E4 Flashcards
What is a central line and most common sites of access
Access of circulation via large vein
Common sites
- internal jugular
- external jugular
- subclavian
- femoral
What are advantages or disadvantages of inserting CVC in the external jugular and in the internal jugular
External jugular
• Won’t allow CVP monitoring
Internal jugular • Readily accessible Won’t disturb surgery or sterile field • Allows monitoring of CVP Tip at cavoatrial junction
What are advantages or disadvantages of inserting CVC in subclavian and femoral veins
Subclavian • Allows for CVP monitoring • More complicated to insert b/c clavicle hard to US • More likely to cause complications PTX risk higher
Femoral • Easy in emergency CPR Esp if access to head/neck limited • Higher risk of infection Urine/feces • Mobility restrictions
What are indications for CVC and describe why. (7)
1. Monitoring central venous pressure • Indication of fluid status 2. Infusion of caustic drugs • Vasopressor (long-term) 3. Administration of TPN • Not common in OR 4. Aspiration of air emboli • Theoretical 5. Insertion of transcutaneous (shouldn’t this be transvenous??) pacing leads • Less likely w/ better external pacing 6. Venous access for people with poor peripheral veins • Last resort 7. Dialysis access
What are 4 contraindications for CVC placement and why
1. Renal cell tumor • extending into right atrium 2. Tricuspid valve vegetation • Knocking off veg can cause emboli 3. Site infection • May use other site? 4. Site specific • CEA misplace normal anatomy ----IJ = less compressible and likely for CVC misplacement • Femoral ----Incontinence d/t risk for infection
What are 5 complications r/t CVC insertion
1. Pneumothorax/Hemothorax • Especially w/ SC site 2. Line-related infection • CLABSI 3. Carotid puncture • Needles and guidewires can traverse jugulars 4. Dysrhythmias • PVC/Vtach • w/ wire advancement into ventricle 5. Trauma to nearby nerves • Nerves path bundle w/ vessels
What is completed prior to CVC procedure
Checklist complete
Time out
What is the landmark for identification of IJ CVC insertion. Describe anatomy
Anatomy
Identification of landmarks for placement
Apex of triangle
• Where clavicle and sternal heads meet
• Of sternocleidomastoid
• Needle insertion site
• IJ access (lateral/anterior to carotid)
Position of pt for CVC placement and rationale
Trendelenburg
• to decrease risk of air embolism
• increases VR
—-Venodilates
Practitioner positioning during CVC placement
- Comfortable height
- Elbow 90deg for insertion
- Line of site to US
- Kit on dominant side
Process of preping CVC site for insertion. Why
Process
—-Chin-sternum-shoulder-neck-ear
Because:
• In case of moving from IJ to SC site
Alternate site already prepared
Saves time
Describe the drape used for CVC placement
•Head to foot
•side to side
•Previously 4 sterile towels “squared off”
–Possibly increased infection rate
Process of visualization w/ US prior to CVC insertion.
• In Plane vs Out of Plane • Identify structures • Right side IJ generally later to CA ---is IJ collapsable ---Is CA pulsatile • Identify direction of flow (towards=CA away = IJ)
Difference btwn in-plane vs out-of-plane when inserting CVC. Disadvantage of each
Out of plane
Transducer perpendicular to needle
In plane
Transducer parallel to needle
What are 3 different types of access processes
25g “seeker needle”
Cath over needle (18G)
16G syringe w/ US
Process of accessing vessel w/ 25G vs catheter vs 16g syringe
25g “seeker needle”
• Puncture vessel
• Aspirate to confirm vessel
Catheter over needle (18G) • Before/after seeker needle • Insert in IJ • Slide cath into IJ • Connect IV tubing Vein=Blood goes up tubing slowly Artery=blood “shoots” up tubing
With ultrasound
• 16G access needle w/ central bore to thread J-wire
• Disadvantage
No visual of arterial puncture vs venous
Can unscrew syringe to visuals blood
Once guide wire is inserted w/ CVC placement, what should be done and why
Use ultrasound identify wire inside vessel
• Picture for chart
Use out of plane
–identify that you are in the right place
J wire insertion technique
Insert J-wire through needle or catheter • Stabilize needle hand • To prevent needle movement inside vessel • So vessel isn’t punctured Or needle removed • J straightens in insertion syringe • Returns to J shape once in vessel • Rotate J to face left toward sternum Guides wire toward heart easier
remove needle • When identify J wire in place • I.e. notice PVC = in RA • Stabilize J-wire so it’s not removed • Keep hand on wire!! nick skin to enlarge opening • For larger CVC access
Once J wire in place, what comes next
remove needle • When identify J wire in place • I.e. notice PVC = in RA • Stabilize J-wire so it’s not removed • Keep hand on wire!!
nick skin to enlarge opening
• For larger CVC access
Process for CVC advancement once J wire in place
–Advanced catheter over wire
–never letting go of the J-wire
• HOLD WIRE
• So wire doesn’t fully go in
–in a twisting motion
Importance of catheter distance. Difference in sites.
Markings to indicate cath insertion length
Some sites require longer CVCs
More distance to
• Left IJ
• Left SC
If RIJ isn’t successful why would you not immediately attempt LIJ
Can result in peritracheal hematoma
Constrict airway
Options for CVC securement
- Suture (not too tight, think removal)
* Securement devices
Basic background of SAB
Injection of local anesthetic (LA) • into the SA space • produces rapid onset anesthesia Sole anesthetic in combination
Alternate terms for spinal anesthesia
intrathecal subarachnoid block (SAB)
MOA of LA for SAB
-Effect oof LA on the nerve root
What does MOA of LA for SAB depend on
- SIZE of nerve fibers
- MYELIN content of nerve fibers
- CONCENTRATION of LA
- DURATION of contact of LA w/ nerve root
Indications for SAB and why
Procedures of:
- lower abdomen
- perineum
- LE
- CS
Why:
reduces morbidity and mortality
What are 4 absolute contraindications for SAB and why
- Patient’s refusal
- Increased ICP
• Worse w/ puncture - Active coagulopathy
• Cause hematoma compress SC - Inability to position
• Moving target = inc risk to stick SC
What are relative contraindications for SAB and why
- Systemic infection
- Hemodynamic profile
• Pt that would not tolerate
Results of sympathectomy
T4-cardioaccelerator nerve block
decrease in SVR d/t sympathectomy
Shock
AS (dependent on afterload/SVR)
Severe hypovolemia (vasodilation)
Advantages of SAB
Decreased incidence of thromboembolism
Decreased cardiac morbidity and death
Reduced risks of bleeding
Landmarks for SAB or epidural needle insertion
Iliac crest
• Landmark to locate BODY of L4
Inferior angle of scapula
• Landmark to locate the body of T7
• For epidural anesthetic
What is importance to recall for needle insertion in relation to landmarks
- NEEDLE INSERTION IS NOT AT ILIAC CREST/TUFFIER LINE
* IT IS BETWEEN L4/5 INTERSPACE
Epidural sac begins and ends where
Begins=foramen magnum
Caudal Termination=sacral hiatus
Landmark and needle insertion for caudal anesthetic
Landmark
• Sacral cornu
Needle insertion
• Sacral hiatus
What type of anesthesia is caudal block and why
epidural
B/c SC only extends to L1 in adults and L3 in peds
What is the significance of high/low points of the spinal column
Where the LA settles depending on baracity.
What are the high/low points in the spine
high = C3 and L3
Low = T6 and S2
Differing baracity in relation to high/low points of spinal column when supine
hyperbaric
-settle/extend as high as T6
hypobaric
-can extend as high as C3
Treatment for effects d/t T4 sympatholysis of cardioaccelerator nerve
Have ready
- neosynephrine (alpha 1 agonist)
- Ephedrin (alph1/beta agonist)
- –use in case of bradycardia
Significance of the spinous process orientation.
Significance
• Determines angle of needle insertion
Thoracic
• Needle angled upward
Lumbar
• straighter
Significance of location of blood vessels
Adipose tissue and blood vessels arelocated at lateral aspect of epidural space
Avoid unintentional intravascular injection
Blood w/ needle insertion
• Needle is likely lateral
Vessels may be engorged during pregnancy
Which ligaments will NEVER be punctured when performing SAB.
What would this indicate
Anterior and posterior
ligaments
That the needle has gone through the SC
What is the last ligament before the SA space
Ligamentum flavum
Significance of the ligaments flavum in SAB
The last ligament punctured before reaching the SA space
Variability of depth below skin
• 50% pts avg 4cm
• 80% pts avg 4-6 cm
Significance of the ligaments flavum in SAB
The last ligament punctured before reaching the SA space
Variability of depth below skin
• 50% pts avg 4cm
• 80% pts avg 4-6 cm
Where does the SC terminate in adults vs meds?
Why is this significant when performing SAB
Termination
• Adult = L1
• Peds = L3
R/t doing SAB
• Th reason insertion is at L4/5 interspace
Slides 17 of SAB lecture identify Spinal cord termination, cons medullaris, caudal equina
pic
Slide 18 of SAB lecture identify caudal equina, subdural space, subarachnoid space, LF and epidural space
pic
Describe the anatomy of the dura mater
Outer most Thickest Starts at the foramen magnum ends in S2 • fuses with filum terminale
Describe the anatomy of the arachnoid mater
Delicate avascular membrane Subarachnoid space • between the arachnoid mater and the pia mater • contains CSF
Describe the anatomy of the Pia mater
Adherent to the SC
thin layer of connective tissue cells
• interspersed with collagen
What is the difference when diong spinal and epidural anesthesia
the presence of CSF
What are dermatones
Sensory level corresponding to spinal nerve
What are dermatones
Sensory level corresponding to spinal nerve
–The skin area innervated by a given spinal nerve and its corresponding cord segment
Corresponding sensory location for following dermatome levels • S1 • L1 • T10 • T6 • T4 • T1-2 • C8 • C6
- S1—lateral aspect of foot
- L1—Inguinal ligament
- T10–Umbilicus
- T6—Xyphoid process
- T4—Nipple line
- T1-2—Inner aspect of FA
- C8—5th finger
- C6—Thumb
Concern w/ sensory alteration at C6 and location
At thumb
C3-C5 = phrenic nerve
Can affect respirations
What should be done if pt feels effects up to C6/5
Raise head of bed
What is the Puffier line
A line drawn across the superior iliac crest that crosses the body of L4 or the interspace of L4-L5
does not change in the scoliosis pt
How to assess superior iliac crest in the morbidly obese pt
- ask them to show you where their hips are
- can you feel the bone
-Crease at the top of the buttocks?
General pharmacology and mechanisms principles for SAB
Spinal nerves in SA space covered by thin pia layer
LA injected to cauda equina
and spreads to the nerve roots
Spinal nerves are susceptible to injury
Small amount of LA can cause intense blockade
What does LA drug selection depend on for SAB
type of surgery
length of the surgery
surgeon
SAB dosing w/ bupicacaine 0.75% to extend to T10 and T4.
How many ml for the dose range?
How many ml if 15 mg bupiv given
T10
8-10 mg
1-1.33 ml
T4
12-20 mg
1.6-2.67 ml
15 mg = 2 ml
What are some additives to SAB and purpose of each
Vasoconstrictor
• Use to prolong block
Opioid
• Use to intensify the block
What is the MOA, type and purpose of opioid additive to SAB
LA and Opioid
synergistic effect in the intrathecal space
Binds to mu receptors
Selectively modulates nociceptive afferent inputs from A and C fibers
Types
Hydrophilic
lipophilic
Mechanism of morphine action in SAB and disadvantages
Is hydrophilic
long duration of action due to
• low SC distribution volume
• slow clearance to plasma
Spreads into the intrathecal space
Disadvantage
Rostral spread to the brain
• “Delayed” respiratory depression
Dosing and side effects of morphine additive to SAB
Dose
• 0.1 - 0.5 mg
• Increasing dose - increases side effects
Side effects • N/V • Pruritus • MOST COMMON • Respiratory depression
MOA of fentanyl/sufentanyl w/ SAB
- Lipophilic agents
- Rapid spread to the spinal cord
- Rapid rostral spread
- early respiratory depression
Advantages of fentanyl use in SAB
- Small doses intensify the block w/o prolonging it
- Reduces LA dose
- Faster sensory and motor recovery
Indications and dosing for sufentanyl w/ SAB
Same advantages as fentanyl
• Mostly used in labor and C-section
• 2.5 - 7.5 mcg - labor
• 2.5 - 10 mcg for c-section with low concentration bupivacaine
Side effects of intrathecal fentanyl/sufentanyl use w/ SAB.
Most common
- Respiratory depression
- Pruritus (most common)
- N/V
MOA of vasoconstrictor use w/ SAB.
Drugs commonly used and dosing
Effects w/ tetracaine, bupiv, lido
Prolongs action of the LA
by reducing blood flow
Decreases CV absorption
Dosing
Epi = 0.2 - 0.3 mg/ “epi wash”
Neo = 2 - 5 mg/ “neo wash”
W/ Tetracaine
profound increase
With bupivacaine or Lidocaine
variable increase
What is most important when performing SAB
ALWAYS HAVE GETA BACKUP
What alpha 2 agonist adjuncts may be used w/ SAB
Clonidine
Dexmeditomidine
MOA of clonidine w/ SAB
Side effects and dosing
acts on the substansia gelatinosa
Intensifies AND prolongs sensory and motor block
Side Effects
Hypotension, bradycardia and sedation
Dose
15 mcg
Where are alpha 2 receptors located
Presynaptic neuron at Lamina II of dorsal horn in SC
Benefit of alpha 2 agonist vs opioid adjuncts w/ SAB
alpha2 agonist don’t cause respiratory depression
MOA of dexmeditomidine
Dose
Has similar effect/side effects in prolonging blocks
Dose=3 mcg
Basic process of uptake and elimination of SAB meds
LA injected into SA space
Injected to the cauda equina
Spreads to the spinal nerve roots
What are factors affecting uptake of LA w/ SAB (4)
Rationale for each
Concentration of LA in the CSF
Faster uptake w/ higher concentration
2% > 0.75%
Surface area of the neural tissue
Inc area = more uptake
Lipid content of the nerve
Higher content = more uptake
Blood flow of the nerve
More flow = more uptake
How to assess level of SAB
Use something cold to determine dermatome level
Explanation for pt movement following SAB
Pt may have adequate sensory block
Motor block occurs after sensory b/c order of fibers
What are the principles of differential block w/ SAB
Nerve fibers differ in their sensitivity to LA
Gradual and segmental block
• different nerve fibers when exposed to LA
Smaller diameter axons = more sensitive
Myelinated fibers = more susceptible than non-myelinated
Order of loss w/ block
autonomic
sensory (pain/temp)
motor
Describe the arrangement of nerves in a bundle and how does this relate to SAB
B-Fibers = outer nerves
C-Fibers = 2nd nerve
A-delta fiber = 3rd level
A-alpha/beta/gamma = central
What are each of the following nerves responsible for B fiber C fiber A-Delta fibers A-alpha A-beta A-gamma
B fiber = autonomic (physiologic) C fiber=pain/temp (sensory) A-Delta fibers=pain/temp (sensory) A-alpha = motor tone A-beta= touch/pressure A-gamma = motor function
What are sensory fibers
Physiologic
Motor
Sensory:
C fiber
A-delta fiber
A-beta fiber
Autonomic/physiologic:
B fiber
Motor:
A-gamma
A-alpha
Function, myelination and SAB order of A type fibers
alpha, beta, delta, gama
alpha = proprioception, motor; heavy; last
beta = touch, pressure; heavy; intermediate
gamma = muscle tone; heavy; intermediate
delta= pain, temp, touch; heavy; intermediate
Function, myelination and SAB order of B fibers
Preganglionic autonomic vasomotor
Light
Early
Function, myelination and SAB order of C fibers
Postganglion vasomotor
Pain, temp, touch
None
Early
How are the levels of sympathetic, sensory and motor level block related w/ SAB
Zones of Differential Block r/t sensory level -Sympathetic level 2-6 levels higher Sensory -Motor level 2 levels below
Describe recovery from SAB
- Reverse sequence
* Motor recovers first
Process of elimination of LA following SAB
Elimination of LA from CSF
Vascular absorption
• via SA and epidural blood vessels
General factors that affect intrathecal spread
We need to decide which LA to use for planned surgery
Take into consideration the dose and the length of surgery
Surgeon
As we age, what physiologic aspects affect SAB (4)
- With advanced age=neural nerves are vulnerable to LA
- Number of myelinated nerves decreased
- Conduction velocity in motor nerves decreased
- CSF volume decreases and specific gravity increases
What effects does age have on SAB intrathecal spread
Faster onset
Higher level of blockade
Longer lasting anesthesia
How does height affect LA spread w/ SAB
Normal-sized adult
height does not play a role in LA spread
In extreme cases
length of the spinal column may affect the spread
How does weight affect LA spread w/ SAB
- The LA spread is influenced by high BMI
* The abdominal mass of obese patient decreases CSF volume
What is the difference between spread and uptake of LA w/ SAB
Spread = from site of LA injection to the top of where it extends
uptake = absorption
How does CSF volume affect spread of LA w/ SAB
Normal CSF
Small CSF volume
• Correlates to extensive spread of LA in intrathecal space
• Maximum spread of anesthetic is higher
100 to 160 mL in adult humans
Which pressure-volume loop would be most likely to correlate to increased spread
The restrictive loop (small)
associated w/ morbid obesity
How does site of injection affect spread of LA w/ SAB
Site note recommended and why?
Higher site of injection spreads higher than lower injection
• L2-L3 = spread is higher compared to L4-L5
Not recommended
• Spinal injection site higher than L3
• L3 and higher injection site caused neural damage
What is barbotage and How does it affect LA spread w/ SAB
- Aspirating CSF before injecting LA
- Mixing the LA and CSF in syringe
- Found not effective
How do you know CSF is present with barbotage
CSF is warm…
How does the dose of LA affect the spread during SAB
larger dose increases
• the spread of LA
• the level of anesthesia
• the block duration
What is density
Density is a physical characteristic
• weight in gram of 1 mL of a solution
• at a specified room temperature
What is baracity
Correlate to LA/CSF
- Relationship of density btwn LA and CSF
- LA density > CSF = HYPERBARIC
- LA density < CSF = HYPOBARIC
- LA density = CSF = ISOBARIC
Should baracity of LA be taken into consideration for epidural anesthesia
NO b/c no CSF
How can you determine the baracity of LA
NS = isobaric
Sterile water = hypobaric
dextrose = hyperbaric
Describe the activity of iso, hypo and hyperbaric LA and their relation to CSF
Isobaric – “Stays where you put it”
LA density or specific gravity = CSF
Hypobaric – “Floats” up
Lighter than CSF
LA has a density or specific gravity < CSF
Hyperbaric – Settles to Dependent aspect of the SA space
Heavier than CSF
LA has a density or specific gravity > CSF
label each picture of slide 56 and 57. Which is iso, hypo or hyperbaric
pics
What factors affect spread of LA w/ SAB (8)
- Age
- Height
- Weight
- CSF properties
- Site of injection
- Barbotage?
- Dose of LA
- Baracity
Cardiac effects r/t the heart d/t SAB
- Dec SVR
- Dec preload
- Dec RH pressures
- Dec CO
Why do CV effects occur w/ SAB
loss of sympathetic activity
• accompanies a spinal anesthetic
• results in vasodilation below the level of blockade
Peripheral CV effects d/t SAB
Arterial and venous dilation
• Venodilation > Arterial dilation
• Veins contain 75% CV volume
Rationale for hypotension d/t SAB
Sympathectomy (T1-T4) • causes arterial and venous dilation High block • can cause unopposed bradycardia Bradycardia + hypotension = not so good
What are HR risk factors r/t SAB
BRADYCARDIA
• Baseline HR < 60 beats/min
• Use of β-adrenergic receptor blocking agents
• Prolonged PR interval
• Sensory level above T6 (sympathetic 2-6 levels above**)
What is preloading and co-loading in r/t SAB management
preloading = volume before SAB
co-loading = volume WITH SAB
What is the management of CV effects of SAB
- NOT normovolemic=Give IV fluids if
* Normovolemic = give ephedrine (more effective)
Volume management principles for CV effects of SAB
Volume for initial treatment of hypotension
• from balanced salt solutions
• do not contain glucose
Are glucose solutions indicated for CV effect management w/ SAB? Why or why not
No
b/c “we don’t want them to pee”
Can lead to hypovolemia
Pharmacologic management of CV effects w/ SAB and rationale
Phenylephrine:
• alpha agonist
If HR is normal or elevated
• causes an increased SVR w/o HR
Ephedrine:
mixed alpha and beta agonist
if bradycardia
will increase HR and increase PVR
50 mg of ephedrine in 1 ml vial
Mix to get 5 mg/ml
How much NS?
Mix w/ 9 ml NS to get 5 mg/ml
What can affect mortality r/t CV effects of SAB
Increase mortality
• Can be d/t Failure to treat or delay treatment
What should be done if HTN results from ephedrine or neo use when pt has SAB
• it must be managed with vasodilators, narcotics, and anxioloytics
What is the decreased of bleeding/DVT due to when a spinal is in place
The vasodilation effect of the epidural causes slower bleeding (he says in his second lecture)
Intentionally lowering BP to decrease the chance of bleeding
At what point does a SAB affect respirations and why. How can this affect the healthy vs chronic dx adult
Cephalad mov’t of block paralyzes
• the abdominal muscles
• intercostal muscles
Pulmonary alterations
• in healthy adult are of little clinical significance
What potential pulmonary complications may occur as SAB moves cephalad
Increase the potential for hypoxia when loss of:
• Phrenic nerve paralysis (C3-C5)
• loss of accessory muscles of ventilation
High Spinal
• Decreased FRC d/t paralysis of abdominal muscles
• as the sensory block reaches the level of T2-T4 (sympathetic fibers that supply lungs)
• Loss of perception of intercostal and abdominal wall movement May cause the patient to feel dyspneic
What can happen to pt w/ lung disease that experiences high spinal
Dec FRC
Dyspnea
What are causes and alterations w/ high spinal
Cause:
- Sensory and sympathetic nerve block that supply the lung at the T2-T4 level
- —— loss of perception of intercostal and and wall muscles causing dyspnea - Paralysis of abdominal muscles
- —–Decreased FRC
Tips to prevent or negate high spinal
Raise head of bed
–esp w/ hyperbaric LA, will settle w/ gravity
Prevention, intervene before symptoms start
Mechanism and effects of altered thermoregulation d/t SAB
- -SAB impairs central thermoregulation
- -Hypothermia that is d/t peripheral redistribution of blood flow and heat d/t vasodilation
- -Leads to shivering
Options to address thermoregulation alterations w/ SAB
Bair hugger (careful, not too hot)
Ondansetron (also prevent HoTN and low HR)
What are your general preparations prior to SAB (3)
Preparation and monitoring patient
Prepare drugs and equipment
Always have a general anesthesia set up
Considerations when preparing pt for SAB preoperatively
Assess patient
• What is the surgery?
Review history
• Anticoagulants and Antiplatelets
Informed consent
• Tell pt complications/risks—spinal HA, hematoma
When preparing pt for SAB, what considerations for sensory level block should be considered.
–What is the surgery
What are the corresponding surgeries for each dermatome level
S2-S5-- S3-- S2-- L2-- L1-- T10-- T8-- T6-- T4--
S2-S5–Peri-anal/anal surgery (saddle block)
S3–Scrotum
S2–Penis
L2–Foot/ankle surgery
L1–Thigh/lower leg/knee
T10–Vag delivery/uterine/hip/tourniquet
T8–Testicular procedures (embryonically derived from T10-L1 like kidneys)
T6–Uro/Gyn/lower abd
T4–Upper abd/C-section
- Peri-anal/anal surgery (saddle block)
- -Scrotum
- -Penis
- -Foot/ankle surgery
- -Thigh/lower leg/knee
- -Vag delivery/uterine/hip/tourniquet
- -Testicular procedures (embryonically derived from T10-L1 like kidneys)
- -Uro/Gyn/lower abd
- -Upper abd/C-section
S2-S5–Peri-anal/anal surgery (saddle block)
S3–Scrotum
S2–Penis
L2–Foot/ankle surgery
L1–Thigh/lower leg/knee
T10–Vag delivery/uterine/hip/tourniquet
T8–Testicular procedures (embryonically derived from T10-L1 like kidneys)
T6–Uro/Gyn/lower abd
T4–Upper abd/C-section
- -Scrotum
- -Penis
- -Foot/ankle surgery
- -Uro/Gyn/lower abd
- -Upper abd/C-section
- -Thigh/lower leg/knee
- -Vag delivery/uterine/hip/tourniquet
- Peri-anal/anal surgery (saddle block)
- -Testicular procedures (embryonically derived from T10-L1 like kidneys)
- -Upper abd/C-section
S3–Scrotum
S2–Penis
L2–Foot/ankle surgery
T6–Uro/Gyn/lower abd
T4–Upper abd/C-section
L1–Thigh/lower leg/knee
T10–Vag delivery/uterine/hip/tourniquet
S2-S5–Peri-anal/anal surgery (saddle block)
T8–Testicular procedures (embryonically derived from T10-L1 like kidneys)
What type of needle is common for SAB insertion.
Why is this needle used. How should it be inserted
Connical aka pencil tip
WHITAKER
Beveled end
Very small gauge (25, 27)
Insert bevel up to direct meds cephalad
Beveled needle orientation w/ insertion for blocks
bevel facing cephalad to direct medication up
What type of LA solution would be best for foot/ankle or thigh/knee surgery when doing a SAB
Isotonic solution
“because you’re already there”
What is the most important aspect of preparing a pt for SAB
positioning
positioning
positioning
Describe the sitting position for SAB placement
- With Legs hanging over side of bed
- Patient hug a pillow
- Put Feet up on a Stool (no wheels)
- Assistant MUST keep the patient from Swaying
- Curve her back like a “C”
- Up in the Bed (quicker but not optimal)
When would the lateral position be appropriate for SAB insertion
Describe the position
Hip surgery, poor spine flexion
- Needs to be Parallel to the Edge of the Bed
- Legs Flexed up to Abdomen
- Forehead Flexed down towards Knees
What is the order of layers traversed by the needle w/ the median approach for SAB
- Skin
- Subcutaneous fat
- Supraspinous ligament
- Interspinous ligament
- Ligamentum flavum
- Dura Mater
- Subdural space
- Arachnoid Mater
- Subarachnoid space
Which layers are not traversed with the paramedic approach vs the median approach for SAB insertion
Supraspinous ligament
Interspinous ligament
What layers are traversed fly the needle for SAB via paramedic approach
- Skin
- Subcutaneous fat
- Ligamentum flavum
- Dura Mater
- Subdural space
- Arachnoid Mater
- Subarachnoid space
What spinal cord ligaments will never be touched by the spinal needle
Anterior ligament
Posterior ligament
Why is introducer used for SAB
because the spinal needle is so small it would not make it through all the layers
What is the fist ligament past via the median approach of the SAB
Interspinous ligament
What is the last ligament passed before epidural space
Ligamentum flavum
Sign that needle has passed through ligaments flavum
Pop
Sign that needle is in SA space
CSF drip (when stylet is removed)
Why is a stylet in the spinal needle
Prevent clotting of needle
Remove when in SA space
When CSF is mixed w/ LA for SAB…
Describe
Barbotage
Hyperbaric = swirl
iso/hypotonic = inc volume
Describe the parmesan approach for SAB
Same process except more lateral approach
Spinal needle will be inserted further than w/ midline
Difference in spinal and local infiltration syringe
Spinal syringe is smaller
Once needle is in w/ SAB what should your hands do
stabilize the needle by anchoring a hand/finger on the pt
Why are the spinal needle and introducer removed together
to prevent debris from microscopic “shredding”
What are complications of SAB (7)
- Backache
- Postdural puncture HA
- Systemic toxicity
- Total spinal anesthesia
- Transient neurologic symptoms
- Cauda equina syndrome
- Spinal hematoma
What leads to backache following SAB
- Repeated needle insertion by provider (needle trauma)
- Local anesthetic irritation
- Ligamentous strain d/t muscle relaxation
What needs to be included when performing the informed consent
The risks/complications
esp, backache, postural HA, spinal hematoma
59 minutes
pg 16
postural HA
Why is surgical positioning of a pt important to the CRNA
- It’s our respondsibilty
- Joints should be in natural alignment or padded to prevent injury
- There are paths changes that can occur
- Safety belts must be used
- Nerve injury can happen quickly and may be irreversible
What should the anesthetist consider prior to positioning pts
The PROCESS FROM HEAD TO TOE
PROPER POSITIONING DEVICES
HOW MUCH HELP IS NEEDED
Which position is the most common surgical position
Supine
Requirements for armboards
Armboards
They must be secure if in use
What are pathophysiologic alterations to CV and pulm systems in supine position
- ↑ VR, preload, SV, and CO
* ↓Vt, ↓ FRC
Describe the guidelines for arm abduction positioning
Out to the side
• < 90 degrees
Padded armboards
• secured to the table and patient at the axilla
The arms should be supine (palms up)
Elbows padded
Arm is secured with a Velcro strap
Describe guidelines for arm adduction positioning
Tucked alongside the body
Arms held along the side of body
• via draw sheet under the body and over the arm
Hand and forearm
• supine (palms up)
• neutral position (palms toward body)
Elbows are padded
• may also tuck one arm
• if surgeon must stand on side of patient
Complications from supine malpositioning
Back ache
Pressure alopecia
Nerve injuries
Stretch injuries
What are specific nerve injuries and stretch injuries that can occur d/t supine positioning
Nerve injuries • Arms abducted >90° Brachial plexus axillary nerve injury • hand/arm is pronated Ulnar nerve injury
Stretch injury
• when neck is extended
• head turned away (C5-T1)
Guidelines for trendelenburg positioning
Similar to supine (padding and alignment) but tilt the head of the patient ↓
Use a non-sliding mattress To prevent patient from sliding
Securement/sliding prevention
• Taped or used shoulder braces
Monitor for pt sliding (use of tape or mark on sheet at head)
Edema considerations and CV alterations d/t trendelenburg positioning
Edema
• face, conjunctiva, larynx, and tongue
• d/t time or volume
- ↑ MAP, SVR, and ICP
- ↑ VR from blood in the lower extremities
What are some pulmonary alterations d/t trendelenburg positioning and how are those treated
↓ lung volumes ↓ pulmonary compliance ↓ FRC B/c diaphragm shifted superiorly • Risk of endobronchial intubation from abdomen pushing carina cephalad
Treat:
Higher pressures in ventilated patients
To maintain volumes
In addition to CV and pulm alterations what is an important consideration/complication w/ trendelenburg positioning.
Recommendation for prevention of this issue
• Possibility of postoperative visual loss (POVL)
• Prevention
decreasing the amount of tilt
periodically placing the patient level for a specified period of time
Important guidelines for reverse trendelenburg positioning
Same as supine (alignment and padding)
with tilt the head of the patient ↑
Slide prevention
• Use a foot rest
• something under the feet
CV effects of reverse trendelenburg positioning
↓ preload and CO
d/t venous pooling in the LE
Pulm effects of reverse trendelenburg positioning
Downward displacement of abdominal contents and diaphragm =
↓mean thoracic pressure
↓work of breathing
↑FRC
Cerebral considerations with reverse trendelenburg positioning and why
↓ perfusion to brain
• Concern w/ long case or hypotensive pt
Which procedures may utilize the sitting position
shoulder
neuro
some ortho
Guidelines for body placement when pt is in sitting position
Head = cradle or pins Knees = slightly flexed for balance and prevent sciatic stretch Feet = supported to prevent sliding
What additional requirements are needed for the pt in sitting position
Compression stockings to maintain VR
At least 2 fingers distance btwn chin and sternum (to prevent spine issues?)
Describe the modification option for the sitting position
BEACH CHAIR position
• used frequently in shoulder cases
• less severe hip flexion
• slight leg flexion
Nerve complications of sitting position
- Sciatic nerve injury
* Neurologic and cervical spine injuries
Pathophysiologic considerations for pts in sitting positions
- Improved ventilation in non-obese patients
- ↓ VR, CO, and CPP
- Hypotension risk
What procedures may utilizes the prone position
Spine
Rectal fissures
Achilles
Proper initial positioning of pt in prone
Patient lying on stomach in “superman” position
Don’t completely stretch out arms
should be < 90 degrees
Guidelines for body placement w/ prone position
- Superman
- Arms outishand <90 dg
- head supported
- legs padded, slightly flexed at knees/hips
Guidelines for head placement with prone position
Head supported face down • using a prone pillow • neutral position • No pressure on eyes, face, and ears Commercially made ProneView other prone pillow
• Do not turn the patient’s head
Risk occlusion of jugular or carotid
Risks if pt head turned during prone case
Risk of jugular or carotid occlusion
Patient equipment for prone position
- EKGk leads on their back
- Intubate while supine then turn prone
- Prevent ETT dislodgment by reconfirming position after turning prone
Guidelines for airway w/ prone position
- Intubate the patient
- supine on the bed
- then turn into prone position
- ETT dislodgement–reconfirm position once prone
Complications to consider for pts in prone position
Nerve injureis
Post-op visual loss
Eye injuries from head positioning
ETT dislodgment
What nerve complications can occur d/t prone positioning
Ulnar nerve injury
if elbows are not padded
Brachial plexus injury
if arms are abducted > 90 degrees
Cause of post-op visual loss following prone positioning
• d/t decreased perfusion/ischemia
what can poor head positioning in prone position lead to
- -eye injuries
- -Pressure injury to eyes, face, ears
- -occlusion to jugular or carotid
Pathophysiologic considerations for pts in prone position
- May reduce amount of fluid in the lungs
- -BUT extra fluid could overload heart
- Shift of ventilation/perfusion to dependent areas
- -V/Q mismatch
- Skin breakdown or blisters
- -from friction; pad
Procedures that may use the lithotomy position
GU
Hemorrhoid
Rectal
Guidelines for body placement in lithotomy position
–Pt supine
–Legs in stirrups
–Arms tucked on armboard
–may use Tburg or reverse Tburg
LE placement
–Hip flexed 80-100 deg
–legs abducted 30-45 deg from midline
–knees flexed
What supports are used in lithotomy position and for what
Leg = padded or candy cane stirrups
Arms = armboard
Describe leg positioning guidelines for lithotomy position.
Very important consideration to remember during LE positioning.
- Hips flexed 80-100 degrees
- legs abducted 30-45 degrees from midline
- knees flexed
Lower extremities MUST be raised/lowered in synchrony
To prevent pressure/stress on LE
What precautions should the CRNA take when the foot of the bed is lowered for a pt in lithotomy position
• Protect the hands and fingers from crush injury
Guidelines for pt care in lithotomy position during long cases.
Rest Periods in long cases
• to level the patient
• lower the lower extremities
• Maybe not during robotic surgeries
Complications that may result from lithotomy position
lower back pain
nerve injuries
compartment syndrome
what nerve injuries may occur as a result of lithotomy position
- Brachial plexus injury
- Ulnar nerve injury
- Common perineal injury (foot drop)
- Lateral femoral cutaneous injury
Pathophysiologic considerations for pts in lithotomy position
CV, pulm, and Tburg/reverse considerations
CV
• ↑ VR, preload, SV, CO, AND ICP
Pulm
• ↓Vt, ↓ FRC
• Exacerbated by obese abdominal body habitus
Cardiovascular and pulmonary changes
• May occur with further positioning in Trendelenburg or reverse Trendelenburg
What vascular assessment should be performed in prone, lithotomy and lateral decubitus positions
Check pedal pulses preoperative
and once placed in position to ensure there isn’t decreased perfusion
Examples of procedures that would utilize lateral decubitus positioning
thoracotomy
nephrectomy
hip replacement
Which side is down in a right lateral decubitus position
right side is down
Guidelines for body placement during lateral decubitus positioning
- Lying on side w/ anterior or posterior support
- Head support w/o pressure to ears and eyes
- -check dependent ear
- Dependent leg slightly flexed
- arms are in from and supported, abducted 90deg
- Axillary roll
- Pillow between knees
What positioning aids may be needed for lateral decubitus positioning
- Anterior/posterior roll or bean bag
- Head support
- Axillary roll
- Pillow between knees
Describe the axillary roll used in lateral decubitus positioning. Purpose and placement.
Axillary roll
to prevent brachial plexus compression
placed between chest wall near nipple line and bed
should NOT be placed in the axilla despite the name
Possible complications of the lateral decubitus position
Inferior vena cava compression
Nerve injuries
Eye or ear injuries
ETT dislodgement
Cause of inferior vena cava compression in lateral decubitus position
Kidney rest
Bed flexed
What nerve injuries may occur from lateral decubitus positioning
Ulnar nerve injury
if elbows are not padded
Brachial plexus injury
if arms are abducted > 90 degrees
What should be assessed after the pt has been positioned in the lateral decubitus position
Assess airway
Make sure ETT has not dislodged
Pathophysiologic considerations for pts in the lateral decubitus position
CV
• ↑ VR, preload, SV, and CO
Pulm
• ↓Vt, ↓ FRC
• V/Q mismatch d/t
inadequate ventilation to dependent lung
decreased blood flow to the nondependent lung
What are the most common peripheral nerve injuries r/t positioning
- Ulnar nerver
- Brachial nerve
Why do peripheral nerve injuries occur
stretch
pressure
ischemia
unknown
Can occur in as little as 30 minutes
Incidence of HA w/ SAB vs epidural blocks.
What is the cause in this difference.
HA incidence is LESS frequent in spinal anesthesia vs epidural anesthesia
B/c of needle size difference. Epidural is much larger than SAB (25g or 27g)
–Likelihood of dura closing is less w/ larger needle
What leads to post-dural HA s/p epidural
- -Result of accidental dural puncture (“wet-tap”)
- -Use of larger needles w/ epidural
What symptoms can a “wet-tap” lead to
HA
Pain that radiates in neck
N/V
What symptoms are characteristically associated w/ post-dural puncture HAs
- HA:
- -Mild or absent when supine
- -w/ elevation = severe fronto-occipital HA
- Neck pain:
- -Pain radiates to neck causing stiff neck feeling
-N/V
- Double vision
- Tinnitus
- Seizures if severe
What is the mechanism leading to the post-dural HA
-Low CSF leading to CN traction
What causes visual changes w/ post-dural HA
Traction causes failure of the affected eye to ABDuct leading to diplopia
CN VII (abducens)
What CN are affect by “wet-tap”
CN VI (abducens)
CN VIII
What can a wet-tap lead to
Low CSF volume
Diploplia
Tinnitus
Seizure
In rare cases wet-tap can lead to seizures. Why
Caused by cerebral hypotension from dural puncture that leads to cerebral vasospasm
What are most common d/dx of post-dural complications
Nausea = 60% Vomiting = 24% Neck stiffness = 43% Ocular = 13% Auditory = 12%
Etiology of pst-dural puncture HA
- Loss of CSF volume
- CSF leak > production
- Cerebral vasodilation as CSF vol decreases
- vasodilation causes pain
what are risk factors for pts prone to post-dural HA
- Age (young > old)
- Gender (female > male)
- H/o previous post-dural HA
- Needle design/size (large > small)
- Multiple dural punctures
Why is post-dural puncture HA more common in young pts
b/c older pts have more inelastic dura so it is less likely to “break”
Treatment options for post-dural puncture HA
- Position = supine
- Meds = NSAIDS, Narcotics
- Caffeine
- Blood patch
Precautions w/ use of caffeine for post-dural puncture HA
How much caffeine and examples of dosing
Caution for elderly and those who can’t tolerate CNS/cardiac stimulation
300-500 mg of oral/IV caffeine once or BID
1 cup coffee = 50-100 mg caffeine
Black tea= 60-90 mg
Soft drink = 30-50 mg
What is a blood patch?
How is this performed?
Pts blood is used occlude puncture
-Blood will clot and occlude the perforation preventing further CSF leak
Patient in the lateral position
the epidural space is located
with a Tuohy needle at the level of the dural puncture
or an intervertebral space LOWER so blood will go up to perf
• 20 ml blood is then taken from the patient’s arm
What leads to systemic toxicity w/ epidural anesthesia
Preventative measures
- Very rare w/ spinal b/c drug dosages are low
- More common w/ epidural anesthesia b/c
- -higher dosage
- -epidural veins inc risk of intravascular injection
Prevention:
Reason why test dose and incremental injections
Where is blood injected for blood patch
Epidural space
Complications of total spinal anesthesia
-Profound hypotension and bradycardia are common secondary to complete sympathetic blockad
Respiratory arrest
What is transient neurologic symptoms and etiology
Pain, in the legs or buttocks after spinal anesthesia
Greater with lidocaine
The mechanism responsible is unknown
What is caudal equina syndrome, symptoms and etiology
Etiology
Pooling of toxic concentrations of undiluted lidocaine
• around dependent cauda equina nerve roots
Symptoms • Low back pain • weakness • sensory deficits • Bowel and bladder dysfunction
Cause of spinal hematoma
How can it be prevented
Cause:
coagulopathy, r/t medications or history
Can lead to paralysis
Prevention:
thorough history and assessment. Are they on anticoags or have altered labs
Chose which..Epidural or SAB
1. Which would you use for a 5 hr case
- Which is fast in onset
- Which has more risk for systemic toxicity
- Which has greater risk for post-dural puncture HA
- Which takes longer to perform
- Epidural
- Spinal
- Epidural
- Epidural
- Epidural
Advantages of epidural vs spinal anesthesia
- Can do at almost any level of the spine to target specific dermatomes
- Allows titration of the block d/t Cath insertion in epidermal space
- Continuous postop analgesia
Disadvantages of epidural vs spinal anesthesia
- Longer time to perform epidural
- Slower onset
- Less dense block
Contraindications for epidural block
- Similar to SAB
- PT REFUSAL = ABSOLUTE
- Tattp (<6 mo = NO!)
Where does the epidural space begin and end
Begin = Base of skull @ foramen magnum
End = Sacral hiatus (S2)
When inserting needle from posterior, which comes first subarachnoid or epidural space
epidural space (dura mater–arachnoid mater–subarachnoid space)
What are the contents in the epidural space
Fat Areolar tissue Lymphatics Veins Nerve roots Blood vessels
What population is more likely to be prone to blood vessel puncture w/ epidural block and why
- common in pregnant patient
- d/t engorgement of the epidural veins
- from caval compression
What approach is more likely to result in blood vessel puncture
The off-midline paramedic approach
What is the last ligament before the epidural space
Ligamentum flavum
How does spinous process orientation differ btwn cervical vs lumbar vertebrae
What does this mean for needle insertion
Cervical AND lumbar = horizontally directed
–Needle entry = direct horizontally
Thoracic SP = Sharp caudal angulation
–Needle entry = point cephalad and use paramedic approach
What is the safest point of entry when performing Epidural Block
Difference in adults/peds
BELOW THE LEVEL OF THE
SC
Adults = lower L1 border Peds= Lower L3 border
General physiologic effects of an epidural block
Sensory and motor block
Central and peripheral sympathetic block
What nerve fibers are associated w/ central vs peripheral sympathetic block
Central = T1-T4
Peripheral = T5 - L4
Chronotropic, inotropic and dromotropic differences
chronotrop = rate
inotropic = contractility
dromotropic = speed of conduction
What are CV effects r/t epidural block
- Loss of motor tone DECREASES blood flow to organs
- Effects depend on level of block
- -HIGH thoracic= thoracic myocardial effects
- —-loss of chronotropic and inotropic drive
- -LOW thoracic = Vascular dilation
- —-Dilation of pelvis and lower limbs (BELOW block) can affect organ perfusion?
What CV effects are r/t high thoracic block and at which levels
Level = T1-T4
Effects on CARDIAC sympathetic activity
- -block segments of CARDIAC REFLEXES
- -blocks outflow from VASOMOTOR center to CARDIAC sympathetic fibers
CV effects on vasculature with an epidural block
- Veno/arterial vasodilation
- -DEC SVR
- -Venous > arterial dilation
- Venous pooling
- -DEC VR, RA pressure, CO
What does venous pooling lead to
–DEC VR, RA pressure, and CO
When using a thoracic approach for epidural block decrease HR and hypotension are noted.
What are the physiologic effects and how should it be treated
Effects:
DEC VR, RA pressure, CO
Tx:
O2, fluid, ephedrine (b/c HR is low)
What are preemptive interventions when noting gradual decline in HR and BP w/ epidural block above T4
O2, fluids and leg elevation
Have ephedrine ready
Sudden decrease in HR can cause what? How is this treated? Why does it occur?
Causes:
- Profound dec in VR
- can lead to cardiac arrest
Tx:
O2, fluids, elevate legs, Atropine and/or ephedrine
D/T:
B fiber sympathectomy
What are the determinants of epidural block spread
- Site of injection
- Volume/dose of LA
Injection consideration when performing a thoracic epidural block
- Produces symmetrical spread of solution
- Use less volume b/c potential for higher block and resultant hemodynamic instability
- Needle inserted at cephalad angle (d/t SP angle)
Injection considerations when performing lumbar epidural block
-There is preferential cephalad spread d/t narrowing of epidural space at lumbosacral joint
- Delay onset may be d/t larger diameter of the L5-S1 nerve roots
- -Can cause patchy anesthesia
-Direct catheter cephalad
How does LA volume relate to epidural block
larger LA volume = more segments blocked
LA volume considerations w/ lumbar vs thoracic epidural block injections
Lumbar injection:
- Recommended bolus vol = 10-15 ml (incremental)
- -Will cause mid-thoracic block (T6@xyphoid)
Thoracic injection:
- Recommended bolus vol = 5 ml to start
- -Need less volume to achieve higher block
Principles and rule for dose injection w/ epidural blocks
• Dosing is incremental for all epidural blocks
Only after a negative aspiration for CSF and blood
Rule 1–2 mL per segment to be blocked i.e. to achieve a T4 (nipple) sensory level from an L4-5 injection L4 to T4 = 12 segments ~ 12–24 mL of LA given incremental dosing
How much LA would be given to achieve a block at nipple line (which level is this) from L4-L5 injection
i.e. to achieve a T4 (nipple) sensory level from an L4-5 injection
L4 to T4 = 12 segments
~ 12–24 mL of LA given
What are purposes of adding adjunctive meds w/ LA for epidural blocks
- Prolong epidural block (Vasoconstrictor)
- Improve quality of blockade (Opioids)
- Accelerate onset of blockade (alkalization)
What medications can be added to prolong an epidural block.
What specific effects to these meds have w/ LA
- Epi increases duration
- -GREATEST w/ lido, mepiv, 2-chloro
- -some w/ bupiv, levobu, etido
- -Ltd w/ ropiv
Phenylephrine
- less used
- not as effective
What medication addition can accelerate LA onset w/ epidural block.
What is the MOA
Alkalinization w/ NaHCO3 (1 mEq/10 ml LA)
Effects INCREASE:
- pH (lower H+)
- Nonionized concentration
- Diffusion rate b/c more nonionized
- Onset speed
Which LA would alkalinization not be useful
When using Ropivacaine
B/c of Ropiv structure
Why does 3% 2-Chloro have a faster onset
because concentration is higher
Onset AND duration (plain) in min:
3% 2-chloro 2% Lido 2% Mepiv 0.5-0.75% Bupiv 1% Etido 0.75-1% Ropiv 0.5-0.75 Levo
3% 2-chloro—10-15//45-60
2% Lido—15//80-120
2% Mepiv—15//90-140
0.5-0.75% Bupiv—20//165-225
1% Etido—15//120-200
- 75-1% Ropiv—15-20//140-180
- 5-0.75 Levo—15-20//150-225
When 1:200,000 epi is added to the following, what is the duration in minutes:
3% 2-chloro 2% Lido 2% Mepiv 0.5-0.75% Bupiv 1% Etido 0.75-1% Ropiv 0.5-0.75 Levo
3% 2-chloro—60-90
2% Lido—120-180
2% Mepiv—140-200
0.5-0.75% Bupiv—180-240
1% Etido—150-225
- 75-1% Ropiv—150-200
- 5-0.75 Levo—150-240
3 ml test dose totals for following LA w/ 1:200,000 epi in mg:
3% 2-chloro 2% Lido 2% Mepiv 0.5-0.75% Bupiv 1% Etido 0.75-1% Ropiv 0.5-0.75 Levo
3% 2-chloro–90//0.015
2% Lido—60//0.015
2% Mepiv–60//0.015
0.5-0.75% Bupiv–15-22.5//0.015
1% Etido–30/0.015
- 75-1% Ropiv–22.5-30//0.015
- 5-0.75 Levo–15-22.5//0.015
Which LA are shortest, intermediate, longest duration
Shortest:
2-chloro
Intermediate:
Lido, Mepiv
Long:
Ropiv
Bupiv
Which LA has the fastest and slowest onset
Fastest onset = 2-chloro
Longest onset = Bupiv**, Ropiv, Levo
If the sensory block target is T6 what is the reference level and where should you initially block
T6 = xyphoid process
You should block higher than T6 so that the block lasts b/c level drops with time
Which LA would be best for an emergency C-section, why and what is it’s structure
2-chloro – b/c of the 3% 2-chloro has the highest concentration of LA
ESTER
More rapid onset d/t higher pKa??
What is the reason that 2-chloro duration is so short
B/c it is an ester and is metabolized by plasma cholinesterase’s NOT the liver
What are draw backs w/ the use of 2-chloro and why
- Short duration d/t plasma cholinesterase metabolization
- decreased efficacy of subsequent epidural opioids d/t 2-chloro repeated dosing and binding to mu receptors
- Metabolite is PABA which can have greater incidence of allergic response
Describe the motor function effects from epidural block. How does it r/t SAB. Which medications are more or less effective?
-Takes longer to achieve motor blockade than w/ SAB
- Lido = GREATEST motor fan depression
- Ropiv = LEAST motor depression
Which LA would be best suited for a working epidural and WHY.
Which La would be best suited for complete motor block
Working epidural:
Ropivacaine
B/c it has the LEAST motor depression
Complete:
Lido
What are some techniques that can be used for better motor blockade
- Choose appropriate LA (lido)
- Increase dose of drug
- Repeat or Top-Up dose
- Use epinephrine
Surgeon performing knee surgery does not want the pt to move. Pt has epidural, what techniques can you use to ensure motor blockade is adequate
- Use appropriate LA (Lido is best)
- Increase the DOSE of the drug
- Repeat or top-up dose
- Use epinephrine
Difference in Touhy and Crawford needle for epidural insertion
Touhy = disposable 19 g
- wings at hub to help stabilize/insert
- Plastic stylet inside
Crawford = 19g reusable
-Metal stylet inside
Stylet = prevents clotting inside insertion needle
Anatomy of the Touhy needle
19 g
Wings
9 cm length
w/ 1cm Marks from tip to hub
What is the purpose of markings on touhy
So anesthetist can determine how deep the epidural space is once inside
helps gauge length of catheter for insertion
What is the average distance from skin to epidural space
What is the possible min to max distance between skin and E space
How is depth affected by habitus
4-6 cm
Min = ~3 cm Max= ~ 8 cm
Can be less w/ thin and more w/ obese
Describe the epidural catheter anatomy
Has markings to determine insertion distance 1 mark = 5 cm 2 marks = 10 cm 1 BOLD mark = 11 cm 3 marks = 15 cm 4 marks = 20 cm
How far should an epidural catheter be inserted into the epidural space.
If a pts epidural space depth his 5 cm, how much catheter will be inserted total
2-6 cm INTO space
7-11 cm TOTAL for catheter insertion (should be at bold 11 cm mark?)
Guidelines and principles for epidural catheter insertion
2-6 cm into epidural space
MIN distance increases risk of DISLODGMENT
MAX distance increases risk of UNILAT block or catheter kinking
Once epidural catheter is placed, what precautions should be taken
Remove touhy very carefully so that catheter does not come out also
What is the purpose of the LOR syringe
Since the epidural space is a potential space, it has negative pressure
Thus, when a syringe w/ air or saline is inserted to the epidural space level, the air or saline should lose resistance
Loss of resistance indicates epidural space
2 methods of identifying epidural space
LOR
Drop method
What is the drop method for identifying epidural space
Place drop of saline at the hub of the needle w/o syringe and advance
The epidural space should “suck” in the drop d/t negative Patm
Not widely used
Complications of using air w/ LOR syringe
Pneumocephalus
Which pts would be most appropriate for a paramedic approach for epidural block
Pts that can’t be positioned easily or cannot flex the spine d/t trauma or arthritis, for example
Pts w/ spine deformities such as kyphosis or prior lumbar surgery
What is a major difference. btwn spinal and epidural anesthesia
Needle size
Access point
TEST dose for epidural blocks
Why are test doses required w/ epidural blocks
To ensure:
- No unintentional intravascular injection
- No intrathecal LA injection
What are s/sx of intravascular injection of LA when doing epidural block.
What should be done
A change of HR by >/=20%
Tinnitus
Metallic taste
Circumoral numbness
How much is a test dose for epidural block
3 ml
Maybe w/ 1.5% lido w/ epi 1:200,000
What does a positive test dose indicate
That the LA is in the vein
OR
That the LA is intrathecal
Using 1.5% lido w/ 1:200,000 epi a CRNA notes a HR from 90 to 110. What could explain this
Intravascular injection of the LA w/ epi
Inadvertant intrathecal injection of lido when giving test dose for epi block would result in…
- Immediate, significant motor block (c/w SAB)
- Dense motor block w/in 5 min MAY lead to suspicion of SAB
If test dose is positive, what should the CRNA do
Remove needle and replace catheter
Complications associated w/ test doses for epidural blocks in peds, pregnancy, or pts taking B-blockers
Peds:
Peaked P waves
Changes in the T wave
Pregnancy:
Give after contraction is over b/c HR inc w/ pain
Beta-blocker pt
HR change may not indicate intravascular injection
Change in SBP >20 mmHg may be more indicative of IV injection
What is the appropriate loading dose for epidural block
Between 10-15 ml given in 3-5 ml increments
Waiting 3-5 min between each increment to assess response
What actions are taken if an epidural block is not complete.
Replace the catheter
Dont waste time trying to reposition
What measures can enhance sensory and block and improve quality/duration
Enhance sensory block:
Give 1/4 to 1/3 initial dose 15 min post initial bolus
Enhance quality/duration
Epi or HCO3 will speed onset and enhance block
Fentanyl will improve the quality
What changes is dosing may occur w/ continuous infusion
Lower concentration of LA
Opioids may be added
When is top-up dosing indicated
- Before “two-segment regression”
- -Given before the block REGRESSES
- -i.e. goal is T4 but sensory regression to T6
Once two-segment regression has occurred, how should the CRNA address this
Top-Up dose of 1/3 to 1/2 the initial loading dose to maintain the block
Initial bolus dose totaled 10 ml for an epidural block. Pt sensory block has regressed from nipple line to xyphoid, how much LA should the CRNA give
5 ml (1/3 -1/2 initial bolus)
Recommended top up time (in min) for lido 2-chloro mepiv bupiv/ropiv
lido–60
2-chloro–45
mepiv–60
bupiv/ropiv–120
What are advantages of continuous infusion epidural anesthesia
- -Hemodynamic stability
- -can be continued post for analgesia
Technique for assessing sensory and motor block
sensory:
- pin-prick (avoid)
- Alcohol swab (TEMP loss w/ pain)
Motor block: Bromage scale 0 = moves hip, knee, ankle 1 = no hip, moves knee/hip 2 = no hip/knee, ankle 3 = no hip/knee/ankle
How is CSE performed
- Perform spinal w/ Tuohy
- Once at epidural space insert spinal needle through touhy into SA space
- After barbotage give LA for SAB
- Pull spinal needle BUT keep touhy
- Insert epidural cath
