Local Anesthetics Flashcards Preview

Anesthesia > Local Anesthetics > Flashcards

Flashcards in Local Anesthetics Deck (26)
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1
Q

Esters

A

Rapidly hydrolyzed by plasma pseudocholinesterase

Significant metabolite, PABA, known allergen

2
Q

Amides

A

Metabolized by hepatic p450

- rare allergic reactions

3
Q

Local anesthetics structure

A

Lipophilic benzene ring linked to amine group by hydrocarbon chain of ester or amide

4
Q

Pharmacodynamics

A

Ionization best correlates with onset of action

-exist in both ionized and non-ionized forms

5
Q

Ionized form

A

Binds receptor and exerts drugs action but is very hydrophilic and cannot penetrate nerve membrane

6
Q

Non-ionized form

A

Lipid-soluble and allows drug to penetrate nerve membrane

7
Q

Potency of LA

A

Correlates with lipid solubility

Higher solubility = higher potency

8
Q

Duration of action

A

Correlates with protein binding

9
Q

pKa

A

Relative portion of drug ionized vs non-ionized

*low pKa = greater fraction of non-ionized at given pH -> faster onset

10
Q

Speed of onset

A

Low pKa = fast onset
Bicarbonate addition = more non-ionized -> quicker onset
High lipid solubility = slower onset

11
Q

Duration of LA

A

Protein binding = longer duration
More vascular sites = shorter duration
Vasodilation = all LA are vasodilators
Pseudocholinesterase activity = increases duration of esters
Liver disease = increases duration of amides

12
Q

Chloroprocaine

A

Most rapid hydrolysis of esters
Increasing popularity for short acting spinal
Useful in OBdue to rapid onset

13
Q

Lidocaine

A

Versatile - topical, regional, IV, peripheral, epidural, spinal
Transient Neuro symptoms after spinal
- pain/sensory change in low back/buttocks
- complete resolution of symptoms in 10 days

14
Q

Bupivacaine

A

Useful due to long duration in peripheral and epidural blocks
High quality sensory anesthesia relative to motor blockade
Severe, refractory CV collapse with toxic IV doses

15
Q

Ropivacaine

A

Greatest margin of safety among locals

More vasoconstriction, less lipid solubility

16
Q

Tetracaine

A

Useful in spinals due to rapid onset and long duration

17
Q

Cocaine

A

Vasoconstrictor property unique among LA
CNS stimulant
Used in topical solution for laceration repair

18
Q

Emla cream

A

Topical anesthesia for minor procedures (peds IV)
Onset in 45-60 min
Lidocaine and prilocaine

19
Q

Ester LA

A

Chloroprocaine
Cocaine
Procaine
Tetracaine

20
Q

Amide LA

A
Bupivacaine
Lidocaine 
Mepivacaine
Prilocaine
Ropivacaine
21
Q

Additives to LA

A

Vasoconstrictors (epi) decrease vascular uptake -> decrease systemic absorption -> increased duration and intensity

22
Q

Systemic toxicity

A

Results from excessive plasma [ ]

  • dose related
  • rate of injection/infusion
  • vasodilation
  • lipid solubility
  • site of injection
23
Q

Toxicity effects

A

CV: transient increase in HR, BP due to CNS stimulation
-dose dependent myocardial depression
- increased PR interval, QRS, QT
CNS: affected first
- lightheadedness, facial/oral numbness/tingling, tinnitus, seizure, unconsciousness, arrest

Test dose: if in intravascular space -> bump in HR and BP

24
Q

LA toxicity treatment

A

Stop injection/infusion -> GET HELP
maintain airway and give 100% O2, consider hyperventilating
- benzos and proposal
Treat cardiac arrest by standard protocols

25
Q

Methemoglobinemia

A

Caused by LA, antibiotics, nitrates
Signs and symptoms: sob, chest pain, cyanosis, AMS, loss of consciousness
Blood is chocolate brown, ABG reveals normal pO2 with metabolic acidosis -> measure met-Hb
Tx: O2, methylene blue 1-2 mg/kg, hyperbaric O2

26
Q

MOA

A

Weak bases, hydrophilic, tertiary amines
- act by binding Na+ channels, blocking depolarization induced influx and blocking propagation of nerve impulse
-block depends on myelination and diameter
Autonomic > sensory > motor