Guedel identified 4 separate stages to anesthesia, based on clinical findings. The third stage used for general surgery. and is divided into 4 planes. This was useful when anesthetics such as ether and chloroform were used, but is less useful today due to the use of muscle relaxants and other agents.
Clinical parameters assessed:
(1) respiration
(2) pulse
(3) pupil size, which is affected by the presence of concurrent medications
(4) eyeball activity
(5) reflexes
(6) skeletal muscle tone
|
Stage |
Descriptive |
|
Stage I |
analgesia, disorientation |
|
Stage II |
delerium, agitation, excitement |
|
Stage III |
surgical |
|
Stage IV |
medullary paralysis, moribund |
|
Stage |
Respirations and Pulse |
Ocular Findings (no medications) |
Reflexes and Skeletal Muscle Tone |
|
Stage I |
normal or panting respirations (20-30 breaths/min); heart rate unchanged |
voluntary eyeball activity, normal pupillary size |
all reflexes intact; normal muscle tone |
|
Stage II |
respirations irregular, with apneic episodes or period of hyper-ventilation; mild tachycardia |
eyeball may be centrally positioned or show nystagmus; possible dilatation of the pupils |
all reflexes intact and some may be exaggerated; muscle show uninhibited activity; vomiting may occur at interface with Stage III |
|
Stage III, Plane 1 (light anesthesia) |
respiration regular with rate 12-20 breaths per minute; pulse strong and > 90 beats per minute |
eyeballs centrally placed or nystagmus present; normally pupillary size |
some reflexes negative with others variable; swallowing may be poor or absent; slight skeletal muscle relaxation |
|
Stage III, Plane 2 (medium, surgical anesthesia) |
respirations shallow with rate 12-16 breaths per minute; heart rate > 90 beats per minute; may respond to surgical activity |
eyeballs may be ventrally rotated; pupillary size moderately dilated |
most reflexes negative with variable corneal and peritoneal reflexes; reflexes sluggish if present; moderate skeletal muscle relaxation |
|
Stage III, Plane 3 (deep anesthesia) |
respirations shallow with rate < 12 breaths per minute; heart rate 60-90 beats per minute; no response to surgical activity |
eyeballs may be centrally placed or ventrally rotated; pupillary size moderately dilated; may be fixed |
all reflexes diminished or absent; moderate skeletal muscle relaxation |
|
Stage III, Plane 4 (overdose) |
respirations jerky; heart rate < 60 beats per minute; no response to surgical activity |
centrally positioned eyeballs; pupillary size widely dilated and fixed |
all reflexes absent; marked skeletal muscle relaxation |
|
Stage IV |
loss of thoracic breathing; cardiovascular collapse |
centrally positioned eyeballs; pupillary size widely dilated and fixed |
all reflexes absent; extreme skeletal muscle relaxation (flaccid) |
The respiratory rate and cardiovascular findings are those for a normal person. A person in shock or with other concurrent disease may differ.
Effect of other medications on pupil size:
• The use of morphine may constrict the pupils in Stage I, Stage III Plane 1, and Stage III Plane 2.
• The use of atropine with morphine will tend to mitigate the constrictions listed above, but will be somewhat smaller than if no medications given, except in Stage IV.
The use of muscle relaxants removes the ability to judge the depth based on muscle tone.
Some of the reflexes which might be used:
(1) corneal
(2) pupillary response to light
(3) conjunctival
(4) pharyngeal
(5) laryngeal
(6) cutaneous
(7) peritoneal
Specialty: Anesthesiology
ICD-10: ,
