Regional Flashcards
1
Q
What are the 5 divisions of the spinal column, and how many vertebrae are present in each?
A
The vertebral column is made up of 33 vertebrae. Cervical- 7, Thoracic -12, Lumbar-5, sacrum- 5 fused, coccyx- 4 fused
2
Q
What are the anatomic borders of the facet joint?
A
The facet joint is formed by the superior articular process of one vertebra and the inferior articular process of the vertebra directly above.
Injury to the facet joint can compress the spinal nerve that exits the respective intervertebral foramina, causing pain and muscle spasm along the associated dermatome
3
Q
What ligament covers the sacral hiatus? what is the significance of this?
A
The sacral hiatus is covered by the sacrococcygeal ligament.
The ligament is punctured during the 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 approach to the epidural space? how about the paramedian approach?
A
midline approach: the needle will pass through 3 ligaments
*supraspinous ligament
* interspinous ligament
* ligamentum flavum
Paramedian approach: the needle will pass through 1 ligament
* ligamentum flavum
The paramedian approach bypasses the other ligaments. With either approach the needle should NEVER pass through the anterior or posterior longitudinal ligaments.
6
Q
List all the structures and spaces between the skin and the spinal cord as they would be encountered during a subarachnoid block.
A
Skin
subcutaneous tissue
muscle
supraspinous ligament
interspinous ligament
ligament flavum
epidural space
dura mater
subdural space
arachnoid mater
subarachnoid space
pia mater
spinal cord
7
Q
what happens when you accidently inject local anesthetic into the the subdural space during a SAB? How about during an epidural?
A
The subdural space is a potential space between the dura mater and the arachnoid mater.
Inadvertent injection of local anesthetic into the subdural space yields the following outcomes:
*Epidural dose-> high spinal with delayed onset (15-20 min)
*spinal dose-> failed spinal
8
Q
What is Batson’s plexus? and what is its significance?
A
The epidural veins (Batson’s plexus) drain venous blood from the spinal cord. These valveless veins pass through the anterior and lateral regions of the epidural space.
Obesity and pregnancy increase intra-abdominal pressure, causing engorgement of the plexus. This is associated with an increased risk of needle injury or cannulation during neuraxial techniques.
9
Q
What is plica mediana dorsalis, and what is its significance?
A
While its existence remains controversial, many speculate that a band of connective tissue courses between the ligamentum flavum and the dura mater. If it does exist, it could conceivably create a barrier that would impact the spread of medications within the epidural space. The plica mediana dorsalis has long been considered the culprit for difficult epidural catheter insertion as well as unilateral epidural blocks.
10
Q
What is a dermatome, and which ones are important as you assess neuraxial anesthetic?
A
the dermatome relates to an area of skin that is innervated by a spinal nerve- it is not necessarily the area of skin that is the same plane as the spinal nerve.
C6- 1st digit (thumb)
C7- 2nd and 3rd digits
C8- 4th and 5th digits
T4- Nipple line
T6- xyphoid process
T10- umbilicus
T12- Pubic symphysis
L4- anterior knee
11
Q
Compare and contrast the site of action for spinal vs epidural anesthesia.
A
site of action: Spinal anesthesia
* The primary site of local anesthetic action is on the myelinated preganglionic fibers of the spinal nerve roots.
* Local anesthetics also inhibit neural transmission in the superficial layers of the spinal cord
Site of action : Epidural anesthesia
* Local anesthetics in the epidural space must first diffuse through the dural cuff before they can block the nerve roots
* local anesthetics also leak through the intervertebral foramen to enter the paravertebral area. Here, local anesthetics cause multiple paravertebral blocks
12
Q
What factors do and do NOT contribute to the spread of local anesthetics in the subarachnoid space?
A
Significantly affect spread:
Controllable factors:
* Baricity of local anesthetic
* Patient position during and after block placement
* dose
* site of injection
Non-controllable factors:
* VOlume of CSF
* Density of CSF
Does NOT significantly affect spread
* Barbotage
* Increase intra-abdominal pressure (coughing, labor)
* speed of injection
* orientation of bevel
*addition of vasoconstrictor
* weight
*gender
13
Q
What is the primary determinant of spread for epidural anesthesia?
A
Volume
14
Q
Discuss the differential blockade of spinal anesthesia.
A
Different types of nerves have different sensitivities to the local anesthetic blockade.
* Autonomic fivers are blocked first
* Sensory fibers are blocked second
* Motor neurons are blocked last
Why is this important?
* Autonomic blockade is 2-6 dermatomes higher than sensory block
* sensory block is 2 dermatomes higher than motor block
15
Q
How is differential blockade different with epidural anesthesia?
A
There is no autonomic differential blockade with epidural anesthesia
Sensory block is 2-4 dermatomes higher than motor block
16
Q
Compare and contrast nerve fibers in terms of subtype, myelination, function, size, conduction velocity, and block onset.
A
17
Q
Discuss the cardiovascular effects of neuraxial anesthesia.
A
Sympathectomy vasodilates the arterial and venous circulations, although it predominantly affects the venous capacitance vessels. Consequently, there is a reduction in venous return, cardiac output, and blood pressure. Volume loading with around 15mL/kg and vasopressors will minimize HoTN.
bradycardia is caused by:
* blockade of the preganglionic cardioaccelerator fibers at T1-T4. This promotes a relative increase of parasympathetic tone.
* unloading of cardiac mechanoreceptors (bezold- jarisch reflex)
*unloading of the stretch receptors in the SA node.
18
Q
Discuss the respiratory effects of neuraxial anesthesia.
A
In healthy patients, neuraxial anesthesia has negligible effects on minute ventilation, tidal volume, respiratory rate, dead space, and arterial blood gas tensions.
Accessory muscle function is reduced. Impariment of the intercostal muscles (inspiration and expiration) as well as the abdominal muscles (ability to cough and clear secretions) will decrease pulmonary reserve. This is particularly important for the patient with severe COPD.
Apnea is usually the result of brainstem hypoperfusion (decreased blood flow to the ventilatory centers in the medulla).
Apnea is usually NOT the result of phrenic nerve paralysis or high concentrations of local anesthetic in the CSF.
19
Q
How does neuraxial anesthesia affect the neuroendocrine response to stress?
A
By inhibiting afferent traffic originating from the surgical site, neuraxial anesthesia diminishes the surgical stress response. This reduces circulating levels of catecholamines, renin, angiotensin, glucose, thyroid-stimulating hormone, and growth hormone
20
Q
How does neuraxial affect GI function?
A
The gut receives parasympathetic innervation from the vagus nerve (CN 10) and sympathetic innervation from the sympathetic chain (T5-L2)
Neuraxial local anesthetics inhibit the sympathetic tone, which increases the parasympathetic tone to the gut. This relaxes the sphincters in the gut and increases peristalsis.
21
Q
How does neuraxial anesthesia affect renal and hepatic blood flow?
A
So long as systemic blood pressure is maintained, hepatic and renal blood flow and function are unchanged
22
Q
What is the risk of neuraxial anesthesia in the patient with coagulopathy? What lab values are considered contraindications to a neuraxial technique?
A
Risk of spinal or epidural hematoma.
Neuraxial blocks are contraindicated in significant pathologic or therapeutic coagulopathic states.
* platelet count <100,00mm
* PT, aPTT, and/or bleeding time twice the normal value
23
Q
what cardiac pathologies present a risk of hemodynamic collapse with neuraxial anesthesia?
A
Valve lesions with fixed stroke volume.
* severe aortic stenosis
* severe mitral stenosis
* Hypertrophic cardiomyopathy
24
Q
what is the risk of a neuraxial technique in the patient with intracranial HTN?
A
There is an increased chance of brain herniation with sudden change in CSF pressure
25
What is the relationship between neuraxial anesthesia and multiple sclerosis?
Classic teaching suggests that, while epidural anesthesia is safe, an intrathecal technique may exacerbate symptoms. In practice, there is no good data to support this.
If spinal anesthetic would benefit the patient with MS, you should inform the patient about a small risk of symptom exacerbation.
If you move forward with a spina, understand that demyelinated fibers may be more susceptible to local anesthetic-induced neurotoxicity. It's best to use a lower dose and concentration of LA.
26
What is baricity , and how does it influence your selection of local anesthetic?
Baricity describes the density of a local anesthetic solution relative to the CSF.
* An isobaric solution describes a local anesthetic solution whose baricity is similar to CSF.
* A higher density solution is hyperbaric
* A lesser density solution is hypobaric
A hyperbaric solution will sink, a hypobaric will rise, and an isobaric solution will remain in place.
As a general rule, solutions in dextrose are hyperbaric, in saline are isobaric, and in water are hypobaric. Procaine 10% in water is an exception (it's hyperbaric; presumably because there are so many molecules in a 10% solution).
27
how does a hyperbaric solution distribute in the sitting patient? how about the supine patient?
A hyperbaric solution will settle to the lowest point of the spinal canal.
* If we keep the patient sitting, a hyperbaric solution will sink and anesthetize the sacral nerve roots, this is a saddle block.
* If we lay the patient supine after the block, a hyperbaric solution will slide down the lumbar lordosis and eventually pool in the sacrum and the thoracic kyphosis.
Hypobaric solution will rise to brain while laying, or lower lumbar region while laying
28
What are the 2 classifications of spinal needles?
Cutting and non-cutting (pencil point & rounded bevel)
Cutting- quincke, pitkin
Pencil point- sprotte and whitacre
Rounded bevel- green
29
What are the three different types of epidural needles? How are they different from each other?
Epidural needles differ in the angle of the needle tip. Notice that the needle angle increases in alphabetical order.
* Crawford= 0 degrees
* Hustead= 15 degrees
* Tuohy= 30 degrees
The tuoy needle has the most pronounced curvature. this curvature plus its blunt tip helps prevent dural puncture
30
How do you dose a caudal anesthetic in a child? An Adult?
Sacral - pediatric -0.5mL/kg / 12-15mL for an adult
Sacral to low thoracic- 1mL/kg/ Adult 20-39mL
Sacral to mid thoracic- 1.25 mL/kg / adult-N/A
31
What are the absolute and relative contraindications to caudal anesthesia?
Absolute:
* spina bifida
* Meningomyelocele of the sacrum
* Meningitis
Relative
* Pilonidal cyst
* Abnormal superficial landmarks
* Hydrocephalus
* Intracranial tumor
* Progressive degenerative neuropathy
32
Discuss the mechanism of action of the neuraxial opioids.
Neuraxial opioids inhibit afferent pain transmission in the substantia gelatinosa (lamina 2) of the dorsal horn.
Neurotransmission is reduced by:
* Decreased cAMP
* Decreased Ca2+ conductance (presynaptic neuron)
* Increased K+ conductance (postsynaptic neuron)
Epidural opioids also diffuse into the systemic circulation, where the blood delivers them to opioid receptors throughout the body
33
DO neuraxial opioids cause sympathectomy, skeletal muscle weakness, and/or changes in proprioception?
Neuraxial opioids do NOT cause:
* sympathectomy
* Skeletal muscle weakness
* Changes in proprioception
34
Discuss the commonly used intrathecal and epidural opioids dosing
35
Rank the opioids from most lipophilic to most hydrophilic. How does lipophilicity affect rostral spread in the subarachnoid space?
Hydrophilic drugs tend to remain in the subarachnoid space and travel upwards to the brain (rostral spread)
Lipophilic drugs tend to diffuse out of the subarachnoid space and enter the systemic circulation.
Hydrophilic: Morphine, hydromorphone, meperidine
Lipophilic: Fentanyl, Sufentanil
36
Compare and contrast PK/PD profiles of hydrophilic and lipophilic opioids used for spinal anesthesia.
37
What are the 4 most important side effects of neuraxial opioids? What is the most common?
1. Pruritis (most common side effect)
2. respiratory depression (hydrophilic drugs are higher risk d/t greater rostral spread)
3. Urinary retention
4. N/V
38
What local anesthetic can reduce the efficacy of epidural opioids?
2-Chloroprocaine reduces the efficacy or epidural opioids
39
What neuraxial opioid can reactivate herpes simplex labialis?
Epidural morphine may reactivate herpes simplex labialis type 1. This is best explained by the cephalad spread of the morphine to the trigeminal nucleus. It usually presents 2-5 days after epidural morphine administration.
40
Describe the pathophysiology and presentation of postdural puncture headache.
Puncturing the dura causes CSF to leak from the subarachnoid space. As CSF pressure is lost, the cerebral vessels dilate. In addition, the brainstem sags into the foramen magnum, which stretches the meninges and pulls on the tentorium. These factors contribute to PDH.
The classic presentation includes a fronto-occipital headache, which may be accompanied by nausea, emesis, photophobia, diplopia, and tinnitus. In the upright position, gravity makes the headache worse, while the supine position brings relief.
41
Discuss the risk factors for PDPH
Patient factors: Younger age, female, pregnancy
Practitioner factors: Cutting tip needle, larger diameter needle, using air for LOR with epidural, Needle perpendicular to longer-axis of the neuraxis
no effect: early ambulation, continuous spinal catheter (if placed after spinal block)
42
How do you treat PDPH?
Bed rest
hydration
NSAIDs
Caffeine (cerebral vasoconstriction)
Epidural blood patch
Opioids are not used to treat PDPH
43
How do you perform an epidural blood patch? what is the success rate?
it is a definitive tx. 90% success rate. if it does not improve after 2, take into consideration other etiologies.
Sterile technique draw 10-20 mL of venous blood and reintroduce to epidural space. When the patient sense pressure in her legs, buttocks, or back the injection is complete.
Useful for two reasons, increase CSF pressure by compressing the epidural and subarachnoid spaces and acts as a plug that prevents further leaks.
44
What are the common side effects of an epidural blood patch?
The most common side effects are backache and radicular pain.
45
What is the primary risk of neuraxial anesthesia in the anticoagulated patient? how does the complication present?
The risk of epidural hematoma is similar during block placement and catheter removal.
An epidural hematoma can cause paralysis. Presenting symptoms include lower extremity weakness, numbness, low back pain, and bowel and bladder dysfunction. Surgical decompression within 8 hrs offers the best chance of recovery.
46
Know this table
47
Know this table
48
Know this table
49
Compare and contrast the level of the conus medullaris and dural sac in the adult vs infant.
The spinal cord ends in a taper as the conus medullaris.
Adult: L1-L2
Infant: L3
The subarachnoid space terminate at the dural sac.
Adult: S2
Infant: S3
Notice the infant has the number 3 in both answers
50
What is the cause of cauda equina syndrome? What factors increase the risk?
Cause:
Neurotoxicity is the result of exposure to high concentrations of local anesthetic.
Factors that increase risk:
*5% lidocaine and spinal microcatheters.
*Micro catheters focus local anesthetic on a small area of the cord, exposing this region to a high concentration of LA.
51
How does cauda equina syndrome present? What is the tx?
S/Sx:
* Bowel and bladder dysfunction, sensory deficits, weakness, and/or paralysis
tx: supportive
52
what is the cause of transient neurologic symptoms? What factors increase the risk?
Cause: Patient positioning, stretching of the sciatic nerve, myofascial strain, and muscle spasm. It is highly unlikely that neurotoxicity causes TNS
Factors that increase risk:
* Lidocaine, lithotomy position, ambulatory surgery, and knee arthroscopy
typically observed after the use of spinal lidocaine
53
How do transient neurologic symptoms present? What is the treatment?
S&Sx:
*severe back and butt pain that radiates to both legs.
* it generally develops within 6-36 hrs and persists for 1-7 days
Tx:
*NSAIDs, opioid analgesics, and trigger point injections
54
What is the most common organism responsible for post-spinal bacterial meningitis?
When placing a neuraxial block, there are two routes by which an infectious organism can reach the CSF.
*Failure of aseptic technique
* Bacteria in the patient's blood at the time of SAB
Streptococcus viridans is one of the most common culprits responsible for post-spinal bacterial meningitis. It is commonly found in the mouth, and this is why it's so critical to wear a mask while performing and neuraxial block.
55
what is the best way to prepare the skin prior to neuraxial anesthesia?
Suitable methods to prepare the skin for neuraxial anesthesia include: chlorhexidine, isopropyl alcohol, and iodine solutions.
According to Miller, the best method is a combination of chlorhexidine and isopropyl alcohol.
Chlorhexidine is neurotoxic, so it's imperative that you allow it to dry completely before you penetrate the skin with the needle
56
what are the 5 main components of the brachial plexus?
Roots =5
trucks= 3
Divisions=6
cords =3
branches =5
mnemonic randy travis drinks cold beer
57
How many trunks are in the brachial plexus? Which nerve roots give rise to each trunk?
There are 3 trunks: superior, middle, and inferior
C5-6 -> superior truck
C7-> middle trunk
C8-T1-> Inferior
58
how many divisions are in the brachial plexus? which nerve roots give rise to each division?
there are 6 divisions ( 3 posterior and 3 anterior)
* each trunk gives rise to 1 anterior and 1 posterior division
* the three posterior divisions from all three trunks converge
* the anterior divisions from the superior and middle trunks converge.
* the anterior division from the inferior trunk continues by itself
59
How many cords are in the brachial plexus? Which nerve roots give rise to each cord?
There are 3 cords: posterior, lateral, and medial
C5-C7-> anterior divisions of superior and middle trunks -> lateral cord
C8-T1 -> anterior division of the inferior trunk -> medial cord
C5-T1 -> all 3 posterior divisions -> posterior cord
60
How many terminal branches are in the brachial plexus? Which roots give rise to each branch?
There are 5 terminal branches
* musculocutaneous (C5-7)
* axillary (C5-T1)
* Median (C5-T1)
* Radial (C5-T1)
* Ulnar (C8-T1)
Use the mnemonic to remember the 5 branches: Most Athletes Must Really Unite
61
Where do the roots turn into trunks?
The roots turn into trunks just beyond the lateral border of the scalene muscles
62
where do the trunks turn into divisions?
The trunks split into the divisions underneath the clavicle and over the first rib
63
Where do the divisions turn into cords?
The divisions converge into cords when the brachial plexus goes under the pectoralis minor muscle
64
When do cords turn into terminal branches?
The cords separate into the terminal branches in the axilla
65
Describe the sensory innervation of the upper extremity
as a general rule:
* the ventral portion is supplied by the median, ulnar, and musculocutaneous nerves ( lateral and medial cords)
* the dorsal portion is supplied by the radial and axillary nerves (posterior cord)
* the hand is the exception
66
how do you assess each branch of the brachial plexus (sensory and motor)?
Axillary- lateral upper arm at shoulder
Intercostobrachial & medial brachail cutaneous- medial upper arm to elbow
Medial antebrachial cutaneous- anterior upper arm, anterior medial forearm to the wrist
Musculotaneous (lateral antebrachial cutaneous)- lateral forearm to the wrist
Radial- Later upper arm, posterior arm below shoulder, posterior forearm, dorsum of the hand lateral to axial line of the 4th digit, radial side of the thumb
Median- Palmer side of 1st, 2nd, and 3rd digits ( palmer side and tips on dorsal side), Radial side of the 4th digit ( palmer side and tip on dorsal side)
Ulnar- Hyothenar eminence, ulnar side of the 4th digit and 5th digit
67
In addition to a brachial plexus block, which nerve must also be anesthetized to foster the tolerance of the upper extremity tourniquet?
Intercostobrachial blockade may foster tolerance for an upper arm tourniquet in an awake patient.
* it arises from T2
* A field block is required to block this nerve. With the arm abducted and externally rotated, begin at the deltoid prominence and mover inferiorly. A total of 5mL of local anesthetic is sufficient.
68
types of surgical procedures are well suited for an interscalene block? which are not?
The interscalene approach to the brachial plexus is indicated for procedures involving the shoulder, upper arm, and clavicle.
It is not the best option for procedures below the level of the elbow, as it frequently spares roots C8-T1 (lower trunk). This region innervates portions of the forearm and hand.
69
Be able to identify brachial plexus anatomy on ultrasound for an interscalene block.
70
Which approach to the brachial plexus is most likely to cause phrenic nerve paralysis? What are the clinical implications of this?
The phrenic nerve is nearly always blocked when performing an interscalene block, resulting in ipsilateral hemiparesis of the diaphragm.
* in healthy pts, this rarely results in respiratory compromise.
* in patients with respiratory disease, such as COPD, phrenic nerve paralysis may result in severe dyspnea, hypercapnia, and hypoxemia
71
Which approach of the brachial plexus is most likely to cause Horner's syndrome? What are the clinical implications of this?
Interscalene.
The stellate ganglion (cervicothoracic ganglion) is located at C7.
* this structure is other blocked during the interscalene approach, resulting in Horner's syndrome (ptosis, miosis, and anhidrosis)
* Horner's syndrome indicates a successful block
72
Discuss the relationship between shoulder arthroscopy, interscalene blockade, and hypotensive bradycardic episodes.
The bezold-jarisch reflex is the proposed mechanism for hypotensive bradycardic episodes during shoulder arthroscopy with interscalene blockade. These patients are typically in the sitting position or semi-upright position.
* S/sx include bradycardia, hotn, and syncope
* the theory is that venous pooling in the lower extremities reduces venous return. The combined effects of an unloaded ventricle, SNS stimulation, and epinephrine uptake (from the block) results in a profoundly underfilled ventricle that slows its rate to increase the diastolic filling time
73
What types of surgical procedures are well suited for supraclavicular block? Which are not?
*Indications include surgical procedures of the upper arm, elbow, wrist, and hand
* the supraclavicular block targets the trunks/divisions of the brachial plexus.
* it is not ideal for shoulder procedures since it does not reliably anesthetize the suprascapular nerve, which arises from the proximal upper trunk
74
What is the greatest risk of a supraventricular block? Why?
Pneumothorax is the greatest risk of the supraclavicular block because the pleura is immediately inferior to the first rib.
* tilting the transducer slightly caudal will place the first rib between the brachial plexus and the pleura, reducing the risk of pneumothorax
* the risk is higher in taller pts
* consider pneumothorax if the pt complains of cough, chest pain, or dyspnea after the block
* dyspnea tends to be delayed (rather than immediate) sign
75
What types of surgical procedures are well suited for infraclavicular block? Which are not?
The infraclavicular block targets the cords of the brachial plexus below the clavicle.
* indications include surgical procedures of the upper arm, elbow, wrist, and hand.
* it's a good alternative to the supraclavicular block in pts with respiratory insufficiency (lower risk of phrenic nerve blockade) and an axillary block in pts with limited extremity mobility
* it is not well suited for shoulder surgery
76
Describe the relationship of the terminal branches relative to the axillary artery.
The axillary block targets four terminal branches of the brachial plexus as they course distally with the axillary artery and vein along the humerus from the apex of the axilla.
* Musculocutaneous nerve is anterior and lateral.
* median nerve is anterior and medial
* Radial nerve is posterior and lateral
* Ulnar nerve is posterior and medial
77
What surgeries are well suited for an axillary block? which are not?
It provide anesthesia to the upper extremity distal to the elbow (forearm and hand)
The axillary block does not cover:
* the skin of the medial upper arm (intercostobrachial n.)
* the skin over the deltoid (axillary n.)
78
How do you block the radial nerve in the forearm?
Derived from the posterior cord of the brachial plexus.
*local anesthetic is injected between the biceps tendon and brachioradialis.
* volume 3-5 mLs
79
How do you block the ulnar nerve at the elbow?
Derived from the medial cord of the brachial plexus
* the elbow flexed 90 degrees and a local anesthetic is injected between the olecranon and medial epicondyle of the humerus
Volume 3-5 mLs
Using too high of a volume compress the ulnar nerve, resulting in ischemic injury
80
How do you block the median nerve at the forearm?
Derived from the lateral and the medial cords of the brachial plexus. In the antecubital fossa, a local anesthetic is injected medially to the brachial artery.
The brachial artery is located medially to the biceps tendon.
Volume 3-5mL
Avoid this block in the pt with carpal tunnel syndrome
81
How do you block the radial nerve at the wrist?
Anatomic landmarks:
Radial styloid
where to inject:
Subcutaneous injection (field block) of 10 mL proximal to the radial styloid.
A field block is used because there are several branches of the radial nerve at this point in the wrist
82
How do you block the ulnar nerve at the wrist?
Anatomic landmarks:
Ulnar styloid
Ulnar pulse
Flexor carpi ulnaris tendon
Where to inject:
Injection 3-5 mL medial to and below the flexor carpi ulnaris tendon
Confirm negative aspiration due to proximity to the ulnar artery
83
How do you block the median nerve at the wrist?
Anatomic landmarks:
Flexor carpi radialis tendon
Flexor palmaris longus tendon
Where to inject
Inject 5mL between the flexor carpi radialis tendon and the flexor palmaris longs tendon
84
Name the 6 terminal branches of the lumbar plexus
The lumbar plexus arises the anterior rami of L1-4 , with an occasional contribution of T12, It gives rise to 6 nerves
Iliohypogastic - I L1
Ilioinguinal - invariably L1
Genitofemoral --Get L1 +L2
Lateral femoral cutaneous - Lazy L2+ L3
Obturator - On L2+L3+ L4
Femoral - Fridays L2+L3+L4
85
Know this table
86
Describe the sensory innervation to the lower extremity.
87
What nerves are anesthetized by the psoas compartment block? What is another name for this block?
The psoas compartment block (lumbar plexus block) targets three major nerves of the lumbar plexus:
Lateral femoral cutaneous
Femoral
obturator
This block is useful when neuraxial anesthesia is contraindicated and/or anesthesia to one lower extremity is preferred
88
Discuss the anatomy of the femoral triangle.
The femoral nerve arises from the posterior divisions of L2-L4. After these nerve roots exit the spinal column, they give rise to the femoral nerve within the psoas major. The 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 the inguinal ligament
* anterior to the iliopsoas muscle
* inferior to the fascia and fascia iliaca
The triangle is shaped like the "SAIL" of a ship, so we can use this as a mnemonic to remember its borders:
Inside the triangle, the femoral nerve runs:
* Deep to the inguinal ligament
* Anterior to the iliopsoas muscle
* Inferior to the fascia lata and fascia iliaca
The triangle is shaped like the "SAIL" of the ship:
* S= Sartorius muscle
* A= Adductor longus muscle
* IL= Inguinal ligament
Use "VAN" for the structures inside the triangle (medial -> lateral):
Vein, artery, nerve
89
Discuss the anatomy and innervation of the anterior and posterior branches of the femoral nerve.
the femoral nerve divides into anterior and posterior branches. This occurs either just before or just after the nerve passes under the inguinal ligament.
90
Discuss the anatomy and innervation of the anterior and posterior branches of the femoral nerve.
The femoral nerve divides into anterior and posterior branches. This occurs either just before or just after the nerve passes under the inguinal ligament.
* The anterior branch innervates the ventral surface of the thigh and the sartorius muscle.
* the posterior branch innervates quadriceps muscles, knee joint and its medial ligament
* the posterior branch gives rise to the saphenous nerve.
91
Describe the innervation of the saphenous nerve. What are the implications of this in the context of surgery on the lower extremity?
The saphenous nerve is the terminal branch of the posterior division of the femoral nerve.
* it provides sensory innervation from the medial aspect of the knee to the medial malleolus
* there is no motor component
the block is useful when combined with a popliteal or ankle block, as these don't capture the saphenous distribution
92
The anatomy of the sciatic nerve
the sciatic nerve arises from L4-5 and S1-3
* the sciatic nerve is actually two nerves contained within a sheath (tibial and peroneal)
* it exits the pelvis inferior to the piriformis muscle via the great sacrosciatic foramen.
* as it continues caudally, it passes between the major trochanter and the tuberosity of the ischium into the lower third of the thigh. This is where the sciatic nerve divides into the tibial and the common peroneal nerves
93
Describe the relevant anatomy for the popliteal block.
The 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 laterally 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.
94
Name the 5 terminal nerves at the level of the ankle. What is the origin for each nerve?
Five nerves provide innervation to the foot. Each one is a branch of either the femoral or sciatic nerves.
* the three sensory nerves begin with an "s"
* the 2 mixed sensory and motor nerves don't begin with s
Femoral-> saphenous
Sciatic-> deep peroneal, superficial peroneal, sural, posterior tibial
95
Describe the sensory innervation of the foot and ankle
96
Describe the nerves location in cross section
97
At the level of the ankle, which nerve is not immediately adjacent to a vascular structure?
Superficial peroneal nerve
All the other nerves are very close to an artery an/or vein, therefore blockade of the superficial peroneal nerve is LEAST likely to result in intravascular injection
98
What is the difference between PECS1 and PEC2 block?
PECS 1
* injection site= fascial plane between the pec major and pec minor
PECS2
* Injection site= fascial plane between the pec major and pec minor (injection 1) and in the fascial plane between the pec and serratus anterior (injection 2)
99
Describe the anatomy and distribution of the intercostal nerves
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. The nerve's proximity to these vascular structures has implications for local anesthetic toxicity.
100
Describe the distribution of anesthesia with a paravertebral block
Intervertebral blocks provide coverage for only one dermatome level, the procedure must be performed at each level where anesthesia is desired.
101
What are the boundaries of the paravertebral space?
The paravertebral space (PVS) is a wedge-shaped area with the following boundaries
1. Anterior-> parietal pleura
2. Medial -> vertebral body and intravertebral foramen
3. Posterior -> transverse process and superior costotransverse ligament
102
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
103
What is an erector spinae block?
the erector spinae block (ESB) is a fascial plane technique that targets the dorsal and ventral rami of the thoracolumbar nerves at the level of injection. Injecting local anesthetic deep to the erector spinae muscle group and superficial to the transverse process causes significant craniocaudal spread.
104
Describe the triangle of Petit.
The inferior lumbar triangle (ie. triangle of petit) provides a key anatomic reference point for performing a TAP block with a landmark technique. You can directly localize the internal oblique muscle (IO) at this location. In most pts, you can find the IO 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
* the transverse abdominis is deep to the IO
105
What is the goal of a TAP block?
The TAP block is a fascial plane block. The goal is to place local anesthetic in the fascial plane between the internal oblique (IO) and transverse abdominis (TA) muscles. The thoracolumbar nerves arising from T6-L1 innervates the IO and TA muscles.
These are 3 approaches (subcostal, lateral, and posterior), and you can use them individually or in combination. The location of the surgical procedure informs the approach you select:
* subcostal approach=> procedures above the umbilicus
* lateral and posterior approach-> procedures below the umbilicus
106
What are the indications for a rectus sheath block?
The rectus sheath block is used in procedures that require a midline abdominal incision. Indication include umbilical hernia repair in the pediatric population, cesarean section when a midline incision is required, and postpartum laparoscopic tubal ligation.
107
Describe the thoracolumbar fascia
The thoracolumbar fascia (TLF), understand it's highly complex network of connective tissue involved in the lumbar paravertebral area and the anterolateral abdominal wall.
* the thoracolumbar fascia consists of 3 layers: anterior, middle, and posterior.
* the quadratus lumborum muscle resides between the anterior to the middle layers of the TLF.
108
Which nerve roots are the MOST resistant to the effects of local anesthetics?
L5 and S1
* They are the largest spinal nerves
* The L5-S1 interspace is the largest interspace in the vertebral column
* Most resistant to local anesthetic
109
In what order dose regression of spinal anesthesia occur?
1. Motor function
2. Touch
3. Pinprick
4. Temperature
Autonomic, temperature, pain, touch, pressure, Motor, vibration, proprioception.
Last to be blocked is first to come back
110
A pt with severe COPD received a spinal anesthetic. Impairment of which muscles is MOST likely to contribute to respiratory failure?
Intercostals (inspiration and expiration) and abdominal (Cough and clear secretions)
Neuraxial anesthesia impairs accessory muscle function; vital capacity and expiratory respiratory volume are decreased
111
A reduction in which of the following is the primary mechanism for hypotension after a T4 spinal anesthetic?
decrease in preload
Cardiac SNS innervation - T1-T4
Vascular SNS innervation - T1-L2
Sympathectomy with spinal anesthesia can be as high as 2-6 levels above the level of sensory blockade. By contrast, sympathectomy is the same as the sensory level during epidural anesthesia
Cardiovascular consequences of sympathectomy include:
* Decreased preload (venodilation)
* Decreased SV (decreased preload)
* Decreased Afterload (arterial dilation)
* Decreased HR ( decreased cardiac accelerator function and decreased preload)
Because 75% of the blood volume resides in the venous circulation, dilation of the venous capacitance vessels (decreased preload) is the primary mechanism of hypotension with a high spinal.
The body compensates with vasoconstriction above the level of sympathectomy, however a higher block limits the effectiveness of this compensatory mechanism.
112
Compared to an epidural, which are more common with a spinal?
Cauda equina syndrome (high LA concentrations may be neurotoxic) and meningitis ( Direct contamination of CSF)
Complications more likely with epidural anesthesia:
* Epidural abscess (direct contamination of epidural space)
* Spinal hematoma (large needle= large hole)
* Traumatic spinal cord injury (large needle= large injury)
113
A patient with an epidural catheter at the L4-5 interspace received 20 mL of 0.25% bupivacaine. After 25 minutes, the patient loses consciousness. What is the MOST likely explanation for this complication?
Subdural injection
presents 15-30 minutes afterward with high but patchy block. While the epidural space extends to the foramen magnum, the subdural space extends intracranially. If local anesthetic reaches the brain, unconsciousness can occur. Tx is supportive.
114
The lateral and medial cords of the brachial plexus supply the:
Median nerve, musculocutaneous nerve, ulnar nerve
Posterior cord supplies the radial and axillary nerve
the circumflex nerve is another name for the axillary nerve
115
Which peripheral nerve block has the HIGHEST incidence of chylothorax?
infraclavicular
The thoracic duct drains into the subclavian vein, and injury to the structure can cause a chylothorax. Left side is larger than right, more susceptible to injury
116
Acceptable movements form interscalene nerve stimulation
* Arm abduction (deltoid muscle)
* Forearm flexion (biceps muscle)
* Forearm extension (triceps muscle)
* Arm internal rotation (pectoralis major muscle)
not okay: hiccups (phrenic nerve) and scapula or trapezius movement from stimulation (cervical plexus)
117
How each nerve transitions through brachial plexus
the roots convert to trunks at the lateral border of the scalene muscles
the trucks change over to divisions under the clavicle and over the 1st rib
the divisions converge into cords as they course under the pectoralis minor muscle
the cords become the terminal branches beyond the lateral border of the pectoralis minor muscle (in the axilla)
118
Complications of interscalene blockade are more common in patient with:
Any impairments of diaphragmatic function must be considered in any pt with decreased pulmonary reserve. Examples: Severe COPD, neuromuscular disease (myasthenia gravis), or contralateral lobectomy or pneumonectomy
119
which of the following increases the risk of pneumothorax during a supraclavicular block?
Performing a supraclavicular block on the right side increases the chances of pneumothorax.
Pneumothorax is the greatest risk for supraclavicular block. Since the cupola of the lung is higher on the right side, it is more likely to be punctured during a supraclavicular block on the right side
Tall, thin patients have a greater risk of pneumothorax. Suspect pneumo if the pt coughs or complains of chest pain
the use of a 5cm needle is standard practice
120
Most common causes of median nerve injury:
AC IV insertion
Axillary approach to the brachial plexus
121
A pt has an axillary block. Blockade of which of the following nerves will enhance an awake patient's tolerance of an upper arm tourniquet?
Intercostobrachial
arises from T2. A field block is usually required to anesthetize this nerve.
122
Drugs and their affect on IOP
Drugs that decrease IOP
* All volatile potent anesthetics
* Fentanyl
* Propofol
Increase IOP:
* Succ's
* Neostigmine
* Atropine
Drugs that do not affect IOP
* N2O
* Ketamine
* Non-depolarizing neuromuscular blocking agents
* Sugammadex
123
Venous plexuses are generally found in which parts of the epidural space?
Lateral, and anterior
124
What structures are anesthetized when a local anesthetic is injected into the paravertebral space?
the paravertebral space is found lateral to the vertebral column. Other anatomic features surrounding this area include the rib and parietal pleura of the lung. Within this space, spinal nerves and their sympathetic branches are infiltrated with local anesthetic.
Bathing the paravertebral space with a long-acting local anesthetic creates a somatic and sympathetic block. It is used in pediatric for postoperative pain control after thoracic and upper abdominal surgery.
125
Ultrasound artifact with it's description
* The bayonet effect is commonly seen during popliteal block with a lateral in-plane approach since there is typically a great deal of adipose tissue over the nerve. Adipose tissue has a slower speed of sound than muscle. Ex: Apparent bending of the block needle due to heterogenous soft tissue.
* the comet tail artifact is a reverberation artifact and is helpful in identifying strong reflective tissue such as the pleura
* Acoustic enhancement ( Aka posterior acoustic enhancement or increased through-transmission) occurs because most fluids do not attenuate the sound beam. If the beam passes through a blood vessel, acoustic enhancement deep to the vessel can be mistaken for a nerve.
* Acoustic shadows occur deep to strong reflecting structures or deep to edges of blood vessels
126
Which technique is recommended when a large surface area of tissue requires infiltration anesthesia?
Use a large volume of low concentration local anesthetic solution
127
A deep cervical plexus block for carotid endarterectomy has the risk of injection of local anesthetic into the:
Epidural space, ver
128
The application of a eutectic mixture of lidocaine and prilocaine has what effects on the local vascular bed?
Vasoconstriction in the first hour after application
and vasodilation after 2 or more hours after application
129
What solution is recommended as a test dose when using peripheral nerve stimulation-guided nerve blocks?
5% dextrose in water- increases current density and either maintains or augments twitch response to stimulation. Only 1-2mLs is necessary for a test dose.
If ultrasound guidance is being used, it is recommended that the D5W test dose be used to visualize the spread and confirm nerve localization before dosing with a local anesthetic
130
which nerve must be blocked to prevent contraction of the orbicularis muscle for ophthalmic surgical procedures?
facial
The zygomatic branch of the facial nerve innervates the orbicularis muscle. This nerve is typically blocked to prevent lid squeezing during eye surgery. The other cranial nerves listed innervate the six extraocular muscles: (lateral rectus (abducens), superior oblique (trochlear), and the "rest" inferior oblique, superior, medial, and inferior recti (oculomotor)
131
Which part of the spinal cord is the MOST prone to ischemia?
Anterior grey matter
132
Which part of the spinal cord is the MOST prone to ischemia?
Anterior grey matter
133
Which concentration of local anesthetic is appropriate for use with a continuous catheter technique for a peripheral nerve block?
0.25% bupivacaine
Lidocaine or mepivacaine should be infused in concentrations no greater than 1 to 1.5%, while bupivacaine concentrations should be limited to 0.125 to 0.5%,
134
which nerve should be blocked for a cleft palate repair?
infraorbital
135
Identify the surface landmarks necessary for performing a psoas compartment (AKA lumbar plexus) block.
Spinous process of L4
and posterior superior iliac spine
136
The MOST proximal course of the sciatic nerve passes between with two bony landmarks?
greater trochanter and ischial tuberosity
137
Which peripheral nerves are the targets of the transversus abdominis plane block (TAP)?
Iliohypogastric and ilioinguinal
also subcostal
These blocks must be done bilaterally
138
The vertebral canal is smallest at which level?
Thoracic
