Inhalational Anesthetics Flashcards
What is the MOA of nitrous oxide?
NMDA receptor antagonist
What does NO do to myocardial contractility?
Depresses it
What does NO do to sympathetic nervous system?
Stimulates it so increases BP, CO, and HR because of the release of catecholamines.
What does NO do to the pulmonary vasculature?
Increases its resistance so causes increase in right ventricular end diastolic pressure
What does NO do to the respiratory system?
Increases the respiratory rate and decreases the tidal volume as a result of CNS stimulation.
It decreases hypoxia drive mediated by the carotid body chemoreceptors
What are the effects of NO in the CNS?
It increases CBF –> mild elevation in ICP
It increases CMRO2 (oxygen consumption in the brain)
What does NO do to muscle relaxation?
Actually causes skeletal muscle rigidity
What does NO do to renal system?
Decreases renal blood flow by increasing renal vascular resistance, decreasing GFR and UOP
What does the use of NO increase the risk of postoperatively?
PONV by activation of the CTZ
How is NO eliminated?
Thru exhalation
What enzyme does NO inhibit?
It irreversibly oxidizes the cobalt atom in vitamin B12 so it affects every vitamin b12 pathway.
- myelin synthesis (methionine synthase), DNA synthesis (thymidylate synthase)
CAN CAUSE MEGALOBLASTIC ANEMIA AND PERIPHERAL NEUROPATHIES
Is NO teratogenic?
Yes
How does NO modulate the immune response?
It affects chemotasis and motility of PMNs
What are the contraindications to using NO
Pneumothorax, air embolism, SBO, pneumocephalus, tympanic membrane grafting (diffuses into air containing cavities due to solubility increasing the pressure within the cavity)
Pregnancy
What does NO do with other gases?
Decreases the MAC
Attenuated the circulatory and respiratory effects of volatile anesthetics
Potentials neuromuscular blockade
What are the effects on CV with isoflurane?
Increase in heart rate due to mild stimulation of beta receptors (no change in cardiac output)
What does isoflurane do to coronary arteries?
It dilates them
What are the respiratory effects of isoflurane?
Bronchodilates
Irritates the upper airway reflexes
Fall in minute ventilation
What does isoflurane do to the CNS?
Increases CBF and ICP at MAC greater than 1 (reversed by hyperventilation)
Reduces CMRO2
At MAC 2 it produces and electrically silent EEG
What does isoflurane do to muscles?
Relaxes them
What does isoflurane do to the renal system?
Decreases renal blood flow and therefore GFR and UOP
What is isoflurane metabolized to?
Trifluoroacetic acid
Can isoflurane trigger malignant hyperthermia?
Yes
What’s the difference between desflurane and isoflurane?
Desflurane has a fluorine atom instead of a chlorine atom
Why does desflurane cause rapid induction and emergence?
It’s low solubility
What is the blood/gas partition coefficient of desflurane?
0.42
What is the vapor pressure of desflurane?
High
What ar the cardiovascular effects of desflurane?
Cardiac output is maintained by mild beta stimulation
With increased dose it causes a decline in SVR
Increased CVP and pulmonary artery pressure
What do rapid increases in desflurane concentration lead to ?
Transient increases in heart rate, BP and catecholamines levels
What drugs attenuate the heart effect of desflurane with rapid increases in dosage?
Fentanyl
Clonidine
Esmolol
What does desflurane due to tidal volume?
Decreases it
What does desflurane do to respiratory rate?
Increases it
What do volatile anesthetics do to respiratory drive?
Decreases the ventilatory response to increasing PaCO2
Why is desflurane a poor choice as an induction agent?
It causes airway irritation
Can cause laryngospasm