Stages of General Anesthesia

Stages of General Anesthesia

Four main stages of general anesthesia are recognized regardless of the method in which the anesthesia is delivered. These stages are based upon the patient's body movements, respiratory rhythm, oculomotor reflexes, and muscle tone. First Gudel used in assessment of stages of anesthesia using ether historic inhalation anesthesia and now it is prove useful in your assessment of the patient under general anesthesia with halogenated inhalational anesthetic agents(e.g., pediatric inductions with halothane).These signs will not be helpful if you are performing an anesthetic with intravenous anesthetics and using muscle relaxants. Atropine may affect the pupillary size and make eye size unusable size. During recovery from an inhaled general anesthetic, the stages will be reversed as the patient regains consciousness

Stage 1 - Amnesia and Analgesia Stage

is conscious and rational, however the perception of pain is diminished. The first stage occurs from the beginning of the anesthetic to the loss of consciousness. During this stage the patient will demonstrate the following:

• Able to open eyes on command
  
• Breathe normally
• Maintain protective reflexes
• Tolerate mild painful stimuli

Stage 2 - Delirium Stage

The second stage starts with the loss of consciousness. It ends with the appearance of a regular pattern of breathing and loss of eye lid reflex. During this stage excitement is noted. Children will often exhibit this stage during an inhaled induction. The patient may demonstrate the following during this stage:

• Movement of limbs and tense struggle
  
• Irregular breathing
• Breath holding
• Pupils become dilated but reactive to light

Stage 3 - Surgical Anesthesia

This stage begins with the resumption of a regular breathing pattern and ends at the cessation of respiration. Surgery generally occurs during one of the four levels of stage 3. There will be no response to surgical incision at this stage.

Level 1: The patient may exhibit the following signs during this level:

• Pupillary dilatation may occur but the pupils will become smaller
• Absence of pupillary reaction to light
• Eye lid reflex disappears
• Respiration is regular
• Vomiting reflex is abolished

Level 2: The patient may exhibit the following signs during this level:

• Eyes become fixed in the midline
• Decrease in the activity of the intercostal and thoracic muscles during respiration
• Laryngospasm reflex disappears
• General muscle tone becomes more flaccid

Level 3: The patient may exhibit the following signs during this level:

• Intercostal muscle activity decreases to the point of cessation
• Respiration may come from only the diaphragm
• Pupils become more dilated

Level 4: The patient may exhibit the following signs during this level:

• Paralysis of intercostal muscles
• Cessation of spontaneous respiration
• Pupils become very dilated

Stage 4 - Anesthetic Overdose

This stage represents an overdose. Action must be taken to decrease the inhaled anesthetic otherwise cardiac arrest may occur. The patient may exhibit the following signs:

• Cessation of spontaneous respiration
  
• Severe bradycardia and hypotension
• Cardiac arrest
• Absence of all reflexes