Stages of Anaesthesia with and without premedication

 There is four Stages of Anesthesia are the following: 

1. Stage I – Analgesia (Induction)

·  Onset: From administration to loss of consciousness.

·  Patient is conscious, may be drowsy, has reduced pain sensation, but can still communicate.

·  Reflexes are intact.

·  Breathing is regular.

Premedication effect: Sedatives or anxiolytics may make the transition to Stage II smoother and less distressing. 

Without Premedication	With Premedication
Patient may be anxious, restless, fearful.	Patient is calm, drowsy, and less anxious (due to sedatives).
Slower onset of analgesia and sedation.	Faster and smoother induction due to synergistic effects.
Patient may resist mask or IV.	Cooperation is improved.

- Drugs used: Midazolam (sedation), Morphine (analgesia), Atropine (dry secretions).

 

2. Stage II – Excitement / Delirium

·  From loss of consciousness to onset of regular breathing.

·  Patient becomes unconscious, but reflexes (cough, gag, swallowing) may be hyperactive.

·  May exhibit irregular breathing, muscle movements, pupil dilation, or vomiting.

·  Dangerous stage due to risk of laryngospasm or vomiting and aspiration.

Premedication effect: Anticholinergics reduce secretions; benzodiazepines reduce agitation and hallucinations. 

Without Premedication	With Premedication
High risk of irregular breathing, vomiting, laryngospasm.	Smoother transition, fewer muscle movements or airway reflexes.
Increased secretions (saliva, mucus).	Reduced secretions (anticholinergics like atropine or glycopyrrolate).
May experience vivid dreams, agitation, or involuntary movements.	Sedatives reduce chances of delirium and hallucinations.

-This stage is the most dangerous if unmedicated; premedication minimizes risks.

 

3. Stage III – Surgical Anaesthesia

·  Ideal stage for surgery.

·  Divided into four planes (depths):

1. Plane 1: Regular respiration, some reflexes present.
2. Plane 2: Loss of reflexes, regular respiration.
3. Plane 3: Diaphragmatic breathing only.
4. Plane 4: Intercostal paralysis – dangerous, close to overdose.

Premedication effect: Often allows for a smoother induction and helps maintain a stable level within this stage.

 

Without Premedication	With Premedication
More anaesthetic needed to maintain depth.	Lower dose of anaesthetic needed due to additive effects.
Vital signs may fluctuate.	More stable vital signs (heart rate, BP, respiration).
Reflexes may return if depth is inadequate.	Deeper and more consistent anaesthesia.

-Muscle relaxants may also be used as part of premedication or induction.

4. Stage IV – Medullary Paralysis (Overdose)

·  From respiratory arrest to death if not reversed.

·  Severe depression of the respiratory and vasomotor centers in the brainstem.

·  No reflexes, no breathing, hypotension, dilated pupils – immediate resuscitation required.

Premedication effect: No direct prevention, but careful dosing and monitoring can help avoid this stage. 

Without Premedication	With Premedication
Harder to detect early warning signs due to chaotic progression.	Easier to monitor and control depth; overdose is less likely.
Emergency may arise due to poor planning or rapid administration.	Risk minimized due to planned dosing and smoother progression.

Premedication helps avoid this stage but cannot treat it—resuscitation is required.

Presentation for Stages of Anaesthesia with and without premedication

   

                                                                  END OF THE CHAPTER

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