Week 5: Inhalational Agents Flashcards
Until middle of the ______ century surgery was done without anesthesia
19th
1840’s - _________, ________, and ________ were the first accepted general anesthetics.
Nitrous oxide
Diethyl ether
Chloroform
October 16, 1846 - ___________ demonstrated Ether for anesthesia at Massachusetts General Hospital
William Morton
When did the specialty of anesthesia start?
1940’s
gaseous phase of a substance at a temperature which the substance can exist in either a liquid or a solid state below a critical temperature for that substance.
Vapor
Potent inhaled anesthetics are mostly in the _____ state at normal room temperature (20 C) and atmospheric pressure (760 mm Hg)
Liquid
** Desflurane kept in special bottle so it remains liquid.
Anesthesia vaporizers facilitate the change of a liquid into a vapor (T/F)
True
Heat of vaporization
is the number of calories required to change 1 gram of liquid into vapor without changing temperature
temperature at which vapor pressure equals atmospheric pressure (760 mmHg)
Boiling point
one in which the total gas flow is divided in two streams by a variable resistance proportioning valve. Usually a small percentage enters a vaporizing chamber, picking up molecules of volatile agent, while the majority travels through a bypass line.
Variable bypass vaporizer
*** Agent specific and concentration calibrated
READ ALL THIS IS REVIEW!!
Contains an electrical filament that heats the desflurane to 39 degrees C.
Raises the Saturated Vapor Pressure
The high pressure removes the need for a pressurized carrier gas
The fresh/diluted gas is separate from the vaporizing pressure
Desflurane is added directly to the fresh gas
The delivered concentration is adjusted by the vaporizer dial.
Tech 6 Vaporizer (Desflurane)
What would make an inhalational agent ideal?
- non-purgent
- non-flammable
- fast induction
- Fast-wake up
- No harmful metabolites
*** no perfect one exists.
General anesthesia is characterized by:
Altered state
Analgesia
Muscle relaxation
Amnesia
Reversible loss of consciousness.
Phases of General Anesthesia
Induction, maintenance, and emergence.
*All of these phases are affected by the pharmacodynamics and pharmacokinetics of the inhalational anesthetics
An Anesthetic state is obtained with a combination of 3 things:
Amnesia,
Analgesia, &
Lack of response to noxious stimuli
States the lipid solubility is directly proportional to the potency of an inhaled anesthetic.
The greater the solubility the lower the MAC value
Myer-Overton Theory
The greater the solubility the_____ the MAC value
lower
The depth of anesthesia is determined by the number of anesthetic molecules that are :
dissolved in the brain
All inhalational anesthetics work via a similar mechanism of action but not all the same sites
What theory?
Unitary Hypothesis
Inhaled anesthetics do what to these:
GABA/ Glycine
Glutamine
Calcium Channels
Potassium
Enhance inhibitory sites/receptors (GABA, Glycine).
Inhibits excitatory channels (Glutamine).
Inhibits calcium channels (Ca2+).
Inhibition of potassium (K+).
Immobility is mediated principally by effects of inhalationals on the
spinal cord
The ultimate effect of inhalational anesthetics depends on reaching a therapeutic level in the
CNS/Brain/Spinal Cord
Sites of Anesthetic Action for unconciousness
Reticular activating system - (Cortex, thalamus, brainstem).
Sites of Anesthetic Action for Analgesia
Spinothalamic tract
Sites of Anesthetic Action for Amnesia
Amygdala, hippocampus.
Sites of Anesthetic Action for immobility
ventral horn.
Ideal Characteristics of Inhaled Gases
Pleasant to inhale, smooth induction and emergence.
Rapid induction and emergence (low solubility).
Easy to administer and analyze, cheap.
Stable in carbon dioxide absorbers, inflammable, not metabolized.
Have a specific site of action.
No CV or respiratory side effects, nontoxic and provides pain control, muscle relaxation and no side effects.
Low solubility of inhaled anesthetics allows for:
Rapid induction and emergence
Anesthesia depth can be assessed by:
Lack of movement in non-paralyzed patient.
Respiratory rate and pattern.
Eye signs?
BP and Pulse values
BIS monitoring?
Effects of anesthetics are dose dependent. _____ & ____occur at lower levels while ________ occurs at much higher levels.
Amnesia & LOC;
Immobility
Conceptualized by Dr. Arthur Guedel during World War I
Guedel Chart
**originally divided into 4 stages.
Guedel Chart was First published in ______. and Depicted the signs and symptoms of ______ anesthesia.
1937;
Ether
Guedel’s Stages of Anesthesia
Stage I
induction to loss of consciousness
Guedel’s Stages of Anesthesia
Delirium with period of excitement, pupils dilated, disconjugate gaze, increased RR/HR, High risk of laryngospasm/bronchospasm
Stage II
Guedel’s Stages of Anesthesia
Surgical plane, fixed gaze, constricted pupils
Stage III
** desired maintenance stage.
Guedel’s Stages of Anesthesia
Overdose, absent or shallow/irregular RR, hypotension/profound CV collapse, dilated/unresponsive pupils
Stage IV
What is an Inhalational Induction?
who is it most common in?
Use of inhalational agents to induce a state of surgical anesthesia from a state of full consciousness
*Most common technique for inducing anesthesia in children undergoing elective surgery.
______ can help speed inhalational induction through the second gas effect.
Nitrous oxide.
*ask patient to take vital capacity breaths or tidal volume breathing.
Inhalational induction of anesthesia with patient breathing normal tidal volumes is _________ than IV and a __________ of a high concentration.
Slower;
gradual increase.
Inhalational induction with vital capacity breaths:
They are _________ than tidal volume breaths but not as __________ as IV inductions.
Quicker; quick
**prime bag with high concentration of gas.
A kid crying is more likely to go to sleep than a calm one with inhalation induction (T/F)
True-
Kid is doing vital capacity breaths.
Two main inhaled Agents for Inhalational Induction
Nitrous oxide (N2O) and Sevoflurane.
*** because it is less irritating, faster, and N2O will help speed it through second gas effects.
N2O and Sevoflurane are used in inhalational induction because they have low incidence of:
&
It is not recommended to use which agent?
-Breath holding
- Coughing
-Secretions
-Laryngospam
*Desflurane.
T/F - Volatile agents can relax airway smooth muscle and produce bronchodilation
True
** sevoflurane and N2O are good at this!!
Patients undergoing inhalational induction exhibit the stages of anesthesia (Especially ________ phase).
Excitement
Phase II
IV induction does not bypass the second phase of anesthesia (T/F)
False - it bypasses second phase.
Pt. pretty much right to sleep.
What are the advantages of inhalational induction?
- Less traumatic
- If no IV access (* specially kids).
- Short pediatric case.
- Bronchodilator effect.
Disadvantages of inhalational induction:
- Smell/irritant
- Excitatory stage (phase II).
- Delayed airway.
- Gas bypassing scavenger system.
MAC is defined as the inhalational anesthetic concentration/alveolar concentration at which 50% of the population will not :
MOVE to painful or noxious stimulus (e.g., surgical incision).
MAC values are sometimes expressed as anesthetic _________.
That is the lower the MAC value the more ______ the agent.
Potency.
Potent.
MAC varies _____ % to _______% among individuals
10 - 15%
MAC mirrors _______ partial pressure
Brain
Potency is directly related to ________. (_________ coefficient)
solubility;
Oil:gas
MAC values are ________: 0.5 MAC of N2O used with 0.5 MAC of Sevoflurane will give an effect of 1.0 MAC anesthetic
additive.
Desflurane has a ______ MAC = _______ potency = _______ solubility.
High MAC;
Low potency,
Low solubility.
Isoflurane has a ______ MAC = _______ potency = _______ solubility.
Low MAC value;
High potency;
High solubility.
MAC-BAR
Range:
MAC needed to Block Autonomic Response to painful stimuli.
or
“Blunt Adrenergic Response.”
Range: 1.5-2.0 MAC
2 MAC- awake:
Range:
alveolar concentration at which patient opens their eyes.
0.15 - 0.5 MAC
*** 0.4-0.5 to lose consciousness and 0.15 to regain it
Awareness MAC
Range:
Important for which patients?
Awareness and recall usually thought to be prevented.
0.4- 0.5 MAC
Trauma patients.
Movement MAC :
Range:
will prevent movement in 95% of surgical patients
1.2- 1.3 MAC
Nitrous Oxide MAC / VP
104 MAC
38,770 VP.
Isoflurane MAC/VP
1.17 MAC
244 VP
Sevoflurane MAC/VP
1.8 MAC
157 VP
Desflurane MAC/VP
6.6 MAC
669 VP
From most potent to least potent:
Des, Iso, Sevo, N2O.
Isoflurane> Sevoflurane> Desflurane> N2O
Factors that DO NOT alter MAC.
- Thyroid function (not directly.
- Anesthetic metabolism: since is <5%.
- Hyperkalemia.
- Hyper/Hypocabia
- Gender
- Duration of anesthesia.
- Metabolic alkalosis.
Factors that increase MAC:
-Hyperthermia
-Hypernatremia
-Drugs that increase CNS catecholamine levels (MAO inhibitors, cocaine, ephedrine, levodopa).
-Excess pheomelanin production (women with natural red hair)
-Chronic ethanol abuse
Factors that decrease MAC:
- Hypothermia
- Preoperative medications.
- Older age
- Pregnancy
- Alpha agonists
- Acute alcohol ingestion
- Hyponatremia
- Induced hypotension - - MAP<50mm Hg.
- Lots of drugs (Lidocaine, Lithium, Ketamine, opioids, benzos).
- Severe anemia
Older age decreases MAC by 6% per decade after age _____.
40
Hyporthermia decreases MAC by ______% per Celcius drop.
2-5%
Pregnancy decreases MAC by ____%
30
Inhaled anesthetics are slow acting, they slowly increase and decrease the anesthetic level.
(T/F)
False:
Rapid acting
Quickly increase and decrease the anesthetic level
Which is a true gas?
Nitrous oxide (N2O)
** that’s why it is on cylinder.
Which are the so-called “potent inhaled anesthetics” ?
They are the vapors of volatile liquids.
** but all are refer to as gases because thats how they are administered to patient.
All ________ with ______ molecular weights so they diffuse rapidly.
nonionized; low
Major advantage of inhaled anesthetics?
They can be delivered to the bloodstream via the lungs
Sevoflurane
Boiling point:
Blood:gas partition coefficient:
Oil:gas partition coefficient:
B.P= 59C
B:G = 0.65
O:G = 47
Desflurane:
Boiling point:
Blood:gas partition coefficient:
Oil:gas partition coefficient:
B.P= 24C
B:G = 0.42
O:G = 19
Isoflurane:
Boiling point:
Blood:gas partition coefficient:
Oil:gas partition coefficient:
B.P= 49C
B:G = 1.46
O:G = 91
Nitrous Oxide:
Boiling point:
Blood:gas partition coefficient:
Oil:gas partition coefficient:
B.P= - 88
B:G = 0.46
O:G = 1.4
At equilibrium, CNS partial pressure equals _____ partial pressure, which in turn equals ______ partial pressure.
blood;
alveolar
3 factors that result in equilibrium:
Inhaled are gases that quickly transfer BIDIRECTIONALLY via the lungs to and from the ________, then to and from the ________.
Plasma and tissues have a _____ capacity to absorb the anesthetic.
Metabolism, excretion, and redistribution are ________ relative to the rate they are delivered and removed from the _______.
Bloodstream ; CNS
Low
Minimal; Lungs.
What is the goal of inhalational anesthetics?
How is this goal achieved?
Establish a specific concentration of anesthetic molecules in the central nervous system
This is done by establishing the specific partial pressure of the agent in the lungs that equilibrates with the brain and spinal cord
Which factors increase the speed of onset of inhaled anesthetics? (4)
- High inspired concentration (dialing more).
- High alveolar minute ventilation : asking patient to take fast breaths.
- Low blood solubility
- High MAC
determined by flowmeter settings and vaporizer
fresh gas flow (FGF).
The fractional concentration of anesthetic leaving the circuit. Determined by FGF, breathing circuit volume and circuit absorption.
Fraction Inspired (FI) gas concentration.
The fractional concentration of anesthetic present in the alveoli. Determined by uptake, ventilation, the concentration effect and second gas effect.
Fraction Alveolar (FA): alveolar gas.
affected by ventilation perfusion mismatch
Fraction Arterial (Fa): arterial gas.
Goal is anesthetic state in the CNS/Brain.
This creates a gradient that leads to equilibrium between the _______ partial pressure of the anesthetic and the partial pressure of the anesthetic in _____.
alveolar (PA);
arterial blood (Pa)
** Anesthetic must travel from the anesthesia machine to the tissue (brain).
The Goal of Inhalational Anesthesia
P_ = P_ = P __
PA = Pa = Pbr
Inspired Gas Concentration (FI) Depends on
- Fresh gas flow and rate
- Breathing system volume
- Absorption of machine circuit.
Ways to speed the increase in Inspired Gas Concentration (FI)
- High fresh gas flow (>4L/min)
- Small breathing circuit
- Less absorption (by CO2 absorbant).
** also rebreathing bag can be collapsed prior to starting the FGF.
For inhaled anesthetics:
Organ of uptake is the ____. and Target’s: ______.
LUNGS;
Target’s: Brain and spinal cord
= [(λ) x (Q) x (PA-Pv)]/Barometric Pressure
Uptake
λ = Solubility
Q = Cardiac Output
PA-Pv = alveolar- venous partial pressure difference
Solubility in the blood: determines speed of _____.
onset
The more soluble the AA is in the blood the _________ the patient becomes anesthetized
slower
Insoluble agents are taken up much slower by the blood so ______ induction (equilibrium).
faster
Solubility of an anesthetic is expressed as ___________.
Partition Coefficients
Partition Coefficients: ratio of the concentration of the anesthetic in the _____ phase to the_______ phase when at equilibrium between the two phases.
blood; gas
All potent agents are highly lipid soluble (T/F)
True
High Blood: Gas Coefficient:
_____ induction/wakeup.
Slow
Technique to speed induction with High blood:partition coefficient agent
Overpressure technique.
Low Blood:gas coefficient = ______ induction/wakeup
Rapid
_______ of volatile agents correlates with the physical property of lipid solubility.
The more soluble= the more _______.
Potency;
potent.
The higher the MAC the _____ the B:G coefficient.
lower
Decrease in potency is associated with a decrease in the _______ partition coefficient.
oil:gas
____ MAC = _____ soluble = ______ potent.
High;
Less; Less
Increase in CO, increase in blood flow through the lungs, more rapid uptake, increasing the amount removed from:
alveolar concentration.
Increased CO = _______ for inhalational to reach an equilibrium between the alveoli and brain therefore ______ induction time
longer; prolonged.
Decreased CO or blood flow through the lungs = _______ anesthetic taken up by the blood, ________ rate of rise in the PA.
Less; increased
______ solubility agents are more affected, ______ soluble agents are rapid regardless of changes in CO.
High;
Low
Alveolar-to-Venous Partial Pressure Difference (A-vD)
reflects tissue uptake of inhaled anesthetics
Transfer of anesthetic from blood to tissue is determined by:
-Tissue solubility
-Tissue blood flow (perfusion)
-Arterial blood/tissue partial pressure difference
Vessel Rich
Percent Body Mass
Percent Cardiac Output
10%
75%
Muscle
Percent Body Mass
Percent Cardiac Output
50%
19%
Fat
Percent Body Mass
Percent Cardiac Output
20%
6%
Vessel Poor
Percent Body Mass
Percent Cardiac Output
20%
<1%
Order of tissue uptake:
Blood equilibrates with alveolar gas, then ________ group,, then ________ group, then _______.
VRG;
muscle,
fat.
Perfusion of VRG:
_______ ml/min per 100 g of tissue
55-500
Perfusion of muscle group:
____ ml/min per 100 g tissue
3
Perfusion of fat:
____ ml/min per 100 g
1
Inhalational are very lipid soluble.
Fat equilibrates ______ due to perfusion. Which has a greater affect on _______ than induction.
Slower;
Emergence
The _______ fraction is directly proportional to the partial pressure of the anesthetic in the brain (CNS).
alveolar
Common way to assess anesthetic uptake is to follow the:
Ratio of fractional concentration in the alveolar anesthetic to the inspired anesthetic over time (FA/FI).
The anesthetic concentration in the gas circuit will rise in accordance with :
First-order kinetics.
With systems that obey first-order kinetics, about 95% of the theoretical maximal value will be reached in about _____ constants.
3
- we can do things to alter the uptake/quicken the rise. - starting with higher Ffgo can increase the rate of rise of FI.
How can we increase the FI?
- Increase the fresh gas flow
- Increase the minute ventilation
- Decrease the Functional Residual Capacity (FRC)
How to decrease FRC?
Mask induction instructions (especially in pediatrics).
Exhale deeply before applying the mask.
Breathe deeply and quickly after applying the mask
Increased FA/FI= _______ onset.
Curve pushed ______.
Increase;
up.
Decrease FA/FI= _______ onset.
Curve pushed ______.
Slower;
Down
Factors that increase FA/FI
Increase Wash in:
Decrease Uptake:
- High FGF
- High minute ventilation rate.
- Low FRC.
- Low time constant.
- Low anatomic dead space.
- Low solubility
- Low CO
- Low Pa-Pv difference
Factors that decrease FA/FI
Decrease Wash in:
Increase Uptake:
- Low FGF
- Low minute vetilations (shallow breathing).
- High FRC
- High time constant
- High anatomic dead space.
- High solubility
- High CO
- High Pa-Pv difference.
Overpressurization during initial administration of inhaled anesthetics is like giving an:
IV bolus
Increasing the concentration of inhalational will speed the rate of equilibrium of the agent; ______ declines as the tissues become saturated.
uptake
Augmented gas flow
as gas is leaving the alveoli for the blood, new gas at the original FI is entering the lungs to replace that which was taken up by the blood.
Concentrating will increase Nitrous FA/FI faster than Desflurane? Why?
Nitrous achieves a faster rate of rise of FA/FI.
Even though Desflurane is less soluble in blood, just the volume of Nitrous compensates for the minimal difference in solubility
_________ Partial Pressure and the _________ Partial pressure are very close to equal in relation to Ventilation and Perfusion in healthy patients.
Alveolar;
Arterial
________ mismatch can affect the uptake and distribution of the inhaled anesthetics.
Ventilation/Perfusion
Impact of shunting (intracardiac and intrapulmonary right-to-left shunt) on FA/FI.
It decreases it. Dilutional effect.
Decrease in PA/PI.
**
Recovery from anesthesia:
Rate of decrease in the _____ as reflected by the PA
Pbrain
Concentration of Inhaled anesthetics in the tissues at the end of anesthetic depends on two things:
The solubility of the agent and time of administration.
Exhaled gases from the patient contain anesthetic that will be rebreathed unless fresh gas flow rates are : > _______ L/min
5
Factors Affecting Wake Up:
-Agent used/Solubility
-Ventilation
- Length of procedure
- Patient age, mental state, medical conditions, medications (opioids, benzos, intoxicants, neuroleptics).
- Obesity (*specially soluble ones).
- Sleep apnea and airway obstruction.
Some of the same things that affect induction will affect emergence (3):
minute ventilation, CO, & solubility of drug.
T/F: the loss of inhales anesthetics transcutaneously is insignificant.
True!!
**it does occur but very small.
Factors to the speed up recovery from inhaled anesthetics.
- increasing ventilation and FGF.
- Anesthetic circuit volume
- Increase in cerebral blood flow.
- Increased CO.
Which inhalational agents are non-pungent?
Sevoflurane, Halothane, and Nitrous are non-pungent.
Which inhalational agents are pungent?
Desflurane and Isoflurane
** .
All volatile anesthetics ______ tidal volume and _______ respiratory rate. (Dose dependant).
Decrease;
increase
Volatile can cause a gradual _______ in minute ventilation leading to _________ in PaCO2.
All inhaled anesthetics produce a dose-dependent ________ of the ventilatory response to hypercarbia.
Depression
Some inhaled anesthetics cause bronchodilation (T/F)
False…. not some, ALL of them cause bronchodilation.
Smokers have impaired mucociliary function, and the combination of a volatile anesthetic in a smoker who is mechanically ventilated sets up a scenario for inadequate clearing secretions, mucus plugging, atelectasis and hypoximia especially with which pungent agent?
Desflurane.
Inhalational agents _______ BP via relaxation of vascular smooth muscle causing _______ in SVR.
Reduce;
Decrease
Inhalationals __________ MAP, CO and CI in dose-dependent ways.
Reduce
**except N2O
Nitrous oxide _________ sympathetic nervous system and vascular resistance (SVR). When combined with a volatile anesthetic the SVR and BP are _______ than if volatile anesthetic was given alone.
increases ;
Greater
*** can also lead to increase in CVP and arterial pressures.
If sevoflurane is dropping your patient’s blood pressure what can you do?
Turn on N2O, and turn sevo down a little.
Rapid increases in inhaled concentration of________ and especially_______ can increase HR and BP due to the sympathetic stimulation
Isoflurane; Desflurane
**Desflurane especially has an irritant effect.
**opioids can help decrease stimulation.
Sevoflurane has minimal effect on HR. (T/F)
True
Circulatory effects of inhaled anesthetics.
- Myocardial depression
- Initial tachycardia with Desflurane>Isoflurane with MAC greater than 1, ISO> Des under 1 MAC.
- Vasodilation (decreased SVR) leading to hypotension.
- Coronary dilators.
** cardiac output is well preserved, minimal effect.
_________ (and most other potent volatile anesthetics) increases coronary blood flow beyond that of the myocardial oxygen demand, thereby creating potential for “____________.”
Isoflurane ; coronary steal
** this remains questionable.
Diversion of blood from a myocardial bed with limited or inadequate perfusion to a bed with more perfusion
Coronary Steal
all of the potent agents _________ cerebral blood flow by direct vasodilation of the cerebral blood vessels
Increase
**dose dependent.
with inhaled anesthetics there is an increase in ICP secondary to increased blood flow that can be attenuated by __________.
hyperventilation
Inhalational agents decrease the cerebral metabolic rate of _______.
oxygen
Dose dependent effects on the EEG, SEPs and MEPs
All volatiles cause dose-dependent increase in ________ and decrease ___________in all cortical SEPs.
Latency; Amplitude
Inhalationals produce dose-dependent _______ in uterine smooth muscle contractility and blood flow.
Modest at____MAC and substantial at _____ MAC
decreases;
0.5; >1
Nitrous can decrease the need for volatile anesthetics for OB cases. T/F
True.
Uterine relaxation from volatiles can cause increased _______ due to uterine atony
blood loss
Renal factors affected by inhaled anesthetics.
- decreases in renal vascular resistance.
- decrease in glomerular filtration rate.
- past concerns with sevoflurane degradation with the older carbon dioxide absorbents and production of compound A.
- Autoregulation remains intact.
Different than IV anesthetics, inhalational agents Undergo minimal liver metabolism because they are primarily excreted via the _______.
Lungs
The chemical structure of inhaled agents determines extent of liver metabolism.
minimally - most commonly biodegraded by way of hepatic metabolism through:
cytochrome P-450 oxidation
Inhaled anesthetics have two important actions on the neuromuscular function:
- All inhalationals produce dose-dependent skeletal muscle relaxation
- They have an additive effect/ potentiates NMBAs.
Inhalationals can delay recovery from nondepolarizing muscle relaxants (T/F)
How do inhalationals potentiate NMBAs?
- Reduced neural activity within in CNS.
- Prominent postsynaptic effect at the neuromuscular junction.
Other things to think about inhalationals.
Developmental _______ and the developing brain.
Postoperative ________ and the elderly.
Emergence______ in children
Neurotoxicity;
Cognitive dysfunction;
Delirium
Postoperative Cognitive Dysfunction is a major concern among; (2)
and it is ____- term.
Pediatric and elderly patients
Short-term.
**It is hypothesized that elderly may be at more significant risk for long-term cognitive problems
Acute state of confusion/agitation after anesthesia.
Emergence Delirium
Emergence Delirium
Prevalence of 20%-80%, primarily seen in:
pediatrics
Peak incidence of emergence delirium in children of both sexes at _______ years of age
2-6
Emergence Delirium more common after (2).
Sevoflurane and Desflurane
** as compared to Isoflurane and TIVA
Usually lasts 10-15 minutes and is terminated spontaneously or after an IV dose of propofol, midazolam, clonidine, dexmedetomidine, ketamine, opioids, or other medications.
Emergence delirium
Degradation of Sevoflurane by strong bases (soda lime) in the CO2 absorbers produces
Compound A
** new ones have no NaOH or KOH……now contain Calcium or lithium hydroxides.
Higher probability of compound A in ____ flow rates, ______ circuit breathing systems, and _____ CO2 absorbents
low,
closed,
warm/dry
Greater than 2 MAC hours of Sevo and fresh gas flows less than 2L/ min may cause Induced Nephrotoxicity which is associated with _______ & ________.
proteinuria and glucosuria
Very low probability of toxicity with CO2 absorbers happening today due to better absorbents examples:
Dragersorb, Amsorb, LoFloSorb
CO is a degradation product of volatile agents(especially _________) due to dry/desiccated CO2 absorbents
Desflurane
Ideal CO2absorbents
Lack of reactivity with anesthetics
Lack of toxicity
Low resistance to gas flow
Low cost efficiency in absorption
The exhaled gases pass through a canister containing a CO2absorbent such as soda lime. Soda lime consists of calcium hydroxide (Ca[OH]2) with lesser quantities of sodium hydroxide (NaOH) and potassium hydroxide (KOH). Soda lime reacts with CO2to form:
heat, water, and the corresponding carbonate.
Soda lime is the most common absorber and, at most, can absorb ____ L of CO2per 100 g of absorbent. However, the average absorber eliminates ___L of CO2per 100 g absorbent in a single-chamber system and _____ of CO2in a dual-chamber system.
23L;
10-15L;
18 to 20 L
Soda lime can also degrade sevoflurane. One of the metabolic by-products is a _______ known asCompound A.
vinyl ether
Compound A may accumulate during (4)
- longer cases,
- low-flow anesthesia,
- dry absorbent
- high sevoflurane concentrations.
Choice of volatile anesthetic also determines the amount of CO produced, and at equiMAC concentrations .
______ > ______ > _______.
desflurane > enflurane > isoflurane.
Commonly used volatile anesthetics are_________that vaporize when exposed to atmosphere.
halogenated ethers
The pressure exerted by a vapor in equilibrium with its liquid or solid phase inside of a closed container.
Vapor Pressure
Vapor pressure is directly proportional to temperature (t/f)
T
Boiling point
Vapor pressure equals atmospheric pressure.
Heat required to change liquid into a vapor .
Latent heat of vaporization.
The three categories of inhaled anesthetics
Alkanes (R-H)
Gases
Ethers (R-O-R)
Inhaled anesthetics in the ether group:
Desflurane
Isoflurane
Sevoflurane
Inhaled anesthetics in the alkane group:
Halothane
Chloroform
Inhaled anesthetics in the Gases group
Nitrous oxide.
Cyclopropane,
Isoflurane has ______ atoms and ______ atom.
5 fluorine; 1 chlorine
Desflurane has_____ atoms
6 fluorine
Sevoflurane had ______ atoms
7 fluorine
(sevo=seven)
All have chiral carbons except?
Sevoflurane has no chiral carbons
Desflurane and Isoflurane has chiral carbons
Isoflurane (________)
Forane
Isoflurane (Forane)
______ _______ ________ ether.
Halogenated methyl ethyl
Isoflurane (Forane) can possibly cause ______ d/t coronary vasodilation.
coronary steal
Isoflurane (Forane)
Solubility:
Blood:Gas coefficient:
Vapor pressure:
MAC:
Potency:
Pungency:
Soluble ;
1.46 - B:G
238 - VP.
1.2 - MAC
Most potent.
Pungent.
Isoflurane (Forane):
Dose-dependant
_______ in MAP
_______ in SVR
_______ cerebral blood flow.
Decreases MAP
decreases SVR
increases CBF
Most potent inhaled anesthetic:
Isoflurane
Most pungent inhaled anesthetic:
Desflurane.
**followed by Isoflurane.
It is okay to run isoflurane at low flows as it is resistant to:
degradation.
Sevoflurane (_______)
Ultane
Sevoflurane (Ultane) is a
____ _______ _____ ether
Fluorinated methyl isopropyl
Sevoflurane(Ultane)
Solubility:
Blood:Gas coefficient:
Vapor pressure:
MAC:
Potency:
Pungency:
Less soluble than ISO, but more soluble that Des.
0.65 - B:G
157 - VP
1.8 - MAC
ISO > SEVO > DES
Non- pungent. Smells sweet too.
Risks of using Sevoflurane.
- Carbon monoxide
- Compound A
- Fire with dry absorbent
Sevoflurane indications :
- Good fo inhalational induction ( with mask/ sweet ordor).
- Bronchospasm: great bronchodilator.
Sevoflurane increases sympathetic activation (T/F)
False!! - it has MINIMAL sympathetic activation
You shouldn’t run sevoflurane for a long time at _______.
Low FGF! - Compound A risk
Desflurane (_______)
Suprane
Desflurane (Suprane) is
______ _____ ______ ether.
Fluorinated methyl ethyl
Desflurane (Suprane)
Solubility:
Blood:Gas coefficient:
Vapor pressure:
MAC:
Potency:
Pungency:
Not soluble in blood.
(Faster to sleep/ wake up).
0.42 B:G
669 VP
6.6 MAC
Least potent.
Most pungent.
Desflurane (Suprane)
has the Potential for _________ with dry CO2 absorbers
Carbon Monoxide
Desflurane (Suprane) effects on heart?
SNS stimulation (Increased HR and BP)
Desflurane (Suprane) is pungent. it can be a potential airway irritant over _____ MAC.
1
Dual-circuit (carrier gas not split) NOT a variable-bypass vaporizer .
TEC 6- Vaporizer.
TEC 6 vaporizer can be filled while in use (T/F)
T
TEC 6. vaporizer is Electrically heated to a constant _____ degrees C
39
**Heat produces vapor which is injected into fresh gas flow
All volatile anesthetic agents increase the incidence of postoperative nausea and vomiting (PONV) and the risk increases with __________. They should be avoided in patients at high risk of PONV.
the duration of exposure to the anesthetic
What can be an alternative anesthetic plan for patient with high risk of PONV?
TIVA
Nitrous Oxide is the only _________ gas in clinical use, also called ________ gas.
inorganic;
laughing
Colorless, non-pungent, non-explosive, non-flammable.
Nitrous Oxide
Nitrous Oxide cannot be used in combination with O2 and inhalationals (T/F)
FALSE!!!
** It is used in combination with these; as an adjunt
Nitrous Oxide
Solubility:
Blood:Gas coefficient:
Vapor pressure:
MAC:
Pungency:
Low solubility
0.46 B:G
38,770 VP
104
Non-pungent.
Nitrous oxide effects:
_________ CV effects.
_________ BP
_________ RR
_________ TV
Minimal;
increases BP
increases RR
decreases TV
NOT a triggering agent for Malignant Hyperthermia
Nitrous oxide
Nitrous oxide may cause PONV (T/F)
TRUE
Nitrous oxide provides muscle relaxation or uterine relaxation (T/F).
FALSE
It does not produce significant muscle relaxation.
The most clinical relevant concern is the ability of N2O to ________ because of its greater solubility in blood compared to nitrogen.
expand air-filled spaces
Nitrous is ______ more soluble than N2, both are _______ (increase in volume and pressure with the closed space).
34; insoluble
Nitrous is ______ more soluble than N2, both are _______ (increase in volume and pressure with the closed space).
34; insoluble
Nitrous oxide should be avoid in which procedures:
- Pneumothorax/ blebs.
- Bowel cases.
- Some eye surgeries
- Middle ear surgery
- Venous air emboli.
- Brain cases: Craniotomy.
Air-filled cuffs of pulmonary artery catheters and endotracheal tubes also expand with _______, possibly causing tissue damage,
N2O
** CAREFUL IN LONG CASES. CHECK CUFF.
N2O is a good _____.
Analgesic
N2O causes inactivation of __________ synthase, a key enzyme in _________ metabolism .
methionine; folate.
Long term use of N2O can cause __________ changes in bone marrow; less than ____ hours is considered harmless.
megaloblastic;
6
In compliant airspace - N2O increase ________.
examples:
Volume
fast:
-pulmonary blebs
- air bubbles in the blood
- sulfa hexafluoride bubble in the eye.
Slow:
- bowel
- pneumoperitoneum
in noncompliant (fixed) air spaces - N2O will increase _____,
Examples:
pressure
- middle ear
- brain during intracranial procedures.
Shutting off the _________ (rather than shutting off the vaporizer) during intubation or airway instrumentation is the best approach to prevent operating room pollution with anesthetic gases and reduce wastage.
fresh gas flows
Diffusion Hypoxia
Occurs when nitrous is discontinued abruptly, reversing the partial pressure gradients, therefore nitrous leaves the blood and enters the alveoli
in diffusion hypoxia: Initial outpouring of Nitrous ______ the PAO2, decreasing the PaO2.
There is also a dilution of the PACO2 which can _____ the stimulus to breath.
dilutes;
decrease
This effect is greatest during the first 5 minutes after stopping Nitrous.
Diffusion Hypoxia
**It is suggested that Nitrous be discontinued early in order to fill the lungs with oxygen and decrease the chance of arterial hypoxemia.
Intraoperative Awareness is about ______%
0.15%
Risk factors for intraopertive awareness
Substance abuse
Underlying conditions.
Gender
Age
Paralytic use
Type of surgery
Poor anesthesia machine maintenance.
Concentrations of inhaled anesthetics that provide loss of awareness and recall are about _____ to _______MAC
0.4 - 0.5 MAC
Malignant Hyperthermia
Profound release of Calcium from the sarcoplasmic reticulum.
Ryanodyne receptor (RYR1)
Hypermetabolic event
MH: Induced by inhalational agents and succinylcholine EXCEPT:
N2O
Malignant Hyperthermia S/S:
Muscle rigidity
Metabolic/respiratory acidosis.
Tachycardia (arrhythmias).
Temperature increase. (up to 1CC every 5 minutes -late sign).
Factors that influence the cost of inhaled anesthetics:
- Price (cost per milliliter of liquid)
- Inherent characteristics (ml of vapor available per ml of liquid), potency, and solubility
- FRESH GAS FLOW
Low solubility anesthetics need _________ FGF.
Less
The United States healthcare system contributes ______ of all greenhouse gas emissions
5%-10%
Approximately ______ gallons of anesthetic greenhouse gases are vented into the environment every year.
500,000
_________ is the most destructive volatile agent to climate change.
can last up to 14 years in the atmosphere
Desflurane
Desflurane contributes to _______ of the estimated greenhouse effect from all volatile anesthetic pollution
80%
Using desflurane for one hour at 1 MAC equates to the greenhouse gas emissions of driving ________ miles in the average automobile
200 to 400
Isoflurane lasts _____ years in the atmosphere and sevoflurane lasts ______ year
One hour of anesthesia with isoflurane can be compared to driving 20-40 miles, and sevoflurane 18 miles
3.2;
1.1
Nitrous oxide is a __________ and directly contributes to the destruction of the ozone layer.
The atmospheric lifetime of nitrous oxide is approximately ______.
chlorofluorocarbon;
114 years
When using nitrous oxide as a carrier gas, the global warming impact of sevoflurane is increased by 590% and isoflurane by 290%
(T/F)
T
should be considered as an alternative to the use of volatile anesthetics to reduce or eliminate the negative impact on the environment.
Total intravenous anesthesia (TIVA)
the weight of a gas dissolved by a liquid is proportional to the pressure of the gas upon the liquid.
Henry’s law
is the relationship between a gas’s rate of diffusion or effusion and its molecular weight.
Graham’s law of diffusion
states that the pressure, volume, and temperature of a gas are directly proportional to each other, as long as the number of particles and the mass of the gas remain constant. This law can be used to calculate the properties of a gas, such as its density or molar mass, given certain information about its pressure, volume, and temperature.
Ideal gas law
if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium shifts to counteract the change to reestablish an equilibrium. If a chemical reaction is at equilibrium and experiences a change in pressure, temperature, or concentration of products or reactants, the equilibrium shifts in the opposite direction to offset the change
Le Chatelier’s Law
that the rate of diffusion of a substance across unit area (such as a surface or membrane) is proportional to the concentration gradient.
Fick’s law states
