دوائيات اولى

• General anesthesia


  A method of medically inducing loss of consciousness that renders a patient unarousable even with painful stimuli
• General anesthesia


  التخدير العام
• General anesthesia


  • Administered intravenously or by inhalation
• Balanced anesthesia


  Includes: loss of consciousness, analgesia, muscle relaxation, abolition of compensatory reflex response
• General anesthetics have therapeutic indices of about 2-4
• Preanaesthetic medication


  The use of drugs prior to anesthesia to make it more safe and pleasant
• Purposes of preanaesthetic medication

  • To relieve anxiety - benzodiazepines
  • To prevent allergic reactions - antihistaminics
  • To prevent nausea and vomiting - antiemetics
  • To provide analgesia - opioids
  • To prevent acidity - proton pump inhibitor
  • To prevent bradycardia and secretion - atropine
• Steps of anesthesia


  1. Induction

  2. Maintenance

  3. Recovery
• Stage II: Stage of excitement


  Disturbed consciousness, irregular respiration, retching and vomiting, incontinence
• Stage III: Surgical anesthesia

  • Plane 1 - roving movements of eyeballs
  • Plane 2 - progressive loss of corneal reflex
  • Plane 3 - pupils start dilating, muscle relaxation
  • Plane 4 - only abdominal respiration, dilated pupils
• Stage IV: Stage of medullary depression


  Loss of consciousness, no spontaneous respiration, cardiovascular collapse
• Transfer of anesthetic from alveolar air to blood and from blood to brain

  1. Anesthetic must be transferred from the alveolar air to blood

  2. Anesthetic must be transferred from blood to brain
• Factors influencing the transfer

  • Solubility in blood (blood/gas partition coefficient)
  • Anesthetic concentration in the inspired air
  • Pulmonary ventilation
  • Pulmonary blood flow
  • Uptake of the anesthetic by the tissues
• Main classes of general anesthetics

  • Inhaled anesthetics
  • Intravenous anesthetics
• Intravenous anesthetics

  • Barbiturates (thiopental, methohexital)
  • Propofol
  • Etomidate
  • Ketamine
• Inhaled anesthetics

  • Halogenate agents (halothane)
  • Benzodiazepines (midazolam, diazepam)
  • Opioids (morphine, fentanyl)
  • Enflurane
  • Desflurane
  • Sevoflurane
  • Nitrous oxide
• Phases of modern balanced general anesthesia

  1. Preanesthetic care

  2. Induction of anesthesia

  3. Maintenance of anesthesia
• Preanesthetic care drugs

  • Diazepam, lorazepam
  • Chlorpromazine, haloperidol
  • Atropine
  • Morphine, meperidine
• Induction of anesthesia drugs

  • Thiopental (propofol or etomidate or midazolam may be alternative drugs)
• Maintenance of anesthesia

  • One or two inhaled anesthetics (loading dose)
  • One or two inhaled anesthetics (maintenance dose)
  • Neuromuscular blocking agents
  • Opioids
• Sevoflurane

  السيفوفلوران
• Parenteral anaesthetics

  • For induction of anesthesia
  • Rapid onset of action
  • Recovery is by redistribution
• Propofol

  • Most commonly used IV anesthetic
  • Unconsciousness in 45 seconds and lasts 15 minutes
  • Anti-emetic in action
  • Non-irritant to airways
  • Suited for day care surgery
  • Adverse effects: fall in BP, pain during injection
• Ketamine

  • Profound analgesia, immobility, amnesia with light sleep
  • Acts by blocking NMDA receptors
  • Heart rate and BP are elevated due to sympathetic stimulation
• Ketamine

  الكيتامين