Anesthesia Flashcards
Halothane
- Halogenated hydrocarbon inhalation
- CNS effect: increase intracranial pressure
- CV effects: Decreased myocardial contractility and stroke volume leading to lower arterial blood pressure; Sensitizes myocardium to catecholamines ↑ automaticity. Epi may trigger arrhythmia.
- Malignant hyperthermia may occur with ALL inhalation anesthetics except nitrous oxide, most commonly seen with halothane.
- Advantage: potent and cheap, no laryngospasm
Isoflurane
- Halogenated hydrocarbon inhalation
- Advantage: potent, <10 min induction, less hepatotoxic and renal toxic than halothane
- Disadvantage: smells bad, arrhythmias
Desflurane
-Halogenated hydrocarbon inhalation
Sevoflurane (7 fluorines)
- Halogenated hydrocarbon inhalation (newer one)
- High potency
- Fast onset of action (low blood solubility) and rapid recovery
- No metabolism
- Almost perfect inhalation anesthetic
Nitrous oxide
- Low blood solubility (rapid onset)..2nd gas effect
- Disadvantage: MAC 104%, no muscle relaxing effect, diffusion hypoxia if rapidly discontinued
Pentobarbital
-Injectable anesthetic
Thiopental (Pentothal)
- Injectable anesthetic
- Rapid onset and short action
- Facilitates GABA induced Cl- entry into neurons, leading to CNS depression
- Use caution: anesthetic dose is b/t 50-75% of LD50
Propofol
- Injectable anesthetic
- Rapid induction (50 s) and recover (4-8 minutes)
- May be given alone to maintain anesthesia or used for induction as part of balanced anesthesia technique
- Most significant respiratory effect is apnea!! Don’t walk out of room i.e Michael Jackson
- May result in injection site pain
- *DON’T USE FOR SLEEP, highest % of abuse is by anesthesiologists going to for a ‘cat nap’ 40% don’t wake up
Midazolam (Versed)
- Benzodiazepine
- Facilitates GABA induced Cl- entry into neurons by increasing the frequency of opening of Cl- channels, leading to CNS depression
- Most important for amnesia (anterograde)
- Insufficient for anesthesia!!!
Ketamine
- Injectable anesthetic
- Related to phencyclidine PCP
- Causes dissociative anesthetic (patient appears to be awake, but they are totally unaware)- good for surgery on the back so you don’t need to get them hooked up to breathing apparatus i.e. they breathe on their own.
- Principal drawback is the occurrence of emergence reactions (delirium and hallucinations)
- *Abuse potential due to PCP like effect. Known as Special K on the street.
- *Rapid action anti-depressant? Future..
Fentanyl (Sublimaze) & Sulfentanyl (Sufenta)
- Injectable anesthetic Opioid
- High dose: hemodynamic stability, respiration must be maintained artificially and may be depressed into the postoperative period
- Usually supplemented with inhalation anesthetic, benzodiazepine or propofal
What are the 4 stages of anesthesia? (In general)
- Analgesia and amnesia (ends w/loss of consciousness); Good
- Delirium (begins with loss of consciousness, patients may become combative; get out of this as quickly as possible); Bad
- Surgical anesthesia (Plane I-IV: I light surgical IV excessive surgical); good
- Medullary depression (stage of reactive OD, patient can die); Bad OOPS
How do you accomplish balanced anesthesia?
- General anesthetic - Loss of awareness or consciousness
- Benzodiazepine - Amnesia
- Opioid – Analgesia, blunting autonomic NS
- Neuromuscular blocker - Skeletal muscle relaxation
What is the Partial pressure of oxygen needed?
21% (79% max can be anesthetic)
What is the minimum alveolar concentration? (MAC)
Dose of anesthetic (vol%) producing surgical anesthesia in 50% of patient population (ED50).
- Lowest MAC drugs are the most potent example: sevoflurane (1.71% of the mixture). Nitrous oxide requires 104%..NOT EFFECTIVE for anesthetic. Only for analgesia.
- Need 1.3-1.5 MAC for light anesthesia, 2 MACs for deep anesthesia
What is the difference between lipid solubility and blood solubility?
Lipid solubility: responsible for potency. Increased lipid solubility, increase potency. Also leaves slower.
Blood solubility: the more water soluble, the slower time of onset
What is the second gas effect?
Rapid uptake of first anesthetic from alveoli into blood creates a negative pressure in alveoli
- Draws in more of a second inhaled anesthetic agent whose alveolar uptake might otherwise be slow
- Nitrous goes first, gets in fast, creates vacuum, sucks in halothane. Get out of 2nd stage quickly
- Diffusion hypoxia is a risk with nitrous during recovery
