GENERAL ANESTHETICS| Pharmacology| CNS| #osmosis #Mednex| 1st video

Summary

This video provides a comprehensive overview of general anesthetics, including their mechanisms of action, types, and specific examples. It explains how anesthetics work by affecting neurotransmitters like glutamate and GABA, with a focus on both parental (injected) and inhalational (inhaled) anesthetics. The video covers the onset, duration, side effects, and contraindications of common anesthetics such as thiopental, propofol, ketamine, nitrous oxide, and halogenated agents. A creative mnemonic is introduced to help memorize the key pharmacology concepts, making this information more accessible and engaging for students and professionals alike.

Takeaways

• 😀 General anesthetics induce an anesthetic state in patients undergoing surgery, which includes unconsciousness, sedation, analgesia, and amnesia.
• 😀 General anesthetics work by depressing the central nervous system, either by blocking excitatory NMDA receptors or enhancing inhibitory GABA receptors.
• 😀 There are two main phases in anesthesia: induction (entering the anesthetic state) and maintenance (sustaining the state during surgery).
• 😀 General anesthetics are classified into two categories: parenteral (injected) and inhalational anesthetics.
• 😀 Parenteral anesthetics, such as thiopental, propofol, and ketamine, are often used for induction and some for maintenance in short procedures.
• 😀 Inhalational anesthetics, like nitrous oxide and halogenated agents (e.g., halothane, isoflurane), are administered through the lungs and have a small therapeutic window.
• 😀 Ketamine is unique among parenteral anesthetics because it works by blocking NMDA receptors, increases blood pressure, and induces dissociative anesthesia.
• 😀 Side effects of parenteral anesthetics include cardiovascular depression, hypotension, respiratory depression, and amnesia.
• 😀 Inhalational anesthetics can cause cardiovascular and respiratory depression, increased intracranial pressure, and malignant hyperthermia in susceptible individuals.
• 😀 The mnemonic uses imagery like a river and a field of flowers to help remember specific drugs and their side effects, such as cardiovascular depression and respiratory issues.

Q & A

What are the main conditions that general anesthetics aim to induce in patients?

General anesthetics aim to induce unconsciousness, sedation, analgesia (pain relief), and amnesia to make surgery tolerable and manageable for both the patient and the surgeon.

How do general anesthetics affect the central nervous system?

General anesthetics depress the central nervous system by reducing the amount of action potentials firing in the brain. They either block excitatory synapses or enhance inhibitory synapses to induce anesthesia.

What role does glutamate play in anesthesia?

Glutamate is an excitatory neurotransmitter that binds to NMDA receptors on post-synaptic neurons to stimulate action potentials. Some general anesthetics work by blocking these NMDA receptors to prevent excitation in the brain.

What is the difference between general and local anesthetics?

General anesthetics induce unconsciousness and affect the entire body, while local anesthetics block pain in a specific part of the body without affecting consciousness.

What are the two main phases of anesthesia, and what do they involve?

The two main phases of anesthesia are induction, which is when the patient enters the anesthetic state, and maintenance, which involves keeping the patient in the anesthetic state for as long as needed during surgery.

What are the two classes of general anesthetics, and how are they administered?

The two classes of general anesthetics are parental (administered via injection into a vein) and inhalational (administered through a mask or tracheal tube). Parental anesthetics are used for induction, while inhalational anesthetics are typically used for maintenance.

What is the main mechanism of action for parental anesthetics like propofol and thiopental?

Parental anesthetics like propofol and thiopental mainly work by stimulating GABA receptors or increasing their sensitivity, leading to inhibition of the central nervous system.

What are the advantages and disadvantages of ketamine as an anesthetic?

Ketamine has a rapid onset and a longer duration than other parental anesthetics. It stimulates the sympathetic nervous system, making it suitable for patients at risk of hypotension and for asthmatics. However, it can cause hallucinations and delusions upon recovery.

What is the second gas effect, and which anesthetic is associated with it?

The second gas effect refers to the phenomenon where nitrous oxide, when combined with other anesthetics, lowers the therapeutic dose required for the other agents. This effect helps enhance the potency of other anesthetics.

What is malignant hyperthermia, and which anesthetics are associated with it?

Malignant hyperthermia is a life-threatening condition where anesthetic agents cause excessive calcium release in muscle cells, leading to muscle rigidity, metabolic acidosis, and tachycardia. This condition is associated with halogenated anesthetics.