Inhaled Agents Flashcards

Question

Sevoflurane - brand name

Answer 1

Blue tank, nonpungent

Answer 2

* **Lower** partition coefficients imply **decreased** solubility, faster equilibration of partial pressure (alveolus ⇔ blood ⇔ brain), * ***_Rapid induction_*** * ***__***Ex: desflurane

Answer 3

* **Higher** partition coefficients imply **increased** solubility, slower equilibration as more molecules are dissolved in the blood * ***_Prolonged induction_*** * Ex: halothane

Answer 4

* Partition coefficients express relative solubility of anesthetic gas at equilibrium * **Tissue:Blood coefficient = time for equilibrium of tissue with _arterial_ blood**

Answer 5

* **Increased** CO results in **faster uptake** but **decreased** alveolar concentration (Fa) * ***_Prolonged induction_*** * More blood passing through the lungs = anesthetic is getting carried away **faster**

Answer 6

* Depends on uptake by desired (brain) and undesired (fat, muscle) tissues * Tissue uptake is determined by partition coefficients and regional blood flow * **Less tissue uptake** means blood returns to alveolus with **higher partial pressure** * **F_a increases faster**

Answer 7

* Use of agents with **low solubility** (low partition coefficients) * **Low CO** w/ minimal R→L shunting and preserved CBF * **Increased alvolar MV, increased conc. of agent, increased FGF rate** * Replaces anesthetic taken up by the bloodstream) * Ex: Pediatric patients * Faster induction due to increased alveolar ventilation, decreased FRC, increased % of blood flow to brain

Answer 8

* Longer duration of anesthetic is associated with longer time to recovery * Over longer time, more anesthetic is deposited in undesired tissues and must be "washed out" * Effect is more pronounced with increased solubility of agent

Answer 9

* High concentrations of relatively insoluble gases (N₂O) diffuse out of the blood and enter the alveolus, displacing and replacing alveolar concentration of O₂ and CO₂ * Dilution of alveolar O₂ can lead to hypoxia * Dilution of CO₂ can **decrease** ventilatory drive and worsen hypoxia * Administer high flow 100% O₂ for 5-10 minutes after discontinuation of N₂O

Answer 10

* Reference point (1 MAC) = alveolar conc. at which 50% of patients will not move in response to a standardized surgical stimulus * Analogous to ED₅₀ * MAC is greatest at 1 yr and is reduced by 6% per decade

Answer 11

* 1.5 - 2 MAC * Concentration which _b_locks **_a_**drenergic **r**esponse to nociceptive stimuli

Answer 12

* ≈ 0.4 - 0.5 MAC * Concentration at which 50% of patients will not be forming long term memory

Answer 13

* 0.15 - 0.5 MAC * Concentration at which 50% of patients open eyes on command

Answer 14

* Acidosis * Acute alcohol use * Advanced age * Benzodiazepines * Increased altitude * Intravenous anethestics * Hypotension (severe) * Hypoxia * Opiates * Pregnancy

Answer 15

* Chronic alcohol use * Very young age (closer to 1 y of age) * Increased temperature ( \>42°C) * Decreased altitude * Drugs (MAOIs, TCAs, cocaine, acute amphetamine use)

Answer 16

* All volatile agents are dose-dependent CV depressants, though mechanism of decreased BP differs * Heart rate effects vary with MAC and inspired concentration rate of change

Answer 17

* All agents increase RR with decrease in TV * Overall volatile agents cause decrease in MV and increase in PaCO2 * All agents blunt ventilatory response to hypoxemia, volatile agents decrease response to hypercarbia * Volatile agents are potent bronchodilators * Minimal inhibition of hypoxic pulmonary vasoconstriction (HPV)

Answer 18

* All agents **_increase**_ CBF causing _**increased_** ICP and impair autoregulation of vascular tone * Volatile agents **_decrease_** CMR (N2O may increase) * All agents **_decrease_** SSEP / MEP signals

Answer 19

* **_Halothane**_ causes _**both_** hepatic artery vasoconstriction and decreases portal vein flow * Potential for hypoxic hepatic injury * Other volatile agents preserve vascular supply better with **_increase**_ in hepatic artery flow _**compensating**_ for _**decreased_** portal vein flow

Answer 20

* All agents decrease RBF, GRF, UO * Untreated hypotension can cause acute kidney injury

Answer 21

* **HR:** ⇔ or slight decrease * **SVR:** ⇔ * **CO:** significantly decrease * **Contractility:** significant decrease * **HBF:** significant decrease

Answer 22

* **HR:** slight increase * **SVR:** slight decrease * **CO:** ⇔ * **Contractility:** slight decrease * **HBF:** slight decrease

Answer 23

* **HR:** ⇔ * **SVR:** slight decrease * **CO:** ⇔ * **Contractility:** slight decrease * **HBF:** slight decrease

Answer 24

* **HR:** slight increase * **SVR:** slight decrease * **CO:** ⇔ * **Contractility:** slight decrease * **HBF:** slight decrease

Answer 25

* **HR:** ⇔ or increase * **SVR:** ⇔ or increase * **CO:** ⇔ or increase * **Contractility:** ⇔ or decrease * **HBF:** slight decrease

Answer 26

* **_MAC of 104% precludes use as solo agent for surgical anesthesia_** * Used at 30 - 70% conc. as adjuvant to IV or potent inhaled anesthetics * *Low solubility = rapid onset / offset of action* * **Nonpungent, has _analgesic_ properties** * Disadvantages * Rapidly diffuses into and expands air-containing cavities → avoid in air embolism, PTX, bowel obstruction, pneumocephalus, middle ear and retinal procedures * Prolonged exposure → inhibits B₁₂-dependent enzymes for myelin and nucleic acid synesthes * Megaloblastic bone marrow change possible \> 12 - 24 h use * **Nonflammable but _does_ support combustion** * *Increases PONV* * *Sympathomimetic CV effects*

Answer 27

* Inexpensive, *slower onset / offset of action* * *Pungent* * **Coronary vasodilator** * Possibility for coronary "steal" effect → flow diverted away from vessels with fixed lesions

Answer 28

* **_Most rapid onset / offset among volatiles_** * Very pungent → may be irritant in patients prone to bronchospasm * *High vapor pressure requires an electrically heated vaporizer → eliminates variations in delivery owing to changes in ambient temp.* * **_Rapid increase or high conc. may cause transient but significant sympathetic stimulation_**

Answer 29

* Least pungent (best choice for inhalational induction) * Fast onset / offset of action * Controversial potential for nephrotoxicity due to metabolic production of fluoride ion and degradation to Compound A * Compound A production increases with low FGF, high conc. sevoflurane, desiccated barium lime absorbent

Answer 30

* Low pungency * Inexpensive * Esp. potent bronchodilator * **_Rare but fulminant postop autoimmune hepatitis_** * *CV depression and myocardial desensitization to catecholamines (increases vent. dysrhythmias)*

Answer 31

* Nonanesthetic gas mixture * Commonly 70 - 79% helium and 21 - 30% O₂ * **Lower density of gases promotes laminar flow, reduces turbulence in upper airway obstruction** * Helps decrease the work of SV