Test 3: Comparison of Volatile Agents Flashcards
What are the side effects of Enflurane?
-Nephrotoxic
-Inc CBF, inc ICP, inc CSF production
-Avoid in neuro cases
What are the CV Effects of Isoflurane?
-Dec MAP due to dec SVR
-Inc HR (mild)
-Dec CO (or no change)
-Coronary vasodilator (more than any other volatile!!)
-Coronary Steal Syndrome risk (reduce risk by keeping them normotensive and maintaining perfusion pressure)
What are the CNS effects of Isoflurane?
-Inc CBF and ICP at >1 MAC (less than all other agents)
-Dec CMRO2 more than any other volatile
-Preserves autoregulation
-Cerebral Protective
What are the Respiratory effects of Isoflurane?
-Decreases tidal volume (similar to other volatiles)
-Slight inc in RR
-Very decreased MV
-Decreased response to CO2
-Increased PaCO2
-Bronchodilator
What are the Misc effects of Isoflurane?
-Halogenated methyl ethyl ether
-Isomer of enflurane
-Most widely used volatile (cheap)
-Stable in storage
-Very minimal hepatic metabolism (0.2%)
-Can dec renal blood flow -> Dec GFR and Dec UOP (avoid by maintaining BP within autoregulation parameters)
What are the CV effects of Halothane?
-Decreases MAP from direct myocardial depression
-No impact on SVR
-Increased incidence of ventricular arrhythmias (junctional rhythms or bradycardia from slowed SA node conduction)
-Increases the arrhythmogenic properties of Epi (ED50 of Epi 1.5-2.1mcg/kg)
What are the Respiratory effects of Halothane?
-Bronchodilation
-Decreased Tidal Volume, Increased RR
-Decreases response to CO2 (less than other agents)
-SEVERELY depresses the hypoxic drive (problem for COPD and OSA patients)
What are the CNS effects of Halothane?
-Significant increases in CBF, increases ICP > than other agents
-Decreases CMRO2
-Autoregulation is blunted and completely abolished at high concentrations (!!)
What is the metabolism of Halothane?
-Metabolized more than any other agent
-Oxidative/reductive metabolism involving CYP450 (!) (only volatile agent to undergo reductive metabolism)
-Metabolized 20% with the first exposure, and increases with repeated exposures.
-More hepatotoxic than other agents (!)
What are the metabolites of Halothane?
Bind to hepatocytes, causing damage.
-Trifluoroacetic acid (TFA)
-Free bromide
-Free chloride
What are the misc effects of Halothane?
-Halogenated Alkane
-Clear & colorless with pleasant odor
-Non-irritating to airways
-Inhalation induction
-Thymol added as a preservative to enhance stability
-Most potent historically (Of the currently used agents, Iso is the most potent)
What are the Misc effects of Desflurane?
-Halogenated methyl ethyl ether
-Less potent than other volatile agents (MAC 6%)!!
-Pungent, airway irritant -> coughing, laryngospasm if awake.
-Minimal metabolism (!)
-Most expensive agent
-Good choices for super obese or really bad liver failure.
What is the Vapor Pressure of Desflurane?
664 mmHg
Why does Desflurane need a special vaporizer?
-Cannot be exposed to room air (directly inserted and tipped up to fill vaporizer) due to increased Vapor Pressure
-Necessitates special heated and pressurized vaporizer
-Tech 6
Why does Desflurane have a rapid onset?
Less potent = faster onset. Doesn’t stay in the bloodstream. Goes into other compartments easily.
-Low solubility
Why does Desflurane have a prompt recovery?
Don’t have to wait for metabolism: concentration gradient helps with recovery.
-It’s not getting saturated in fatty tissues and hanging out there.
-Not required to wait around for liver metabolism.
-If good pulmonary mechanics are happening, should be able to get this off quickly.
What are the Cardiac effects of Desflurane?
-Rapid inc in concentrations lead to transient inc in HR
-Can confound pain indicators (causes tachycardia)
-Does not increase coronary artery blood flow
-Effect on other organ systems similar to Isoflurane
What is the metabolism and metabolites of Sevoflurane?
-2-5% metabolized
-Metabolites: inorganic fluoride,
hexafluoroisopropanol
What is important to know about Sevo and CO2 Absorbents?
-Breaks down to Compound A in the presence of strong bases found in CO2 absorbents
-Nephrotoxic
-Moved away from Soda Lime so not as big of a problem anymore
What are the misc. effects of Sevo?
-Halogenated Methyl Isopropyl Ether
-Rapid induction
-Prompt recovery
-Non-pungent (!)
-Lowest degree of airway irritation among currently used volatile anesthetics (!)
-Inhalational Induction agent (!)
-Can spontaneously degrade in a glass bottle (!)
What kind of gas is Xenon?
Noble gas.
-Colorless, odorless
-Low chemical reactivity
What are the effects of Xenon?
-Mac 71%
-B:G Solubility = 0.14
-Induction & Emergence is 3-4xs faster than Des or Sevo
-Non-explosive
-Minimal cardiac depression
-No metabolic effects
-Not harmful to the environment
-Potential risk of recall (!)
VERY Expensive. Extremely high cost has hindered its acceptance into clinical practice (BLUE BOX)
How is Nitrous Oxide stored?
Stored as a liquid and a gas in pressurized tanks.
-Non flammable, but Does support combustion (!)
-Stable at room temp
Anesthetic effects of N2O and other volatile agents are _____. Usually used in concentrations of __ - __ % to reduce the requirements of more potent agents. (Blue Box)
Anesthetic effects of N2O and other volatile agents are additive. Usually used in concentrations of 50%-70% to reduce the requirements of more potent agents.
How is N2O eliminated?
Almost entirely eliminated via the lungs.
-Approx. 1% undergoes metabolism.
The analgesic effects of 50% N2O are approx. equal to ___ mg of Morphine.
The analgesic effects of 50% N2O are approx. equal to 10 mg of Morphine.
What are the effects of Nitrous Oxide on the CNS?
-Increases CBF: potent vasodilator. Can be attenuated with hyperventilation.
-Minimal inc in CMRO2 (different from most volatiles)
-Minimal EEG changes
-No effect on autoregulation
-BIG inc in PONV (theoretically due to activation of the CTZ and vomiting center of medulla and connections to expansion of middle ear causing balance issues)
What are the cardiac effects of Nitrous Oxide?
-No significant change in HR, CO, or BP
-No significant change in ECG
-Mild, transient stimulation of SNS
-Inc Pulm. Vascular Resistance.
What is important to know regarding Nitrous Oxide and Pulmonary Vascular Resistance?
-N2O increases PVR.
-Exaggerated in patients with pre-existing pulmonary hypertension
-Neonates are especially vulnerable (Bronchopulmonary Dysplasia (BPD) or Respiratory Syncytial Virus (RSV) avoid N2O)
-Inc PVR in patients with congenital heart defects/diseases may result in inc R-to-L shunt (inc in deoxygenated blood circulating to the body, bypassing the lungs).
What are the respiratory effects of Nitrous Oxide?
-Mild dec in tidal volume and inc in RR
-Minute ventilation really no change, maybe slightly less than normal
-Hypoxic respiratory drive markedly decreased
-Ventilatory response to inc CO2 affected
Does N2O have renal effects?
No significant effects on kidney function
What are the hepatic effects of Nitrous Oxide?
Mild dec in hepatic blood flow
What are the neuromuscular effects of Nitrous Oxide?
-Does NOT provide muscle relaxation (different from volatiles)
-Can actually increase muscle tone in high concentrations
-Does NOT trigger MH
What are the hematologic effects of Nitrous Oxide?
-Inhibits enzymes that are Vitamin B12 dependent (Ex: Methionine synthetase)
-Causes bone marrow suppression (megaloblastic anemia)
-Causes peripheral neuropathies & pernicious anemia (disrupts DNA synthesis)
What are the effects of N2O on OB patients?
-Does NOT alter uterine smooth muscle contractility
-Will not start or stop labor
-Avoid repeated or lengthy use in 3rd trimester (Nagelhout).
-Inhibits methionine synthase (necessary for DNA synthesis), and teratogenic effects are seen in animal studies with high concentrations for prolonged periods. Some providers avoid N2O in pregnant patients.
What are the effects of N2O on a fetus?
-Increased incidence of spontaneous abortion with chronic exposure
-May be hazardous during 1st trimester due to issues with maturation
-Risk of brain development issues
What are the maximum amounts of Volatiles/N2O allowed in the air by NIOSH?
-2 ppm of Volatile
-25 ppm of Nitrous Oxide
OR air is filtered every 4 minutes
N2O is ___ times more soluble in the body than Nitrogen.
N2O is 34 times more soluble in the body than Nitrogen.
What happens if N2O enters a compliant space in the body?
Increase in volume
What happens if N2O enters a non-compliant space in the body?
Increase in pressure
What are examples of compliant spaces?
-GI tract
-Pneumoperitoneum
-Pneumothorax (Inhaling 75% N2O doubles the volume in 10 min)
-Air emboli
-ETT cuffs
What are examples of non-compliant spaces?
-Middle Ear
-Paranasal sinuses
-Cerebral Ventricles
-Eyeball
When are we concerned about air embolism?
In surgeries where the incision site is above the heart.
-Taking down highly vascularized tissues
-Inc CVP so air can’t be sucked into open venous sinuses
-Aspirate with CVC, patient’s right side up
