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Principles of Anesthetics

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Principles of Anesthetics Bucky Boaz, ARNP-C Background Carl Koller 1884 Freud colleague Eye surgery Background William Halsted 1885 Local injection of cocaine for ... – PowerPoint PPT presentation

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Title: Principles of Anesthetics


1
Principles of Anesthetics
Bucky Boaz, ARNP-C
2
Background
  • Carl Koller
  • 1884
  • Freud colleague
  • Eye surgery

3
Background
  • William Halsted
  • 1885
  • Local injection of cocaine for surgery
  • Nerve block

4
Background
  • 1905
  • Einhorn and Braun Procaine
  • 1930
  • Chlorprocaine
  • 1941
  • Nils Lofgren
  • Synthesized Xylocaine
  • Changed to lidocaine
  • 1884
  • Hall Dentistry
  • 1884
  • Zenfel Ear
  • 1890
  • Ritsert Benzocaine

5
Physiochemical Properties
Aromatic Segment
Hydrophilic Segment
Intermediate Chain
Amino-amine
Amino-ester
Esters
Amines
6
Physiochemical Properties
  • Amino-esters (Esters)
  • Older class of drugs
  • Derivatives of PABA (p-aminobenzoic acid)
  • Hydrolyzed by serum cholinesterase
  • Examples
  • Procaine (Novocaine)
  • Cocaine
  • Tetracaine
  • Benzocaine

7
Physiochemical Properties
  • Amino-amines (Amines)
  • Newer class of drugs
  • Derivatives of aniline
  • Hepatic degradation
  • Examples
  • Lidocaine
  • Bupivocaine (Marcaine, Sensoricaine, Polocaine)
  • Mepivocaine (Carbocaine)
  • Etidocaine
  • Prilocaine

8
Physiologic Basis
  • Prevention of sodium influx across the nerve
    membrane
  • Sufficient anesthetic present prevents firing
    threshold from being obtained
  • Prevents action potential from forming
  • No action potential, no impulse, therefore
    conduction blockade
  • End result is local anesthesia

9
Mechanism of Action
Lipid solubility Vasodilatation Tissue
pH Concentration of drug
Protein binding Vasodilatation Mode of
administration Presence of vasoconstrictor
Duration
Potency
Onset
Inherent pKa Myelination Interspersed
tissue Dosage of drug
10
Ideal Anesthetic
  • Immediate onset
  • Reversible
  • Appropriate duration
  • No permanent damage
  • No tissue irritation / pain
  • Wide therapeutic range
  • Effective regardless of application

11
Topical Anesthesia
12
Intact Skin
  • Epidermis
  • Avascular layer measuring 0.12 to 0.7 mm
  • Barrier to diffusion of topicals
  • Dermis
  • Support structure
  • Contains blood vessels and nerve endings
  • Anesthetics targeted site of action

13
Agents
  • Lidocaine Cream
  • EMLA
  • Ethyl Chloride

14
Uses
  • Intact skin procedures
  • Venopuncture
  • Punch biopsies
  • Lumbar puncture

15
Lidocaine Cream
  • 30 lidocaine cream
  • Saturated on gauze pad adherent to an elastic
    patch
  • 45 minutes minimum application time
  • ½ hour anesthetic duration 2 hour application
  • Effective and safe, but not practical

16
EMLA (Eutectic Mixture of Local Anesthetics)
  • 2.5 lidocaine and 2.5 prilocaine
  • 1-hour application time
  • Maximum dose at 2-3 hours
  • Depth of anesthesia correlated to duration of
    application
  • Duration of 1-2 hours after removal
  • Hypersensitivity and systemic toxicity rare

17
Ethyl Chloride (C2H5CL)
  • Not an anesthetic, but a vapocoolant
  • Immediate anesthesia, but limited duration
  • Spray for 3 to 7 seconds
  • Used for injections and lancing small abscesses
    or boils
  • Not used for punch biopsies

18
Mucous Membranes
  • Nose, mouth, throat, tracheobronchial tree,
    esophagus, and genitourinary tract

19
Agents
  • Tetracaine
  • Lidocaine
  • Cocaine
  • Benzocaine

20
Tetracaine
  • Effective and potent agent
  • Long duration of action
  • Downside high toxicity
  • Maximum adult dose of 50mg

21
Lidocaine
  • 2 solution
  • Swished inside the mouth then expectorated
  • 5 liquid
  • Applied with a swab
  • 5 ointment
  • Applied with a sterile gauze pad

22
Lidocaine
  • Indicated for painful, irritated, or inflamed
    mucous membranes of the mouth
  • 2 good for aph-thous stomatitis and as adjunct
    before infraoral nerve block
  • 5 ointment good for reducing pain during oral
    injection

23
Lidocaine
  • Precautions
  • Impaired swallowing
  • Numbness of the tongue
  • Expectorate excess to avoid toxicity

24
Cocaine
  • Topical preparations available in 4 and 10
    solutions and viscous formulations
  • Safe dose of 200mg (2 to 3 mg/kg)
  • Apply for 5-6 minutes
  • Works by vasoconstriction
  • Coronary vasoconstriction with 2mg/kg applied to
    the nasal mucosa

25
Benzocaine
  • Available in 14 to 20 liquid, gel, or spray
  • Used to relieve pain in canker sores, cold sores,
    other minor inflammation
  • Very short duration and more allergenic
  • Can be used prior to infraoral nerve block

26
Ophthalmic Anesthetics
27
Agents
  • Proparacaine
  • Tetracaine

28
Proparacaine
  • 0.5 solution
  • Indicated for removal of superficial foreign body
  • 1 to 2 drops before procedure
  • Onset within 30 seconds
  • Duration 15 minutes
  • Have patient avoid touching eye

29
Tetracaine
  • 0.5 solution
  • Onset, duration, and potency similar to
    proparacaine
  • Burning sensation worse and longer

30
Lacerations
31
TAC
  • TAC (tetracaine-adrenalin-cocaine)
  • Used to anesthetize lacerations in children
  • Wounds lt 5cm
  • Vasoconstrictor
  • More effective on face and scalp

32
TAC
  • Advantages
  • Disadvantages

33
Agents and Effectiveness
  • 0.5 tetracaine, 12000 epinephrine (adrenalin),
    and 11.8 cocaine
  • Epinephrine 12000, cocaine 11.8
  • Tetracaine 0.25, epi 14000, cocaine 5.9
  • Tetracaine 1.0, epi 14000, cocaine 4
  • Lidocaine 4.0, epi 11000, tetracaine 0.5
  • Gel by adding 0.15g methylcellulose to 1.5ml of
    epi and cocaine solution

34
Application
  • Fill wound with TAC solution
  • After 3 minutes, instill saturated gauze or
    cotton into wound
  • Leave in place 15-20 minutes
  • SAFE dose maximum
  • Full strength TAC 0.09 ml/kg
  • Tetracaine 50mg, cocaine 150-300mg

35
Adverse Reactions
  • Can lead to systemic toxicity from mucosal
    application
  • Gel form reduces runoff
  • Ischemic complications

36
Precautions
  • Avoid in
  • CAD
  • Uncontrolled HTN
  • Seizures
  • PVD
  • Risk of Toxicity

37
Infiltration Anesthesia
  • Injection of anesthetic agent directly into tissue

38
Indications
  • Excision of skin lesions
  • Incision of abscess
  • Suturing of wounds

39
Advantages Disadvantages
  • Advantages
  • Quick and safe
  • Provides hemostasis
  • Disadvantages
  • Large dose for small area
  • Distorts wounds

40
Choice of Agent
  • Lidocaine 0.5 to 1.0
  • Procaine 0.5 to 1.0
  • Bupivacaine 0.25

41
Choice of Agent
42
Choice of Agent
  • Prolong duration by adding
  • Epinephrine
  • Sodium bicarbonate
  • Both
  • Use bupivicaine

43
Epinephrine Use
44
Injection Technique
  • Bicarbonate
  • Reduces pain of injection
  • Mechanism unclear
  • 1 cc 8.4 bicarb 9 cc lidocaine
  • Neut 4.2 bicarb (1cc4cc)
  • Precipitates in bupivicaine
  • Shelf life 1 wk (unref), 2 wks (refr)

Bartfield JM, et al Buffered lidocaine as a
local anesthetic An investigation of shelf life.
Ann Emerg Med 2124, 1992.
45
Comparison of 1 Lidocaine (L) and 0.25
Bupivacaine (B)--Infiltration Anesthesia
46
Injection Technique
  • Lowest concentration effective
  • Prep wound first if possible
  • Smallest needle available (27g)
  • Use wound margin
  • Subdermal injection
  • Insert, then inject

47
Injection
  • Injection should be subdermal
  • Bury the hub and inject as you withdraw
  • Through wound edge

48
Injection Technique
  • Warming
  • No change in efficacy
  • Less pain of injection
  • Probably synergistic with buffering

Brogan GX, et al Comparison of plain, warmed
and buffered lidocaine in wound repair. Ann
Emerg Med Aug. 1995.
49
Complications
  • Effects on wounds
  • Systemic toxic reactions
  • Catecholamine reaction
  • Allergic reactions

50
Effect on Wounds
  • Wound healing
  • Wound strength
  • Avoid in poor healing wounds
  • Help prevent keloids
  • Wound infection
  • Local injuries

51
Systemic Toxic Reaction
  • High Blood Levels
  • Site and mode of administration
  • Rate
  • Dose of Concentration
  • Addition of epinephrine
  • Specific drug
  • Clearance
  • Maximum safe dose
  • Inadvertent intravascular injection

52
Maximum Dosage - Lido
  • Without epi
  • 4.5 mg/kg
  • 70 kg 300 mg
  • 30 cc (1 ½ bottles) of 1
  • 15 cc (3/4 bottle) of 2
  • With epi
  • 7 mg/kg
  • 70 kg 500 mg
  • 50 cc (2 ½ bottles) of 1
  • 25 cc (1 ¼ bottles) of 2

53
Lidocaine
  • Dosage administered Packaging ( g / dl)

1 20 cc
2 20 cc
4 20 cc
1 g/dl 1000mg/100cc 10 mg/cc 200 mg/bottle
2 g/dl 2000mg/100cc 20 mg/cc 400 mg/bottle
4 g/dl 4000mg/100cc 40 mg/cc 800 mg/bottle
54
Systemic Toxic Reaction
  • Host Factors
  • Hypoxia
  • Acid-base status
  • Protein binding
  • Concomitant drugs

55
Catecholamine Reaction
  • Excess levels produce

56
Adverse Effects - Systemic
But Im allergic to the numbing medicine
Great, now what?
57
Adverse Effects - Systemic
  • Allergic reactions
  • 1 2 of total adverse reactions
  • Esters
  • Large majority
  • PABA
  • Amides
  • Rare
  • methlyparaben

58
Allergic Reactions
  • Fisher,et al
  • Anesthetic allergy clinic
  • 208 patients with allergy to local anesthetic
    over 20 year period
  • Intradermal testing
  • 4 immed, 4 delayed
  • 39 to additives

Fisher MM, Bowie CJ Alleged Allergy to Local
Anesthetics Anaesth Intensive care 1997
Dec25(6)611-4
59
Allergic Reactions
  • Recommendations
  • 1. Define allergy vs. adverse rxn
  • 2. Alternate class of anesthetics
  • 3. Cardiac lidocaine
  • 4. Test dose (0.1 cc SQ)
  • 5. Diphenhydramine

60
Allergic Reactions
  • Diphenhydramine
  • Supplied as 5 solution (50 mg/cc)
  • Tissue necrosis
  • Must be diluted in NS
  • 1 cc / 4 cc NS 50 mg / 5 cc 1
  • 1 cc / 9 cc NS 50 mg / 10 cc 0.5

61
Allergic Reactions
  • Diphenhydramine
  • 24 volunteers
  • DPH 1 as effective as Lido 1
  • Injection more painful
  • Safety profile not well established

Green SM, Rothrock SG, et al Validation of
diphenhydramine as a local anesthetic. Ann Emerg
Med June, 1994.
62
Allergic Reactions
  • Diphenhydramine
  • 98 patients
  • DPH 0.5 vs. lidocaine 1
  • No difference in pain of injection or efficacy,
    except face

Ernest AA, et al. Lidocaine vs. diphenhydramine
for laceration repair . Ann Emerg Med Jun,
1994.
63
Allergic Reactions
  • Diphenhydramine
  • Dbl blinded
  • 2 cc of Lido 1 vs. DPH 1
  • 10 adult volunteers - pinprick
  • Conclusions
  • No differences to 30 minutes, Lido better after
    30 min
  • Duration Lido (81 min) vs. DPH (42 min)
  • 1/10 developed skin necrosis

Dire DJ. Double blinded comparison of lidocaine
vs. diphenhydramine as a local anesthetic. Ann
Emerg Med. 1993 22(9) 1419-1423.
64
Allergic Reactions
  • Recommendations
  • 6. Normal saline
  • 7. No anesthesia
  • 8. Parenteral agents
  • 9. General anesthesia
  • 10. Nitrous oxide
  • 11. Benzyl alcohol

65
Points to Remember
  • Esters and Amines
  • Factors affecting MOA
  • Types of anesthetics
  • How applied
  • Risks and Benefits
  • Contraindications
  • Adverse reactions

66
Questions?
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