Stages of Anesthesia

Lectures in Veterinary Anesthesia

Muneer S. Al-Badrany

Stages of Anesthesia:

Stage I: Induction Stage Or Voluntary Excitement Animal Conscious, may make forcible efforts to avoid anesthesia, fear lead to increase R.R, PR, Dilation Pupils, Animals may be defected, uninitiated
Stage II: Involuntary Excitement animals loss consciousness, Reflex response to stimuli is exaggerated . Dog may Whimper Howl, cats swear, Horses neigh. Res. Irregular Swallowing & Vomiting Cough reflex present
More dangerous stages, The anesthetist aim archive stage 3 as smoothly and quickly as possible, when given premedication it help to achieve this goal.

Lectures in Veterinary Anesthesia

Muneer S. Al-Badrany





Stages of Anesthesia:
Stage III: Surgical Stage

Plane I: Light anesthesia

Plane II: Medium deep anesthesia

Plane III: Deep anesthesia

Stage IV Anesthetic overdose:

Plane IV: Excessive deep anesthesia

Regular automatic breathing and cessation all limb movement , eye move from side to side . Palperpral, Conjunctiva, Corneal reflex disappear
Minor operation
R. Rate increase and amplitude decrease, laryngeal reflex persist, eye ball fixed centrally , pedal reflex dog sluggish ( All operation except abdomen surgery
R. Rate increase, depth decrease, all reflex including pedal reflex disappear
Paralysis thoracic muscle, jerkey movement of diaphragm , pulse become rapid pupil dilated eyeball present a fish eye , Cyanosis appear indicate heart failure

Lectures in Veterinary Anesthesia

Muneer S. Al-Badrany

Lectures in Veterinary Anesthesia

Muneer S. Al-Badrany

• ♦ Heart rate

• Palpation of arterial pulse
• Oesophageal stethoscope
• ECG
• Blood pressure monitor
• Pulse oximeter
• ♦Tissue perfusion
• Mucus membrane colour
• Capillary refilling time
• Bleeding at operative site
• Urine out put
• ♦ Arterial blood pressure
• Palpation peripheral pulse
• Doppler ultrasound method
• Oscillometric method
• Arterial catheterization
Table : Method of assessing cardiovascular function in anesthetiazied animal.


Lectures in Veterinary Anesthesia

Preanesthetic medications

♣To aid in the restraint of the animal by quieting the patient,

educing anxiety, and decreasing hyperactivity
♣ To reduce or minimize pain, especially if the animal has suffered a fractured limb and must be moved or manipulated before anesthetic induction
♣ To facilitate the induction phase of general anesthesia by eliminating or re­ducing the excitatory stage. These drugs also help to reduce delirium and excitement during the recovery from general anesthesia.
♣ To minimize the vagal-mediated reflexes associated with the depressant action of general anesthetics and intubation of the trachea.
♣ To increase the effects of the general anesthetic drug in order to decrease the total amount of anesthetic drug needed to produce and maintain anesthesia
♣ To aid in the performance of local analgesia techniques by providing sedation and reducing anxiety