Anesthesia

Question 1

Halothane

Answer 1

• 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

Question 2

Isoflurane

Answer 2

• Halogenated hydrocarbon inhalation
• Advantage: potent, <10 min induction, less hepatotoxic and renal toxic than halothane
• Disadvantage: smells bad, arrhythmias

Question 3

Desflurane

Answer 3

-Halogenated hydrocarbon inhalation

Question 4

Sevoflurane (7 fluorines)

Answer 4

• Halogenated hydrocarbon inhalation (newer one)
• High potency
• Fast onset of action (low blood solubility) and rapid recovery
• No metabolism
• Almost perfect inhalation anesthetic

Question 5

Nitrous oxide

Answer 5

• Low blood solubility (rapid onset)..2nd gas effect

- Disadvantage: MAC 104%, no muscle relaxing effect, diffusion hypoxia if rapidly discontinued

Question 6

Pentobarbital

Answer 6

-Injectable anesthetic

Question 7

Thiopental (Pentothal)

Answer 7

• 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

Question 8

Propofol

Answer 8

• 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

Question 9

Midazolam (Versed)

Answer 9

• 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!!!

Question 10

Ketamine

Answer 10

• 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..

Question 11

Fentanyl (Sublimaze) & Sulfentanyl (Sufenta)

Answer 11

• 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

Question 12

What are the 4 stages of anesthesia? (In general)

Answer 12

1. Analgesia and amnesia (ends w/loss of consciousness); Good
2. Delirium (begins with loss of consciousness, patients may become combative; get out of this as quickly as possible); Bad
3. Surgical anesthesia (Plane I-IV: I light surgical IV excessive surgical); good
4. Medullary depression (stage of reactive OD, patient can die); Bad OOPS

Question 13

How do you accomplish balanced anesthesia?

Answer 13

• General anesthetic - Loss of awareness or consciousness
• Benzodiazepine - Amnesia
• Opioid – Analgesia, blunting autonomic NS
• Neuromuscular blocker - Skeletal muscle relaxation

Question 14

What is the Partial pressure of oxygen needed?

Answer 14

21% (79% max can be anesthetic)

Question 15

What is the minimum alveolar concentration? (MAC)

Answer 15

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

Question 16

What is the difference between lipid solubility and blood solubility?

Answer 16

Lipid solubility: responsible for potency. Increased lipid solubility, increase potency. Also leaves slower.
Blood solubility: the more water soluble, the slower time of onset

Question 17

What is the second gas effect?

Answer 17

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