Module 2-3 Anesthetic drugs Flashcards Preview

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Flashcards in Module 2-3 Anesthetic drugs Deck (36):
1

Anesthetics

Drugs that depress the central nervous
system (CNS)
 Depression of consciousness
 Loss of responsiveness to sensory stimulation
(including pain)
 Muscle relaxation

2

Anesthesia

A state of depressed CNS activity
 Two types
 General anesthesia
 Local anesthesia
 Balanced anesthesia

3

General Anesthetics

 Drugs that induce a state in which the CNS is altered to produce varying degrees of:
analgesia
 Depression of consciousness
 Skeletal muscle relaxation
 Reflex reduction

4

General Anesthetics (cont’d)

Inhaled anesthetics
 Volatile liquids or gases that are vaporized/mixed
in oxygen and inhaled
 Parenteral anesthetics
 Administered intravenously

5

Inhaled Anesthetics

Inhaled gas
 nitrous oxide
 Inhaled volatile liquids
 desflurane
 enflurane (Ethrane)
 halothane (Fluothane)
 isoflurane (Forane)
 methoxyflurane (Penthrane)
 sevoflurane

6

Injectable Anesthetics

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

7

Injectable Anesthetics (cont’d)

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

8

Adjunct Drugs

Sedative-hypnotics
 Barbiturates (pentobarbital, secobarbital)
 Benzodiazepines (diazepam, midazolam)
 hydroxyzine
 promethazine
 Opioid Analgesics
 fentanyl, sufentanil, meperedine, morphine

9

Adjunct Drugs (cont’d)

Neuromuscular blocking drugs (NMBDs)
 Depolarizing drugs (succinylcholine)
 Nondepolarizing drugs (pancuronium
pancuronium,
d-tubocurarine, vecuronium)
 Anticholinergics
 atropine, glycopyrrolate, scopolamine

10

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

11

Indications

General anesthetics used during surgical
procedures to produce:
 Unconsciousness
 Skeletal muscular relaxation
 Visceral smooth muscle relaxation
 Rapid onset; quickly metabolized
 Also used in electroconvulsive therapy
treatments for depression

12

Adverse Effects

Vary according to dosage and drug used
 Sites primarily affected
 Heart, peripheral circulation, liver, kidneys,
respiratory tract
 Myocardial depression is commonly seen

13

Adverse Effects (cont’d)

Malignant hyperthermia
 Occurs during or after general anesthesia or use
of the NMBD succinylcholine
Sudden elevation in body temperature (greater
than 104° F)
 Tachypnea, tachycardia, muscle rigidity
 Life-threatening emergency
 Treated with dantrolene (skeletal muscle relaxant)

14

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 patient’s ability to maintain own airway and to respond to verbal commands

15

Moderate Sedation (cont’d)

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

16

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

17

Local Anesthetics (cont’d)

Topical
 Applied directly to skin or mucous membranes
Creams, solutions, ointments, gels, ophthalmic
drops lozenges suppositories
drops, lozenges, 
Parenteral Injected parenterally or into the CNS by various spinal injection techniques

18

Types of Local Anesthesia

Spinal or intraspinal
 Intrathecal
 Epidural
 Infiltration
 Nerve block
 Topical

19

Parenteral Anesthetics

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

20

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)

21

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
 Local anesthetics are given by:
 Infiltration anesthesia
 Nerve block anesthesia

22

Indications (cont’d)

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

23

Indications (cont’d)

Infiltration 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

24

Indications (cont’d)

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

25

Adverse Effects

Usually limited
 Adverse effects result if:
 Inadvertent intravascular injection occurs
 Excessive dose or rate of injection is given
 Slow metabolic breakdown occurs
 Injection into highly vascular tissue occurs
 “Spinal headache,” treated with an epidural blood patch

26

Neuromuscular Blocking Drugs

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

27

Neuromuscular
Blocking Drugs (cont’d

When used during surgery, artificial
mechanical ventilation is required
 These drugs paralyze respiratory and skeletal
muscles
 Patient cannot breathe on his or her own
 Do not cause sedation or pain relief
 Patient may be paralyzed yet conscious

28

Neuromuscular
Blocking Drugs (cont’d

Depolarizing drugs
 Nondepolarizing drugs
 Short acting
 Intermediate acting
 Long acting

29

NMBAs: Depolarizing Drug

Succinylcholine
 Works similarly to neurotransmitter acetylcholine
(Ach), causing depolarization
 Metabolism is slower than Ach so as long as
Ach, succinylcholine is present, repolarization cannot
occur
 Result: flaccid muscle paralysis

30

NMBAs: Nondepolarizing Drugs

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

31

Nondepolarizing NMBAs

Prevent Ach from acting at neuromuscular
junctions
 Muscle fibers are not stimulated
 Skeletal muscle contraction does not occur

32

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
eyes), limbs, neck,  Finally, intercostal muscles and diaphragm affected,
resulting in cessation of respirations
 Recovery of muscular activity usually occurs in reverse order
 Transient muscle fasciculations may result in later
muscle soreness

33

NMBAs:
Indications

Main use: maintaining controlled ventilation
during surgical procedures
 Endotracheal intubation (short acting)
 To reduce muscle contraction in an area that needs surgery

34

NMBAs:
Adverse Effects

Few when used appropriately
 May cause:
 Hypotension (blockade of autonomic gangli
 Tachycardia (blockade of muscarinic receptors)
 Hypotension (release of histamine)

35

NMBDs: Safety

Respiratory muscle paralysis occurs with
these drugs
Emergency ventilation equipment must be
immediately available

36

NMBDs: Overdose

Overdose causes prolonged paralysis
requiring prolonged mechanical ventilation
Cardiovascular collapse may occur