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Nurse Practicum > Neuraxial Anesthesia > Flashcards

Neuraxial Anesthesia Flashcards

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1
Q

Neuraxial Anesthesia

A
  • can be used in combo with GA or alone or after for post-op analgesia
  • single dose or catheter for intermittent boluses or continuous infusion
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2
Q

Benefits of Neuraxial Anesthesia

A
  • In high risk pts may decrease risk of venous thrombosis, PE, cardiac comps, bleeding, resp depression, transfusion requirements, PNE, vascular graft occlusion
  • Post-op epidural analgesia may reduce mech vent need & time to extubation in abd or thoracic surgery pts
  • Epidural/spinals (regional anesthesia) for C-section has decreased mortality & morbidity compared to GA
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3
Q

Spinal Column General Anatomy

A

from foramen magnum to L1 in adults, L3 in children

Dura Mater + Arachnoid Mater usually stuck together
Subarachnoid space = CSF
Pia mater adherent to spinal cord

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4
Q

Filum Terminale

A

an extension of the Pia mater which attaches the end of the spinal cord (conus medullaris) to the coccyx

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5
Q

Spinal Vs. Epidural

A

spinal requires less medication = a dense sensory and motor blockade

epidural requires more = a differential blockade

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6
Q

Differential Blockade

A

sympathetic is most cephalad: 1-2 segments above sensory

motor is most caudal

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7
Q

Primary Site of Action for Neuraxial Anesthesia & Physiologic Response

A

the nerve root

results from inhibited sympathetic and unopposed parasympathetic

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8
Q

Posterior V Anterior Nerve Roots

A

Posterior: somatic & visceral sensation
Anterior: efferent motor & autonomic outflow

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9
Q

Nervous System Breakdown

A

CNS: brain & spinal cord

PNS –> autonomic –> SNS & PNS
PNS –> somatic –> sensory & motor

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10
Q

Sympathetic Nervous System

A

thoracolumbar - T1-L2
most preganglionic synapse with postganglionic in the paravertebral ganglia

stellate ganglion: inferior cervical + first thoracic

T1-T4 are cardiac accelerator fibers

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11
Q

massive sympathetic response

A

tachycardia, bronchodilation, dry mouth, diaphoresis

anatomically & functionally more systemic

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12
Q

parasympathetic

A

craniosacral outflow
CN 3: midbrain
CN 7: pons
CN 9 & 10: medulla

Sacral segments S2, S3, S4

more selective & localized

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13
Q

massive parasympathetic response

A

bronchoconstriction (wheezing), bradycardia, miosis, vomitting, defecating, seizing

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14
Q

BP Effects of Neuraxial Anesthesia

A

varying level of decreased HR/BP

Hypotension: vasomotor tone is mostly determined by T5-L1 sympathetic fibers which innervating arterial & venous smooth muscle

  • vasodilation of veins = reduced preload & CO
  • vasodilation of arteries = impaired compensatory vasoconstriction
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15
Q

HR effects of neuraxial anesthesia

A

bradycardia.
a high blockade may inhibit the cardiac accelerator fibers at T1-T4

there is unopposed vagal tone which can = sudden cardiac arrest

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16
Q

Treatment of hypotension/bradycardia r/t neuraxial anesthesia

A

first line: ephedrine
glycopyrolate or atropine can be used for sympathetic bradycardia

IVF bolus 5-10ml/kg IF appropriate renal & cardiac function

head down = autotransfusion

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17
Q

Cephalad block effect on hemodynamic instability

A

more cephalad block = more hemodynamic instability

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18
Q

Pulmonary Effects of Neuraxial Anesthesia

A

usually minimal (phrenic nerve - innervating diaphragm - at C3-5)

severe CLD may require accessory muscles to breathe - these can be inhibited

post-op thoracic epidural analgesia in high risk patients is BENEFICIAL - decreased risk of PNE & respiratory failure - improves Oxygenation - decreases duration of mech vent

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19
Q

GI effects

A

unopposed vagal stim = small contracted gut & increased peristalsis- helpful for intestinal surgery

post-op epidural analgesia = decreased opioid need = quicker return of gut function

hepatic blood flow reduced with any type of anesthesia

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20
Q

GU effects

A

renal blood flow maintained

urinary retention - impairment of PNS & SNS - intraop catheter OR careful IVF admin & monitor for bladder distention

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21
Q

Major Indication for Neuraxial Blocks

A

Breast/thoracic/major abd - epidural + GA

Hip/knee replacement - can do spinal/epidrual alone

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22
Q

Absolute Contraindications to Neuraxial anesthesia

A 
coagulation abnormalities
severe hypovolemia 
increased ICP 
infection at injection site
thrombolytic/fibrinolytic therapy
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23
Q

Relative Contraindications to Neuraxial anesthesia

A 
aortic/mitral stenosis 
severe LF outflow obstruction
sepsis
severe spinal deformity
pre-existing neurological defects
uncooperative pt
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24
Q

Anticoagulants + Neuraxial Blockade

A

bleeding in the closed space of spinal canal = hematoma = pressure on spinal cord or caudal equina = infarction or ischemia = paraplegia or severe neurologic injury

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25
Q

Warfarin

A

interval from last dose to placement/removal: 4-5 days

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26
Q

Heparin

A

interval from last dose to placement/removal:

IV OR SubQ: 4-6 hrs & verify aPTT

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27
Q

Clopidogrel

A

interval from last dose to placement/removal: 5-7 days

interval from placement/removal to next dose:

  • with loading dose: 6 hrs
  • without: immediate
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28
Q

Argatroban

A

thrombin inhibitor

AVOID neuraxial anesthesia

29
Q

Aspirin & NSAIDS

A

okay to continue

30
Q

Prominent Landmarks

A

T7 - level with inferior tip of scapula
L4 - tip of iliac crests - Tuffiers Line
L4-L5: largest intervertebral space
S2: bw posterior superior iliac spine

31
Q

thoracic vs cervical/lumbar vertebrae

A

thoracic spinous processes point much more caudal & therefore require a greater cephalad angle

32
Q

Passing of Needle layers

A

skin - subQ tissue - muscle - SSL - ISL - ligament flavum - epidural space - dura mater - subdural space - arachnoid mater - subarachnoid space

33
Q

Midline Approach Steps

A
  1. palpate & identify space
  2. clean - set up sterile
  3. skin wheel with LA with 25g needle
  4. introducer slightly above caudal spinous process with 10 degree cephalad angle
  5. remove stylet: CSF should drip
  6. attach syringe - gently aspirate - slowly inject 0.5ml/s
  7. complete, aspirate again to check placement
  8. remove all together
  9. assess level of blockade by testing temp or pin prick sensation
34
Q

Paramedian approach

A

can bypass calcified ligaments
1 cm lateral and directed toward middle of the interspace
ligamentum flavum will be first resistance met

35
Q

Dermatomes

A 
C5: clavicles
C6: thumb
C8: ring & little fingers
T4: nipples
T10: umbilicus 
S2, 3, 4: perineum 
L1,2,3,4: anterior & inner surfaces of lower limbs
36
Q

Spinal Needles & Catheters

A

sharp cutting tip: Quincke
blunt tip: Whitacre
25g

smaller gauge + blunt tip = reduced risk of PDPH

37
Q

Factors influencing the level of a spinal block

A

baricity
positioning
drug dosage - larger dose = more cephalad
site of injection - more cephalad = more cephalad block

38
Q

Baricity

A

migration depends on its density relative to CSF (1.003)
hyperbaric = denser/heavier
hypobaric = lighter/less dense

39
Q

Positioning + baricity

A

Head up: hyperbaric settles caudal & hypobaric migrates cephalad

lateral: hyperbaric will have greater effect on the dependent side & hyperbaric will have a greater effect on the non-dependent side

isobaric tends to remain AT the level of injection

40
Q

Baricity Supine position

A

anatomy will limit migration
T4-T7 is the most dependent area
T4 is the apex of the thoracolumbar curve - limiting spread

41
Q

other factors affecting height of block

A

pt height, age, intraabd pressure, direction of bevel on injection, anatomy

42
Q

spinal additives

A

all are preservative free

vasoconstrictors (A agonists & epi) & opioids prolong duration and/or improve quality

43
Q

Epidural Anesthesia General

A

wider range of applications
can be cervial, thoracic, lumbar
surgical anesthesia, OB, post-op pain, chronic pain
single shot, boluses, or continuous
motor block can range from none to complete
slower onset (10-20 min)
less dense - segmental block
can provide analgesia without motor blockade

44
Q

segmental block

A

a band of blockade at certain nerve roots, leaves those above/below unblocked

45
Q

Epidural Needles

A 
16-18g
blunt bevel 
15-30 degree gentle curve at tip - helps to push away dura after passing through the ligament flavum
Tuohy Needle
avg adult passes 4-6 cm 
obese pt may pass 8 cm
46
Q

checking epidural placement

A

aspirate - confirm absence of blood
test dose - 3ml of LA with 5mcg/ml epidural
a 30 BPM increase in HR in 30s lasting 30s may mean you are intravascular

immediate profound motor block may mean you are intrathecal

47
Q

Factors Affecting Level of Epidural Block

A

Drug Vol: 1-2ml per segment to be blocked
- to get T4 from L4-L5 would need 12-24ml
Pt height: shorter may require less per segment, closer to.1

interspace decreases with age - require less

additives usually help quality more than prolonging duration

48
Q

Spinal Analgesia patho

A

diffuses into substantia gelatinous (Rexed lamina II)
unites with opioid receptors of primary pain afferent
Mu-1, Mu-2, kappa, delta
spinal opioid analgesia primarily Mu-2
increased frequency of pruritus & urinary retention

49
Q

Intrathecal Opioid

A

diffuses out of intrathecal space slowly
onset of analgesia is slow, duration is prolonged
early ventilatory depression does not occur - systemic uptake is minimal
rostral speed = late resp depression (6-12hrs after)

50
Q

Epidural Opioid

A

onset slow, duration prolonged
systemic uptake is greater here = early ventilatory depression
late depression also - rostral spread

51
Q

epidural placement

A

sudden loss of resistance as you pass the ligamentum flavum

52
Q

Hitting bone

A

superficially - needle hitting a lower spinous process
deeper - midline - may be hitting an upper spinous proccess

deeper - medial - may be hitting a lamina

53
Q

pain or persistent paresthesias on injection of drugs

A

withdraw needle and re-direct

54
Q

Caudal epidural anesthesia

A

usually for pends in combo with GA for procedures beneath umbillicus

penetration of sacrococcygeal ligament covering the sacral hiatus (the unfused S4/S5) - groove above coccyx bw sacral Cornu (bony prominences)

55
Q

three areas of neuraxial complications

A

adverse/exaggerated physiological responses

catheter placement/injury

drug toxicity - SLAT or caudal equina syndrome

56
Q

Adverse/Exaggerated physiologic responses

A 
urinary retention 
high block
total spinal
cardiac arrest 
horner syndrome
57
Q

catheter placement complications/injury

A 
PDPH
backache
neural injury 
bleeding- epidural hematoma
incorrect placement - inadequate anesthesia, infection, inadvertent intravascular or intrathecal block
58
Q

PDPH

A

occurs w/I 72 hrs
intracranial hypotension from leak of CSF = sagging of brain & supporting structures
S/S: HA, N/V, stiff neck, visual changes

Risk Factors: pregnancy, female, young age, low BMI, cutting needle, large gauge

Tx: rest, blood patch, caffeine, lie flat

59
Q

High/Total Spinal

A 
rapid ascending sympathetic/sensory/motor block 
bradycardia
hypotension 
dyspnea
difficulty swallowing

can progress to unconsciousness & respiratory depression

60
Q

Spinal-Epidural Hematoma

A

progressive motor & sensory block with bladder/bowel dysfunction

61
Q

Lidocaine

A 
amide -
4.5mg/kg -- with epi: max 7mg/kg OR 500mg
fast onset 
DOA: 1-2 hr  
intermediate potency
62
Q

Bupivicaine

A

amide
2mg/kg – with epi: max 3 mg/kg OR 200mg
SLOW onset

DOW: 3-10 hr - LONG acting

has a high affinity for cardiac proteins - can produce cardiac toxicity

63
Q

Mepivacaine

A

amide
4.5mg/kg – with epi: 7mg/kg OR 500 mg
intermediate onset
DOA: 2-4hrs

64
Q

Procaine

A

Ester
7mg/kg
spinal primarily
SLOW onset

DOA: 1-2hrs

65
Q

Chloroprocaine

A

ester
11mg/kg – with epi: 14mg/kg OR 1g
FAST onset

DOA: 30min-1hr

66
Q

MOA of LAs

A

produce a reversible blockade of conduction of electrical impulses at the alpha subunit of sodium channels

ONSET: pain - temp - touch - pressure - motor

67
Q

Metabolism of LAs

A

esters - hydrolysis via tissue & plasma cholinesterase

amide - liver via CYP system

68
Q

LA Properties

A

all are weak bases
pKa: the pH at which there is an equal fraction of ionized & non-ionized

lower pKa = greater non-ionized fraction = faster onset

once in the nerve the charged IONIZED fraction binds the Na++ channels

69
Q

DOA of LA

A

more lipid soluble = longer
higher potency = longer
more protein bound = longer

Nurse Practicum (2 decks)

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