Unit 8: Regional Anesthesia Flashcards
1
Q
What are the 5 divisions of the spinal column? How many vertebrae are present in each?
A
Cervical = 7
Thoracic = 12
Lumbar = 5
Sacrum = 5 fused
Coccyx = 4 fused
*33 vertebrae total
2
Q
What are the anatomic boarders of the facet joint on the vertebrae?
A
Superior articular process of one vertebra
Inferior articular process of the vertebra directly above
*injury to facet joint can compress spinal nerve that exits the respective foramina
3
Q
What ligament covers the sacral hiatus? What is the significant of this?
A
Sacrococcygeal Ligament
-it is punctured during caudal approach to the epidural space
4
Q
Order the 5 ligaments of the spinal column from posterior to anterior
A
-Supraspinous Ligament
-Interspinous Ligament
-Ligamentum Flavum
-Posterior Longitudinal Ligament
-Anterior Longitudinal Ligament
5
Q
What ligaments are penetrated during the midline and paramedian approach to the epidural space?
A
Midline Approach:
- supraspinous
- interspinous
- ligamentum flavum
Paramedian Approach
- ligamentum flavum
6
Q
List the structures/spaces between the skin and spinal cord as they would be encountered during a subarachnoid block
A
-Skin
-SubQ tissue
-Muscle
-Supraspinous ligament
-Interspinous ligament
-Ligamentum flavum
-Epidural space
-Dura mater
-Subdural space
-Arachnoid mater
-Subarachnoid space
-Pia mater
-Spinal cord
7
Q
What are the boundaries of the epidural space?
A
Cranial Border = Foramen Magnum
Caudal Border = Sacrococcygeal Ligament
Anterior Border = Posterior Longitudinal Ligament
Lateral Border = Vertebral Pedicles
Posterior Borders = Ligamentum Flavum and Vertebral Lamina
8
Q
What happens when you accidently inject local anesthetic into the subdural space during a SAB? How about during an epidural?
A
Subdural space = potential space between the dura and arachnoid mater
Inadvertent injection of LA into the space yields the following:
-epidural dose –> high spinal w/ delayed onset (15-20 min)
-spinal dose –> failed spinal
9
Q
What is Batson’s plexus? What is its significance?
A
Batson’s Plexus = epidural veins that drain venous blood from the spinal cord
-valveless veins pass through the anterior and lateral regions of the epidural space
-obesity and pregnancy increase intra-abdominal pressure causing engorgement – associated w/ increased risk of needle injury or cannulation during neuraxial techniques
10
Q
What is the plica mediana dorsalis? What is its significance?
A
Band of connective tissue between the ligamentum flavum and dura mater
-existence remains controversial
-if it does exist it could create a barrier that impacts the spread of medications within the epidural space
11
Q
What are the significant dermatomes levels and related cutaneous innervation?
A
-C6 = 1st digit (thumb)
-C7 = 2nd and 3rd digits
-C8 = 4th and 5th digits
-T4 = Nipple line
-T6 = Xiphoid process
-T10 = Umbilicus
-T12 = Pubic symphysis
-L4 = Anterior knee
12
Q
What is the site of action for spinal anesthesia and epidural anesthesia?
A
Spinal Anesthesia Site of Action:
- myelinated preganglionic fibers of the spinal NERVE ROOTS
- LA also inhibits neural transmission in the superficial layers of the spinal cord
Epidural Anesthesia Site of Action:
- diffuse through DURAL CUFF before they can block the nerve roots
- LA also leaks through the intervertebral foramen to enter the paravertebral area
13
Q
What factors significantly affect the spread of LA in the subarachnoid space?
A
Controllable Factors:
- baricity
- pt position during and after block placement
- dose
- site of injection
Non-Controllable Factors:
- volume of CSF
- density of CSF
14
Q
What factors do not significantly affect the spread of LA in the subarachnoid space?
A
-Barbotage
-Increased intra-abdominal pressure (coughing/labor)
-Speed of injection
-Orientation of bevel
-Addition of vasoconstrictor
-Weight
-Gender
15
Q
What is the primary determinant of spread for epidrual anesthesia?
A
Volume
16
Q
What is the order of blockade of spinal anesthesia? What are the blockade level differences?
A
-Autonomic fibers are blocked first
-Sensory fibers are blocked second
-Motor neurons are blocked last
*autonomic blockade = 2-6 dermatomes higher than sensory block
*sensory block = 2 dermatomes higher than motor block
17
Q
How is differential blockade different with epidural anesthesia than with spinal?
A
There is no autonomic differential blockade with epidural anesthesia
Sensory block = 2-4 dermatomes higher than motor block
18
Q
What are the characteristics of type A-alpha nerve fibers?
A
Heavy myelination
Function = skeletal muscle (motor) and proprioception
12-20 um diameter
Velocity = +++++
Block onset = 4th
19
Q
What are the characteristics of type A-beta nerve fibers?
A
Heavy myelination
Function = touch and pressure
5-12 um diameter
Velocity = ++++
Block onset = 4th
20
Q
What are the characteristics of type A-gamma nerve fibers?
A
Medium myelination
Function = skeletal muscle (Tone)
3-6 um diameter
Velocity = +++
Block onset = 3rd
21
Q
What are the characteristics of type A-delta nerve fibers? What order block onset?
A
Medium myelination
Function = fast pain, temp, touch
2-5 um diameter
Velocity = +++
Block onset = 3rd
22
Q
What are the characteristics of type B nerve fibers?
A
Light myelination
Function = preganglionic ANS fibers
3 um diameter
Velocity = ++
Block onset = 1st
23
Q
What are the characteristics of type C sympathetic nerve fibers? What is the block onset order?
A
No myelination
Function = postganglionic ANS fibers
0.3-1.3 um diameter
Velocity = +
Block onset = 2nd
24
Q
What are the characteristics of type C dorsal root nerve fibers? What is the block onset order?
A
No myelination
Function = slow pain, temp, touch
0.4-1.2 um diameter
Velocity = +
Block onset = 2nd
25
What is the order of block onset for the different nerve types?
First = B fibers
Second = C fibers (sympathetic and dorsal root)
Third = A-gamma and A-delta fibers
Fourth = A-alpha and A-beta fibers
26
What are the cardiovascular effects of neuraxial anesthesia?
Sympathectomy vasodilates the arterial and venous circulations --> Reduction in venous return, CO, and BP
-volume loading with ~15mL/kg and vasopressors will minimize hypotension
Bradycardia is caused by:
-blockade of preganglionic cardioaccelerator fibers at T1-T4 (promotes relative increase in parasympathetic tone)
-unloading of cardiac mechanoreceptors (Bezold-Jarish reflex)
-unloading of the stretch receptors in the SA node
27
What are the respiratory effects of neuraxial anesthesia?
Negligible effects on minute ventilation, tidal volume, RR, dead space, and arterial blood gas tensions in the HEALTHY patient
Accessory muscle function is reduced -- impairment of the intercostal muscles (inspiration/expiration) as well as abdominal muscles will decrease pulmonary reserve
-important for pt w/ severe COPD
Apnea is usually result of brainstem hypoperfusion (Decreased blood flow to ventilatory centers in the medulla) -- not a result of phrenic nerve paralysis or high concentrations of LA in the CSF
28
How does neuraxial anesthesia affect the neuroendocrine response to stress?
Diminishes the surgical stress response -- inhibits afferent traffic originating from the surgical site
-reduces circulating levels of catecholamines, renin, angiotensin, glucose, TSH, and growth hormone
29
How does neuraxial anesthesia affect GI function?
Inhibit the sympathetic tone --> increase parasympathetic tone to the gut --> relaxes the sphincters in the gut and increases peristalsis
30
How does neuraxial anesthesia affect renal and hepatic blood flow?
As long as systemic blood pressure is maintained -- hepatic and renal blood flow and function are unchanged
31
What is the risk of neuraxial anesthesia in the pt with coagulopathy? What lab values are considered contraindications to neuraxial technique?
Risk of spinal or epidural hematoma
Contraindicated in significant pathologic or therapeutic coagulopathic states:
-platelet count <100,000
-PT, aPTT, and/or bleeding time twice the normal values
32
What cardiac pathologies present a risk of hemodynamic collapse with neuraxial anesthesia?
Valve lesions with fixed stroke volume
-severe aortic stenosis
-severe mitral stenosis
-hypertrophic cardiomyopathy
33
What is the risk of a neuraxial technique in the patient with intracranial hypertension?
Increased chance of brain herniation with sudden change in CSF pressure
34
What is the relationship between neuraxial anesthesia and multiple sclerosis?
Intrathecal technique may exacerbate symptoms
-no good data to support this
-use lower dose and concentration of LA if doing a spinal for pt with MS
35
What is the specific gravity of CSF?
1.002 - 1.009
36
What is baricity? How does it influence your selection of local anesthetic?
Baricity = density of a local anesthetic solution relative to the CSF
-Isobaric solution = similar baricity to CSF (LA remains in place)
-Hyperbaric = higher density (LA sinks)
-Hypobaric = lower density (LA rises)
*general rule - solutions in dextrose are hyperbaric -- saline are isobaric -- water are hypobaric
*Procaine 10% in water = exception (it is hyperbaric)
37
How does a hyperbaric solution distribute in the sitting patient? How about the supine patient?
Hyperbaric solution will settle to the lowest point of the spinal canal
-Sitting = sink and anesthetize the sacral nerve roots (Saddle block)
-Supine = slide down the lumbar lordosis and pool in the sacrum and thoracic kyphosis
38
How does a hypobaric solution distribute in the sitting patient? How about the supine patient?
Hypobaric solution will settle to the highest point of spinal canal
-Sitting = rise towards brain (not a good idea)
-Supine = float toward the lower lumbar region
39
What are the two classifications of spinal needles? What are examples of each?
Cutting Tip -- Quincke and Pitkin
Non-Cutting Tip:
-Pencil point -- Pencan, Sprotte and Whitacre
-Rounded bevel -- Green
40
What are the pros and cons of each type of spinal needle?
Cutting Tip:
-Pros = requires less force
-Cons = higher risk of PDPH, less tactile feel, needle more easily deflected, more likely to injure cauda equina
Non-Cutting Tip:
-Pros = lower risk of PDPH, more tactile feel, needle less likely to deflect, less likely to injure the cauda equina
-Cons = requires more force
41
What are the three types of epidural needles? How are they different from each other?
Differ in the angle of the needle tip
-Crawford = 0 degrees
-Husted = 15 degrees
-Tuohy = 30 degrees (curvature plus blunt tip helps prevent dural puncture)
*needle angle increases in alphabetical order
42
How do you dose a caudal anesthetic in a child and adult for the following block heights:
-sacral
-sacral to low thoracic (~T10)
-sacral to mid thoracic
Sacral Block Height:
- pediatric dose = 0.5 mL/kg
- adult dose = 12-15 mL
Sacral to Low Thoracic (~T10):** common dose
- pediatric dose = 1 mL/kg
- adult dose = 20-30 mL
Sacral to Mid Thoracic:
- pediatric dose = 1.25 mL/kg
- adult dose = N/A
43
What are the absolute and relative contraindications to caudal anesthesia?
Absolute Contraindications:
-spina bifida
-meningomyelocele of sacrum
-meningitis
Relative Contraindications:
-pilonidal cyst
-abnormal superficial landmarks
-hydrocephalus
-intracranial tumor
-progressive degenerative neuropathy
44
What is the mechanism of action of neuraxial opioids?
Inhibit afferent pain transmission in the substantia gelatinosa (lamina 2) of the dorsal horn
Neurotransmission is reduced by:
-decreased cAMP
-decreased calcium conductance (presynaptic neuron)
-increased potassium conductance (postsynaptic neuron)
Epidural opioids also diffuse into the systemic circulation -- delivered to opioid receptors throughout the body
45
Do neuraxial opioids cause sympathectomy, skeletal muscle weakness, and/or changes in proprioception?
Neuraxial opioids DO NOT cause these
46
What are the doses for commonly used intrathecal opioids?
Sufentanil = 5-10 mcg
Fentanyl = 10-20 mcg
Meperidine = 10 mg
Morphine = 0.25 - 0.3 mg
47
What are the doses for commonly used epidural opioids?
Sufentanil = 25-50 mcg (10-20 mcg/hr)
Fentanyl = 50-100 mcg (25-100 mcg/hr)
Hydromorphone = 0.5-1 mg (0.1-0.2 mg/hr)
Meperidine = 25-50 mg (10-60 mg/hr)
Morphine = 2-5 mg (0.1-1 mg/hr)
48
Rank the opioids from most lipophilic to most hydrophilic
Lipophilic:
- Sufentanil
- Fentanyl
- Meperidine
- Hydromorphone
- Morphine
Hydrophilic
49
How does lipophilicity affect rostral spread of opioids in the subarachnoid space?
Hydrophilic drugs (morphine, meperidine) tend to remain in the subarachnoid space and travel towards the brain -- rostral spread
Lipophilic drugs (fentanyl, sufentanil) tend to diffuse out of the subarachnoid space and enter the systemic circulation
50
Compare and contrast PK/PD profiles of hydrophilic and lipophilic opioids used for spinal anesthesia
-Hydrophilic opioids stay in CSF longer than lipophilic
-Hydrophilic have extensive more rostral CSF spread with wide band of analgesia
-Lipophilic have minimal and less rostral CSF spread with narrow band of analgesia
-Hydrophilic site of action = rexed laminae 2&3
-Lipophilic site of action = rexed laminae 2&3 + systemic
-Hydrophilic have delayed (30-60 min) onset compared to lipophilic fast (5-10 min) onset
-Hydrophilic duration is longer (6-24 hrs) than lipophilic (2-4 hrs)
-Hydrophilic has less systemic absorption than lipophilic
-Hydrophilic has early and late respiratory depression -- lipophilic only has early
-Higher incidence of N/V and pruritus w/ hydrophilic
51
What are the four most important side effects of neuraxial opioids? Which is most common?
1. Pruritus (most common)
2. Respiratory depression
3. Urinary Retention
4. N/V
52
Which local anesthetic can reduce the efficacy of epidural opioids?
2-Chloroprocaine
53
Which neuraxial opioid can reactivate herpes simplex labialis?
Epidural Morphine
-best explained by the cephalad spread of morphine to the trigeminal nucleus
-presents 2-5 days after administration
54
What is the pathophysiology of postdural puncture headache? How does it present?
Puncture of the dura causing CSF to leak from subarachnoid space --> CSF pressure is lost, cerebral vessels dilate
Brainstem sags into the foramen magnum --> stretches the meninges and pulls on the tentorium
Classic presentation = fronto-occipital headache
-may be accompanied by nausea, emesis, photophobia, diplopia, and tinnitus
-upright position (gravity) makes headache worse
55
What are the risk factors for PDPH?
Patient Factors:
-higher risk = younger age, female, pregnancy
-lower risk = older age, male, non-pregnant
-no effect on risk = early ambulation
Practitioner Factors:
-higher risk = cutting tip needle, larger diameter needle, using air for LOR, needle perpendicular to long-axis of neuraxis
-lower risk = non-cutting tip, smaller diameter, using fluid for LOR, needle parallel to long-axis, continuous spinal catheter (if placed after wet tap)
-no effect on risk = continuous spinal catheter (if placed after spinal block)
56
How do you treat PDPH?
-Bed rest
-Hydration
-NSAIDs
-Caffeine (cerebral vasoconstriction)
-Epidural blood patch (definitive treatment)
*opioids are not used
57
How do you perform an epidural blood patch? What is the success rate?
Using sterile technique, 10-20 mL of venous blood is withdrawn from the pt and then reintroduced into the epidural space -- when pt feels pressure in legs, buttock, or back the injection is complete
-compresses the epidural and subarachnoid spaces --> increases CSF pressure
-acts as a plug to prevent further leaks
90% success rate -- if headache doesn't improve after 2 blood patches, consider other etiologies
58
What are the most common side effects of an epidural blood patch?
Backache
Radicular Pain
59
What is the primary risk of neuraxial anesthesia in the anticoagulated patient? How does this complication present?
Epidural Hematoma -- can cause paralysis
Presenting Symptoms:
-lower extremity weakness
-numbness
-low back pain
-bowel and bladder dysfunction
*surgical decompression within 8 hours offers best chance of recovery
60
What are the neuraxial considerations for COX-1 Inhibitors (NSAIDs and ASA)?
- Clinical assessment of coagulation status appears normal
- No other blood thinners in use
** Otherwise, no added risk or limitations
61
What are the neuraxial considerations for Glycoprotein IIb/IIIa antagonists (Tirofiban, Eptifibatide, Abciximab)?
Avoid until platelet function has recovered
Before block placement:
-hold Tirofiban and Eptifibatide for 4-8 hours
-hold Abciximab for 24-48 hours
Contraindicated within 4 weeks of surgery (do not restart)
62
What are the neuraxial considerations for Thienopyridine Derivatives (Clopidogrel, Prasugrel, Ticlopidine)?
Before block placement:
-Clopidogrel: hold 5-7 days
-Prasugrel: hold 7-10 days
-Ticlopidine: hold 10 days
May restart 24 hrs postop
63
What are the neuraxial considerations for unfractionated heparin?
Criteria to consider for neuraxial block:
- clinical assessment of coagulation status appears normal and no other blood thinners in use
- obtain a platelet count before neuraxial block or catheter removal if on IV or SQ heparin >4 days
Before block placement:
- hold 4-6 hours: low dose (5,000 U up to TID)
- hold 12 hours: higher dose (<20,000 U daily)
- hold 24 hrs: therapeutic UFH high dose (>20,000 U daily in pregnant pts)
After block placement = restart heparin after 1 hr
Before neuraxial catheter removal:
- hold 4-6 hr after last SQ dose or IV infusion discontinued
After catheter removal = restart heparin after 1 hr
64
What are the neuraxial considerations for Anti-Vitamin K drugs (Warfarin)?
Before block/catheter placement:
-hold warfarin 5 days
-verify normal INR
Neuraxial catheter removal:
-wait until INR <1.5
65
What are the neuraxial considerations for Oral Anti-Factor Xa agents (Apixaban, Betrixaban, Edoxiban, Rivaroxaban)?
Before block/catheter placement:
-discontinue at least 72 hours prior
-consider checking drug level or anti-factor Xa activity if less than 72 hours
Neuraxial catheter removal:
-6 hours before 1st postop dose
-if accidental dose given with catheter in situ -- hold subsequent dose before removal for: Edoxaban (20-28hrs), Rivaroxaban (22-26hr), Apixaban (26-30hrs), Betrixaban (72hrs)
66
What are the neuraxial considerations for Thrombolytic agents (TPA, Streptokinase, Alteplase, Urokinase)?
Absolute contraindication to neuraxial anesthesia
67
What are the neuraxial considerations for herbal therapies (garlic, ginkgo, ginseng)?
Proceed with neuraxial anesthesia if patient is not on other blood thinning drugs
68
What are the neuraxial considerations for low molecular weight heparin (Enoxaparin, Dalteparin, Tinzaparin)?
Criteria to consider for neuraxial block:
-clinical assessment of coagulation status appears normal and no other blood thinners in use
-obtain a platelet count before block or catheter removal if on LMWH >4 days
Before block/catheter placement:
-delay at least 12 hrs after prophylactic dose
-delay at least 24 hrs after therapeutic dose and consider checking anti-factor Xa activity in elderly or if renal insufficiency
After block/catheter placement:
-delay first dose at least 12 hours after block
-if single daily dosing, give 2nd dose no sooner than 24 hours after 1st dose
Neuraxial catheter removal:
-remove before initiating LMWH if possible delay 1st dose at least 4 hours after removal
-otherwise remove at least 12 hours after last dose; hold for 4 hours after removal
Blood in needle or catheter = delay initiating LMWH for 24 hours
69
What spinal level does the conus medullaris and dural sac end in the adult and infant?
Conus Medullaris (end of spinal cord) ends at:
-Adult: L1-L2
-Infant: L3
Dural Sac (subarachnoid space) ends at:
-Adult: S2
-Infant: S3
70
What is the cause of cauda equina syndrome? What factors increase the risk?
Cause = neurotoxicity from exposure to high concentrations of LA
Factors that increase risk:
-5% lidocaine and spinal microcatheters
*microcatheters focus LA on a small area of cord, exposing this region to high concentration of LA
71
How does cauda equina syndrome present? What is the treatment?
S/Sx
- bowel and bladder dysfunction
- sensory deficits
- weakness
- paralysis
Treatment = Supportive
72
What is the cause of transient neurologic symptoms? What factors increase the risk?
Cause = pt positioning, stretching of the sciatic nerve, myofasical strain, and muscle spasm
-highly unlikely that neurotoxicity causes TNS
Factors that increase risk:
-lidocaine
-lithotomy position
-ambulatory surgery
-knee arthroscopy
73
How do transient neurologic symptoms present? What is the treatment?
S/Sx:
- severe back and butt pain that radiates to both legs
- generally develops within 6-36 hours and persists for 1-7 days
Treatment:
- NSAIDs
- Opioids
- Trigger point injections
74
What is the most common organism responsible for post-spinal bacterial meningitis?
Streptococcus viridans
-commonly found in the mouth (reason it is so critical to wear a mask during neuraxial block)
75
What is the best way to prepare the skin prior to neuraxial anesthesia?
-Chlorhexidine
-Isopropyl Alcohol
-Iodine
*according to Miller - best method = combo of chlorhexidine + isopropyl alcohol
*chlorhexidine = neurotoxic so allow it to dry completely
76
What are the causes and management of a no block "failed spinal"?
Causes:
-LA not injected into CSF
-LA was defective (hyperbaric bupivacaine = most common)
-syringe swap (ie another drug was injected)
Management (If block not achieved in 15-20 min):
-convert to GA
-repeat block (caution advised -- some blocks may set up slowly and a 2nd dose may cause total spinal)
77
What are the causes and management of a unilateral block "failed spinal"?
Causes:
-poor patient positioning (most common)
-anatomic variant prevented LA spread
Management:
-position the unblocked side down (use gravity to distribute)
-can proceed with caution if the blocked side is the same side as surgery
78
What are the causes and management of a patchy block "failed spinal"?
Causes:
-insufficient dose (most common) -- too low a dose or not enough of the dose reaching the anatomic target
Management:
-transition to another technique (ie. supplemental IV sedation or GA)
79
What are the causes and management of an inadequate duration "failed spinal"?
Causes:
-insufficient dose (most common)
-wrong drug selected
Management:
-transition to another technique (ie. supplemental IV sedation or GA)
80
What are the causes and management of an inadequate block height or density "failed spinal"?
Causes:
-insufficient dose (ie. leak at syringe/needle connection)
-injection site selected is too low in the subarachnoid space
Management:
-place pt in Trendelenburg to encourage cephalad spread (only beneficial until block sets) -- far more effective w/ hyperbaric LA
81
What are the five main components of the brachial plexus?
Roots = 5 -- C5, C6, C7, C8, T1
Trunks = 3 -- Superior, Middle, Inferior
Divisions = 6 -- 3 posterior and 3 anterior
Cords = 3 -- Lateral, Posterior, Medial
Branches = 5 -- Musculocutaneous, Median, Ulnar, Axillary, Radial
82
How many trunks are in the brachial plexus? Which nerve roots give rise to each trunk?
C5-6 --> Superior Trunk
C7 --> Middle Trunk
C8-T1 --> Inferior Trunk
83
How many cords are in the brachial plexus? Which nerve roots, and divisions give rise to each cord?
C5-C7 --> Anterior divisions of superior and middle trunks --> Lateral cord
C8-T1 --> Anterior division of inferior trunk --> Medial cord
C5-T1 --> All three posterior divisions --> Posterior cord
84
How many terminal branches are in the brachial plexus? Which roots and cord gives rise to each branch?
-Musculocutaneous = C5-C7 -- Lateral Cord
-Axillary = C5-C6 -- Posterior Cord
-Median = C5-T1 -- Median and Lateral Cords
-Radial = C5-T1 -- Posterior Cord
-Ulnar = C8-T1 -- Medial Cord
85
Where do the roots turn into trunks in the brachial plexus?
just beyond the lateral border of the scalene muscles
86
Where do the trunks turn into divisions in the brachial plexus?
underneath the clavicle and over the 1st rib
87
Where do divisions turn into cords in the brachial plexus?
when the brachial plexus goes under the pectoralis minor muscle
88
Where do cords turn into terminal branches in the brachial plexus?
in the axilla
89
Describe the sensory innervation of the upper extremity
- ventral portion is supplied by median, ulnar, and musculocutaneous nerves (lateral/medial cords)
- dorsal portion is supplied by the radial and axillary nerves (posterior cord)
*hand is the exception
90
What is the sensory region of each branch of the brachial plexus?
**Axillary:** lateral upper arm at shoulder
**Intercostobrachial & Medial Brachial Cutaneous:** medial upper arm to elbow
**Medial Antebrachial Cutaneous:** anterior upper arm and anterior/medial forearm to the wrist
**Musculocutaneous (lateral antebrachial cutaneous):** lateral forearm to the wrist
**Radial:** lateral upper arm, posterior arm below shoulder, posterior forearm, dorsum of hand lateral to axial line of 4th digit, radial side of thumb
**Median:** palmer side of 1st/2nd/3rd digits + tips on dorsal side, radial side of 4th digit + tip on dorsal side
**Ulnar:** hypothenar eminence, ulnar side of 4th digit, entire 5th digit
91
In addition to a brachial plexus block, which nerve must also be anesthetized to foster the tolerance of an upper extremity tourniquet?
Intercostobrachial blockade
-arises from T2
-a field block is required to block this nerve (begin at deltoid prominence and move inferiorly
-5mL of LA is sufficient
92
What types of surgical procedures are well suited for an interscalene block? Which are not?
Indicated for procedures involving the shoulder, upper arm, and clavicle
Not the best option for procedures below the elbow -- interscalene frequently spares roots C8-T1
93
Which approach to the brachial plexus is most likely to cause phrenic nerve paralysis? What are the clinical implications of this?
Phrenic nerve is nearly always blocked with interscalene block
-results in ipsilateral hemiparesis of diaphragm
-healthy pts --> rarely results in respiratory compromise
-pts with respiratory disease --> may result in severe dyspnea, hypercapnia, and hypoxemia
94
Which approach to the brachial plexus is most likely to cause Horner's syndrome? What are the clinical implications of this?
Interscalene -- stellate ganglion is located at C7
-ptosis, miosis, and anhidrosis
-indicates a successful block
95
What is the relationship between shoulder arthroscopy, interscalene blockade, and hypotensive bradycardic episodes?
Bezold-Jarisch reflex is the proposed mechanism for hypotensive bradycardic episodes during shoulder arthroscopy w/ interscalene blockade
-pt is typically in sitting or semi upright position
-S/Sx = bradycardia, hypotension, and syncope
*theory is that venous pooling in lower extremities reduces venous return -- combined effects of an unloaded ventricle, SNS stimulation, and epinephrine uptake (from block) results in a profoundly underfilled ventricle that slows its rate to increase diastolic filling time
96
What types of surgical procedures are indicated for a supraclavicular block? Which are not?
Indicated for procedures of the upper arm, elbow, wrist, and hand
-targets trunks/divisions of brachial plexus
Not ideal for shoulder procedures
97
What is the greatest risk of a supraclavicular block? Why?
Pneumothorax -- pleura is immediately inferior to the first rib
-tilting transducer slightly caudal will place 1st rib between the brachial plexus and pleura (reduces risk)
-risk is higher in taller patients
-consider pneumothorax if pt complains of cough, chest pain, or dyspnea after the block
-dyspnea tends to be delayed sign
98
What section of the brachial plexus does an Infraclavicular block target? What types of surgical procedures are well suited for it? Which are not?
Targets the cords of the brachial plexus below the clavicle
Indications: surgical procedures of the upper arm, elbow, wrist, and hand
-good alternative to supraclavicular block in patients with respiratory insufficiency (lower risk of phrenic nerve blockade) and axillary block in pts with limited upper extremity mobility
Not well suited for shoulder surgery
99
Where are the terminal branches of the brachial plexus located relative to the axillary artery?
Musculocutaneous = Anterior and Lateral
Median = Anterior and Medial
Radial = Posterior and Lateral
Ulnar = Posterior and Medial
100
Which nerve is most likely to be missed during an axillary block? Which terminal branch is not included in an axillary block?
Musculocutaneous nerve is most likely to be missed
-exits proximal to this area and travels in the fascial plane between the biceps and coracobrachialis muscles
Axillary nerve is NOT included in an axillary block
101
What types of surgical procedures are well suited for an axillary block? Which are not?
Provides anesthesia to the upper extremity distal to the elbow (forearm and hand)
Doesn't cover:
-skin of medial upper arm
-skin over the deltoid
102
How do you block the radial nerve in the forearm?
Local anesthetic is injected between the biceps tendon and brachioradialis
Volume = 3-5 mL
103
How do you block the ulnar nerve at the elbow?
Elbow is flexed 90 degrees and a local anesthetic is injected between the olecranon and medial epicondyle of the humerus
Volume = 3-5 mL
*using too high volume can compress the ulnar nerve, resulting in ischemic injury
104
How do you block the median nerve at the forearm?
Local anesthetic is injected medially to the brachial artery in the AC fossa
Brachial artery is located medially to the biceps tendon
Volume = 3-5 mL
*avoid in patient with carpal tunnel syndrome
105
How do you block the radial nerve at the wrist?
Subcutaneous injection (field block) of 10 mL proximal to the radial styloid
Field block is used because there are several branches of the radial nerve at this point in the wrist
106
How do you block the ulnar nerve at the wrist?
Anatomic Landmarks: Ulnar styloid, Ulnar pulse, Flexor carpi ulnaris tendon
Inject 3-5 mL medial to and below the flexor carpi ulnaris tendon -- confirm negative aspiration due to proximity to the ulnar artery
107
How do you block the median nerve at the wrist?
Inject 5 mL between the flexor carpi radialis tendon and the flexor palmaris longus tendon
108
How do you perform a Bier block?
-Place a double cuff tourniquet on the patient, but don't inflate it
-Place 22g PIV in a distal peripheral vein on operative extremity
-Elevate extremity for 1-2 min to allow passive exsanguination
1) Wrap Esmarch bandage around the extremity to further exsanguinate it
2) Inflate the DISTAL cuff
3) Inflate the PROXIMAL cuff (should be ~250mmHg)
4) Deflate the DISTAL cuff
5) Remove the Esmarch bandage
6) Inject LA -- use a large volume of dilute LA (50mL of 0.5% lidocaine)
*do not use bupivacaine or a solution that contains epi
109
How do you change cuffs during the procedure when a Bier block is in use?
1) Proximal cuff is currently inflated
2) Inflate distal cuff (tissue under this cuff is already anesthetized)
3) Deflate proximal cuff
110
When can you deflate the tourniquet after a Bier block?
Must remain inflated for a minimum of 20 minutes following LA injection -- allows enough time for the LA to absorb into the tissue
*if deflated too soon, LA washes out into the systemic circulation, where it can produce LAST symptoms
111
What are the 6 terminal branches of the lumbar plexus?
Lumbar plexus arises from the anterior rami of L1-L4, with an occasional contribution from T12
-Iliohypogastric
-Ilioinguinal
-Genitofemoral
-Lateral femoral cutaneous
-Obturator
-Femoral
"I Invariably Get Lazy On Fridays"
112
Which nerve roots give rise to each nerve of the lumbar plexus?
Iliohypogastric - L1
Ilioinguinal - L1
Genitofemoral - L1 + L2
Lateral Femoral Cutaneous - L2 + L3
Obturator - L2 + L3 + L4
Femoral - L2 + L3 + L4
113
Describe the sensory innervation to the lower extremity
114
Describe the anatomy of the psoas compartment
Lumbar plexus is contained within a sheath inside the psoas compartment
At this point, the plexus is:
-lateral to the vertebral column
-anterior to the quadratus lumborum muscle
-posterior to the psoas muscle
115
What nerves are anesthetized by the psoas compartment block? What is another name for the block?
Targets:
-lateral femoral cutaneous n.
-femoral n.
-obturator n.
Also called lumbar plexus block
*useful when neuraxial anesthesia is contraindicated and/or anesthesia to one lower extremity is preferred
116
Discuss the anatomy of the femoral triangle
-Arises from the posterior divisions of L2-L4
-Nerve roots exit spinal column and give rise to the femoral nerve within the psoas major
-Femoral nerve stays in the groove between the psoas major and iliac muscles before entering the femoral triangle
-Inside the triangle, the femoral nerve runs --> deep to inguinal ligament, anterior to iliopsoas muscle, inferior to the fascia lata and fascia iliaca
Triangle is shaped like the "SAIL" of a ship (Borders of the triangle)
-S = sartorius muscle
-A = adductor longus muscle
-IL = inguinal ligament
Use "VAN" for the structures inside the triangle (Medial --> Lateral)
-V = vein
-A = artery
-N = nerve
117
Discuss the anatomy and innervation of the anterior and posterior branches of the femoral nerve
Divides into anterior and posterior branches -- occurs just before or just after the nerve passes under the inguinal ligament
- **anterior branch** innervates the ventral surface of the thigh and the sartorius muscle
- **posterior branch** innervates quadriceps muscles, knee joint, and its medial ligament
- posterior branch gives rise to the saphenous nerve
118
Describe the innervation of the saphenous nerve. What are the implications of this in the context of surgery on the lower extremity?
Saphenous nerve is the terminal branch of the posterior division of the femoral nerve
-provides sensory innervation from the medial aspect of the knee to the medial malleolus
-no motor component
Block is useful when combined with a popliteal or ankle block (these don't capture the saphenous distribution)
119
Describe the anatomy of the sciatic nerve
Sciatic nerve arises from L4-5 and S1-3
-sciatic nerve is actually two nerves contained within a sheath (tibial and peroneal)
-exits the pelvis inferior to the piriformis muscle via the great sacrosciatic foramen
-as it continues causally, it passes between the major trochanter and the tuberosity of the ischium into the lower third of the thigh -- where the sciatic nerve divides into tibial and common peroneal nerves
120
Describe the relevant anatomy for a popliteal block
Popliteal block targets the sciatic nerve in the proximal popliteal fossa:
-at this location, the sciatic nerve is posterior and lateral to the popliteal artery and vein, and is bordered medially by the semitendinosus and semimembranosus muscles and lateral by the biceps femoris muscle
-a "triangle" is formed in the posterior knee with the base being the popliteal crease at the knee, and the apex formed by the convergence of the biceps femoris and semitendinosus muscles
121
What are the 5 terminal nerves at the level of the ankle? What is the origin for each nerve?
-Saphenous (origin = femoral)
-Deep Peroneal (origin = sciatic)
-Superficial Peroneal (origin = sciatic)
-Sural (origin = sciatic)
-Posterior Tibial (origin = sciatic)
*3 sensory nerves begin with an "S"
*2 mixed sensory and motor nerves don't begin with an "S"
122
Describe the sensory innervation of the foot and ankle
123
Where is the sural nerve blocked?
Posterior to the lateral malleolus
124
Where is the deep peroneal nerve blocked?
Between the tendons of the anterior tibial and extensor digitorum longus muscles
125
Where is the superficial peroneal nerve blocked?
Anterior to the lateral malleolus
126
Where is the saphenous nerve blocked?
Anterior to the medial malleolus
127
At the level of the ankle, which nerve is not immediately adjacent to a vascular structure?
Superficial peroneal nerve
-all other nerves are very close to an artery and/or vein
128
What is the difference between a PECS1 and PECS2 block?
PECS 1: injection site = fascial plane between the pec major and pec minor
PECS 2: injection site = fascial plane between the pec major and pec minor (injection 1) and in the fascial plane between the pec minor and serratus anterior (injection 2)
129
Describe the anatomy and distribution of the intercostal nerves
-Originate from the ventral rami of the thoracic spinal nerves (T1-T11)
-Each intercostal nerve enters the intercostal space between the posterior intercostal membrane and parietal pleura
-Once inside the intercostal space, each nerve travels beneath the rib alongside the corresponding intercostal artery and vein
-Nerve's proximity to these vascular structures has implications for LA toxicity
130
Describe the distribution of anesthesia with a paravertebral block
Provides coverage for only one dermatome level
Procedure must be performed at each level where anesthesia is desired
131
What are the boundaries of the paravertebral space?
Anterior --> Parietal Pleura
Medial --> Vertebral body and intravertebral foramen
Posterior --> Transverse process and superior costotransverse ligament
132
What are the indications for paravertebral blockade?
Surgical Procedures:
-Thoracic, Breast, Cholecystectomy, Herniorraphy, Appendectomy
Pain Management:
-Rib fractures, Flail chest, Blunt abdominal trauma, Osteoporotic vertebral fractures, Herpes zoster where coverage of more than one dermatome is needed
133
What is an errector spinae block?
A fascial plane technique that targets the dorsal and ventral rami of the thoracolumbar nerves at the level of injection
Injecting LA deep to the erector spinae muscle group and superficial to the transverse process causes significant craniocaudal spread
134
What is the triangle of Petit? What are its borders?
The inferior lumbar triangle
-provides a key anatomic reference point for performing a TAP block with a landmark technique
-you can directly localize the internal oblique muscle at this location
-you can find the internal oblique just beyond the peak of the iliac crest
Posterior Border = Latissimus dorsi
Anterior Border = External oblique
Inferior Border = Iliac crest
Inside of the triangle (floor) = Internal oblique
Transverse Abdominis is deep to the internal oblique
135
What is the goal of a TAP block?
To place LA in the fascial plane between the internal oblique and transverse abdominis muscles
Thoracolumbar nerves arising from T6-L1 innervate the internal oblique and transverse abdominis muscles
Three approaches (subcostal, lateral, and posterior)
-subcostal approach: procedures above the umbilicus
-lateral and posterior approach: procedures below the unbilicus
136
What are the indications for a rectus sheath block?
Used in procedures that require a midline abdominal incision
Indications:
-umbilical hernia repair in pediatric population
-c-section when midline incision is required
-postpartum laparoscopic tubal ligation
137
Describe the thoracolumbar fascia
Highly complex network of connective tissue involved in the lumbar paravertebral area and the anterolateral abdominal wall
Consists of 3 layers: Anterior, Middle, and Posterior
Quadratus Lumborum Muscle resides between the anterior to the middle layers
138
Where is local anesthetic injected for the QL 1, 2, & 3 blocks?
Thoracolumbar fascia - target area for depositing local anesthetic
QL 1: LA injected lateral to the quadratus lumborum muscle (QLM)
QL 2: LA injected posterior to the QLM
QL 3: LA injected anterior to the QLM
139
What is the motor function for the terminal nerves of the brachial plexus?
**Axillary:** Shoulder ABduction (deltoid contraction)
**Musculocutaneous:** Elbow Flexion and Forearm Supination
**Radial:** Elbow Extension, Wrist Extension, Finger Extension, and Thumb ABduction
**Median:** Forearm Pronation, Finger Flexion (digits 1-3), Thumb Opposition
**Ulnar:** Wrist Flexion, Ulnar Deviation, 5th Digit Opposition, Finger Flexion (digits 4/5), Thumb ADDuction
140
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