Chapter 13 今日のメモ☆
神経系第四回目はAnesthetics[麻酔]に関する項です。
Kinds of Anesthetics
＊Ideal general anesthetics
induce anesthesia[感覚消失] rapidly and smoothly and permit rapid recovery of the patient once administration of the agent ceases.
- Volatile[揮発性] or inhalation anesthetics (gas or vapor[蒸気])
* Nitrous oxide(N2O)
* nonflammable[不燃性] halogenated hydrocarbon & ether ; e.g., halothane, methoxyflurane
- Nonvolatile or intravenous(i.v.), intramuscular(i.m.) anesthetics (aqueous solution)
* water-soluble(short acting) ; barbiturates, cyclohexylamine, benzo-diazepines, butyrophenone, opioid
* aqueous propylene glycol solution(compatible) ; imidazole, etomidate
* emulsion(not mixed with others) ; dialkylphenol, propofol
Pharmacology
- General anesthetics
depress the CNS ; reversible loss of consciousness & loss of sensation
- Inhalational anesthetics
absorbed and excreted through the lungs. these drugs are supplemented with below,
* Analgesics[鎮痛薬] : concentration of anesthetics↓
* Skeletal muscle relaxants : muscle relaxation during surgery
* Antimuscarinic agents : buccal & bronchiolar secretions↓
Therapeutic indications
- Inhalational anesthetics : general surgical anesthesia
- Nonvolatile anesthetics : induce dowsiness and procide relaxation before the inhalational anesthetics
※ use of previous popular volatile anesthetics was discontinued due to their toxicity, flammable[引火性] and explosive[爆発性] properties.
e.g., chloroform, cyclopropane, diethylether
Adverse effects
- depress respiration, circulation and the CNS
- hepatic & kidney function↓
- cardiac dysrhythmia[不整脈] (e.g., halothane)
Today's question
- Anesthetics(麻酔剤)の問題
Q: The brief duration of action of an ultra-short-acting barbiturate is the result of a
(A) slow rate of metabolism in the liver.
(B) low lipid solubility, resulting in a minimal
(C) high degree of binding to plasma proteins.
(D)
rapid rate of redistribution from the brain owing to its high liposolubility.
(E) slow rate of excretion by the kidneys.
A: (D)
Ultra-short-acting barbiturates are characterized by having branched or unsaturated 5,5-side chains and by having a sulfur atom in place of oxygen in the 2 position of the barbituric acid molecule. These modifications of barbituric acid result in an extremely liposoluble molecule that is very soluble in lipid tissues. After administration, an ultra-short-acting barbiturate readily crosses the blood-brain barrier but then is quickly redistributed into extracerebral tissue, resulting in a rapid loss of activity. While these agents do remain in the body for a long time and seem to have slow rates of metablism and excretion, their long retention time is due more to their slow rate of leaching out of lipid tissue.
