anesthetic drugs pharmacology

8/14/2019 Anesthetic Drugs Pharmacology

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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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STAGE III Surgical anesthesia

Regular respirationSkeletal muscles relaxation

Eye reflexes

Eye movementsFixed pupil

STAGE IV Medullary paralysis


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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


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


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


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

anesthetic drugs pharmacology

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