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Apex Review > Local anesthetics 4 > Flashcards

Local anesthetics 4 Flashcards

1
Q

LAST is more common with ______________ than with ____________

A

peripheral nerve blocks than with epidural anesthesia

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2
Q

The risk of LAST is increased in the setting of

A

hypoxia, hypercarbia, acidosis, and hyperkalemia

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3
Q

___________ is the only local anesthetic with vasoconstrictive properties

A

Cocaine

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4
Q

_______________ is the primary risk of cocaine toxicity

A

Excessive SNS stimulation

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5
Q

Cocaine toxicity is best treated with

A

a vasodilator or a mixed alpha and beta antagonist such as labetalol

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6
Q

Cardiovascular toxicity causes

A

conduction block
depresses the myocardium
and reduces systemic vascular resistance

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7
Q

CNS complications such as seizures occur _________ CV complications with LAST.

A

before

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8
Q

_____________ is the exception because cardiac complications (myocardial depression, AV block, cardiac arrest) often occurs before a seizure.

A

Bupivacaine

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9
Q

Analgesia occurs at a plasma concentration of ________ mcg/mL of lidocaine

A

analgesia

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10
Q

At a plasma concentration of _________ mcg/mL of lidocaine, tinnitus, skeletal muscle twitching, numbness of lips and tongue, restlessness, vertigo, blurred vision, hypotension, and myocardial depression.

A

5-10 mcg/mL

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11
Q

At a plasma concentration of ______________ of lidocaine seizures and loss of consciousness may occur.

A

10-15 mcg/mL

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12
Q

At a plasma concentration of __________ of lidocaine coma and respiratory arrest can occur.

A

15-25 mcg/mL

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13
Q

At a plasma concentration of ___________ of lidocaine cardiovascular arrest can occur.

A

> 25 mcg/mL

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14
Q

How does hypercarbia increase the potential for LAST?

A

hypercarbia increases cerebral blood flow and increases drug delivery to the brain
decreases protein binding and increases the free fraction available to enter the brain

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15
Q

How does hyperkalemia increase the risk for LAST?

A

raises resting membrane potential, making neurons more likely to depolarize

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16
Q

How does metabolic acidosis increase the risk for LAST?

A

decreases the convulsion threshold and favors ion trapping inside the brain

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17
Q

Factors that decrease the risk of LAST include

A

hypokalemia, hypocarbia, and CNS depressants

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18
Q

What two features determine the extent of cardiotoxicity?

A

affinity for the voltage- gated sodium channel in the active and inactive states
rate of dissociation from the receptor during diastole

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19
Q

The risk of bupivacaine toxicity is increased with

A

pregnancy
beta-blockers
calcium channel blockers
digitalis

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20
Q

Rank the difficulty of cardiac resuscitation with local anesthetics:

A

bupivacaine> levobupivacaine> ropivacaine> lidocaine

21
Q

Cocaine should be avoided with

A

MAOIs
TCAs
sympathomimetic drugs

22
Q

Beta blockade in the setting of cocaine overdose is a questionable practice that allows for

A

unopposed alpha-1 stimulation. High SVR (alpha 1 stimulation caused by cocaine) and reduced inotropy (beta-1 antagonism) set the stage for congestive heart failure and CV collapse

23
Q

What is the best tx for cocaine toxicity?

A

a vasodilator such as nitroglycerine is best but if given a list of beta-blockers than labetalol (or another mixed alpha and beta antagonist) is a reasonable choice

24
Q

The maximum allowable dose for cocaine is

A

200 mg

25
Q

The dose range for cocaine is

A

1.5-3.0 mg/kg

26
Q

One minute following an interscalene block, a 62 kg patient has a seizure. How much 20% lipid emulsion should you administer?

A

93 mL

27
Q

What are the steps to treating LAST?

A
  1. manage the airway
  2. treat seizures with a benzodiazepine
  3. ACLS w/ modifications
  4. administer 20% lipid emulsion therapy
  5. avoid beta-blockers and calcium channel blockers
  6. If the patient is unresponsive to modified ACLS and lipid emulsion therapy, prepare for cardiopulmonary bypass
28
Q

What should you not give for seizures in the LAST patient?

A

propofol

29
Q

What is the agent of choice for ventricular dysrhytmias for the patient with LAST?

A

amiodarone

30
Q

What drugs should be avoided with LAST?

A

vasopressin
lidocaine
procainamide
epinephrine

31
Q

Why should epinephrine be avoided with LAST?

A

epinephrine reduces the efficacy of lipid emulsion therapy
if you must give it, then limit the dose to <1 mcg/kg

32
Q

For 20% lipid emulsion therapy what is the bolus and infusion dose for a patient over 70 kg:

A

bolus = 100 mL over 2-3 minutes
infusion = 250 mL over 15-20 minutes
if the patient remains unstable–> repeat bolus and/or double the infusion

33
Q

For 20% lipid emulsion therapy what is the bolus and infusion dose for a patient under 70 kg:

A

bolus: 1.5 mL/kg of lean body weight over 2-3 minutes
infusion: 0.25 mL/kg/min.
if the patient remains unstable–> repeat bolus and/or double the infusion

34
Q

LAST can be reduced by

A

using a test dose and incremental dosing with periodic aspiration

35
Q

______ & ____________ will worsen the symptoms of LAST

A

hypoxia and acidosis

36
Q

If benzodiazepines are ineffective to treat a LAST seizure,

A

a small dose of succinylcholine or a non-depolarizer should be given to stop muscle contraction
this minimizes O2 consumption, hypoxemia, and acidosis although it will not stop seizure activity in the brain

37
Q

Why is propofol avoided for seizures in LAST?

A

larger doses of propofol augment myocardial depression

38
Q

If epinephrine is used in last, the recommended dose is

A

below 1 mcg/kg

39
Q

The maximum recommended dose of lipid emulsion is

A

12 mg/kg

40
Q

The infusion of lipid emulsion should be continued for

A

a minimum of 15 minutes after the patient regains CV stability

41
Q

Is lipid emulsion safe in pregnancy?

A

yes

42
Q

What is a theoretical complication secondary to hyperlipidemia and hyperamylasemia after lipid emulsion therapy?

A

pancreatitis

43
Q

The proposed MOA of lipid emulsion therapy includes?

A

lipid sink- sequesters LA and reduces the plasma concentration of LA
metabolic effect- enhanced myocardial fatty acid metabolism
inotropic effect- increased Ca+ influx and intracellular Ca+ concentration
membrane effect- impairs LA binding to Na+ channels

44
Q

What is the MAXIMUM recommended dose for lidocaine during tumescent anesthesia?
a. 5 mg/kg
b. 7 mg/kg
c. 55 mg/kg
d. 75 mg/kg

A

C. 55 mg/kg

45
Q

Tumescent anesthesia provides

A

comfort during liposuction

46
Q

The plasma concentration of lidocaine peaks at __________ and is completely eliminated by _____________

A

12 hours; 36 hours

47
Q

GA for liposuction is recommended if > ____________ of tumescent is planned

A

2-3 L

48
Q

_______ & __________ may occur as a result of intravascular volume expansion when using tumescent lidocaine.

A

fluid overload
pulmonary edema

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