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LA 1 And 2 Flashcards

1
Q

Duration of anesthesia of PNB is dependent on

A

Type of block (uptake)

Drug used

Concentration

Adjuncts

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2
Q

Onset of PNB

Can take up to _____ to determine if block failed

A

10 minute onset
- 15 for Ropivacaine and Bupivacaine

Up to 30 minutes to determine if failed

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3
Q

Most single shot blocks _____ duration when combined with adjunct

A

16-24 hours

Decadron or epinephrine

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4
Q

Which is longer?

Analgesic time or surgical anesthetic time

A

Analgesic time much longer

Motor block will wear off but analgesia will continue

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5
Q

3 reasons for rescue blocks

Done when primary block

A
  • failed or has nerve sparing properties
  • ineffective in providing analgesia or doesn’t cover appropriate dermatome
  • duration of LA has been exceeded
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6
Q

If primary block has failed or has nerve sparing properties

A

Supplemental distal blocks

Redo primary block targeting location of missed nerves

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7
Q

Primary block is ineffective in providing analgesia or doesn’t cover appropriate dermatome

A

Surgeon operated on unanticipated area

Pain originates outside block coverage

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8
Q

When duration of LA has been exceeded

A

Usually at 16-24 hour mark when pain is still moderate-severe in nature

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9
Q

Rescue blocks are done by

A

Single shot

Single shot with catheter placement

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10
Q

Uptake of LA based on Regional Anesthetic Technique

Highest blood concentration to lowest

A 
IV
Tracheal
Intercostal
Caudal
Paracervical
Epidural
Brachial
Sciatic
Subcutaneous

(In Time I Can Please Everyone But Sally and Susan)

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11
Q

Pathophysiology of LAST

A

LA affect SNS and PNS

Profound arterial vasodilation and smooth muscle relaxation

Slows rate of depolarization, blocking fast Na channels

Very high doses dampen SA pm cells = bradycardia and sinus arrest

Dose dependent inotropic depression from negative modulation of Ca release from SR

Hypercapnia, acidosis, hypoxia increase negative inotropic and chronotropic effects of LA

BB, Ca channel blockers, and dig decrease threshold for cardiac toxicity

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12
Q

3 classes of drugs that decrease the threshold for cardiac toxicity

A

Beta blockers

Calcium channel blockers

Digoxin

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13
Q

LA with Lower safety margin and resuscitation if more difficult in event of LAST

A

Bupivacaine

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14
Q

LA that accounts for significant portion of LAST events

A

Lidocaine

Ropivacaine

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15
Q

4 things that are more predictive of high plasma levels of LA than body weight or BMI

A

Block site

Total LA dose

Test dosing

Pt comorbidities

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16
Q

7 events in LA toxicity

First to last

A

Drowsiness

Parentheses in mouth and tongue

Tinnitus, auditory hallucination

Muscular spasm

Seizure

Coma

Respiratory arrest

Cardiac arrest

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17
Q

Systemic intoxication by LA

Cardiocirculatory increasing degree of intoxication

A

HTN, tachycardia

Bradycardia, extrasystoles, hypotension

Asystole

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18
Q

Cerebral systemic intoxication s/s by degree of intoxication

A

Psychically “abnormal”

Confusion, dizziness, tinnitus, metallic taste

Seizure

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19
Q

Bupivacaine, levobupivacaine, ropivacaine

Which requires lower dose for toxic effects of LA

A

Bupivacaine

Levobupivacaine

Ropivacaine

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20
Q

Systemic presentations of LAST

CNS only

CV only

CNS and CV

A

CNS only 43%

CV only 24%

CNS and CV 33%

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21
Q

Spectrum of CV presentations with LAST

A

Dysrhythmia 34%

Conduction delay 27%

Cardiac arrest 23%

Bradycardia/hypotension 16%

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22
Q

Spectrum of CNS presentations of LAST

A

Seizure 47%

Loss of consciousness 36%

Prodromes 11%

Agitation 6%

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23
Q

The changing slop of trend lines suggest that contemporary LAST presentations are becoming

A

More delayed as compared with previous years

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24
Q

Due to the variability in presentation of LAST pt should be monitored for at least

A

30 minutes after injection

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25
Immediate (<60sec) presentation of LAST suggests
IV injection of LA with direct access to brain
26
Presentation of LAST delayed 1-5 minutes suggests
Intermittent IV injection, lower extremity injection, or delayed tissue absorption
27
4 basic steps of treatment of LAST
Get help Initial focus - airway mgmt - HYPERVENTILATE - seizure suppression - Alert nearest facility with CPB Mgmt of cardiac arrhythmia - BLS and ACLS - avoid vasopressin, BB, Ca channel blockers, LA - reduce epi dose to <1mcg/kg Lipid emulsion therapy
28
Drugs to avoid in management of cardiac arrhythmias with LAST
Vasopressin Calcium channel blockers Beta blockers LA (lidocaine)
29
Lipid emulsion therapy dosage
20% therapy Bolus 1.5mg/kg (lean body mass) over 1 minute Infusion 0.25ml/kg/min (at least 30min) - double rate if BP remains low Repeat bolus up to 2 times of CV collapse Max 10-12 ml/kg over first 30 minutes
30
Seizure control in LAST
Benzodiazepines Small doses of propofol (avoid if CV collapse) Small doses of succ or NMB to minimize acidosis and hypoxemia
31
Epinephrine dosage during cardiac arrest due to LAST
<1mcg/kg
32
If ventricular arrhythmias develop Treatment of choice
Amiodarone Avoid lidocaine and procainamide
33
Pt with significant CV event should be monitored for
At least 4-6 hours
34
If event is limited to CNS symptoms that resolve quickly they should be monitored for
At least 2 hours
35
Steps to prevent IV injection
Slow injection Multiple needle redirections and small injection 2-3ml Aspirate for blood every 5 ml Awake and monitored pt US Epi 2.5-5mcg/ml vascular marker Vigilant monitoring
36
Dose of LA is product of
Volume X concentration
37
IV injection of epi s/s
>10bpm increase in HR >15mmHg increase in BP
38
S/S IV injection of epi are masked in
Beta blocked pt Active labor Advanced age General/neuraxial anesthesia
39
To decrease risk of LAST associated with truncal blocks
Use lower concentration Dose on lean body weight Adjunctive epi Observe at least 30-45 minutes
40
Myotoxicity of LA
IM injection of LA causes muscle damage and necrosis
41
Myotoxicity of LA causes
Increase intracellular Ca
42
Myotoxicity of LA Which causes most damage
Bupivacaine
43
Why use adjuncts of LA
Increase block duration Post op analgesia
44
Which blocks is epi for duration excluded
Sciatic Digit blocks
45
Adjuncts to LA examples
Epi A2 agonist (precedex, clonidine) Decadron (Tramadol, buprenex, mag investigational)
46
First liposomal, bupivacaine encapsulated drug
Exparel
47
Exparel is a _____% solution
1.3%
48
Max dose of Exparel
266 mg
49
Dilution of exparel
Diluted to 0.89 mg/ml with NS or LS Use within 4 hours
50
FDA approved use of exparel
TAP blocks
51
If exparel has been used. Don’t give bupivacaine for
96 hours Increased risk of toxicity
52
Obstacles in regional block anesthesia
Surgeon resistance 2 man procedure, stress staff resources Risk of persistent parethesia, nerve injury, paralysis Neurotoxicity from LA IV injection
53
Key to IV injection
Prevention Early recoginition
54
Dose of Decadron IV PNB
10mg IV after GETA induction 2mg per block
55
LA works by
Blocking NA gated voltage channels
56
Form of LA that is active
Protonated Ionized Lipid insoluble
57
To speed the onset of LA you can add HCO3 MOA
More unprotonated from to cross the lipid bilayer 1MeQ of NAHCO3 for every 10 ml of LA
58
First to disappear with LA blockade
B sympathetic fibers Then Fast pain (Type A delta fibers)
59
Most resistant fiber to LA
Slow pain (Type C fiber)
60
Order of common LA from vasodilatory properties to vasoconstricitive properties
Tetracaine Lidocaine Bupivacaine Mepivacaine Ropivacaine
61
LA onset/duration from fastest to slowest
Lido Mepivacaine Ropivacaine Bupivacaine Levobupivacaine Exparel
62
LA are only pharmacologically active in
Free, unbound state
63
Rationale behind hyperventilating patient when suspect LAST
Pushes pH more alkaloid so more LA bound to protein so less free for CV and CNS toxicity

Regional 1 (8 decks)

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