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Questions and Answers
Which type of drugs are used for inducing controlled unconsciousness in general anaesthesia?
How do inhalational anaesthetics primarily act in the body?
Which inhalational anaesthetic has a fast recovery time and mild respiratory depressant effects?
What is a characteristic of desflurane that leads to increased costs?
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Which inhalational anaesthetic offers a wide range of clinical applications due to its mild hemodynamic effects?
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Among the inhalational anaesthetics, which one has the least pronounced cardiovascular response?
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What is the advantage of TIVA agents over inhaled anaesthetics?
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Which TIVA agent is preferred for rapid induction and maintenance of anaesthesia due to its impact on arterial pressure and heart rate?
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How does etomidate differ from propofol in terms of its impact on arterial pressure and heart rate?
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Why is remifentanil preferred in situations where haemodynamic stability is important?
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Which muscle relaxant is commonly used to facilitate intubation and ventilation during anesthesia?
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What is the primary mechanism through which opioids exert their effects during general anesthesia?
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Study Notes
Anaesthetic Agents for General Anaesthesia
General anaesthesia is a state of controlled unconsciousness induced by medications called anaesthetics. These agents work by suppressing neural activity throughout the body. There are several classes of drugs used for general anaesthesia, each with its own unique characteristics and uses. Here's a look into some common anaesthetic agents:
Inhalational Anaesthetics
Inhalational anaesthetics are volatile liquids that evaporate readily into gases when exposed to air. They act on lipid membranes, particularly at nerve terminals. Some commonly used inhalational anaesthetics include:
Desflurane
Desflurane has rapid induction and emergence times, a low blood gas solubility, and minimal effect on acid-base balance. It also has favourable resuscitation properties compared to other agents. However, its high potency requires small vapouriser sizes, which can lead to increased costs.
Isoflurane
Isoflurane is widely used due to its good safety profile and suitable stability. It has rapid induction and emergence times, a fast recovery time, and mild respiratory depressant effects.
Sevoflurane
Sevoflurane offers a wide range of clinical applications because of its mild hemodynamic effects and ocular effects. Its cardiovascular response is less pronounced than that of desflurane.
Total Intravenous Anaesthesia (TIVA) Agents
These agents are administered intravenously, often combined with opioids such as fentanyl, and sedatives like midazolam. TIVA agents have the advantage of providing consistent levels of depth of sedation without concerns related to the delivery system common to inhaled anaesthetics. Common agents include:
Propofol
Propofol provides rapid redistribution from the central compartment after discontinuation of infusion, resulting in a short duration of action. It causes dose-dependent decreases in arterial pressure and heart rate, making it useful for the rapid induction and maintenance of anaesthesia.
Etomidate
Etomidate is a non-barbiturate hypnotic agent characterised by a rapid onset of action, a moderate duration of action, and minimal reduction in mean arterial pressure and heart rate. It is used for rapid sequence inductions and tracheal intubations under general anaesthesia.
Opioids
Opioids are analgesics that are sometimes used for procedural pain management during general anaesthesia. They exert their effects via interaction with specific receptors found in the brain and spinal cord, especially the mu-opioid receptor. Some examples include:
Fentanyl
Fentanyl is a synthetic opioid that binds to the mu-, delta-, and kappa-opioid receptors. It has a rapid onset, intermediate analgesic efficacy, and short half-life.
Remifentanil
Remifentanil is self-administered by enzymatic degradation, which allows for rapid onset and offset of action. This property makes remifentanil preferable in situations where haemodynamic stability is important.
Sedatives and Muscle Relaxants
Sedatives and muscle relaxants are also used in conjunction with anaesthetics. Dexmedetomidine is a highly selective alpha-2 agonist commonly used to produce a sedative effect, while muscle relaxants such as rocuronium and vecuronium help facilitate intubation and ventilation.
Each anaesthetic agent has its own set of advantages and disadvantages, and the choice of agent depends on factors such as the patient's medical history, the type of surgery being performed, and the preferences of the surgical team.
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Description
Test your knowledge on common anaesthetic agents used for general anaesthesia, including inhalational anaesthetics, total intravenous anaesthesia (TIVA) agents, opioids, sedatives, and muscle relaxants. Learn about the characteristics, advantages, and disadvantages of each type of anaesthetic agent.
