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I'd be happy to answer any questions about intraoperative monitoring.
Go!
Go!
I'd be happy to answer any questions about intraoperative monitoring.
Go!
are you CNIM certified?
What's your biggest frustration from anesthesiologists? Nitrous? Too much inhalational agent? Anything else?
Yes, that can cause serious 60 Hz interference. Reorienting or powering off the warmer usually helps.The only "gripe" I'll get from the EP folks is that the fluid warmer is too close to the patient.
I'd be happy to answer any questions about intraoperative monitoring.
Go!
hehe, my biggest frustration was when anesthesiologists would tell me that Nitrous doesn't effect EPs, which it clearly does! Or when they would lie to me about patient having twitches.
Great new avatar 😀
The only "gripe" I'll get from the EP folks is that the fluid warmer is too close to the patient.
SSEPS- Stimulate a peripheral nerve, which travels from the extremity to the Somatosensory cortex, creating a small electrical field at the scalp. This measures the integrity of the spinal cord.OK, Why don't you start by defining SSEPS, Motor evoked potentials, Auditory evoked potentials, and visual evoked potentials for the sake of the junior people and the students and tell us where each one is useful or indicated.
Then maybe you can elaborate on the effect of different anesthetics on your signals in each of the above mentioned modes.
🙂
Excellent response.SSEPS- Stimulate a peripheral nerve, which travels from the extremity to the Somatosensory cortex, creating a small electrical field at the scalp. This measures the integrity of the spinal cord.
For LE SSEPs, the posterior tibial nerve is used (peroneal or tibial at the pop fossa can also be used). Responses are recorded from the pop fossa (to ensure stimulation and ensure no positional changes), the cervical spine, and the somatosensory cortex at the scalp.
For UE SSEPs, the median or ulnar nerve is used for stimulation. Responses are recorded from erb's point (same reasons as pop fossa), cervical spine and somatosensory cortex at the scalp.
SSEPs are useful for:
Lumbar and Cervical Spine surgeries: fusions, lamis, decompressions, tethered cords, tumor resections, etc...
Vascular monitoring (MCA/PCA): CEA's, aneurysm coilings/clippings.
Positioning of the brachial and lumbar plexus.
Suggested anesthetics: < 1 MAC of halogenated agent with narcotic infusion, and any other drugs as indicated. Note: Neuromuscular blockade does not effect SSEPs, but does effect EMG and TcMEPS, which are commonly used in conjunction with SSEPs.
Combining anesthetic agents (especially N2O with others) can have a devastating effect on SSEP traces. TIVA is very helpful, but is expensive.
TcMEPs (motors)- Stimulate the motor cortex at the scalp. This travels the pyramidal pathway to the target motor axon. Responses are usually measured from hands and feet, but can be measured just about any muscle involving the corticospinal tract.
TcMEPs are useful for any surgery involving the spinal cord:
Scoliosis
Cevical or thoracic Fusions
Some craniotomies
Suggested anesthetics: Due to the nature of the corticospinal pathway, TcMEPs are much more susceptible to anesthetics than SSEPs.
Therefore, if TIVA is not available, <0.5 MAC of halogenated agent with low to moderate propofol infusion is recommended. Absence of NMB is recommended, but TcMEPs can be monitored with 2/4 twitches from an NMB infusion.
EMG-Monitors integrity of nerves by measuring potentials from the nerve's target muscle. If there is irritation, the smooth EMG waveform becomes rough.
EMG is useful for:
Lumbar and Cervical Spine surgeries
Craniotomies
Cauda equina cases
Suggested anesthetics:- Absence of NMB.
Audio-Evoked Potentials (BAER/ABR)-Monitors potentials from the cochlea to the brain, via the brainstem, by use of click stimulators inserted into the ears. This produces 5 major peaks that are used to measure amplitude and latency of the stimulation. It is very important if brainstem retraction is involved, and a shift of waves usually occurs with this or manipulation of cranial nerve VIII.
Useful for:
Acoustic Neuromas
Trigeminal MVD
posterior fossa surgeries
Suggested anesthetics:-The only contraindication is use of N2O. It has been reported that N2 gas comes out of solution and causes a physical conductive hearing block.
Typical modalities:
Lumbar case: SSEPs and EMG
Cervical case: SSEPs, EMG, TcMEP
Scoliosis: SSEPs, EMG, TcMEPs
Acoustic neuroma: EMG, BAERs
I am unfamiliar with VEPs.
Excellent response.
Now, are you sure that 0.5 MAC of inhaled agents + Propofol infusion is better than 1 MAC of inhaled agents without propofol?
Consider that MAC of anesthetics is additive.
TcMEPs (motors)-
Suggested anesthetics: Due to the nature of the corticospinal pathway, TcMEPs are much more susceptible to anesthetics than SSEPs.
Therefore, if TIVA is not available, <0.5 MAC of halogenated agent with low to moderate propofol infusion is recommended. Absence of NMB is recommended, but TcMEPs can be monitored with 2/4 twitches from an NMB infusion.
what about remi, half mac agent and low-dose infusion (25 mcg/kg/min) propofol?
👍what about remi, half mac agent and low-dose infusion (25 mcg/kg/min) propofol?
For TcMEPs, yes, if the propofol is infused at a moderate rate, like 25-100 ug/kg/min.
Can you elaborate on the supersize font part above?
Also, why can't you bolus hypnotics/opioids? What does it mess with?
Yes, I have an article I can share. I'll have to dig it out of the pile.Do you have data showing that Propofol + 1/2 MAC of vapor is better than 1 MAC of vapor alone for motor evoked potentials?
You do know that it is possible to achieve burst suppression with propofol don't you?
awesome, thanks so much. would love to see this thread added to some clinical FAQ sticky as it accumulates more info!SSEPS- Stimulate a peripheral nerve, which travels from the extremity to the Somatosensory cortex, creating a small electrical field at the scalp. This measures the integrity of the spinal cord.
For LE SSEPs, the posterior tibial nerve is used (peroneal or tibial at the pop fossa can also be used). Responses are recorded from the pop fossa (to ensure stimulation and ensure no positional changes), the cervical spine, and the somatosensory cortex at the scalp.
For UE SSEPs, the median or ulnar nerve is used for stimulation. Responses are recorded from erb's point (same reasons as pop fossa), cervical spine and somatosensory cortex at the scalp.
SSEPs are useful for:
Lumbar and Cervical Spine surgeries: fusions, lamis, decompressions, tethered cords, tumor resections, etc...
Vascular monitoring (MCA/PCA): CEA's, aneurysm coilings/clippings.
Positioning of the brachial and lumbar plexus.
Suggested anesthetics: < 1 MAC of halogenated agent with narcotic infusion, and any other drugs as indicated. Note: Neuromuscular blockade does not effect SSEPs, but does effect EMG and TcMEPS, which are commonly used in conjunction with SSEPs.
Combining anesthetic agents (especially N2O with others) can have a devastating effect on SSEP traces. TIVA is very helpful, but is expensive.
TcMEPs (motors)- Stimulate the motor cortex at the scalp. This travels the pyramidal pathway to the target motor axon. Responses are usually measured from hands and feet, but can be measured just about any muscle involving the corticospinal tract.
TcMEPs are useful for any surgery involving the spinal cord:
Scoliosis
Cevical or thoracic Fusions
Some craniotomies
Suggested anesthetics: Due to the nature of the corticospinal pathway, TcMEPs are much more susceptible to anesthetics than SSEPs.
Therefore, if TIVA is not available, <0.5 MAC of halogenated agent with low to moderate propofol infusion is recommended. Absence of NMB is recommended, but TcMEPs can be monitored with 2/4 twitches from an NMB infusion.
EMG-Monitors integrity of nerves by measuring potentials from the nerve's target muscle. If there is irritation, the smooth EMG waveform becomes rough.
EMG is useful for:
Lumbar and Cervical Spine surgeries
Craniotomies
Cauda equina cases
Suggested anesthetics:- Absence of NMB.
Audio-Evoked Potentials (BAER/ABR)-Monitors potentials from the cochlea to the brain, via the brainstem, by use of click stimulators inserted into the ears. This produces 5 major peaks that are used to measure amplitude and latency of the stimulation. It is very important if brainstem retraction is involved, and a shift of waves usually occurs with this or manipulation of cranial nerve VIII.
Useful for:
Acoustic Neuromas
Trigeminal MVD
posterior fossa surgeries
Suggested anesthetics:-The only contraindication is use of N2O. It has been reported that N2 gas comes out of solution and causes a physical conductive hearing block.
Typical modalities:
Lumbar case: SSEPs and EMG
Cervical case: SSEPs, EMG, TcMEP
Scoliosis: SSEPs, EMG, TcMEPs
Acoustic neuroma: EMG, BAERs
I am unfamiliar with VEPs.
I'd be happy to answer any questions about intraoperative monitoring.
Go!
what about remi, half mac agent and low-dose infusion (25 mcg/kg/min) propofol?
Over at our institution, the NeuroSx uses DSSEPs for his Laminectomies. He claims they are superior to SSEPs and all other modalities.
Could you describe whether or not they are better/worse? Thanks
Sounds great. Quick wake ups are important for those cases.When I'm doing an intracrani IONM case, like a coiling, I use Precedex, propofol, and remi - no agent. Get really good results. I usually run the Precedex at about 0.3-0.5 mcg/kg/hr, propofol anywhere from 50-100 mcg/kg/min, and the remi titrated to like 0.05-0.1 mcg/kg/min. I try to do a "pure" TIVA, meaning no volatile at all. The nice thing is the NM folks can do EEG too and tell me if I'm "deep" enough with my anesthetic. Obviously, you can't have the patient move at all during these cases, which can make it a little tricky (when they are near the motor strip and don't want NMB, etc.). Movement can be catastrophic. I find that good communication with the IONM folks is critical. They usually sit right next to us during the case.
Towards the end of the case, you switch off the propofol, then the precedex, then the remi. The nice thing is that the patient will wake-up in about 5 minutes, if you time it right, and will be so fully awake that they can get a good neuro exam before you move them from the gantry. The surgeons love it. Remi, though, is really only good where you're not going to have much post-op pain. Likewise, it is a more expensive anesthetic, and I doubt that I'll have such liberty in PP land.
-copro
For crani with IONM, Remi + propofol when available. If no TcMEP, will crack on 0.4-0.5 Iso as well. As long as we stay away from larger amounts of gas, and don't make any sudden changes, our NM folks are pretty cool with most regimens.
Another point that I haven't seen posted is hemodynamic instability; big changes in MAP will throw off EEG, so we let our NM folks know of any changes with the red numbers as well.
When I'm doing an intracrani IONM case, like a coiling, I use Precedex, propofol, and remi - no agent. Get really good results. I usually run the Precedex at about 0.3-0.5 mcg/kg/hr, propofol anywhere from 50-100 mcg/kg/min, and the remi titrated to like 0.05-0.1 mcg/kg/min. I try to do a "pure" TIVA, meaning no volatile at all. The nice thing is the NM folks can do EEG too and tell me if I'm "deep" enough with my anesthetic. Obviously, you can't have the patient move at all during these cases, which can make it a little tricky (when they are near the motor strip and don't want NMB, etc.). Movement can be catastrophic. I find that good communication with the IONM folks is critical. They usually sit right next to us during the case.
Towards the end of the case, you switch off the propofol, then the precedex, then the remi. The nice thing is that the patient will wake-up in about 5 minutes, if you time it right, and will be so fully awake that they can get a good neuro exam before you move them from the gantry. The surgeons love it. Remi, though, is really only good where you're not going to have much post-op pain. Likewise, it is a more expensive anesthetic, and I doubt that I'll have such liberty in PP land.
-copro
Food for thought:
Do you know who is monitoring your case?
Often, the neurotech is in the room wathcing, but has somebody watching over the internet. Do you know who that somebosy is?
I have done a bit of IOM in the past. I strongly recommend to all the OSS and NS I meet to only use IOM services with the person responsible for telling him what he can cut, and if the screw breached the pedicle sitting in the room and not over the internet. I have seen PA's and people with no U.S. qualifications watching the screens.
Caveat emptor.
Yes, I know all of my staff. My company has very high standards for all of our staff.
Food for thought:
Do you know who is monitoring your case?
Often, the neurotech is in the room wathcing, but has somebody watching over the internet. Do you know who that somebosy is?
I have done a bit of IOM in the past. I strongly recommend to all the OSS and NS I meet to only use IOM services with the person responsible for telling him what he can cut, and if the screw breached the pedicle sitting in the room and not over the internet. I have seen PA's and people with no U.S. qualifications watching the screens.
Caveat emptor.
When I was a tech I had neurologist watching via internet while she was seeing patients. She wanted me to page her is something was going wrong. RIGHT, when s*it hit the fan I would be talking to surgeon right then not trying to find her over the phone. That monitoring over internet is just for insurance purposes. 🙄 If you have a good tech that knows their stuff (like the Neuroguy 😀) it is better then having virtual neurologist hehe
When I was a tech I had neurologist watching via internet while she was seeing patients. She wanted me to page her is something was going wrong. RIGHT, when s*it hit the fan I would be talking to surgeon right then not trying to find her over the phone. That monitoring over internet is just for insurance purposes. 🙄 If you have a good tech that knows their stuff (like the Neuroguy 😀) it is better then having virtual neurologist hehe
I guess the ghost doc neurologist is just a name to sue if it all falls apart.
Talk about high risk. I'd also like to know how the billing gets done. If a Neurologist can see patients and bill, and also supervise a tech in the OR and bill.....I guess it all about what codes get submitted.
If I were the patient.....none of this crap going on. Anesthesiologist, MD. Neurologist in room. NS with his PA.
do you use this modality for peds coiling too? we're a little pressed for using precedex, but they have no problem tossing over remi. it's weird. i mean, it's business?!
I guess the ghost doc neurologist is just a name to sue if it all falls apart.
Talk about high risk. I'd also like to know how the billing gets done. If a Neurologist can see patients and bill, and also supervise a tech in the OR and bill.....I guess it all about what codes get submitted.
If I were the patient.....none of this crap going on. Anesthesiologist, MD. Neurologist in room. NS with his PA.
When I was a tech we used to do spinal cord untethering. I think there are only a couple places in the country that do this. We had a neurologist in the room for the whole case. He used to sit with his back to the field. Funny thing was he wouldn't really say anything. Just cleared his throat louder and louder when the surgeon was poaking at things that he didn't like. On the other hand this was the only case that I ever saw a neurologist in.Good luck getting a neurologist in the OR to sit with an all-day spine case. I've never seen one in all the years we've been doing this, and we do a ton of spine work.
There's a pretty well publicized case in Atlanta a few years ago - neurologist in the OR all of 10 minutes to confirm that the surgeon had indeed done something very bad - his malpractice had to pay out as well.
The neurologist used to wear a down jacket until we noticed feathers floating under the microscope. After that the surgeon bought him a fiberfill jacket just for the OR.
It was always my understanding that Using Propofol + Vapor or Vapor alone does not make any difference when we are talking about SSEP's on the other hand if they are doing MEP's then Propofol is definitely superior to inhaled agents.
Despite that, you see many Neuro monitoring people insist on using Propofol for SSEP's monitoring.
This little study addresses this issue:
http://www.asaabstracts.com/strands...BCB91245FA6ED868?year=2007&index=5&absnum=508