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Regional > Regional Introduction > Flashcards

Regional Introduction Flashcards

1
Q

What are the three structures of that make up LA?

A

Aromatic Ring – fat soluble (hydrophobic)
Terminal Amine – water soluble (hydrophillic)
Intermediate link - Ester or Aminde

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2
Q

Generally what are three characteristics of Esters?

A
  • -Are less stable (shorter shelf life)
  • -Metabolized in the plasma by pseudocholinesterases
  • -More prone to cause allergic reactions
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3
Q

Generally what are three characteristics of Amides?

A
  • -More stable
  • -Metabolized by liver
  • -Rare allergies
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4
Q

Chemical structure of LA, what two important reasons why they are placed in an acidic environment (vial)?

A

This acidity is important for 2 reasons:

  • –At this pH they are highly ionized, it is this portion that is H2O soluble
  • –Epi (if added) needs an acidic pH as it is unstable in alkaline environments
  • —NaHCO3 is often added to hasten onset
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5
Q

How is the potency of LA determined?

A

Lipid solubility or length of chain is related to potency

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6
Q

How is the duration of action of LA determined?

A

Protein binding is related to duration of action

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7
Q

How is the onset of an LA determined?

A

pKa is related to the onset

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8
Q

To successfully block myelinated fibers, LAs must block how many nodes?

A

To successfully block myelinated fibers; LA’s must generally inhibit 3 successive nodes of ranvier

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9
Q

What is the order of the Nerve fiber blockade? from first to last?

A 
B fibers
C and A delta Fibers
A gamma Fibers
A beta Fibers
A alpha fibers
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10
Q

What are B fibers responsible for?

A

Autonomic and sympathetic efferent

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11
Q

What are C and A Delta fibers responsible for?

A

Temperature and touch

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12
Q

What are A Gamma fibers responsible for?

A

Muscle tone for skeletal muscles

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13
Q

What are A beta fibers responsible for?

A

Small motor with sensations of touch/pressure

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14
Q

What are A alpha fibers responsible for?

A

innervate skeletal muscle for large motor and proprioception

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15
Q

Are all A fibers myelinated or unmyelinated?

A

All A fibers are myelinated

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16
Q

What are B-fibers?

A

Preganglionic autonomic nerve fibers

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17
Q

B fibers myelinated or unmyelinated?

A

B fibers are myelinated

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18
Q

C fibers myelinated or unmyelinated?

A

C fibers are unmyelinated

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19
Q

What are C fibers?

A

pain (slow), reflex responses, postganglionic autonomic

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20
Q

What are A delta fibers?

A

sensations of pain (1st;fast), temp., touch

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21
Q

What a-1 agonists can you give as local anesthetic “adjuvants”?

A

Epinephrine
Phenylephrine

These are a-1 agonists
(vasoconstrictors)

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22
Q

How will Epinephrine effect the local anesthetic as an “adjuvants”?

A
  • -Makes more acidic; increases shelf life
  • -Prolongs & incr. intraneural conc. of LA’s
  • -Decreases blood flow to area thus less taken up in blood and carried away; also increasing time fibers are exposed to increased concentrations (incr. block)
  • -Now also thought to exert presynaptic adrenergic receptor activity that contributes to analgesia
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23
Q

What will sodium bicarbonate do if you add it as an adjuvant to local anesthetics?

A
  • -Used clinically to speed onset of block
  • -Increases amount of “nonionized” form available to cross membrane
  • -Inconsistent
  • -May see more effect with epinephrine containing locals
24
Q

What class are used as an adjuvant to local anesthetics, especially with central blocks? This improves perioperative analgesia as well.

A

Opioids

Also see a reduction of supraspinal side effects seen w. systemic opioids

25
Q

Opioids and spinal analgesia modulated what fibers in the spinal cord?

A

A-delta & C fibers in the spinal cord

26
Q

What type of affects does opioids and LA have?

A

A synergistic affect

27
Q

What are major concerns/side effects with using opioids in conjunction with local anesthetics?

A

Pruritis
N/V
Urinary retention

28
Q

If you use opioids in conjunction with local anesthetics, what other drugs will it require you to use less of?

A

Reduces the requirements of Volatile Anesthetics

29
Q

What is the most commonly used alpha-2 adrenergic agonist in conjunction with local anesthetics?

A

Clonidine

30
Q

Alpha-2 adrenergic agonists are used in why type of blockade?

A

Used in central blockade

31
Q

What are alpha-2 adrenergic agonists suppose to do when it is used with local anesthetics?

A

It enhances analgesia without opioid side effect profile

32
Q

Alpha-2 adrenergic agonists binds to a-2 receptors on which two sites in the body?

A

Binds to a-2 receptors on primary afferent fibers and several brainstem nuclei

33
Q

Alpha-2 adrenergic agonists increases AcH and norepi in the (Blank) and inhibits the release of several other (Blank)?

A

Increases AcH and norepi in CSF and inhibits release of several neurotransmitters

34
Q

Absorption of local anesthetics depends on many factors such as injection site. What is the order of injection site that will be more more vascular/ increase absorption?

A 
Tissue blood flow:  More vascular/ incr. absorption
IV
Intercostal
Tracheal
Caudal/paracervical
Epidural
Brachial plexus
Spinal
SubQ
  ****presence of epi will decrease absorption
35
Q

Do Local anesthetics cross the BBB?

A

Yes

locals readily cross the BBB

36
Q

CNS toxicity can occur with direct IV injection or by?

A

CNS toxicity can occur with direct IV injection or systemic absorption

37
Q

What are signs and symptoms of local anesthetic toxicity?

A

S/S dose dependent

  • Vertigo/Lightheadedness
  • “Tinnitius” Visual/auditory disturbances
  • Circumoral numbness
  • Ominous feelings
  • Muscle twitching
  • Convulsions
  • unconsciousness
  • Coma
  • Resp/ Cardio collapse
38
Q

What are some ways that you can prevent local anesthetic toxicity? (not talking about adding epi)

A
  • Choice of appropriate drug/dose
  • Frequent aspiration from catheter (epid)
  • Small “test doses”
  • Checking for systemic effects
  • Monitors
  • Slow injection
39
Q

What is the treatment for local anesthetic toxicity? (other than intralipid)

A 
Dependent on severity
-Stop injection
-Know s/s
-Maintain patent airway/O2
barbs/benzo’s
-Tx CV s/s
Initially excitation
Tachy, hypertension
Followed by depression
--Decr CO, hypotension
Fluids, phenylephrine, vasopressin, norepi
--Cardiac arrest
Amniodarone, vasopressin vs. epi and lidocaine
Increased resuscitation time
40
Q

If using 20% intralipid for local anesthetic toxicity, how do you give it?

A
  • -Administer 1.5 mL/kg as an initial bolus; the bolus can be repeated 1- 2 times for persistent asystole.
  • -Start an infusion at 0.25 mL/kg/min for 30-60 minutes; increase infusion rate up to 0.50 mL/kg/min for refractory hypotension
41
Q

How can you tell if a Local anesthetic is an Ester or Amide?

A

Esters have one i, Amides have 2 i’s.

42
Q

How are esters and amides metabolized?

A

Esters are metabolized by pseudocholinesterase. Amides are cleared by the liver.

43
Q

what is Pseudocholinesterase?

A

Pseudocholinesterase is an enzyme produced by the liver and circulates in the plasma.

44
Q

What are ester local anesthetics derived from?

A

Ester local anesthetics are derivatives of benzoic acid.

45
Q

What is the metabolic end product for an ester local anesthetic?

A

Para-aminobenzoic acid (PABA) is a metabolic end product of ester local anesthetics.

46
Q

What is the toxic manifestations for lidocaine?

A

Toxic manifestations of Lido 4ug/ml. Tongue numbness, lightheadedness.

47
Q

Whats the relationship between benzoic acid and PABA?

A
  • -Benzoic acid = ester local anesthetics = PABA (Para-aminobenzoic acid)
  • -PABA can cause allergic reactions
  • -Esters cause allergic reactions more so than amides secondary to PABA
48
Q

Which local anesthetic can can induce methemoglobinemia??

A
  • —Prilocaine may induce methemoglobinemia.

- – O-toluidine is a metabolite of liver metabolism of prilocaine which may cause methemoglobinemia.

49
Q

What is Methemoglobinemia?

A

—Methemoglobinemia: Normal hemoglobin has iron in the ferrous state (Fe++) Met-Hb has iron in the ferric state (Fe+++) O2 carrying capability is poor. Tx. Methylene blue 1-2mg/kg over 5 minutes.

50
Q

Which preservative can cause an allergic reaction?

A
  • —Paraben derivatives (have microbial actions) can cause allergic rxns.
  • –Parabens are cytotoxic – do not use for spinal , epidural or intravenous regional anesthesia.
  • –Needs to say Methylparaben Free or MPF
51
Q

What are the Local Anesthetics clinical uses?

A
  • –Topical
  • –Infiltration (for Aline/Pline)
  • -Field block
  • -Nerve block
  • -Intravenous regional anesthesia (Bier block)
  • -Spinal anesthesia
  • -Epidural anesthesia (caudal)
52
Q

What are two types of Central nerve blocks?

A

Spinal and Epidural

53
Q

What makes a Spinal block different from an epidural block?

A
  • -Small volume
  • -Direct-Sheath (in the spinal cord, right at the nerves)
  • -Rapid onset
  • -Total neural block (from this area and below) (BP will quickly drop)
54
Q

What makes an epidural block different from a spinal block?

A

Large volume
Outside-Sheath
Slow onset (has to slowly diffuse into the sheath)
Block varies with dose
(the more volume you put the higher the block will be

55
Q

What are some advantages from doing a peripheral block than doing a central one?

A
  • -Segmental block (don’t see a huge sympathetocmy)
  • -Slow onset = time to Rx side effects
  • -Flexibility in density
  • -Flexibility in duration
  • -Less side effects
56
Q

What are some disadvantages from doing a peripheral block than doing a central one?

A
  • -More technical & more failure
  • -More time consuming
  • -Greater LA volume- [>toxicity risk]
  • -Faulty block
57
Q

What are some things you need to consider with peripheral nerve blocks in terms of equipment?

A
  • -Usually to perform any peripheral nerve block, you will need specialized equipment
  • -This equipment includes specially insulated needles and a nerve stimulator
  • -They are hooked up to each other to generate a pulse current so that when you are near a nerve, you will see the area innervated by the nerve react
  • -This helps you localize the nerve much more efficiently and makes the percentage of you getting a good block climb tremendously
  • -It is no longer a completely “BLIND” technique

Regional (12 decks)

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