, labelled 30Hz and 3Hz. It is recommended that no neuromuscular block is used other than for intubating the patient and that a suitable anaesthetic protocol is implemented so as not to impede muscle movement, in which case the frequency switch should be set to 30Hz. The advantages of this are that because of the higher frequency, the surgeon will need to stimulate the tissue for less time before correctly interpreting a positive response, and also that the CURRENT CONFIRM circuitry will be able to check that the correct current has passed more quickly. A neuromuscular block will reduce or eliminate the responses from mechanical distortion of the nerve, which is the normal early warning to the surgeon. If a neuromuscular block has to be used throughout the operation, this switch should be set to 3Hz. At this frequenc y, the stimulation will overcome the block (as long as it is not too deep), although it may take 1-2 seconds to confirm that the correct current has been passed. Please note that a high dosage of neuromuscular block must be avoided, unless the patient needs to be paralysed for clinical reasons, as this will significantly reduce the compound muscle action potential. PROBE The Stimulator Probe Pod cable should be connected to the socket marked PROBE, unless the stimulator probe is not required for the procedure, in which case it may be left unconnected. It is a push fit in the socket and clicks home. It is removed by pulling the plug from the socket; do not pull the cable, or damage may occur. Always remove by holding the
connector body - do not remove using the cable or by twisting the connector sideways from the housing.
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STIMULATOR CURRENT This control sets the current which flows through the Stimulation Probe and so through the tissue touched by the Probe. It can be adjusted from 0.05mA (50µA) to 5mA and consists of a narrow negative going pulse of 200? s at a frequency of either 30Hz or 3Hz, depending on the FREQUENCY switch setting. Note that most of the travel of this control is at the lower levels of current, below 1mA; the higher levels are used for stimulating through tumour mass and bone. Currents in excess of 1mA should not be used directly on the exposed nerve in surgery involving the cranial nerves. Although the minimum current setting varies dependent on the specific surgical procedure, and on the individual patient’s physiology, the current ma y be set to 0.2mA as a basic control value, but the user should be prepared to alter this in the light of experience. There is a simple table suggesting suitable stimulation currents on page 22. Further information on current settings for specific surgical procedures is outlined in the Procedure Sheets which are available from the Company or Distributor. In order to enable the surgeon to know that the set stimulation current has been passed through the Probe, an indicator labelled CURRENT CONFIRM is provided. This indicator will light when the set current is passed; therefore it will only light when the Probe is in good contact with tissue. It provides positive proof to the surgeon that the correct current has been passed, and also that the Stimulation Probe is functioning. When the CURRENT CONFIRM indicator is lit, the Stimulation Current Record on the rear panel provides a voltage proportional to the current set on the front panel - this, in conjunction with the EMG Outputs, may be used for dataSTIMULATOR logging. (See Section 14 for details of the computer software available). TESTING The CURRENT CONFIRM indicator also provides a warning if the Stimulation Probe is faulty. During the operation, if the indicator stays on permanently check that the tips of the Probe are dry, clean and are not touching, and that there is no liquid material bridging them which could create an electrical path for current to flow. If cleaning the tips does not cure the problem, unplug the Probe. If the indicator light turns off, the Probe is faulty. If the indicator does not light, the Probe may be checked by shorting the Probe tips together, either physically or by using a damp cloth. It may be difficult to obtain a result at the highest current setting, so it is best to check the functionality of the Probe at the lowest current setting (0.05mA). If the indicator lights, the Probe is working. Ensure that both electrodes come into contact with tissue, not just the side of one electrode. If the indicator does not light, unplug the Probe and try ano ther; if this Probe works, the first is faulty, but if this still does not work, the fault is likely to be in the Stimulation Pod. Reasonable care of all items will ensure a long life, but the components should be treated appropriately during the sterilisation and storage phases of the equipment’s life.
The Magstim Company Ltd 9883-23-P16
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CHANNELS 1& 2 These switches control each channel. When the indicator is orange, the channel is OFF; when the indicator is green, the channel is ON. The bargraph for each channel will light showing the level of EMG activity. Each bargraph is calibrated from 30? V to 20mV peak-to-peak. In practice, with the electrodes correctly placed, no part of the bargraph should light unless the muscle is stimulated, either spontaneously or by the surgeon, either through manipulation or electrical stimulation of the nerve. When EMG is detected, the bargraphs rise; when the EMG ceases, the bargraphs fall. However, in order to allow the user to determine the level of the response, or to identify the channel, the top segment of the EMG response remains lit for a period of several seconds before decaying. When the unit is first switched on, the bargraphs light and a beep is heard. This allows the user to see that all the segments are working correctly. ELECTRODE WARNING The Neurosign 100 contains circuitry to detect the level of artifact present at the output. Experience has shown that where the electrodes are poorly placed, perhaps in fatty tissue rather than muscle, or the incorrect electrodes have been used, then a large amount of artifact may be present and can degrade the quality of the output available; this possibility can be avoided by using the Impedance Meter, described in Section 14. The Neurosign 100 detects this artifact, and sounds a warning in the following manner. For the purposes of this manual, artifact can be defined as unwanted voltages present in the body or in the electrical environment of the Operating Theatre. Each channel is monitored independently. Artifact must be present continuously for a period of 20 seconds, when the ELECTRODE WARNING light will illuminate and a short beep will repeat every 8 seconds until the problem is cleared. Should the artifact fall below a certain level, even for a moment, the warning circuitry will reset and the process will start again. There are three reasons why the ELECTRODE WARNING indicator may light; ?
continuous monopolar electrocautery is being used for a period greater than 20 seconds, injecting artifact into the patient. The ELECTRODE WARNING indicator will extinguish as soon as the electrocautery stops
?
the electrodes are poorly positioned or have become detached; the use of the Impedance Meter will prevent the former, whilst proper taping of the electrode leads as shown in the diagrams on pages 13 and 14 will reduce the risk of the latter
?
there is continuous EMG activity for more than 20 seconds; such continuous EMG activity is not usually a good sign, in that it represents continual irritation of the nerve.
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When the indicator sounds, the electrodes should be checked at the earliest convenient point in the surgical procedure, if possible. Experience has shown that correctly placed electrodes of the appropriate type will not give problems. Care should be taken during placement (see Section 8) and it should be remembered that strong muscle contractions could easily disturb the electrodes. The electrodes should be securely fixed to the patient as well as properly located and inserted. VOLUME This knob controls the volume of the sound available from the speaker, but does not affect the bargraph displays or the BNC outputs available at the rear of the machine. The instrument utilises a compression technique so that small signals are amplified more than large signals. This improves the sensitivity of the instrument at low signal inputs, whilst still giving powerful warning of very high input le vels, occasioned by either direct stimulation or mechanical distortion of the nerve. The volume control cannot be set to zero; this is a safety feature in case the control is accidentally set to the minimum and the surgeon is not aware of the fact. CHANNEL IDENT In most circumstances, the surgeon will find it desirable to monitor two sets of muscles together. If it is important however, to be able to differentiate between the two nerve branches being monitored, the CHANNEL IDENT switch should be set ON. This introduces a different texture to the sound output for each channel. This difference is only applied to the speaker; the outputs available for connection to external devices do not include this Channel Identification colouration.
The Magstim Company Ltd 9883-23-P16
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Neurosign 100
SECTION 5: REAR PANEL LAYOUT_______________
MAINS The standard IEC power lead should be connected before the unit is CONNECTOR switched on. The unit is OFF when the switch is at the 0 position, and ON when at the 1 position. There are two fuses, rated at T500mA for 100-120V operation, or T250mA for 230-240V operation, next to the power lead connector. The fuses may be checked or replaced by removing the fuseholder cover. This cover also provides access to the voltage selector. Although it is unlikely that this will need to be changed, unless the instrument is shipped to another count ry, the mains voltage may be chosen by rotating the voltage selector and replacing the cover. A legend displays the voltage selected when the fuse cover is replaced. Do not select the wrong voltage, or replace fuses with those of a different rating, as severe damage may occur. EMG OUTPUTS These outputs come after 10kHz filters but before the signal conditioning necessary for the audio section, including the CHANNEL IDENT feature, and so may be directly connected to an EMG recording instrument or a computer and the waveforms captured and printed if required. The signal amplifiers have a gain of 500 and an output in the range 15mV to 10V peakto-peak. TRIGGER This TTL compatible output allows an oscilloscope, external chart recorder OUTPUT or monitor to be synchronised to the unit in order to obtain waveforms or hard copies. This facility may be used together with an EMG instrument. Using the Trigger Output and the appropriate hardware and software, the EMG Output can be captured by a computer. The Company distributes a dedicated package for this purpose (see Section 14).
The Magstim Company Ltd 9883-23-P16
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MUTE SENSOR A Mute Sensor can be used with the Neurosign 100 to cut out the sound output during electrocautery. The lead from the sensor should be attached to the Mute Sensor socket. The sensor itself should be clipped to the monopolar electrocautery cable near the diathermy machine. There is no adjustment available for the mute. If the mute is not required, do not connect the sensor and the Neurosign will operate normally, but do not attach the sensor and leave it lying unconnected to the electrocautery cable since it will detect spurious signals and may cause the Neurosign 100 to cut out randomly. Note that the bargraphs and EMG outputs are not affected by the mute, and they will show a high level of artifact during ele ctrocautery. STIMULATION This output may be used to log the Stimulation Probe current setting with CURRENT respect to time, in conjunction with the Trigger and EMG Outputs. It RECORD provides a voltage proportional to the Stimulation Probe current set on the front panel; however, the actual current flowing through tissue is affected by the quality of the contact between the Probe and tissue. The voltage at the Stimulation Current Record Output is only present when the CURRENT CONFIRM indicator is lit; hence its value for data- logging. This output must not be confused with the Stimulation Probe; the Stimulation Current Record Output on the rear panel is not on the isolated side of the electronics, and must on no account be connected to the patient. HEADPHONES The Headphone connector will accept any 3.5mm stereo jack plug, and headphones with an impedance of between 20 and 100 ohms. Most lightweight headphones have an impedance of 32 ohms. The volume of the headphones is controlled by the thumbwheel knob on the rear panel; however, this control operates after the main volume control on the front panel, so both must be operated in order for the headphone output to function. The output from the headphones is in mono, even when both channels are used, so that information is not lost due to any hearing difficulties of individual surgeons. When using headphones, the mute will be found to be only partially effective, and some noise from electrocautery may be heard. No sound will be heard from the Neurosign 100 itself. PRE-AMP POD The cable from the Pre-Amplifier Pod is plugged into the PRE-AMP POD INPUT INPUT socket. The connector should be located in its socket and pushed firmly home. To unplug the cable, depress the tab and then remove the plug. Do not pull on the cable to remove the connector, as this may cause damage. OTHER The Neurosign 100 which accompanies this revision of the Operating Manual contains ciruitry to remove the stimulus artifact when using monopolar stimulation. The monitor essentially turns off for a period of 1.25ms after the stimulation pulse - long enough to remove the artifact, but short enough not to remove any response.
The Magstim Company Ltd 9883-23-P16
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SECTION 6: PRE-AMPLIFIER POD__________________ CARE AND The Pod may be cleaned using a lint- free cloth damped with alcohol. Do not MAINTENANCE use water, as this will cause the instrument to give poor results until completely dry, and may even cause damage. PREPARATION The Neurosign 100 detects very small voltages within a number of motor FOR USE units. In order to ensure that as little electrical noise as possible is amplified, the instrument utilises a Pre-Amplifier Pod, which should be placed on or near the patient, usually near the head either at the top rail of the operating table or at the side. The Pod is fitted with a clip to enable it to be attached to the rails on the table; alternatively, it may be laid on the patient’s chest or secured elsewhere as required. The cable from the Pod should be connected to the Pre-Amp Pod Input socket on the Rear Panel of the instrument. Three electrodes are used to monitor each muscle group. The use of disposable needle electrodes is recommended in terms of performance, and staff and patient safety. Two of these electrodes are connected to the differential amplifier inputs, +ve and -ve (colour coded red and black), and the third is connected to the reference input, Ref (colour coded green). Care should be taken to connect the electrode wires correctly. The best results will be obtained if the wires from each muscle group are lightly twisted together - this reduces the amount of noise the wires pick up before they reach the Pre-Amplifier Pod. The use of the correct electrodes is absolutely essential, and it is recommended that only electrodes obtained from the Magstim Company Limited are used. The Company cannot guarantee the instrument’s performance if these electrodes are not used. They may be taped either to the bed or the patient as required. For further information see Section 8.
.
The Magstim Company Ltd 9883-23-P16
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Neurosign 100
SECTION 7:
PREPARATIONS FOR USE____________
The instrument should be prepared for use as follows: ?
clean the instrument with a dry cloth or a lint free material damped with alcohol.
?
place the Stimulation Probe (and reusable electrodes if these are being used) in an autoclave for the prescribed period (see Section 13). Single use needle electrodes are supplied sterile.
?
insert the electrodes and connect them to the Pre-Amplifier Pod (see Section 8 on Electrode Placement and Section 6 on the Pre-Amplifier Pod for connections).
?
ensure that CHANNEL 1 and CHANNEL 2 switches are both OFF.
?
attach the Pre-Amplifier Pod to the patient or bed and plug the cable into the PRE-AMP POD INPUT Socket on the Rear Panel of the NEUROSIGN 100.
?
connect the power lead to the power input module socket with the power switch at 0.
?
set power switch to 1; the orange LEDs will light.
?
turn on CHANNEL 1 and CHANNEL 2 as required.
?
with the electrodes connected and correctly inserted, there should be no segments lit on the bargraph with the patient at rest. For the first few minutes after needle insertion, and whilst the patient is being draped, it is normal for a few segments to flicker - the muscle is irritated by the electrodes! If segments are continuously lit, check the location of the electrodes and the wiring to the Pre-Amplifier Pod; if all the wiring appears to be in order, remove and resite the electrodes (see Section 8).
?
it is strongly recommended that the Impedance Meter available from the Company is used to check electrode placement before the patient is finally draped. This device ensures that electrodes are placed in muscle tissue and also highlights any problems there may be with the electrodes themselves.
?
raise the front of the Neurosign 100 by altering the handle position in order to allow low le vel sounds to be heard.
?
plug the Stimulator Probe Pod into the front panel connector, and locate conveniently near to the patient. This is often at the foot of the table, where the Pod can remain in the non-sterile area for easy attachment of probes.
?
connect the Stimulation Probe to the Stimulator Probe Pod, observing the colour coding.
. The Magstim Company Ltd 9883-23-P16
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SECTION 8:
SENSING ELECTRODES____________
TYPES OF Dependent on the procedure being monitored, and individual preferences, ELECTRODE different electrodes may be used. Surface electrodes may be suitable in some instances, although in the majority of cases intra- muscular, noninsulated, stainless steel needle electrodes have been found the most satisfactory. An electrode to monitor the vocal cords is also available (see Section 14). ELECTRODE The exact muscle location for the electrodes will vary according to the PLACEMENT surgical procedure being performed. It is important that the active electrodes are inserted within the muscle proper, and are not merely resting in fatty tissue. This could occur if an electrode were to be poorly placed or even passed through the muscle, reaching fatty tissue on the far side. The reference electrode should be placed close to the muscle itself to reduce artifact pick-up, but not in the same muscle group. For monitoring the facial nerve during the resection of acoustic neuromas, mastoid surgery or ear surgery, it is suggested that two muscle groups are monitored, one above the eye and the other in the lip. For the lip, the reference electrode (coloured green) should be inserted into the orbicularis oris above the vermillion border of the upper lip, with the sensing electrodes (coloured red and black) inserted into the orbicularis oris below the vermillion border of the lower lip. When placing the electrodes around the eye, the sensing electrodes should be inserted in the frontalis, with the reference electrode inserted in the upper cheek near the nose in the levator labii superioris. It is important to keep the electrodes away from the masseter surgery of the cerebello-pontine angle otherwise extraneous Vth nerve activity may be detected and misinterpreted. For parotid surgery, the electrodes must be spread to include the four major branches of the facial nerve. See the diagrams on pages 14 and 15. The electrodes must not touch each other, or a noisy or nil output will be obtained. They should be inserted parallel to each other, to reduce the risk of internal contact, and approximately 5-10mm apart. It will help to reduce noise and interference from other equipment if the wires are lightly twisted together, as supplied. The electrodes should be firmly attached to the patient using adhesive tape. Movement of the patient’s head or strong contractions can dislodge the electrodes and so the insertion of a “slack loop” in the electrode wires en route to the Pre-Amplifier Pod is a wise precaution. Refer to the diagrams on page 13 and 14 for the suggested placement of electrodes. In procedures where it might be useful to be able to monitor several muscles over a long period of time, the Neurosign 100 Dual-Pod Switch may be used. This allows two Pods to be connected, and the user may switch between the two Pods. This enables four muscles to be monitored (see Section 14).
The Magstim Company Ltd 9883-23-P16
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ELECTRODE PLACEMENT DIAGRAMS Fig. 1: Electrode placement for acoustic neuroma, mastoid and ear surgery
Fig. 2: Electrode placement suitable for Parotid gland surgery
Fig. 3: Electrode placement suitable for 4 Channel monitoring of the facial nerve (requires Dual Pod Switch)
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Fig. 4: Electrode placement suitable for submandibular gland surgery Frontalis
Orbicularis ocili
Levator labii superioris
Orbicularis oris
Mylohyoid
Fig. 5: Brachial Plexus muscle sites Nerve Radial Ulnar Median Posterior interosseous Axillary Musculocutaneous Suprascapula Medial pectoral
Muscle Brachioradialis, triceps brachii, anconeus, extensor carpi radialis longus Flexor carpi ulnaris Pronator teres, pronator quadratus, flexor carpi radialis, palmaris longus, flexor digitorum superficialis Supinator , extensor carpi ulnaris, extensor digitorum, extensor indicis, extensor pollicis longus Deltoid, teres minor Coracobrachialis, biceps brachii Supraspinatus, infraspinatus Pectoralis major, pectoralis minor
Fig. 6: Flexible electrode for use in thyroid surgery Electrode tail
Sensing tracks of electrode
Active area of electrode
Black lines on tube
Cuff
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SECTION 9:
STIMULATOR PROBE POD_________
CARE AND The Pod may be cleaned using an MAINTENANCE alcohol damped, lint- free cloth. Do
not use water. The cable and connector may be washed in water as required. Dry off the parts with a cloth and allow to dry completely before storage. The Pod may be ETO sterilised if necessary. Do not autoclave. Sterilisation of the Pod by any other means will invalidate the guarantee. RATIONALE To enable disposable Probes to be connected, a Stimulator Probe Pod is supplied. The cable from the Stimulator Probe Pod should be taken back to the Neurosign 100 and plugged into the PROBE connector. The connector is a push fit onto the socket; it is in position when a click is felt. When removing the plug, do not pull on the cable, as this may cause damage. Always pull on the connector body. The Pod should be placed in an accessible position, or it may be placed out of reach if the Probe(s) is connected before the patient is draped. Where possible, place the Pod at the opposite end of the table to the surgery usually the feet. This enables the Pod to be kept in the non-sterile area, where Probes can easily be attached or disconnected. When connecting Probes, ensure that the colour coding is observed - this is especially important for monopolar probes, which will not function if wrongly connected. It is important to realise that if two Probes are connected, both Probes will be “live”. In practice, there is little risk of a Probe accidentally stimulating the patient, but if the CURRENT CONFIRM indicator is lit even when the surgeon is not stimulating tissue, then both Probes should be checked to remove the problem. Probes must not be left standing in saline, or allowed to contact other electrical devices. PROBE The probe, pod and stimulator can be checked by placing a damp cloth TESTING across the electrode tips with the current set to 0.05mA. The CURRENT CONFIRM indicator should light. If it does not, there is a fault.
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SECTION 10:
STIMULATION PROBES________
There are four types of Reusable Probe currently available; a bipolar Probe, two concentric Probes, a monopolar Probe and two models of forceps Probe, a 150mm straight forceps and a 250mm bayonet forceps. Surgeons may choose their Probe type according to individual preferences and the demands of each procedure. These are further described in Section 14. The use of the Probes varies slightly according to their type; all reusable probes may be autoclaved. If the area to be stimulated is very wet, for example after being irrigated with saline solution, much of the current from the Probe could flow through this liquid rather than through tissue. The area to be stimulated should be made as dry as reasonably possible before stimulation. The bipolar Probe should be plugged into the connectors on the Stimulator Probe Pod when required, observing the colour code. BOTH Probe tips must come into contact with tissue in order to pass current. Should the CURRENT CONFIRM indicator stay lit after stimulation, this implies that there is still an electrical connection being made between the Probe tips, probably by liquid picked up during the procedure. This should be cleaned off before the Probe is used to stimulate tissue again. The concentric Probes are very precise and have a diameter of only 1mm. They are especially useful when working with the microscope, and allow the surgeon to differentiate between the VIIth and VIIIth cranial nerves, to stimulate within the Internal Auditory Canal, or to stimulate fine fibres of the extra-cranial nerve without stimulating surrounding tissue. See Section 14 for further information. The earth lead of the monopolar Probe should be connected to the patient via a sub-dermal, uninsulated reference electrode inserted at the operating site when required. Alternatively, the reference needle may be placed in the shoulder before the patient is draped. This needle electrode should then be connected to the white socket on the Stimulator Pod, and the monopolar probe wire attached to the blue socket. A disposable monopolar Probe is also available. This probe is supplied non-sterile, and should be sterilised by ETO - it has not been designed to be reused. The electrode of the disposable Probe is flexible, and may be bent to the desired shape. The electrode is insulated to the end, so it is capable of very precise stimulation, although it is difficult to control the degree of current spread. The Probe should be touched onto the tissue until the nerve is located, observing the same rules as to dryness as above. A higher current setting may be required using a monopolar Probe - do not exceed 1mA, as the higher current settings up to 5mA are for stimulating through bone only. The monopolar probe is designed to be used to stimulate the tumour mass, or where a large current spread is required. It is not intended to be as accurate as the bipolar series of probes, nor should it be used to try and stimulate through bone.
The Magstim Company Ltd 9883-23-P16
Page 17
31 st October 2003