Spinal Anatomy and Nerve Flashcards
For patients that were receiving therapeutic doses of LMWH, wait_____hours after the last dose before neuraxial procedure
24
For patients that were receiving prophylactic doses of LMWH, wait_____hours after the last dose before neuraxial procedure
12
After performing a neuraxial procedure, when can you restart LMWH?
24 hours after needle insertion for full dose (Or 48-72 for high bleeding risk surgery)
OR 12 hours for ppx dose
If a neuraxial procedure was performed with catheter in place
DO NOT give full dose or BID ppx LMWH with catheter in place ; one may give daily ppx 12 hours after needle insertion.
When may one safely remove catheter after daily LMWH ppx dosing?
12 hours after
After removal of catheter, when to start LMWH?
with ppx dosing, 4 hours after removal; for full dose wait 4 hours or 24 hours after needle placement
dural sac terminates?
S1-S2
conus medullar is terminates?
L1-L2 (so spinal anesthetics are administered L2-L4)
The dura mater is the toughest and outermost layer. In neonates the dura extends to ____, however this also moves more cephalad as a person ages so that it terminates around ___ in a normal adult.
S3; S1-S2
The arachnoid mater also extends to ___ along with the dural sac.
S1-S2
When performing a spinal blockade in an adult, the iliac crest is commonly used as a landmark as it generally corresponds to the level of the ______
L4 interspace (Tuffier’s line)
Spinal anesthesia in an adult is generally administered at the ______interspace as this avoids the spinal cord, yet is still above the level at which the dural sac terminates.
L3-4 or L4-5
conus medullaris ends at ____in adults
L1-L2
conus medullaris ends at ____in newborns.
L3-L4
dural sac ends at _____in newborns
S3-S4
axillary nerve block but is still able to flex their arm at the elbow.
Musculocutaneous was not blocked!
Musculocutaneous N provides innervation to _____muscle and flexion at_____?
biceps; flex at elbow
where does musculocutaneous nerve lie?
laterally between the fascial planes of the biceps brachii and coracobrachialis muscle
intercostobrachial nerve originates from?
T2
when is intercostobrachial nerve indicated?
upper arm tourniquet is required and would not be successful with any brachial plexus block technique.
elbow and wrist extension?
radial N.
addition of bicarbonate to ropivacaine or bupivacaine can cause ?
precipitant to form in solution
Often bicarbonate is added to local anesthetic (often in a 1:10 ratio) to increase the pH of the solution. This increase of pH decreases pain on injection into peripheral tissues and also speeds the onset time of the local anesthetic by increasing the unionized portion of local anesthetic
Lidocaine remains relatively soluble in its unionized form. However ropivacaine and levobupivacaine are not, and therefore it is not recommended to have bicarbonate added for infusion
nerve fiber is responsible for the fastest transmission of nociception?
A- delta fibers “Delta airplane”
fibers responsible for transmission of nociception?
Type A-delta fibers and C fibers
conduct proprioception and motor
A-alpha
transmit mechanical information and information from Meissner corpuscles and Merkel disks. touch and pressure
Type A-beta
Muscle spindles and tone
Type A gamma
two fibers responsible for nociception/pain?
A delta and type C dorsal
Differential blockade begins with
B fibers, then A, then C. Recovery is in reverse order.; *A mnemonic for differential blockade is “Sympathetic People Matter”: Sympathetics > Pain > Motor for neuraxial blockade levels.
For neuraxial blocks,________ nerve fibers are blocked by the lowest concentration of local anesthetic followed by nerve fibers responsible for pain/touch and finally motor function.
sympathetic
slowest conduction velocity and are not sensitive to nerve blockade as they are unmyelinated.
C fibers
epidural anesthesia may cause?
increased peristalsis=> Tonic inhibitory sympathetic control (T6-L2) predominates, but parasympathetic activation increases contractility. Therefore, sympathectomy induced by epidural or spinal analgesia results in increased gut motility (B), especially those involving epidural catheter placement at T12 or higher.
Sympathectomy induced by epidural anesthesia results in _______, especially those involving epidural catheter placement at T12 or higher.
increased peristalsis
Tx for N/V caused by spinal?
nopposed parasympathetic (vagal) activity after sympathetic blockade causes increased peristalsis of the gastrointestinal tract, which can lead to nausea. For this reason, atropine is nearly universally effective in treating nausea associated with neuraxial blockade. G
At which of the following spinal levels does the great radicular artery MOST commonly originate?
T9-T12
Spinal Cord Perfusion Pressure (SCPP) = ?
= MAP - Intrathecal Pressure or CSF pressure (SCPP = MAP - CSF pressure). The two most common ways to improve SCPP during aortic surgery are to increase the MAP and reduce CSF pressure using a lumbar CSF drain.
CPP =
MAP - ICP applies to the spinal cord and the principle remains the same as intracranial hypertension.
Blood supply to the _______ of the spinal cord (wherein the motor tracts are located) is provided by the SINGLE anterior spinal artery (ASA)
anterior two-thirds
what is ASA syndrome?
irreversible spinal cord damage, paraplegia, and loss of bowel and bladder function,
tx of ASA syndrome?
SCPP can be increased by increasing MAP > 90 mm Hg through the administration of vasopressors and reducing CSF pressure < 10 mm Hg by CSF drainage.
Blood supply to the posterior _____of the spinal cord is provided by the TWO posterior spinal arteries (PSA)
1/3
ASA= motor PSA= ?
sensation and proprioception in the dorsal columns.
which artery gives rise to the single ASA?
vertebral!
which artery gives rise to the PSA?
posterior inferior cerebellar arteries from the vertebral arteries give rise to two PSAs.
In ASA syndrome what is preserved?
In anterior spinal artery syndrome, there is loss of motor, temperature, and pain function. Proprioception and vibratory senses are preserved.
pain and temp
(lateral spinothalamic tract)
corticospinal tract
motor
3 mechanisms for Subarachnoid anesthesia causing hypotension???
1- arterial dilation 2/2 loss of sympathetic tone
2-venodilation
3-bradycardia- higher blocks are associated with brady (cardiac acc fiber T1-T4); parasympathetic dominance and/or the Bezold-Jarisch reflex
Bezold-Jarisch cardiovascular reflex
parasympathetic-mediated reflex occurs when stretch receptors located mainly in the left ventricle respond to an acute decrease in left ventricular preload. The result is bradycardia and reduced contractility (and resultant hypotension). This reflex is thought to occur to allow the ventricle additional time to fill and increase preload
carotid sinus baroreceptor response to hypotension
increased heart rate and contractility
best nausea treatment after HIGH SPINAL?
atropine
RFs for N/V after spinal?
high block (above T5), hypotension, opioid administration, and a history of motion sickness