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🏠3. Local and General Anesthesia

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Question Bank

1
Local anesthesia route of admin
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• topical • injection

2
What are the two main types of LA
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Esters and Amides

3
Which types of local anesthetics are no longer available in dental cartridges due to risk of allergic reactions?
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Esters

4
What are the desirable properties of injectable local anesthetics?
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• transient and completely reversible • Does not cause permanent nerve damage. • Low systemic toxicity • Short onset • Relatively hypoallergenic

5
What is the purpose of formulating local anesthetics as a hydrochloride salt?
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To enhance their stability in solution

6
What is the pKa range for local anesthetics?
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7.5-10

7
How does an acidic pH affect the efficacy of local anesthetics?
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shifts the equilibrium towards protonation → decreasing efficacy

8
what is the impact of inflammation on LA
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• tissue more acidic → incomplete anesthesia • vasodilation → rapid diffusion of LA away from site • infected tissues: increase risk of spreading infection

9
What are nociceptors and thermoreceptors and how do they function in pain transmission?
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Nociceptors and thermoreceptors are sensory receptors that detect pain and thermal stimuli, respectively. They activate when stimulated, generating an action potential and transmitting the signal to the somatosensory cortex through the dorsal horn of the spinal cord.

10
How do local anesthetics inhibit the conduction of action potential?
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• inhibits conduction of action potential in all afferent nerve fibers • blocking the sodium channels

11
What is the mechanism of action of local anesthetics?
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• prevent pain perception by binding to receptors and blocking sodium channels • stops sodium influx • prevents depolarization or action potential generation

12
What factors influence the onset of local anesthetic (LA) action?
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• Size and lipophilicity of LA • Smaller and more lipophilic LA = faster • Dissociation constant (pKa) of LA • Near physiological pH, more non-protonated form

13
What factors influence duration of LA
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• Protein binding; more = longer • vasodilator activity; more = diffusion = shorter

14
How does vasodilator activity affect the duration of local anesthetic action?
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Increased blood flow will increase diffusion, thus affecting the duration of action.

15
What is the anatomical proximity to the injection site?
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The distance from the injection site to the nerve fibers.

16
What is differential functional blockade?
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It refers to the varying susceptibility of nerve fibers to block local anesthetics • myelination • nerve diameter • tissue pH • vasoactivity • lipid solubility

17
WHat size axons are more susceptiple to LA
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smaller = more susceptible C and A-delta most susceptible

18
What is the function of Type A alpha fibers?
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Proprioception, motor

19
Which type of nerve fiber is most susceptible to local anesthetics?
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Type C

20
relation of ionization to onset
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increase in non-ionization = decrease in onset smaller pKa = shorter onset time

21
What is LAST
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Local anesthetic system toxicity

22
What are the initial signs of systemic toxicity in LAST?
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The initial signs include agitation, confusion, and dizziness.

23
What are the progression stages of LAST and their corresponding serum concentrations?
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• seizures at 10 ug/ml • coma at 15 ug/ml • respiratory failure at 20 ug/ml • cardiovascular collapse at >20 ug/ml

24
What is the most common cause of Local Anesthetic Systemic Toxicity (LAST)?
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Accidental intravascular injection during the administration of local anesthetics.

25
What is the importance of aspiration before every injection?
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To prevent accidental intravascular injection.

26
co-morbidity that can increase risk of local anesthetic overdose?
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Hepatic dysfunction

27
initial management steps for LAST
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Airway management, circulatory support, and calling for help.

28
medication administered by EMS to manage convulsions in LAST?
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Benzodiazepines

29
What is the lipid rescue treatment for patients exhibiting seizures or signs of CVS toxicity?
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20% Lipid emulsion (triglycerides and phospholipid) infusion.

30
Ester metabolization
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• metabolized in the plasma by pseudocholinesterase enzyme • yields para-aminobenzoic acid • Metabolites are eliminated via the kidneys

31
Examples of esters
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• benzocaine • procaine • chloroprocaine • tetracaine

32
How is benzocaine applied and what is its absorption rate?
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• mucous membranes as a topical anesthetic • poorly absorbed into the circulation.

33
Amide Local Anesthetics
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• Lidocaine • Mepivacaine • Prilocaine • Bupivacaine • Articaine

34
What is the primary organ for the excretion of metabolites?
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Kidneys

35
What is the range of elimination half-life for Amide LAs?
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20 minutes to few hours

36
Which Amide LAs can be suitable for patients with renal dysfunction?
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Those that undergo liver/plasma metabolism to inactive metabolites prior to excretion

37
What are the components of a dental cartridge (LA Solution)?
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• Local anesthetic agent • vasoconstrictor • reducing agent: Sodium metabisulfite • preservatives: Methylparaben. • Fungicide: Thymol. • Vehicle: distilled water, Standard volume is 1.8 ml

38
What is the pH range for LA with vasoconstrictors compared to LA without vasoconstrictors?
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• LA with vasoconstrictors: more acidic (3.5) • LA w/out vasoconstrictors: more basic (6.5)

39
What is the purpose of LA buffering in dental procedures?
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bringing the solution near the physiological pH by mixing w/ sod.bicarb. • To increase the onset of action • enhance patient comfort, acidity = pain

40
What does vasodilation cause in relation to LA
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• causes redistribution of local anesthetic • higher plasma concentration • decreased depth and duration of anesthesia at site • increased bleeding risk at injection site

41
What is the purpose of using vasoconstrictors with local anesthesia?
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To reduce bleeding and prolong the effect of local anesthesia.

42
vasoconstriction effects with in regards to LA injection
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• decreasing blood flow to the injection site • reducing local anesthesia redistribution • lowering the risk of systemic side effects • decreasing the risk of bleeding • increasing the duration of the anesthetic action

43
What are the effects of epinephrine on the cardiovascular system?
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Epinephrine increases cardiac output and blood pressure.

44
common epi drug-drug interactions
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tricyclic antidepressants nonselective beta blockers

45
What is the dilution of epinephrine used as a hemostatic reagent?
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1:50,000

46
What is the effect of increasing the concentration of epinephrine on the duration of local anesthesia?
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Increasing the concentration of epinephrine decreases the duration of local anesthesia.

47
Max dose of epi for a healthy subject?
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0.2 mg

48
Max dose of epi for a patient with severe cardiovascular disease (ASA III and IV)?
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0.04 mg

49
MRD for epi-sensitive individuals, ASA category III patients?
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40 μg per appointment

50
What is the effect of epinephrine on blood glucose levels in diabetic patients who do not use their hypoglycemic medication?
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Epinephrine may increase blood glucose levels.

51
What is glycogenolysis?
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The breakdown of glycogen into glucose.

52
What is Levonordefrin?
Show answer
A synthetic vasoconstrictor that mainly acts by α2 receptor stimulation.

53
How does Levonordefrin affect the heart and central nervous system?
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It has lower cardiac and CNS stimulation.

54
What is the dilution ratio of Levonordefrin when combined with mepivacaine?
Show answer
1:20,000

55
Which LAs are risk category B during pregnancy?
Show answer
Lidocaine and prilocaine

56
Which LAs are risk category C during pregnancy?
Show answer
Articaine Mepivacaine Bupivacaine

57
What is the mechanism of action of Phentolamine Mesylate (OraVerse)?
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It is an alpha-adrenergic antagonist that decreases local anesthetic duration by inducing vasodilation.

58
What are the indications for using a specific medication?
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• Reverse local anesthesia and soft tissue numbness • prevent self-inflicted soft-tissue trauma in children/patients w/ cognitive impairment

59
What is tachyphylaxis in the context of local anesthesia (LA)?
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• where nerve function returns before re-injection of LA, • leads to pain in the patient

60
How can tachyphylaxis be prevented?
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additional injections are administered before the full recovery of nerve function

61
What are GABA receptors and how do they work in the context of general anesthesia?
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• GABA: inhibitory neurotransmitters • when stimulated → induce general anesthesia by reducing neural activity

62
What are NMDA receptors and how do they relate to general anesthesia?
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• NMDA receptors: excitatory receptors • when blocked → MOA in general anesthetics in inducing anesthesia

63
What are the four goals of general anesthesia?
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Hypnosis, Analgesia, Amnesia, Muscle relaxation

64
What is the first stage of general anesthesia?
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Induction IV injection with propofol + neuromuscular blocker

65
What is the second stage of general anesthesia?
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Maintenance

66
What is the last stage of general anesthesia
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Recovery redistribution of anesthetics from the site