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Quantitative Architecture of the Brachial Plexus and Surrounding Compartments, and Their Possible Si

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the architecture of the brachial plexus? Ratio of neural and nonneural ... plexus block: ... doses of local anesthetic in the distal plexus. Limitations ... – PowerPoint PPT presentation

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Title: Quantitative Architecture of the Brachial Plexus and Surrounding Compartments, and Their Possible Si


1
Quantitative Architecture of the Brachial Plexus
and Surrounding Compartments, and Their Possible
Significance for Plexus Blocks
Nizar Moayeri, M.D., Paul E. Bigeleisen, M.D.,
Gerbrand J. Groen, M.D., Ph.D Anesthesiology
2008 108299304
  • ?????????????
  • R2 ??? / VS ???

2
Background
  • Nerve injury after brachial plexus block
  • shortterm neurologic deficits
  • pain sensations
  • small incidence
  • 0.02 to 0.2 for distal block (axillary nerve
    block)
  • 0.03 to 0.4 in short- and severe long-term
    neurologic complications of proximal blocks
    (interscalene nerve block)

3
Background
  • Intraneural injection of the local anesthetic !
    (with high pressures)
  • the use of electrical neurostimulation to evoke
    motor responses in the proximity of the nerves
    without puncturing them (epineurium)
  • ultrasound-guided local anesthetic injection
  • avoiding injection within the epineurium ?
  • the architecture of the brachial plexus?
  • Ratio of neural and nonneural tissue in
    epineurium
  • differences in onset time and LA volumes

4
Background
  • A successful brachial plexus block
  • the type, amount, concentration, lipophilicity,
    place of injection, and anatomical distribution
    of the local anesthetic
  • the lipid content of the nerve tissue and
    surrounding extraneural tissue
  • Proximal blocks (interscalene and
    supraclavicular) are thought to have a faster
    onset than distal blocks (infraclavicular and
    axillary)
  • hypothesized that distal compartments surrounding
    the brachial plexus are larger and contain more
    fat and stroma within the epineurium

5
Materials and Methods
  • Cryomicrotomy
  • Four shoulders of three different cadavers
  • frozen in carboxymethylcellulose gel at -25C
  • Cryomicrotome consecutive sagittal sections
    (interval, 0.078 mm)
  • high-resolution photography
  • 300 pixels/inch, total 1,1001,500 images
  • coronal and axial planes were reconstructed using
    Enhanced Multiplanarreformatting Along Curves
    software

6
Materials and Methods
7
Materials and Methods
  • Interactive Image Sequence Viewer program
    individual roots, trunks, cords, and nerves
  • interscalene, supraclavicular, midinfraclavicular,
    and subcoracoid regions midpoint, and locations
    5 and 10 mm medial and lateral to each midpoint

8
Materials and Methods
9
Materials and Methods
  • Original reconstructed image
  • Measured intraepineurial tissue (shaded in gray)
  • measured neural tissue including perineurium and
    nerve fascicles (black spots)
  • Combined image showing both measurements
    superimposed on the same image

10
Materials and Methods
  • Areas of each tissue were demarcated and
    calculated
  • two-sided Student t test.
  • For statistical significance, a value of Plt 0.05
    was chosen

11
Results
  • The median amount of neural tissue remained
    approximately the same throughout the brachial
    plexus (41.16.3 mm2 range, 3060 mm2)
  • values for the interscalene, supraclavicular,
    midinfraclavicular, and subcoracoid regions,
    respectively, were 40.73,8 mm2 (range, 3245
    mm2), 45.05.2 mm2 (range, 3757 mm2), 38.54.4
    mm2 (range, 3348 mm2), and 40.39.4 mm2 (range,
    3060 mm2)

12
Results
  • nonneural tissue inside the epineurium increased
    from proximal to distal
  • median surface areas were 46.79.5 mm2 (range,
    2562 mm2), 47.27.4 mm2 (range, 3664 mm2),
    75.416.3 mm2 (range, 4994 mm2), and 76.023.1
    mm2 (range, 50123 mm2) for the interscalene,
    supraclavicular, midinfraclavicular, and
    subcoracoid regions
  • Differences in values between interscalene /
    supraclavicular and midinfraclavicular /
    subcoracoid regions were significant (Plt0.001)

13
(No Transcript)
14
Results
The ratio of neural to nonneural tissue in the
epineurium 454 (range, 4157), 484 (range,
4258), 346 (range, 2948), 343 (range, 30
39). These differences were significant (P
0.001).
15
Results
Absolute values (mm2) of adipose/connective
tissue compartment surrounding the brachial
plexus depicted per shoulder, from the most
proximal to the most distal area
16
Discussion
  • Why cryomicrotome technique ?
  • standard for allowing histologic examination
  • provides detailed information, which is currently
    superior to that of CT or MRI
  • high-resolution images and reconstructions we
    made with an interval of less than 0.1 mm allowed
    us to accurately demarcate and measure the
    contents of the brachial plexus within and
    outside the epineurium

17
Discussion
  • What is inside the epineurium ?
  • single nerve fibers enveloped by endoneurium,
    which are organized in bundles (fascicles)
    surrounded by perineurium
  • proximal (interscalene and supraclavicular)
    regions show a more solid, oligofascicular
    pattern
  • More distal, the fascicles show a more
    scattered, polyfascicular pattern

18
Discussion
  • Why penetration of the epineurial layer does not
    always lead to observed neural damage ?
  • The perineurium, in contrast to the epineurium,
    is a tough and mechanically resistant tissue. It
    is unlikely that a blunt needle will penetrate it
    easily.
  • polyfascicular configuration and relative
    increase in nonneural tissue more distally
  • higher incidence of neurologic dysfunction in
    proximal versus distal nerve blocks

19
Discussion
  • Injection inside the perineurium
  • high injection pressures
  • leads to fascicular injury and neurologic deficit
  • injection inside the epineurium
  • low initial pressures
  • return of normal motor function

20
Discussion
  • The neural tissue content of the brachial plexus
    remained approximately the same throughout the
    plexus
  • the ratio of neural to nonneural tissue decreased
    from a proximal value (interscalene /
    supraclavicular) of approximately 11 to a distal
    value (midinfraclavicular / subcoracoid) of
    approximately 12.
  • correlations with the onset time of brachial
    plexus

21
Discussion
  • To inject local anesthetic outside the epineurium
    ?
  • a larger mass of fat outside the plexus in the
    more distal regions of the plexus, which might
    serve as a reservoir for lipophilic local
    anesthetics
  • time needed to reach the neural tissue might be
    prolonged because less local anesthetic is
    available to diffuse across the epineurium to
    block the neural tissue
  • a requirement for larger doses of local
    anesthetic in the distal plexus

22
Limitations
  • number of specimens used is very small
  • The current study also does not take into account
    the elasticity of tissue in living patients
  • Further studies using the same manner of analysis
    after injection of stained solutions in the four
    brachial plexus approaches are recommended, as
    well as clinical imaging studies with local
    anesthetics to confirm our findings in vivo

23
Conclusion
  • Observed differences may explain why injections
    within the epineurium do not always result in
    neural injury
  • These differences also be a factor in determining
    the onset time and quality of blocks performed at
    different levels

24
  • Thanks for your attention !!
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