Drugs - General Anesthesia Flashcards
4 components of General Anesthesia
1 - Analgesia - pain relief
2 - Amnesia - no new memories formed
3 - Areflexia - not moving
4 - Unconsciousness - unaware
General Anesthesia
- Stages?
- Solubility in blood?
Stage 1 - Analgesia / pain relief
Stage 2 - Delirium ** LARYNGOSPASM RISK
Stage 3 - Surgical Anesthesia ** DESIRED STAGE
Stage 4 - Medullary Paralysis *** OVERDOSE
- The more soluble the GA agent is in the blood, the MORE YOU NEED to reach critical tension in the brain
- The LESS SOLUBLE in blood, the FASTER it goes on and off
3 steps of GA
1 - Induction
2 - Maintenance
3 - Emergence
Class of drugs used for Anxiolysis/Sedation
1 - Benzodiazepines
2 - Barbiturates
*** NOT analgesics, these provide NO pain relief
Benzodiazepines
- Mechanism of action?
- Examples (6)
- Binds to GABA receptors –> opens the channel –> increases Cl- (chloride ion) influx –> SLOWS down the CNS
- Diazepam (Valium)
- Triazolam (Halcion)
- Midazolam (Versed)
- Alprazolam (Xanax)
- Clonazepam (Klonopin)
- Lorazepam (Ativan)
Generic Name: Diazepam
Brand Name?
Valium
Generic Name: Triazolam
Brand Name?
Halcion
Generic Name: Midazolam
Brand Name?
Versed
Generic Name: Alprazolam
Brand Name?
Xanax
Generic Name: Clonazepam
Brand Name?
Klonopin
Generic Name: Lorazepam
Brand Name?
Ativan
Barbiturates
- Mechanism of action?
- Overdose may lead to what?
- Contraindication?
- Examples
- Same as Benzos - - Binds to GABA receptors –> opens the channel –> increases Cl- (chloride ion) influx –> SLOWS down the CNS
- Overdose may lead to Respiratory Depression
- Contraindicated in pts with Intermittent Porphyria, aggravates the disease
- Thiopental (quick onset, short duration of action - undesirable, used for induction)
Midazolam / Versed
- Class?
- Effects?
- When to give?
- Benzodiazepine
- Anxiolytic, Amnestic
- Induction period - First medication you give
Fentanyl
- Class?
- Effects?
- When to give?
- Opioid
- Decrease sympathetic drive - meaning, decrease HR, BP, stress on heart and body
- Reduces the amount of OTHER anesthetics needed to keep the patient under
- Induction Period
Lidocaine
- Class?
- Effects?
- When to give?
- Local anesthetic, Class 1B Anti-arrhythmic
- Reduces pain from Propofol IV injection
- Reduces post-op pain
- Reduces amount of anesthetics needed to keep patient under
- Reduces post-op ileus (painful obstruction of intestines)
- Induction Period
Propofol
- Class?
- Effects?
- When to give?
- General anesthetic
- Can be used as the sole anesthetic for MAC (Monitored Anesthesia Care / Twilight anesthesia)
- Vasodilation - so decreases BP (keep pressors on hand, not good for hemodynamically unstable patients), Anti-emetic
- Induction and Maintenance Periods
Pressors to keep on hand to combat the vasodilatory effects of Propofol:
When to use?
- Phenylephrine (vasopressor)
- Ephedrine (vasopressor and positive inotrope)
- Induction Period
Paralytics
- Succinylcholine - DEPOLARIZING
- Rocuronium - NON-DEPOLARIZING
Dexamethasone
- Uses?
- When to give?
- Anti-emetic
- Anti-inflammatory (steroid)
- Induction Period
Why is Halothane no longer used in the United States?
Hepatotoxicity - potential fatal liver toxicity
What is MAC (in terms of anesthetic gases) and what does it mean?
- Minimum Alveolar Concentration - alveolar concentration of a gas at 1 atm of steady-state concentration at which 50% of subjects do not respond to surgical incision/painful stimulus
- Aka = ED50 (effective dose for 50% of the population)
- MAC values are additive (0.5 MAC isoflurane + 0.5 MAC N2O = 1 MAC)
- MAC is INVERSELY related to anesthetic POTENCY
- High MAC –> Less potent
- 1 MAC of Nitrous Oxide = 104%
- ED95 is 1.3 MAC
What is the MAC of Nitrous Oxide?
N2O MAC = 104%
- Meaning, it can NEVER reach 1 MAC alone.
Between N2O, isoflurane, desflurane, sevoflurane - list most to least potent
MOST POTENT -- 1 - Isoflurane ----- MAC 1.2% 2 - Sevoflurane - MAC 2.0% 3 - Desflurane --- MAC 6.0% 4 - N2O ------------ MAC 104% -- LEAST POTENT
