Chapter 78: Stages and Signs of General Anesthesia – Flashcards
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The definition of general anesthesia is the induction of a loss of consciousness by pharmacological means such that the patient is unarousable to verbal, tactile, or painful stimuli. List the primary goals of GA.
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Amnesia Sedation/hypnosis Analgesia Areflexia (motionlessness) Attenuation of autonomic (sympathetic) nervous system responses
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In 1846, Dr. William Morton gave the first public demonstration of general anesthesia by which agent?
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ether... diethyl ether
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Dr. Arthur Guedel, during the 20's and 30's was the first to describe the stages of general anesthesia or the different depths of anesthesia and the signs at each level. All the stages are based on the administration of a single volatile agent, diethyl ether, which is no longer used today.
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The "balanced anesthesia" used today (which uses multiple classes of drugs like IV anesthetics, opioids, benzos, NMJ blockers) mask the classical clinical signs of each of Guedel's stages. Therefore many consider these stages to be obsolete, but some still find the stages useful for when the patient is emerging from anesthesia or with purely inhalational inductions in children.
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In one word for each stage, what are the 4 stages of general anesthesia?
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1. Disorientation 2. Excitation 3. Surgical Anesthesia 4. Overdose
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Stage 1 is also called the "- stage". When does it begin and end? What are some of the signs?
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the "induction stage" It begins with the initial administration of anesthesia and ends with the loss of consciousness. Signs: sedation, some analgesia, and eventually amnesia. The patient should still be able to maintain a conversation Respiration is slow but regular. The eyelid is intact.
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Stage 2 is defined when?
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Its the period immediately after the loss of consciousness until regular spontaneous ventilation resumes.
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What are some signs of Stage 2?
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disinhibiton delirium uncontrolled spastic movements The eyes will show a loss of lash reflex, divergent gaze, and reflex pupillary dilatation. The airway is more irritable and has a lot of secretions and therefore there is more coughing, vomiting, laryngospasm, and bronchospasm. Respirations are irregular with breath holding. Hypertension and tachycardia are common.
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Because of the risk of clinically significant airway compromise, anesthetics these days, like propofol, minimize the time spent in stage 2...
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All patients emerging from inhalation anesthetic and kids with an inhalation induction will show signs of this stage.
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What cannot be done during stage 2?
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Endotracheal intubation and extubation should never occur during stage 2. External stimulation, particularly of the airway, should be kept to a minimum.
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What is the beginning and end of Stage 3 of anesthesia?
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Surgical Anesthesia: begins when the patient resumes spontaneous respirations and ends with respiratory paralysis.
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Stage 3 is the target level of surgical anesthesia. What is it safe to do in stage 3 now?
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Stage 3 is when its appropriate to intubate a patient without NMJ blockers.
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What are some general signs of Stage 3?
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cessation of eye movement skeletal muscle relaxation respiratory depression
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Stage 3 of anesthesia is divided into 4 planes. Describe Stage 3 plane 1.
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Plane 1: Regular spontaneous breathing. Eyelid, conjunctival, swallowing reflexes disappear. Ocular muscles are less active. The pupils are constricted with a central gaze.
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What happens during Stage 3, Plane 2?
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Plane 2: Tears increase. Slight pause between inhale and exhale. Additional reflexes, corneal and laryngeal, are lost. Eyeball movements cease completely. Intercostals begin to weaken.
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What happens during Stage 3, Plane 3?
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Plane 3: Intercostals and abdominal muscles completely relax so ventilation is solely controlled by the diaphragm. The light reflex is lost... surgical anesthesia has now been achieved.
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What happens during Stage 3, Plane 4?
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Plane 4: Respirations become irregular and shallow with paradoxical rib cage movement (as a result of complete intercostal muscle paralysis)... eventually apnea results from full paralysis of the diaphragm.
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What is the start and end of Stage 4?
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Stage 4 begins with cessation of respirations and ends with death. An overdose of anesthetic, relative to the degree of surgical stimulation, results in severe medullar depression leading to death unless support is provided. (otherwise respiratory arrest and cardiovascular collapse result).
