General Anesthetics Flashcards
What is MAC?
Minimal alveolar concentration
Define MAC
50% of patients do not respond to a surgical stimulus (reach stage III anesthesia) - ED50
A _____ (higher / lower) MAC means the drug is more potent.
Lower
Which drug is the least potent of all the general anesthetics?
Nitrous oxide (105.0)
Which drug is the most potent of all the general anesthetics?
Methoxyflurane (0.16)
*****What is blood-gas partition coefficient?
ratio of drug gas dissolved in blood ( ionized) to free gas (nonionized)
*****If the blood-gas partition coefficient is higher then the onset is _____ (fast / slow). Why?
Slow because it indicates the drug is more ionized and dissolved in blood (water) and is unable to cross BBB.
*****Which inhaled general anesthetic onset is fastest (lower blood-gas partition coefficient number)?
Nitrous oxide (0.47)
*****Which inhaled general anesthetic onset is slowest (higher blood-gas partition coefficient number)?
Halothane (2.3)
*****What are the properties of a drug with a lower blood-gas partition coefficient (4 total)?
Less soluble in blood (nonionized higher), crosses BBB, arterial tension rises quickly, fast onset of action
*****What are the properties of a drug with a higher blood-gas partition coefficient (4 total)?
Highly soluble in blood (ionized higher), does not cross BBB, arterial tension rises slowly, slow onset of action
What are the two main side effects of nitrous oxide?
- Increased intracranial pressure (by increasing cerebral blood flow) 2. megaloblastic anemia (inhibitis vitamin B12 dependent enzyme methionine synthase because nitrous oxide oxidizes cobalt/metal)
Due to nitrous oxide’s side effect of increasing ICP, what conditions are contraindicated? What can you do in these conditions to help prevent this side effect?
Open head trauma, cerebral edema, and brain tumor; put patient on artificial respiratory support (intubated)
What kind of surgery is nitrous oxide most used in?
Dentistry
What are the three main side effects of halothane?
Decrease CO, liver dysfunction (very HY, can cause massive heptocyte death), and malignant hyperthermia
Which general anesthetics drugs can cause malignant hyperthermia?
Volatile anesthetic gases i.e. halothane, sevoflurane, desflurane, isoflurane, enflurane or the depolarizing muscle relaxants suxamethonium / succinylcholine* and decamethonium
All inhaled general anesthetics have the potential side effect of causing _____ and are therefore contradicted in open head trauma, cerebral edema, and / or brain tumor patients unless on artificial respiratory support (intubated)?
Increase ICP
Which IV anesthetic drugs can you use on in open head trauma, cerebral edema, and / or brain tumor patients because they reduce ICP?
Barbiturates Thiopental and Methohexital, Propofol (all other IV anesthetics increase ICP and cannot be used)
What IV general anesthetic drugs have a similar MOA as barbiturates?
Propofol and Etomidate
What is the structure and MOA of the dissociative anesthetic Ketamine?
Phencyclidine (PCP, dissociative anesthetic), NMDA receptor antagonist causing stimulation
What are the potential side effects of stimulation due to Ketamine?
HTN, tachycardia, ICP increase, and emergency phenomenon
Name the drug groups (6 total) and drugs within these groups that are intravenous general anesthetics.
- Barbiturates: thiopental, methohexital 2) dissociative: ketmaine 3) opiods: morphine, fentanyl 4) BZDs: midazolam, diazepam 5) Propofol 6) Etomidate
Name the drug groups (2 total) and drugs within these groups that are inhaled general anesthetics.
- Gaseous: NO / nitrOUS oxide 2) volatile liquids: Halothane and -fluranes
What is the “emergency phenomenon” that can be caused by Ketamine?
Hallucinations, disorientation, and nightmares a couple hours post-surgery