Local Anesthetics II (Exam IV) Flashcards by Claire Edwards

What is the average pKa of local anesthetics?

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Alkalinization ______ the % of lipid soluble or non-ionized form of LAs

Increases

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What are the benefits of alkalinization?

Faster onset of action - Speeds onset of peripheral and epidural blocks by 3 to 5 mins.
Enhances the depth
Increase the spread (i.e., epidural)

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Regarding weak bases, the pKa is ________ pH.

before

ex. pKa 9, pH 7 → 9 - 7 = +2

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Regarding weak acids, the pKa is ________ pH.

after

ex. pKa 9, pH 7 → 7 - 9 = -2

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Nicely negative numbers are _________.

non-ionized

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If Drug V (weak base) has a pKa of 9.1, will the drug be more ionized or nonionized at physiological pH?

pKa - pH
9.1 - 7.4 = +1.7

Drug V will be more ionized at physiological pH.

Weak Bases, pKa before pH
Weak Acids, pKa afterpH

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If the pKa of LA (a weak base) is at 4.5, will the drug be more ionized or nonionized at physiological pH?

pKa - pH
4.5 - 7.4 = -2.9

LA will be more non-ionized at physiological pH.

Weak Bases, pKa before pH
Weak Acids, pKa afterpH

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LA1’s pKa is 9.2, and LA2’s pKa is 7.5. Which of the following are correct when placed in physiological pH? Select 2 answers.

A. LA2 has more non-ionized components
B. LA1 has more ionized components
C. LA2 has more ionized components
D. LA1 has more non-ionized components

B and C

LA1
9.2 - 7.4 = +1.8 (ionized)

LA2
7.5 - 7.4 = +0.1 (ionized)

Weak Bases, pKa before pH
Weak Acids, pKa afterpH

This shouldnt be select 2. the answer should just be B becuase overall LA1 is more ionized.

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Adjuvant:
1. _____ increases the duration of both motor and sensory blocks. It is the first analgesic request after spinal anesthesia
2. _____ Increases the duration with SAB with or without opioids
3. _____ and _____ will give us a prolonged duration with pediatric regional anesthesia
4. _____ gives us increased duration and it is given either IV or mixed with LA

Dexmedetomidine IV
Magnesium
Clonidine & Ketamine
Dexamethasone

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What will be the results of combining LA Chloroprocaine & Bupivacaine?

Produce a rapid onset
Tachyphylaxis (bupivacaine)

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What is added to 30 mL of LA to alkalinize the drug? what does this do to the LA?

1 mL of 8.4% Sodium Bicarbonate

This will increase the non-ionized form of LA.

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Combining local anesthetics and getting toxic effects is a synergistic process. T/F ?

False. The toxic effects are additive. (1+1 =2)

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Compare the onset of action between chloroprocaine and bupivacaine.

Chloroprocaine: Rapid
Bupivacaine: Slow

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What vasoconstrictors can be utilized with local anesthetics?

Epinephrine
Phenylephrine

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Why is it important to use vasoconstrictors with LA?

The duration of action of a LA is proportional to the time the drug is in contact with nerve fibers.

Adding a vasoconstrictor will keep the LA in that area instead of it spreading systemically (think lidocaine and its vasodilatory effects, epi offsets this)

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Results of using vasoconstrictors with LA:
1. ______ Neuronal uptake of LA
2. α-adrenergic effects may have some degree of _____
3. No effect on the onset rate of LA
4. Enhanced _____ irritability with inhaled anesthetics
5. Systemic absorption of the vasoconstrictor can lead to ______ and ______

Increased
Analgesia
Cardiac
HTN and Tachycardia

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What is epinephrine 1:200,000 mean?

Convert that to mcg/mL.

1:200,000 means 1 gram of epinephrine is dissolved in 200,000 mL of solvent.

1g/200,000 mL
1000mg/200,000 mL
1 mg/200 mL
1000 mcg/200 mL
10 mcg/2 mL
5 mcg/mL

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How much epinephrine or phenylephrine is given with bupivacaine or lidocaine for a subarachnoid block (SAB)?

0.2 mg Epi
2 mg Phenylephrine

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Compute 1:500,000 Epi to mcg/mL

1,000,000/ 500,000=2

2 mcg/mL

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Compute 1:10,000 Epi to mcg/mL

1,000,000/ 10,000 = 100

100 mcg/mL

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Compute 1:1000 Epi to mcg/mL

1,000,000/ 1000 = 1000

1000 mcg/mL

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0.25% equates to how many mg per mL ?

2.5 mg/mL

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0.5% equates to how many milligrams per milliliter?

5 mg/mL

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1% equates to how many milligrams per mL ?

10 mg/mL

2% equates to how many milligrams per mL ?

20 mg/mL *2% lidocaine is the most common concentration used in the OR*

4% equates to how many milligrams per mL ?

40 mg/mL

Your surgeon injected 20 mLs of Bupivacaine 0.25% with 1:200,000 of Epi. What are the total mgs for Bupivacaine and the total mcgs for Epinephrine?

Bupivacaine: 0.25% = 2.5 mgs/mL 2.5 mgs x 20 mLs = 50 mgs total Epinephrine: 1:200,000 = 5 mcg/mL 5 mcg x 20 mLs = 100 mcg total

What is the Lidocaine Recommended Max Single Dose for Spinal?

100 mg

Prilocaine Recommended Max Single Dose

600 mg

Bupivacaine Recommended Max Single Dose Bupivacaine Recommended Max Single Dose with/Epi Bupivacaine Recommended Max Single Dose for Spinal

175 mg 225 mg w/ Epi 20 mg

112.5 mg of Bupivacaine with Epi and 250 mg of Lidocaine with Epi were given during surgery. What are the percentages of each LA based on the recommended max single dose in mg?

Max single dose of Bupivacaine with Epi: 225 mg 112.5/225 = 50% Max single dose of Lidocaine with Epi: 500 mg 250/500 = 50% ## Footnote *(even though its 50% of each..its 100% of the max dose for LAs so we cant give more)*

Where are topical anesthetics applicable?

Applicable on the mucous membranes of the nose, mouth, tracheobronchial tree, esophagus, or GU tract.

Which anesthetic has localized vasoconstriction that will decrease blood loss and improve surgical visualization?

Cocaine (4-10%)

Which anesthetic is great with surface anesthesia?

Lidocaine (2-4%)

Lidocaine inhalation does not alter airway resistance, but does cause ______.

vasodilation

True/False: Procaine and Chloroprocaine are good choices for topical anesthesia.

False *These drugs do not penetrate mucous membranes as effectively as cocaine or lidocaine.*

What does LTA stand for?

* Lidocaine transtracheal anesthesia

Eutectic Mixture of LA (EMLA) contains what two local anesthetics? Dose: Onset:

Lidocaine 2.5% + Prilocaine 2.5% = 5% LA Dose: 1 to 2 g/ 10 cm2 area Onset: 45 mins

EMLA has to be applied for ______ hours before skin graft.

2 hours

For these procedures below, when would we want to apply EMLA cream? - Cautery of genital warts - Venipuncture, lumbar puncture - Arterial cannulation (Nitroglycerine) - Myringotomy

10 min before

What considerations should one have when using EMLA ?

* Caution with methemoglobinemia (bc of the prilocaine) * No open skin wounds * No amide allergy patients

Other Topical Anesthesia Preparations besides EMLA

* Amethocaine (EMLA-like) * Tetracaine 4% Gel * Lidocaine 7% * Tetracaine 7%

What is considered local infiltration with LA?

Extravascular placement of LA (subcutaneous injection)

What LAs are used on inguinal operative sites?

* Lidocaine 1% or 2% * Ropivacaine 0.25% * Bupivacaine 0.25%

What are the contraindications of using epinephrine on LA for local infiltrations?

* Not intracutaneously or into tissues at end arteries * Fingers, toes, ears, nose, penis *vasoconstriction --> ischemia --> necrosis.*

How is Peripheral Nerve Block achieved?

Achieved by LA injection into tissues surrounding individual peripheral nerves or nerve plexuses.

What is the MOA of peripheral nerve blocks?

diffusion from outer mantle to central core of nerve along a concentration gradient.

What area (proximal or distal) is affected first with local anesthetic administration?

The proximal area (site of LA administration) is affected first and then distal.

When the peripheral nerve block is wearing off, what comes back first? Proximal or Distal?

Proximal comes back first & then distal.

With a peripheral nerve block, how does the numbing sensation spread (what fibers are affected first/last)

***Smallest sensory and ANS fibers first, then larger motor and proprioceptive axons.***

Peripheral Nerve Block onset of action is dependent on the local anesthetic's _________. While the duration is dependent on the _____.

pK Dose

Peripheral nerve block: OOA of Lidocaine and Bupivacaine

Lidocaine: 3 min Bupivacaine: 15 min

What are the benefits of a continuous infusion block?

* Improved pain control * Less nausea * Greater satisfaction * Additives are used with continuous infusion blocks (ie: Ketolorac, Ketamine, Decadron) ## Footnote *(Additives will prolong duration)*

What is a Regional Bier Block?

Bier Block IV injection of LA into an extremity isolated from the rest of the systemic circulation with a tourniquet. Sensation and muscle tone return dependent on tourniquet release

What LA is commonly used in Bier Block?

**Lidocaine**

What are the steps to performing a Bier Block?

**1. IV start 2. Exsanguination 3. Double cuff 4. LA injection 5. IV D/C**

What is the sequence of blockades for a segmental block in Neuraxial Anesthesia?

1. SNS (Myelinated preganglionic B fibers) 2. Sensory (Myelinated A-beta & A-delta fibers, unmyelinated C fibers) 3. Motor (Myelinated A-alpha fibers)

Which of the following will be the last sign associated with injection of an anesthetic for neuraxial blockade? A. NIBP B. Heart Rate C. Cold Alcohol Pad D. Leg Movement

D. Leg Movement

How is a Spinal Anesthesia Block (SAB) produced?

Direct injection of LA into subarachnoid/spinal area

What is used for confirmation of a Spinal Anesthesia Block (SAB)?

**CSF**

What is the principal site of action for sub arachnoid block?

Preganglionic fiber

For SAB, the _______ effect is on the same level of denervation.

sensory

For SAB, the _______ effect is 2 spinal segments cephalad (above) of the sensory block. For SAB, the _______ effect is 2 spinal segments below the sensory block.

SNS Motor

If our sensory block is at T10, what level is the motor and SNS block?

SNS: T8 Sensory: T10 Motor: T12

If the sensory block is at T5, where is the SNS block?

T3 *This SNS block will trigger an asystole event.*

What dermatomes correspond with our cardiac accelerator?

T1 to T4

Clinical Scenario Slide: If the assessed sensory level after SAB is T6 ( Top of Xiphoid Process), what are the blocked SNS and motor levels?

SNS Block: T4 Motor Block: T8

What factors affect SAB dosage?

* Height of patient (volume of subarachnoid space) * Segmental level of anesthesia desired * Duration of anesthesia desired

For SAB, _____ is more important than _______ of drug (%) or the volume (mLs) of the solution injection.

Dose; Concentration

What is the dose of bupivacaine for the scenario below? 5 ft tall patient = _____mL of 0.75% Bupivacaine + ______ mL for every inch above…. 2 cc total ( 1½ hours to 2 hours) If our patient is 5'5", how much bupivacaine will we give for SAB?

1 mL 0.1 mL *For someone who is 5'5", you will give 1.5 mL of bupivacaine for a SAB.*

What dose of 0.75% bupivacaine would be indicated for a 6'7" patient undergoing a SAB?

2mL ## Footnote *2mL is the MAX*

For SAB, the _________ of LA is important in determining the spread of the drug.

specific gravity

What can be added to LA so that its specific gravity can increase? What can be added to LA so that its specific gravity can decrease?

Glucose added → hyperbaric solution. Distilled water added → hypobaric solution

Which side will you want to position a right-hip arthroplasty patient on if they receive a hyperbaric LA solution?

Right side lying, the hyperbaric solution will "sink."

Which side will you want to position a right-hip arthroplasty patient on if they receive a hypobaric LA solution?

Left side lying, the hypobaric solution will "float".

The most common LA used in Epidural Anesthesia.

Lidocaine *Good diffusion through tissue and safer*

What is the onset of epidural anesthesia?

Onset: 15 to 30 minutes

Epi 1:200,000 with ___________ offers no advantage in an epidural block.

bupivacaine

Can epidural anesthesia cross the placental barrier with OB and C-section patients?

Yes ## Footnote *(Effect on fetus at 24-48 hrs. Lidocaine more than bupivacaine)*

What is the difference between SAB and epidural blocks?

**No differential zone of SNS, sensory, and motor blockade with epidurals.** ## Footnote *(Large doses required to get differential zone with epidural)*

What is considered an acceptable additive to both epidural and SAB to produce a synergistic effect?

Opioids

True/False: Between Lidocaine and Bupivacaine, the former will cross the transplacental barrier more than the latter.

True

What is Tumescent Liposuction?

Subcutaneous infiltration of large volume (5L or more)

What makes up the tumescent solution?

* Diluted Lidocaine 0.05% to 0.1% (0.5-1mg/ml) * Epinephrine 1:100,000 (10mcg/ml)

What causes the tumescent effect?

The taunt stretching of overlying blanched skin d/t large volume → Tumescent Effect *Fat can be aspirated without blood loss and provide prolonged post-op analgesia.*

Where is tumescent usually administered?

* Thigh * Abdomen * Hips * Buttocks

When is the LA plasma peak for tumescent anesthesia?

12 to 14 hours s/p injection.

What is the dose for Regional Anesthesia Lidocaine with Epi?

7 mg/kg

Highly diluted Lidocaine with Epi Tumescent dose.

**35 to 55 mg/kg**

What is the theory with the Tissue Buffering System?

1 gram of SQ can absorb up to 1 mg of Lidocaine

Local Anesthetics II (Exam IV) Flashcards

(91 cards)