Regional Anesthesia Flashcards
major contraindications for neuraxial anesthesia (6)
- patient refuse
- bleeding diathesis
- hypovolemia
- elevated ICP
- infection at site of injection
- severe stenotic valvular heart disease or centric outflow obstruction
reduction of SVR from neuraxial anesthesia ok with WHAT cardiac lesions?
regurgitant
what object is continuous cephalic with the brainstem through the foramen magnum?
SUBarachnoid
where does the spinal cord terminate distally?
conus medullaris
distal termination of spinal cord in INFANTS is where?
L3
distal termination of spinal cord in ADULTS
lower border of L1
subarachnoid space terminates distally to what level?
S2
subarachnoid space also known as?
intraTHECAL space
what accounts for 80% of variability in PEAK BLOCK HEIGHT and REGRESSION of sensory and motor blockade
CSF volume
PRIMARY tissue layer that serves as primary (90%) barrier to epidural drugs diffusing into the intrathecal space?
Arachnoid mater
2 mechanisms of EPIDURAL anesthesia:
1) drug translocation into thecal space
2) drug can anesthetize the nerve roots laterally
which layer covering the spinal cord is HIGHLY vascular
pia mater
Why do patients with High spinals become apneic (resp arrest)?
dropped pressure so much that brainstem isn’t perfused (NOT bc you blocked phrenic nerve)
epidural space bound ANTERIORLY by?
posterior longitudinal ligaments
epidural space bound laterally by?
pedicles
posterior boundary of epidural space?
ligamentum flavum
spinal epidural space extends from where to where?
foramen magnum to sacral hiatus (and by virtue of the posterior aspect, the ligamentum flavum does, too)
what VENOUS plexus included in the epidural space?
BATSON venous plexus
posterior to the Ligamentum flavum?
INTERSPINOUS LIGAMENTs
posterior to the INTERSPINOUS ligament?
Supraspinous ligament
Rexed lamina layers in gray matter of spinal cord NOT involved in NOCICEPTION transmission?
FOUR (mechanoreceptors)
1,2,5 keep the pain alive
two types of spinal needles?
1) cut dura
2) conical tip
needles that cut the dura?
Quincke-Babcock
traditional disposable needle
needles that have conical tip (pencil-point)?
Whitacre and Sprotte
what’s benefit of using conical-tipped needle?
decrease in incidence of post-dural puncture headache
what things can DECREASE incidence of PDPH?
- small needles
- less punctures of dura
which spinal anesthetic (used less frequently than lido) for shorter spinal anesthesia? for what THREE reasons?
Procaine (
for what THREE reasons was Procaine used less frequently?
- higher NAUSEA
- higher ANESTHETIC failure rate
- Slower time to recovery
what is one reason some STILL USE procaine vs lidocaine?
lower frequ of back and leg pain after its use
transient neurologic symptoms are what?
back and leg pain following “-caine” use in spinals
NOT neurologic; NO focal neurologic pain; NOT dermatome-specific
what’s LONG-acting ester spinal anesthetic used?
tetracaine
what vasoconstrictor can be used with tetracaine to make it EVEN LONGER lasting?
- epi (2-3hrs)
- PHENYLEPHRINE (5 hours!!!)
Ultrasound beam frequency versus depth and resolution?
HIGH FREQUENCY - better resolution; less penetration; good for shallow structures
(Deeper needs lower frequency….more than 5cm deep; but get lower resolution)
reflected sound waves produce
hyperechoic if bounced back; highly reflected tissue
sound waves hypoechoic = tissue not strongly reflect; DARKER on u/s
bones on US?
dark, acoustic shadow, bone doesn’t absorb many of the sound waves - they’re reflected, so surface may be hyperechoic
nerves on US?
- individual peripheral nn fibers bundled together in ____?
- -those fibers bundles together into _____ by _____
- –multiple fascicles bundled together by ______
HYPERECHOIC; honey-comb interior
- endoneurium
- -fascicles covered by connective tissue called perineurium
- –Epineurium
fascicles covered by?
fat, connective tissue, and small vessels; THEN covered by Epineurium around this bundle
majority of nerves appear with
hyperechoic perineurium
how is an ultrasound image formed?
electricity applied to a Piezoelectric element in a TRANSDUCER –> vibrates –>emits sound waves –>waves reflected back detected by transducer and converts sound energy into electric signal
how fast is transmission/reception cycle repeated in U/s?
7,000 times/second
how does U/S ENERGY relate to impedance of tissue?
Amount of sound energy reflected PROPORTIONAL to difference in acoustic impedance between the tissues (different acoustic impedance, reflects differently, but proportionally)
higher frequency affects wavelength how?
SHORTER wavelength
frequencies good for less than 5cm?
8-20 MHz
frame rate of U/S machine has what effects?
if SLOW –>system not able to produce images to keep up with movement of probe
what can decrease frame rate of U/S?
- adding color Doppler
- increasing number of focal zones
what is the energy loss from sound waves penetrating tissue?
ATTENUATION
what is sound energy converted to?
heat
common attenuation of BONE (relative to h2o)?
10,000x
attenuation of air (relative to h2o)?
5,000x
attenuation of muscle(relative to h2o)?
500x
attenuation of blood (relative to h2o)?
100x
water–>blood–>muscle–>air–>bone
100, 500, 5000, 10000
best angle of u/s reflection for getting sound energy back to transducer (probe)
90-degree (perpendicular)
which type of angle reflects MOST away from probe?
acute angles
What is anisotropy?
angle of sound wave and its effect on the reflection – causes some structures to be VERY sensitive to position of transducer
what is the angle at which sound waves strike the surface?
Angle of insonation
which color are objects moving TOWARDS the transducer?
RED (towaR[e]d)
color of objects moving AWAY from U/S?
Blue - has U - up up, and AWAY
