Big Flabby Text-Only Outlines
DEHY34: Pharmacology for Dental Hygienists
Who to blame and contact: Jim Middleton, Instructor
Module Six: Local and General Anesthesia 
By the completion of this section, the participant shall be able to:
 1. Describe the mechanism of action of local anesthetics
 2. Differentiate between the three major categories of local anesthetics
 3. Identify crossover allergies between local anesthetic agents and discuss their clinical significance
 4. Differentiate between a drug allergy and a panic reaction
 5. Understand the effect of physiological pH on the activity of injected local anesthetics
 6. Discuss the effect of inflammation on the effectiveness of a local anesthetic
 7. Describe the action of epinephrine when added to local anesthetics
 8. Discuss the clinical significance of epinephrine entering the bloodstream when used as part of the local anesthetic.

I. Background
    A. These are the most often used drugs in dental practice
    B. Indication–reduce pain and discomfort during a dental procedure
    C. Mechanism of action
  --interfere with the movement of sodium through the pores of the neuronal membrane
  --without the movement of sodium, the nerve’s ability to depolarize for a new signal is taken away, and the conduction of the nerve impulse is lost
        --therefore, pain signals are lost
QUESTION TIME
 The mechanism of action of local anesthetics is to
   a. block nerve synapes
   b. coagulate nerve protein reversibility
   c. depolarize persistently the nerve membrane
   d. block nerve conduction by preventing nerve depolarization

Or, to put it in another way:

 Local anesthetics produce their primary effects by
   a. inhibiting inflammation
   b. blocking nerve conduction
   c. constricting blood vessels
   d. depressing the reticuloactivating system (RAS)


 D. Dental application
  1. topical--anesthesize the nerve at the site
  2. infiltration--as above, affecting smaller nerves
  3. nerve block--numb an area affecting a series of nerves which then numbs the areas those nerves serve

E. Primary action is localized
       --produce loss of sensations of
        1. pain
        2. temperature
        3. touch

 F. Chemistry considerations
  1. remember our body's pH, an indicator of acid/base environment (under 7 is acidic, 7 is neutral, over 7 is basic)
  For example:

  acids: vinegar, hydrochloric acid, sulfuric acid
  bases: sodium hydroxide (aka LYE), soaps
    --physiological pH=7.4 (slightly basic)

  2. local anesthetics are weak bases (pH > 7)
  3. at tissue pH, the anesthetic is partially nonionized; it is in this form that it is able to penetrate the nerve tissue
  (of course you recall this from our earlier lectures dealing with lipid solubility and nonionized forms of drugs)
  4. in the presence of tissue inflammation, the tissue pH is lowered (pH <7, representing an acidic environment)
  5. in an acidic environment, a basic drug is more highly ionized
  6. therefore, if the anesthetic exists in a more highly ionized state, less of it will be able to penetrate the nerve tissues
  7. less penetration-- less effect-- less anesthesia


 An infection in an area can prevent the accumulation of effective concentrations of local anesthetic solution because of
   a. low tissue pH
   b. excessive dilution with tissue fluids
   c. the intense stimulation of pain due to the infection
   d. rapid absorption of the solution into the systemic circulation

II. IMPORTANT CONSIDERATIONS IN LOCAL ANESTHESIA
 A. Characteristics of an ideal local anesthetic
  1. good and reversible anesthesia
  2. no allergic, local, or systemic side effects
  3. penetrate tissues easily
  4. stable in solution
  5. stable for sterilization (ie, by autoclave)
  6, Low cost (life is an HMO)
  7. Ease of metabolism and excretion

QUESTIONS
Use of a topical anesthetic spray is limited by which of the following disadvantages?
   a. it is difficult to control the quantity administered
   b. it is difficult to confine the effect to a small area
   c. sufficient amounts could be inhaled to cause a toxic reaction
   d. larger amounts are needed than with a topical solution

Topical anesthetic agents are most effective when applied to
   a. skin
   b. palatal mucosa
   c. keratinized epithelium
   d. nonkeratinized soft tissue
   e. areas of acute inflammation


 B. Loss of nerve function in this order
  1. autonomic
  2. cold
  3. warmth
  4. pain
  5. touch
  6. pressure
  7. vibration
  8. proprioception (position)
  9. motor

 C. Toxicity
         1. local anesthetics are very safe when properly used
         2. problems more likely with children or the elderly
         3. POSSIBLE PROBLEMS WITH allergy or when vasoconstrictors being used
   --allergy can be due to anethetic or preservatives present (methylparabens)
         4. CNS stimulation if systemic absorption
             --excitement, tremors, convulsions
   --can be followed by CNS depression; cardiovascular depression, unconsciousness
  5. allergic reactions--ester type of anesthetic
  6. panic reactions--"fainting as the result of the injection procedure is...not due to the pharmacological effect of the drug, but is a psychological response to the fear or pain of injection..."


QUESTION TIME
A patient states "I'm allergic to Novocaine."  When questioned further, he describes his experience as "shortness of breath, palpitations, cold perspiration and fainting for a few moments."  From this information the dental hygienist should suspect that the patient is
   a. a drug addict
   b. apprehensive about receiving dental care
   c. likely to experience anaphylactic shock if injected with Novocaine
   d. suffering from an undiagnosed systemic disturbance and should be referred to a physician for consultation

  7. malignant hyperthermia--
   --a syndrome where the patient has a reaction to the anesthetic and develops a potentially fatal elevated body temperature
   –genetic predisposition, an autosomal dominant gene
   –mortality rate is 50%
   –treated with dantrolene sodium (Dantrium) and a quick trip to intensive care
   –halothane and succinylcholine are the most often implicated

     D. Precautions
      1. take a careful history
      2. aspirate before injection
            --draw back on syringe to check for blood return; if you get blood, you've hit a vessel and should try again! Yikes!
      3. use the least amount necessary
      4. inject slowly
      5. avoid repeated injections into the same area
            -decreased blood flow to area ?  edema ?  tissue damage ? delays in healing (due to oxygen deprivation)
      6. of the local anesthetics, sources indicate lidocaine is the best choice; concern is with fetal bradycardia


QUESTION
The effective use and application of a topical anesthetic solution is dependent on
   a. a review of the patient's history
         To determine allergies
   b. an explanation of the procedure to the patient
         To allay fear and apprehension
   c. a generous application to a large surface
         Icky-bad idea--can result in sensitization to the local anesthetic
   d. application to a surface that is dried with a gauze sponge or cotton roll
         A dry surface is an absorbant surface
   e. performance of clincial services immediately after application
         All good things take time, especially local anesthesia...

III. SPECIFIC AGENTS
(this represents an unfortunate turn for those who dislike memorization; for your national boards, you will have to know these names and be able to differentiate them both by type of anesthetic and by trade/generic name)
--there are three broad classifications for local anesthetics, based on chemical structure
--if your patient has an allergy to one of the esters, he/she will probably have an allergy to the other esters
–amides have a far lower allergy potential and do not seem to be subject to crossover allergies
 CHART OF LOCAL ANESTHETICS

AMIDES                            ESTERS                      MISCELLANEOUS
bupivicaine (Marcaine)         benzocaine                  dyclonine (Dyclone)
lidocaine (Xylocaine)           cocaine                        diphenhydramine (Benadryl)
mepivacaine (Carbocaine)   procaine (Novocaine)
prilocaine (Citanest)            propoxycaine (Ravocaine)
etidocaine (Duranest)          tetracaine (Pontocaine)
chloroprocaine (Nesacaine)

Note: etidocaine (Duranest) is used primarily for central nerve block or lumbar procedures

    A. Classifications
        1. amides
        2. esters
        3. miscellaneous

    B. Amides
        1. lidocaine (Xylocaine, also known as “Nervocaine” or “Dilocaine”) –since 1948
           a. topical, infiltration, nerve block
           b. most frequently used anesthetic
           c. more toxic than procaine with long-term use, but this is not a problem at dental concentrations
           d. has vasodilatory effect; often has epinephrine added in 1:100,000 or 1:200,000 concentrations WHY WHY WHY WHY WHY would you add epinephrine?


QUESTIONS
The action of epinephrine when combined with a local anesthetic is to
   a. increase the amount of local anesthetic needed for effect
   b. decrease the relative length of action of an anesthetic
   c. enhance circulation and wash the anesthetic from the site of action more quickly
   d. increase the duration of anesthesia

When a local anesthetic containing epinephrine is mistakenly injected into a blood vessel, the patient could demonstrate
   a. watery saliva
   b. bradycardia
   c. an elevation in blood pressure
   d. contraction in the muscles of mastication

   e. lidocaine comes in sterile 1%, 1.5%, 2% solutions for injection
    –topical 5% ointment, patch (maximum effect after 10 minutes), 10% spray, 2% viscous solution (2-3 minute onset of action)
            f. IV use is reserved for cardiac arrhythmias (more with our discussion on cardiac emergency drugs)
            g. duration of lidocaine anesthesia
                i. 2% solution – infiltration and block
                   pulpal anesthesia 5-10 minutes
                   soft tissue anesthesia 1-2 hours

                ii. with epinephrine
                    pulpal: 60-90 minutes
                    soft tissue: 2-4 hours

            h. may cause some sedation, positional headache, and shivering
 
        2. mepivacaine (Carbocaine) –since 1960
            a. equal to lidocaine in potency, but not effective topically
            b. no sedation, no vasodilation properties
            c. 3% solutions
                pulpal anesthesia: 20-40 minutes
                soft tissue: 2-3 hours
            d. Carbocaine brand does not use parabens as preservatives (consider patient allergies)
            e. levonordefrin (Neo-Cobefrin) is the vasoconstrictor used here as an alternative to epinephrine, at a 1:20,000 dilution
 
        3. prilocaine (Citanest, Citanest Forte)
            a. more rapidly metabolized
            b. less toxic; higher concentrations possible, anesthesia is slightly longer
            c. methemoglobinemia possible but rare; consider patients taking hefty doses of acetaminophen – methemoglobinemia is reversed by IV administration of methylene blue
            d. in 4% solutions, with or without epinephrine 1:200,000

        4. bupivacaine (Marcaine)
            a. structurally, related to mepivacaine
            b. noteworthy for long duration of action – useful for procedures requiring more than 1.5 hours
            c. minimizes need for analgesics
            d. 0.5% solution
             e. problems
                i. more toxic than lidocaine
               ii. beware of intravenous infiltration
               iii. long duration of action can increase danger of tissue laceration among children or the mentally handicapped

      5. etidocaine (Duranest)
               For central nerve block or lumbar procedures

      6. ropivacaine (Naropin) –relatively new, used primarily for epidural blocks; not in dentistry

    C. ESTERS
  --all are derivatives of para-aminobenzoic acid (PABA), except for cocaine; can interfere with antibacterial effects of the sulfonamide class of antibiotics
        --produce allergic type reactions more often than the amides
        --the first collection of local anesthetics – NOT available in dental cartridge formats

        1. procaine (Novocaine)
            a. to the lay-public, the term "novocaine" has become synonymous with local anesthesia (biggie from 1905-1950)
            b. important during drug history to determine the exact allergy
            c. least toxic, not effective topically
            d. max. dose: 20ml of a 2% solution

        2. propoxycaine (Ravocaine)
             a. very potent, but very toxic
             b. not used alone
             c. propoxycaine sometimesmixed with procaine
             d. propoxycaine sometimes recommended when amides are contraindicated

3.  tetracaine (Pontocaine)
         a. very potent, very toxic
         b. very effective topically
               --2% solution--
         c. best not used on abraided tissues
         d. once  mixed with procaine

4. benzocaine, or "ethylaminobenzoate"
           a. topical use only
           b. benzocaine and tetracaine can sensitize patients to the ester-class of anesthetics and can potentiate the possibility of allergic reactions
           c. used in ointments and powders

5. chloroprocaine (Nesacaine)
 –alternative to procaine, in 2% solutions

6.  cocaine
     a. CNS stimulant
     b. very EFFECTIVE topically
     c. an alkaloid from the coca plant
     d. a controlled substance--CII
 In spite of its greater renown as a drug of abuse, cocaine is an excellent topical local anesthetic and can be legally prescribed.


Cocaine addiction has recently been associated with dopamine accumulation.  Dopamine is a neurotransmitter that is important in those parts of the brain which control pleasure responses.  Like most synapses, there are salvage mechanisms for the unused dopamine that gets released.  Cocaine blocks the uptake of excess dopamine, increasing the effects on the pleasure center neurons.
In 1988, the National Institute for Drug Abuse estimated that 35-40 million Americans had tried cocaine in one form or another; in South America, native Indians use the coca leaf, obtaining the equivalent of 400mg of cocaine in 50 grams of leaves.  Ironically, this generally malnourished population may actually derive some benefit from chewing the leaves–they contain high doses of vitamin C, B1, and riboflavin, helping prevent scurvy in regions where fresh fruit and vegetables are in short supply.

 D. MISCELLANEOUS: neither amide nor ester
        1. dyclonine (Dyclone) –presently, not commercially available
            a. may be useful if allergies to other two classes
            b. slow anesthesia: up to 10 minutes before effects seen
            c. duration: l hour
            d. 0.5% solution; maximum dose: 200mg
 
 A quick sidebar note here as well:
On rare occasions, when the patient has demonstrated sensitivity to the usual collection of local anesthetics, anesthesia is obtained by diphenhydramine (Benadryl) injection.  Diphenhydramine is an antihistamine but has this ability to produce local anesthesia.  A 1% concentration is used, combined with a 1:100,000 dilution of epinephrine–NO COMMERCIALLY AVAILABLE PRODUCT OFFERS THIS COMBINATION

IV. Topical applications/considerations
    A. Uses
        1. before infiltration or block to reduce the pain of injection
             --affects primarily surface tissues
         2. used to numb oral wounds or ulcers
         3. care with abraided tissue to prevent systemic absorption
         4. may be used to reduce the "gag" reflex
             --beware of possible aspiration
               –oral cough capsules benzonatate (Tessalon Pearles)

         5. topical solutions may be useful in
             --suture removal
             --before probing
             --root planing, scaling
             --gingival curettage
             (if injection not used)
         6. lidocaine, benzocaine, dyclonine are less toxic on abraided tissue
         7. beware of sensitization


QUESTIONS
Use of a topical anesthetic spray is limited by which of the following disadvantages?
   a. it is difficult to control the quantity administered
   b. it is difficult to confine the effect to a small area
   c. sufficient amounts could be inhaled to cause a toxic reaction
   d. larger amounts are needed than with a topical solution

The drug of choice for immediate treatment of an anaphylactic reaction of a local anesthetic is
   a. morphine
   b. thiopental
   c. epinephrine
   d. pentobarbital
   e. diphenhydramine (Benadryl)


 B. Storage considerations
        1. chemical changes will turn solution pink to brown
         2. expiration date
         3. get a policy on how long to use a multiple dose vial after the "first entry"
         4. intact multiple dose vial a mandate!

V. The issue of epinephrine
 A. The “dilution” phrasing
  what is “1:100,000" anyway?
   1:100,000 is an ancient means of presenting a solution’s concentration; here, it represents g:ml, or specifically, 1gram in 100,000ml solution.
   1:200,000 is 1 gram in 200,000ml solution
   1:50,000 is 1 gram in 50,000ml solution, etc.

 B. The clinical significance of systemic absorption of epinephrine
  1. 0.5mg, 1mg, are therapeutic doses used in emergency situations
  2. a 1:100,000 dilution contains 0.018mg in a 1.8ml cartridge
           10 dental cartridges contain less than ½ the therapeutic dose of epinephrine as used in emergency situations
  3. a patient can produce endogenous epinephrine far in excess of that administered in dentistry
  4. however, still use care in patients
       a. uncontrolled hypertension
       b. hyperthyroidism
       c. angina pectoris
       d. heart attack or stroke patients within 6 months of the event

 GENERAL ANESTHESIA: CONCEPTS AND AGENTS

By the completion of this section, the participant shall be able to:
 1. Describe the concept of "partial pressures"
 2. Understand the stages of general anesthesia
 3. Understand the concept of diffusion hypoxia
 4. Describe the function of "double gas" effect
 5. Identify an agent used to reduce secretions during surgical procedures
 6. Identify both the absorption and excretion site for general anesthetics

I. Introduction
    A. What is this general anesthesia, anyway?
        1. anesthesia:  without sensation
        2. general anesthesia: without sensation and without consciousness
    --can go from mild sedation to sedation, sleep, unconsciousness, coma, and ultimately, death
 
    B. Objectives of general anesthesia
        1. abolish pain completely
        2. elimate awareness to elimate fears and anxieties
        3. prevent undesired reflex actions
           (consider hiccoughs during ophthalmic surgery)
        4. muscle relaxation

        --sometimes to reach these objectives, multiple agent use is necessary
 
    C. When to use?
        1. consider locale, liability
        2. anethesiologist

II. Inhalation anesthesia
     A. Pharmacology
          1. absorption site: the lungs

          2. excretion site: the lungs

          3. Concept of partial pressures
             a. "the pressure exerted by each gas "
             b. or, the pressure of diffusion
             c. depends on the number of molecules of the gas that are present, or, simply, the concentration of the gas

  4. Partial pressures and effect on anesthesia
             a. anesthetic is absorbed like crazy at first WHY?
                --consider diffusion and equilibrium
                --effect of high concentration induction

              b. the anesthetic will continue to move from compartment to compartment until equilibrium is obtained
 

             INSPIRED AIR--  LUNG -- BLOODSTREAM ---   BRAIN

 B. More terms
  1. DOUBLE GAS EFFECT
           a. two inhalation gases used
           b. one is potent, in low concentrations
              one is weak, in high concentrations
           c. recall that absorption is based on concentration of the gas
           d. therefore, when the low potency, high concentration gas is administered, it drags more of the potent gas with it
           e. the potent gas alone, in low concentrations, would not be absorbed as well

       2. DIFFUSION HYPOXIA
           a. happens when anesthetic is removed suddenly, without oxygen supplementation
           b. recall anesthetic flow in body compartments
           c. diffusion is based on concentration
           d. equilibrium must be maintained
           e. flow of anesthetic is reversed; agent leaves bloodstream and fills lungs
           f. oxygen is forced out--HYPOXIA!!

       3. ANESTHETIC STRENGTH
           a. potent anesthetics (ether)
               i. due to potency, must give in reduced amounts
               ii. BUT in reduced amounts, you have less partial pressure, therefore--

               iii.induction concentrations (those amounts necessary for the induction of anesthesia) cannot be maintained due to potential for saturation
               iv. "emergence" is also prolonged

          b. weak anesthetics (nitrous oxide)
               i. high concentrations required, high partial pressures
               ii. must approach 100% concentrations to produce full anesthesia, but hey! you gotta breathe, too!
               iii. due to high pressure, induction and emergence are both rapid

III. PROBLEMS WITH TOXICITY
    A. Cardiac arrhythmias
       --usually involve concurrent administration of epinephrine

   B. Malignant Hyperpyrexia
        1. high fever of unknown origin
        2. acidosis
        3. high serum potassium levels
        4. muscle contractions
        5. may be an inherited trait
        6. treatment is with dantroline (Dantrium) IV

    C. Personnel (that's you, the healthcare professional)
        1. long term contact
        2. increased chances for cancer, liver and kidney disease
        3. ventilation, disposal systems–big considerations


QUESTION
Long term exposure to low doses of nitrous oxide has been shown to increase the incidences of
 a. myeloneuropathy
 b. multiple sclerosis
 c. spontaneous abortion

IV. STAGES OF GENERAL ANESTHESIA
    ---these levels refer to ether in particular, an agent so well studied since its first use in the 19th century that its effect can be carefully predicted

 A. Stage I:  Analgesia
 B. Stage II: Delerium
 C. Stage III: Surgical anesthesia
  1. plane 1: light surgical anesthesia
  2. plane 2: moderate
  3. plane 3: deep surgical anesthesia
  4. plane 4: respiratory and circulatory collapse
   (polite term for death) not really desired

V. The particular agents
    A. Nitrous Oxide "laughing gas"
        1. light analgesia, light sedation
        2. used with local anesthetic because analgesia with nitrous oxide alone is incomplete
        3. must co-administer oxygen
            a. 80% nitrous oxide, 20% oxygen for induction
            b. 65% nitrous oxide, 35% oxygen for maintenance

        4. releases endorphins in the CNS (remember those?)

        5. nonflammable, nonirritating, "pleasant" smell

        6. additional benefits for stress patients

        7. Adverse effects
            --n/v, disorientation, dizziness
            --allow time after procedure for observation for residual effects
 
        8. Requires patient cooperation: communication essential!
    --consider the patient population least cooperative in these situations
 
 Of the following, nitrous oxide-oxygen analgesic is contraindicated in a patient who
   a. is overweight
   b. has hypertension
   c. has a history of emphysema
   d. has an upper respiratory infection
   e. has just ingested a large meal

The greatest danger in using nitrous oxide for analgesia is
   a. hyperventilation
   b. a gas embolus
   c. oxygen deprivation
   d. cardiac arrhythmia
   e. foreign body aspiration
 
  9. Other random comments on nitrous oxide
   –effective in management of general anesthesia up to Stage I
   –often abbreviated “N2O”
   –least toxic, may be used in children
   –good analgesia, also possesses anxiolytic effects
   –some random disadvantages:
   Misuse potential, can reduce fertility in women, analgesia is usually incomplete, nausea is the most common complaint, contraindicated in first trimester, and that includes dental office personnel (see sample question on chronic exposure to nitrous oxide)

    B. Ether/chloroform
        1. historical significance only--fencing mask
        2. very flammable, explosive, irritating to tissues
        3. induction is slow

    C. Halothane (Fluothane)
        1. potent, rapid induction (3%)
           --0.5-1.5% for maintenance
        2. used in combination
        3. can sensitize heart to amines (ie, epinephrine)
        4. considered good choice among asthmatics (less irritation)--also nonflammable
        5. metabolites have been implicated in liver damage

    D. Methoxyflurane (Penthrane)
        1. nonflammable, nonirritating
        2. slow induction
        3. sensitizes heart to amines, too
        4. metabolites yield fluorine, so beware of accumulation

    E. Enflurane (Ethrane)
        1. rapid induction
        2. good analgesia and muscle relaxation
        3. only mild sensitization of cardiac tissues to amines

VI. INTRAVENOUS ANESTHETICS
    A. Ultrashort acting barbiturates (recall lecture on anxiety and depression)
        --instantaneous, smooth induction, recovery also rapid

        1. thiopental (Pentothal sodium)
            a. poor muscular relaxation, analgesia
            b. coughing possible
            c. addition of atropine in order to:


QUESTION:
The cause of death from overdose of any central nervous system depressant is usually
   a. renal failure
   b. thromboembolism
   c. hepatic necrosis
   d. respiratory depression
   e. cardiovascular depression

  2. methohexital (Brevital sodium)
            --very similar
 
ADJUNCTIVE DRUGS FOR GENERAL ANESTHESIA
 A. Why?
  1. supplement lacking characteristics of the anesthetic
        2. improve safety
        3. increase patient "comfort" or surgeon’s “predictable outcome”

 B. Preanesthetic sedation
  1. if patient on sleeper already, the notion is to continue with that sleeper
        2. consider patient tolerance
       3. patients are awakened on occasion to get their sleeping pills (yes, it really happens!)
           --anesthesiologist wants a guaranteed response

    C. Drug categories used
        1. sedative-hypnotics
            a. benzodiazepines
               --flurazepam (Dalmane), temazepam (Restoril)
 
           b. long acting barbiturates
               --secobarbital (Seconal), pentobarbital (Nembutal)
 
           c. chloral hydrate
               --for children (liquid and suppository form) and the elderly

        2. antihistamines
            --sedate and offer antiemetic and antihistaminic effects
            a. promethazine (Phenergan)
            b. hydroxyzine (Vistaril)
            c. doperidol (Inapsine)
 

        3. diazepam (Valium), midazolam (Versed), lorazepam (Ativan)
            --muscle relaxation, sedation, amnesia

        4. narcotics (meperidine, morphine)
            a. post-operative analgesia
            b. sedation
            c. problems:
                i. may increase n/v post-op (morphine and the CTZ)
                ii. respiratory depression

    WHAT ANTAGONIST IS USED IN THIS SITUATION?

        5. anticholinergic drugs
           a. atropine
            b. scopolamine
            c. glycopyrrolate (Robinul)
            d. why?
                i. decrease secretions
               ii. prevent bradycardia
                 (a) due to procedure
                  (b) due to anesthetic (halothane)
                   (c) due to neuromuscular blockade (succinyl choline)


QUESTION
Which of the following is NOT a reason to premedicate patients before induction of general anesthesia
   a. relieve anxiety
   b. prolong induction
   c. prevent adverse effects of the anesthetic agent
   d. potentiate or supply an effect not produced by the anesthetic
   e. shorting duration of anesthesia from a single injection

 D. Neuromuscular blockade
        1. reasons
            a. anesthetics can provide some muscular relaxation, but usually only at toxic doses
            b. neuromuscular blockade provides good skeletal muscle relaxation
            c. neuromuscular blockade also relaxes certain respiratory muscles as well--assisted ventilation (breathing) required
 
        2. activity of these agents has been known for some time-- tubocurarine is the basic ingredient of the poison darts of Tarzan/Indiana Jones movies fame

        3. specific agents
            a. succinylcholine
              duration of action 5-10 minutes
              consider effects of liver damage; apnea possible
            b. d-tubocurarine (Tubarine)
              duration 20 minutes
              hypotension a contraindication (will worsen)
            c. gallamine and pancuronium
              can produce tachycardia and hypertension

VIII. DISSOCIATIVE ANESTHESIA
 "patient feels unrelated to the environment, analgesia and amnesia are good but muscle relaxation is poor"
      --causes disaggreeable dreams and hallucinations
      --ketamine

IX. INTRAVENOUS SEDATION
     A. patient remains awake and cooperative
     B. popular for outpatient procedures
     C. drugs
        1. diazepam (Valium), midazolam (Versed), lorazepam (Ativan)
         2. may be combined with an opioid (meperidine, morphine)

     D. Neuroleptanalgesia
        1. combines a major tranquilizer with an opioid
         2. Innovar is the most often used
             combines
             a. droperidol (Inapsine), a butyrolphenone (like Haldol)
             b. fentanyl (Sublimaze), a short-acting IV opioid
         3. extrapyramidal symptoms (Parkinsonism like syndromes) possible

X. PROBLEMS WITH ANESTHETICS/PATIENT CARE
    A. Loss of protective mechanisms for survival
       --suppression of cardiovascular and respiratory systems
    B. Special care with these patients
        1. circulatory abnormalities
        2. respiratory deficiencies
            --atelectasis possible (lung collapse)
        3. kidney disease
            --avoid methoxyflurane
            --avoid gallamine and pancuronium
        4. liver disease
            --volatile anesthetics may worsen
            --liver impairment can increase the duration of action of succinylcholine
 
     C. Complete medical history
     D. Watch for recovery


QUESTION:
Which of the following does NOT delay the absorption of a drug from its site of injection?
   a. massage of the injection area (increasing blood flow to the area enhances its absorption)
   b. suspension of the active drug in oil (this is used to create a sustained release, or “depo” injection)
   c. occlusion of the circulation in the area of the injection (this keeps the drug in the area)
   d. incorporation of a vasoconstrictor with the drug to be injected (think epinephrine and lidocaine)
   e. implantation of the drug in a solid pellet form under the skin (again, long term therapies here--think of the 5 year birth control implants popular until just recently)
 Study Guide Questions for Local and General Anesthesia
KCC Dental Hygiene Students: to send your homework, highlight the questions below, go to "edit," click on "copy," then click onto my email address below...when the email appears, go to "edit" in the email menu, click on "paste," and the questions will appear as the body of the email.  Answer the questions and then press "send." Your homework will be reviewed and returned via email within 72 hours.  Or just do it all on paper and bring your work to the next class session.

1. What is the primary site of absorption and excretion for inhalation general anesthesia?
2. What is the mechanism of action for local anesthetics?
3. What is the numeric value of physiological pH? Is it basic, acidic or neutral?
4. Why is a local anesthetic less effective in the presence of inflammation?
5. What is the purpose of adding epinephrine to a local anesthetic?  What precautions must be taken?
6. What are three disadvantages limiting the value of topical anesthetic sprays?
7. Topical anesthetic agents are most effective when applied to which type of tissue?
8. A red flag should fly up when a patient states he is allergic “to novocaine.”  Why?
9. What is malignant hyperpyrexia/hyperthermia?  What is its treatment?
10-12. List the local anesthetics presented in the lecture, divided by class.  Be sure to label the appropriate class.
13. What is a drawback to the use of diphenhydramine as a local anesthetic?
14. Name a drug of abuse that is also an effective topical anesthetic.
15. What is the double gas effect?
16. Name a weak general anesthetic.
17. What is diffusion hypoxia?
18. Describe the stages of general anesthesia.
19. What is the nitrous oxide/oxygen ratio for induction of general anesthesia?  What is the ratio for maintenance?
20. Halogenated inhalation anesthetics can cause sensitization of the cardiac tissue to epinephrine.  Give three examples of halogenated inhalation anesthetics.

End of Module Six
Anesthesia
Jim Middleton, Pharmacist, Instructor
KCC Dental Hygiene Pharmacology