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

DEFINITION: General anesthetics are drugs which produce reversible loss of all sensation and Consciousness.

Inhibition of Autonomic reflexes Skeletal muscle relaxation Unconsciousness GA s Amnesia Analgesia

Properties General Anesthetics Local Anesthetics Site of Action Area of body involved Consciousness Care of Vital functions Poor health in patient Use in non co-operative patients Major surgeries Minor surgeries CNS Whole body Lost Essential Risky Possible Preferred Not Preferred Peripheral Nerves Restricted area Unaltered Usually not needed Safer Not possible Cannot be used

MINIMAL ALVEOLAR CONCENTRATION (MAC): A measure of potency 1MAC is the concentration necessary to prevent responding in 50% of population.

STAGES OF GENERAL ANESTHESIA: I. STATE OF ANALGESIA II. STATE OF EXCITEMENT AND DELIRIUM III. STATE OF SURGICAL ANESTHESIA IV. MEDULLARY PARALYSIS

PATHWAY OF GENERAL ANESTHETICS:

ANESTHETICS GENERAL premedication Induction of anesthesia Maintenance Of

I. Relief from anxiety(Benzodiaepines) III. Post – operative INTRA VENOUS ANESTHETICS PREMEDICATION INHALATION ANESTHETICS I. Relief from anxiety(Benzodiaepines) II. Reduction in secretions and vagal reflexes (hyoscine/Atropine) III. Post – operative (Anti- emetics) IV. Pain Relief (NSAIDs, Opioid analgesics) (Thiopental) # Barbiturates # Non- Barbiturates a. Propofol b. Etomidate c. ketamine Nitrous oxide Halothane Isoflurane Enflurane Desflurane Sevoflurane

MECHANISM OF ACTION:

Amount that reaches the brain PHARMACOKINETICS OF INHALED ANESTHETICS: Amount that reaches the brain Indicated by oil:gas ratio (lipid solubility) Partial Pressure of anesthetics 5% anesthetics = 38 mmHg Solubility of gas into blood The lower the blood:gas ratio, the more anesthetics will arrive at the brain Cardiac Output Increased CO= greater Induction time

PHARMACOKINETIC PROPERTIES OF IV ANESTHETICS:

TOXICITY OF ANESTHETIC AGENTS: ACUTE TOXICITY NEPHROTOXICITY HEMATOTOXICITY MALIGNANT HYPERTHERMIA HEPATOTOXICITY CHRONIC TOXICITY MUTAGENICITY TERATOGENICITY REPRODUCTIVE EFFECTS CARCINOGENICITY

SOME PLANTS SHOWING ANESTHETIC ACTIVITY: Datura metel Brugmansia species Winter green( used for arthritis, aching muscle, gout) Theophrastus Pedanius dioscorides

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.