Spinal Anesthesia (Exam I) Flashcards
What type of neuraxial technique would exhibit a more rapid onset?
Spinal blocks
What type of neuraxial technique would exhibit a slower onset?
Epidural blocks
What type of block tends to extend cephalad?
Spinal blocks
The spread of epidural blocks can be controlled via the ______ of the local anesthetic.
volume
Which type of neuraxial block is more dense? Which is more segmental?
Spinal = Dense
Epidural = Segmental
Which type of neuraxial block will produce a dense neuromuscular blockade?
Spinal blocks
T/F. Epidural blocks tend to produce hypotension more than spinal blocks?
False. Spinal blocks tend to produce greater hypotension.
Spinal blocks are ____ based, whilst epidural blocks are _____ based.
dose; volume
Where should spinal blocks be placed? (especially if you’re a beginner)
L3 - L4
Differentiate the duration of action of spinal blocks vs epidural blocks.
Spinal blocks = limited and fixed duration
Epidural = variable duration due to catheter in place and infusion delivery.
Which neuraxial technique is more prone to local anesthetic toxicity?
Why?
- Epidural blocks
- Possibility for LA to infiltrate vasculature and flood the circulation.
Which neuraxial technique exhibits baracity?
What does this mean?
- Spinal blocks
- This means that the LA is influenced by gravity.
What factors affect the dermatome spread of a spinal block?
- Position changes
- Baricity
- Dose
Epidural dermatome spread is incremental based on _______.
volume
Epidural spread is ____ mls per segment.
1 - 2
Which neuraxial technique is the preferred technique for Cesarean delivery?
Spinal block
What other names exist for spinal blocks?
- Subarachnoid block
- Intrathecal block
What types of surgical procedures indicate the use of spinal block?
- Lower abdomen
- Perineum
- Lower extremities
What are absolute contraindications to spinal block?
- Coagulopathy (ex. known disorder)
- Sepsis
- Patient refusal
- Dermal site infection
- Hypovolemia
- Intraspinal mass
- Severe Valvular disease
What are the relative contraindications to neuraxial anesthesia?
- Spinal column deformities (ex. kyphosis)
- Preexisting spinal cord disease (ex. MS)
- Chronic Headache/backache
- Inability to place block after 3 attempts
How many attempts does one have to place a neuraxial block?
Three attempts typically
The superior aspects of the iliac crests line up with what spinal segment?
L4
The inferior aspects of the scapula line up with what spinal segment?
T7
How many vertebrae are there?
- 8 Cervical
- 12 Thoracic
- 5 Lumbar
- 5 Sacral
- 1 Coccyx
What type of neuraxial technique is used with a sacral approach?
Epidural
How is the sacral hiatus identified?
Via the sacral cornua on either side of the hiatus.
Which spinal nerves are our cardioaccelerators?
T1 - T4
What are the high points of the spine when the patient lays in the supine position?
High points = C3 and L3
What are the low points of the spine when the patient lays in the supine position?
Low points = T6 and S2
When blood is encountered during a neuraxial needle insertion, the most likely cause is that the needle is _________.
lateral
(needle should be dead center medial)
What ligament is indicated by “c” in the picture below?
Supraspinous ligament
What ligament is indicated by “b” in the picture below?
Interspinous ligament
What ligament is indicated by “a” in the picture below?
Ligamentum Flavum
What is the distance from the skin to the ligamentum flavum?
4 cm in 50% of patients
4-6 cm in 80% of patients
Where is the ligamentum flavum thinnest?
Cervical interlaminal spaces
Is the ligamentum flavum thickest near the rostral lamina or the caudad lamina?
Caudad Lamina
Where does the spinal cord typically end in adults?
L1 (60% of patients)
Where does the spinal cord typically end in kids?
L3
Where should a beginner SRNA stick for neuraxial access?
L3 - L4 interlaminar space
Where does the dural sac terminate?
What is in the dural sac after the termination of the spinal cord?
- S2
- Cauda Equina
List the spinal meninges from outermost to innermost.
Dura mater
Arachnoid mater
Pia mater
Which of the spinal meninges is avascular?
Arachnoid mater
Which of the spinal meninges is composed of a thin layer of connective tissue with interspersed collagen?
Pia mater
How much CSF do adults have?
100 - 160 mL
At what rate is CSF produced?
20 - 25 mL/hr
The entire CSF volume is replaced roughly every ____ hours.
6
What dermatome is at the level of the umbilicus?
T10
What dermatome is at the level of the nipples?
T4
What dermatome is associated with the thumb?
Why is this dermatome pertinent in the monitoring of neuraxial anesthesia?
- C6
- Thumb being numb could be indicative of impending C3-C6 involvement (diaphragmatic innervation)
What is Tuffier’s line?
What does it indicate?
- Imaginary line between iliac crests.
- Indicates L4 (or L4-L5 interlaminar space)
How much should the second dose of lidocaine 5% be in a spinal neuraxial technique?
Trick question. Spinal’s are one dose only.
What common dose of bupivacaine is used in spinal anesthesia?
Bupivacaine 0.75% in 8.5% dextrose
What common dose of Lidocaine is used in spinal anesthesia?
Lidocaine 5% in 7.5% dextrose
What common dose of Tetracaine is used in spinal anesthesia?
1% in 5% dextrose
What type of anesthetic is indicated below?
Ester
What type of anesthetic is indicated below?
Amide
What is the benefit of neuraxial pharmacologic adjuncts?
- Postoperative analgesia
- Extended duration
- Improved block density
Which neuraxial adjunct only extends block duration?
Vasopressors (ie epinephrine)
What neuraxial adjuncts are there?
- Opioids
- α2 agonists
- Vasopressors
What opioids (with respective doses) are often used in spinal anesthesia?
- Morphine 100 - 400 mcg
- Fentanyl 10 - 25 mcg
- Sufentanil 2.5 - 10 mcg
What opioids (with respective doses) are often used in epidural anesthesia?
- Morphine 3 - 5 mg
- Fentanyl 50 - 100 mcg
- Sufentanil 10 - 25 mcg
Why does post-op apnea and respiratory depression occur from neuraxial opioids?
Due to cephalad spread
Higher doses of opioids are required with which neuraxial technique?
Epidural
Which opioid has a slower cephalad spread? Why?
Morphine due to hydrophilicity
Why is morphine not great for outpatient neuraxial anesthesia?
- Delayed resp depression
- Rostral spread to the brain
- Slow spread to the intrathecal space
Which opioids exhibit an earlier onset of respiratory depression? Why?
Fentanyl and Sufentanil due to their lipophilicity
What troublesome (but not life-threatening) side effect occurs with neuraxial opioids?
Pruritis
How is neuraxial pruritis treated?
- Diphenhydramine 25 - 50 mg IV
- Naloxone 0.1 mg IV (best but reverses pain control)
How is neuraxial pruritis prevented?
- Minimize morphine dose
- Ondansetron 4 mg IV
- Nalbuphine 2.5 - 5 mg IV
How often does urinary retention occur with neuraxial opioid use?
- 30 - 40 %
Morphine doses of < 100mcg will have a lower incidence of _______.
PONV
Adding fentanyl to morphine will decrease the PONV effects. T/F ?
False
What is the epi wash dose?
Why is it used?
- 0.2 - 0.3 mg
- Used to prolong duration of neuraxial medication.
What is the neo wash dose?
2 - 5 mcg
What drug exhibits a much more profound increase in duration when vasopressors are used with it?
Tetracaine
What do the α-2 agonists contribute as neuraxial adjuncts?
- Intensification and prolongation of motor and sensory block.
What is the neuraxial dose of clonidine?
15 - 45 mcg
What is the neuraxial dose of dexmedetomidine?
3 mcg
What factors effect the uptake of medication into the neural space?
- LA concentration in CSF
- Nerve surface area
- Lipid content of nerve
- Blood flow to the nerve
What is the reason for differential block?
Differing neurons reacting to anesthetic due to their characteristics.
ex. smaller diameter neurons more susceptible
In what order are nerves affected by neuraxial anesthetics?
1st: B-Fibers (SNS)
2ⁿᵈ: C- Fibers (pain & temp)
3rd: A-delta Fibers (pain & temp)
4th: Aα, Aβ, Aγ (Motor)
What nerve type (if blocked) would recover the quickest?
Aα (motor function)
What nerve type (if blocked) would recover the slowest?
B-Fibers (SNS)
What nerve type would have the slowest onset of block?
Aα
The sensory block is assessed to be at the T8 level, where would you expect SNS blockade and motor blockade to be?
SNS blockade: T6 (T6 - T2)
Motor blockade: T10
What metabolizes anesthetic in the CSF?
Trick question. No metabolism occurs in CSF, all anesthetics are eliminated by reuptake
What is the most important factor affecting epidural block height and distribution?
Volume
What drug factors greatly influence neuraxial drug distribution and block height?
- Dose
- Baricity
- Patient position
For spinal anesthesia, _____ is the most reliable determinant of local anesthetic spread (and block height).
Dose
What makes a hyperbaric solution?
Dextrose
What makes a Hypobaric solution?
LA + water in 3x the amount of LA.
Ex. 1mL of Lido + 3mL of H₂O
What makes an isobaric solution?
Plain LA or LA/CSF mix
What solution would be best for hip and knee surgeries?
Isobaric
What type of solution was used in each of the scenarios below?
- Hypobaric
- Isobaric
- Hyperbaric
How much hyperbaric SAB would be used in a non-obstetric patient?
2mL
Swirl will be present with ______ solutions.
hyperbaric
Compare and contrast dosing for isobaric and hypobaric neuraxial anesthetics.
How much CSF do adult humans have?
100 - 160mL
How does elderly age affect neuraxial anesthesia?
Everything is exaggerated (↑ duration, faster onset, etc.)
How does pregnancy affect CSF volume?
↓CSF volume via ↑abd pressure
Is local anesthetic spread enhanced or diminished in pregnant patients??
Enhanced
L3 and higher injection sites can result in what?
Neural damage
Inject at L4-L5
What is barbotage?
Aspiration of CSF before LA injection
How does bradycardia occur with autonomic blockade from local anesthetic injection?
- Bainbridge reflex inhibition
- SA node atrial stretch
- Bezold-Jarisch reflex
- T1-T4 cardioaccelerator block
What is the Bezold-Jarisch reflex?
Cardioinhibitory reflex defined as bradycardia, vasodilation, and hypotension resulting from stimulation of cardiac receptors.
Credit: LITFL.com
What is the Bainbridge reflex?
Compensatory reflex of increased heart rate in response to increases in intravascular volume.
If a patient is hypotensive but normovolemic what is the first drug that should be tried? (usually)
Ephedrine
What GI occurrence results from neuraxial anesthesia?
Sympathectomy → increased peristalsis → N/V
Sympathetic blockade above _____ will result in losses to bladder control.
T10
How can neuraxial anesthesia result in hypothermia?
Sympathectomy results in widespread vasodilation and heat dissipation peripherally.
What drug (not meperidine) did Dr. Tubog mention that will treat post-op shivering?
Ondansetron
What is the dose for lipid rescue?
1.5 mL/kg bolus
0.25 mL/kg gtt
Why must the CRNA be prepared to convert to general anesthesia with all neuraxial cases?
- Failed block
- High spinal
- LAST
- Anaphylaxis
- CV collapse
- Prolonged case
What dermatomal level would be necessary for a C-section or upper abdominal case?
T4
What dermatomal level would be necessary for vaginal delivery, uterine surgeries, hip procedures, or TURPs?
T10
What types of needles are cutting needles and thus not a great choice for spinal anesthetics?
- Quincke
- Pitkin
What is the typical onset of spinal anesthesia?
5 min
What needle approach is recommended for patients with scoliosis or other spinal abnormalities?
Paramedian
Name the tissues from superficial to deep in a spinal anesthetic.
Skin
Subcutaneous
Supraspinous ligament
Interspinous ligament
Ligamentum flavum
Epidural space
Dura mater
Subdural space
Arachnoid mater
Subarachnoid space
What degree of approach is used for a paramedian approach for a spinal anesthetic?
10-15°
What ligaments are not felt during a paramedian spinal approach?
Supraspinous and interspinous ligaments
What is an early symptom of a high spinal?
Inability to phonate
What are symptoms of a high spinal?
- Apnea (C3-C5 involvement)
- Inability to phonate
- Sympathectomy
- Unconsciousness
- Upper extremity block
Rapid injection of LA in the subarachnoid space will result in…
A high spinal
If the patient can phonate, the block likely isnt high enough to require ______.
intubation
Canceling a case due to a high spinal is indicated if what conditions are occurring?
Inability to maintain CV and respiratory status
What type of needle tip is preferred to prevent post-dural puncture headache (PDPH) ?
Pencil point
Do the elderly have a higher risk of PDPH from spinals?
No, they have a lower risk.
What is the mechanism of PDPH?
Loss of CSF → CN traction → CN VI adduction & CN VIII tinnitus.
What are the treatments for PDPH?
- Bedrest
- NSAIDs & narcotics
- Caffeine
- Blood patch
What dose of caffeine is given for PDPH?
300 - 500mg PO or IV
A blood patch is determined to be necessary for a PDPH. The patient was stuck at L1-L2. Where would the blood patch be placed?
L2-L3
How does a blood patch work?
20mL of blood is injected into the interlaminar space below site of injury. The blood clots and prevents further CSF leak.
What is the hallmark sign of Transient Neurological Symptoms (TNS) ?
What medication increases the incidence of TNS?
- Severe radicular back pain
- Lidocaine 5%
What is Cauda Equina Syndrome?
- Occurs when cauda equina nerve roots are compressed and leads to possible permanent paraplegia.
What are s/s of possible cauda equina syndrome?
- Bowel/bladder dysfunction
- Paraplegia
- Back pain
- Saddle anesthesia
- Sexual dysfunction
If compression (disc, hematoma, etc.) is a factor in cauda equida syndrome, what is indicated?
Immediate laminectomy within < 6 hours
What can cause transient hearing loss with neuraxial anesthesia?
CSF pressure changes.
What is horners syndrome? What causes it?
- Ptosis, anhydrosis, & miosis
- High sympathectomy
What ester is great for nasal intubations?
Cocaine
What CN are blocked for awake intubations?
CN V, IX, and X
What is arachnoiditis?
What causes it?
Meningeal inflammation from:
- Wrong med in epidural space
- non-preservative free solutions
- Betadine contamination
What are the three most often causes of epidural/spinal hematoma?
- Clotting disorders
- Traumatic needle placement
- Indwelling or long-term catheters
What neuraxial complication has large jury awards?
Epidural/spinal hematoma
