Nitrous Oxide Flashcards
Please note that the drug card information is for Educational Use ONLY, and the source is from Carrie Bowman's glossary of drug cards permitted by use of Georgetown NAP students. No permission is given to use these cards for anything other than as a study resource for our program.
What is another name for N2O?
laughing Gas!
What is the drug classification for nitrous oxide?
inhaled anesthetic
What is nitrous oxide (describe the gas!)?
it is a low-molecular weight, odorless to sweet-smelling nonflammable gas of low potency and poor blood gas solubility (0.46) that is most commonly administered in combination with opioids or volatile anesthetics to produce general anesthesia
What is the MOA of nitrous oxide?
Current theory is that target proteins (most likely ion channels and/or receptors) are the site of action of the inhaled anesthetics
-separate sites of action for loss of consciousness and immobility have been proposed
How is Nitrous Oxide metabolized?
- an estimated 0.004% of an absorbed dose of nitrous oxide undergoes reductive metabolism to nitrogen in the GI tract
- Anaerobic bacteria, such as Pseudomonas, are responsible for this reductive metabolism
- there is no evidence that nitrous oxide undergoes oxidative metabolism in the liver
What inhibits the metabolism of nitrous oxide by anaerobic bacteria?
-oxygen concentrations of >10% in the GI tract and antibiotics inhibit the metabolism of nitrous oxide by anaerobic bacteria
What is the elimination route for nitrous oxide?
Eliminated almost entirely unchanged via the lungs
How does nitrous oxide produce anesthesia; and how does this involve the volume of distribution?
- When nitrous oxide is added to inspired air at a concentration that will produce anesthesia, the rate at which this equilibrium is approached depends on the blood/gas partition coefficient
- The lower the blood/gas coefficient, the lower the solubility in the blood
- a lower solubility in the blood allows the gas to reach alveolar/arterial equilibrium quickly
Tell me about Nitrous Oxides blood/gas and oil/gas partition coefficient…
Has a LOW blood/gas partition coefficient (0.46), which allows the gas to achieve a given partial pressure in the blood very quickly compared with other available inhaled agents
-In addition, nitrous oxide also has low oil/gas partition coefficient of 1.4, which allows for a fast recovery from anesthesia
Does nitrous oxide reach equilibrium fast or slow? why?
Due to low blood/gas partition coefficient, N2O reaches equilibrium very fast and uses the same principle for elimination or washout; the speed of elimination mirrors that of the rate of equilibrium!!!!
What is diffusional anoxia? What drug is this a side effect of?
(Transient hypoxia) can occur during recovery of nitrous oxide anesthesia due to the transfer of gas from the blood and to the alveoli which can be sufficient to reduce, by dilution, the alveolar partial pressure of oxygen
-side effect of Nitrous Oxide!
What is the typical respiratory pattern with nitrous oxide?
Increased RR, Decreased Tidal Volume, and Reduced hypoxic drive
What are the neurological side effects of nitrous oxide?
Increases in CBF, Cerebral Metabolic Rate (CMR), and ICP
What are the CV side effects of nitrous oxide?
- Myocardial depressant and sympathomimetic
- it may cause increases in pulmonary vascular resistance with the greatest response in patients with pre-existing pulmonary HTN
- may also elicit a compensatory, sympathetically mediated increase in SVR
What can nitrous oxide cause in a gas sense?
- Expansion of gas
- Bowel gas expansion is associated with the use of nitrous oxide in abdominal surgeries and this expansion can interfere with surgical closure
- can accumulate in gaseous cavities and therefore exacerbate such conditions as pneumothorax and pneumocephalus
- 75% nitrous oxide can expand a pneumothorax to double or triple its size in 10-30 minutes
- Air-filled cuffs of pulmonary artery catheters and endotracheal tubes also expand with the use of nitrous oxide, possibly causing tissue damage
