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How TOF Ratio Monitor Helps In Anaesthesia

What is TOF monitor?

At a time when NMBAs (Neuromuscular Blocking Agents) are provided to block musculoskeletal
activities then a TOF monitor (Train of Four monitor) is used as a peripheral nervous stimulator. It
assesses neuromuscular transmission in the entire process.

Monitoring Train of Four during Surgery

From an anaesthesiologist’s perspective there are multiple benefits of having a monitor of surgical
neurophysiologist at the time of a surgery. One of the benefits is that the monitor measures
muscular relaxation or train of four monitoring more preciously. Depending on different kinds of
surgeries, we make the patient either not to move at all or to regain a certain amount of muscular

Making Sense of Train of Four and Twitches

The various effects of a neuromuscular blockade on the neuromuscular junction can be monitored in
a number of ways.

T1 amplitude/T1 baseline amplitude:

In order to execute this TOF test, a CMAP is needed to be collected before any kinds of muscle
reluctant are given. There are a number of cases where no muscle reluctant is needed. However, this
technique is excluded in a number of cases, where an upfront dose is given for the anaesthesia to
manage the breathing tube.

In this way of conducting neuro muscular monitoring you are comparing the amplitude height of the
first response of the TOF and the first response resulted after giving muscle reluctant in any TOF.

T4:T1 ratio

A more commonly used technique is to measure the ratio between T4 (fourth twitch amplitude) and
T1 (first twitch amplitude). This ratio can be measured by putting up amplitude markers on each of
the CMAP from the peak that is the highest to trough for T1 and T4. It is mandatory for the T4 to
have an amplitude, in order to measure the ratio.

T4:T1 ratio for pedicle screw stimulation:

A number of authors have suggested that while using the T4:t1 ratio for the purpose of pedicle
screw simulation, a ratio greater than 80% will bring forward optimal results. There are also a few
authors who suggest that only two twitches are needed out of the four, however, most of the
members of the neuro monitoring community do not well accept this advice.

A number of different patterns can be seen if you are able to use both T1 amplitude and T1 baseline
along with the T1:T4 ratio.

Visual inspection or palpation for twitches:

A very basic estimation of what amount of muscle relaxation is still happening is made by looking at
palpating the muscle or the hand while in a supramaximal situation. A similar deduction can be
made if a train of four is run without the T1 baseline measure or the T1:T4 ratio. In cases like this, it
is generally said that there are two twitches in number.

However, when the TOF ratio is greater than 0.4, the visual examination of muscle response is not

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Effective and Revolutionary Neuromodulation technology by MedTech Devices

Neuromuscular monitoring is a technique used in anesthesia to quantitatively determine the functionality of a person’s muscles. It is used during a patient’s recovery from the application of general anesthesia. There are several clinical tests that an anaesthetist can use to assess muscle function and power. In the past, crude means, such as testing a patient’s ability to sustain a head lift for five seconds, were used. The advancement of technology has led to better methods that are more comfortable for the patient, and also more accurate, especially for lower TOF ratios. TOF monitoring is commonly used today.

A train-of-four (TOF) ratio monitor, also known as a peripheral nerve stimulator is a device that is used to determine the degree of neuromuscular block. This monitor functions by applying a supramaximal stimulus to a nerve and then it measures the muscular response to the change. To work best, a peripheral nerve stimulator is used on nerves that must meet certain criteria. The nerve must:

  • contain a motor element
  • be located close to the surface (skin)
  • be controlling a muscle or muscle group whose movement can be observed.

An electrical current is applied using ECG electrodes. The effect of the current is maximal muscle contraction. The TOF ratio monitor then computes the ratio based on the resulting contraction.

A peripheral nerve stimulator is used by anaesthetists after an operation on a patient. In some cases, a neuromuscular block may persist after anesthesia. This condition is commonly referred to as residual paralysis, and its extent varies from patient to patient. Although seemingly mild, residual paralysis has been linked to oxygen desaturation, pulmonary collapse, muscle weakness, and acute respiratory failure that could be fatal. Different parts of the body recover at different rates, and so a reliable method of measuring the recovery is required. Residual paralysis quite common and a recent study has shown that 45% of patients experienced it. It is important for anaesthetists to quickly and accurately determine the presence of residual paralysis. This helps to prevent further complications that may result from late detection. This led to the invention of these gadgets, and since then, they have increased tremendously in popularity. There are now several peripheral nerve stimulator manufacturers in the market who are helping to lower the cost of these devices and thus make them more available to the majority. PNS devices are making the work easier for the anaesthetists and helping to save lives.

There are several benefits of using a TOF monitor. Using tactile (visual) methods to determine the muscular response is subjective and hence it is not reliable. It has been proven that even the most experienced anaesthetists cannot measure low TOF ratios. Clinical measurements alone could, therefore, be unable to detect minimal levels of paralysis. Such minimal errors could be quite costly for the patient as the problem could deteriorate and cause complications. TOF monitors are a great invention and they have helped to prevent many complications.
You ought to try our popular devices and experience great service and outstanding reliability.

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Determine the degree of Neuromuscular block with TOF

The world we live in today is mesmerizing. Technological advances are being made every day, and our lives are changing just as fast. Scientists, engineers, and their associated companies are investing time and money to create products that raise the living standards of the consumers. These changes are found in all sectors and all of the components of our daily lives. In medicine, inventions have transformed how doctors diagnose, treat, and operate.These new developments have helped save lives by enabling doctors to detect diseases early,perform operations more successfully, and treat more effectively. One such device is the Stimpod.

The Stimpod is a nerve stimulator for nerve blocks, and its purpose is to provide the status of the strength of contraction of an affected limb. To achieve this, the device has a tri-axial accelerometer. The data is then graphically shown on the display. It provides other relevant ratios as well. The device can be used for both regional and general anesthesia.

You may be wondering what problems this nerve locator device has solved. In anesthesia, it is becoming increasingly important for doctors to effectively monitor neuromuscular blocks.Stimpods are able to accurately detect residual blocks and consequently lowers one’s chances of residual paralysis during the early post-operative period. Residual paralysis should not be taken lightly and this is why doctors are keen to employ the device. There are a myriad of pulmonary complications that can be traced back to residual paralysis and these include.

  • Collapsing of the airways
  • Aspiration
  • Regurgitation
  • Hypoxia

These complications could be very costly, and deadly. It is better to prevent them than treat.

How the Stimpod functions is quite intriguing. The main reason that accelerometry is applied is to measure fine movement as opposed to monitoring visually. The limitations of subjective methods could have far-reaching consequences. It has been discovered that visual or tactile measurement techniques are unable to detect fade for TOF ratios that are from 0.4 to 1.0. Such inaccuracies cannot be overlooked and this is why the Stimpod is an invaluable tool.The triple axis accelerometer enables the Stimpod to measure the movement vector in all three dimensions. This is an extremely beneficial feature because one would not need to calibrate as is done with single-dimension accelerometers. This saves time, improves convenience and is more accurate than having to calibrate.

The Stimpod comes in a kit with a few other things that enable it to function at its best. First,we have the Stimpod device itself. There are three cables, namely, the map locate cable,locating cable, and an NMBA cable. You will also need an NMBA/standard ECG electrode that will be attached to the body. The device is easy to use with clear instructions on when to enter the cable. You will get an open circuit alert once the cables are connected. Next, you will need to set up the electrodes on the patient and the circuit will be closed. Next, you need to set the accelerometer on the patient’s thumb. The remaining instructions are basic and you will be able to use it effectively.

Try our Stimpod today and help save your patients’ lives.

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