💊أدويه الجهاز العصبي المركزي 14
#Pharmcology_of_CNS 14
#CNS
#Anesthetics
INTRAVENOUS ANESTHETICS
حا نتكلم فيها عن👇
✔️Induction
✔️Recovery
✔️Effect of reduced cardiac output on IV anesthetics
✔️ Drugs
✔️Induction
🔘After entering the blood, a percentage of drug binds to plasma proteins, and the rest remains unbound or “free.”
🔘درجة الارتباط مع بروتينات البلازما بتعتمد على الخصائص الفيزيائية للدواء زي الdegree of ionization and lipid solubility
🔘The majority of CO flows to the brain, liver, and kidney (“vessel-rich organs”)
🔘The rate of this transfer is dependent on the arterial concentration of the unbound free drug, the lipid solubility of the drug, and the degree of ionization.
✔️Recovery
🔘Recovery from IV anesthetics is due to redistribution from sites in theCNS.
🔘This initial redistribution of drug into other tissues leads to the rapid recovery seen after a single IV dose of induction agent.
✔️Effect of reduced cardiac output on IV anesthetics
🔘When CO is reduced (for example, in shock, the elderly, cardiac disease), the body compensates by diverting more CO to the cerebral circulation
عشان كدا في الحالة دي لازم نقلل ال dose
🔘The slow titration of a reduced dose of an IV anesthetic is key to a safe induction in patients with reduced CO.
✔️ Drugs
✅Propofol
🌀Propofol is an IV sedative/hypnotic used for induction and/or maintenance of anesthesia.
🌀Because propofol is poorly water soluble, it is supplied as an emulsion containing soybean oil and egg phospholipid, giving it a milk-like appearance
🔵Onset
🔹Induction is smooth and occurs 30 to 40 seconds after administration
🔹Plasma levels decline rapidly as a result of redistribution, followed by a more prolonged period of hepatic metabolism and renal clearance.
🔹The initial redistribution half-life is 2 to 4 minutes
🔵Actions
🔹Although propofol depresses the CNS, it is occasionally accompanied by excitatory phenomena, such as muscle twitching, spontaneous movement, yawning, and hiccups
🔹Propofol decreases blood pressure without depressing the myocardium. It also reduces intracranial pressure, mainly due to systemic vasodilation.
🔹The incidence of postoperative nausea and vomiting is very low, as this agent has some antiemetic effects.
✅Barbiturates
🌀Thiopental is an ultra–short-acting barbiturate with high lipid solubility. It is a potent anesthetic but a weak analgesic.
🌀These drugs may remain in the body for relatively long periods, because only about 15% of a dose entering the circulation is metabolized by the liver per hour. Thus, metabolism of thiopental is much slower than its redistribution.
🌀These drugs may remain in the body for relatively long periods, because only about 15% of a dose entering the circulation is metabolized by the liver per hour. Thus, metabolism of thiopental is much slower than its redistribution.
✅Benzodiazepines
🌀The benzodiazepines are used in conjunction with anesthetics for sedation. The most commonly used is midazolam. Diazepam and lorazepam are alternatives.
🌀They are metabolized by the liver with variable elimination half-lives, and erythromycin may prolong their effects.
✅Opioids
🌀Because of their analgesic property, opioids are commonly combined with other anesthetics.
🌀The most commonly used opioids are fentanyl and its congeners, sufentanil and remifentanil, because they induce analgesia more rapidly than morphine
🌀Opioids are not good amnesics, and they can all cause hypotension, respiratory depression, and muscle rigidity, as well as postanesthetic nausea and vomiting.
🌀Opioid effects can be antagonized by naloxone
✅Etomidate
🌀Etomidate is a hypnotic agent used to induce anesthesia, but it lacks analgesic activity.
🌀Induction is rapid, and the drug is short-acting
🌀Etomidate is usually only used for patients with coronary artery disease or cardiovascular dysfunction
🌀Its adverse effects include decreased plasma cortisol and aldosterone levels,which can persist up to 8 hours.
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