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146 Cards in this Set
- Front
- Back
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Spinal anesthesia is accomplished by injecting LA into the CSF contained within what space?
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Subarachnoid space
Intrathecal space |
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Epidural anesthesia is accomplished by injecting LA into the epidural space which lies_________?
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within the vertebral canal but outside or superficial to the dural sac
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What landmark does one use to perform a caudal anesthetic?
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sacral hiatus
Sacral cornu |
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What spinal level are subarachnoid injections limited to and why?
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The spinal cord in an adult ends at L1
Spinal injections are limited to the lumbar region below the level of the spinal cord. |
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List some advantages of spinal anesthesia over epidural anesthesia.
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1) takes less time to perform
2) causes less discomfort during placement 3) requires less LA 4) produces more intense sensory and motor block 5) correct needle placement confirmed by clearly defined endpoint (CSF) |
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List some advantages of epidural anesthesia over spinal anesthesia.
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1) decreased risk for PDPH
2) lower incidence of systemic hypotension 3) ability to produce segmental sensory block 4) greater control over the intensity of sensory anesthesia and motor block achieved by adjustment of LA concentration 5) titration of block to duration of surgery 6) catheter provide means for long-term administration of LA or opioid |
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Why is the long-term administration of LA or opioid in an epidural catheter advantageous?
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Effective control of postoperative or obstetric pain.
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Do you use neuromuscular blocking drugs in the presence of spinal or epidural anesthesia/analgesia?
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No need for NMBD's d/t neuraxial anesthesia provides profound skeletal muscle relaxation.
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What is the number one fear of patients about to undergo neuraxial anesthesia?
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Permanent nerve damage
Paralysis |
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Thoracic convexity is best described as__________?
a) lordosis b) scoliosis c) kyphosis |
c) kyphosis
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Lumbar concavity is described as__________?
a) lordosis b) scoliosis c) kyphosis |
a) lordosis
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How many cervical vertebrae?
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7
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How many thoracic vertebrae?
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12
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How many lumbar vertebrae?
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5
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How many true vertebrae are there?
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24
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How amy false or fixed vertebrae are there?
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5
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What are the false or fixed vertebrae called
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sacrum
consists of 5 fixed or false vertebrae |
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What is the opening between the unfused lamina of the 4th and 5th sacral vertebrae called?
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Sacral Hiatus
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What % of adults are missing the sacral hiatus?
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8%
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The line drawn between the iliac crests is otherwise known as_______?
What spinal level |
Intercristal line
Tuffiers line L4 |
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What interspace connects a line drawn between the lower limits of the scapulae?
What is this spot used for? |
T7-8
Used to guide nedle placement for passage of a catheter into the thoracic epidural space. |
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The terminal portion of the 12th rib intersects which vertebral body?
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L2
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Posterior iliac spines indicate which vertebral body?
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S2
Which is the caudal limit of the dural sac in most adults. |
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What is the first ligament that a needle will traverse when using a midline approach to the vertebral canal?
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The supraspinous ligament
runs superficially along the spinous process |
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Where does the spinal cord usually terminate in adults?
Where does it terminate at birth? |
Adults- lower border of L1
Birth- L3 |
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What are the 3 layers of connective tissue called that surround the spinal cord?
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Meninges
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What are the names of the 3 meninges?
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Dura mater
Arachnoid membrane Pia |
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The outermost meninge is called the __________ and it originates at the ___________ and continues caudal to terminate at ______________.
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Dura mater
originates at foramen magnum Terminates at S1-S4 baby miller 5th ed p. 245-246 |
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Which meninge is the tough fibroelastic membrane that provides structural support and a fairly impenetrable barrier that normally prevents displacement of an epidural catheter into the fluid-filled subarachnoid space?
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Dura mater
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Which meninge is more delicate and serves as the major pharmacologic barrier preventing movement of drug from epidural to subarachnoid space?
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Arachnoid membrane
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Which meninge is the innermost layer, highly vascular structure closely applied to the cord that forms the inner border of the subarachnoid space?
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Pia
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What is the filum terminale and where does it usually end?
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Filum terminale is the distal thin filament of the pia which becomes enveloped by the dura at the caudal termination of the dural sac generally around S2
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Caudally the spinal cord tapers into what is known as the ____________?
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Cauda equina
or Conus medullaris |
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How many pairs of spinal nerves are there?
Name them (generally) |
31 pairs of spinal nerves
8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal |
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Briefly describe how the cervical nerves pass with the respective cervical vertebra
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They pass above the cervical vertebra
Since there are 8 cervical nerves and only 7 cervical vertebra the 8th passes below the cervical vertebra and above the first thoracic vertebra |
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Briefly describe how all the other non-cervical nerves pass with respect to the vertebra.
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Below C7 each spinal nerve passes through the inferior notch of the corresponding vertebra.
Ex. T1 spinal nerve passes through the notch formed by the 1st and 2nd thoracic vertebra. |
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Where is the subarachnoid space and what does it contain?
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Subarachnoid space lies between the arachnoid and the pia.
Contains the CSF |
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Where is CSF formed?
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Choroid plexus of the lateral, 3rd, and 4th ventricles
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What is in the epidural space?
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Fat
Lymphatics Blood vessels |
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what are the boundaries of the epidural space?
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Foramen magnum- cranially
Sacrococcygeal ligament- caudally posterior longitudinal ligament- anteriorly ligamentum flavum and vertebral lamina- posteriorly vertebral pedicles- laterally |
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What is the maximal depth of the epidural space?
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about 6mm- midline at L2
4-5mm in the midthoracic region |
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Where does the blood supply of the spinal cord arise from?
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a single anterior
and 2 paired posterior spinal arteries |
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Where does the single anterior spinal artery arise?
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Originates from the vertebral artery.
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Where does the anterior spinal artery supply blood?
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Supplies the ventral (motor) portion of the spinal cord.
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Where does the largest anastamotic link to the anterior spinal artery come and what is the name?
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Radicularis magna or
artery of Adamkiewicz arises from the aorta in the lower thoracic or upper lumbar region. |
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The artery of Adamkiewicz is critical to the blood supply of what portion of the spinal cord?
Most commonly is it on the left or right? Where does it usually enter the vertebral canal (? interspace)? |
supply of the lower 2/3 of the spinal cord
most commonly on the left enters vertebral canal through the L1 interspace. |
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What would happen if there were damage to the artery of Adamkiewicz?
What surgical procedure may this happen? What neuraxial procedure may this happen? |
produce characteristic bilateral lower extremity motor loss otherwise known as anterior spinal artery syndrome.
Can happen on surgery of the aorta (aortic aneurysm resection) Can happen during epidural placement |
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What are the veins in the epidural space called?
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Venous plexus
or internal vertebral venous plexus |
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Where are the epidural venous plexus predominant?
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in the lateral epidural space
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Where do the epidural veins empty into and their path?
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empty into the azygos venous system which enters the chest, arches over the right lung, and empties into the superior vena cava
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List absolute contraindications to neuraxial anesthetic techniques
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1) patient refusal
2) infection at the site of planned needle puncture 3) elevated ICP 4) bleeding diathesis |
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Would you do a block on a patient with known bacteremia?
If so, what would need to be done prior to the block? |
Can do it
know that you may introduce infected blood and resulting epidural abscess or meningitis can occur Make sure appropriate antibiotic therapy is started and patient has a response to the therapy prior to performing the block |
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Why would one be cautious when administering neuraxial block to a pt with either Mitral stenosis, IHSS, or AS?
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these patients are intolerant of decreased SVR and although not a contraindication the block should be used and administered cautiously.
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Should you do neuraxial blocks on patients with either chronic back pain or multiple sclerosis?
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No causal relationship between exacerbation of the condition and neuraxial anesthesia but one wouldn't want to be responsible for exacerbation of pain and the block....so it is best avoided.
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The spinal cord extends to the 3rd lumbar vertebra in approximately what % of adults?
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2%
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When using the midline approach where do you make your needle placement with respect to the spinous process?
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Needle is inserted at the top margin of the lower spinous process of the selected interspace.
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What are the layers as the needle passes toward the subarachnoid space?
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Skin
Subcutaneous tissue supraspinous ligament interspinous ligament ligamentum flavum epidural space dura arachnoid |
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Where is the general insertion point of the needle for a paramedian approach?
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1cm lateral to midline
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With the paramedian technique which ligaments are bypassed?
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Supraspinous
and interspinous ligaments |
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What is the first resistance encountered when placing the needle with a paramedian approach?
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Ligamentum flavum
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Describe the Taylor approach and what it is used for.
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Paramedian technique to access the L5-S1 interspace.
Spinal needle passed from a point 1 cm caudad and 1 cm medial to the posterior superior iliac spine and advanced cephalad at a 55degree angle with a medial orientation based on the width of the sacrum |
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What is generally the widest interspace?
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L5-S1
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What do you do when you encounter blood tinged CSF?
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if it is initially blood tinged and then clears the spinal can be completed.
If it continues to flow the neele should be removed and inserted into a different interspace. Should blood-tinged CSF still persist at the new interspace the attempt to induce SAB should be terminated. |
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Distribution of local anesthetic in CSF is influenced principally by:
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1) baricity of solution
2) contour of spinal canal 3) position of patient in first few minutes after injection of LA into the Subarachnoid space |
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How does spinal anesthesia usually regress?
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From the highest dermatome in a caudad direction
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What are the 3 baricities of local anesthetic solutions?
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Isobaric
Hypobaric Hyperbaric These are based on density relative to the density of CSF |
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Why is baricity important?
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It determines the direction the LA will move after injection into the CSF
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What are the most commonly selected LA solutions for spinal anesthesia?
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Hyperbaric
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How is hyperbaric solution achieved?
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addition of dextrose (glucose)
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What is the principle advantage in utilizing hyperbaric solutions?
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ability to achieve greater cephalad spread of anesthesia
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What are 2 commercially available hyperbaric LA solutions?
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0.75% Bupivacaine with 8.25% glucose
5% Lidocaine with 7.5% glucose |
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what are 2 indications to use hypobaric local anesthesia?
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patient undergoing perineal procedures in the "prone jackknife" position
Hip arthroplasty where anesthetic can "float up" to the nondependent operative site |
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what solution would you use to dilute the local anesthetic into a hypobaric solution?
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sterile water
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What is a potential advantage of using isobaric local anesthetic?
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more profound motor block and more prolonged duration of action than achieved with equivalent hyperbaric local anesthetic solutions.
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What are 2 adjuvant agents frequently added to LA solutions to increase duration of spinal anesthesia?
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Epinephrine
[0.1-0.2 mg (which is 0.1-0.2 ml of a 1:1000 solution)] Phenylephrine [2-5 mg (which is 0.2-0.5 ml of a 1% solution) |
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When epi is added to which LA is prolongation of the block most profound?
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Tetracaine
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List in order of greatest to least the effect of LA on spinal cord blood flow.
Bupivacaine Tetracaine Lidocaine |
Tetracaine>Lidocaine>Bupivacaine
Tetracaine=intense vasodilation Lidocaine more modest Bupivacaine Decreases both spinal cord and dural blood flow |
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Adding epi to LIdocaine increases risk for ____?
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lidocaine neurotoxicity
TNS Transient neurologic symptoms |
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Adding epi to spinal chloroprocaine has been associated with________?
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flu-like side effects
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Adding epi to tetracaine has been associated with an increased risk for _______?
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TNS
Transient neurologic symptoms |
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Where in the spinal cord is the effect of added oioids mediated?
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Dorsal horn
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The use of spinal morphine (0.1-0.5 mg) can provide effective control of post op pain for how long?
Can these patients go home the same day? |
pain relief for about 24 hours
In hospial monitoring must be maintained d/t potential for respiratory depression. |
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Is Clonidine as effective as opioids in regional anesthesia?
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It is NOT as effective as opioids
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What potential augmentation to LA does Clonidine provide?
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Augments the sympatholytic and hypotensive effects of the local anesthetic.
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What is transient neurologic symptoms?
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pain and or dyesthesia in the back, buttocks, and lower extremities
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Define dyesthesia
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tactile hallucination
Damage is being done to the tissue when actually none is. |
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What are drugs used for short acting spinal anesthesia?
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60 mg Lidocaine
40-60 mg Chloroprocaine |
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What drugs are used for longer acting spinal anesthesia?
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Bupivacaine 0.75% w/ 8.25% dextrose for hyperbaric anesthesia
Tetracaine 1% plain |
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Does Tetracaine or bupivacaine produce more intense spinal sensory anesthesia?
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Bupivacaine
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Does tetracaine or bupivacaine produce more pronounced motor block?
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Tetracaine
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The level of a patient's sensory anesthesia can be determined by what exam?
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discriminate between sharpness as prodcued by a needle
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Does the sensory exceed the level of the sympathetic block?
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No- the sympathetic block exceeds the level of the sensory block
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What nerve roots are evaluated by asking the patient to dorsiflex the foot?
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S1-S2
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What nerve roots are evaluated by asking the patient to raise the knees?
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L2-3
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What nerve roots are evaluated by asking the patient to tense the abdominal rectus muscle?
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T6-T12
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What sensory level would you desire for a hemorrhoidectomy?
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S2-S5
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What sensory level would you desire for foot surgery?
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L2-L3 (knee)
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What sensory level would you desire for lower extremity surgery?
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L1-L3 (inguinal ligament)
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What sensory level would you desire for hip surgery, vaginal delivery, or a TURP?
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T10 (umbilicus)
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What sensory level would you desire for lower abdominal surgery such as an open appendectomy?
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T6-7 (xiphoid process)
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What sensory level would you desire for upper abdominal surgery such as for a Cesarean section?
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T4 (nipple)
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What is the significance of a spinal block to the C8 level- 5th digit on the hand?
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Cardioaccelerator fibers are blocked.
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What is the significance of a spinal block to T1-2 level of inner aspect of the arm and forearm?
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Some degree of cardioaccelerator fibers are blocked.
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What is the significance of a spinal block to the T4-T5 nipple level?
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Possibility of cardioaccelerator block
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What is the significance of a spinal block reaching the S1 level that of the outer side of the foot?
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Confirms a block of the most difficult root to anesthetize.
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What is the significance of a T10 umbilicus level of a spinal block?
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Sympathetic nervous system block limited to the legs
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If you have a failed spinal block and you decide to repeat the spinal block- how much anesthetic do you give?
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Assume the first injection was delivered into the subarachnoid space as intended, and the combination of the 2 doses should not exceed that considered reasonable as a single injection for spinal anesthesia.
Some would say give another full dose Some would say give 1/2 the dose. You'll have to determine this as you are making your patient assesment. |
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The sympathetic nervous system block typically exceeds the somatic sensory block by how many dermatomes?
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2-6
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Which are blocked first?
a) conduction block of small-diameter, unmyelinated sympathetic fibers b) conduction block of large diameter, myelinated fibers? |
a
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Why is there a decreased incidence of thromboembolic complications after hip surgery with spinal anesthesia?
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Decrease in systemic blood pressure
Reduction in peripheral venous pressure Increased bood flow to lower extremities after sympathetic nervous system block. |
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What is the mechanism of hypotension resulting from a sympathetic nervous system block?
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1) decrease venous return to the heart and decreased cardiac output
2) decreased systemic vascular resistance |
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What precaution is taken before the institution of spinal anesthesia to minimize the effects of venodilation from sympathetic nervous system block?
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Adequate hydration
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What is PDPH?
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consequence of a hole in dura resulting in loss of CSF faster than production rate
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When does pain from PDPH begin?
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12-48 hours after transgression of the dura
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What is the characteristic feature of PDPH?
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it's postural component.
intensifies with sitting or standing partially or completely relieved by recumbency |
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Where do patients usually feel the PDPH and how do they typically describe it?
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occipital or frontal (or both)
Described as dull or throbbing |
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PDPH stretching can cause visual disturbances (diplopia, blurred vision, photophobia, "spots") resulting from the stretch of which cranial nerve as the brain descends because of the loss of CSF?
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cranial nerve VI (Abducens)- innervate the extraoccular muscles
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Describe some conservative treatments for PDPH
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Bed rest
Fluids analgesics Caffeine (500 mg IV) |
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What is more definitive treatment for PDPH?
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Epidural blood patch
15-20ml of patients blood obtained aseptically injected into epidural space ner or below the site of puncture because there is preferential cephalad spread. |
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How long should a patient who has received an epidural blood patch remain supine?
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1 hour
relief of headache should be immediate |
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Describe total spinal or high spinal.
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Excessive sensory and motor anesthesia after spinal administration with a loss of consciousness
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What is treatment for a high spinal?
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maintenance of the airway and ventilation
support of circulation -sympathomimetics -IV fluid administration |
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What is a first symptom of hypotension sufficient to produce cerebral ischemia after spinal anesthesia that your patient may tell you about?
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Nausea
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Should you perform thoracic epidural placement in an anesthetized patient?
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NO
However it is standard practice to place caudal, lumbar, and even thoracic epidural catheters in children after induction of general anesthesia where the communication with the patient is not really a benefit but adds substantial risk |
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What is the most commonly used epidural needle?
What kind of tip does it have? |
Toughy
Blunt tip- so it can rest against the dura without penetration |
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Generally what is the depth of the epidural space from the skin in most patients?
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4-6cm
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What approach is the thoracic epidural usually placed?
a) Taylor b) Midline c) Paramedian |
c) paramedian approach
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Name 2 techniques to identify the epidural space.
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1) loss of resistance
2) hanging-drop technique |
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What is the epidural test dose of local anesthetic?
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3cc of 1.5% Lidocaine with epinephrine 1:200,000
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How far do you advance a continuous epidural catheter into the epidural space?
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3-5cm beyond the tip of the needle
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True/False
=never attempt to withdraw a catheter back through the needle because of shearing (transection) of the catheter may result with retention of the transected tip left in the epidural space |
true
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The dural sac extends beyond S2 in approximately what % of people?
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10%
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What are the 2 principle factors affecting spread of epidural anesthesia?
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Dose (volume times conentration)
Site of injection |
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1:200,000 epinephrine is
________mcg/ml? |
5mcg/ml
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__________ is an opioid that is lipohilic, rapidly absorbed into systemic circulation and exhibits little rostral spread.
a) Morphine b) Clonidine c) Fentanyl |
c) Fentanyl
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_________is an opioid that is hydrophilic, spreads rostrally within the CSF and can produce effective analgesia for thoracic surgery even when administered into the lumbar epidural space.
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Morphine
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Local anesthetics are (strong/weak) bases?
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Weak
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Local anesthetics exist largely in (ionic/ nonionic) form in commercial preparations?
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ionic
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Adding sodium bicarbonate to LA favors the
a) ionic form b) nonionic form c) polar form |
b) nonionic form
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Ionic form/ nonioinic form
of local anesthetic promotes more rapid onset of epidural anesthesia? |
nonionized form
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How much sodium bicarbonate is added to how much local anesthetic to alkalinize the solution?
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1ml of 8.4% sodium bicarbonate added to 10ml of a solution containing lidocaine or chloroprocaine.
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Do you add sodium bicarbonate to bupivacaine solution?
Why or why not? |
No- bupivacaine precipitates at alkaline pH
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List some disadvantages of sympathectomy.
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1)loss of body's compensatory mechanisms in response to surgical bleeding
2) risk for stroke 3) spinal cord ischemia 4) MI if Systemic BP is persistently low or dangerously low |
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When an epidural hematoma is suspected what do you do?
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Urgent performance of MRI
Recovery of motor function correlates inversely with the time until surgical decompression. |
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You have injected local anesthetic into the epidural space and now notice your patient has an unexpected dilated nonreactive pupil...what may have happened?
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migration of the catheter into the subarachnoid space.
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Subdural injection of LA produces what kind of block?
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unusual block characterized by patchy sensory anesthesia and often unilateral dominance.
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