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Nov 28, 2010

Anesthetic Agents & Anesthesia

  • Anesthesia is the loss of sensation by giving anesthetic agents.
  • Agents which cause the loss of sensation are called as anesthetic agents.
These are of two types;
Local
  • These cause loss of sensation but animal is conscious.
General
  • These cause loss of sensation due to unconsciousness.
Objectives of Anesthesia
  • Sensory block to have analgesia. In this, sensory stimuli from the periphery are blocked.
  • Mental block to have hypnosis or Amnesia (animal know nothing, what is happening around). Activity of CNS is blocked.
  • Motor block to have muscle relaxation
  • Reflex block to have hyporeflexia
  • In case of local anesthetics, only one purpose is not the case of interest which is the mental block.
Stages of Anesthesia
  • Based on ether anesthesia, there are following stages of anesthesia;
  • Excitement stage (voluntary movements occur)
  • Delirium stage (involuntary movements occur)
  • Surgical Stage
  • Medullary paralysis
There are 3 stages of anesthesia;
  • Induction
  • Maintenance
  • Recovery
Ideal Properties of Anesthetic Agent
  • It should cause rapid & smooth induction and recovery.
  • It should be easy to maintain anesthesia (light or deep).
  • It should be non-toxic and safe to internal organs.
  • It should be non-irritant.
  • It should be non-inflammable and non-explosive.
  • Myocardial sensitization to epinephrine should be least.
  • It should be compatible with other drugs.
  • It should be easily available, cheap and easy to administer.
Pre-anesthetic Agents
These are the drugs given before anesthesia.
Why to give?
  • To reduce anxiety of patient
  • To reduce the amount of anesthetic agent
  • To reduce the adverse effects of anesthetic agent
  • To reduce the toxicity problems
  • To reduce secretions especially Bronchial & Salivary
  • To increase analgesia
Examples
  • Opiods (Morphine, Mepridine) which induce analgesia
  • Tranquilizers (Xylazine, Acepromazine) which reduce anxiety
  • Anticholinergic drugs (Atropine sulphate, scopolamine) which reduce secretions
  • Muscle relaxants (Gallamine, Pancuronium, d-tubocurarine, succinylcholine)
Medication during Anesthesia
  • To reduce Blood pressure
  • To induce muscle relaxation
  • To stop bleeding
Post-Anesthetic Medication
  • Analgesics
  • Anti-inflammatory
  • Anti-microbial
  • Cholinergic drugs to relieve retention of urine E.g. Bethanicol

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