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130 Cards in this Set
- Front
- Back
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what are the physical properties of nitrous
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*colorless GAS
*sweet odor |
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how is nitrous stored
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*stored under pressure in steel cylinder
*cylinder color is blue |
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what is the critical temp of N20
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36.5
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what is the definition of critical temp
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highest temp at which a substance can be liquified by any amt of pressure
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at < 36.5 it takes how much pressure to liquify N20
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74 ATMS
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when a vapor reaches it critcal temp what occurs
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it becomes a gas
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when a solid reaches its melting point what occurs
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it becomes a liquid
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when a liquid reaches its boiling point what occurs
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it becomes a vapor
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what is the difference b/t vapor and a gas
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temperature
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how does gas become a liquid
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cannot not be compressed into a liquid until it is cooled below its critical temp
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how does vapor become a liquid
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can be compressed at a constant temp into a liquid
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at room temp (20 c) what is the pressure in a N20 cylinder
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745 lbs/sq in or approx 51 atms gauge pressure
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1 atm= ____ lbs/sq in
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14.7
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what does the N20 gauge read
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51 approx
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the pressure of the vapor above the liquid N20 varies with what
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temperature
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at 0 degrees the pressure of N20 is what
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31 atm
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the colder the room the higher or lower the N20 pressure gauge will read
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LOWER
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if the temp is > 36.5 what will N20 be
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a GAS
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at room temp the N20 gauge will read what
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51 atms or 745 psig
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when will the N20 gauge stop reading the standard reading
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when all the liquid has vaporized
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what is the flammability of N20
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it is NOT flammable or explosive
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is nitrous stable in soda lime
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YES
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what are the analgesic properties of nitrous
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POTENT analgesic
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what are the anesthetic properties of nitrous
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WEAK anesthetic
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what is the MAC of N20 at 37 degrees C for a 30-55 y/o
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104%
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are the effects of N20 the same on each patient
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NO--they vary from pt to pt
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how is nitrous typically given
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with another agent (volatile agent or opioid)
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what is the blood-gas coefficent of nitrous
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LOW (0.47)
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what does the blood-gas coeffienct of nitrous effect
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the LOW coefficient makes for a RAPID induction and RAPID emergence
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upon emergence from N20 what happens to volume of N20
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there is a high volume output
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upon emergence from N20 what parameters are affected and how
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*alveolar O2 is diluted and arterial o2 drops
*PaCo2 diluted -stimulus to breath is decreased |
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with emergence effects from N20 the greatest effects are seen when
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the first 5 min
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what should be done on emergence from N2o
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give 100% oxygen for at least 5 min
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if N20 is given to a closed gas space what occurs at equlibrium
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partial pressure of N20 in the cavity is equal to PA
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the blood-gas coefficient of N20 is what
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0.47
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the blood gas coefficient of nitrogen is what
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0.015
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nitrous solubility coefficient is how much greater than nitrogen
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31 times
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the preferential transfer of nitrous into an air filled cavity does what to the cavity
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*increases pressure
OR *increases volume |
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what places would you see increased PRESSURE d/t non-compliant walls secondary to nitrous
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*occluded middle ear
*cerebral ventricles with air spaces *occluded sinuses |
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what places/situtions would you see increased VOLUME d/t compliant walls secondary to nitrous
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*bowel gas
*loops of intestine in obstruction *pneumothorax *pulm blebs *air emboli *pneumoperitoneum *intraocular pressure(increased) |
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the magnitude of the increase in pressure or volume caused by nitrous in a cavity is dependent on what
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*partial pressure of nitrous
*blood flow to the cavity *duration of the anesthetic |
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50% N20 would change te cavity size how
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double it
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75% N20 would change the cavity size how
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quadruple it
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after starting a central line when is it safe to give nitrous
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only after a CXR
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when is it ok to use nitrous with a pneumothorax
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NEVER--it is contraindicated with a pneumo
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why does bowel gas expand slowly
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b/c of low blood flow
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with a posterior fossa craniotomy intracranial venous pressure is negative or positive
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NEGATIVE
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when in the sitting position the pressure in the cranium is negative or positive
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NEGATIVE
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pressure in the sagital sinus is positive or negative
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NEGATIVE
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what could happen if doing a craniotomy in the sitting position and the sagittal sinus is exposed to air
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it can suck in air---potential for air emboli
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why is doing craniotomies in the sitting position controversial
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b/c of the potential for air emboli
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resection of meningiomas arising from the dural reflection overlying the saggital sinus poses a risk for what
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venous air embolism
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what is the most sensitive way to detect an air embolism
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echo
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on doppler how would you detect an air embolism
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you would hear a distinct murmur called a Mill-Wheel murmur
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how can nitrous effect an ET tube cuff
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it will diffuse into the cuff and can put pressure on the tracheal mucosa
-need to check pressure on cuff w/ long cases with N20 |
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how can nitrous affect the balloon of a swan ganz catheter
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it can rupture it--make sure to completely deflate the balloon
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if a pt has had a pneumocephalography or has had air in ventricles or CSF how long before they can have N20
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7 days
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what are the auditory complications of nitrous
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it is associated with post-op hearing loss
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how is nitrous used for tympanoplasty
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it is NOT
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nitrous cause what kind of middle ear pressure on emergenge
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NEGATIVE
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secondary to the type of pressure that nitrous creates upon emergence what kinds of sympoms are seen
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*serious otitis
*post -op N/V |
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with COPD pts what can be a complication nitrous can cause
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ruputure of blebs
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what does N20 do to the CNS
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depresses it
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does nitrous cause analgesia
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YES
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what causes the differences of pts being conscious vs unconscious on the same dosages of N20
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*indivdual differences
*physical status of pt |
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how does N20 affect CMRO2 and CBF
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it increases CMRO2 and CBF which INCREASES ICP
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N20 has what effect on O2 supply and demand
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less effect than other IA
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how are CMRO2 and CBF related with N20
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they are coupled
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when N20 is given with sevoflurane what happens to CBF and CBV
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they increase
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with N20 what happens to CBF response to CO2
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it is preserved
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nitrous has what effect on vessels
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vasodilatory
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is nitrous used with increased ICP
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NO
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what would you do with nitrous and a "tight field"
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turn off nitrous and hyperventilate
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regarding CV pattern of inconsistent hemodynamic changes with nitrous it is complicated by what factors
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*use of nitrous with volatile anesthetics
*use of N2O with opioids *use of N20 with anesthetic adjuncts *with or without the presence of CV dz |
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when would nitrous cause a modest increase in HR
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*healthy volunteers
*hyperbaric chambers *when given with volatile agents |
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what are the heart rate changes when nitrous is given with a volatile agent
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higher HR than when given alone
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when can nitrous can a decrease in HR
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*coronary artery dz anesthetized with halothane or isoflurane
*cardiac sx with fentanyl or MS |
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why would N20 cause a small increase in arterial pressure
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mild sympathomimetic effect
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what effects on arterial pressure does N20 have when comined with a volaltile anesthetic
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no effect or modest increase i BP
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when would N20 cause a decreae in arterial BP
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*coronary artery dz
*with or without an opioid |
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when are small increases in CO and stroke volume seen with N20
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*with 60% nitrous and 02
*nitrous and volatile agents |
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when are no changes in CO and stroke volume seen with N2o
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in a hyperbaric chamber
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when are decreased CO and stroke volume seen with N20
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*pts receiving opioids
*pts with cardiac dz |
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what is SVR durng volatile anesthesia with nitrous oxide
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HIGHER
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what is SVR when receiving opioids
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HIGHER
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what is SVR in pts with cardiac dz anesthetized with opioids
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HIGHER
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nitrous does what to venous tone?
this results in what? |
*INCREASES it
*decreases venous capacitance |
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N20 does what to pulmonary artery pressures
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increases them
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N20 does what to pulmoary vascular resistance
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INCREASES it
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N20 does what to venous return
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INCREASES it
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N20 does what to central venous pressure
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INCREASES it
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b/c of increases in system pressures what conditions should you be cautious in giving nitrous with
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*pulmonary HTN
*neonates (esp w/ congenital heart dz) *congentital heart dz |
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N20 does what to R to L atrial or ventricular shunting
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ENHANCES it so PaO2 is lowered
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is nitrous cardioprotective
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NO--it is not associated with cardioprotection
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T or F
Nitrous does NOT exacerbate myocardial ischemia |
FALSE
it MAY exacerbate ischemia |
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nitrous is a weak or strong sympathomimetic
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WEAK
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secondary to N2O's sympathomimetic properties what effects will be seen
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*pupillary dilation (may be masked by opioids)
*diaphoresis |
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what type of hemodynamics do you get with nitrous
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relatively stable
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is nitrous good with asthma?
why or why not |
NO
-it does NOT relax the bronchial smooth muscle |
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what is the resp pattern seen with nitrous general anesthesia
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regular, rhythmic, rapid and shallow pattern of breathing
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a pt spontaneously breathing on nitrous will have what type of PaCO2
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normal
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a pt spontaneously breathing on nitrous will have what changes in Vt
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it will go down
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a pt spontaneously breathing on nitrous will have what changes in RR
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it will increase
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a pt spontaneously breathing on nitrous will have what changes in minute volume
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it will be normal
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with nitrous there is a _____ increase in rate
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dose dependent
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does nitrous effect ventilatory response to PCO2
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NO
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nitrous like all IA profoundly depresses ventilatory response to what
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hypoxemia
(secondary to action on peripheral chemoreceptors) |
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hypoxemia is normally mediated by what
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carotid bodies
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1 MAC causes depression of what % of carotid bodies response
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50-70%
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1.1 MAC causes depression of what % of carotid bodies response
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100%
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with nitrous what happens to the synergistic effect of hypoxia and hypercapnia
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it is depressed
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nitrous does what to FRC
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DECREASES it
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N20's effect on FRC may be exaggerated by what
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nitrous induced skeletal muscle rigidity
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is nitrous safe for malignant hyperthermia
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YES
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what type of muscle relaxation is there with N20
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min to no skeletal muscle relaxation
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what types of musculoskeletal effects may be seen with N20 (more so with children)
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*clonus
*opisthotamus |
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what is N20's affect on neuromuscular blockers
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does NOT augment them
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nitrous interacts with what vitamin
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b-12
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what occurs with nitrous and methionine synthase
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it inactivates it
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N20 does what to megoblastic bone marrow activity
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depresses it
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what is methionine synthase and how does N20 affect it
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*it is an enzyme involved in he metabolism of B-12
-resembles pernicious anemia *N20 inactivates it |
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when is CNS depression seen with N20
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at 1000 ppm
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what is the NIOSH standard regarding N20
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that the OR is not > 25 ppm
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for sleeper c-sections how is nitrous usually utilized
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1/2 MAC N20 and 1/2 MAC of a volatile agent
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how is N20 useful in therapeutic abortions
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there is a decrease in blood loss
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what could be some potential causes for exposure leading to adverse reproduction and fetal development with N20
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*exposure in OR
(leaks in anesthetic system-masks, high pressure fittings, exhalation valves) *post-op exposure (ICU or PACU) |
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what are the main adverse effects of N20
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*expansion of gas in closed spaces
*diffusion hypoxia *post-op N/V *vit B-12 oxidation *effects DNA synthesis *increased incidence of spont abortion & devolpment delay |
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nitrous effects on vitamin b-12 oxidation can lead to what
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polyneuropathy
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nitrous effects on DNA synthesis leads to what
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decreases in RBC and leukocyte production
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what are some advantages of N20
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*cheap
*faster induction *safe for malignant hyperthermia *sweet odor (good for mask inductions) *maintains PaCO2 *minimal CV depression |
