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81 Cards in this Set

  • Front
  • Back
Spinal, Epidural & Caudal anesthesia are known as _____ _______.
Neuraxial anesthesia
Spinal anesthesia is also known as __________ or ________.
Intrathecal or subarachnoid block
Where is the principle site of action for neuraxial anesthesia?
Nerve Root
Neuraxial anesthesia is appropriate for procedures that do not require mechanical ventilation or loss of sensory perception above ___ level.
T4 Level
The vertebral column is comprised of ___ vertebrae.

__ cervical
__ thoracic
__ lumbar
__ fused sacrala
__ coccygeal
33 vertebrae

7 cervical
12 thoracic
5 lumbar
5 fused sacral
4 coccygeal
Which parts of the vertebral column are convex toward the abdomen?
Cervical and Lumbar curve toward the abdomen
Thats why you tell people to push out their lower back when doing a spinal/epidural - to bring the spine closer to you.
Which parts of the vertebral column are convex toward the back?
Thoracic and sacral
What is scoliosis?
most common abnormal curvature of the spine.

lateral curvature of the spine
What is kyphosis?
usually occurs of the thoracic spine

excessive posterior curvature or hump
What is lordosis?
hollowing of the back

common in obese people and may occur temporarily during pregnancy in an attempt to restore center of gravity.
The spine is bound by what three ligaments in order from outmost to innermost?
Supraspinous ligament (outermost)
Interspinous ligament
Ligamentum flavum (innermost)
The supraspinous ligament is the outermost ligament and exends from ____ to ____.
Sacrum to C7
The epidural space is the potential space between the ligamentum flavum and the ______.
Dura Mater
Epi (of epidural) means ?
above the dura
The epidural space extends from the _________ to the sacral hiatus.
Foramen Magnum
The epidural space is widest at what space?
L2 (5-6mm)
Why is it important to stay midline when doing an epidural?
Veins of the plexus of batson are located lateral of the epidural space.
They are valveless and drain the spinal cord and linings of the cord.
When opioids are placed in the epidural space the (least/most) lipid soluble drugs like morphine have the greatest net transfer to the intrathecal space.
Least - meaning that they work the best.
Why are lipid soluble locals less effective?
Because they become sequestered in the fat. This is why lidocaine (although less potent) is more effective than Etidocaine which is more lipid soluble.
List the three connective tissue coverings of the spinal cord from outer to inner.
Dura mater (outermost) - tough & ends at S2

Arachnoid mater (middle) - delecate, nonvascular, closely attached to the dura, also ends at S2

Pia mater (innermost) - delicate, highly vascular, clings to the surface of the brain & cord.
The Pia mater extends to the tip of the spinal cord to become the filum terminal and anchors the cord where?
to the sacrum
Where is the subarachnoid space located?
between the arachnoid and pia mater
Describe CSF?
Clear, colorless ultrafiltrate of blood plasma.

It fills the subarachnoid space
What is the total CSF volume and how much of that is in the subarachnoid space?
100-150ml total
25-35ml in SA space
CSF is produced at a rate of ____ ml/day. Where is it produced?
450-500 ml/day

Produced in the choroid plexus in the lateral 3rd & 4th ventricles.
At birth the spinal cord ends at what level?
L3
By 24 months and into adulthood the spinal cord ends at what level?
L1 (L2 Nagelhout)
Below L1 the lumbar and sacral nerve roots that extend below the termination of the spinal cord are referred to as ____________.
The Cauda Equina (horse's tail)
The blood supply to the spinal cord and nerve roots is derived from _____ & _____.
single anterior spinal artery & paired posterior spinal arteries.
What level is the nipple line and what surgeries need this level of blockade?
T4

C-section, upper abdominal surgery
What level is the xyphoid and what surgeries need this level of blockade?
T6

Appy, lower abdomen (hernias, pelvic procedures)
What level is the umbillicus and what surgeries require this level of blockade?
T10

Vaginal/cervical procedures, hip and lower extremities
What level is the groid and what surgeries need this level of blockade?
L1

rectal procedures
What level is a Saddle block and what surgeries need this level of blockade?
S2-S5

Hemmorhoidectomy, perianal procedures
What is the difference between epidurals and spinals in terms of how they work?
Local used in epidurals must first diffuse out of the epidural space to reach the primary site of action, unlike intrathecal locals.
The spread of blockade is dependent on what factors?
Gravity
CSF pressure
Patient position
Volume of local
Baricity of local
Nerve fibers are blocked differently depending on their size and type of nerve fiber. Which one work the fastest?
Small, myelinated fibers are blocked faster than large unmyelinated fibers.
Large fibers are the most sensitive though
Explain the phenomenon of differential blockade.
The concentration of local anesthetic decreases with increasing distance from the site of injection.

Differential blockade refers to the difference in sympathetic, sensory, and motor blockade.
What is sympathetic blockade?
temperature sensitivity
Sympathetic blockade is generally ___ segments higher than Sensory blockade.
2-6 segments
Sensory blockade is ___ segments higher than motor blockade.
2-3 segments
True or False:
Differential blockade is seen most profoundly with spinal block.
True, it can also be seen with epidural blocks though
What is the most sensitive test of initial onset of blockade in neuraxial anesthesia?
Temperature
What is the most sensitive indicator of senory blockade in neuraxial anesthesia?
Pinprick
What is the most troublesome consequence of differential blockade?
A patient who has intact touch and proprioception at the surgical site but with loss of pain sensation.
Blockade of Efferent autonomic output at the spinal nerve roots can produce _____ & _______ blockade.
sympathetic and some parasympathetic blockade
Autonomic sympathetic outflow is referred to as ______ and exits the spinal cord at _______.
Thoracolumbar

T1 to L2
Autonomic parasympathetic outflow is referred to as ________ outflow.
craniosacral
True or False:

The vagus nerve is blocked by neuraxial anesthesia.
False
The physiology of autonomic blockade is a result of ??
It is a result of decreased sympathetic tone and/or unopposed parasympathetic tone.
Vasomotor tone is controlled by sympathetic fibers arisiong from ___ to ___.
T5 to L1

Blockade of these nerves causes vasodilation of the venous capacitance vessels, pooling of blood and decreased venous return to the heart
Arterial vasodilation with neuraxial anesthesia causes what?
Decreased SVR, which results in hypotension.
The decrease in blood return to the right atrium is sensed by stretch receptors and reflex bradycardia is seen.
What reflex is primarily responsible for bradycardia seen with neuraxial anesthesia?
Bainbridge Reflex

High neuraxial sympathectomy causes bradycardia
Where do the sympathetic cardiac accelerator fibers arise from?
T1-T4

Asystole has been reported after neuraxial administration probably due to unopposed vagal tone.
How much should you volume load a patient with to prevent cardiovascular complications?
10-20 ml/kg of crystalloid immediately prior to the block.
What will minimize obstruction of venous return in the vena cava during pregnancy?
Left uterine displacement in the third trimester
What is the first drug of choice for hypotension after neuraxial anesthesia in the pregnant patient? (unrelieved by fluids)
Ephedrine 5-10mcg. It indirectly causes vasoconstriction by release of norepinephrine.
Explain phenylephrine for hypotension with neuraxial anesthesia.
Phenylephrine is an alpha-agonist that causes increased venous tone and arteriolar vasoconstriction.
Dose cautiously in OB anesthesia.
Which patients would you want to reserve neuraxial anesthesia for when a level below T 7 is needed, not above that?
Chronic lung patients depend upon intercostal and abdominal muscles that will be affected by blocks above this level.
The patient would feel like that couldn't breath but yet they would be able to talk just fine and have adequate ventilation.
What nerve arises from C3-C5 and is not blocked even with total spinal or high cervical spinal? What is the significance of this?
Phrenic nerve. Thus respiratory arrest is a result of Brainstem hypoperfusion in the medulla.
What are results of neuraxial anesthesia having to deal with urinary, metabolic, and thermoregulation?
Bladder atony = urinary retention
Blocked stress response & can decreased circulation of catecholamines from respose of incision
Predisposed to hypothermia from vasodilation in legs especially if left uncovered.
What are some indications for neuraxial anesthesia?
full stomach
difficult airway (epidural may be safer-more control)
control post op pain
continuous local needed
As a primary anesthetic neuraxial blocks are most appropriate what surgeries?
lower abdomen
inguinal
urogenital
rectal
lower extremity
lumbar spine
What are 3 absolute contraindications for neuraxial anesthesia?
infection at site of injection
patient refusal
coagulopathy or bleeding diathesis
increased ICP
severe aortic or mitral stenosis (d/t vasodilation)
severe hypovolemia or shock
uncertain about length of procedure
What are 3 relative contraindications for neuraxial anesthesia?
sepsis
uncooperative patient
preexisting neurologic deficits
mild stenotic heart valves
severe spinal deformity
prior back surgery at the site of injection
inability to communicate with patient
complicated surgery
What are reasons for a failed block?
catheter migration
false LOR
spinal needle not completely in the subarachnoid space
unilateral block
Discuss Spinal hematomas
Rare but potentially devastating complication
Patient commonly presents with numbness or lower extremity weakness
Early detection is critical because a delay of more than 8hrs for spinal decompression reduces odds of good recovery
Coagulation defects are the greatest risk
Discuss Total spinal anesthesia
Usually occurs with inadvertent SA injection of local meant for epidural.
Must be prepared for intubation and CV support
Discuss Intravascular injection
Usually occur with epidural.
Aspiration and test dose must be used but can have false negatives and positives so incremental dosing should be used when activating an epidural.
What is the typical loading dose in mls for an epidural?

What is the max ml that should be placed in the SA space?
6-7ml loading dose for epidural

max 2cc in SA space
What causes a postdural puncture headache?
It is caused by a loss of CSF which causes decreased intracranial pressure and traction on structures supporting the brain.

It is usually obvious when CSF is dripping from the epidural needle, but it can occur with seemingly successful epidural if needle just scratched the dura.
What is the occurance rate for PDPH with spinals and epidurals?
20% in OB with large epidural needles

As low as 3% with spinals in OB
What factors increase the risk for getting a PDPH?
young age, female, pregnancy, cutting needle (especially large gauge)
What are the signs that a patient has a PDPH?
Bilateral, frontal, and occipital HA that extends into the neck
- worse with sitting or standing
- may be associated with nausea and photophobia
- onset usually 12-72hrs later but may be immediate
What is the treatment for a PDPH?
conservative: bedrest in supine position with adequate hydration and oral analgesia. caffeine 300mg oral or 500mg IV in 1L of fluid over 2hrs

Epidural blood patch
How do you do a epidural blood patch?
With sterile technique place IV and withdraw 15-20ml of blood and inject into epidural space. stop if pain occurs, have patient remain flat for 2hrs

Relief rate reported as high as 100% but can be repeated in 24hrs one time if needed then neuro consult if not relieved.
Discuss what you would do if you have a retained epidural catheter.
It occurs by either breaking or unraveling of the catheter. If the catheter is difficult to remove stop and allow the patient to relax for an hour or so, may even wait until the next day.
Place in lateral position and try again. If unable. Call radiology and try under fluroscopy.
If the catheter unravels or stretches call radiology.
If the catheter breaks beneath the skin most sources recommend leaving the retained catheter if no portion is exposed to the outside.
Discuss a high block and the symptoms.
High block can happen with either epidural or spinal blocks when excessive doses are given or when patient is extremely sensitive.
Symptoms: dyspnea, numbness or weakness in upper extremities, nausea often proceeds hypotension.
What are transient neurological symptoms?
(TRI) Transient radicular irritation

Back pain radiating to the legs which resolves usually within 72hrs but some patients have had pain for up to 6months.
What are transient neurological symptoms associated with?
Almost all locals and most common with outpatient surgery, lithotomy position, and high concentrations of locals

Studies have shown increase risk with lidocaine
What is Lidocaine Neuotoxicity or Cauda Equina Syndrome?
Characterized by bowel and bladder dysfunction, paralysis of legs, sensory deficits and pain with evidence of multiple nerve root injuries.

Associated with continuous spinal catheters and 5% lidocaine but has been reported with single shot lidocaine

Take home message lidocaine spinals not always a good idea