General anesthesia progresses through four stages: I) analgesia, where the patient feels drowsy and numb; II) excitement, where the patient may feel agitated or delirious; III) surgical anesthesia, the target stage where painful stimuli do not elicit reflexes or autonomic responses; and IV) impending death, where breathing and circulation fail and death occurs if not treated. The ideal anesthetic agent allows quick progression from initial feelings of numbness to unconscious surgical anesthesia without inducing excitement or life-threatening paralysis.

1. Stages of GENERAL
ANESTHESIA
Medicinal chemistry
Reference :- Wilson and Giswolds
textbook of organic medicinal and
pharmaceutical chemistry

2. General Anesthesia
•Clinical definition; “General Anesthesia is a
state where no movement occurs in response
to what should be painful.”

3. Stages of General Anesthesia
1.Analgesia (stage I)
2.Excitement (Stage II)
3.Surgical Anesthesia (Stage III)
4.Impending Death (Stage IV)

4. Analgesia (stage I)
•The Stage of analgesia lasts from onset of
drowsiness to loss of eyelash reflex (blinking when
the eyelash is stroked ) .
•Variable levels of amnesia and analgesia are seen
in this stage I .
•The patient is considered unconscious at the end of
stage I .

5. Excitement (Stage II)
•The stage of excitement is characterized by agitation and
delirium .
•During this stage , salivation may be copious .
•Heart rate and respiration may be irregular.
•Induction agents are designed to move the patient through
this undesirable stage quickly .

6. Surgical Anesthesia (Stage III)
•This stage of anesthesia is the target depth
for this procedure .During this stage , a
painful stimuli will not elicit a somatic reflex
or deleterious autonomic response .

7. Impending Death (Stage IV)
•This stage lasts from onset of apnea to
failure of circulation and respiration and
ends in death.

8. Note:-
•The ideal anesthetic combination will
allow the patient to proceed quickly from
stage I to stage III and avoid stage IV .

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