Anesthesia

TOF Monitor For Anesthesia & Precision Nerve Location In Regional Anaesthesia

Simple. Accurate. Reliable.

Stimpod Nerve Stimulator Anesthesia devices are very useful and effective for Anesthesiologist at Multi-specialty Hospitals, Super specialty Hospitals, Research Institutes, Government Medical Colleges and Hospitals, etc…

STIMPOD NMS 450

Nerve Stimulator-Mapper-Locator with Acceleromyography for
Muscle relaxation monitoring

(NMBA – Neuro Muscular Blockade monitoring) during General Anesthesia & Peripheral Nerve Stimulator (PNS) (Nerve Mapper-Locator) during Regional Anesthesia

STIMPOD NMS 450 with TRIAXIAL ACCELEROMYOGRAPHY is Ideal for Muscle Relaxant (NMBA) Monitoring

Features

STIMPOD NMS 450 with TRIAXIAL ACCELEROMYOGRAPHY & Transcutaneous Electrical Nerve Stimulation is Ideal for Muscle Relaxant (NMBA) monitoring

  • The Various modes guide, when to Intubate, Extubate and confirm Patient Reversal
    Also, assists, in identifying, end of Surgical Block OR during Drug top up
    Provides Real time, feedback of the strength of contraction ( for TOF, DBS & PTC, modes)
  • Accelerometery, detects fine movement differences, and offers Major advantage over, gauging contraction strength, visually or tactilely
    The strength of each measured Contraction is displayed Graphically, including relevant Ratios.
  • The Tri axial accelerometery does not need Calibration, & reduces Setup time of the procedure

STIMPOD NMS 450 is equipped with :

  • Acceleromyography sensor to provide real time feedback of strength of contraction.
  • Proximity indicator to precisely identify location of nerves.
  • Real-Time Graphical display of each measured contraction, with relevant ratios
  • All modes availability – TOF, DBS, PTC, TET, etc..
  • Transcutaneous nerve simulation stimulation of Nerve with mapper probe.
  • Facility to pre-program 20 different Current and Pulse width settings.
  • Shows charge transfer waveform to indicate excessive impedance in the circuit / skin, electrode condition.
  • Auto detection of cables to change the mode from nerve mapping to nerve location.

Learn how the Stimpod NMS450 is used in the operating theatre.

Instructions for use

Frequently Asked Questions

  • Even moderate Post Operative Residual Curarization (PORC) decreases chemoreceptor sensitivity to hypoxia.
  • PORC is associated with impairment of muscles of the upper pharynx and upper oesophagus leading to regurgitation and aspiration.
  • Reduced upper airway volume or partial airway collapse
  • Significant risk factor for the development of pulmonary complications – increased morbidity and mortality
  • Research shows that almost half of anaesthesia-related deaths are directly or indirectly attributable to PORC.
  • The reason for this is attributed to the binding of non-depolarizing neuromuscular blocking agents to presynaptic acetylcholine receptors, resulting in inhibition of the recruitment of Ach from the reserve pool.
  • A minimum of spontaneous recovery does not need to be present before Sugammadex can be administered. Even the deepest neuromuscular blockade can be reversed rapidly within one to two minutes.
  • Fewer autonomic side effects are anticipated with Sugammadex.
  • It could be that the core body temperature of the patient dropped again after recovery was observed.
  • In order to prevent PORC patients should only be assessed for residual NMBA once core has reached a temperature of greater than 36 °C.

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STIMPOD NMS 450T

Nerve Stimulator-Mapper-Locator with Acceleromyography for
Muscle relaxation monitoring

(NMBA – Neuro Muscular Blockade monitoring) during General Anesthesia & Peripheral Nerve Stimulator (PNS) (Nerve Mapper-Locator) during Regional Anesthesia

STIMPOD NMS 450 with TRIAXIAL ACCELEROMYOGRAPHY is Ideal for Muscle Relaxant (NMBA) Monitoring

Features

STIMPOD NMS 450T with TRIAXIAL ACCELEROMYOGRAPHY is Ideal for Muscle Relaxant (NMBA) monitoring

  • The Various modes guide, when to Intubate, Extubate and confirm Patient Reversal
    Also, assists, in identifying, end of Surgical Block OR during Drug top up
    Provides Real time, feedback of the strength of contraction ( for TOF, DBS & PTC, modes)
  • Accelerometery, detects fine movement differences, and offers Major advantage over, gauging contraction strength, visually or tactilely
    The strength of each measured Contraction is displayed Graphically, including relevant Ratios.
  • The Tri axial accelerometery does not need Calibration, & reduces Setup time of the procedure

STIMPOD NMS 450 is equipped with :

  • Acceleromyography sensor to provide real time feedback of strength of contraction.
  • Proximity indicator to precisely identify location of nerves.
  • Real-Time Graphical display of each measured contraction, with relevant ratios
  • All modes availability – TOF, DBS, PTC, TET, etc..
  • Transcutaneous mapping of Nerve with mapper probe.
  • Facility to pre-program 20 different Current and Pulse width settings.
  • Shows charge transfer waveform to indicate excessive impedance in the circuit / skin, electrode condition.
  • Auto detection of cables to change the mode from nerve mapping to nerve location.

Learn how the Stimpod NMS450T is used in the operating theatre.

Instructions for use

Frequently Asked Questions

  • Even moderate Post Operative Residual Curarization (PORC) decreases chemoreceptor sensitivity to hypoxia.
  • PORC is associated with impairment of muscles of the upper pharynx and upper oesophagus leading to regurgitation and aspiration.
  • Reduced upper airway volume or partial airway collapse
  • Significant risk factor for the development of pulmonary complications – increased morbidity and mortality
  • Research shows that almost half of anaesthesia-related deaths are directly or indirectly attributable to PORC.
  • The reason for this is attributed to the binding of non-depolarizing neuromuscular blocking agents to presynaptic acetylcholine receptors, resulting in inhibition of the recruitment of Ach from the reserve pool.
  • A minimum of spontaneous recovery does not need to be present before Sugammadex can be administered. Even the deepest neuromuscular blockade can be reversed rapidly within one to two minutes.
  • Fewer autonomic side effects are anticipated with Sugammadex.
  • It could be that the core body temperature of the patient dropped again after recovery was observed.
  • In order to prevent PORC patients should only be assessed for residual NMBA once core has reached a temperature of greater than 36 °C.

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STIMPOD NMS 450X

One-Touch NMT Monitoring
Electrode Placement Verification
Quick Setup & No Calibration
Handheld
Data Connectivity

Features

  • One-Touch NMT Monitoring
  • Electrode Placement Verification
  • Quick Setup & No Calibration
  • Handheld
  • Data Connectivity
  • Reusable Sensor
  • Standard ECG Electrode Compatible
  • Quantitative NMT Monitoring reduces incidence of residual paralysis,increases operating room throughput and lowers cost
  • 23 years of AMG research proves it identifies residual paralysis in 97% of patients
  • Pioneers of quantitative monitoring technology since 1998
  • Trusted by anaesthesiologists in over 40 countries

Learn how the Stimpod NMS450 is used in the operating theatre.

Instructions for use

Frequently Asked Questions

  • Even moderate Post Operative Residual Curarization (PORC) decreases chemoreceptor sensitivity to hypoxia.
  • PORC is associated with impairment of muscles of the upper pharynx and upper oesophagus leading to regurgitation and aspiration.
  • Reduced upper airway volume or partial airway collapse
  • Significant risk factor for the development of pulmonary complications – increased morbidity and mortality
  • Research shows that almost half of anaesthesia-related deaths are directly or indirectly attributable to PORC.
Stimulation Pattern Onset of Action Deep NMB Moderate NMB Neuromuscular Recovery
TOF Suitable Not Suitable Suitable Conditionally Suitable
TOF with objective monitoring Suitable Not Suitable Suitable Suitable
DB Conditionally Suitable Suitable Not Suitable Conditionally Suitable
PTC Conditionally Suitable Suitable Not Suitable Not Suitable
Tetanus Not Suitable Not Suitable Not Suitable Not Suitable
  • Train of Four (TOF) with quantitative monitoring (objective monitoring).
TOF Ratio Inability to sustain headlift for > 5 sec [n=12] Inability to swallow normally [n=12] “Fade Visible” [n=12]
0.5 1 10 1
0.8 0 7 0
1.0 0 1 0
  • Eikermann et al. AM J Repir Crit Care Med. 2007;175:9-15
  • Berg H et al. Acta Anaesthesiol Scand. 1997; 41:1095-1103
  • Murphy GS et al. Anesth Analg. 2008; 107:130-137

What clinical outcomes could be expected at which TOF ratios?

Monitoring TOF Ratio on adductor pollicis Ratio: 0.5 Ratio: 0.8 Ratio: 1.0
Pharyngeal function (Swallowing) Significantly Impaired Impaired Mostly Normal
Integrity of upper airway Significantly Impaired Impaired Mostly Normal
Hypoxic respiratory response Frequently Impaired Mostly Normal Normal
  • Eikermann et al. AM J Repir Crit Care Med. 2007;175:9-15
  • Berg H et al. Acta Anaesthesiol Scand. 1997; 41:1095-1103
  • Murphy GS et al. Anesth Analg. 2008; 107:130-137
  • The reason for this is attributed to the binding of non-depolarizing neuromuscular blocking agents to presynaptic acetylcholine receptors, resulting in inhibition of the recruitment of Ach from the reserve pool.
  • A minimum of spontaneous recovery does not need to be present before Sugammadex can be administered. Even the deepest neuromuscular blockade can be reversed rapidly within one to two minutes.
  • Fewer autonomic side effects are anticipated with Sugammadex.
  • It could be that the core body temperature of the patient dropped again after recovery was observed.
  • In order to prevent PORC patients should only be assessed for residual NMBA once core has reached a temperature of greater than 36 °C.

Heier T, Caldwell J E, Impact of Hypothermia on the Response to Neuromuscular Blocking Drugs, Anesthesiology 2006; 104:1070-80

  • The location of the electrode could have moved.
  • It could be that the supramaximal stimulating current was not first established.
  • It could be that the electrode dried out.
  • It could be that the polarity of the electrodes was reversed.
  • When facial muscles are stimulated there is a risk of direct muscle stimulation.
  • When monitoring TOF prior and post NMBA, ratios of > 100% are often noticed (As high as 147%)
  • Effect ascribed to mobilization of presynaptic acetylcholine in NMJ after T1 promoting release in synaptic cleft during subsequent stimulations.
  • Both Stimpod NMS450 and TOF-Watch SX (uncalibrated) show values greater than 100%.

Suzuki T, Fukano N, Kitajima O, Saeki S, Ogawa S, 2006.’Normalization of acceleromyographic train-of-four ratio by baseline value for detecting residual neuromuscular block.’ British Journal of Anaesthesia; 96:44–7

  • The cathodes (negative electrodes) could be placed at different distances from targeted nerves.
  • It could be that the supramaximal stimulating current was not first established for both stimulators independently.
  • It could be that one or more electrodes dried out.
  • It could be that the polarity of some electrodes was reversed.
  • It is a known fact that stimulation of the ulnar nerves on one patient’s two arms would results in different TOF ratios if all other setup factors are significantly similar.
  • It remains unclear as to what acceleromyography TOF ratio is necessary to exclude clinically significant PORC.
  • Glenn et al PORC reduced in patients monitored with acceleromyography TOF of >90%.

Claudius, C., Viby-Mogensen, J., 2008. ‘Acceleromyography for Use in Scientific and Clinical Practice – A Systematic Review of the Evidence’. Anesthesiology; 108:1117-40 
Glen S., Murphy, M. D., etc. 2011. ‘Intraoperative Acceleromyography Monitoring Reduces Symptoms of Muscle Weakness and Improves Quality of Recovery in the Early Postoperative Period

  • In an attempt to increase the reliability of the TOF-Watch accelerometer a preload device was introduced. According to Claudius, Viby-Mogensen (2008), there is insufficient evidence to confirm or deny that the application of a preload will increase the precision of acceleromyography.
  • The preload device attempts to restrict the movement of the thumb to one dimension. With a three dimensional accelerometer this is not necessary.

Claudius, C., Viby-Mogensen, J., 2008. ‘Acceleromyography for Use in Scientific and Clinical Practice – A Systematic Review of the Evidence’. Anesthesiology; 108:1117-40

  • No. Mechanomyography is the established standard to measure neuromuscular block (NMB), however, it is impractical in a clinical setting and is only reserved for research purposes.
  • Acceleromyography is based on Newton’s second law of motion, stating that: F (force) = m (mass) X a (acceleration).
  • Acceleromyography should be interchangeable with mechanomyography if the mass (in this case the mass of the thumb) is constant.
  • Surprisingly acceleromyography cannot be used interchangeably with mechanomyography in pharmacodynamic studies.
  • One difference between mechanomyography and acceleromyography is that the contractions observed during acceleromyography involve a three-dimensional movement involving three joints, frictional forces, and deformation of tissues.
  • The accelerometer of the TOF-Watch device utilizes a 1-dimensional accelerometer losing much of the information of the complex 3-dimensional movement.
  • The Stimpod NMS450, on the other hand, uses three accelerometer sensors, each positioned perpendicular on the other two, to enable the device to measure acceleration in three dimensions.
  • A specialized algorithm processes the information provided by the three accelerometers and provides a value representing the size of the vector of the three dimensional movement.
  • Xavant is of the opinion that this feature makes acceleromyography more reliable and should bring its response curves more in line with mechanomyography.

Claudius, C., Viby-Mogensen, J., 2008. ‘Acceleromyography for Use in Scientific and Clinical Practice – A Systematic Review of the Evidence’. Anesthesiology; 108:1117-40 
Baillard, C., Bourdiau ,S., Le Toumelin, P.,Ait Kaci, F., Riou, B., Cupa, M and Samama, M. 2004. ‘Assessing Residual Neuromuscular Blockade Using Acceleromyography Can Be Deceptive in Postoperative Awake Patients’, Anesthesia Analgesia; 98:854–7

  • TOF-Watch and TOF-Watch S will calculate and display T2/T4 and if this value exceeds 100% it would simply limit the display to 100%.
  • TOF-Watch SX has a well-implemented normalization procedure but it takes 20 minutes to perform.
  • Xavant is currently researching a practical way of implementing a normalization algorithm.

Claudius, C., Viby-Mogensen, J., 2008. ‘Acceleromyography for Use in Scientific and Clinical Practice – A Systematic Review of the Evidence’. Anesthesiology; 108:1117-40

  • The Stimpod has an automated switch off function which is activated if the device has not been in use for more than 10 minutes.
  • It could be because electrodes have dried out to the extent that they resemble an open circuit.
  • There could be a problem with the cable.
  • There could be a problem with the device.
  • There could be a problem with the cable.
  • There could be a problem with the Stimpod.
  • The Stimpod is in ‘TWI’ mode. In this mode, the device does not communicate with the accelerometer.
  • The Stimpod is in ‘TET’ mode. In this mode, the device does not communicate with the accelerometer.
  • There could be a momentary interference that interrupted communication between the accelerometer and Stimpod.
  • There could be a problem with the accelerometer cable.
  • There could be a problem with the Stimpod.
  • No. In order for Stimpod to receive its certification, it has to pass certain tests to prove its immunity to electromagnetic interference (EMI) and electrostatic discharge (ESD). All versions of Stimpod have passed these criteria.
  • In beginning 2012 the Stimpod was redesigned in order to increase its immunity to EMI and ESD.
  • The new version of Stimpod has proven its immunity to cauterization in the OR under general conditions, however, extreme intensities of cauterization could still impact of the accuracy and functioning of the Stimpod.
  • All devices in the OR are generally affected by extreme intensities of cauterization.

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Stimpod NMS410

The accurate and cost-effective alternative to ultrasound techniques

Increase your accuracy and close needle tip placements

The NMS410’s technology is not only on par with ultrasound techniques when determining anatomical deviations prior to needle insertion, but reduces the duration of the procedure while providing excellent patient comfort and safety.

Features

Simultaneous nerve mapping and nerve location

Auto-sensing technology monitors whether the mapping probe or needle touches the patient and adjusts the current range accordingly.  With the needle in one hand and the probe in the other, it’s easy to achieve quick and precise nerve location.

Map nerves prior to needle insertion for ultimate accuracy

The nerve mapping probe enables transcutaneous nerve mapping at higher currents (up to 20mA) to assist in finding deeper peripheral nerves. The small surface area of the tip ensures effective discrimination.

Visual and audible proximity indicator

When the target current and pulse width ranges are reached, the Stimpod will indicate probable nerve proximity. This safety mechanism prevents the practitioner from getting confused with the current settings at different pulse widths while ensuring the needle tip is close to the nerve before administering the block.

Real-time waveform display

The waveform display indicates if the pulse is delivered according to the settings.  If the waveform is not square, this indicates excessive impedance (> 20kOhm) in the circuit which means the ECG electrodes or skin condition needs to be re-assessed before nerve location can be successfully completed.

Simultaneous nerve mapping and nerve location

Auto-sensing technology monitors whether the mapping probe or needle touches the patient and adjusts the current range accordingly. With the needle in one hand and the probe in the other, it’s easy to achieve quick and precise nerve location.
Map nerves prior to needle insertion for ultimate accuracy

The nerve mapping probe enables transcutaneous nerve mapping at higher currents (up to 20mA) to assist in finding deeper peripheral nerves. The small surface area of the tip ensures effective discrimination.
Visual and audible proximity indicator

When the target current and pulse width ranges are reached, the Stimpod will indicate probable nerve proximity. This safety mechanism prevents the practitioner from getting confused with the current settings at different pulse widths while ensuring the needle tip is close to the nerve before administering the block.
Real-time waveform display

The waveform display indicates if the pulse is delivered according to the settings. If the waveform is not square, this indicates excessive impedance (> 20kOhm) in the circuit which means the ECG electrodes or skin condition needs to be re-assessed before nerve location can be successfully completed.

Dr Russel Raath, MMChB, MMed (Anaes), (Pret.) FIPP (WIP), explains how the Stimpod NMS410 is used in regional anaesthesia procedures.

Instructions for use

Frequently Asked Questions

Nerve Mapping

Nerve mapping is a technique whereby superficial peripheral nerves can be traced and located transcutaneously for peripheral nerve blocks during regional anaesthesia procedures. The technique enables the anesthesiologist to determine the site for needle insertion prior to puncturing the skin.

The current density radiates outward from the nerve mapping pen in a spherical form. There is also a decrease in behavioural density as the distance is increased from the source. Axons with a larger diameter exhibit a lower activation threshold than small axons. This results in electrical stimulation activating larger axons first before activating the smaller axons. Looking at the behavioural density, most of the axons will be activated close to the probe, whereas only the larger diameter axons will be activated further away from the probe. There are two options to increase the energy delivered to a nerve without changing the distance from the electrode – increase the current amplitude and/or increase the pulse width.

There is an optimal Pulse Width at which a specific nerve is most excitable. This is called the chronaxie threshold. It is preferable to keep the pulse width as close to this value for the related nerve or nerve plexus, as the Peripheral Nerve Stimulator allows, then increase only the current.

It should be noted that, although there are many published values for chronaxie for various excitable tissues, the range of variability for a given tissue type is quite large. It is generally assumed, however, that nerves can be classified according to their chronaxie thresholds as follows:

 

Classification Chronaxie Sensory Functions
A (alpha) 40-100μs Predominantly motor neurons. They also have
the following sensory functions: Proprioception,
hair receptors, vibratory sensors and high
discrimination touch
A (delta) 150μs Deep pressure and touch, pricking pain and cold
C 400μs Crude touch and pressure, tickle,
aching pain, cold and warmth

 

From the above table, it would seem reasonable to deduce that the ideal pulse width to facilitate a motor nerve response (A alpha), would be around 100μs. If one sets the nerve stimulator at 100μs and increases the amplitude to 5mA giving a total charge of 500nC one would not get the same muscle response as if the setting is at 500μs and 1mA, also giving a total charge of 500nC. In the second case even though the total charge transferred to the nerve is the same, because of the chronaxie threshold of 100μs for the nerve, much of the energy transferred to the nerve after the 100μs is wasted on the nerve.

This is clearly shown by the graph below. The strength-duration curve (green) indicates the current necessary at the different pulse widths to facilitate a contraction. The energy cost or total charge is shown by the blue curve. It can be seen that the stimulation is the most energy efficient at the chronaxie pulse of +- 80μs width as would be expected. It should be noted how the energy cost increases when pulse width increases.

As a preference, keep the nerve stimulator at a 100μs pulse width and adjust the current. If the nerve stimulator is already set at 20mA and the Nerve Mapping Probe does not elicit any neuromuscular response, increasing the pulse width to 300μs will offer 3 x more charge, however bear in mind that the net effect on the nerve will not constitute a contraction which is 3 times more powerful.

Due to the fact that the surface location of the nerve is pre-determined and thus the optimal entry point for the needle, the technique reduces the need for multiple needle insertions and discomfort to the patient. It also reduces the time to perform the peripheral regional nerve block.

The nerve mapping technique may be used for various approaches to the brachial plexus, as well as the axillary, musculo-cutaneous, ulnar, median and radial nerve blocks of the upper limb; and the femoral, sciatic and popliteal nerve blocks in the lower limb. Surface nerve mapping is particular useful where classic anatomical landmarks are absent or difficult to define, for example in children with contractures (arthrogryposis multiplex congenital; burns) or with major congenital limb defects.

It relates the charge intensity necessary to elicit a neuromuscular response to the distance between the probe and the nerve.

In order for nerve excitation to take place, the energy delivered to the nerve must be high enough to trigger the threshold voltage. The current-distance relationship is governed by Coulomb’s Law:

E = K(Q/r²)  where E is the energy required, K is a constant, Q is the minimum current and r is the distance away from the electrode.

The equation shows what effect the distance has on the energy delivered .: 2 x Distance = ¼ Energy

The equation also shows how you need to increase the current as your distance increases .: 2 x Distance = 4 x Current

The Stimpod peripheral nerve stimulator allows the user to use the needle and probe simultaneously, eliminating the need to change cables or make markings on the patient.

The practical application of nerve mapping as a technique has always been a cumbersome technique. In order to use nerve mapping effectively, the position and angle of the probe must be recorded exactly before inserting the needle. Marking the probe position with a marker has proved unsuccessful and cumbersome, as this does not capture the exact position and angle relating to subcutaneous structures – i.e. bone structure, muscles etc. It is important to have the ability to keep the probe in its original position when inserting the needle. This will ensure exact positioning and angle of the needle.

The Stimpod peripheral nerve stimulator facilitates this procedure by providing a combined Nerve Mapping/Locating cable. The unit will automatically switch between the probe and the needle, depending on which device is in contact with the skin. The Stimpod will guide you through the entire procedure, switching between the probe and the needle as needed whilst keeping an eye out for high impedance and nerve proximity.

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