Chapter 12- General and Local Anesthetics Flashcards Preview

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Flashcards in Chapter 12- General and Local Anesthetics Deck (38):
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Anesthetics

Drugs that depress the central nervous system (CNS)
-depression of consciousness
-loss of responsiveness to sensory stimulation (including pain)
-muscle relaxation

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Anesthesia

A state of depressed CNS activity

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Two types of anesthesia

*General anesthesia
*Local anesthesia

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General Anesthetics

*Drugs that induce a state in which the CNS is altered to produce verying degress of:
-analgesia
-depression of consciousness
-skeletal muscle relaxation
-reflex reduction

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General Anesthetics: Inhaled anesthetics

Volatile liquids or gases that are vaporized/mixed in oxygen and inhaled

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General Anesthetics: Parenteral anesthetics

Administered intravenously

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Inhaled Anesthetics

Inhaled gas:
-nitrous oxide

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Inhaled volatile liquids:

-desflurane
-enflurane (Ethrane)
-halothane (Fluothane)
-isoflurane (Forane)
-methoxyflurane (Penthrane)
-sevoflurane

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Injectable Anesthetics- Used:

-To induce or maintain general anesthesia
-To induce amnesia
-As an adjunct to inhalation-type anesthetics

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Injectable Anesthetics:

*etomidate (Amidate)
*ketamine (Ketalar)
*methohexital (Brevital)
*propofol (Diprivan)
*thiamylal (Surital)
*thiopental (Pentothal)

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Sedative-hypnotics

*Barbiturates (pentobarbital, secobarbital)
*Benzodiazepines (diazepam, midazolam)
*hydroxyzine
*promethazine

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Opioid Analgesics

fentanyl, sufentanil, meperedine, morphine

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Neuromuscular blocking drugs (NMBDs)

-depolarizing drugs (succinylcholine)
-nondepolarizing drugs (pancuronium, d-tubocurarine, vecuronium)

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Anticholinergics:

atropine, glycopyrrolate, scopolamine

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Mechanism of Action

*Varies according to drug
*Overton-Meyer theory
*Overall effect
-orderly and systematic reduction of sensory and motor CNS functions
-progressive depression of cerebral and spinal cord functions

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Indications

*General anesthetics used during surgical procedures to produce:
-unconsciousness
-skeletal muscular relaxation
*Rapid onset; quickly metabolized
*Also used in electroconvulsive therapy treatments for depression

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Adverse Effects

*Vary according to dosage and drug used
*Sites primarily affected
-heart, peripheral circulation, liver, kidneys, respiratory tract
*Myocardial depression is commonly seen

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Adverse Effects: Malignant Hyperthermia

-occurs during or after general anesthesia or use of the NMBD succinylcholine
-sudden elevation in body temperature (greater that 104)
-tachypnea, tachycardia, muscle rigidity
-life threatening emergency
-treated with dantrolene (skeletal muscle relaxant)

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Moderate Sedation

*Also called conscious sedation, procedural sedation
-combination of an IV benzodiazepine and an opiate analgesic
-anxiety and sensitivity to pain are reduced, and patient cannot recall the procedure
-preserves the patients ability to maintain own airway and to respond to verbal commands

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Moderate Sedation also used for:

-diagnostic procedures and minor surgical procedures that do not require deep anesthesia
-topical anesthetic may be applied also
-Rapid recovery time and greater safety profile than general anesthesia

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Local Anesthetics

*Also called regional anesthetics
-used to render a specific portion of the body insensitive to pain
-interfere with nerve impulse transmission to specific areas of the body
-do not cause loss of consciousness

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Local Anesthetics: Topical

-Applied directly to skin or mucous membranes
-creams, solutions, ointments, gels, ophthalmic drops, lozenges, suppositores

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Local Anesthetics: Parenteral

-injected parenterally or into the CNS by various spinal injection techniques

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Types of Local Anesthesia

*Spinal or intraspinal
-Intrathecal
-Epidural
*Infiltration
*Nerve block
*Topical

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Parenteral Anesthetics

*procaine (Novocain)
*tetracaine (Pontocaine)
*lidocaine (Xylocaine)
*mepivacaine (Carbocaine)
*bupivacaine

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Drug Effects: Paralysis

*First, autonomic activity is lost
*Then pain and other sensory functions are lost
*Last, motor activity is lost
*As local drugs wear off, recovery occurs in reverse order (motor, sensory, then autonomic activity are restored)

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Indications: Local anesthetics are used for-

*Surgical, dental, and diagnostic procedures
*Treatment of certain types of chronic pain
*Spinal anesthesia: to control pain during surgical procedures and childbirth

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Local anesthetics are given by:

-Infiltration anesthesia
-Nerve block anesthesia

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Infilitration anesthesia

-Minor surgical and dental procedures
-injection of the anesthetic solution intradermally, subcutaneously, or submucosally across the path of nerves supplying the target area
-May be given in a circular pattern around the operative area

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Infilitration anesthesia and epinephrine

*Some local anesthetics used for infiltration or nerve block are combined with vasoconstrictors
-to prevent systemic absorption of anesthetic
-to help confine local anesthetic to injected area
-to reduce local blood loss during procedure
-epinephrine, phenylephrine, norepinephrine

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Nerve block anesthesia

*Used for surgical, dental, and diagnostic procedures
-also used for therapeutic management of pain
-the anesthetic drug is injected directly into or around the nerve trunks or nerve ganglia that supply the area to be numbed

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Adverse Effects:

*usually limited
*adverse effects result if:
-inadvertent intravascular injection occurs
-excessive dose or rate of injection is given
-slow metabolic breakdown occurs
-"spinal headache," treated with an epidural blood patch

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Neuromuscular Blocking Drugs:

-Also known as NMBDs
-Prevent nerve transmission in certain muscles, resulting in muscle paralysis
-Used with anesthetics during surgery

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Neuromuscular Blocking Drugs: When used during surgery

Artificial mechanical ventilation is required
-these drugs paralyze respiratory and skeletal muscles
-patient cannot breathe on is or her own
-do not cause sedation or pain relief
-patient may be paralyzed yet conscious
-depolarizing drugs
-Nondepolarizing drugs
short acting
intermediate acting
long acting

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NMBAs: depolarizing drug

Succinylcholine
-works similarly to neurotransmitter acetylcholine (Ach), causing depolarization
-metabolism is slower than Ach, so as long as succinylcholine is present, repolarizing cannot occur
*Result: flaccid muscle paralysis

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NMBAs: nondepolarizing drugs

*Short acting
-mivacurium (Mivacron)
*Intermediate acting
-atracurium (Tracrium), vecuronium (Norcuron)
-rocuronium (Zemuron)
*Long acting
-pancuronium (Pavulon), doxacurium (Nuromax)
-d-tubocurarine

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Nodepolarizing NMBAs

-prevent Ach from acting at neuromuscular junctions
-muscle fibers are not stimulated
-skeletal muscle contraction does not occur

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Neuromuscular Blocking Drugs

-first sensation is muscle weakness
-followed by total flaccid paralysis
-Small, rapidly moving muscles affected first (fingers, eyes) then limbs, neck, trunk
-finally, intercostal muscles and diaphragm affected,