Inhalational Agents Flashcards
1
Q
What is added on modern anesthetic agents?
A
diethyl group
2
Q
the 3 A’s of inhalational general anesthesia
A
amnesia, analgesia, areflexia
3
Q
Action of general anesthesia agents
A
altered transmission in the cerebral cortex
additional effects on: brain stem arousal center, central thalamus, spinal cord
4
Q
What makes them cross blood brain barrier quickly?
A
carbon based
5
Q
Stage 1 of Anesthesia
A
Amnesia and Anesthesia
initiation of anesthesia: LOC, follow simple commands, protective reflexes, eyelid reflex intact
6
Q
Stage 2 of Anesthesia
A
Delirium and Excitation
LOC and eyelid reflex, irregular breathing, dilated pupils, extremely hypersensitive - vomiting, laryngospasm, cardiac arrest, emergence delirium, avoid manipulating!
7
Q
Stage 3 of Anesthesia
A
Surgical Anesthesia - where we want them!
cessation of spontaneous respiration, absence of eyelash response and swallowing reflex
should get benefit of 3 A’s here
8
Q
Who do we see stage 2 exaggerated in?
A
young kids
9
Q
Stage 4 of Anesthesia
A
anesthetic overdose!
cardiovascular collapse
10
Q
Are we hyperdynamic or hypodynamic in stage 2?
A
hyperdynamic (elevated BP and HR)
11
Q
choice of anesthesia based on
A
proposed surgery
comorbidities
provider experience
surgeon
12
Q
When was nitrous oxide discovered and by who?
A
1793 by Joseph Priestley
13
Q
When was nitrous oxide successfully used in a dental procedure and by who?
A
1842 by Horace Wells
14
Q
when was diethyl ether first used in medicine and by who?
A
1842 by Crawford Long
15
Q
What day is ether day and why is it that day?
A
October 16.. on this day in 1846 William TG Morton removed a tumor from a jaw using diethyl ether
16
Q
When was chloroform discovered and by who?
A
1831 by Dr. Samuel Guthrie
17
Q
When was chloroform first used as an anesthetic and by who?
A
1847 by Sir James Young Simpson
18
Q
What is unique about chloroform?
A
nonflammable, highly potent
19
Q
When did Dr. John Snow use chloroform?
A
in 1853 on Queen Victoria during child birth
but had developed the first vaporizer
20
Q
When was Halothane developed?
A
1956
21
Q
Significance of Halothane?
A
first halogenated anesthetic agent, non flammable, metabolized in liver, causes hepatoxicity
22
Q
How does an inhalation agent work?
A
it starts in liquid form, gets vaporized, and breathed in and delivered to the brain
23
Q
absorption of inhalational agents are related to
A
ventilation, blood uptake, cardiac output, blood solubility, and alveolar to blood partial pressure difference
24
Q
the concentration or partial pressure of gas in the lungs is assumed to be ____
A
be equal in the brain
25
Definition of MAC
minimum alveolar concentration (%) required to produce anesthesia (lack of movement) in 50% of population
26
the faster the lung concentration rises
the faster anesthesia is achieved
27
Increase MAC if
hyperthermia, increase in CNS activity, hypernatremia, chronic alcohol abuse
28
Decrease MAC if
hypothermia, increased age, alpha 2 agonists (dex), acute alcohol ingestion, pregnancy, hyponatremia
29
rubber and plastic pieces and CO2 absorbent can ___
retain gas delaying initial uptake
30
all inhalational agents except ____ can trigger ___
nitrous oxide ; malignant hyperthermia
31
ways to avoid triggering malignant hyperthermia in at risk patient
flush 10mL/min for 20 minutes, replace all breathing circuits and CO2 absorbent, remove all vaporizers, charcoal filters
32
increasing liter flow during induction ____ agent intake
accelerates
33
Definition of Blood:Gas Solubility
describes amount of gas that will dissolve or bind to blood vs the amount that will diffuse into tissues
34
isoflurane solubility coefficient
1.4
there is 1.4x more gas soluble in the blood than available to the tissues
35
desflurane solubility coefficient
0.42
only .42 stays in blood for every molecule that is available to the tissues (put to sleep quicker and awake faster)
36
Which is more potent isoflurane or desflurane?
isoflurane
37
Over-pressuring or Concentration Effect
administration of higher concentration of gas than necessary to speed up initial uptake
greater effect on high solubility gases
38
Second gas effect
co-administering a 2nd agent with NO to speed the onset of the slower agent
also used in emergence to quickly remove slower gas
39
Why don't we use nitrous oxide with Desflurane often?
can cause tachycardia/arrhythmia if over-pressurized, toxic to environment
40
oil:gas solubility
ability to get into tissues, indicator of potency
41
higher lipid soluble drugs tend to be ___
more potent
42
the circulatory system has 2 major influences on anesthetic gases
1. uptake
| 2. distribution
43
an increase in cardiac output
slows uptake
44
approximately 5-8% of sevoflurane is metabolized
by the liver
45
decreases in temperature results in
increased potency and solubility
46
hypothermia decreases
tissue perfusion = slowed induction
47
how can decreased tissue perfusion in hypothermia be overcome?
increase gas concentration, warm the patient if able
48
hypothermia increases
tissue anesthetic capacity (slow recovery)
49
hyperthermia increases
cardiac output and anesthetic requirement (slows induction)
50
a patient receiving nitrous oxide during a case should receive
100% oxygen on emergence
51
the longer an anesthetic gas is used during the case
the slower the emergence
52
the higher the solubility
the slower the emergence
53
emergence phase 1
cessation of anesthetic, reversal, apnea to breathing, increased alpha and beta waves on EEG
54
emergence phase 2
increased HR and BP, return of autonomic responses, responsiveness to pain, salivation, tearing, grimacing, swallowing and gagging, defensive posturing
55
emergence phase 3
eye opening, response to verbal commands, awake EEG, extubation possible
56
nitrous oxide is ___ soluble than nitrogen
34 times more
57
when nitrous oxide is being administered what can happen
increased volume in air containing cavities (abdominal distension)
58
anesthetic agents are ___ soluble and ___ uptake in kids over adults
less; greater
59
right to left shunt
ex. PE
| shunted blood mixes and dilutes blood reducing anesthetic partial pressure and slows induction
60
left to right shunt
ex. septal defect
| increases uptake
61
What are all of the modern inhalation agents based off of?
ether
62
What is the basic structure of ether?
R-O-R
63
What is fresh gas flow determined by?
vaporizer and flowmeter settings
64
Fi stands for and is determined by
inspired gas concentration, determined by FGF rate, breathing circuit volume, and circuit absorption
65
FA stand for and is determined by
alveolar gas concentration, uptake, ventilation, concentration effect and second gas effect
66
Fa stand for and is determined by
arterial gas concentration, affected by ventilation/perfusion mismatching
67
What could cause V/Q mismatch in terms of intubation
right bronchial intubation, PFO
68
What do inhalational agents most likely target?
NMDA receptors, tandem pore potassium channels, VGNaCh, glycine receptors, GABA receptors
69
According to the Meyer Overton theory...
lipophilicity equals potency
70
CMRO2 is ____ with inhalational agents
decreased
71
Cerebral blood flow is ___ with inhalational agents
increased
72
What happens with "uncoupling"
CMRO2 decreased, CBF increased except for NO it increases both
73
cerebral vascular responsiveness to CO2 is
vasodilate
74
When does Burst suppression occur with inhalational agents?
1.5 MAC of desflurane, 2 MAC with isoflurane and sevoflurane
75
In terms of evoked potentials, inhalational agents
decrease amplitude (height) and increase latency (how often response is occuring)
76
What is the proposed mechanism of developmental neurotoxicity?
activation of extrinsic and intrinsic apoptic cell death pathways
77
What does PANDA stand for in PANDA study
pediatric anesthesia neuorodevelopment analysis
78
What does GAS stand for in the GAS trial
general anesthesia vs spinal
79
Who should we be concerned about postoperative cognitive dysfunction with?
the elderly
80
who should we be concerned with emergence delirium with?
children
81
what inhalational agents is more common with emergence delirium?
sevoflurane and desflurane (insoluble, get in quick, get out quick)
82
all volatile inhalational agents ___ CO
reduce
83
as MAC hours increase, ____ CI and HR
slight increase
84
reduced MAP secondary to
SVR reduction
85
how do inhalational agents induce HR changes?
via SA node antagonism, modulation of baroreflex activity, SNS activity (blunting)
86
all inhalational agents produce
vasodilation (SVR)
87
in hypotensive patients vasodilation can result in
reverse Robinhood syndrome (steal from poor give to the rich)
88
which inhalational agent is most associated with reverse robinhood syndrome?
isoflurane
89
preconditioning
the heart is exposed to intracellular events that protect it from ischemic and reperfusion insult
90
sensitization
volatile agents reduce the quanity (desensitize) of catecholamines necessary to evoke arrhythmias
91
safe epi dosing
10mL of 1:100,000 (10mcg/mL) in a 10 minute period or up to 30 mL in one hour
92
nitrous oxide causes a slight increase in
PVR , worsens with patients with pulmonary HTN
93
volatile agents decrease
pulmonary artery pressure
94
hypoxic pulmonary vasoconstriction is
depressed
95
which drug has the greatest effect on HPV?
isoflurane
96
volatile agents cause decreases in
tidal volume and responsiveness to CO2
97
how is decreased tidal volume compensated for?
increased RR (not sufficient to offset TV)
98
which causes the least bronchodilation?
desflurane
99
which has least impact of renal function?
desflurane
100
use of older absorbents can increase likelihood
nephrotoxicity with sevoflurane
101
should not exceed 2 MAC hours at flows ___
<2L per minute
102
Halothane has what affect on hepatic function?
is associated with Halothane Hepatitis
103
what causes halothane hepatitis?
metabolites binding to proteins and forming antibodies, re-exposure to Halothane antibodies mediate massive hepatic necrosis
104
Advantage of fluorination
resists hepatic degradation
105
which drug undergoes the most metabolism?
sevoflurane (5-8%)
106
is sevoflurane toxic to liver?
no, can be toxic to kidneys though d/t fluoride ions
107
volatile agents have additive effect with
nondepolarizing NMBDs
108
an ideal anesthetic agent
```
nonirritating to respiratory tract
rapid induction and emergence
chemically stable (nonflammable)
produce amnesia, analgesia, areflexia
potent
not metabolized and excreted by respiratory tract
free of toxicity and allergic reactions
minimal systemic changes
uses a standardized vaporizer
affordable
```
109
what four properties affect how agents work
vapor pressure, boiling point, partial pressure, solubility
110
what is vapor pressure
pressure exerted inside a container between liquid and vapor
111
as long as liquid is present, vapor pressure is
independent of volume
112
vapor pressure is directly proportional to
temperature
113
boiling point
temperature at which vapor pressure exceeds atmospheric pressure in an open container
114
partial pressure
fraction of pressure within a mixture (Dalton's Law)
115
solubility
tendency of a gas to equilibrate with a solution (Henry's Law)
116
the concentration of anesthetic in tissue is dependent on
the partial pressure and solubility
117
what is used instead of partial pressure
inspired concentration or fractional volumes
118
for most drugs, concentration is measured as
mass (mg/mL) but can be expressed in percent by weight or volume
119
MAC awake
MAC in which 50% opens eyes to command
120
MAC bar
the MAC necessary to block adrenergic response to stimulation
121
MAC ___ with age
decreases
122
How much should MAC decline with age?
6% each decade after age 40
| 6% of 6% for example
123
how do vaporizers facilitate movement of anesthetic from machine to patient
by fresh gas flow, pressure, and temperature
124
isoflurane (general facts)
```
halogenated methyl ethyl ether
most potent, most soluble
slow onset and recovery
dilates coronary arteries - reverse robinhood
minimal cardiac depression
pungent, not used for induction
```
125
desflurane (general facts)
least potent
quicker induction and emergence
heated and pressurized to maintain constant
can boil at room temp
rapid increase in gas can increase HR and BP
very pungent
avoid in pts with reactive airway disease
bad for the environment
126
sevoflurane (general facts)
```
fluorinated methyl isopropyl ether
moderate potency
rapid induction and emergence
may prolong QT interval
nonpungent
preferred agent for induction
small percent metabolized by CYP
soda lime can degrade into Compound A (nephrotoxic)
```
127
safety factors for sevoflurane
calcium hydroxide absorbent, flows 2lpm, avoid in renal dysfunction
128
nitrous oxide (general facts)
```
not volatile, colorless and odorless
gas at room temp
nonflammable
NMDA receptor antagonist
have to weigh it
stimulates SNS, increases RR, decreases hypoxic drive
increases CMRO2 and CBF
increases risk of PONV
```
129
absolute and relative contraindications for NO
absolute: methionine synthase pathway deficiency, expansion of gas filled space
relative: PONV, 1st trimester pregnancy, increased ICP, pulmonary HTN, prolonged surgery
130
Xenon (general facts)
noble gas, odorless, colorless, naturally occuring, acts on NMDA and glycine receptors, minimal effects
rare and hard to get
ideal agent
131
malignant hyperthemia triggered by
succinylcholine and volatile anesthetics
| stress
132
malignant hyperthermia receptor
ryanodine receptor gene mutation (chromosome 19)
133
S/S of malignant hyperthemia
incease in CO2 production, muscle rigidity, metabolic acidosis, high temp, urine color darkens, tachycardia, tachypnea
134
treatment of malignant hyperthermia
dantrolene sodium or ryanodex**
135
dose of dantrolene sodium (w/ mannitol and sodium hydroxide)
1 mg/kg
*70mL vials containing 20mg
administer until side effects subside or up to 10mg/kg
takes forever to mix!!
136
ryanodex
requires fewer vials and less reconstituion, shorter half life, requires supplementation of mannitol
