Week 12 Spinals, Epidurals, and Locals Flashcards
Spinal and epidural are considered ________ _________.
Neuraxial Blocks
In the history of epidural anesthesia, what occurred in the 1950s?
- Popularized epidural anesthesia in the 1950s
- Touhy Needle introduced in 1949
- Lidocaine available in 1950s
In the history of epidural anesthesia, what occurred in the 1960s?
By the 1960s it was popular amongst the obstetric population
Today neuraxial blocks are widely used for:
- Labor analgesia;
- Caesarian section;
- Orthopedic procedures;
- Perioperative analgesia
- Chronic pain management
(He said even Urology cases)
Neuraxial blocks in anesthesia use (3)
- Alternatives to general anesthesia
or
- Used simultaneously with general anesthesia
or
- afterward for postoperative analgesia.
Neuraxial techniques have proven to be safe when well managed. However, the is still risk of complications ranging from:
- self-limited back soreness to debilitating permanent neurological deficits and even death
Benefits of neuraxial blocks:
Reduce the incidence of:
- Venous thrombosis & pulmonary embolism
- Cardiac complications in high-risk patients
- Bleeding & transfusion requirements & vascular graft occlusion
- Pneumonia & respiratory depression following upper abdominal or thoracic surgery in patients with chronic lung disease
- An earlier return of gastrointestinal function
Epidural is the reversible chemical blockade of ________ ________ produced by the injection of a LA drug into the epidural space
neuronal transmission
It interrupts transmission of sensory, autonomic, and motor nerve fiber transmission in the anterior and posterior nerve roots
Epidural anesthesia interrupts transmission of sensory, autonomic, and motor nerve fiber transmission in the _______ and _______ nerve roots.
anterior;
posterior
More benefits of epidural anesthesia:
- Avoidance of larger doses of anesthetics and opioids
- amelioration of the _________ state.
- improved oxygenation from decreased splinting.
- enhanced ___________ (Hint: GI).
- suppression of ________ _________ response to surgery.
- ______-______ increases in tissue blood flow.
hypercoagulable
peristalsis
neuroendocrine stress
sympathectomy-mediated
Epidural benefit:
Reduction of parenteral opioid requirements, which decreases – (4)
- Atelectasis
- Hypoventilation
- Aspiration pneumonia
- Reduction of ileus duration
Postoperative epidural analgesia reduces the time to __________; and preserves _________ reducing cancer spread according to some studies
Extubation;
Immunity
Benefits of epidural anesthesia in OB:
- Widely used for women in labor and during vaginal delivery.
- C-sections are most performed under epidural or spinal anesthesia: both blocks allow a mother to remain awake for the birth of her child.
- Some studies show it is less maternal M&M than GETA (largely d/t incidence of aspiration and failed intubation)
Epidural Anesthesia advantages:
- Predictable
- Can provide a segmental blockade
- Reduce risk of thrombosis
- PT can remain fully conscious
- Analgesia into the post-operative period
Epidural Anesthesia
disadvantages:
- May require 10-20 minutes to establish a level
- Sympathetic blockade
- Surgeon complains “It takes to long”
- Time-consuming to perform
Vertebral column is made up of ____ Vertebrae
Cervical:
Thoracic:
Lumbar:
Sacral:
Coccygeal:
33
Cervical: 7 (C1-C7)
Thoracic: 12 (T1-T12)
Lumbar: 5 (L1-L5)
Sacral: 5 fused (S1-S5)
Coccygeal: 4 fused to form the coccyx
T/F: Vertebrae differ in shape and size at the various levels
True
____ cervical vertebra (_______)- lacks a body and has unique articulations with the base of the skull
1st
atlas
______ cervical vertebra (_______)- has atypical articular surfaces
2nd
axis
All _______ thoracic vertebrae- articulate with their corresponding _______.
12;
Rib
_______ vertebrae- have a large anterior cylindrical body
Lumbar
When all vertebrae are stacked vertically the hollow rings become the ________ _______ (where the cord and its coverings sit)
spinal canal
Individual vertebral bodies are connected by :
intervertebral disks
Spinal Ligaments- (superficial to deep):
- Supraspinous
- Interspinous
- Ligamentum flavum
- Posterior longitudinal
- Anterior longitudinal
The spinal canal contains the cord with:
- coverings (meninges)
- fatty tissue, and
- venous plexus
Meninges- 3 layers:
- pia mater,
- arachnoid mater and
- dura mater (contiguous with cranial counterparts)
meninge closely adherent to the spinal cord
Pia mater
meninge closely adherent to the thicker and denser dura mater
Arachnoid matter
Where is the CSF contained?
contained between the pia and arachnoid mater in the subarachnoid space
where is the Epidural space (potential space)?
within the spinal canal bounded by the dura and the ligamentum flavum
The spinal cord extends from the ____ to the _____ in adults.
and in children?
Extends from the foramen magnum to the level of L1 in adults
In children the spinal cord ends at L3 and moves up with age
Lower spinal nerves form the :
cauda equina (horse’s tail)
Performing lumbar (subarachnoid) puncture below L1 in adults and L3 in children usually avoids potential needle trauma to the cord; damage to the _______ _________ unlikely
cauda equina
MOA of neuraxial blockade:
Interruption of efferent autonomic transmission at the spinal nerve roots
Sympathetic Blockade
The physiological responses of neuraxial blockade
S/S:
decreased sympathetic tone/ unopposed parasympathetic tone.
drop in BP
decrease in HR
arterial vasodilation- decreased SVR
As a primary anesthetic, neuraxial blocks are most useful in:
- lower abdominal
- inguinal
- urogenital
- rectal
- lower extremity surgeries
Upper abdominal procedures such as gastrectomy have been performed with spinal or epidural anesthesia- but:
can be difficult to safely achieve adequate sensory levels for patient comfort
T/F: Epidurals are good choice for patients with coexisting pulmonary disease.
True :)
Pre-op considerations for neuraxial blocks:
- Discuss the plan with the surgeon.
- Discuss the proposed surgery and explain the epidural technique in detail.
- Do not coerce the patient into an epidural anesthetic
- Do a full pre-operative assessment and interview
Most important pre-op labs to have before epidural procedure?
Coags!!! Specially platelets
Informed consent for neuraxial block considerations:
- Make sure you document that you have discussed the advantages & disadvantages of the anesthetic
- Discuss risk
- GA is plan B
- Document
Pre-op meds considerations for neuraxial blocks:
- Pt should be NPO
- Do not over-sedate the patient
- OB patients are not sedated
- Midazolam (titrate to effect)
- Opioids
Epidural is indicated for (6)
- “balanced” regional/general anesthesia
- Pt has a full stomach
- Upper airway anomalies
Contraindications for neuraxial blocks: absolute
Epi I RAP CHICAS
-
I nfection at the site
| - R efusal from patient.
- A ortic/mitral stenosis or asymmetric septal hypertrophy
-
P sychiatric disease - Severe
| - C oagulopathy
- H erpetic infection
- I ncreased ICP
- C NS disease - Preexisting
- A llergy to LA
- Septicemia or bacteremia
Contraindications for neuraxial blocks: relative
my Epi Relatives love CHOC MUSH
- C lotting/blood abnormalities (Minor) ( ASA or mini heparin doses / Check coags ).
- H A (chronic) or backache
- O besity/ deformities of the spinal column
- C hronic HTN (Untreated)
- M ultiple attempts
- U mbilicus - surgeries above it.
- S urgery of unknown duration
- H IV infections
Neuraxial Block patient preparation:
- Baseline VS & Pt must have an IV
- Standard monitors
- Equipment to provide positive pressure ventilation
- Supportive meds
In the history of epidural anesthesia, what occurred in the 1950s?
- Popularized epidural anesthesia in the 1950s
- Touhy Needle introduced in 1949
- Lidocaine available in 1950s
Benefits of epidural anesthesia in OB:
- Widely used for women in labor and during vaginal delivery.
- C-sections are most performed under epidural or spinal anesthesia: both blocks allow a mother to remain awake for the birth of her child.
- Some studies show it is less maternal M&M than GETA (largely d/t incidence of aspiration and failed intubation)
In an epidural midline approach - what layers do you penetrate with needle?
- Skin
- Subcutaneous tissue and fat
- Supraspinous ligament
- Interspinous ligament
- Ligamentum flavum
- Epidural space
For an epidural you palpate the patient’s back to find the:
and which sites do you use?
Superior aspects of the iliac crest and the spinous process
L4 or L4-5
Use the largest and most superficial interspace you can find
L2-3
(according to VP- we use L4 - L5)
Draw up the LA to be used for the skin wheal in a _____ ml ______ syringe
Draw ______ ml of preservative free saline into the ____ ml _______ syringe
3; plastic
2-3; 5ml glass
In an epidural: Raise a skin wheal with the ______ -gauge needle
27
Ligamentum flavum is normally _____ cm from the skin
4 cm
In an epidural paramedian approach - what layers do you penetrate with needle?
- Skin
- Subcutaneous tissue and fat
- Paraspinous muscle
- Ligamentum flavum
- Epidural space
With the Paramedian technique how do you point the needle?
Direct needle medially and cephalad
Touhy Needle (Epidural needle) characteristics:
- 3.5 inches long
- 17-18 gauge
- With inner stylet: prevents occluding the lumen with tissue.
- with rounded tip: prevent puncture of the dura and easier to thread the catheter
- Markings along the shaft of the needle are in 1 cm increments
- 9 cm from the tip of the needle to the proximal edge of the hub
- 11 cm to the distal edge of the hub
Markings on the Epidural Catheter
1st. marking= _______ cm
Each marking after that is _____ cm
2nd double marking= _____cm
Thick mark is ______cm.
3rd triple mark is _______cm.
- 1st marking= 5 cm
- Each marking after that is 1 cm
- 2nd double marking= 10 cm
- Thick mark is 11 cm
When inserted to this point you are at the tip of the needle in the epidural space
- 3rd triple mark= 15 cm
Single hole at the end vs multiple ports on its distal side
Skin to Epidural Space:
_______ cm in 60% of patients
_______ cm in 25% of patients
_______ cm in 10% of patients
> ________ cm in 5% of patients
- 4-6 cm in 60% of patients
- 2-4 cm in 25% of patients
- 6-8 cm in 10% of patients
- > 8 cm in 5% of patients
Usually leave _____ cm of the catheter in the epidural space.
3-4 cm
Things to keep in mind with the epidural catheter: (4)
- When advancing the catheter, the patient may feel transient paresthesia
- Catheter may puncture the dura and you will get CSF (may not aspirate CSF).
- Be careful removing the needle with the catheter.
- An antibacterial filter is attached to the end of the catheter
T/F: A negative aspiration ensures you are not in a vessel or the subarachnoid space
False! - it does NOT
Test dose for epidural
and
what level of block would be produced if inadvertently injected in CSF?
3 ml of 1.5-2% Lidocaine with 1:200,000 epinephrine
This dose will only produce a T10 block if injected in the CSF
What should you ask a patient during a test dose?
to report symptoms of “feeling different, ringing in the ears or metallic taste in the mouth”
During test dose, if it is an intravascular injection what symptoms would you see?
- Increase in HR of 15-20 bpm for 2-3 minutes
- Systemic toxicity- numb tongue, dizziness, ringing in the ears
During test dose, if it is a subarachnoid injection what symptoms would you see?
Immediate onset of sensory and motor block in the buttocks and lower extremities (T10 block)
During test dose, if injection is in the subdural what would happen?
Produces a High block
T/F onset of epidural is faster than the spinal
False - Epidural onset takes longer (~10- 20 mins)
Evaluation of patient after an epidural involves:
- After repositioning evaluate patient for 10-30 minutes
- Measure BP every minute for the first 3-5 minutes then every 2-3 minutes until the block is set.
- Determine the level of blockade every 2-3 minutes with an alcohol sponge and then a sharpened device until the level is set.
Check level every 30-45 minutes - Evaluate BP, ECG, and pulse ox
The distribution of the LA in the epidural space is dependent on:
the volume injected
Positioning will not aide in distribution of the local
The primary objective of the epidural is to block the_________ fibers located in the ______ _______.
afferent;
dorsal roots
Site of action of Local:
- Ultimate target are the spinal nerves & roots
- The dura serves as a barrier to diffusion of Local
- Most is absorbed into the circulatory system some will stay in the epidural space and the rest will enter the spinal nerves and nerve roots
- The Local will spread horizontally and longitudinally once in the epidural space
Distribution of the LA
Blockade of fibers occurs quickly.
Blockade is ___ __________ higher than sensory
2 dermatomes
Distribution of the LA in epidural:
- A quick drop in BP may be an early sign that a “_________” is setting up.
- Rapid decrease in BP cause :
- These effects will be accentuated in which patients:
- spinal;
- nausea or dizziness.
- hypovolemic pt’s
Cardioaccelator fibers
Distribution of the LA in epidural:
Temperature & Light Touch
- Unmyelinated C & myelinated A-delta fibers.
- Loss of these follows autonomic blockade.
- Assess with Alcohol sponge
- Loss of temperature correlates with sensory loss
- May report lower extremity feels warm
Distribution of the LA in epidural:
Initial Motor Impairment & Touch
- Myelinated A-beta & A-gamma.
- Follows loss of temperature and touch discrimination
- Onset of motor weakness and impaired perception of strong tactile stimulation
- Use a sharpened device or pinch method to assess level
Distribution of the LA:
Profound Motor & Proprioception
Myelinated A-alpha fibers
Profound motor block develops with loss of proprioception
Feel “Phantom Limb”
How to Assess motor block:
Lift shoulders of the bed (T6-T12)
Raise knees (L2-3)
Flex toes (L4-L5)
Dorsiflex feet (S1-S2)
Epidural Desired Level of Block
Will be determined by:
- The volume and concentration of drug.
and
- The level of the epidural catheter placement.
Injection of 10-15 ml of LA into the epidural space in the lumbar area will produce a ___________ level in the average sized patient
T7-9
What is an inadequate block and what can you do?
The concentration or volume of the drug may have been too weak to penetrate spinal nerves
If the block does not reach the desired level, you can give a top off dose:
- One-half of the initial volume can be reinjected
- Wait 10-15 minutes before reinjection
_________ is the key factor in the height of the block (in epidurals)
Volume
The guideline for dosing an epidural in adults is _________ ml per segment to be blocked.
Adjust the guideline for shorter patients (______ in.) or taller patients (__________in.).
1 - 2;
< 5 ft. 2;
> 6 ft. 2
’“**T10 block from L3-4 injection: 6-12 ml of local anesthetic. **
Epidural:
The ______, _______, and _______ _______ administered will vary with the level and duration of block desired.
The type, volume, and total dose
LA drugs reversibly interrupt nerve impulse conduction by interfering with_________ conductance.
sodium ion
Local Anesthetic
Potency
- Equal to lipid solubility
- Higher lipid soluble, the more readily it penetrates neuronal membranes
- Better able to penetrate A-alpha motor fibers
Local anesthetic
Rate of onset:
- Determined by pKa
- Weak bases
- pKa near physiologic ph will move more readily into nerve membranes
The neutral (non-ionized) form is most readily able to penetrate the neuronal membrane
Local anesthetic
DOA:
- Determined by potency and protein binding
- Highly protein-bound agents are less available for systemic absorption
Most common LAs:
- Bupivacaine (Marcaine)
- Ropivacaine
- Lidocaine
- Mepivacaine
- 2-chloroprocaine
Distribution and Uptake of LA
The spinal nerves in the epidural space are larger and covered by _______ and ______ matter.
It takes ________ times the dose (mass) of LA to accomplish the same blockade as a spinal
arachnoid; dura
6-8
what three factors influence the level of DOA of LA in an epidural?
and which has biggest influence of level of blockade
- volume: larger = greater vertical spread.
- dose: increase= intense analgesia/ prolonged DOA.
- concentration: increase= faster onset/ more intense block
___________________
Volume
Vasoconstrictors such as Epinephrine can help:
Be a marker for intravascular injection
Prolong duration of action of Locals
effect of vasoconstrictors on the DOA of LA
prolong
epi in LA is usually a __________ dose
1:200,000
The closer the injection site is to the spinal nerve to be blocked, the _______ rapid the onset of analgesia
more
Slowly titrate LA into the epidural space ( _____ ml increments every _____`)
Pt. may complain of?
3-5ml every 60 seconds.
Headache (HA)
this does not detect intravascular injection
T/F: **level and duration of action? (For epidurals)
- Patient position does NOT affect it.
- Extremes of age affects spread.
- Height does not affect the dose.
True :)
False
True
for epidural LA dose, what would you do for each population
elderly
obese
Parturient
E- half dose
O- decrease d/t larger cephalad spread
P- 1/3 dose needed from non-pregnant (d/t engorgement of epidural veins/ hormones).
If the pt. has an adequate level but not a solid block, redose with a top-up dose or
20% of the initial volume
During the anesthetic do not allow the level of blockade to recede
If the pt. has an adequate level but not a solid block and they are redosed, what will happen to the intensity and height of the block
intensity increase
height remains the same
if epidural level has regressed 1-2 dermatomes, redose with:
1/2 to 1/3 initial volume.
Dermatome level for C- section:
T4 level ( nipple area )
Dermatome level for knee or hip sx:
T10 ( umbilicus )
Dermatome level that is considered dangerous area:
C4- C5, *even T1 ( Cardiac accelerators ).
CNS S/S of LA toxicity (7)
Nobody Drinks Like Drew Drinks Vodka And Club
- numbness of tongue and lips
- dizziness
- lightheadedness
- disorientation
- drowsiness
- visual & auditory disturbance
- convulsions
CV S/S of LA toxicity (3)
- ecg changes
- CV depression
- cardiac arrest
what is it called when an intended epidural is given into spinal space
high spinal and its very dangerous
treatment for CV collapse from LA toxicity
IV 20% lipid emulsion
in LA toxicity, what 4 meds should be avoided
- vasopressin
- Ca2+ channel blocker
- beta-blocker
- LAs
spinal are the reversible chemical blockade of neuronal transmission produced by injection of a LA into CSF contained in the _______
subarachnoid space
t or F: the advantages of spinals are similar to epidurals
T
only differences is the smaller dose of LA = less toxicity
spinals produce a (sympathetic/parasympathetic) blockade 100% of the time, which can cause?
sympathetic
hypotension
what can be given prophylactically for a spinal
phenylephrine
T or F: spinal anesthesia is a good choice for major intraabdominal procedures
F- not a good choice
Good choice for procedures of the mid to lower abdomen and lower extremity
in pts with pulmonary disease, spinal level should not exceed what level
T4
T or F: spinal anesthesia is a good choice for major intraabdominal procedures
F- not a good choice
9 absolute contraindications for spinal
- pt refusal
- severe psych disease
- CV disease
- severe hypovolemia
- CNS disease
- blood clotting anomalies
- infection at site
- septicemia/bacteremia
- allergy to LA
10 relative contraindications of spinal
- HIV
- Surgery of unknown duration
- untreated chronic HTN
- procedure above the abdomen
- obesity
- deformity of spinal column
- chronic HA/backache
- bloody tap
- multiple attempts
- minor blood clotting abnormalities
procedural site for spinal
one of four intervertebral spaces L2-S1 (popular site L2-3 or L3-4)
if pt is in lateral position for spinal insertion, would surgical side be up or down if using a hyperbaric solution
surgical side down!
when preparing a spinal, what two structures will differe between midline and paramedian approach
midline- supraspinous ligament & interspinous ligament
paramedian- paraspinous muscle & ligamentum flavum
how often should you check BP after spinal admin
Q3-5 minutes until block is set
how frequently should you assess the progress of the spinal block after administration until block achieved and then how frequently after that
every mintute until block achieved
Q30-45 min
two ways to test if spinal is working
- Alice/hemostats?
- alcohol sponge
earliest sign spinal is working
drop in BP followed by nausea and dizziness
after spinal admin, loss of temp and light touch signals that what fibers are blocked . How can we assess this
C and A-delta
alcohol sponge
loss of these follows autonomic blockade
in spinal admin, motor impairment and touch and managed by what fibers
A-beta and A-gamma
which comes first in spinal
loss of motor & touch OR loss of light touch and temperature
loss of light touch and temperature
:)
which dermatomes are you assessing if you ask pt to dorsiflex feet
S1-S2
which dermatomes are you assessing if you ask pt to flex his toes
L4-L5
which dermatomes are you assessing if you ask pt to raise their knees
L2-L3
which dermatomes are you assessing if you ask pt to lift shoulders off bed
T6-T12
a block at S2-S5 is referred to as a ___________.
There (is/is no) effect of ANS.
Surgical anesthesia is limited to ________, _________, & __________
saddle block
is no
perineum, perianal, genitalia
A block at T10 (umbilicus) is referred to as a ________.
It blocks ______ &__________.
it produces _________ & __________.
What surgeries is it good for?
low spinal
s1-5 & L1-5
vasodilation and lowers BP
gynecologic, vaginal delivery, lower extremity surgery, TURP, cysto
(C-section is T4)
A block at ______ is referred to as a high spinal.
It is used for ___________ surgery though the patient can still feel traction.
It can cause (vasodilation/vasoconstriction) and block _______________ fibers
T4 (nipple)
upper abdominal
vasodilation
cardio accelerator
A block at C8, referred to as __________,
is a (high/low/total) spinal.
Pt may experience ________ that can lead to ____ &________.
little finger
total
difficulty breathing
respiratory & cardiac arrest
This is bad news friend you better grab airway eqt.
which two spinal needles are “puncturing” needles
Quincke & whittacre
name the 4 spinal needles
Quincke
Whittacre
Sprotte
Pencan
what causes PDPH and how can it be prevented/exacerbated
CSF leak
choice in needle size
- large (20 -22G) = more CSF but easier to use
- smaller (25- 26G) = less CSF but more difficult to use
LA solutions > 5% concentration are linked to ___________
neurotoxicity
very (large/small) amounts are needed for spinals
SMALL
T or F: LAs are the safest anesthetic we have and as a result are completely risk free
F- nothing is risk free
Which LA does this describe for spinal use:
2 ml ampule of 5% solution premixed with 7.5% dextrose (hyperbaric). This mixtures has a risk for cauda equina syndrome
A. Lidocaine
B. Procaine
C. Tetracaine
D. Bupivacaine
A
Which LA does this describe for spinal use:
2 ml ampule of 10% solution. Short DOA, low potency.
A. Lidocaine
B. Procaine
C. Tetracaine
D. Bupivacaine
B
Which LA does this describe for spinal use:
2 ml ampule of 1% solution. Provides a more profound block than the other three listed
A. Lidocaine
B. Procaine
C. Tetracaine
D. Bupivacaine
C
Which LA does this describe for spinal use:
2 ml ampule of 0.75% with 8.25% dextrose (*hyperbaric). The onset is 3-5 minutes. You must use a filtered needle with this
A. Lidocaine
B. Procaine
C. Tetracaine
D. Bupivacaine
D
Bupivacaine has less motor block than
tetracaine
spinal dose for normal duration total knee or hip replacement for T10 level
Lidocaine
Bupivacaine
L- 50-75 mg (of a 5% solution = 1-1.5 ml)
B - 8-12 mg (of a 0.75% soltuion = ~1-1.6 mL)
how to we extend normal duration of spinal dose if, for example, you’re with a slow surgeon
epi-wash (100 mcg)–> extends ~ 1 hour
(0.1 - 0.2 mg)
spinal dose for normal duration total knee or hip replacement for T4 level
Lidocaine
Bupivacaine
L- 75-100 mg (of a 5% solution = 1.5-2 ml)
B - 14-20 mg (of a 0.75% soltuion = ~1.8-2.6 mL)
what LA is mainly used for D&C
Chloroprocaine 3% (VERY quick acting and short DOA)
T or F: vasoconstrictors prolong the action of bupivacaine
F- do not prolong the action of bupivacaine… its just vasoconstricting to its not being taken away as quickly
T or F: vasoconstrictors will prolong DOA of ester LAs
T
2 vasoconstrictors used for spinals
epinephrine
phenylephrine (less common)
Vasoconstrictors in the spinal space can: (6)
- constrict blood vessels at the site and slow absorption of LA
- produce analgesia
- prolong DOA of ester LA ( tetracaine, procaine).
- does prolong action of lidocaine
- does not prolong action of bupivicaine
- does not affect spread of block.
intrathecal opioids will not produce analgesia. How can better anesthesia be provided/achieved
administer with LA
Fentanyl Intrathecal Opioid:
Dose:
S/E:
Onset:
Duration:
15-25 mcg
Higher doses: resp. depression, itching , and urinary retention
5- 10 minutes
2- 4 hours.
Duramorph is :
Onset:
Dose:
DOA:
Morphine (preservative-free)
- 60 - 90 minutes
- 0.1- 0.5 mg
- Profound analgesia for 18-27 hours.
most commonly used
intrathecal fentanyl and duramorph dose
F- ~ 20 mcg (15-25 mcg)
D- 0.15 mg (common in OB)
about how long should spinal last
~ 2 hours
3 most important factors for determining distribution of LAs for spinal
- baracity
- pt position during/just after
- dose of LA
density of CSF =
1.004- 1.008
determines where spinal LA will distribute
Baracity
solution is hyperbaric… what is its density in relation to CSF
> CSF
> 1.008
most commonly used SINKS
solution in hypobaric… what is its density in relation to CSF
< CSF
< 1.008
FLOATS up to the least dependent area. Good for lateral position sx.
Li
what is used to make a solution hyperbaric
dextrose
you want to achieve a saddle block… what baracity LA will you adminster
hyperbaric
T or F: you can achieve a high spinal after an isobaric solution LA administration by placing pt in trendelenberg
F- isobaric do NOT spread with position changes and are ideal when repositioning may be required
Limited clinical application/ Difficult to obtain a high level
spinal level normally fixed in ________ minutes of positioning patient.
5-10
most evident with hyperbaric solutions
4 CV complications following a spinal
- block sympathetic fibers
- block cardioaccelerator fibers
- cause hypotension/bradycardia
- BP decrease by 15-20% in most healthy pts
3 ways to treat hypotension following spinals
- prevent with preload/prophylactic admin of 1-2L crystalloids
- supplementary O2
- treatment (slight trendelenberg, bolus crystalloid, ephedrine 5-10mg IV)
S/S of PDPH
N/V
photophobia
tinnitus
dizzy
cranial nerve palsies
symptoms are postural
3 treatment therapies for PDPH
- resolves in 5-7 days
- conservative therapy x24 hours
- epidural blood patch
when administering an epidural blood patch for PDPH, where should you adminsiter it
blood moves cephalad so one interspace below
all LAs are weak (acids/bases)
Bases
how are LAs classified
according to structure
for amide LAs, the amine group is (hydrophobic/hydrophilic) and the aromatic end is (lipophobic/lipophilic)
hydrophilic
lipophilic
amides metabolized by
microsomal P-450 system
Put in order: amide LAs order of metabolism
ropivacaine
lidocaine
Prilocaine
bupivacaine
mepivacaine
prilocaine>lidocaine>mepivacaine>ropivacaine>bupivacaine
ester LAs metabolized by
pseudocholinesterases, hydrolysis is very rapid
procaine and benzocaine is metabolized by ______
PABA (p-aminobenzoic acid)
CSF lacks esterase enzymes so termination of action of ester depends on
redistribution to bloodstream
short cut way to tell the difference bewteen amides and ester LAs
I before C = Am**I*des
name some amide LAs
- bupivacaine
- lidocaine
- ropivacaine
- etidocaine
- mepivacaine
name some ester LAs
cocaine
procaine
tetracaine
_______ end of ester LA is lopohilic and penetrates lipid bilayer of nerve membrane
aromatic
_________ part of amide LA is hydrophilic and remians of either side of nerve membrane
hydrophilic ring
which is hydrophobic and which is hydrophilic (the ends only)
allergy or cross sesntivity occurs with (amide/ester) linkage
ester
Nerve fibers classified according to what 3 things
- size
- conduction velocity
- function
Ester LAs are rapidly metabolized in plasma by __________ into the metabolite __________. Amides are slowly destroyed by ______________
cholinesterase
PABA
liver microsomal P450 enzymes
Na+ channels are membrane-bound proteins composed of ________ subunits and ________ subunits. LAs bind to a specific region on (alpha/gamma) subunits and inhibit membrane (depolarization/repolarization), thus inducing anesthesia
1 alpha
2 betas
alpha
depolarization
(transmission/transduction) of electrical impulses along nerve membrane signal (transmission/transduction) along nerve fibers
transmission
transduction
sensitivity of nerve fibers to LA is determined by _________, __________, and other factors
axonal diameter
myelination
RMP = _________ by active transport and passive diffusion. Na+/K+ pump transports ___ Na+ out of cell for every ____ K+ into cells
-60 to -70 mV
3
2
onest of action of LA depends on what two things
While the DOA of LA depend on what two things
ONSET: lipid solubility & pKa
DOA: lipid solubility & potency
T or F: pH is pKa at which fraction of ionized and nonionized drug is equal
F – pKa is pH at which….
Vasoconstrictors such as Epinephrine can help:
Be a marker for intravascular injection
Prolong duration of action of Locals
less potent & less lipid soluble have (slower/faster) onset than more potent more lipid soluble agents
faster
Quick summary of LAs MOA
- slows down speed/stops generation of AP
- bind to Na+ channels
- inhibit Na+ influx in the neuronal cells
3 factors affecting LAs action
- lipid solubility ]
- influence of pH
- vasoconstrictors
T or F: epinephrine prolongs a bupivacaine block by increasing the volume of bupivacaine present in space
F – literally the slopiest written question to date so my apologies
epinephrine vasoconstricts the vessels which decreased the rate of systemic absorption So That (VP voice) the local hangs out a bit longer :)
increased lipid solubility = (slower/faster) nerve pentration & onset of action
faster
A. a lower pKa (7.6-7.8) is (slower/faster) acting
B. give examples of low pKa anesthetics
C. a higher pKa (8.1-8.9) is (slower/faster) acting
D. B. give examples of higher pKa anesthetics
A. faster
B. lidocaine & mepivacaine
C. slower
D. procaine, tetracaine, & bupivacaine
t or F: vasoconstrictors synergize the vasoconstricting effects of LAs
F – vasoconstrictors antagonize the vasodilating effects of LAs
2 medications that affect LA action
opioids – synergistic analgesia & attenuation of C-fibers
a-2-adrenergic agonist – clonidine inhibitory effect on peripheral nerve conduction & analgesia via supraspinal/spinal adrenergic receptors
rate of systemic absorption of LAs is related to ______ & ________
blood flow & vascularity
decreased absorption of LAs with the use of vasoconstrictors (reduces/increases) peak concentration of LA in blood, (enhances/ inhibits) quality of anesthesia, and (shortens/prolongs) DOA and (increases/limits) toxicity
reduces
enhances
prolongs
limits
pharmacokinetics of LAs determined by what 3 things
- tissue perfusion
- tissue blood partition coefficient
- tissue mass
early S/S of CNS LA toxicity
late S/S of CNS LA toxicity
excitatory S/S
circumoral numbness
tongue paresthesia
dizziness
tinnitus
blurred vision
___________
clonic-tonic seizures
___________
restlessness, agitation, nervousness
Highly lipid soluble LA produce seizures at lower blood concentration
disadvantages of spinal anesthesia:
- Hypotension
- Intense motor blockade that may last for hours post-op
- “takes too long”
T or F: spinal anesthesia is a good choice for major intraabdominal procedures
F- not a good choice
Good choice for procedures of the mid to lower abdomen and lower extremity
Fentanyl Intrathecal Opioid:
Dose:
S/E:
Onset:
Duration:
15-25 mcg
Higher doses: resp. depression, itching , and urinary retention
5- 10 minutes
2- 4 hours.
Respiratory effects of LAs:
Relax bronchial smooth muscles
Phrenic nerve paralysis
Depression of hypoxic drive
Cardiovascular effects of LAs: (7)
- Depress myocardial automaticity
- Unintentional IV injection of bupivacaine may produce severe CV toxicity
- Left ventricular depression, AV block, arrhythmias
- Decreased cardiac excitability and contractility
- Decrease conduction rate
- Increased refractory rate
- Hypotension
Local Anesthesia Toxicity
Related to absorption from the site
(Review LAST s/s)
The distribution of LAs occurs in 3 phases describe:
Highly vascular tissue (lungs and kidneys) then less vascular tissue (muscle and fat), then drug is metabolized
Major CV toxicity requires _____ times the local anesthetic concentration in blood as that requires to produce seizures
3
