Lecture 6: Inhalation Agents Flashcards
What was the earliest anesthetic?
Ether
T/F: All inhalation agents have a low blood:gas solubility coefficient in common.
True.
This creates a favorable pharmacokinetic profile and promotes their clinical use today.
A chemical bond that involves the sharing of electron pairs between atoms is called a _______.
Covalent Bond.
The stable balance of attractive and repulsive forces between atoms when they share electrons is known as covalent bonding. For many molecules, the sharing of electrons allows each atom to attain the equivalent of a full outer shell, corresponding to a stable electron configuration.
Match the following Covalent Bonds with their names.
- Alkane a. C=C
- Alkene b. C-C
- Alkyne c. CEC (E= 3 lines, or 3 bonds)
- Alkane b. C-C
- Alkene a.C=C
- Alkyne c. CEC (E=3 lines, or 3 bonds)
simple way to remember. Ane, Ene, Yne follow alphabetical order. A=1 bond, E=2 bonds, Y=3 bonds.
Chemical Structure and Agent Characteristics:
All commonly used inhalations are ethers or aliphatic hydrocarbons with no more than ___ carbon atoms.
4 (no more than 4 carbon atoms)
Chemical Structure and Agent Characteristics:
Why is the length of the molecule significant?
Anesthetic effect of immobility is decreased or lost if carbon atom chain length exceeds a distance of 4-5 carbon atoms 5 angstroms.
Chemical Structure and Agent Characteristics:
What is meant by “Halogenated” hydrocarbons?
Halogens are substituted for Hydrogen atoms in the chemical structure.
Chemical Structure and Agent Characteristics:
What are the halogen gases are attached to the molecules? (hint: there are 4 of them)
F (Fluorine)
Cl (Chlorine)
Br (Bromine)
I (Iodine)
Chemical Structure and Agent Characteristics:
The addition of F, Cl, Br, or I provide what characteristics to an anesthetic gas? (hint: 4 items)
- Potency
- Arrhythmogenic properties
- Flammability
- Chemical stability
Halogenated gases:
How is potency impacted by halogenation?
Potency increases as the amu (atomic mass unit) of a halogen increases.
Bromine 80 amu vs. Fluorine 19 amu. Bromine will be more potent.
Potency of inhalation agent has been found to correlate with the physical property of lipid solubility. A decline in potency (increased MAC value) is not a perfect correlation.
Halogenated gases:
How is Arrhythmogenesis impacted by halogenation?
INCREASING the number of halogen atoms within a volatile agent FAVORS the occurrence of arrhythmia.
Halogenated gases:
How is Flammability and Chemical Stabilty impacted by halogenation?
Flammability is REDUCED and Chemical Stability is ENHANCED by substituting hydrogen atoms with halogens.
What are Aliphatic Hydrocarbons?
a compound containing carbon and hydrogen joined together in straight chains, branched trains or non-aromatic rings.
What are the halogens?
- Halogens are a group in the periodic table consisting of 5 chemically-related elements (F, Cl, Br, I and Astatine). Known as (vertical) group 17.
- It is the only group to contain elements in 3 states at standard temperature (gas F and Cl, liquid Br, and solid I).
- All are toxic.
- All of the halogens form acids when bonded to hydrogen.
All modern inhaled anesthetics are halogenated hydrocarbons except_______?
Nitrous Oxide
Metabolism:
Typically, increasing the number of _____atoms on an anesthetic molecule will ______ the rate biodegradation.
FLUORINE;
SLOW or DECREASE
Anesthetic gases mostly excreted by the _____ and to a small extent metabolized by the _____.
- Excreted by the lungs unchanged.
- metabolized by the liver.
Halothane= 45% metabolized by liver (halothane hepatitis; rarely used)
Sevofluorane=5-8% metabolized by liver
Isofluorane=0.2% metabolized by the liver
Desflurane=0.02% metabolized by liver
T/F: All anesthetic gases are non-ionized.
True.
- All are non-ionized (not charged, neutral molecular compounds), strong covalent bonding.
- All have low molecular weight.
The goal of inhalation anesthesia is to produce the anesthetic state by creating a specific concentration of anesthetic molecules in the CNS. This is done by establishing a ____ _____ of an agent in the lungs, which then _______s with the brain and spinal cord.
Partial Pressure
Equilibrates
-with partial pressure equilibrium, the gas redistributes and is exhaled.
The anesthetic gases ______ the effects of stress from surgical stimulus, and _______ the occurrences of arrhythmias.
Attenuate/decrease
increase.
Pharmacodynamics:
Lipid solubility is directly proportional to ______. (Meyer-Overton rule)
Potency.
The potency of an anesthetic increases as the liposolubility increases.
Pharmacodynamics:
T/F: Reversal of anesthetic can be achieved with the application of pressure.
True.
Pharmacodynamics:
The exact mechanism of action is not well understood, however it is understood that the spinal cord and brain stem are effected and the _____ receptors are play a role in anesthesia effects.
GABA
Define MAC
not monitored anesthesia care
Minimum Alveolar Concentration (at MAC value, 50% of people will NOT respond to surgical stimulation.)
