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Second Gas Effect
During induction of general anesthesia, when a large volume of a gas (e.g. nitrous oxide) is taken up from alveoli into pulmonary capillary blood, the concentration of gases remaining in the alveoli is increased. This results in effects known as the "concentration effect" and the second gas effect. These effects occur because of the contraction of alveolar volume associated with the uptake of the nitrous oxide. Previous explanations by Edmond I. Eger and Robert K. Stoelting have appealed to an extra-inspired tidal volume due to a potential negative intrapulmonary pressure associated with the uptake of the nitrous oxide. There are two extreme breathing patterns and the extra-inspired tidal volume is an artificial construct associated with one of these patterns. * * Errata British Journal of Anaesthesia 1997;79:268 Thus it is the volume change that actually causes the effects. An applicable example from Stedman's medical dictionary When a constant concentration of an anesthetic suc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
General Anesthesia
General anaesthesia (UK) or general anesthesia (US) is a medically induced loss of consciousness that renders the patient unarousable even with painful stimuli. This effect is achieved by administering either intravenous or inhalational general anaesthetic medications, which often act in combination with an analgesic and neuromuscular blocking agent. Spontaneous ventilation is often inadequate during the procedure and intervention is often necessary to protect the airway. General anaesthesia is generally performed in an operating theater to allow surgical procedures that would otherwise be intolerably painful for a patient, or in an intensive care unit or emergency department to facilitate endotracheal intubation and mechanical ventilation in critically ill patients. A variety of drugs may be administered, with the overall goal of achieving unconsciousness, amnesia, analgesia, loss of reflexes of the autonomic nervous system, and in some cases paralysis of skeletal muscles. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitrous Oxide
Nitrous oxide (dinitrogen oxide or dinitrogen monoxide), commonly known as laughing gas, nitrous, or nos, is a chemical compound, an oxide of nitrogen with the formula . At room temperature, it is a colourless non-flammable gas, and has a slightly sweet scent and taste. At elevated temperatures, nitrous oxide is a powerful oxidiser similar to molecular oxygen. Nitrous oxide has significant medical uses, especially in surgery and dentistry, for its anaesthetic and pain-reducing effects. Its colloquial name, "laughing gas", coined by Humphry Davy, is due to the euphoric effects upon inhaling it, a property that has led to its recreational use as a dissociative anaesthetic. It is on the World Health Organization's List of Essential Medicines. It is also used as an oxidiser in rocket propellants, and in motor racing to increase the power output of engines. Nitrous oxide's atmospheric concentration reached 333 parts per billion (ppb) in 2020, increasing at a rate of abo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pulmonary Alveolus
A pulmonary alveolus (plural: alveoli, from Latin ''alveolus'', "little cavity"), also known as an air sac or air space, is one of millions of hollow, distensible cup-shaped cavities in the lungs where oxygen is exchanged for carbon dioxide. Alveoli make up the functional tissue of the mammalian lungs known as the lung parenchyma, which takes up 90 percent of the total lung volume. Alveoli are first located in the respiratory bronchioles that mark the beginning of the respiratory zone. They are located sparsely in these bronchioles, line the walls of the alveolar ducts, and are more numerous in the blind-ended alveolar sacs. The acini are the basic units of respiration, with gas exchange taking place in all the alveoli present. The alveolar membrane is the gas exchange surface, surrounded by a network of capillaries. Across the membrane oxygen is diffused into the capillaries and carbon dioxide released from the capillaries into the alveoli to be breathed out. Alveoli are pa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Concentration Effect
In the study of inhaled anesthetics, the concentration effect is the increase in the rate that the Fa (alveolar concentration)/Fi (inspired concentration) ratio rises as the alveolar concentration of that gas is increased. In simple terms, the higher the concentration of gas administered, the faster the alveolar concentration of that gas approaches the inspired concentration. In modern practice it is only relevant for nitrous oxide since other inhaled anesthetics are delivered at much lower concentrations due to their higher potency. See also * Second gas effect During induction of general anesthesia, when a large volume of a gas (e.g. nitrous oxide) is taken up from alveoli into pulmonary capillary blood, the concentration of gases remaining in the alveoli is increased. This results in effects known as th ... References * * {{Anesthesia Anesthesia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tidal Volume
Tidal volume (symbol VT or TV) is the volume of air moved into or out of the lungs during a normal breath. In a healthy, young human adult, tidal volume is approximately 500 ml per inspiration or 7 ml/kg of body mass. Mechanical ventilation Tidal volume plays a significant role during mechanical ventilation to ensure adequate ventilation without causing trauma to the lungs. Tidal volume is measured in milliliters and ventilation volumes are estimated based on a patient's ideal body mass. Measurement of tidal volume can be affected (usually overestimated) by leaks in the breathing circuit or the introduction of additional gas, for example during the introduction of nebulized drugs. Ventilator-induced lung injury such as Acute lung injury (ALI) /Acute Respiratory Distress Syndrome (ARDS) can be caused by ventilation with very large tidal volumes in normal lungs, as well as ventilation with moderate or small volumes in previously injured lungs, and research shows that t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Halothane
Halothane, sold under the brand name Fluothane among others, is a general anaesthetic. It can be used to induce or maintain anaesthesia. One of its benefits is that it does not increase the production of saliva, which can be particularly useful in those who are difficult to intubate. It is given by inhalation. Side effects include an irregular heartbeat, respiratory depression, and hepatotoxicity. Like all volatile anesthetics, it should not be used in people with a personal or family history of malignant hyperthermia. It appears to be safe in porphyria. It is unclear whether use during pregnancy is harmful to the baby, and it is not generally recommended for use during a C-section. Halothane is a chiral molecule that is used as a racemic mixture. Halothane was discovered in 1955. It was approved for medical use in the United States in 1958. It is on the World Health Organization's List of Essential Medicines. Its use in developed countries has been mostly replaced by newer ane ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Concentration Effect
In the study of inhaled anesthetics, the concentration effect is the increase in the rate that the Fa (alveolar concentration)/Fi (inspired concentration) ratio rises as the alveolar concentration of that gas is increased. In simple terms, the higher the concentration of gas administered, the faster the alveolar concentration of that gas approaches the inspired concentration. In modern practice it is only relevant for nitrous oxide since other inhaled anesthetics are delivered at much lower concentrations due to their higher potency. See also * Second gas effect During induction of general anesthesia, when a large volume of a gas (e.g. nitrous oxide) is taken up from alveoli into pulmonary capillary blood, the concentration of gases remaining in the alveoli is increased. This results in effects known as th ... References * * {{Anesthesia Anesthesia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fink Effect
The Fink effect, also known as "diffusion anoxia", "diffusion hypoxia", or the "second gas effect", is a factor that influences the pO2 (partial pressure of oxygen) within the pulmonary alveoli. When water-soluble gases such as anesthetic agent N2O (nitrous oxide) are breathed in large quantities they can be dissolved in body fluids rapidly. This leads to a temporary increase in both the concentrations and partial pressures of oxygen and carbon dioxide in the alveoli. The effect is named for Bernard Raymond Fink (1914–2000), whose 1955 paper first explained it. When a patient is recovering from N2O anaesthesia, large quantities of this gas cross from the blood into the alveoli (down its concentration gradient) and so for a short period of time, the O2 and CO2 in the alveoli are diluted by this gas. A sufficiently large decrease in the partial pressure of oxygen leads to hypoxia, especially if the patient hypoventilates (which allows more time for evolving nitrous to dilu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inhalational Anesthetic
An inhalational anesthetic is a chemical compound possessing general anesthetic properties that can be delivered via inhalation. They are administered through a face mask, laryngeal mask airway or tracheal tube connected to an anaesthetic vaporiser, anesthetic vaporiser and an anesthetic machine, anesthetic delivery system. Agents of significant contemporary clinical interest include Volatility (chemistry), volatile anesthetic agents such as isoflurane, sevoflurane and desflurane, as well as certain anesthetic gases such as nitrous oxide and xenon. List of inhalational anaesthetic agents Currently-used agents * Desflurane * Isoflurane * Nitrous oxide * Sevoflurane * Xenon Previously-used agents Although some of these are still used in clinical practice and in research, the following anaesthetic agents are primarily of historical interest in Developed country, developed countries: * Acetylene * Chloroethane, Chloroethane (ethyl chloride) * Chloroform * Cryofluorane * Cyclopropa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
