Summary of TEMA 22. ANESTÉSICOS GENERALES

00:00:00 - 00:20:00

The video discusses general anesthetics, including their effects, risks, and mechanisms of action. Combinations of drugs are often used to achieve the desired effects with lower doses. The four stages of central nervous system depression caused by ether are discussed, but modern techniques have allowed for three phases of general anesthesia. The video also covers different types of anesthetics, including barbiturates, benzodiazepines, propofol, and ketamine, along with their benefits and possible side effects. The transcript also focuses on three specific general anesthetics, highlighting their benefits and potential risks. Overall, the proper administration and monitoring of general anesthetics are crucial to avoid complications.

• 00:00:00 In this section, we learn that general anesthetics can induce a reversible state of unconsciousness and insensitivity to pain. Other effects, such as amnesia, immobilization, and blocking of somatic and vegetative reflexes, are also sought after during anesthesia, but high doses of a single drug would increase the risk of toxicity. Therefore, combinations of drugs are used to achieve the desired effects with lower doses. Anesthetics have a narrow therapeutic index, meaning they must be carefully administered since they present different effects and adverse reactions depending on their properties, pharmacokinetics, physiopathology, and other drugs used. Different types of anesthetics have been used throughout history, but currently, intravenous agents are the most utilized to induce general anesthesia while inhaled agents are used for its maintenance. However, anesthetics present risks for the patient, such as hemodynamic, respiratory, digestive, and neurological effects, among others, that must be carefully monitored to avoid complications.
• 00:05:00 In this section, the video discusses the four stages of central nervous system depression caused by ether, from the start of anesthesia to paralysis and death, but notes that modern techniques and monitoring tools have allowed for three phases of general anesthesia: induction, maintenance (intravenous or inhalational), and waking. The mechanisms of general anesthetics are still not well understood, as they are mediated by various centers, structures, and neurotransmission systems, and their diverse chemical structures, but most anesthetics act through GABA and some through NMDA receptors. The video also covers the pharmacodynamics and pharmacokinetics of intravenous general anesthetics like thiopental, which interacts with GABA to produce central inhibitory effects, has weak analgesic action and respiratory depression at normal doses, and can lead to cardiovascular and respiratory side effects at higher doses, with slow elimination rates due to its accumulation in adipose tissue.
• 00:10:00 In this section, we learn about various general anesthetics including barbiturates, benzodiazepines, propofol, and ketamine. Barbiturates reduce cerebral metabolism, causing a significant drop in intracranial pressure that is beneficial for protecting against cerebral ischemia. Benzodiazepines such as the short-acting midazolam produce rapid and short-term sedative effects and are useful as anticonvulsants, anxiolytics, and muscle relaxants. Propofol also produces a rapid loss of consciousness, but recovery is faster, and it is considered safe for pregnant patients. Ketamine, a derivative of phencyclidine, induces dissociative anesthesia, causing profound analgesia and amnesia, while maintaining spontaneous respiration. It is important to note that while these drugs can cause side effects such as hypotension, respiratory depression, and hyper-sensitivity reactions, they are valuable tools in the practice of anesthesiology.
• 00:15:00 In this section, the video discusses general anesthetics, including ketamine, etomidate, and halothane. Ketamine increases blood flow to the brain and intraocular pressure, making it useful for patients at risk of hypotension during anesthesia. However, it can also lead to delirium characterized by hallucinations, vivid dreams, and illusions. Etomidate is a good hypnotic with a short duration of action, making it ideal for patients with cardiac disease, but can produce muscle contractions. Halothane is no longer widely used due to the availability of safer alternatives. Its main side effects are hypotension, respiratory depression, and liver toxicity.
• 00:20:00 In this section, the transcript discusses three different general anesthetics often used in surgery. Hyperthermia maligna is a potential risk associated with one of these medications. Another medication similar to loto produces hypotension with decreasing sympathetic activity, but not necessarily slowing of heart rate. It should be avoided in higher doses or hyperventilation which can cause muscle activity and seizures. Other effects presented by this medication often include nausea, vomiting, and altered liver function, as well as protecting the brain from injury and ischemia. Isoflurane on the other hand, is the most commonly used inhalable anesthetic worldwide as it rapidly induces anesthesia, but can cause a coronary steal by directing blood flow from poorly irrigated areas to those with more flow. Lastly, nitrous oxide is often used as a coadjuvant anesthetic due to its quick induction and recovery times, but little solubility in the blood. However, it requires particular administration requirements and can induce effect on the oxidation of cobalt.