Mastering General Anesthetic Agents

Thiopentone Sodium

• A barbiturate that is used as an intravenous anesthetic.
• It is a potent hypnotic agent that produces a rapid onset of anesthesia.
• Thiopentone sodium is metabolized in the liver and has a short duration of action.
• It is commonly used for induction of anesthesia and as a sedative for short procedures.

Methohexital/Methohexitone

• This drug is a barbiturate used for intravenous anesthesia.
• It is a short-acting anesthetic that produces a rapid onset of anesthesia.
• Methohexital is metabolized in the liver.
• It is commonly used for induction of anesthesia for short procedures.

Benzodiazepines

• This class of drug is used as intravenous anesthetics.
• They are used primarily for sedation and amnesia.
• Benzodiazepines have a slower onset of action than barbiturates.
• They are metabolized in the liver.
• Common examples are midazolam and diazepam.

Etomidate

• An anesthetic used intravenously.
• It produces rapid onset of anesthesia.
• Etomidate is metabolized in the liver.
• It is often used for induction of anesthesia in patients with cardiovascular disease.

Propofol

• A hypnotic agent used as an intravenous anesthetic.
• It has a rapid onset and short duration of action.
• Propofol is metabolized in the liver.
• It is commonly used for induction and maintenance of anesthesia.

Opioid Agonists

• These drugs are used intravenously as anesthetics.
• Their primary use is to provide analgesia during anesthesia.
• Opioid agonists are used in combination with other anesthetic agents.
• Examples include fentanyl, sufentanil, and remifentanil.

Ketamine

• An intravenous anesthetic that has dissociative properties.
• Ketamine can be used as an induction agent or as a maintenance anesthetic for short procedures.
• It is metabolized in the liver.
• It is particularly useful in situations where it is important to maintain airway reflexes.

Desirable Criteria for General Anesthetics

• A good general anesthetic should have a rapid onset of action.
• It should be potent and have a short duration of action.
• The anesthetic should be safe and have minimal side effects.

Important Sites of Action for Anesthetics

• Central Nervous System (CNS)
• Peripheral Nervous System (PNS)
• Spinal Cord

Nitrous Oxide

• It has analgesic and amnesic properties.
• It is a weak general anesthetic that can be used in combination with other agents.
• Nitrous oxide is easily administered by inhalation.

Diethyl Ether

• It has been used as a general anesthetic for many years.
• Diethyl ether has several disadvantages, which include its flammable nature.
• It has a pungent odor, and it can cause a prolonged recovery period.

Halothane

• Commonly used anesthetic agent that is administered by inhalation.
• Halothane has some disadvantages, such as its hepatotoxicity.
• It can cause cardiac arrhythmias.

Enflurane

• An inhaled general anesthetic.
• It is commonly used for induction and maintenance of anesthesia.
• Enflurane is non-flammable, but it has a disadvantage of being a potent trigger for seizures.

Isoflurane

• Another inhaled general anesthetic.
• Isoflurane is non-flammable.
• The disadvantage is that it may cause hypotension and tachycardia. It is also a potent trigger for malignant hyperthermia.

Intravenous Anesthetics

• These anesthetics are rapidly injected into the bloodstream.
• They are often used to induce anesthesia, especially in situations where rapid onset is required.

Thiopentone Sodium

• It can produce a quick onset of anesthesia.
• The disadvantage is that it has a short duration of action.

Diethyl Ether

• It has a prolonged recovery time.
• It has a pungent odor and can cause nausea and vomiting.

Administration of General Anesthetic Agents

• General anesthetic agents are administered by inhalation or intravenously.

Clinical Characteristics of General Anesthetics

• Nitrous Oxide: Anesthetic; analgesic properties
• Halothane: Anesthetic; potent, metabolized in the liver
• Desflurane: Anesthetic; rapid onset, short duration, low blood solubility, non-flammable
• Sevoflurane: Anesthetic; non-flammable, rapid onset, short duration
• Isoflurane: Anesthetic; potent, non-flammable, metabolized in the liver
• Enflurane: Anesthetic; potent, non-flammable, metabolized in the liver

Mechanism of Action of Anesthetics

• General anesthetic agents inhibit neurotransmission by increasing the inhibitory effects (GABA) in the central nervous system (CNS).

Anesthetic Associated with Major Toxicity

• Halothane can cause hepatotoxicity.

Intravenous Anesthetics

• Thiopentone sodium is a barbiturate intravenous anesthetic.

Major Indication for the Use of Benzodiazepines

• Sedation, amnesia, and anxiety relief before surgery

Major Clinical Characteristic of General Anesthesia

• General anesthesia is a reversible loss of consciousness and responsiveness.

Main Effect of General Anesthesia on the CNS

• General anesthetics act on the brain to reduce neuronal activity and cause unconsciousness.

Routes of Administration for General Anesthetics

• Inhalation
• Intravenous

Purpose of General Anesthetic Agents

• To produce a loss of consciousness, analgesia, and muscle relaxation for surgery.

Inhalational Anesthetic Agents

• Halothane
• Enflurane
• Isoflurane
• Desflurane
• Sevoflurane

Toxicities associated with Nitrous Oxide and Halogenated Anesthetics

• Nitrous Oxide: Bone marrow suppression and megaloblastic anemia
• Halogenated Anesthetics: Hepatotoxicity, cardiac arrhythmias, renal toxicity, and neurotoxicity

Major Indication for the Use of Intravenous Anesthetics

• Induction and maintenance of general anesthesia.

Major Clinical Characteristics of General Anesthesia

• Loss of consciousness
• Analgesia
• Muscle relaxation
• Amnesia

Disadvantage of Halothane

• It can cause hepatotoxicity

Advantage of Nitrous Oxide

• It is a weak general anesthetic that has analgesic and amnesic properties.

Major Indication for the Use of Barbiturates as Intravenous Anesthetics

• Induction of anesthesia The barbiturate drugs used include thiopentone sodium and methohexital/methohexitone.

Major Indication for the Use of Opioids as Intravenous Anesthetics

• Analgesia

Major Indication for the Use of Propofol as an Intravenous Anesthetic

• Induction and maintenance of anesthesia
• Sedation

Major Indication for the Use of Etomidate as an Intravenous Anesthetic

• Induction of anesthesia in patients with cardiovascular disease.

Advantage of Nitrous Oxide

• It is a weak general anesthetic that has analgesic and amnesic properties.
• It is also relatively safe and has a rapid onset and offset.

Disadvantage of Halothane

• It can cause hepatotoxicity
• It has a slow onset and offset.
• It can also cause cardiac arrhythmias.

Disadvantage of Enflurane

• It can cause seizures and malignant hyperthermia.

Major Indication for the Use of Benzodiazepines as Intravenous Anesthetics

• Sedation, amnesia, and anxiety relief before surgery.

Disadvantage of Isoflurane

• It can cause hypotension and tachycardia.
• It can trigger malignant hyperthermia.

Advantage of Thiopentone Sodium

• It has a rapid onset of action.
• It is a potent hypnotic agent.

Thiopentone Sodium

• It can cause respiratory depression.
• It has a short duration of action.

Advantage of Diethyl Ether

• It is a potent anesthetic.

Major Clinical Characteristic of General Anesthesia

• Loss of consciousness

Ketamine

• Ketamine is not a barbiturate. It is a dissociative anesthetic.
• It is used to induce and maintain anesthesia.
• It is not metabolized in the liver.

Thiopentone Sodium

• Thiopentone sodium is a barbiturate.

Methohexital/methohexitone

• Methohexital/methohexitone is a short-acting barbiturate. It is used for induction of anesthesia.

Benzodiazepines

• Benzodiazepines are a class of drugs that are used as sedatives, hypnotics, and anxiolytics.

Etomidate

• It has a very short duration of action. It is an effective induction agent.

Propofol

• It is a very potent and rapid-acting hypnotic agent.
• It is used for induction and maintenance of anesthesia.
• it can cause hypotension.

Opioid Agonists

• They produce analgesia and sedation.
• Opioid agonists can cause respiratory depression.

Ketamine

• Ketamine is a dissociative anesthetic that produces a unique state of anesthesia.
• It is used for induction of anesthesia.
• It is metabolized in the liver.

Intravenous Anesthetics

• They can cause a rapid onset of anesthesia.
• They are used for induction and maintenance of anesthesia.
• Some IV anesthetics are short-acting and have minimal side effects.

General Anesthesia

• It is a reversible loss of consciousness achieved by using anesthetic drugs that suppress neurotransmission in the brain.
• It is used to perform surgery and other medical procedures without pain and discomfort.

Nitrous Oxide

• It has analgesic and amnesic properties.
• It is a weak general anesthetic.
• It is metabolized in the liver.