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The concentration of the anesthetic in blood includes the portion that is undissolved in plasma and the portion that is dissolved (bound to plasma proteins). The more soluble the inhaled anesthetic is in blood compared to in air, the more it binds to plasma proteins in the blood and the higher the blood–gas partition coefficient.
It is a potent anesthetic with a minimum alveolar concentration (MAC) of 0.74%. [14] Its blood/gas partition coefficient of 2.4 makes it an agent with moderate induction and recovery time. [15] It is not a good analgesic and its muscle relaxation effect is moderate. [16] Halothane is colour-coded red on anaesthetic vaporisers. [17]
A lower MAC value represents a more potent volatile anesthetic. Other uses of MAC include MAC-BAR (1.7–2.0 MAC), which is the concentration required to block autonomic reflexes to nociceptive stimuli, and MAC-awake (0.3–0.5 MAC), the concentration required to block voluntary reflexes and control perceptive awareness.
Generally, inhalational anesthetics that are minimally soluble reach equilibrium more quickly. Inhalational anesthetics that have a high fat:blood partition coefficient, however, reach equilibrium more slowly, due to the minimal vascularization of fat tissue, which serves as a large, slowly-filling reservoir for the drug. [3]
Sevoflurane, sold under the brand name Sevorane, among others, is a sweet-smelling, nonflammable, highly fluorinated methyl isopropyl ether used as an inhalational anaesthetic for induction and maintenance of general anesthesia. After desflurane, it is the volatile anesthetic with the fastest onset. [8]
An inhalational anesthetic is a chemical compound possessing general anesthetic properties that is delivered via inhalation. They are administered through a face mask, laryngeal mask airway or tracheal tube connected to an anesthetic vaporiser and an anesthetic delivery system .
The more lipophillic the anesthetic agent is, the more potent the anesthetic agent is. [3] [8] [18] This principle became known as the Meyer-Overton Correlation. It originally compared the anesthetic partition coefficient in olive oil (X-axis) to the effective dose that induced anesthesia in 50% (i.e., EC50) of the tadpole research subjects (Y ...
The Meyer-Overton correlation for anaesthetics. A nonspecific mechanism of general anaesthetic action was first proposed by Emil Harless and Ernst von Bibra in 1847. [9] They suggested that general anaesthetics may act by dissolving in the fatty fraction of brain cells and removing fatty constituents from them, thus changing activity of brain cells and inducing anaesthesia.