Arthur Guedel described these stages based on the use of ether. While modern balanced anaesthesia has made these stages less distinct, they remain fundamental for understanding the depth of anaesthesia.
| Stage | Name | Clinical Features |
|---|---|---|
| I | Analgesia | From induction to loss of consciousness. Amnesia and analgesia occur. |
| II | Excitement | From loss of consciousness to the onset of automatic breathing. Characterized by struggling, irregular breathing, and potential airway reflex hyper-reactivity. |
| III | Surgical Anaesthesia | From the onset of automatic respiration to the cessation of spontaneous breathing. Divided into 4 planes based on eye signs, muscle tone, and respiration. |
| IV | Overdose | From cessation of respiration to circulatory collapse and death. |
High-Yield Clinical Notes:
- Stage II Avoidance: Modern Rapid Sequence Induction (RSI) is specifically designed to bypass the “Excitement Stage” rapidly, preventing risks like laryngospasm, vomiting, and aspiration.
- Current Relevance: In clinical practice today, we aim to maintain patients in Stage III, Plane 1 or 2, balancing the depth of anaesthesia against hemodynamic stability.
For more high-yield resources and free medical questions, visit mymedschool.org.