Neuraxial Anesthesia Flashcards
What can happen with degenerative disc disease?
It decrease the size of the intervertebral foramen, and can cause nerve compression
What is Batson’s plexus?
Network of epidural veins
Why do pregnancy and obesity decrease the epidural space?
Increased intraabdominal pressure puts back pressure on the epidural veins. This increases the blood volume in the epidural space and decreases the rest of the room within the space
The dural sac ends here
Adult = S2 (level of the superior iliac spines) Infant = S3
Anterior nerve roots carry
Motor and autonomic information
These fibers are NOT myelinated
C fibers
Order of types of fibers blocked
1- Autonomic
2- Sensory
3- Motor
Why is autonomic blockade higher than motor in spinals? How much higher?
Autonomic fibers are more sensitive to LA, so they get blocked with lower concentrations.
2-6 dermatomes higher
How much higher is sensory block than motor block in spinals?
2 dermatomes higher
Difference between motor block and autonomic block in epidurals?
There is none! They are at the same level
Difference between motor and sensory block in epidurals
Sensory is 2-4 dermatomes higher
Vasodilation that occurs with sympathectomy
Both arterial and venous, but MOSTLY VENOUS. Results in decreased venous return, decreased CO, decreased BP, etc.
Why might your healthy patient be c/o dyspnea after neuraxial anesthesia
D/t loss of chest proprioception
Why may you have drowsiness with neuraxial?
Because there is less input arriving to the RAS
Effect of neuraxial on GI system
Blocks SNS, but PSNS from CNX is unaffected and runs unopposed. Results in increased peristalsis and sphincter relaxation.
Why is full stomach a risk with neuraxial?
B/c the low BP from sympathectomy can cause N/V
MS and neuraxial
Looks like OK with epidural, but MS may slightly exacerbate with spinal. No real data to support this though. Explain risk of exacerbation to your patient.
Spec gravity of CSF
1.002-1.009
LAs in dextrose are hyperbaric, while those in water are hypobaric. What is the exception to this?
Procaine 10% in water is actually HYPERBARIC
Due to natural curvature of the spine, when a spinal is placed, LA pools and you get sensory block up to what dermatome?
T4
Absolute contraindications to Caudal anesthesia
Spina bifida
Meningomyelocele of the sacrum
Meningitis
This additive can provide analgesia that is equal to epidural opioids
Clonidine (1mcg/kg)
Any volume of bupiv, ropiv, or levobupiv may be used in peds as long as the total dose doesn’t exceed
2.5mg/kg
Where do neuraxial opioids affect pain transmission?
Substantia gelatinosa Lamina II of the dorsal horn
Effect of combining opioids with LAs
Denser block
Neuraxial opioids do NOT cause
Sympathectomy
Motor Block
Changes in proprioception
Most common SE of neuraxial opioids administration
Pruritis
Does benadryl work for neuraxial opioid itching?
No
Only narcan
Hydrophilic drugs and rest depression
Biphasic
Early (6 hours) due to tendency to rise towards the brain
Opioids and chlorprocaine
2-Chlorprocaine decreases efficacy of epidural opioids
Herpes and morphine
May reactivate HSV Type I d/t stimulation at the trigeminal nucleus
Opioids and breast milk
Minimal opioids is transferred from epidural space to breast milk
Examples of cutting needles
Pitkin
Green
Quinke
PDPH is more common in this population
Young, pregnant females
S/S of epidural hematoma
Weakness, numbness, lower back pain, and bowel and bladder dysfunction
Conus Medullaris ends at
Adults L1-2
Infants L3
For the dural SAC:
Adults S2
Infants S3
Cauda Equina Syndrome vs. Transient Neurologic Symptoms (TNS)
Cauda Equina
- NEUROTOXICITY d/t exposure to high concentrations of LA
- S/S = bowel and bladder dysfunction, sensory deficits, and weakness/paralysis ==> i.e. major nerve damage!
- Treatment is supportive (not much you can do)
TNS
- NOT from nerve toxicity ==> usually due to positioning, stretching of sciatic nerve, myofascial strain, and muscle spasm.
- Lidocaine and lithotomy position increases risk
- See severe back and butt pain that radiates to both legs
- Starts 3-36 hours after surgery, and lasts 1-7 days
- Treat with NSAIDS, opioids, and trigger point injections
Apnea after a spinal is generally due to
Cerebral hypoperfusion! (Blood pressure is too low!)
Level of cardiac SNS innervation
T1-4
Level of vascular SNS innervation
T1-L2
S/S of PDPH
Fronto-occipital HA, tinnitus, and N/V
How do you know when you have given enough blood for an epidural blood patch?
Once the patient starts to feel pressure in their back, buttocks, or legs
Organism that most commonly causes post-spinal bacterial meningitis
Streptococcus viridans
This is found in the mouth, and is why we wear masks during placement
Best disinfectant for neuraxial anesthesia
Combo of iodine and isopropyl alcohol
Lab cutoffs for neuraxial blocks
Plts 2x normal
