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Principles 2 > Spinal Anesthesia (pt 1) > Flashcards

Spinal Anesthesia (pt 1) Flashcards

1
Q

What is Spinal Anesthesia?

A

Reversible chemical blockade of neuronal transmission by a local anesthetic injected into the Cerebral Spinal Fluid (CSF).

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2
Q

Where do the actions of spinal anesthesia occur?

A

On anterior and posterior nerve roots as they pass through the CSF to peripheral nerves
-To a lesser extent, on the spinal cord itself
-Temporary interruption of sensory, autonomic, and motor nerve fibers renders the patient insensitive to surgical stimulation.

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3
Q

Immediately after spinal nerves exit via the intervertebral foramen, they divide into _____ ?

A

Ventral and Dorsal Primary Rami.
-DPR: supply skin and muscles of the back
-VPR: supply anterior lateral muscles, skin of neck and trunk and limbs.
Both also contribute a small nerve to sympathetic ganglia.
Joint together eventually to form plexi in a specific region

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4
Q

What are Dermatomes?

A

Areas of the skin that are innervated by a specific nerve root.
-Help to determine where a block is working
-Help to understand where injury/pain is coming from

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5
Q

What nerve forms the dermatomes of the face?

A

Ophthalmic, Maxillary, and Mandibular divisions of the Trigeminal Nerve

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6
Q

What dermatome level is C4?

A

Clavicle

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7
Q

What dermatome level is C8?

A

Little finger

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8
Q

What dermatome level is T4?

A

Nipple

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9
Q

What dermatome level is T6 - T8?

A

Xiphoid, lower rib cage

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10
Q

What dermatome level is T10?

A

Umbilicus

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11
Q

Above ___ is a high spinal, which causes what symptoms?

A

T2
-Severe hypotension, dyspnea, respiratory arrest

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12
Q

What dermatome level is T12?

A

Last rib

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13
Q

Explain how/why Differential Nerve Blockade works?

A

The anatomy of the nerve root accounts for differential sensitivity of nerve types to local anesthetic.
-Small diameter nerve fibers are found close to the nerve root surface (Shorter diffusion path of LA)
-Large diameter nerve fibers are found deep to the nerve bundle (longer diffusion path of LA)

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14
Q

Which fibers are more sensitive to local anesthetic blockade?

A

Large myelinated fibers are more sensitive to local anesthetic blockade than smaller myelinated and unmyelinated fibers.

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15
Q

What order are fibers blocked in (A, B, C, etc)?

A

1) B Fibers
2) C Fibers
3) A Delta Fibers
4) Larger A Gamma (muscle spindles), A Beta (Touch, pressure)
5) A Alpha (Proprioception, motor) fibers are last.

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16
Q

What fibers are found at the outside of the root?

A

B Fibers
-Preganglionic sympathetic efferents
-Autonomics. This is why the first thing you’ll see with a block is a drop in BP.

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17
Q

What fibers are found immediately inferior to B Fibers?

A

C and A-Delta fibers
-C: Pain
-A Delta: Pain, temperature
-Pain, temperature, and touch afferents
-Post ganglionic sympathetics

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18
Q

What is the order of sensitivity with large myelinated to unmyelinated?

A

Large Myelinated > Smaller myelinated > unmyelinated
-Once it gets to them, the large myelinated fibers are very sensitive

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19
Q

What are other factors that contribute to a differential nerve block?

A

-Myelination
-Nodes of Ranvier
-Size of fibers
-Location depth
-Na and K Channels on each nerve

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20
Q

Sympathetic blockade (BP changes is 1st sign) is usually ___ segments higher than ____ blockade (temp, light touch, pain), which is usually ____ or greater segments before ____ blockade.

A

Sympathetic blockade (BP changes is 1st sign) is usually 2 segments higher than Sensory blockade (temp, light touch, pain), which is usually 2 or greater segments before Motor blockade.

-Sometimes, sympathetics can go up to 6 segments higher (bad).
-Could end up having a bigger block than what you thought.

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21
Q

How do you assess your patient for sensory block?

A

-Loss of temperature sensation from cool alcohol swab is most sensitive indicator of initial onset of sensory block
-Sharp/broken tongue depressor is most accurate for overall sensory block
-Decrease in BP may be first sign it’s working (B fibers)
-Loss of sensation to cold (alcohol swab) occurs before sharp and at a higher level (C, A-Delta)
-Initial motor block is myelinated A Beta & A Gamma fibers
-Profound block is A Alpha

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22
Q

What are the 2 most important factors that impact the Spinal (Intrathecal) Level?

A

-Baricity
-Patient position

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23
Q

How do you determine baricity?

A

In relation to the specific gravity of CSF (1.004-1.008).
-Hypobaric: Less baricity than CSF (floats up)
-Isobaric: stays where it is injected
-Hyperbaric: most frequently used. Sinks

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24
Q

What are the highest points of the spinal curve?

A

-Cervical & Lumbar Lordosis
-C3 and L3 high points

25
Q

What are the lowest points of the spinal curve?

A

-Thoracic and Sacral Kyphosis
-T6 and S2 low points

26
Q

What other factors affect the height of a spinal block?

A

-Age
-Height (if very tall, can increase dose as more distance to travel)
-Weight: Obese/Pregnant have decreased intrathecal space (less dose)
-Technique of injection: site, direction of needle/bevel, rate of injection (barbotage) - controversial
-Spinal Fluid (rate of circulation, volume, pressure - coughing and straining)
-LA: Amount, concentration, volume, vasoconstrictors (slow down how fast it is absorbed)

MOST IMPORTANT is baricity and patient position!!!!

27
Q

How does age impact your height of spinal block?

A

-Ligamentum Flavum gets tougher
-Intrathecal space is more compressed
-Higher spread of Local Anesthetic

28
Q

What is the baricity of CSF?

A

1

29
Q

What is the baricity of hypobaric solutions?

A

-Tetracaine 0.33% / water = 0.9977
-Lidocaine 0.5% / water = 0.9985

30
Q

What is the baricity of isobaric solutions?

A

-Tetracaine 0.5% / 50% CSF = 0.9995
-Lidocaine 2% / water = 1.003
-Bupivicaine 0.5% / water = 0.999

31
Q

What is the baricity of hyperbaric solutions?

A

-Tetracaine 0.5% / 5% dextrose = 1.0133
-Lidocaine 5% / 7.5% dextrose = 1.0265
-Bupivicaine 0.5% / 8% dextrose = 1.0207
-Bupivicaine 0.75% / 8% dextrose = 1.0227

32
Q

What is specific gravity?

A

The ratio of a density of a substance to the density of water
-Affected by proteins, glucose, uremia
-temperature can affect it
-Spec grav of CSF = 1.0069

33
Q

What is the definition of baricity?

A

The resting position of 2 fluids with differing specific gravities.

34
Q

What is the primary objective of neuraxial anesthesia? **

A

-To block afferent fibers located in the Dorsal Roots
-Motor and sympathetic fibers are close and they get blocked as they pass through the ventral root.

35
Q

Why is Lidocaine 5% not used anymore for Spinal Anesthesia (SAB)?

A

-Potential to cause transient neurological syndrome (TNS)
-Can cause Cauda Equina syndrome (permanent)

36
Q

Which is the most cardiotoxic local anesthetic?

A

Bupivicaine
-May need lipids to reverse

37
Q

List some common preservatives added to local anesthetics.

A

-Parabens (high allergy/anaphylaxis potential)
-Sulfites (neurotoxic)
-EDTA (muscle pain, can cause tetany in paraspinous muscles)

38
Q

T/F: it’s ok to use preservative containing, multi-use vials for spinals.

A

FALSE
-Want preservative free, single dose vials for anything going in the spine.
-Multi-use can be used for PNB, but not for spinals.

39
Q

What is the MOA of local anesthetics?

A

-Limit the sodium channels and stop the propagation of a nerve impulse.
-Small amounts act directly on the spinal cord itself by way of diffusion through the pia mater (slow process)
-LA can find its way to the cord via the Virchow-Robin Spaces

40
Q

What are Virchow-Robin Spaces?

A

Insertion sites of tiny blood vessels on the spinal cord where local anesthetics can get around the sides of them and act directly on the cord.

41
Q

The more _____ soluble the drug, the more it can penetrate the membrane and get to the roots (site of action).

A

Lipid soluble.

42
Q

Why is Epinephrine added to local anesthetics?

A

-Alpha 1 agonist
-Produces direct analgesia when placed on the cord
-Increases duration of LA by causing constriction of blood vessels (slows absorption of local)
-Usual dose is 0.1-0.2 mL of Epi 1:1000 for spinal (Epi Wash)

43
Q

Epinephrine has the greatest effect on which local anesthetic?

A

Greatest effect on Tetracaine

Then Lidocaine, then Bupivicaine.

44
Q

What is the dose of Phenylephrine added to Spinals?

A

-Pure Alpha 1 Agonist
-0.5 - 2 mg

45
Q

What is the purpose of adding Clonidine to Local Anesthetics?

A

-Alpha 2 Agonist Activity
-High lipid solubility
-Local anesthetic effects
-Prolongs DOA

46
Q

Why is NaHCO3 added to local anesthetics?

A

To increase the pH to decrease the onset (quicker)

47
Q

Describe Opioids added to a Spinal

A

-Stimulate opioid receptors in the brainstem (Substantia Gelatinosa) and Spinal Cord
-Mu receptors are responsive to Morphine, Meperidine, Sufentanil, Fentanyl, and Alfentanil
-Mu 2 receptors are responsible for dec HR, RR, Euphoria
-SEs: N/V, itching, urinary retention

48
Q

What is the opioid reversal?

A

Naloxone - competitive antagonist

49
Q

What is the number 1 complaint of opioid additives to Local Anesthetics?

A

Itching (especially in OB)

50
Q

Why is Fentanyl widely used as an additive to local anesthetics?

A

-It adheres to lipoproteins in the spinal cord due to its high lipid solubility
-Less drug available to diffuse to respiratory centers
-Dose: 10-25 mcg
-Onset: 5-10 min
-DOA: 2-4 hours
-Can be used in combo with morphine

51
Q

What is important to know regarding Morphine added to local anesthetics?

A

-Use preservative free for spinals!
-Hydrophilic and not highly bound to spinal cord, so it moves around (can hit respiratory centers)
-Be very careful - administer only if patient is being monitored
-Onset: 60-90 min
-DOA: 6-8 hours
-Dose: 0.1 - 0.5 mg (spinal)
-Won’t be able to give more opioids for breakthrough pain
-Caution with risk of delayed respiratory depression**

52
Q

For Upper abdominal surgery, what Dermatome level do you want to block?

A

T4

53
Q

For intestinal, gyn, and urologic surgeries, what Dermatome level do you want to block?

A

T6

54
Q

For a TURP, what Dermatome level do you want to block?

A

T10

55
Q

For a vaginal delivery or hip surgery, what Dermatome level do you want to block?

A

T10

56
Q

For thigh surgery and lower leg amputations, what Dermatome level do you want to block?

A

L1

57
Q

For Foot and Ankle surgery, what Dermatome level do you want to block?

A

L2

58
Q

For perineal and anal surgery, what Dermatome level do you want to block?

A

S2-S5 (saddle block)

Principles 2 (45 decks)

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