Anesthesia/anesthetics inhalational

Balanced Anesthesia with Inhalational Anesthetic Agents... 

During maintenance of anesthesia with inhaled anesthetics, the drug continues to be transferred between various tissues at rates dependent on the solubility of the agent, the concentration gradient between the blood and the tissue, and the... 

Protein Theories. The direct interaction of inhalation anesthetics and proteins has been proposed as the cause of anesthesia. An inhalation agent, whether a noble gas or a fluorinated ether, could dissolve asymmetrically in a protein, Resultant conformational changes in the protein, if these changes occur, could then cause changes in biological activity. 

Alternative survival methods include anesthesia by inhalation (isoflurane) or injectable (tribromoethanol) anesthetics which can be used to temporarily immobilize the mice (60, 61). While isoflurane is commonly used for repeated anesthesias, tribromoethanol is contraindicated for repeated use (60). Another approach for partial immobilization of mice is to use a 50-50% O2/CO2 mixture in a sealed container (see Note 3). Another alternative is to place the mice in a restraint device in which there is a black concave area for... 

Ingestion is the most common form of accidental and intentional exposure. This occurs primarily via drinking bromonated water. In the past, inhalation was a more common route of exposure during anesthesia. However, due to the associated toxicities, bromoform is no longer popular as an anesthetic. Inhalation can still be a significant route of exposure via volatilization of household or workplace water. Dermal absorption is possible but not likely to be a significant route of exposure in intact skin. 

Indications Induction or maintenance of anesthesia Category Anesthetic, inhalation Half-life Onset of action 1-2 minutes Clinically important, potentially hazardous interactions with tramadol... 

Trade names Alyrane Efrane Ethrane (Baxter) Etrane Indications Maintenance of general anesthesia Category Anesthetic, inhalation Half-life N/A... 

Indications Anesthesia Category Anesthetic, inhalation Half-life N/A... 

Anesthesia. Materials that have unquestionable anesthetic properties are chloral hydrate [302-17-0] paraldehyde, dimethoxymethane [109-87-5] and acetaldehyde diethyl acetal. In iadustrial exposures, however, any action as an anesthesia is overshadowed by effects as a primary irritant, which prevent voluntary inhalation of any significant quantities. The small quantities which can be tolerated by inhalation are usually metabolized so rapidly that no anesthetic symptoms occur. 

The onset of action is fast (within 60 seconds) for the intravenous anesthetic agents and somewhat slower for inhalation and local anesthetics. The induction time for inhalation agents is a function of the equiUbrium estabUshed between the alveolar concentration relative to the inspired concentration of the gas. Onset of anesthesia can be enhanced by increasing the inspired concentration to approximately twice the desired alveolar concentration, then reducing the concentration once induction is achieved (3). The onset of local anesthetic action is influenced by the site, route, dosage (volume and concentration), and pH at the injection site. 

The membrane enzyme luciferase, responsible for light emission in fireflies, is sensitive to anesthetics (20,21), and the concentrations of inhalational agents which inhibit luciferase are the same as those which cause general anesthesia. Studies of various classes of inhalational agents and luciferase demonstrated that above a certain chain length in a homologous series, a point is reached where higher members are not anesthetic. The same cut-off effect in efficacy is observed in anesthesia (22). This effect is not explainable by Hpid theory. 

Isoflurane is a respiratory depressant (71). At concentrations which are associated with surgical levels of anesthesia, there is Htde or no depression of myocardial function. In experimental animals, isoflurane is the safest of the oral clinical agents (72). Cardiac output is maintained despite a decrease in stroke volume. This is usually because of an increase in heart rate. The decrease in blood pressure can be used to produce "deHberate hypotension" necessary for some intracranial procedures (73). This agent produces less sensitization of the human heart to epinephrine relative to the other inhaled anesthetics. Isoflurane potentiates the action of neuromuscular blockers and when used alone can produce sufficient muscle relaxation (74). Of all the inhaled agents currently in use, isoflurane is metabolized to the least extent (75). Unlike halothane, isoflurane does not appear to produce Hver injury and unlike methoxyflurane, isoflurane is not associated with renal toxicity. 

The total U.S. market value for the anesthetic agents Hsted was 299.9 million ia 1990 (162). General inhalation agents, valued at 154.5 million, comprised over half (51.5%) of the 1990 market. General iv anesthetics were valued at 111.5 million (37.2%). Local iajectable agents, at 33.9 million, represented the smallest portion of the market (11.3%). U.S. sales for selected anesthesia pharmaceuticals are given ia Table 6. 

The anesthesiologist selects the anesthetic drug that will produce safe anesthesia, analgesia (absence of pain), and in some surgeries, effective skeletal muscle relaxation. General anesthesia is most commonly achieved when the anesthetic vapors are inhaled or administered intravenously (IV). Volatile liquid anesthetics produce anesthesia when their vapors are inhaled. Volatile liquids are liquids that evaporate on exposure to air. Examples of volatile liquids include halothane, desflurane, and enflurane. Gas anesthetics are combined with oxygen and administered by inhalation. Examples of gas anesthetics are nitrous oxide and cyclopropane. 

Enflurane (Ethrane) is a volatile liquid anesthetic that is delivered by inhalation. Induction and recovery from anesthesia are rapid. Muscle relaxation for abdominal surgery is adequate, but greater relaxation may be necessary and may require the use of a skeletal muscle relaxant. Enflurane may produce mild stimulation of respiratory and bronchial secretions when used alone Hypotension may occur when anesthesia deepens. 

Halothane (Fluothane) is a volatile liquid given by inhalation for induction and maintenance of anesthesia Induction and recovery from anesthesia are rapid, and the depth of anesthesia can be rapidly altered. Halothane does not irritate the respiratory tract, and an increase in tracheobronchial secretions usually does not occur. Halothane produces moderate muscle relaxation, but skeletal muscle relaxants may be used in certain types of surgeries. This anesthetic may be given with a mixture of nitrous oxide and oxygen. 

In the past, trichloroethylene was used as a human anesthetic. Trichloroethylene has also been used by individuals who intentionally inhale it for its narcotic properties. Therefore, most of the information regarding the effects of trichloroethylene in humans comes from case studies and experiments describing effects of trichloroethylene after inhalation exposure. These studies indicate that the primary effect of exposure to trichloroethylene is on the central nervous system. Effects include headache, vertigo, fatigue, short-term memory loss, decreased word associations, central nervous system depression, and anesthesia. 

A 30-year-old female is being prepared for anesthesia before exploratory surgery for a mass in her neck. In addition to using an inhalation anesthetic, a drug is given that causes complete paralysis of the skeletal muscles. 

Chloroform is also known as trichloromethane or methyltrichloride. It is a colorless liquid with a pleasant, nonirritating odor and a slightly sweet taste. Most of the chloroform found in the environment comes from industry. It will only bum when it reaches very high temperatures. Chloroform was one of the first inhaled anesthetics to be used during surgery, but it is not used for anesthesia today. Nearly all the chloroform made in the United States today is used to make other chemicals, but some is sold or traded to other countries. We also import chloroform. 

Inhalational anesthetics are administered in and, for the most part, eliminated via respired air. They serve to maintain anesthesia Pertinent substances are considered on p. 218. 

Injectable anesthetics (p. 220) are frequently employed for induction. Intravenous injection and rapid onset of action are clearly more agreeable to the patient than is breathing a stupefying gas. The effect of most injectable anesthetics is limited to a few minutes. This allows brief procedures to be carried out or to prepare the patient for inhalational anesthesia (intubation). Administration of the volatile anesthetic must then be titrated in such a manner as to counterbalance the waning effect of the injectable agent. 

Increasing use is now being made of injectable, instead of inhalational, anesthetics during prolonged combined anesthesia (total intravenous anesthesia—TIVA). 

The object of inhalation anesthetics is to obtain a concentration (partial pressure) of the drug in the brain sufficient to reach the desired level of anesthesia. In order to do this, anesthetic molecules must pass through the lungs into the brain through various biological phases. Therefore, inhalation anesthetics must be soluble in blood and interstitial tissue. 

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