Download G_A_PPT - ichapps.com

GENERAL ANAESTHETIC
AGENTS
By
Afsar fathima
CONTENTS:
•DEFINITION
•NEUROPHYSIOLOGIC STATE PRODUCED BY GENERAL
ANESTHETICS
•DIFFERENCE BETWEEN GENERAL AND LOCAL ANESTHETICS
•OVERTON & MEYER CORRELATION
•CLASSIFICATION OF GA s
•MECHANISM OF ACTION
•PHARMACOKINETICS OF DRUGS
•TOXICITY OF GA s
•SOME PLANTS WITH ANESTHETIC ACTIVITY
•REFERENCES
2
DEFINITION:
General anesthetics are drugs which
produce reversible loss of all sensation
and Consciousness.
3
Inhibition of Autonomic
reflexes
Unconsciousness
Skeletal muscle relaxation
GA s
Amnesia
Analgesia
4
Properties
• Site of Action
•Area of body involved
•Consciousness
General Anesthetics
CNS
Whole body
Lost
•Care of Vital functions
Essential
•Poor health in patient
Risky
•Use in non co-operative
Local Anesthetics
Peripheral Nerves
Restricted area
Unaltered
Usually not needed
Safer
Possible
Not possible
•Major surgeries
Preferred
Cannot be used
•Minor surgeries
Not Preferred
patients
Preferred
5
MINIMAL ALVEOLAR CONCENTRATION
(MAC):
• A measure of potency
• 1MAC is the concentration
necessary to prevent responding
in 50% of population.
6
STAGES OF GENERAL ANESTHESIA:
I.
STATE OF ANALGESIA
II. STATE OF EXCITEMENT AND DELIRIUM
III. STATE OF SURGICAL ANESTHESIA
IV. MEDULLARY PARALYSIS
7
PATHWAY OF GENERAL ANESTHETICS:
8
GENERAL
ANESTHETICS
premedication
Induction of
anesthesia
Maintenance
Of
anesthesia
9
PREMEDICATION
I. Relief from
anxiety(Benzodiaepines)
II. Reduction in secretions
INHALATION
ANESTHETICS
Nitrous oxide
INTRA VENOUS
ANESTHETICS
# Barbiturates
(Thiopental)
Halothane
# Non- Barbiturates
and vagal reflexes
(hyoscine/Atropine)
Isoflurane
a. Propofol
III. Post – operative
(Anti- emetics)
Enflurane
b. Etomidate
Desflurane
c. ketamine
IV. Pain Relief (NSAIDs,
Opioid analgesics)
Sevoflurane
10
MECHANISM OF ACTION:
11
12
PHARMACOKINETICS OF INHALED ANESTHETICS:
1. Amount that reaches the brain
Indicated by oil:gas ratio (lipid solubility)
2. Partial Pressure of anesthetics
5% anesthetics = 38 mmHg
3. Solubility of gas into blood
The lower the blood:gas ratio, the more
anesthetics will arrive at the brain
4. Cardiac Output
Increased CO= greater Induction time
13
14
PHARMACOKINETIC PROPERTIES OF IV ANESTHETICS:
15
TOXICITY OF ANESTHETIC AGENTS:
ACUTE TOXICITY
CHRONIC TOXICITY
•NEPHROTOXICITY
•MUTAGENICITY
•HEMATOTOXICITY
•TERATOGENICITY
•MALIGNANT
HYPERTHERMIA
•REPRODUCTIVE
EFFECTS
•HEPATOTOXICITY
•CARCINOGENICITY
16
SOME PLANTS SHOWING ANESTHETIC ACTIVITY:
•Datura metel
•Brugmansia species
•Winter green( used for arthritis, aching muscle, gout)
•Theophrastus
•Pedanius dioscorides
17
REFERENCES:
•Basic and clinical pharmacology- katzung, RogerJ.Porter,MD ,&
Brain S. Meldrum,MB, PhD 11th edition
•RANG & DALE’S Pharmacology 7th edition
•Essentials of Medical Pharmacology, KD Tripathi
•Medical Pharmacology at a Glance, Michael J Neal
•Goodman & Gilman’s The Pharmacological Basis of
Therapeutics, 11th edition.
18
19