Spinals part 2 Flashcards
in what order are nerve fibers sensitive to LA? (most sensitive to least sensitive)
in what order are they blocked? (first to last)
large myelinated > smaller myelinated > smaller unmyelinated
B fibers
C and A-Delta fibers
larger A-gamma, A beta, and A-alpha fiberes
what do B fibers do?
preganglionic sympathetic efferents
what do C and A-delta fibers do?
pain, temp, touch afferents
post ganglionic sympathetics
factors that affect differential blocks?
size/myelination of the fibers
nodes of ranvier
location depth
Na and K channels on each nerve
in waht order are the nervous systems blocked?
sympathetic, sensory, motor
sings of a sympathetic block? and how to sympathetic, sensory, and motor block levels compare?
BP changes may be the first sign, and is usually 2 segments higher than the sensory block, which is usually 2 levels higher than a motor block
most accurate way to check for sensory block?
sharp or broken tongue depressor
is loss of sensation to cold or sharp pain first?
sesation to cold is first and occurs at higher levels
what fibers are blocked first in motor blockade?
A beta and A gamma, A alpha is a profound block
2 most important factors that affect height of nerve block for SAB?
baricity and patient position
how do you get a saddle block? what is it good for?
sitting position for SAB, leave sitting for 3-5min with a hyperbaric solution. Great for lower perineal procedures
how does LA distribute in position is sitting to supine with hyperbaric solution?
it moves more cephalad to the dependent region of the lumbar curve
spine high points in cervical and lumbar lordosis?
C3 and L3
spine low points in thoracic and sacral kyphosis?
T6 and S2 low points
other factors affecting height of spinal block?
age - older ligamentum flavum gets tougher and intrathecal space gets compressed, so higher spread of LA
height, more distance to travel and can increase dose
weight, decrease in intrathecal and epidural space if obese or pregnant
spinal fluid rate of circulation (coughing and straining)
hypobaric LAs?
tetracaine 0.33% with water
lidocaine 0.5% with water
isobaric LAs?
tetracaine 0.5% with 50% CSF
lidocaine 2% with water
bupivicane 0.5% with water
hyperbaric LAs?
tetracaine 0.5% with 5% dextrose
lidocaine 5% with 7.5% dextrose
bupivicane 0.5% with 8% dextrose
bupivicaine 0.75% with 8% dextrose
primary goal of neuraxial anesthesia?
block afferent fibers located in dorsal roots
motor and sympathetic fibers are close and they get blocked as they pass through ventral root
why must you use preservative free LA in SAB?
parabns high allergy potential
sulfites neurotoxic
EDTA muscle pain and can cause tetany
should you use multi dose or single dose vial for SAB?
single dose
mech of action of LA?
limits sodium cahnnels and stops propogation of a nerve impulse
which LA has strongest attachment to NA channels?
bupivicaine
how do LAs find their way to the spinal cord?
through virchow-robin spaces
insertion site of tiny blood vessels where local can get around the side of them
which meds can increase duration of SAB? what dose for each?
epi 0.1-0.2ml of epi 1:1000 “epi wash”
Neo 0.5-2mg
clonidine (LA effect)
what is added to LA to increase onset?
NAHCO3
where are opiod receptors?
substantia gelatinosa and spinal cord
what meds are MU opioid receptors responsive to?
morphine, meperidine, sufentanil, fentanyl, alfentanil
What are MU2 receptors also responsible for?
decreased HR, RR, and euphoria
SE of opioids?
N/V, itching, urinary retention
N/V is the number one complaint
why is fentanyl widely used?
it adheres to lipoproteins in the spinal cord due to its high lipid solubility, less drug available to diffuse to respiratory centers
fentanyl dosing in SAB? what can it be combined with?
10-25mcg
onset 5-10min
DOA 2-4hours
can be combined with morphine (must be preservative free)
morphine dosing in SAB
0.1-.5mg
onset 60-90min
DOA 6-8hrs
what should you be cautions with when using morphine in SAB?
delayed resp depression
adequate dermatome levels for the following procedures?
upper abdmonial surgery
intestinal, gyn, urologic
TURP
vaginal delivery, hip surgery
thigh surgery and lower leg amputation
foot and ankle surgery
perineal and anal surgery
T4
T6
T10
T10
L1
L2
S2-S5 (saddle block)
needle size for spinals?
22-27 gauge
is quinke point needle cutting?
yes
is whitacre needle cutting?
no, pencil point
line accross iliac crests?
Tuffiers line
spinal considerations in prone jacknife positions?
use hypobaric or isobaric
must aspirate CSF, it will not drip
rectal procedures
what do you need to make sure happens with legs in the lateral position?
good flexion of the legs
why is potential lumbar spine rotation importnat?
it may impede access to the spinal canal
what LA is typically used for jack knife position?
tetracaine with water
caudal anesthesia can also be used, this is part of epidural space with a space in the sacral hiatus
what size spinal needles need an introducer?
25-27 gauge
what size needle no longer needs an introducer?
22gauge
which way should bevel face on introducer needle for paramedian approach? midline?
up (why???)
to the side
what structures are passed through for subarachnoid block in midline position? lateral or paramedian approach?
skin
subq tissue
supraspinous ligament
interspinous ligament
ligamentum flavum
epidural space
dura matter
arachnoid matter
lateral or paramedian approach does not pass through the supraspinous or interspinous ligaments
how often should BP cuff be set when starting a spinal?
every 2 min
when is paramedian approach done and how is it done?
for patients unable to flex and arch their back. also for paties who are belived to have calcified ligaments, or after a couple attempts at midline
walk laterally 1-2cm from spinous process as well as 1cm down, angle 45 degrees cephalad and 15 degress to midline. first resistance should be ligamentum flavum
describe taylor approach
indications: difficult anatomy, kyphoscoliosos, scoliosis
it is a modified paramedian appraoch, but done at L5-S1 interspace
pros of SAB?
fast acting
dense block - motor and sensory
small volume minimzes toxicity
less time and smpler to perform
less N/V, decreased stress response, decreased opioids
affects reticular activating system so pt can be somnolent
cons of SAB?
hypotension is significant
cant prolong the block
lack of control with the level of the block
