Stages of Anesthesia

Study Notes

Stages of Anesthesia

Anesthesia progresses through stages, with each stage showing a progressive decrease in pain, perception, motor coordination, consciousness, reflexes, muscle tone, and cardiopulmonary function. Stage 3 (S3,P2) is ideal for surgery.

Stage 1: Voluntary Excitement

Marks the beginning of induction into unconsciousness.
Patients can move voluntarily.
Typical signs include fear, excitement, disorientation, struggling, urination, and defecation.
Heart rate and breathing rate increase.
This stage is undesirable due to its involuntary nature.

Stage 2: Involuntary Excitement

Characterized by involuntary movements and excitement; delirium and agitation will present.
Irregular breathing, salivation, vomiting, urination, and defecation might occur.
Vocalization, struggling, paddling may be observed.
Increased heart rate and breathing rate.
Pupils dilate; nystagmus is possible.
Muscles are tense; reflexes are present, but jaw tone is strong (making intubation difficult).
Ends with muscle relaxation, decreased breathing rate, and decreased reflexes.
Rapid progression through stages 1 and 2 is crucial. Adjust IV anesthetic administration to minimize time spent in these stages.
Dissociative anesthetics (e.g., ketamine) can bypass these stages quicker.

Stage 3: Surgical Anesthesia

The ideal stage for surgical procedures; characterized by the absence of movement in response to stimuli, progressive loss of reflexes (eye, jaw, pedal, anal (large animals), autonomic reflexes).
Consists of four planes.

Plane 1

Suitable for non-surgical procedures.

Plane 2: Surgical Anesthesia

Regular, shallow breathing with reduced rate.
Mild decrease in blood pressure and heart rate.
Relaxed muscle tone; swallowing reflex absent.
Eyes rotate ventrally.
Weak or absent palpebral (eyelid) and pedal reflexes.
Surgical stimuli might mildly increase heart rate, blood pressure, and respiratory rate.
Sluggish or absent pupillary light reflex; moderate pupil size.

Plane 3: Too Deep, Dangerous

Depressed cardiovascular and respiratory function (low heart rate, breathing rate, reduced tidal volume).
Reduced pulse strength and increased capillary refill time (CRT).
Absent palpebral and pedal reflexes.
Central eyeballs; moderately dilated pupils.
Weak corneal reflex; dry cornea.
Very relaxed muscle tone; absent jaw tone.
Reflex Responses: Described as present (brisk), decreased, or absent.

Management of Anesthetic Complications

Hypoventilation can be managed by manual or mechanical ventilation.
Hypotension, though possibly an adverse effect, can occur at lighter planes due to other anesthetic drugs.

Description

This quiz covers the various stages of anesthesia, focusing on the physiological changes occurring from induction to surgical anesthesia. It explores the characteristics of each stage, including voluntary and involuntary excitement, and the implications for patient care during anesthesia. Understand the importance of Stage 3 for surgical procedures.