The Stimpod NMS 450X

Quantitative NMT Monitoring

Train of Four | Post Tetanic Count | Double Burst | Tetanus | Twitch

Nerve Mapping & Locating

  • OneTouch 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
Stimpod Neuromuscular Monitor with Accelormyography sensor

OneTouch NMT

The Stimpod NMS450X features OneTouch NMT™ technology which enables the user to monitor an entire case from electrode placement to extubation at the press of a single button.

Once initiated, the Stimpod will automatically confirm and optimise the electrode placement by assigning the appropriate supramaximal current, begin Train of Four Monitoring (TOF Monitoring) and move to Post Tetanic Count (PTC) when a deep/profound block is achieved.

When the patient begins the reversal process, the Stimpod neuromuscular monitor will automatically reinitiate TOF monitoring until the patient is 90%+ recovered. No manual intervention is required to manage the process. Along the way, the Stimpod will detect and notify the user of the depth of the neuromuscular blockade.

Key Features

Accurate and real-time NMT monitoring

Supports Train-of-Four (TOF), Post-Tetanic-Count (PTC), Double Burst (DB), Tetanus and Twitch stimulation modes for accurate Neuromuscular Monitoring.

Electrode placement verification

Verify effective electrode placement and optimal stimulation current.

Data connectivity

Transfer case data to electronic medical records with ease.

Quick setup and no calibration

Patient can be monitored instantly and at any time during the procedure.

Workflow guidance

Step-by-step prompts for proper setup and use.

Reusable 3D AMG Sensor

Reusable sensor design saves running costs compared to devices with disposable sensors.

Versatile Sensor Placement

The 3D AMG sensor can be placed on the thumb, toe or face.

Standard ECG Electrode Compatible

Compatible with off-the-shelf ECG electrodes, allowing hospitals the freedom to purchase or use any existing electrode.

Nerve mapping and locating

Includes combined mapping and location functionality for peripheral nerve blocks.

Handheld or IV pole mount

Handheld portability with a rapid quick-snap IV pole mountable design makes it easy to move between the OR, PACU and ICU.

Stimpod Neuromuscular Monitor viewed from the side

New Features of the NMS450X TOF Monitor

  • OneTouch NMT™ monitoring mode for complete case monitoring at the touch of a button
  • Electrode placement and stimulating current verification for optimal NeuroMuscular Transmission Monitoring
  • Depth of block detection (Minimal, Shallow, Moderate, Deep, Profound, Full Recovery)
  • Communication cable for case data transfer to EMR or 3rd party monitor integration
  • Battery operating time increased 100% over previous models
  • Electromagnetic interference (EMI) detection
  • Facial sensor placement settings/mode

Instructional Video Series

Learn more about the Stimpod NMS450X and NMS450 and how they are used in the operating room.

Stimpod NMS450X Videos | Stimpod NMS450 Videos | Train of Four (TOF) Training Videos



Note that some of the videos below feature the Stimpod NMS450, the predecessor of the NMS450X.

Technical Specifications

Current Range

Nerve Locating: 0.0 – 5.0mA
Nerve Mapping: 0 – 20mA
NMT Monitoring: 0 – 80mA

Load Impedance

Nerve Locating: 0 – 20kΩ (100V)
Nerve Mapping: 0 – 20kΩ (400V)
NMT Monitoring: 0 – 5kΩ (400V)

Stimulating Modes

Train-of-Four (TOF)
Double Burst (DB)
Post-Tetanic-Count (PTC)
Supra Maximal Current (SMC)
Tetanus (TET)
Twitch (1Hz, 2Hz, 5Hz)
Auto (Changes automatically depending on the depth of the block)


145mm x 90mm x 30mm

Operating Temperature

10 – 40° Celsius

Storage Temperature

10 – 40° Celsius

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 anesthesia-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

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 because a depolarizing NMBA was injected.
  • It could be that the core body temperature of the patient dropped again after recovery was observed.
  • In order to prevent Post Operative Residual Curarization (PORC) patients should only be assessed for residual NMBA once their 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 or is not adhering the patient’s skin any more.
  • 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 Train of Four prior and post NMBA administration, ratios of more 100% are often noticed and might go as high as 147%.
  • The effect is ascribed to the mobilization of presynaptic acetylcholine in the Neuromuscular Junction (NMJ) after T1 promoting release in synaptic cleft during subsequent stimulations.
  • Both the Stimpod NMS450X 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. found that postoperative residual curarization is reduced in patients monitored with acceleromyography TOF ratio greater than 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

  • 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 for 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 that the electrodes have dried out to the extent that they are no longer conducting and are causing 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.
  • The latest version of Stimpod has proven its immunity to cauterization in the OR under general conditions, however, extreme intensities of cauterization could still impact the accuracy and functioning of the Stimpod.
  • All devices in the OR are generally affected by extreme intensities of cauterization.

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Ordering information

The Stimpod NMS450X TOF monitor is available around the world through our distribution partners network. Find a distributor close to you or complete the form and we will send you a full quotation.

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