DR. MOHD NAZAM ANSARI. Partial or complete loss of sensation with or with out loss of consciousness...
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Transcript of DR. MOHD NAZAM ANSARI. Partial or complete loss of sensation with or with out loss of consciousness...
PHARMACOLOGY – I (PRACTICAL)[PHL 313]
DR. MOHD NAZAM ANSARI
Background General anesthesia was absent until the
mid-1800’s William Morton administered ether to a
patient having a neck tumor, removed at the Massachusetts General Hospital, Boston, in October 1846.
The discovery of the diethyl ether as general anesthesia was the result of a search for means of eliminating a patient’s pain perception and responses to painful stimuli.
Lab 3:STUDY OF DIFFERENT
STAGES OF ANESTHESIA
Partial or complete loss of sensation with or with out loss of consciousness as a result of disease, injury, or administration of an anesthetic agent, usually by injection or inhalation.
Anesthesia
TYPES OF ANESTHESIA
A. GENERAL- A drug that brings about a reversible loss of
consciousness Total loss of consciousness and sensation,
sleep (unconsciousness), and muscle relaxation;
IV, Inhalation, Rectal
B. LOCAL- Reduce all painful sensation in one region of
the body without inducing unconsciousness.
INHALATION ANESTHETIC AGENTS
Volatile Liquids Ether Halothane ( Fluothane) Enflurane (Ethrane) Isoflurane (Forane) Sevoflurane (Ultrane) Desflurane ( Suprane)
Gases Nitrous oxide Cyclopropane Ethylene
INTRAVENOUS ANESTHETIC AGENTS
Inducing Agent (~11 sec) Thiopentone sodium Propofol Etomidate
Slower Acting Drugs Benzodiazepines
Diazepam (5-10 min) Lorazepam
Dissociative anesthesia Ketamine
Neurolept analgesia Fentanyl + Droperidol
LOCAL ANESTHESIA Rectal (Pediatrics)-
Anectine, Pentothal Na 5-10%
Spinal anesthesia- Procaine (Novocaine), Tetracaine(Pontocaine), Lidocaine(Xylocaine), Mepivacaine (Carbocaine), Bupivacaine( Marcaine)
Muscle relaxants- Anectine (Succinyl choline), Pavulon (Pancuronium)
Description General Anesthetics Local Anesthetics
1. Site of action Central Nervous System Peripheral Nerves
2.Area of body involved Whole body Restricted area
3. Conciousness Lost Unaltered
4. Major surgery Preferred Can not be used
5. Minor surgery Can not be used Preferred
6. Poor health patient Risky Safer
7. Care of vital function Essential Usually not needed
Anesthesiology
Preanesthetic medication:It is the use of drugs prior to anesthesia to
make it more safe and pleasant. To relieve anxiety – benzodiazepines. To prevent allergic reactions –
antihistaminics. To prevent nausea and vomiting –
antiemetics. To provide analgesia – opioids. To prevent bradycardia and secretion –
atropine.
Lipid theory of General Anaesthetics
Based on the fact the anesthetic action is correlated with the oil/gas coefficients.
Higher the solubility of general anesthetics in oil greater is the anesthetics action.
Anesthetic Suppression of Physiological Response to
Surgery
Anesthesiology
Molecular mechanism of the GA : GABA –A : Potentiation by
Halothane, Propofol, Etomidate NMDA receptors : inhibited by
Ketamine
Molecular Actions: GABAA
Receptor Ligand-gated ion channels
Chloride channels gated by the inhibitory GABAA receptor
GABAA receptor mediates the effects of gamma-amino butyric acid (GABA), the major inhibitory neurotransmitter in the brain
GABAA receptor found throughout the CNS
Most abundant, fast inhibitory, ligand-gated ion channel in the mammalian brain
Located in the post-synaptic membrane
Molecular Actions: GABAA
Receptor GABAA receptor is a 4-transmembrane (4-
TM) ion channel 5 subunits arranged around a central
pore: 2 alpha, 2 beta, 1 gamma Each subunit has N-terminal
extracellular chain which contains the ligand-binding site
Molecular Action: GABAA
Receptor
Molecular Action: GABAA
Receptor Receptor sits in the membrane of its neuron at the synapse
GABA, endogenous compound, causes GABA to open
Receptor capable of binding 2 GABA molecules, between an alpha and beta subunit Binding of GABA causes
a conformational change in receptor Opens central pore Chloride ions pass
down electrochemical gradient
Net inhibitory effect, reducing activity of the neuron
STAGES OF ANESTHESIA Irregular descending depression of CNS
STAGE 1 (ANALGESIA/ONSET/INDUCTION): Extends from the administration of anesthesia
to the time of loss of consciousness. Pain is progressively abolished during this
stage. Patient remains conscious, can hear and see,
and feels a dream like state. Reflexes and respiration remain normal. Some minor and major operation can be
carried out.
STAGE 2 (EXCITEMENT/DELIRIUM): Extends from the time of loss of consciousness
to beginning of regular respiration Characterized by struggling, delirium, irregular
respiration, and breatholding are commonly seen.
Muscle tone increases, jaws are tightly closed, vomiting, involuntary micturation or defecation may occur.
Heart rate and BP may rise. Pupils are dilated. No operation.
STAGE 3 (Surgical Anesthesia): Extends from the regular respiration to the
loss of most of the reflexes. Muscle tone decreases, BP falls, HR increases,
constricted pupils, and regular respirations. Surgical procedure is started.
STAGE 4 (Impending Death/ Stage of Danger): Cessation of breathing, to failure of circulation
and death. Pupil is widely dilated. It is due to anesthesia overdose.
Thank you