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N931 Advanced Principles of Anesthesia I > Spinal Anesthesia > Flashcards

Spinal Anesthesia Flashcards

1
Q

what is a spinal anesthetic?

A
  • reversible chemical blockade of neuronal transmission produced by the injection of a local anesthetic into the CSF
  • aka = subarachnoid block OR intrathecal block
  • result = temporary interruption of autonomic, sensory and motor nerve fiber transmission
  • takes place at the ventral and dorsal nerve roots
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2
Q

first spinal anesthetic

A
  • August Bier
  • 1898
  • documented first spinal headache and N/V
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3
Q

advantages of spinal anesthesia

A
  • ideal for procedures from lower abdomen and caudal
  • simple and versatile - block distribution without adjunct and distribution can be controlled
  • reduces - surgical stress, blood loss, risk of DVT
  • can provide post-op analgesia
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4
Q

spinal analgesia decreases incidence of

A
  • PONV
  • sedation
  • cognitive impairment
  • surgical pain
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5
Q

disadvantages of spinal anesthesia

A
  • sympathetic blockade occurs 100% of the time
  • block may last longer than procedure
  • PDPH
  • urinary retention
  • regional takes “too much time”
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6
Q

which procedures is spinal anesthesia beneficial for?

A
  • lower extremities
  • lower abdomen
  • also certain comorbidities like pulmonary disease
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7
Q

indications for spinal anesthesia

A
  • full stomach - vomiting and aspiration less likely than with general anesthesia
  • difficult airway
  • minimal metabolic impact - liver disease, kidney disease, diabetes
  • reduction ins systemic blood pressure - decreases risk of DVT and blood loss
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8
Q

absolute contraindications

A
  • patient refusal
  • increased ICP
  • severe aortic or mitral valve stenosis
  • coagulopathy or bleeding diathesis
  • severe hypovolemia
  • infection at injection site
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9
Q

valve area for severe AS

A

<1 cm2

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10
Q

valve area for critical AS

A

<0.7 cm2

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11
Q

considerations and relative contraindications for spinal

A

same as for epidural

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12
Q

dural puncture usual site

A
  • occur anywhere from L2 to S1

- most common is L3-4 interspace

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13
Q

patient positioning for spinal

A

same as for epidural
angry cat or shrimp
flexed to open up the interspinous spaces

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14
Q

specific gravity

A

density of a substance as compared to the density of water

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15
Q

SG water

A

1.0

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16
Q

SG CSF

A

1.003-1.009

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17
Q

baricity

A
  • resting position of two fluids with different specific gravity when mixed in a single container
  • helps determine the potential spread of LA in the subarachnoid space
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18
Q

isobaric

A
  • LA same baricity as CSF

- normal saline or CSF (mixed in this)

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19
Q

hyperbaric

A
  • LA is heavier (more dense or higher baricity) than CSF

- mixed with dextrose

20
Q

hypobaric

A
  • LA is lighter (less dense or lower baricity) than CSF

- mixed with sterile water

21
Q

most important factors that determine LA level

A
  • baricity
  • position of the patient
  • drug dosage
  • site of injection
22
Q

other factors that determine LA level

A
  • patient height (short people need less)
  • pregnanacy (epidural veins engorged, so need less because greater spread)
  • age
  • CSF volume
  • curvature of the spine
  • drug volume
  • intra-abdominal pressure
  • needle direction
23
Q

where do hyperbaric solutions settle

A
  • the most dependent area of the spine

- in a supine patient this is T4-T8

24
Q

spinal procedure

A
  • prepare patient, talk them through it
  • position patient
  • sterile procedure
  • cleanse injection site with CHG
  • apply sterile drape
  • straddle selected interspace with middle and index fingers of non-dominant hand
  • raise small intradermal skin wheal of LA with 25-27G
  • small spinal needle (25 G) requires introducer, larger needles (20-22G) do not
  • pass spinal needle through introducer
  • advance through posterior ligaments
  • you may feel two pops (flavum and dura)
  • stop advancing the needle and secure the hub with your hand against the patient’s back
  • remove stylet and observe flow of clear CSF
  • connect syringe containing LA
  • aspirate small volume of CSF to confirm placement
  • observe swirl
  • inject entire predetermined volume of drug in one smooth motion
  • immediately remove the syringe, needle and introducer unit in one smooth motion
25
Q

introducer

A
  • placed before the spinal needle through the skin wheal int he midline of the lower third of the interspace
  • serves to guide the spinal needle, provides stability and support for smaller gauge needles
26
Q

what do you do if you want a bilateral spinal block?

A
  • return patient to supine position immediately to get even spread
  • slightly elevate the head
27
Q

what do you do if you want a unilateral spinal block?

A
  • leave patient in the lateral position for at least 3 min prior to returning to the supine position
  • slightly elevate the patient’s head
28
Q

cutting needle

A
  • designed to cut through tissue
  • want to insert this with the bevel to the side so you don’t puncture anything or cause dural trauma
  • quinke needle
29
Q

pencil point needle

A
  • designed to separate tissue not cut it
  • less incidence of dural trauma
  • whitacre needle
30
Q

absence of CSF with spinal

A
  • reinsert stylet
  • slowly advance 1-2 mm
  • attempt to aspirate CSF
  • repeat steps until CSF seen
  • common practice is to advance needle an additional mm after puncture to ensure complete puncture of dura
  • especially impt with pencil point needles - more common with these due to where the hole is in relation to the bevel
31
Q

what to do if you suspect you traversed the dura

A
  • remove the stylet and attach syringe
  • gently aspirate as you slowly withdraw your needle
  • may get CSF as needle tip is withdrawn into the subarachnoid space
  • increased risk of PDPH
32
Q

frank blood CSF

A
  • does not clear, the needle tip is likely in an epidural vein
  • withdraw and reposition
33
Q

blood-tinged CSF

A

allow CSF to flow for several seconds it should become clear; when it does inject the medication

34
Q

saddle block

A
  • S2-S5
  • surgery limited to perineum, perianal region or genitalia
  • little autonomic effect
35
Q

low spinal

A
  • T 10
  • low abdominal procedures and lower extremity vascular and orthopedic procedures
  • block lower lumbar and sacral roots
36
Q

most common level

A
  • T4
  • remember this is where the cardioaccelerator fibers are located
  • abdominal and lower extremity procedures
37
Q

high spinal

A
  • C8
  • block higher than T2
  • bad because patient will not be able to maintain ventilation
  • must intubate and take control of their airway
38
Q

paramedian approach

A
  • useful when patient cannot flex spine (hx spine surgery, RA, or hip/upper leg trauma)
  • skin wheal 1 cm lateral and 1 cm caudal to spinous process
  • advance needle toward midline
  • needle passes through paraspinous muscles to ligamentum
  • does NOT pass through supraspinous or intraspinous
39
Q

lumbosacral approach

A
  • “taylor” approach
  • modified paramedian approach
  • uses L5-S1 interspace
  • identify posterior superior iliac spine
  • make a skin wheal 1 cm medial and 1 cm caudal to the spine
  • needle insertion is at a 45-55 degree angle medial and cephalad to the dorsal surface of the sacrum toward the midline of the lumbosacral foramen
40
Q

continuous spinal

A

provides prolonged surgical anesthesia and post-op pain management

  • dura punctured with a 17G epidural needle
  • epidural cath passed through the dura into the subarachnoid space
  • small incremental doses of local are given until desired level
  • small, slow doses slow onset of hypotension
  • total dose to achieve desired level is the same
  • consider using when a wet tap occurs when placing an epidural
41
Q

epi for spinals

A
  • alpha 1 agonist
  • 0.1-0.2 mL of 1:1000 can be added to LA to prolong DOA
  • greatest effect with tetracaine
42
Q

phenylephrine for spinals

A
  • pure alpha adrenergric agonist slightly more effective than epi
  • 0.05-0.2 mL of 1% solution (0.5-2 mg) added to LA
  • greatest effect with tetracaine
43
Q

clonidine for spinals

A
  • NOT a vasoconstrictor
  • selective alpha 2 agonist
  • used when epi is contraindicated
  • when mixed with lido or bupiv has synergistic effects
  • central action appears to help with tourniquet pain
44
Q

intrathecal opioids

A
  • combo of preservative free opioids and LAs provides better analgesia than either one alone
  • most commonly used = fentanyl and morphine
45
Q

spinal fentanyl

A
  • high lipid solubility
  • binds directly to lipid elements of spinal cord
  • less drug available to diffuse systemically
  • provides PROFOUND analgesia
  • dose 12.5-25 mcg mixed with LA
  • onset 5-10 min
  • DOA 2-4 hrs
46
Q

spinal morphine

A
  • highly polarized, not very lipid soluble
  • drifts freely in CSF
  • provides profound analgesia
  • dose 0.1-0.25 mg mixed with LA
  • onset 60-90 min
  • DOA 24 hours
47
Q

AE of spinal morphine

A
  • itching
  • urinary retention
  • delayed resp depression - in approximately 6-8 hours will risk to respiratory center

N931 Advanced Principles of Anesthesia I (19 decks)

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