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ANESTHETICS DRUGS
Depart. of Pharmacology and Therapy
Medical School -Padjadjaran University
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TERMINOLOGY
ANESTHETICS :
Drugs that caused anesthesia
ANESTHESIA :
No pain sensation
TWO GROUPS OF ANESTHESIA :
1. General Anesthetics
2. Local Anesthetic
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THEORYOF ANESTHESIA
1. No stimuli from perifer
2. Stimuli + Block at Gg. cervicalis sup
3. Stimuli +
No block at Gg. Cervicalis sup
No interpretation
4. Stimuli +No block
interpretation +
No response
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GENERAL ANESTHESIA
Analgesic, amnesic, unconscious state
Muscle relaxation
Suppresion of undesirable reflexes
BALANCED ANESTHESIA
PRE ANESTHETIC MEDICATION
SKELETAL MUSCLE RELAXANTS
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PRE ANESTHETIC MEDICATION
SERVES TO :
Calm the patient
Relieve pain Protect against undesirable effects of the subsequently
administered anesthetic or the surgical procedures
INCLUDING :
Hipnotic sedatives, anti histamines, anti emetics, opioids,
anti cholinergics
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STAGES OF ANESTHESIA
STAGE I Analgesia
STAGE II Excitement
violent combative behavior
BP
Respiratory rate
Reflexes
Hyper secretion
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STAGES OF ANESTHESIA
STAGE III Surgical anesthesia
Regular respirationSkeletal muscles relaxation
Eye reflexes
Eye movementsFixed pupil
STAGE IV Medullary paralysis
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STAGES OF ANESTHESIA
PLANE I PLANE II PLANE III PLANE
IV
EYE
Rovingmovment of
eye ball.
Myotic pupil
midconstriction middilatation dilatation
REFLEXES
MUSCLE
RELAXATION
Small
muscles
Large muscles All muscles All
muscles
RESPIRATION Thoracal >
Abdominal
Thoracal =
Abdominal
Abdominal
>
Thoracal
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EVALUATION
Rhythm and automatization of respiration
Conjunctival reflexes
Gradually loss of Mm. Intercostales activity
Fixated eye
DEEP ANESTHESIA
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GENERAL ANESTHESIA
INHALATIONAL ANESTHETICS
INTRAVENOUS ANESTHETICS
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INHALATIONAL ANESTHETICSMECHANISM OF ACTION
Non selective action
Their clinically important effect on the CNS
also alter the function of various peripheral
cell types
Site of action :Reticular activating system
and cortex cerebri (controlling the overallstate consciousness and response to sensory
stimuli)
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INHALATIONAL ANESTHETICSTHE POTENCY
Defined quantitatively as the MINIMUM ALVEOLAR
CONCENTRATION (MAC)
MAC :
The concentration of gas anesthetic needed to eliminate
movement among 50% of patient challenged by a
standardized skin incision
MAC is small for potent anesthetics and large for theless one
The more lipid soluble an anesthesia, the lower the
concentration of anesthetics needed to produce
anesthesia
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THE PHARMACOKINETICS OF
INHALATIONAL ANESTHETICS
Partial pressure of anesthetic gas driving
force moves the anesthetics into the
alveolar space blood brain and body
compartment
Steady state :
The partial pressure in each of these compartments
is equivalent to that in inspired mixtures
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THE PHARMACOKINETICS OF
INHALATIONAL ANESTHETICS
The steady state depends on :
Alveolar wash-in
Solubility in blood
Blood-gas partition coefficient
halothane > enflurane > isoflurane > N20
solubility faster achievement of steadystate
Tissue uptake
Wash-out
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COMMON FEATURES OF
INHALATIONAL ANESTHETICS
Decrease cerebrovascular resistance
resulting in increased perfusion of the brain
Bronchodilation and decrease minuteventilation
Potency does correlate with their solubility
in lipid
Recovery is due to redistribution from the
brain
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HALOTHANE
Weak analgesic effect
Vagomimetic, atropine-sensitive bradycardi
Cardiac output , hipotension
Cardiac arrhytmia, esp. to whom with hipercapnia
and high concentration of blood catecholamine
Toxic metabolites (trifluoroethanol + bromide ion) No hepatotoxic effect for children
DOC for pediatric patient
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ENFLURANE
Less potent than halothane
Rapid induction and recovery
The metabolite (fluoride ion) excreted by kidney,
so its contra indicated in patient with renal failure
Some differences from halothane:
Fewer arrhytmia
less heart sensitization to catecholamines
greater potentiation of muscle relaxants
Intra ocular pressure
Disadvantage : CNS excitation
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ISOFLURANE
Low biotransformation and low organ
toxicity
Doesnt induce cardiac arrhytmia
No heart sensitization to catecholamine
Less fluoride ion is produced
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METHOXYFLURANE
High solubility in lipid
Not for prolonged adminiostration (toxic
effect to the kidney)
Indication : obstetrical practice (does not
relax the uterus)
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NITROUS OXIDE
Potent analgesic, weak general anesthetic
No respiration depression Less effect on CVS
Increasing cerebral blood flow
Less hepatotoxic effect
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INTRAVENOUS ANESTHETICBARBITURATES
Quickly enter the CNS depress function
diffusion out of the brain redistributionto other body tissue
Not significant analgesic
ADR : apnea, coughing, chest wall spasm,laryngospasm, bronchospasm
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BENZODIAZEPINES
Lorazepam and Midazolam are more potent
than diazepam Facilitate amnesia while causing sedation
Etomidate : No analgesic effect
uncontrolled skeletal muscle activity
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OPIOIDS
Analgesic effect
Amnesic effect