Neuraxial blocks Flashcards
How many cervical vertebrae are there?
7
How many thoracic vertebrae are there?
12
How many Lumbar vertebrae are there?
5
How many sacral vertebrae are there?
5~fused
How many coccygeal vertebrae are there?
4~fused
What is the vertebral foramen?
Space that contains the spinal cord, nerve roots, and epidural space
What is vertebrae C1 also called?
The atlas
What is vertebrae C2 also called?
The axis (this vertebrae has the dens!)
What is another name for the facet joint?
Zygapophyseal joint
Where is the vertebra prominens?
C7
Where is the SPINE of the scapula?
T3
Where is the Inferior angle of the scapula?
T7
At what level is the rib margin?
L1
At what level is the iliac crest?
L4
At what level is the posterior iliac spine?
S2
What is another name for the intercristal line?
Tuffier’s line ~ correlates with L4 vertebra
Where is the sacral hiatus?
S5
Covered by the sacrococcygeal ligament
Entry point to the epidural space in pediatrics
What are the sacral Cornu?
Bony nodukes that flank the sacral hiatus
Where does the spinal cord end in an adult (aka conus medullaris)?
Adult: L1-L2
Where does the spinal cord end in the infant? (Aka conus medullaris)
L3
What is the cauda Equina?
Bundle of nerve fibers extending from conus medullaris to Duran sac
Where does the Dural sac terminate in the adult?
S2
Where does the dural sac terminate in the infant?
S3
What is the film terminale?
Continuation of pia mater that extends from the conus medullaris to coccyx
Anchors spinal cord to coccyx
What is the order of the five ligaments in the spinal column? From outside in…
Supraspinous
Interspinous
Ligamentum flavum
Posterior longitudinal ligament
Anterior longitudinal ligament
What ligaments does the needle pass in the midline approach?
Supraspinous
Interspinous
Ligamentum flavum
What ligaments does the needle pass in the paramedical approach?
Ligamentum flavum
What are the 3 meninges layers of the spinal cord? From outside in?
DAP
Dura
Arachnoid
Pia
What is the cranial border, caudal border, anterior border and posterior border of the epidural space?
Cranial (top) foramen magnum
Caudal (bottom): sacrococcygeal ligament
Anterior: posterior longitudinal ligament
Posterior: ligamentum flavum
How does the epidural space affect lipophilic drugs?
Acts as a sink reducing bioavailability
(Bupi > Lido > morphine)
What is another name for the epidural veins?
Bataan’s plexus
They pass the anterior and lateral regions of the epidural space
**pregnancy and obesity increase intraabdominal pressure and cause engorgement of these vessels
What is the plica mediana dorsalis?
Hypothetically…this is a band of tissue that courses b/t the ligamentum flavum and dura mater.
** been considered the culprit for difficult epidural catheter insertion
What is a tough fibrous shield that protects the spinal cord?
Dura mater
What is a potential space b/t the dura mater and the arachnoid mater?
Subdural space
What is a thin layer of connective tissue that neighbors the dura mater?
Arachnoid mater
Which space is deep to the arachnoid mater and contains CSF, nerve roots, and the spinal cord?
Subarachnoid space
What is the external covering of the spinal cord?
Pia mater.
What does C6 innervate?
1st digit (thumb)
What does C7 innervate?
2nd and 3rd middle digits
What does C8 innervate?
4th and 5th digits
What does T4 innervate?
Nipple line
What does T6 innervate?
Xiphoid process
What does T10 innervate?
Umbilicus
What does T12 innervate?
Pubic symphysis
What does L4 innervate?
Anterior knee
What sensory level is necessary for an upper abd surgery, c-section, or cystectomy?
T4
What sensory level is necessary for a lower abdominal surgery/appendectomy ?
T6-T7 (xiphoid process)
What sensory level is necessary for a total hip arthroplasty, Vaginal delivery, or TURP
T10
What sensory level is necessary for a lower extremity surgery?
L1-L3
What sensory level is necessary for a foot surgery?
L2-L3
What sensory level is necessary for a hemorrhoidectomy?
S2-S5
What are some controllable factors for spinal anesthesia?
Baricity
Patient position
Dose
And Site of injection
What are some controllable factors for epidural anesthesia?
Local anesthetic volume (most imp.)
Level of injection
Local anesthetic dose
How does the level of injection affect the spread in epidural anesthesia?
Lumbar: cephalon
Midthoracic: both cephalon and caudad
Cervical: caudad
In spinal anesthesia, what is the sensory blockade, what is the autonomic blockage and what is the motor blockade?
Sensory: usually 2 dermatomes ABOVE motor
Autonomic: usually 2-6 dermatomes ABOVE sensory
Motor: usually 2 dermatomes BELOW sensory
In epidural anesthesia, what is the sensory blockade, what is the ANS blockade, and what is the motor blockade?
Sensory and ANS are 2-4 dermatomes ABOVE motor
What is the first sensory modality blocker? What is the second? What is the last?
1st: sense of temperature
2nd: pain
3rd: sense of light touch or pressure
Where is the primary site of action of a spinal anesthetic?
In the subarachnoid space ~ myelinated preganglionic fibers of the spinal nerve roots
For a spinal anesthetic, what is the dose of bupivaciane at the T10 level and what is the dose at the T4 level?
T10: 10-15mg
T4: 12-20 mg
For a spinal anesthetic, what is the dose of Levobupivacaine at the T10 level and what is the dose at the T4 level?
T10: 10-15 mg
T4: 12-20 mg
For a spinal anesthetic, what is the dose of ropivacaine at the T10 level and what is the dose at the T4 level?
T10: 12-18mg
T4: 18-25 mg
For a spinal anesthetic, what is the dose of Chloroprocaine 3% at the T10 level and what is the dose at the T4 level?
T10: 30-40 mg
T4: 40-60 mg
For a spinal anesthetic, what is the dose of tetracaine at the T10 level and what is the dose at the T4 level?
T10: 6-10 mg
T4: 12-16 mg
What is the initial dose per segment to be blocked in an epidural?
1-2 mL per segment
What is a “top up” dose?
50-75%
What is the difference b/t specific gravity and baricity?
Both are the density of a substance relative to a substance
Specific gravity = water
Baricity = CSF
What is an isobaric solution?
Baricity is similar to CSF
What is a hyperbaric solution?
Baricity is greater ~ higher density > 1
Dextrose is added to increase Baricity
What is a hypobaric solution?
Baricity is lower ~ lesser density < 1
Water is added to reduce Baricity
Which is the only solution that is hyperbaric in water?
Procaine 10% in water (there are a lot of molecules in procaine)
What are the highest points of lordosis in the supine position?
L3
C5
What are the high points of kyphosis in the supine position?
T5-T7 and S2
What can occur if you have unloading of the ventricular mechanoreceptors?
Activation of the Bezold-Jarisch reflex (this can lead to asystole with spinal anesthesia
How does neuraxial anesthesia affect the resp system?
Accessory muscle function is reduced. ~this can reduce pulmonary reserve.
What is usually the culprit if a patient becomes apneic with neuraxial anesthesia?
Brainstem hypoperfusion.
How does neuraxial anesthesia affect the CNS?
Reduces sensory input to the reticular activating system ~ causes drowsiness
How does neuraxial anesthesia affect the Neuro endocrine system?
Inhibits afferent traffic and diminishes the stress response
How does neuraxial anesthesia affect the GI system?
Relaxes sphincters and increases peristalsis
What do opioids NOT cause in spinal or epidural anesthesia?
Sympathectomy
Skeletal muscle weakness
Changes in proprioception
What are some traits about hydrophilic drugs administered in the intrathecal/epidural administration?
Spread: extensive (more rostral spread)
Wider band of analgesia
Site of action: rexed laminae II and 3
Onset: 30 mins
Duration: 6-24 hours
**resp depression (early < 6 hrs; late > 6 hrs)
N&V: increased
Pruritus: increased
What are some traits about lipophilic drugs that are administered in the epidural and spinal space?
Spread: stays in CSF for shorter period of time (less rostral spread)
Narrow band of analgesia
Site of action: rexed laminae 2 and 3/systemic
Onset: 5-10 mins
Duration: 2-4 hours
Resp depression: early
N&V: less
Pruritus: less
What is the intrathecal dose and epidural dose of sufentanil?
Intrathecal: 5-10 mcg
Epidural: 25-50 mcg
What is the intrathecal dose and epidural dose of fentanyl?
Intrathecal: 10-20 mcg
Epidural: 50-100 mcg
What is the intrathecal dose and epidural dose of hydromorphone?
Intrathecal: ~
Epidural: 0.5-1 mg
What is the intrathecal dose and epidural dose of meperidine?
Intrathecal: 10 mg
Epidural: 25-50 mg
What is the intrathecal dose and epidural dose of morphine?
Intrathecal: 0.25 - 0.30 mg
Epidural: 2-5 mg
What is the most common side effect of neuraxial opioid administration?
Pruritus
Then resp depression > urinary retention > N&V
Why do opioids cause Pruritus?
Stimulation of opioid receptors in the Trigeminal nucleus
**must be treated with an opioid antagonist, such as naloxone
How does neuraxial opioids cause urinary retention?
Inhibition of sacral parasympathetic tone ~ bladder detrusor muscle relaxation and urinary sphincter muscle contraction
How do opioids cause N&V?
Activation of opioid receptors in the area posted a of the medulla and vestibular apparatus
What can epidural morphine reactivate?
Herpes
Which local anesthetic reduces the efficacy of epidural opioids?
2-Chloroprocaine
What is ALWAYS an absolute contraindication to neuraxial anesthesia?
Patient refusal
At what platelet count would a neuraxial technique be contraindicated?
<100,000
Which anesthetic technique is preferred for a patient with MS?
Epidural is relatively safe, but intrathecal may exacerbate symptoms
What 3 vascular lesions are generally considered contraindications for neuraxial anesthesia?
Severe Aprtic stenosis
Severe Mitral stenosis
Hypertrophic cardiomyopathy
What is an example of a cutting needle?
Quincke
(Requires less force)
What are two examples of a pencil point needle?
Sprotte
Whitacre
What are the pros of a cutting needle? What are the cons?
Pros: requires less force
Cons: higher risk of PDPH, less tactile feel, needle more easily deflected, more likely to injure nerve roots
What are the pros of a pencil point? What are the cons?
Pros: lower risk of PDPH, more tactile feel, needle less likely to deflect, less likely to injure nerve roots
Cons: requires more force
How are epidural needles differed?
By the amount of curvature at the needle tip
Needle angle increases in alphabetical order
Crawford ~ 0
Hustead ~ 15
Tuohy ~ 30 degrees
How deep is the epidural space in most adults?
3-5 cm from the skin.
What are absolute contraindications to caudal anesthesia?
Spina bifida
Meningomyelocele of the sacrum
Meningitis
What are the two landmarks for a caudal anesthetic?
Posterior superior iliac spines and the sacral hiatus
What is the dose for a caudal anesthetic that goes to the sacral height?
Peds: 0.5 mL/kg
Adult: 12-15 mL
What is the dose for a caudal anesthetic that goes from the sacral to low thoracic (~T10)?
Peds: 1 mL/kg
Adults: 20-30 mL
What is the dose for a caudal anesthetic that goes from sacral to mid thoracic?
Peds: 1.25 mL/kg (this should be avoided though)
What are some common pediatric procedures where a causal is useful?
Circumcision
Hypospadias repair
Anal surgery
Inguinal hernia
Low thoracic surgery
What are the presenting symptoms of an epidural hematoma?
Lower extremity weakness
Numbness
Low back pain
Bowel and bladder dysfunction
If a patient has an epidural hematoma, how soon should surgical decompression be initiated?
Within 8 hours!!
How long should you hold COX-1 inhibitors prior to neuraxial block?
Examples: asa, NSAID
Management: none of labs look ok.
How long should you hold a glycoprotein IIb/IIIw antagonist?
Example: tirofiban, eptifibatide, abciximab
Management:
Before block: hold tirofiban and eptifibatide 4-8 hrs; hold abciximab 24-48 hours
(Contraindicated within 4 weeks of surgery)
How long should you hold a thienopyridine derivative?
Examples: clopidogrel, prasugrel, ticlopidine
Before block:
5-7 days with Clopidogrel
7-10 days with prasugrel
10 day hold ticlopidine
How long should you hold heparin for a neuraxial block!?
Before block:
Low dose (5,000) ~ hold 4-6 hours
Higher dose (< 20,000) ~ hold 12 hr
Therapeutic dose (>20,000) ~ hold 24
May restart heparin after 1 hour
How long should you hold heparin after removal of neuraxial catheter?
SubQ ~ hold 4-6 hours
IV ~ hold 4-6 hours after IV infusion discontinued.
(After catheter removal ~ restart in 1 hour)
How long should you hold low molecular weight heparin (lovenox) for neuraxial anesthesia?
Before block placement:
Prophylactic: hold for 12 hours
Therapeutic dose: hold for 24 hours
(After block placed, delay first dose by 12 hours after block)
How long should you wait for catheter removal with a patient on low molecular heparin (lovenox)
Catheter removal:
Remove before lovenox if possible or delay first dose 4 hours after removal
Otherwise remove 12 hours after last dose and HOLD next dose for at least 4 hours
How long should you hold for a patient taking warfarin requesting neuraxial anesthesia?
Before block
Hold: 5 days
Catheter removal: wait until INR < 1.5
How long should you hold for a patient taking oral anti-factor 10a agents requesting neuraxial anesthesia?
Before block:
72 hrs (3 days)
Catheter removal: must wait 6 hrs prior to first postoperative dose
What is an ABSOLUTE contraindication to neuraxial anesthesia?
Thrombolytic agents
What causes a post-dural puncture headache?
As CSF pressure is lost, cerebral vessels dilate, the brain stem sags into the foramen magnum and stretches the meninges and pulls on the tentorium
What are some patient factors that increase the risk for PDPH?
Younger
Female
Pregnancy
What are some practitioner factors?
Cutting tip needle
Larger diameter needle
Using air for LOR
Needle PERPENDICULAR instead of parallel
What is the treatment for PDPH?
Bed rest
NSAIDs
Caffeine
Epidural blood patch (the DEFINITE treatment)
Sphenopalatine ganglion block
What is the most common side effects following epidrual blood patch?
Backache and radicular pain
What are the two routes by which an infectious organism can reach the CSF?
Failure of aseptic technique
Bacteria in the patient’s blood at the time of SAB
What is the most common bacteria for post-spinal meningitis?
Streptococcus
What is the MOST effective way to prevent post-spinal bacterial meningitis?
Alcohol and chlorhexidine
What is cauda equina syndrome?
Neurotoxicity as result to high concentrations of local anesthetic
What factors increase the risk of cauda equina syndrome?
5% lido
Spinal microcatheters
What are the signs and symptoms of cauda equina syndrome?
Bladder and bowel dysfunction
Weakness
Sensory deficits
Paralysis
Treatment: supportive
What is transient a Neurological Symptom?
Usually develops because of patient positioning, stretching of the sciatic nerve, myofascial strain, and/or muscle spasm
What factors increase the risk of transient neurological symptoms?
Lidocaine, lithotomy, ambulatory surgery, and knee arthroscopy
What are some signs and symptoms of transient neurological symptoms?
Severe back and butt pain that radiates to both legs
Develops within 6-36 hours and lasts 1-7 days
What is the tx for transient neurological symptoms?
NSAIDs
Opioids
Trigger point injections
What happens if a neuraxial catheter breaks off?
Leave the fragments in the patient, alert the patient, and watch for complications.
What do you do if there is blood in the NEEDLE?!
Needle was inserted too laterally
Redirect midline
What do you do if there is blood in the epidural catheter?
Pull the catheter back a little, flush, and repeat procedure till you are unable to aspirate blood and/or not enough catheter remains in the space
What do you do for a failed spinal (no anesthesia)
If a spinal does not set up in 15-20 mins, it is reasonable to repeat the injection
What do you do with a patchy spinal?
Do NOT repeat spinal ~ transition to another technique
What do you with a unilateral block?
Position the patient with the poorly blocked side down and administer several mL of anesthetic ~ if not, consider another technique
