5- General Anesthetics
A- Intro
1- General anesthesia was first used in mid 1800s when Diethyl ether was discovered as a
general anesthetic and William Morton used it for neck tumor
surgery.
2- General anesthetics cause loss of all senses ( pain ) with
reservable loss of consciousness, muscular relaxation and
loss of sensory and autonomic reflexes.
3- Properties of ideal general anesthetics:
‣ Smooth & rapid loss of consciousness // prompt recovery on discontinuation // wide margin of
safety // No adverse effects.
‣ No drug currently have all of these characteristics -> we use combination of inhaled and IV
drugs to get the favorable properties of each drug while minimizing AE.
Because of the more rapid onset of action
4- Stages of anesthesia: of modern i.v and inhaled anesthetics,
distinctive signs of each of the four stages
are obscured
‣ Stage I : Analgesia
• Patis have analgesia without amnesia -> later both happen
‣ Stage II : Excitement (combative behavior – dangerous state)
• Patis are delirious and amnesic with irregular breathing ( volume and rate ) and retching
and vomiting can happen -> The goal is to limit this stage which ends with stable breathing.
‣ Stage III : Surgical anesthesia
• It begins when breathing is regular and extends till spontaneous respiration occur.
, • This stage is described in terms of ocular movement, eye reflexes and pupil size.
‣ Stage IV : Medullary paralysis (respiratory and vasomotor control ceases)
• When spontaneous respiration ceases. Severe depression of vasomotor and resp center and
without circulatory and respiratory support death XD.
• The margin between Stage III and fatal resp and circulatory depression is narrow -> we
need a careful monitoring by an anesthetist
5-Classification Of general anesthetics:
‣ Inhaled // IV
B- Inhaled GAs
The rate at which a therapeutic concentration of
the anesthetic is achieved in the brain depends on the
1- Pharmacokinetics
following parameters
1- Vatatile liquids
◦Older
‣ Ether:
‣ UPTAKE & DISTRIBUTION • First anesthetic
• Liquid at room temp and vaporized easily
• In ammable, explosive and irritating
‣ Chloroform
• Solubility: • 2nd anesthetic
• Pleasant odor, nonin ammable
• Hepatotoxic and severe CV depressant
◦Halogenated hydrocarbons
◦The concentration of a gas in blood is equal to its ‣ Halothane
‣ Methoxy urane
‣ En urane
‣ Iso urane
‣ Des urane
partial pressure/ tension. ‣ Sevo urane
2- Gases
◦Nitrous oxide
◦Cyclopropane
◦Blood ( gaz partition coefficient ) is the ‣ Accidentally discovered -1929
‣ Flammable & explosive
anesthetics relative affinity to blood compared to
other gases -> Low solubility ->few molecules dissolve in blood to
rise partial pressure equilibrium ( NO )
-> high solubility -> more molecules need to dissolve to rise the blood
partial pressure ( Halothane, isoflurane)
• Anesthetic concentration in the inspired air
◦If increases -> increase the rate of induction ( rate of gas
fl
A- Intro
1- General anesthesia was first used in mid 1800s when Diethyl ether was discovered as a
general anesthetic and William Morton used it for neck tumor
surgery.
2- General anesthetics cause loss of all senses ( pain ) with
reservable loss of consciousness, muscular relaxation and
loss of sensory and autonomic reflexes.
3- Properties of ideal general anesthetics:
‣ Smooth & rapid loss of consciousness // prompt recovery on discontinuation // wide margin of
safety // No adverse effects.
‣ No drug currently have all of these characteristics -> we use combination of inhaled and IV
drugs to get the favorable properties of each drug while minimizing AE.
Because of the more rapid onset of action
4- Stages of anesthesia: of modern i.v and inhaled anesthetics,
distinctive signs of each of the four stages
are obscured
‣ Stage I : Analgesia
• Patis have analgesia without amnesia -> later both happen
‣ Stage II : Excitement (combative behavior – dangerous state)
• Patis are delirious and amnesic with irregular breathing ( volume and rate ) and retching
and vomiting can happen -> The goal is to limit this stage which ends with stable breathing.
‣ Stage III : Surgical anesthesia
• It begins when breathing is regular and extends till spontaneous respiration occur.
, • This stage is described in terms of ocular movement, eye reflexes and pupil size.
‣ Stage IV : Medullary paralysis (respiratory and vasomotor control ceases)
• When spontaneous respiration ceases. Severe depression of vasomotor and resp center and
without circulatory and respiratory support death XD.
• The margin between Stage III and fatal resp and circulatory depression is narrow -> we
need a careful monitoring by an anesthetist
5-Classification Of general anesthetics:
‣ Inhaled // IV
B- Inhaled GAs
The rate at which a therapeutic concentration of
the anesthetic is achieved in the brain depends on the
1- Pharmacokinetics
following parameters
1- Vatatile liquids
◦Older
‣ Ether:
‣ UPTAKE & DISTRIBUTION • First anesthetic
• Liquid at room temp and vaporized easily
• In ammable, explosive and irritating
‣ Chloroform
• Solubility: • 2nd anesthetic
• Pleasant odor, nonin ammable
• Hepatotoxic and severe CV depressant
◦Halogenated hydrocarbons
◦The concentration of a gas in blood is equal to its ‣ Halothane
‣ Methoxy urane
‣ En urane
‣ Iso urane
‣ Des urane
partial pressure/ tension. ‣ Sevo urane
2- Gases
◦Nitrous oxide
◦Cyclopropane
◦Blood ( gaz partition coefficient ) is the ‣ Accidentally discovered -1929
‣ Flammable & explosive
anesthetics relative affinity to blood compared to
other gases -> Low solubility ->few molecules dissolve in blood to
rise partial pressure equilibrium ( NO )
-> high solubility -> more molecules need to dissolve to rise the blood
partial pressure ( Halothane, isoflurane)
• Anesthetic concentration in the inspired air
◦If increases -> increase the rate of induction ( rate of gas
fl
