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From: "Steven Belknap, M.D." <sbelknap@uic.edu>
Newsgroups: sci.med
Subject: Re: Awareness under anesthesia
Date: Thu, 11 Feb 1999 23:27:14 -0600

[[ This message was both posted and mailed: see
   the "To," "Cc," and "Newsgroups" headers for details. ]]

Hey, Cecil-

The British medical journal letter writer raises a very interesting
point. First, the dogma. Neuromuscular blocking agents are given to
reduce muscle tone during surgical anesthesia. This allegedly provides
several advantages:

1. Prior to the beginning of the surgical procedure, a neuromuscular
blocker is given to relax the muscles of the head and neck, which
simplifies placement of the endotracheal tube and avoids
overstimulation of vagal and other reflexes which can cause hypotension
and arrhythmias. This tube is connected to the ventilator, which
delivers inhalant anesthetics and oxygen and removes carbon dioxide
from the lungs. For some very short surgical procedures, the tube is
not used; a tightly fitting mask being used instead.

2. In cases of orthopedic trauma, a neuromuscular blocker may be given
so as to allow manipulation of fractured or dislocated limbs. For
example, a femur fracture is often complicated by contracture of the
quadriceps (the strongest muscle in the body), which makes realignment
of the bone extremely difficult. By paralyzing the muscle, it is
possible to set the fracture.

3. For abdominal surgery, neuromuscular blockade relaxes the muscles of
the abdomen, which facilitates access to the peritoneal space and
abdominal viscera. This allows the surgeon to use a smaller incision
than would be otherwise necessary, and shortens the duration of
surgery. Also, since muscular relaxation no longer depends upon
maintaining deep general anesthesia, lighter levels of anesthesia
suffice, which minimizes the risk of adverse drug events such as
cardiac or respiratory depression and shortens post-surgical recovery
time.

4. Neuromuscular blockade suppresses involuntary movement by the
patient during surgery, which can happen despite adequate analgesia and
amnesia. (Hmmm.)

That is the dogma.

But now you've got me wondering Cece. Neuromuscular blockers have some
serious toxicities. I know of a patient who inadvertently got no
general anesthetic, and who thus underwent surgery while conscious, but
paralyzed. He developed severe post-traumatic stress disorder.
Interactions with glucocorticosteroids can lead to diaphragmatic
weakness and skeletal muscle damage. Occasionally, life-threatening
potassium release occurs after neuromuscular blockade, typically in
patients with burn injury or denervation due to spinal injury or other
neurologic pathology. So these drugs are not entirely benign.

Some combinations of general anesthetics such as propofol + fentanyl +
nitrous oxide possess relatively few adverse effects, even in large
doses. Recovery is rapid. Adequate relaxation of muscle could perhaps
be achieved without neuromuscular blockers by achieving very deep
anesthesia.

Given this, it would be nice if someone had done some randomized,
controlled, clinical trials comparing shallow general anesthesia +
neuromuscular blockers to deep general anesthesia with some of the
better tolerated anesthetic drugs. There are techniques, such as EEG
spectral edge monitoring which would allow monitoring of the depth of
anesthesia.

I don't think such studies have been done. At least, I've never seen
such a study, and I couldn't find any controlled clinical trials
addressing this question via KnowledgeFinder or OVID. It is entirely
possible that standard anesthesiology practice includes neuromuscular
blockade unncessarily. If you could send me the reference to the letter
you cited, I could perhaps comment further.

-Steven

In article <19990208175520.21048.00000145@ng94.aol.com>, Ed Zotti
<edzotti@aol.com> wrote:

> I'm researching a newspaper column about awareness under anesthesia -
> that is, patients who are given insufficient general anesthesia prior to
> surgery but are unable to alert the OR staff due to the muscle relaxant
> and suffer unimaginable agonies on the operating table. A letter writer
> in a British medical journal claims that this problem is a holdover from
> the days "when general anesthetic drugs were highly unsatisfactory."
> (Unsatisfactory how? Wore off too quick? Too many side effects?) Anyway,
> the writer believes that muscle relaxants are not as important as they
> used to be and that greater emphasis should be placed on general
> anesthesia, there by eliminating many cases of accidental awareness..
> 
> Is there any truth to this? How has the practice of anesthesia evolved
> over time? Is too much emphasis placed on muscle relaxants? And what
> exactly goes into the chemical cocktail used in general anesthesia,
> anyway?
> 
> Thanks for any info. CCs by E-mail greatly appreciated. -Ed


From: sbharris@ix.netcom.com(Steven B. Harris)
Newsgroups: sci.med
Subject: Re: Awareness under anesthesia
Date: 12 Feb 1999 08:44:01 GMT

In <sbelknap-110219992327145312@mac0.uicomp.uic.edu> "Steven Belknap,
M.D." <sbelknap@uic.edu> writes:

>[[ This message was both posted and mailed: see
>   the "To," "Cc," and "Newsgroups" headers for details. ]]
>
>Hey, Cecil-
>
>The British medical journal letter writer raises a very interesting
>point. First, the dogma. Neuromuscular blocking agents are given to
>reduce muscle tone during surgical anesthesia. This allegedly provides
>several advantages:
>
>1. Prior to the beginning of the surgical procedure, a neuromuscular
>blocker is given to relax the muscles of the head and neck, which
>simplifies placement of the endotracheal tube and avoids
>overstimulation of vagal and other reflexes which can cause hypotension
>and arrhythmias. This tube is connected to the ventilator, which
>delivers inhalant anesthetics and oxygen and removes carbon dioxide
>from the lungs. For some very short surgical procedures, the tube is
>not used; a tightly fitting mask being used instead.
>
>2. In cases of orthopedic trauma, a neuromuscular blocker may be given
>so as to allow manipulation of fractured or dislocated limbs. For
>example, a femur fracture is often complicated by contracture of the
>quadriceps (the strongest muscle in the body), which makes realignment
>of the bone extremely difficult. By paralyzing the muscle, it is
>possible to set the fracture.
>
>3. For abdominal surgery, neuromuscular blockade relaxes the muscles of
>the abdomen, which facilitates access to the peritoneal space and
>abdominal viscera. This allows the surgeon to use a smaller incision
>than would be otherwise necessary, and shortens the duration of
>surgery. Also, since muscular relaxation no longer depends upon
>maintaining deep general anesthesia, lighter levels of anesthesia
>suffice, which minimizes the risk of adverse drug events such as
>cardiac or respiratory depression and shortens post-surgical recovery
>time.
>
>4. Neuromuscular blockade suppresses involuntary movement by the
>patient during surgery, which can happen despite adequate analgesia and
>amnesia. (Hmmm.)
>
>That is the dogma.
>
>But now you've got me wondering Cece. Neuromuscular blockers have some
>serious toxicities. I know of a patient who inadvertently got no
>general anesthetic, and who thus underwent surgery while conscious, but
>paralyzed. He developed severe post-traumatic stress disorder.
>Interactions with glucocorticosteroids can lead to diaphragmatic
>weakness and skeletal muscle damage. Occasionally, life-threatening
>potassium release occurs after neuromuscular blockade, typically in
>patients with burn injury or denervation due to spinal injury or other
>neurologic pathology. So these drugs are not entirely benign.
>
>Some combinations of general anesthetics such as propofol + fentanyl +
>nitrous oxide possess relatively few adverse effects, even in large
>doses. Recovery is rapid. Adequate relaxation of muscle could perhaps
>be achieved without neuromuscular blockers by achieving very deep
>anesthesia.
>
>Given this, it would be nice if someone had done some randomized,
>controlled, clinical trials comparing shallow general anesthesia +
>neuromuscular blockers to deep general anesthesia with some of the
>better tolerated anesthetic drugs. There are techniques, such as EEG
>spectral edge monitoring which would allow monitoring of the depth of
>anesthesia.
>
>I don't think such studies have been done. At least, I've never seen
>such a study, and I couldn't find any controlled clinical trials
>addressing this question via KnowledgeFinder or OVID. It is entirely
>possible that standard anesthesiology practice includes neuromuscular
>blockade unncessarily. If you could send me the reference to the letter
>you cited, I could perhaps comment further.
>
>-Steven



Comment:

   An excellent reply.  Should the paralytic agents still be found to
be necessary, spectral edge monitoring is getting easier.  The new
machines are not the old clunkers where you got more information than
anyone knew what to do with, and required a lot of scalp needles. The
spectral edge, for those who are unfamiliar with it, is the frequency
below which 95% of the spectral power of the EEG lies.   Since it's a
sort of measure of integrated high frequency EEG power (of the sort
associated with consciousness), it can be used to monitor wakefulness
and alertness.  These days, the machines that do this are about the
size of a palmtop computer, which they basically are, and they have one
electrode that sticks on your forehead, a lot like something out of a
Steve Martin movie.  Now the machine does not show you the Fourier
transformed EEG power spectrum, and the statistics.  No, that was
beyond the intellect of the average schlub who passes gas, I suppose.
Instead, now what we have on the market is a little a machine which
computes the EEG spectral power, figures out the point under which 95%
of the spectral power lies, and then converts THIS into one easy-to-use
number from 10 to 100, for use by those who need Anaesthesiology For
Dummies.   Which is a surprising number of people who put other people
to sleep, it turns out.  Your dentist, just for beginners.

   Ceders Sinai in L.A. just bought one of these Dummed Down gismos for
every O.R. in their hospital.  They figured out what fraction of people
would bring suits, and what fraction of suits would be won once the
average jury figured out just what CAN happen to you, and there was no
objective evidence whatsoever that it hadn't to the guy bringing the
suit, and  ....  they geeked.

   It's all too bad, because a lot of very expensive research went into
this technology by several companies that failed utterly, because they
could not sell the big machines that gave the interesting data.  They
did the work, and they didn't reap the benfits.  We have a LifeScan,
made in Germany, which we use in research on animals. It puts out a 3-D
EEG power spectrum, bihemispheric, in real time, in a moving
rectangular virtual box which appears on a TV screen.  Output to
computer data aquisition.  Awesome.  A lot of them, which each cost God
knows how many 10s of thousands of dollars new, were thrown in the
garbage, and we rescued a few.  When they break we'll have to
canibalize them or toss them, because the company that made them does
not support them.  I believe it no longer exists.

                                         Steve Harris, M.D.


From: sbharris@ix.netcom.com(Steven B. Harris)
Newsgroups: sci.med
Subject: Re: Awareness under anesthesia
Date: 15 Feb 1999 04:05:22 GMT

In <sbelknap-130219992256482580@slip6b-08.dialin.uic.edu> "Steven
Belknap, M.D." <sbelknap@uic.edu> writes:

>The "Hmmm." refers to my concern that maybe its not such a good idea to
>hide evidence of awareness, which involuntary movement may represent.


    Or may not (since even brain dead people have been seen to do a
fair amount of random limb moving when removed from ventilators).  It's
simply impossible to tell one way or the other.  I agree, of course,
that it's not a good idea to interpose one more block to awareness of
inadequate anaethesia without very good reasons.  And probably EEG
spectral monitoring of anaesthesia plane will be standard of care in 5
years.



 



































































































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