Regional Anesthesia Flashcards
According to the American Society of Regional Anesthesia (ASRA) guidelines, epidural catheter placement in obstetric patients should be delayed for at least how long after administration of a therapeutic dose of low molecular weight (LMW) heparin?
24 hours
Patients receiving higher therapeutic doses of LMWH are at increased risk compared to patients receiving lower prophylactic doses of LMWH.
ASRA guidelines for neuraxial placement:
- wait at least 24 hours following a therapeutic dose of LMWH
- wait at least 10-12 hours following a prophylactic dose of LMWH
What is the indication for a stellate nerve block and what are its innervations?
This block is often used in patients with head, neck, arm, and uppercuts pain.
It usually blocks the upper thoracic as well as all cervical ganglia (sympathetic), down to T5 ganglia
What are the risk factors for a postural puncture headache?
Factors that increase the risk for PDPH are:
- Young age
- Female gender
- Pregnancy
What are the recommendations for cessation of therapy of baby aspirin, clopidogrel, ticlopidine, abciximab, and eptifibatide for regional anesthesia?
Baby aspirin is NOT a contraindication to regional anesthesia.
Ticlopidine should be stopped 2 weeks prior.
Clopidogrel should be stopped 1 week prior.
Abciximab and eptifibatide are stopped 24-48 hours prior
Describe an ankle block (all of the nerves blocked and their locations)
1) Saphenous nerve ( the only nerve in the block deriving from the femoral nerve) provides superficial sensation to the anteromedial part of the foot and is blocked by subcutaneous infiltration of local anesthetic between the medial malleolus and the extensor hallucis longus tendon
2) Posterior tibial nerve provides sensation to the heel, the medial part of the sole of the foot and part of the lateral sole. It is blocked by deep infiltration between the posterior tibial artery and the medial malleolus
3) Superficial peroneal nerve provides cutaneous sensation to most of the dorm of the foot and the 5 toes. It is blocked between the lateral malleolus and the extensor digitorum longus (anterior border of the medial malleolus)
4) Deep peroneal nerve innervates the toe extensors and provides sensory to the medial half of the dorsum of the foot (specifically the 1st and 2nd digits). It is blocked by identifying the groove between the extensor hallucis longus and the extensor digitorum longus tendons (lateral to the dorsalis pedis artery pulse).
5) Sural nerve provides sensation to the lateral foot and is blocked between the lateral malleolus and the tendocalcaneus.
What nerve is typically missed in an interscalene block?
Ulnar nerve sparing occurs in 50% of patients
What respiratory parameters change with spinal anesthesia?
Decreases in maximum expiratory volume & vital capacity due to relaxation of the abdominal muscles
Max breathing capacity, inspiratory volume, and tidal volumes are unchanged
Where is the stellate ganglion located anatomically? What is it a fusion of?
It is located at the level of C7, anterior to the transverse process of C7, anterior to the neck of the 1st rib, and just below the subclavian artery.
It is a sympathetic ganglion formed by the fusion of the inferior cervical ganglion and the 1st thoracic ganglion?
For a stellate ganglion block, what is the anatomical landmark?
Chassaignac’s tubercle, which is the anterior tubercle of the transverse process of C6 vertebrate, which corresponds to the anatomical level of the cricoid cartilage.
Insertion of the needle at the medial edge of the sternocleidomastoid muscle, just below the cricoid cartilage
How is the Glossopharyngeal nerve blocked?
By infiltration of 2ml of 2% lidocaine into the tonsillar pillar
Where are the celiac ganglia located?
Celiac ganglia vary in number (1-5) and are located at the level of the body of L1, posterior to the vena cava and pancreas and lateral to the aorta.
What anatomical landmark defines the ulnar nerve block?
One finger breadth above the medial epicondyle
Describe the hypoglossal nerve’s function
It is a motor nerve and innervates the intrinsic muscles of the tongue (except the palatoglossus muscle).
It does NOT provide sensory supply to any of the airway structures and is therefore, not necessary to block for airway topicalization
What nerves are necessary to block for an awake nasotracheal intubation?
Anterior ethmoidal nerve (anteriorly), a branch of the ophthalmic division of the trigeminal nerve & sphenoplatine nerves (posteriorly), branches of the maxillary division of the trigeminal nerve.
What areas does the glossopharyngeal nerve provide sensation to?
Posterior 1/3rd of the tongue
The roof of the pharynx, the tonsils, and the undersurface of the soft palate
What is the superior laryngeal nerve a branch of and what are its branches functions?
It is a branch of the VAGUS nerve
The EXTERNAL branch is motor and innervates the cricothyroid muscle
The INTERNAL branch is sensory to the larynx above the level of the glottis.
What does the recurrent laryngeal nerve innervate?
It is another branch of the VAGUS nerve and supplies all the muscles of the larynx except the cricothyroid muscle and provides sensory supply to the larynx below the level of the glottis
What does the psoas compartment block provide anesthesia for? How does a continuous block compare to a PCA alone or a continuous femoral nerve block?
a.k.a. the lumbar plexus block
It provides analgesia and anesthesia to the entire lumbar plexus which includes the anterior, lateral, and medial thigh, the knee, and the saphenous nerve below the knee
A continuous psoas compartment block provides superior analgesia to PCA alone
It provides similar analgesia to continuous femoral nerve block after TKA. However, the psoas compartment block provides analgesia to the obturator and lateral femoral cutaneous nerve unlike the femoral nerve.
What nerve needs to be blocked to provide analgesia to the posterior knee?
The sciatic nerve
Describe the difference between complex regional pain syndrome (CRPS) type 1 vs type 2
CRPS type 1 usually occurs following (minor) trauma which does not demonstrate tissue damage or nerve lesions, while CRPS type 2 (causalgia) is associated with a major nerve injury
What is the treatment for trigeminal neuralgia?
Medications: Carbamazepine or
Procedure: A Gasserian Ganglion Block
If the nerve is blocked and NOT the ganglion this can result in deafferentation pain in the nerve distribution
Always block with local anesthetic before alcohol or phenol or attempted.
At what level does the spinal cord end at birth? In adults?
At birth to 1 year, the spinal cord ends at L3
In adults, the spinal cord ends at L1
How does an epidural abscess present vs. arachnoiditis vs. epidural hematoma?
An epidural abscess presents as localized back pain that worsens and develops radicular changes with a median onset of 7 to 8 DAYS
*If untreated, patients will develop sensory and motor deficits and eventually paralysis.
Arachnoiditis is a more subacute/chronic condition that manifests as radicular changes/ back pain over SEVERAL MONTHS.
An epidural hematoma proceeds more rapidly to produce sensory and motor deficits within HOURS.
How does a patient with anterior spinal artery syndrome usually present?
It is predominantly characterized by motor changes. There is no associated pain.
At the level of the popliteal fossa, where is the sciatic nerve located?
Between the biceps femoris and semitendinosus muscles, posterior to popliteal artery
What are the branches of the superior laryngeal nerve? What are their functions?
The external branch (motor via the crycothyroid muscle)
The internal branch (sensory) above the vocal cords to epiglottis
Describe the oculocardiac reflex
Afferent limb is the trigeminal nerve
Efferent limb is the vagus nerve
What is the mechanism which causes orthostatic hypotension in a celiac plexus block?
Blockade of sympathetic efferents resulting in splanchnic and peripheral vasodilatation
From where (what roots) does the median nerve derive? How can it be injured? What would the manifestations of injury be?
The median nerve arises from C6-T1
It can be injured from wrist extension or via injury to the brachial plexus during any procedure
Atrophy of the THENAR EMINENCE and therefore the inability to oppose the thumb is classic
What level of the spinous process does the inferior edge of the scapula correspond to?
T7
What spinous process does the iliac crest in an adult correspond to?
L4
What level of the spine does the conus medullaris (the terminal end of the spinal cord) correspond to?
L1 or L2
What is the blood supply to the spine?
One anterior spinal artery supplying 75% of the cord and 2 posterior spinal arteries supplying the remaining 25%
What are the symptoms of injury to the conus medullaris?
Bladder and bowel dysfunction
Impotence
Loss of superficial reflexes
How many vertebrae does the vertebral column consists of?
It usually consists of 24 articulating vertebrae & 9 fused vertebrae in the sacrum and the coccyx
( The number of cervical vertebrae is very rarely increased or diminished
What is the typical presentation of Facet syndrome?
Facet back pain tends to be off midline and goes into the buttocks
How would a patient with ankylosing spondylitis present? How can it be diagnosed?
Onset of back pain with no specific injury event.
Back stiffness that occurs in the mornings and gets better with exercise.
Histocompatability testing (which would detect HLA-B27) may help with diagnosis
What nerve needs to be blocked to obliterate the gag reflex?
The Glossopharyngeal nerve
What division of the trigeminal nerve innervates the nasopharynx?
The Maxillary Division of the trigeminal nerve
What nerves comprise the lumbar plexus?
It is formed by the ventral rami of L1-L3 and the superior branch of L4 (contribution from T12 occurs in ~ 50% of cases)
The branches include: Iliohypogastric Ilioinguinal Genitofemoral Lateral femoral cutaneous Femoral Obturator
The carotid sinus is innervated by what nerve(s)?
The Glossopharyngeal and the Vagus nerves
What does the Psoas Compartment Block provide analgesia to?
a.k.a. Lumbar Plexus Block
I provides analgesia and anesthesia to the entire lumbar plexus, which includes the anterior, lateral, and medial thigh, the knee and the saphenous nerve below the knee.
Provides analgesica similar to a continuous femoral nerve block for a TKA
How is analgesia to the posterior knee achieved?
A Sciatic Nerve Block, which is not part of the lumbar plexus
Sensory innervation to the entire larynx is supplied by what nerve?
The Recurrent Laryngeal Nerve
What nerve can be damage during thoracic aortic surgery and why?
The LEFT recurrent laryngeal nerve can be damaged because on the left, it leaves the vagus as it crosses the aortic arch, passes under the aorta and ascends on the right
What nerves need to be blocked for an awake fiberoptic intubation? How?
CN IX (Glossopharyngeal): sensory to the posterior tongue and superior border of epiglottis - topical/tonsillar pillar
Superior Laryngeal Nerve (SLN): Internal branch provides sensory to the inferior epiglottis to cords
External branch provides motor to cricothyroid muscle
- Nerve block at hyoid
Recurrent Laryngeal Nerve (RLN): Motor to larynx (except cricothyroid) and sensory below the cords - typically topicalized
How does etomidate affect the amplitude and latency of SSEPs?
Etomidate increases BOTH amplitude and latency
Landmarks for Saphenous nerve block at the ankle
Between the MEDIAL malleolus and the extensor hallucis longus tendon
Landmarks for Posterior tibial nerve block at the ankle
Between the posterior tibial artery and the MEDIAL malleolus
Landmarks for Superficial peroneal nerve block at the ankle
Subcutaneous infiltration of local anesthetic between the lateral malleolus and the extensor digitorum longus
Landmarks for Deep peroneal nerve block at the ankle
Groove between the extensor hallucis longus and the extensor digitorum longus tendons
Landmarks for Sural nerve block at the ankle
Between the LATERAL malleolus and the tendocalcaneus
How does facet back pain present?
Facet pain tends to be off midline and radiates to the buttocks, thigh, and knee.
Spinal tumors after the age of 50 tend to indicate ….?
Malignancy
What vertebrae level(s) tend to be involved in back pain 80% of the time?
Lumbosacral discs are L5-S1 or L4-5 about 90% of the time, pain radiates along a dermatome
What is the blood supply to the larynx?
The Thyroid arteries
What artery gives rise to the cricothyroid artery?
The Superior thyroid artery
What is the order (from greatest to least) of regional blocks’ systemic absorption of local anesthetics?
1) Intercostal nerve blocks
2) Caudal and epidural injections
3) Brachial plexus blocks
4) Spinal injections
The median nerve derives from what spinal levels? If injured, what is the resultant deformity?
The median nerve arises from C6-T1.
If injured (from wrist extension or via the brachial plexus) atrophy of the thenar eminence and the inability to oppose the thumb is classically seen.
At what level of the brachial plexus is the supraclavicular block performed?
At the trunks just before they become divisions
What is the order of nerve fiber blockade?
1) Sympathetic
2) Pain
3) Proprioception
4) Motor
What is characteristic about Facet syndrome back pain?
Facet pain tends to be off midline and goes into the buttocks
What is characteristic about Ankylosing spondylitis back pain? How is it diagnosed?
Back pain/stiffness occurring in the morning. Improves with exercise.
Histocompatability testing for HLA-B27 may help with diagnosis
Describe Piriformis Syndrome
It comprises 5-6% of patients with back and leg pain.
Usually complaint of buttock pain that extends from the sacrum to the greater trochanter with/without radiation down the ipsilateral leg.
Prolonged sitting aggravates the pain as well as rising from the sitting position
At the level of the popliteal fossa, where is the sciatic nerve located?
Between the biceps femurs and the semitendinosus muscles, posterior to the popliteal artery
The paramedic epidural procedure passes through what layers of the spine?
The needle is inserted below and lateral to the spine and passes through:
1) skin
2) subcutaneous tissue
3) ligamentum flavum
(bypassing supraspinous and interspinous ligaments)
What is the best technique with the highest success rate to perform an axillary block?
3 to 4 injection neuromuscular technique
What risk is associated with the inter scalene block 100% of the time?
Phrenic nerve paralysis
What does the addition of epinephrine to a bupivicaine epidural block?
Epinephrine increases the duration of the MOTOR blockade but NOT the sensory block.
What brachial plexus block is considered the “spinal anesthesia” of the upper extremity?
The Supraclavicular blockade of the brachial plexus provides a rapid onset of dense anesthesia of the arm with a single injection. At this level, it has the greatest likelihood of blocking all of the branches of the brachial plexus.
Ideal for surgeries involving the arm and forearm, from the lower humerus down to the hand.
Define hypoesthesia
Decreased sensation in a given area
Define dyaesthesia
An unpleasant sensation with or without a stimulus
Define anesthesia dolorosa
Pailin an area that lacks sensation
Define paraesthesia
Abnormal sensation of tingling, tickling, pricking, or burning
A test dose of epinephrine administered via the epidural catheter must raise the heart rate by what amount in order to be considered a positive dose?
A test dose consists of 3 mL of local anesthetic with 5 micrograms/mL epinephrine.
An IV injection will increase the heart rate by approximately 30 bpm
What structures are noted on an ultrasound guided stellate ganglion block?
1) The longus colli muscle, which lies anterior to the first rib. (the stellate ganglion is found the lateral border)
2) Cricoid cartilage
3) Thyroid gland
What are indications of a successful stellate ganglion block?
Horner’s syndrome
Increase in temperature
How long does it take to see results from lumbar epidural steroid injections (LESIs)?
LESIs routinely require a series of 3 injections before a response can be elucidated.
What are the risk factors associated with Obesity Hypoventilation Syndrome (OHS)? Diagnostic criteria?
Risk Factors: Male sex Ages 50-70 years h/o Chronic fatigue Mood disorders (e.g. Bipolar) Nocturnal headaches Dyspnea with minimal exertion Hypersomnolence
Diagnostic criteria:
BMI > 30
Awake arterial hypercapnia (PaCO2 > 45 mmHg)
No other cause for chronic hypoventilation
Abnormal polysomnography (hypoventilation with hypercapnia with or without OSA)
Describe a TAP block.
The transverses abdominus plane (TAP) block is used to provide analgesia after surgery involving the abdominal wall.
It requires injection of local anesthetic into a plane between the transverses abdominus and the internal rectus abdominus muscle.
What will a high thoracic epidural do the lung volumes?
It will diminish the ERV by 20% though this decrease is not associated with a decrease in overall blood gas status.
What level of the brachial plexus is blocked with an infraclavicular block?
Lateral, posterior, and medial cords
What is the first symptom of an intravascular injection of lidocaine without epinephrine?
Light headedness
Describe the brachial plexus from the level of the cords
1) Lateral cord —> Musculocutenous nerve (C5-6)
2) Lateral and Medial cords—> Median nerve (C6-8,T1)
3) Medial cord —> Ulnar nerve (C8, T1)
4) Posterior cord —-> axillary nerve that terminates into the radial nerve (C5-8)
How does median nerve injury present?
Atrophy of the thenar muscle and loss of the ability to oppose the thumb
Where should the needle for an intercostal nerve block be positioned?
Inferior to the costal margin of the intended rib.
Where does the sciatic nerve lye within the popliteal fossa?
The sciatic nerve is between the biceps femoris and semitendonus muscles, posterior to the popliteal artery
What is the most common arrhythmia observed with bupivicaine local anesthetic toxicity?
Ventricular tachycardia
What is the earliest sign of intravascular injection of a test dose?
T wave elevation greater than 25%, which may or may not be accompanied by an increase in HR.
What increase in HR can be noted as significant with an inadvertent intravascular injection of a test dose in an anesthetized patient? What ECG finding is significant? What change in BP?
*An elevation in HR of 10 or more bpm
(the standard HR response is 20 bpm)
- A 25% increase in the T wave amplitude
- An increase in systolic BP by 15 mmHg
What blocks have the greatest vascularity (greatest to least)?
“ICE Beyond Slight Freezing”
Intercostal > Caudal > Epidural > Brachial > Sciatic > Femoral
*the spinal canal has no vessels, so there is no risk for IV injection
