Inhalation Anesthesia Part 3 - Quiz 6 Flashcards
What is the relationship of the concentrations of Des, Sevo, and Isoflurane have with Mean Arterial Pressure?
As the concentration of these gases increase, MAP decreases in a dose dependent manner d/t a decrease in SVR
Out of Des, Sevo, and Isoflurane, which gas has the least Dose-Response relationship in regards to MAP
Sevoflurane
How does Halothane decrease MAP?
Halothane decreases MAP by decreasing Cardiac Output
How does N2O affect the MAP?
N2O mi**ldly increases MAP if at all
Activates SNS to increase SVR
What happens if you add N2O to other gases?
Decreases the magnitude of BP drop
At what concentration of Isoflurane would you start to see HR increase?
0.25 MAC
At what concentration of Desflurane would you see start to see a HR increase?
< 1 MAC: mininmal HR increase
≥ 1 MAC: linear dose dependent HR increase
At what concentration of Sevoflurane would you start to see a HR increase?
> 1.5 MAC
How do Inhalation Anesthetics affect Cardiac Index?
Cardiac Index is minimally influenced by gases
What are the Circulatory Effects with an abrupt increase of Desflurane & Isoflurane
to > 1 MAC?
Transient Circulatory Stimulation - increased plasma Epi & Norepi
Not seen w/ other gases
How do gases (except for Halothane) effect Myocardial Conduction?
Does not cause PVC’s d/t prolonging effective refractory period
Halthone makes it easier for PVCs to happen
How do Inhaled Anesthetics affect the QT Interval?
Prolongs QT Interval
Avoid Sevo in pts w/ Long QT Syndrome
What is Coronary Steal?
Side effect of Isoflurane that can worsen myocardial ischemia - Not found valid
Reduced blood flow from ischemic part of the heart & increases blood flow to the healthy part of the heart
What is Ischemic Preconditioning?
- Anesthetic gas exposes heart to brief episodes of ischemia that protects it from subsequent prolonged ischemia
- Present in all tissues
When do the Two Periods of Ischemic Preconditioning occur?
- 1-2 hours after episode
- 24 hours later & lasts 3 days
What is the crucial event in Ischemic Preconditioning that causes the protective activity?
Opening of ATP-Sensitive Potassium (KATP)
30-40% d/t this
How does the concentration of anesthetic gas relate to Respiratory Rate & Tidal Volume?
As gas concentration increases, Respiratory Rate increases & Tidal Volume decreases
How does anesthetic gas affect Minute Ventilation, Gas Exchange & PaCO2?
Minute Ventilation: Same
↑Dead Space Ventilation
↑PaCO2
↓Gas Exchange
How does Anesthetic Gas affect Respiratory Response to CO2?
Dose Dependent decreased/blunted response to CO2
How does Anesthetic Gas affect the Chest Wall?
Diaphragm goes toward the Head
Ribs go Inward
Results in Decreased FRC & Atelectasis
How does Anesthetic Gas affect Hypoxic Pulmonary Vasoconstriction (HPV)?
Limited Effect unless there is Bronchoconstriction
Which volatile gases are Nonpungent?
Sevo
Halothane
N20
Which volatiles gases are Pungent?
Desflurane & Isoflurane
Produces Irritation - Cough, Breath Holding, Laryngospasm
What affect does Anesthetic Gas have on Cerebral Vascular response to PaCO2?
No Effect
Inhalation agents ________ CMRO2, cerebral metabolic O2 requirement, except for N2O?
Inhalation agents decrease CMRO2, cerebral metabolic O2 requirements
N2O increases CMRO2
At what MAC does Cerebral Vasodilation occur?
> 0.6 MAC
Dose-dependent increase in CBF
What happens in the 2 Phases of dose-dependent effect of inhalation agents on CBF?
- First Phase
- @ 0.5 MAC: Decreased CMRO2 offsets Vasodilation - No change in CBF
- Second Phase
- ≥ 1 MAC: Vasodilation takes over - Increased CBF
What are the effects of N2O on the CNS?
Cerebral Vasodilation
&
↑CMRO2
What would you give with N2O to counteract its effect on the CNS?
Opioids
Barbituarates
Propofol
Which gases would Increase ICP with a MAC > 1?
All of them @ MAC > 1
At what MAC is CNS Autoregulation impaired?
< 1 MAC
What is SSEP?
SamatoSensory Evoke Potentials - Evaluates integrity of Brain & Spinal Cord
How do Anesthetic Gases & N2O affect SSEP?
Depresses Amplitude & Increase Latency of SSEP according to dose
At what MAC are Evoked Potentials abolished?
1 MAC
or
0.5 MAC if Gas + N2O
What would Increased Depth of Anesthesia look like on an EEG?
Increased Amplitude & Synchrony
As Depth of Anesthesia increases, Burst Supression occurs with _______ frequency
As Depth of Anesthesia increases, Burst Supression occurs with greater frequency
At what MAC will you see an Isoelectric pattern on an EEG?
1.5 - 2.0 MAC
Which gases are associated with Epileptiform Activity on the EEG?
Sevoflurane & Enflurane (Ethrane)
How do Inhalation Agents affect Neuromuscluar Activity?
Dose-Dependent skeletal muscle relaxation & enhances neuromuscular blocking drugs
Which gas from most to least triggers Malignant Hyperthermia?
Halothane > Isoflurane > Sevoflurane > Desflurane
What are symptoms of Malignant Hyperthermia?
Increased EtCO2 - Earliest/Most sensitive sign
Fever
Tachycardia
Cyanosis
Rigidity/Trismus
What rare liver effects might result after receiving Inhaled Anesthethics?
Immune Mediated Liver Injury
Liver Necrosis leading to death
Caused by Trifluoroacetate Metabolite
Other than immune mediated, how else can inhaled anesthetics cause mild liver injury?
Decreased O2 to Liver & Decreased Liver Blood Flow
↑Serum Transaminase Levels
Which gases are most hazardous to the liver due to metabolism?
Halothane > Isoflurane > Desflurane
Halothane Hepatitis
When are Inhaled Anesthetics avoided with patients who have liver disease?
Avoid using gases in patient who previously had liver damage d/t inhaled anesthetics.
Not harmful otherwise.
How does Methoxyflurane cause Nephrotoxicity?
Production of Inorganic Fluoride
How might Sevoflurane & Halothane cause Nephrotoxicity?
Sevo & Halothane breaksdown into Compound A –> Prolonged exposure = Nephrotoxicity
What can happen if Sevo has been given with low fresh gas flow for over 2 hours?
Compound A –> Proteinuria, Enzymuria & Glycosuria
Which Inhaled Anesthetic should be avoided for pts with Vitamin B Deficiency?
N2O - stops methionine from regulating Vitamin B & Folate metabolism
What causes Homocysteine levels to increase, which increases risk for coronary events?
N2O - stops methionine from converting Homocysteine to methionine
Why does N2O cause air filled cavities to expand?
N2O goes into cavity 34x faster than Nitrogen can leave the cavity, increasing the volume and pressure.
This can cause a Pneumo
What happens when the Soda Lime is fully dessicated?
Carbon Monoxide production from the Gases
Which gas has the highest risk of fire when used with a fully dessicated soda lime?
Sevoflurane
What is produced when Isoflurane & Desflurane is exposed to a fully dessicated Soda Lime?
Carbon Monoxide
What is the best way to prevent Soda Lime related Fires?
Adequate Hydration of Absorbent
Change Frequently & When in Doubt
Turn off fresh gas b/t cases
What compounds are in the conventional CO2 Absorbents?
94% Ca(OH)2 - Calcium Hydroxide
5% NaOH - Sodium Hydroxide
1% KOH - Potassium Hydroxide
Which gases use a Variable-Bypass Vaporizer?
Sevoflurane
Isoflurane
Halothane
How does a Variable-Bypass Vaporizer work?
- Two streams of fresh gas
- One goes to the agent
- One bypasses agent reservoir
What is the Vapor Pressure of Sevoflurane
170 mmHg
What is the Vapor Pressure of Enflurane?
172 mmHg
What is the Vapor Pressure of Isoflurane?
240 mmHg
What is the Vapor Pressure of Halothane?
244 mmHg
What is the Vapor Pressure of Desflurane?
669 mmHg
What happens if you put an Inhaled Agent in the wrong Vaporizer?
High-Low-High
High VP Agent + Low VP Can = Higher amt. delivered than dialed
Low-High-Low
Low VP Agent + High VP Can = Lower amt. delivered than dialed
Which gas uses a special Heated Vaporizer?
Desflurane (Suprane)
How does a Tec 6 Vaporizer Work in different altitudes?
Heats Desflurane to 2 atm
High Altitude = lower amt. delivered
