- 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;
- These cause loss of sensation but animal is conscious.
- 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;
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.
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
- 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
- Cholinergic drugs to relieve retention of urine E.g. Bethanicol