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Intravenous Anesthetics - Coggle Diagram

- - - - Most commonly used - midazolam
      - Diazepam & lorazepam (alternatives)
      - BZD - used in conjunction with anesthetics for sedation
    - - Besides sedation, they can also induce a temporary form of anterograde amnesia - patient retains memory of the past events, but new information is not transferred into long-term memory............ Therefore, important treatment information should be repeated to the patient after the effects of the drug have worn off
      - Only cause minimal CV depression (especially when administered intravenously)
      - By enhancing the inhibitory effects of GABA -> opens the chloride ion channels -> increases chloride ion entry -> hyperpolarization of neuron -> reduces neural excitability (sedative effect)
  - - - Because of their analgesic property, opioids are commonly combined with other anesthetics with weak analgesic property (nitrous oxide or volatile halogenated anesthetics)
      - Opioids -> analgesic effect
      - Choice of opioid primarily based on duration of action needed
      - Most commonly used = fentanyl & its congeners (sufentanil & remifentanil) -> they induce analgesia more rapidly than morphine
    - - They are not good anmesics
      - They may cause hypotension, respiratory depression & muscle rigidity as well as post-anesthetic nausea & vomiting
      - Opioids can be antagonized by naloxone
      - Route of administration: IV, epidural, intrathecal (into CSF)
  - - - Short duration of action (rapid recovery); rapid redistribution of thiopental to other body tissues (skeletal muscle & ultimately adipose tissue); re-distribution terminates action
      - Metabolism of thiopental is much slower than its tissue redistribution -> remain in body for relatively long period of time after administration
      - Onset: often <1 min (rapid induction)
    - - Cause apnea & cough
      - May also cause chest wall spasm, laryngospasm & bronchospasm (a particular concern for asthmatic patients)
      - Minor effects on patients with normal CVS, but it may contribute to severe hypotension in patients with hypovolemia or shock
    - - Commonly used barbiturates: thiopental, methohexital
      - Thiopental: ultrashort acting barbiturate with high lipid solubility; a potent anesthetic, but a weak analgesic -> require some supplementary analgesic during anesthesia
    - - Patients with acute intermittent porphyria
  - - - Causes a decrease in plasma cortisol & aldosterone levels which can persist for up to 8 hrs........... This is apparently due to inhibition of 11-B-hydroxylase
    - - Etomidate should not be infused for an extended time because prolonged suppression of these hormones can be hazardous
    - - Poor water solubility -> formulated in a propylene glycol solution
      - Rapid induction & short-acting
      - A hypnotic agent but lack analgesic activity
      - It is usually used in patients with coronary artery disease or CV dysfunction such as shock... why? because it exerts little to no effect on the heart & circulation
      - Etomidate - used for induction anesthesia
    - - Venous pain can occur on injection
      - Involuntary skeletal muscle movements are common
  - - - Fospropofol is a pro-drug of propofol (converted to propofol in the body)
      - Pharmacological effects- attributed by propofol
      - New, water-soluble drug approved for sedation
      - Loss of consciousness by fospropofol occurs within 4 mins (propofol = 30-40 secs)
    - - Fospropofol is water-soluble, therefore causes less problems which are associated with lipid-formulated propofol (eg: pain at IV injection site & increased chance for bacterial contamination) are less frequent
  - - - Ketamine is used in children & elderly adults, usually for short procedures but not widely used, because it increases cerebral blood flow & induces post-operative hallucinations (nightmares) particularly in adults
      - It stimulates central sympathetic outflow -> causes stimulation of heart with increased BP & CO........beneficial in patients with hypovolemic or cardiogenic shock & in asthmatic patients
    - - Hypertensive or stroke patients
    - - It induces a dissociated state in which patient is unconscious (but may appear to be awake) & does not feel pain
      - This "dissociative anesthesia" provides sedation and amnesia
      - A short-acting, non-barbiturate anesthetic
      - Ketamine is lipophilic & enters brain circulation very quickly (fast onset)
      - Similar to barbiturates, ketamine redistributes to other organs & tissues (recovery)
      - Also known as "pil kuda"
  - - - Occasionally causes muscle twitching, spontaneous movement & hiccups
      - A marked fall in BP
      - Depresses CNS (lesser extent compared to volatile inhalation anesthetics)
      - Reduces intracranial pressure (mainly due to systemic vasodilation)
    - - Minimal or low risk for post-anesthetic nausea & vomiting (anti-emetic effect)
      - It produces euphoric feeling
      - Rapid induction
    - - Redistribution (recovery) = 2-4 mins. This was then followed by a more prolonged period of hepatic metabolism & renal clearance
      - Pharmacokinetics of propofol are not altered by moderate hepatic or renal failure
      - Smooth induction within 30-40 seconds (rapid equilibration between plasma & brain)
    - - Propofol is in oil state at room temp & insoluble in aqueous solution but is highly lipid soluble
      - The viscous formulation causes pain on injection in 28%-90% of patients
      - Usually associated with pain at injection site
    - - Propofol - a weak analgesic -> usually co-administered with opioids
      - Commonly infused at lower doses to provide sedation for outpatient procedures
      - A common IV anesthetic used for induction or maintenance of anesthesia
      - It has replaced thiopental as the 1st choice for anesthesia induction & sedation
  - - - Provide sedation without causing respiratory depression
    - - Sedative
      - Analgesic
      - Sympatholytic
      - Anxiolytic
    - - Dexmedetomidime reduces volatile anesthetic, sedative & analgesic requirements of patient without causing significant respiratory depression
    - - An agonist at a2-receptors in certain parts of the brain
      - A sedative medication