Guedels stag3 of anaesthesia
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Guedel stage 3 surgical anaesthesia four planes detailed signs pupils respiration
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I have enough information from both the textbook (Katzung's Basic and Clinical Pharmacology) and web sources (Wikipedia, MedicoNotebook, StatPearls) to give a comprehensive answer on Guedel's Stage 3.
Guedel's Stage III — Surgical Anaesthesia
Described originally for diethyl ether induction (with morphine + atropine premedication), Stage III is defined as the period from the onset of automatic (regular) respiration to complete cessation of spontaneous respiration (apnea).
It is the stage at which surgery is performed, and is subdivided into four planes based on progressive changes in ocular movements, eye reflexes, pupil size, and respiratory muscle activity.
The Four Planes of Stage III
| Sign | Plane I | Plane II | Plane III | Plane IV |
|---|---|---|---|---|
| Eyeball movement | Present (oscillating/roving) | Ceases (fixed, central) | Fixed | Fixed |
| Eyelid reflex | Lost | Lost | Lost | Lost |
| Conjunctival reflex | Lost at bottom of plane | Lost | Lost | Lost |
| Corneal reflex | Present | Lost | Lost | Lost |
| Lacrimation | Present | Increased (sign of light anaesthesia) → decreases | Absent | Absent |
| Pupil size | Normal/mildly dilated | Moderate dilatation | Dilated, light reflex abolished | Maximally dilated |
| Laryngeal reflex | Present | Lost | Lost (but can be provoked by cervical/anal dilatation) | Lost |
| Swallowing reflex | Lost | Lost | Lost | Lost |
| Respiration | Automatic, regular | Automatic, regular | Diaphragmatic only (intercostal paralysis progressing) | Diaphragmatic → apnea |
| Intercostal muscles | Active | Beginning paralysis | Progressive → complete paralysis | Complete paralysis |
| Response to skin stimulation | Present | Lost | Lost | Lost |
Plane-by-Plane Detail
Plane I — Onset of automatic respiration → cessation of eyeball movements
- Eyelid reflex lost, swallowing reflex disappears
- Eyeballs may show marked oscillating/roving movements
- Conjunctival reflex lost at the bottom of this plane
- Respiration: automatic and regular
- This marks the entry into safe surgical anaesthesia — eyeball oscillation indicates an adequate but not overly deep level
Plane II — Cessation of eyeball movements → beginning of intercostal muscle paralysis
- Eyeballs now fixed and central
- Corneal reflex lost
- Laryngeal reflex lost (though upper respiratory inflammation raises irritability)
- Lacrimation increases (a useful clinical sign of light anaesthesia in this plane)
- Respiration: automatic and regular; no movement or deep breathing response to skin stimulation
- Most minor and moderate surgery performed here
Plane III — Beginning → completion of intercostal muscle paralysis
- Diaphragmatic respiration persists but intercostal muscles are progressively then completely paralysed
- Pupils dilated, light reflex abolished
- Laryngeal reflex is lost, but can still be triggered by painful stimuli from cervical or anal dilatation
- This was the preferred plane for major surgery before neuromuscular blocking agents were available (allowing adequate abdominal relaxation)
Plane IV — Complete intercostal paralysis → diaphragmatic paralysis (apnea)
- Diaphragm progressively paralysed → apnea
- Pupils maximally dilated, all reflexes absent
- Merges into Stage IV (medullary depression / overdose)
- Dangerous zone — border of anaesthetic overdose
Key Clinical Mnemonics / Points
- Entry into Stage III is signalled by: onset of regular automatic breathing + eyeball oscillation
- Eyeball oscillation = safe surgical plane (not too deep)
- Eyeball fixation = deeper plane; watch for depth
- Pupil dilatation + loss of light reflex = Plane III or beyond → dangerously deep
- Increased lacrimation = light anaesthesia (Plane II)
- The progression through planes follows: eye signs → respiratory muscle signs
Important Caveats
- Guedel's classification was based on ether with morphine/atropine premedication — stages may not be clearly demarcated with modern agents (propofol, sevoflurane, etc.)
- Neuromuscular blocking drugs eliminate the respiratory muscle signs, making traditional Guedel monitoring unreliable
- Modern anaesthesia uses balanced techniques (IV agents + volatiles + NMBDs) where clinical signs are partially masked; depth is now monitored with BIS (Bispectral Index) or other EEG-based monitors
- Katzung's Basic and Clinical Pharmacology, 16th Ed., p. 701
- Guedel's Classification — Wikipedia / StatPearls (NCBI Bookshelf)
Guedels stage of anaesthesia in MD anaesthesia. ..Make a ppt
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