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Uploaded by Drx Vaishnavi Bhasme
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PHARMACOLOGY GENERAL ANAESTHETICS MPHARM

The document presents a comprehensive overview of general anaesthetics, detailing their definition, cardinal features, and classification, including inhalational and intravenous anaesthetics. It describes the stages of general anaesthesia and outlines the differences between general and local anaesthetics, emphasizing the systemic effects of the former. Additionally, it discusses specific agents such as nitrous oxide, halothane, sevoflurane, thiopental, propofol, and ketamine, highlighting their characteristics, effects, and contraindications.

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l SSR COLLAGE OF PHARMACY General Anaesthetics NAME-Vaishnavi bhasme CLASS-1 Sem M.PHAM GUIDED BY – Kajal Patil DATE -23/11/2024
 Definition  Cardinal features general anaesthesia  Stages of generl anaesthesia  Difference between general and localanaesthetics5  Mechanism of general anaesthetics  Classification of general anaesthetics  Inhalational anaesthetics  Intravenous anaesthetics . FLOW OF PRESENTATION
3 Definition Anesthesia (an =without, aisthesis = sensation The drugs which produce reversible loss of all and consciousness sensations. Generally administered by an anaesthesiologist in order to induce or maintain general anathesia to facilitate surgery. WHAT ARE GENERAL ANAESTHETICS ?
. . THE CARDINAL FEATURES OF GENERAL ANAESTHETICS 1. Loss of all sensation, especially pain 2. Sleep(unconsciousness) and amnesia 3. Abolition of somatic and autonomic reflexes 4. Immobility and muscle relaxation
. STAGES OF GENERAL ANAESTHESIA 1.Stage of Analgesia Start from beginning of anaesthesia administration and last up to loss of consciousness feels a dream like state, reflexes and respiration remains normal . 2 Stage of delirium from loss of consciousness to beginning of irregular respiration. Apparent excitement is seen. Muscle tone increases. Jaws are tightly closed. Heart rate and blood pressure may rise. 4 Medullary paralysis - respiratory and vasomotor control ceases. 3 Surgical anaesthesia extends from onset of irregular respiration to cessation of spontaneous breathing. This has been divided into 4 planes 1This plane ends when eyes become fixed . 2 Loss of corneal and laryngeal reflexes.. 3Pupil start dilating and light reflexes. 4 Dilated pupil, decrease muscle tone ,BP falls.
. . General anesthetics Local anesthetics DIFFERENCE BETWEEN GENERAL AND LOCAL ANAESTHETICS Central nervous system Whole body effects Consciousness loss Major surgery preferred Minor surgery can not be used Poor health patient risky Peripheral nerves Restricted area Consciousness unaltered Major surgery can not be used Minor sugery preferred Poor health patient safer
7 . classification
Mechanism of general anaesthetics Activity of inhibitory transmitted like GABA Block activity of excitatory neurotransmitter like NMDA and GLUTAMATE receptor Decrease the transmission in reticular formation Loss of sensation
9 Ether  It is explosive  Irritant to respiratory tract  High incidence of nausea and vomiting during induction and post-surgical emergence. INHALATIONAL ANAESTHETICS Inhalational anesthesia refers to the delivery of gases or vapours to the respiratory system to produce anaesthesia
Nitrous oxide  Colourless, odourless gas at room temperature.  Very insoluble in blood and other tissues quick recover  Rapid induction of anaesthesia and rapid emergence following discontinuation of administration.  Completely eliminated by the lungs  It is weak anaesthetic and powerful analgesic  The mac value is 105%.  Causes megaloblastic anaemia.  Used as adjunct to supplement other inhalationals.
 Volatile liquid at room temperature  Light sensitive .  High fat solubility => slow induction & recovery Eliminated unchanged via lungs.  Commonly used in children, where preoperative placement of an iv catheter can be difficult.  It is marketed in amber bottles with thymol added as a preservative.  Metabolised in liver by Cyt-P450. Halothane
. 1 Side effects of halothane CVS: Cardiae arrhythmia, depression of myocardial contraction. Respiratory system : Depression of respiration Muscles : Malignant hyperthermia Kidney : Decrease renal blood flow Liver and GIT: Cause halothane induced hepatitis & nausia and vomiting DRUG INTERACTION : Halothane + adrenaline, theophylline = > arrhythmia may be precipitated. CONTRAINDICATION : Hepatic dysfunction and/or jaundice
Pleasant smell, non irritant and bronchodilation makes it agent of choice for paediatric anaesthesia.  Neuro anaesthesia  Cardiac anaesthesia  Asthmatics. Sevoflurane reacts with soda lime used in anaesthetic circuit to form "compound A" which acts as renal toxin (nephrotoxic). Agents that should not be given with soda lime 1) Trielene.(trichloro ethylene) 2) Sevoflurane 3) Desflurane . Sevoflurane
MEASURMENT OF INHALATIONAL ANAESTHETIC POTENCY MAC  Minimum alveolar concentration  MAC is the Concentration at which 50% of subjects have no response (movement) to surgical stimulus (skin incision)  Different for each inhaled agent  Increase MAC  Hyperthermia  Hypernatremia  Drug induced elevation of CNS catecholamine stores  Chronic alcohol abuse  Increases in ambient pressure (experimental)
. 1 Two important characteristics of Inhalatior anaesthetics which govern the anaesthesia are; Solubility in the fat (oil : gas partition coefficient) Solubility in the blood (blood : gas partition coefficient) Oil-gas partition coefficients It indicates the amount of gas that is soluble in oil phase. It is a measure of lipid solubility of anaesthetic ,It a measure of anaesthetic potency. Higher the solubility of general anaesthetics in oil greater is the anaesthetics action. Blood-gas partition coefficients: The ratio of the concentration in blood to the concentration in the gas phase. Lower the blood : gas coefficient - faster the induction and the faster the recovery.
. INTRAVENOUS ANAESTHETICS THIOPENTAL  Ultrashort acting barbiturate  High lipid solubility rapid entry into the brain  Rapid onset (20 sec), short duration  Effect terminated not by metabolism but by redistributior  Risk of sever vasospasm if accidently injected into artery  Depress cerebral blood flow  Decrease intracranial pressure  Tissue necrosis gangrene, Tissue stores, hypotension, apnea  Build-up in adipose tissue = very long emergence from anaesthesia
. Propofol  Rapid onset and have a short duration of action  Highly protein bound in vivo and is metabolised by conjugate in the liver   Very good anesthetic for induction and maintaince of anest with no accumulation effect  Side-effects are pain on injection, hypotension and transier apnea following induction  Used for the induction, maintenance of GA and sedation  Useful for day-case surgery
 Dissociative anaesthetic  NMDA Receptor Antagonist  Cardiovascular stimulant  Catatonia, analgesia, and amnesia without loss of consciousness  Useful for anesthetizing patients at risk for hypotension and bronchospasm and for certain paediatric procedures. Ketamine
Etomidate  Rapid induction  Minimal change in cardiac function and respiratory rate  Not analgesic  Cause pain on injection and nausea postoperatively  Prolonged administration may cause adrenal suppression
REFERENCES  Rang & Dale's Pharmacology Humphrey P. Rang. Want to Read.  Goodman & Gilman's the Pharmacological for basis of therapeutics.  https://www.ncbi.nlm.nih.gov/books/NBK493199/.  https://pmc.ncbi.nlm.nih.gov/articles/PMC3674880/’
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