Local And Regional Anesthetics

Question 1

Esters - hydrolysis, examples, do they have allergic rxn?

Answer 1

• Hydrolysis by pseudo cholinesterase enzyme
• Cocaine, chloroprocaine, procaine, tetrocaine
• Yes, they are known for allergic reactions

Question 2

Amides (local anesthetics) - metabolism, examples, allergic rxn?

Answer 2

Liver metabolism CYP450
Lidocaine, bupivicaine, ropivicaine, etidocaine, mepivicaine

Question 3

Lidocaine:

Answer 3

Weak base - pKa of 7.8
Mainly ionized at physiological pH
1h duration
2h duration w/ adrenaline
CNS and CVS toxicity
Max dose:
- 200mg (20ml of 1%)
- 500mg (50ml of 1%)

Question 4

Bupivicaine:
Dose

Answer 4

Max of 150mg (30ml of 0.5%)
Selective cardiotoxicity
Highly plasma protein bound
Tachyphylaxis is rare

Question 5

What is tachyphylaxis?

Answer 5

Appearance of progressive decrease in response to a given dose after repetitive administration of the drug

Question 6

Does increased fraction of unionized drug increase the onset of action?

Answer 6

Yes

Question 7

Factors increasing potency and duration of action of local anesthetics?

Answer 7

Greater oil/water partition coeffectient = greater lipid solubility = greater potency

Greater protein binding = greater greater duration of action

Question 8

What to do in systemic toxicity with local anesthetics?

Answer 8

Lipids and CPR

Question 9

Lidocaine toxicity starts at?

Answer 9

3 Ug/mL with circumoral and tongue numbness

Goes all the way to coma, respiratory collapse and CVS collapse

Question 10

Main disadvantage of regional anesthesia? The others are easy to guess

Answer 10

Hypotension

Question 11

Spinal injection properties?

Answer 11

Lumbar region only
Brief but high block quality

Question 12

Epidural injection qualities?

Answer 12

Can be done anywhere on spinal cord
Longer but less ecfdcfice block
Requires 5-6x higher dosage

Question 13

Type of local anesthetic blocks?

Answer 13

Motor - muscle paralysis, weakness
Sensory - total anesthesia
Sylpathetics - hypotension, bradycardia

Question 14

Sequence of events with regional anesthetics:

Answer 14

• 1 - sympathetic block - vasodilation
• 2 - loss of pain and temperature sensation
• 3 - loss of proprioception
• 4 - loss of touch and pressure sensation
• 5 - loss of motor function

Question 15

Chloroprocaine:

Answer 15

Use of vasoconstrictors is contraindicated
Good short duration spinal procedure

Question 16

Lidocaine:

Answer 16

60 to 90 mins
Sensory and motor block
60-75mg
Transient neurologic symptoms in 1/3

Question 17

Bradycardia is caused by blockade where?

Answer 17

T1 to T4

Question 18

Which regional anesthetic is greatly affected by vasoconstrictors?

Answer 18

Tetracaine

Question 19

Spinal injection for sylpathetics block vs motor block

Answer 19

Motor block is 2 dermatomes lower

Question 20

Hyperbaric anesthetic is mixed with?
Hypobaric?

Answer 20

Dextrose
Sterile water

Question 21

Absolute spinal injection contraindications?

Answer 21

Sepsis
bacteremia
Skin infection
Hypovolemia
Coagulopathy
Anticoagulation
Increase ICP
Lack of consent

Question 22

Relative spinal injection contraindication:

Answer 22

Peripheral neuropathy
Heparin
Psychosis
Aspirin or antiplatelet
Demyelunated CNS disease
Cardiac lesion
Emotional instability
Prolong surgery
Surgical team resistance

Question 23

Epidural anesthesia location?

Answer 23

Widest L2
Narrowest C5
Prefer L3-L4
Skin to epidural space is 4-6cm

Question 24

Anesthetic test:

Answer 24

3mL lidocaine 1.5% with epinephrine 1:200,000

Question 25

Epidural techniques

Answer 25

Midline Paramedian Taylor L5-S1 Caudal - pediatrics single shot

Question 26

Lower pKa effect on local anesthetics:

Answer 26

-> Un-ionizes faster -> faster onset of action Also why adding sodium bicarbonate (NaHCO3) increases speed of onset

Question 27

Regional anesthesia advantages:

Answer 27

Cheap High patient satisfaction Maintain patient airway Decreased blood loss Selective muscle relaxation Decreased incidence of DVT and PE

Question 28

Regional anesthesia disadvantages:

Answer 28

Hypotension Risk of toxicity Many patients prefer to be asleep Skills required Patient can talk Patient anxiety Not reliable

Question 29

Location of spinal and epidural anesthesia:

Answer 29

Spinal - Lumbar only, subarachnoid space Epidural - Along spinal cord, epidural space

Question 30

Where does the spinal cord end in the vertebral column in adults and infants?

Answer 30

- Adults - L1/L2 - Childern - L3

Question 31

Dura and arachnoid end at?

Answer 31

S2

Question 32

Chlorprocaine:

Answer 32

- 11mg/kg -> up to 13 w/ E - CONTRAINDICATED WITH VASOCONSTRICTORS - Enhanced by fentanyl and clonidine - Used in short procedures

Question 33

Lidocaine:

Answer 33

- 5mg/kg -> up to 7 w/ E - 60 - 90 mins - Good sensory and motor block - Transient neurological symptoms in a third of patients - Used in short procedures

Question 34

Bupivicaine:

Answer 34

- 2.5mg/kg -> up to 3mg/kg w/ E - 90-120 mins

Question 35

Tetracaine:

Answer 35

- 2.5mg/kg -> up to 3mg/kg w/ E - 90 - 120 mins - Effect is doubled with vasoconstrictors

Question 36

Blockade where causes bradycardia?

Answer 36

T1-T4

Question 37

Most ideal patient position for regional anesthesia:

Answer 37

- Regional anesthesia

Question 38

Complications for spinal anesthesia:

Answer 38

- Failed block - Back pain - Hypotension - Local anesthesia toxicity - High blockade - Urinary retention - Local infection - Meningism - Epidural hematoma - Spinal headache

Question 39

Factors affecting distribution of spinal anesthesia:

Answer 39

- Level of injection - Shape of spinal column - Patient height - Angulation of needle - Volume of CSF - Characteristics of local anesthetic (density, specific gravity, baricity) - Dose - Patient position

Question 40

Absolute contraindications of spinal anesthesia:

Answer 40

- Sepsis - Back pain - Skin infection - Severe hypovolemia - Coagulopathy - Therapeutic anticoagulation - Increase intracranial pressure - Lack of consent

Question 41

Relative contraindications of spinal anesthesia:

Answer 41

- Peripheral neuropathy - Mini-dose heparin - Psychosis - Aspirin or other antiplatelet drugs - Demyelinated CNS diseases - Certain cardiac lesions (aortic stenosis) - Emotional instability - Prolong surgery - Sirgical team resistance

Question 42

Verterbal canal is widest at ____ Narrowest at ____ Preferable location of administration _____ Distance from skin to epidiral space ______

Answer 42

L2 C9 L3-L4 4-6cm (can be from 3-8cm)

Question 43

Epidural test (dose, explain)

Answer 43

3mL lidocaine 1.5% w/ epinephrine - Test for intravenous or intrathecal catheter placement Positive test: - Tachycardia - High BP - Light headedness - Metallic taste in mouth - Ringing in ears - Facial numbness

Question 44

Does patient position affect epidural anesthesia?

Answer 44

NO

Question 45

Complications of epidural administration:

Answer 45

- Penetration of blood vessels - Hypotension - Nausea and vomiting - Headache - Back pain - Intravascular catheterization - Dural puncture - Infection