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Anesthesiology
Exam 1
138
Veterinary Medicine
Undergraduate 4
09/30/2010

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Cards

Term
Three methods of storing and delivering oxygen to an anesthesia machine
Definition
liquid oxygen, compressed gas, oxygen generator
Term
what is the pressure of a full oxygen cylinder?
Definition
1900-2200 psi
Term
what is the pressure reduced by before oxygen enters the flow meter?
Definition
pressure reducing valve
Term
How do you determine how many liters of oxygen are left in an e-cylinder?
Definition
multiply psi by 0.3
Term
when should you change an oxygen cylinder?
Definition
when 100-200 psi remain
Term
What is the purpose of the "pin-index" system?
Definition
Prevents attachment of incorrect gas cylinder
Term
What is the purpose of the flow meter?
Definition
Measures gas flow in mls or liters per minute going to the vaporizer
Term
What is the oxygen flush valve?
Definition
Allows oxygen to bypass the flow meters and vaporizer, delivering pure oxygen to the patient. Flow rate is 35-75 L/min
Term
what is fresh gas?
Definition
oxygen + vaporized anesthetic
Term
Where is the fresh gas line attached to the breathing circuit?
Definition
fresh gas inlet
Term
What is the difference between rebreathing and non-rebreathing circuits?
Definition
In a rebreathing circuit, all exhaled gases except CO2 are recirculated and rebreathed by the animal. In a non-rebreathing system, none of the exhaled gases are rebreathed by the patient; all exhaled gases are sent to a scavenger.
Term
What is the purpose of the unidirectional valves in a circle system?
Definition
Keep the gas flowing in one direction and prevents the animal from rebreathing carbon dioxide
Term
What happens to exhaled carbon dioxide in a circle system?
Definition
Removed by the CO2 absorber or evacuated by the scavenge.
Term
How do you know what size reservoir bag to use in a circle system?
Definition
30ml/lb or 6 times tidal volume
Term
What is the purpose of the reservoir bag?
Definition
Acts as a reservoir, monitor breathing, bagging
Term
What is the difference between a semi-closed and a closed circle system?
Definition
closed = all exhaled gases rebreathed, oxygen flow rate equal to metabolic requirements, pop off valve closed or open.
semi-closed = oxygen flow rate greater than metabolic requirements, some exhaled gas exits through partially open pop-off valve
Term
Adult size breathing circuits are for patients over ___ lbs. The pediatric size breathing circuit is for patients between ___ and ____ lbs.
Definition
20, 6, 20
Term
What does dead space refer to?
Definition
begins at y-piece, may include face mask or endotracheal tube extending beyond the nose
Term
Purpose of the pressure manometer
Definition
Measures pressure within a breathing system. Used to determine how big of a tidal volume to deliver to a patient.
Term
How big does the CO2 absorber need to be?
What are the granules made of?
Definition
2 x tidal volume, soda lime or bara lime
Term
Why does channeling occur?
Definition
uneven distribution/clumping of granules, allowing gases to bypass them. This can be caused by uneven packing or exposure to heat and water (byproducts of Co2 absorption)
Term
What is the pop-off valve?
Definition
Allows exit of waste gases to the scavenger, prevents buildup of pressure within the system
Term
What is the purpose of a universal F circuit? What is the minimum weight requirement to use these and why?
Definition
Aids in warming and humidification of inspired gases.
Increased inspiratory resistance, patients must be >20 lb
Term
Is a universal F circuit more like a bain circuit or a circle system?
Definition
Identical to a circle system. It is an alternate configuration of the y-piece in which the inspiratory tube runs on the inside of the expiratory tube.
Term
What are the advantages and disadvantages of a closed circle system?
Definition
Advantages = more economical, less pollution, conserves heat and humidity, do not have to close and open popoff valve
Disadvantages = Risk of hypoxia, takes longer to change anesthetic concentration
Term
What is meant by "low flow" anesthesia
Definition
semi closed system, when oxygen flow rate is close to the metabolic requirement but just barely exceeds it
Term
What are the advantages of a low flow system?
Definition
more economical, inspired gases are warmed and humidified, atmospheric pollution is reduced
Term
Potential disadvantages to a low flow system
Definition
hypoxia, changes to the anesthetic system are very slow, cannot be used on very small patients
Term
How do you test a circle system for leaks?
Definition
Close popoff valve, occlude the y-piece with your thumb, depress the oxygen flush valve until the manometer reads 20, observe manometer for decrease in pressure
Term
In a bain circuit, the patient inspires fresh gas from the _____. The patient exhales into the ______. What happens during the expiratory pause?
Definition
outer reservoir tube (although it came from the inner tube originally)
outer reservoir tube.
Fresh gas from the inner tube flushes out expired gas from the reservoir tube
Term
What is the lowest oxygen flow rate that can be used in a bain circuit?
Definition
100ml/lb/min
Term
Does any rebreathing occur at this flow rate?
Definition
yes - to eliminate all rebreathing, you would need a flow rate of 3 times minute ventilation
Term
what is minute ventilation equal to?
Definition
RR (respiratory rate) x TV (tidal volume)
Term
Why is a bain ciruit used with patients less than 5-6 lbs?
Definition
decreased dead space and resistance to breathing
Term
Advantages and disadvantages of a bain circuit
Definition
advantages: compact, inexpensive, low dead space and resistance to breathing, facilitates scavenging of waste gases
disadvantages: uses more oxygen and anesthetic gas per lb, loss of heat and humidity, cannot use oxygen flush valve (barotrauma)
Term
How do you test for leaks in the inner tube of a bain circuit?
Definition
In systems fitted with a bag, push the oxygen flush valve. If tube is intact, the bag will be flat. If there are leaks, the bag will fill.
Term
What is the oxygen flow rate for a closed system?
Definition
2-3ml/lb/min (metabolic requirements)
Term
What is a peep valve?
Definition
addition to a circle system or bain ciruit, safety device used to prevent pressure build-up in a breathing circuit
Term
Difference between active and passive scavengers?
Definition
active = gas suctioned into scavenger via fan or vacuum
Passive = positive pressure pushes gas into scavenger
Term
What are three options for deposited scavenged gases?
Definition
1) Through a hole in the wall to the outside
2) f/air canister (activated charcoal)
3) Surgi-vet pure guard (activated charcoal)
Term
Why does the flow rate for a bain circuit have to be so high?
Definition
Necessary to wash out the majority of exhaled gases during the expiratory pause
Term
Why can't the o2 flush button be pushed when using a bain circuit?
Definition
may cause barotrauma because a high flow rate will rapidly cause a buildup of pressure due to the small volume of a bain circuit
Term
How is nitrous oxide stored in a compressed gas cylinder?
Definition
liquid and gas state
Term
How do you know how much nitrous oxide is in a compressed gas cylinder?
Definition
Weigh the tank before using and compare it to the full and empty weights stamped on the outside of the canister.
Term
What is the time constant and how is it calculated?
Definition
The time constant is used to give the anesthetist a rough idea of how long it will take for a change in anesthetic concentration to occur when using a circle system. It is calculated by dividing the total volume of the breathing circuit by the oxygen flow rate.
Term
How long after a vaporizer dial setting is changed does circuit concentration change?
Definition
5 time constants
Term
if a circuit has a volume of 5 L, and the fresh gas flow rate is 2L/min, what is the time constant? How long would it take for a circuit concentration to match the vaporizer dial setting?
Definition
5/2 = 2.5 minutes
2.5 * 5 = 12.5 minutes
Term
Reasons for IV access
Definition
anesthetic agents, emergency drugs, fluids, blood, plasma, parenteral nutrition, repeated IV meds, monitor central venous pressure and mean arterial pressure
Term
Why use a catheter instead of a needle?
Definition
Repeated use causes vessel damage, hematomas, etc.
Easily dislodged, perivascular injection more likely, difficult to secure in place
Term
Most common catheter for IV anesthesia/short term use
Definition
over-the-needle
Term
Type of catheter used long term or as a central line
Definition
through-the-needle
Term
What are wire guided catheters used for?
Definition
long term, central venous or arterial line
Term
material used for short term, inexpensive catheters
Definition
teflon
Term
flexible but expensive material used for long term
Definition
polyurethane
Term
Name the catheter sites for the following species
dog
Definition
cephalic, jugular, lateral saphenous
Term
cat
Definition
cephalic, jugular, medial saphenous
Term
small ruminants/horses
Definition
jugular, cephalic, lateral thoracic
Term
cows
Definition
jugular or auricular
Term
pigs, rabbits, some dogs
Definition
auricular
Term
considerations for choosing a site
Definition
must not interfere with surgery, should be accessible during surgery, check patency (inspect and palpate)
Term
in what direction are catheters always placed?
Definition
with blood flow - towards heart
Term
Materials used to secure a catheter
Definition
tape, suture, glue, staples, +/- bandage and/or antibiotic ointment
Term
maintenance of catheter
Definition
flush with heparinized saline every 4-6 hours, inspect every 24 hours
Term
main purpose of endotracheal intubation
Definition
insert tube into the trachea to provide a patent airway
Term
Advantages of an endotracheal tube
Definition
Administration of oxygen and inhaled anesthetic agents
Assist or control ventilation
Protect airway
Tracheal suctioning & sampling
Term
4 methods of placement
Definition
orotracheal, nasotracheal, via pharyngotomy or tracheotomy
Term
what does the endotracheal tube size indicate?
Definition
internal diameter in mm
Term
what happens to resistance to breathing as the size gets bigger?
Definition
decreases
Term
How far down the trachea should the tube be placed? What happens if it is too short or too long?
Definition
Cuff should be in middle third of trachea. If it is too short, it is too easily dislodged. If too long, may intubate a main-stem bronchus, increases dead space
Term
What is the purpose of murphy's eye?
Definition
safety device in case end of the tube gets blocked
Term
Which is better, high-volume or low-volume cuffs and why?
Definition
high volume cuffs will exert less pressure per square inch and there is less risk of trauma
Term
When are cole tubes used?
Definition
Used in birds and very small patients, due to larger diameter that will fit without a cuff
Term
considerations for use of a stylet
Definition
may help in small ruminants, swine, and rabbits. may cause trauma if not careful
Term
species in which laryngospasm is common - what drug can be used to suppress this in cats?
Definition
humans, cats, pigs
lidocaine
Term
What are the negative consequences of esophageal intubation?
Definition
gastric distention, risk of aspiration, No delivery of oxygen or gas to lungs
Term
What kinds of things can cause an occluded tube?
Definition
Mucus, saliva, blood, foreign material, "herniated" cuff, tip lodged against wall of trachea, kinking if head is tipped forward
Term
What kinds of things can cause tracheal damage?
Definition
over-inflation of the cuff (never use cuffed tubes with birds,) harsh chemicals used to disinfect the tubes
Term
species in which you can perform orotracheal intubation with direct vision
Definition
dogs, cats, birds, pigs, small ruminants
Term
species you must do blind
Definition
horses, rabbits
Term
species you can do blind with palpation
Definition
large ruminants
Term
how do you know how much to inflate the cuff?
Definition
inflate so a leak begins at 15-20 cm water to offer some protection against barotrauma
Term
list four ways that you can be 100% sure the tube is in the trachea
Definition
look with laryngoscope, palpate for two tubes, auscultate thorax when giving a breath, capnography (gold standard)
Term
list other things that can help confirm placement
Definition
movement of reservoir bag, condensation in the tube, patient may cough
Term
suspect esophageal intubation if..
Definition
regurgitation soon after, patient wakes up after several minutes, cannot get cuff to seal, patient can vocalize
Term
Why should we monitor anesthetized patients?
Definition
identify problems early, institute treatment promptly, keep patient safe
Term
overall goal of monitoring
Definition
ensure tissue perfusion with oxygenated blood
Term
subjective monitoring
Definition
anesthetist using touch, sound, and vision to assess patient's vital signs
Term
objective monitoring
Definition
involves the use of monitors to assess a patient's vital signs.
Term
Three main areas of monitoring
Definition
circulation, oxygenation, ventilation
Term
what is electrical mechanical dissociation?
Definition
electrical activity without mechanical activity
Term
What three types of pressures indicate mechanical activity?
Definition
pulse pressure, mean arterial pressure, central venous pressure
Term
3 different ways to connect ECG leads to a patient
Definition
alligator clips, fine gauge wire needles, stick-on patches
Term
What is pulse pressure? Is it a good indicator of mean arterial pressure?
Definition
pressure produced by movement of blood through the whole arterial system. equal to systolic pressure - diastolic pressure
Term
2 methods of auditory pulse monitoring
Definition
esophageal stethoscope, Doppler
Term
How does the doppler work?
Definition
An ultrasonic probe that emits ultrasound frequency waves is placed over a peripheral artery. Another crystal receives the returning echoes, which are sent to the electronic monitor, which converts it to a whooshing sound. Systolic pressure is when you can hear the blood when the cuff is slowly released
Term
How can false readings be made by the doppler?
Definition
patient positioning, blood flow altered by ties, motion, proficiency of using machine
Term
MAP =
Definition
MAP = CO x SVR
Term
CO =
Definition
CO = HR x SV
Term
SV =
Definition
load x contractility
Term
define mean arterial pressure. what pressure needs to be maintained during anesthesia?
Definition
Lateral force per unit area exerted on a vessel wall. It is what drives blood. greater than 60 mm Hg needs to be maintained
Term
How do you calculate MAP?
Definition
(systolic + diastolic + diastolic)/3 = MAP in mm Hg
Term
Name two indirect methods of getting arterial blood pressure.
Definition
doppler, oscillometric
Term
How does the Dinamap (oscillometric method) work?
Definition
Detects pressure pulsations produced within a cuff bladder - microprocessor inflates device to suprasystolic pressure and then deflates. can measure Systolic, diastolic, and mean pressures
Term
How do you determine the cuff width? What happens if the cuff is too small or too large?
Definition
40% of limb circumference. If it is too narrow, values are artificially elevated. If too wide, values are artificially low
Term
best location for cuff placement on a
cat
dog
horse
ruminant
Definition
above elbow on medial side
distal forelimb or rear limb
tail
tail or distal limb
Term
Name two direct arterial blood pressure methods
Definition
1) Mechanical movement converted to electrical energy via a transducer and red with an oscilloscope
2) Pulsations red with an aneroid manometer
Term
Where exactly is CVP measured and what does it tell us about the heart?
Definition
intrathoracic vena cava or right atrium. It reflects the ability of the heart ot pump blood returning to it, and adequacy of circulating blood volume.
Term
2 observation methods of ventilation monitoring
Definition
thoracic wall movement or breathing bag movement
Term
two auditory methods of monitoring ventilation
Definition
"honker" or esophageal stethescope
Term
two methods of measuring carbon dioxide (as indicator of ventilation)
Definition
blood gases, capnograph
Term
4 things to assess when visually observing ventilation
Definition
rate, rhythm, nature, effort
*look for sudden changes in rate
Term
reasons for tachypnea
Definition
too light or too deep, drug induced, obese, geriatric, hypoxia
Term
reasons for bradypnea or apnea
Definition
CNS depression, opioids, barbituates, propofol, after neuro procedures
Term
how does a honker work?
Definition
measures changes in air temp
Term
Capnograph is an instrument that measures ______ to provide an estimate of _____
Definition
end tidal CO2, arterial partial pressure of carbon dioxide
Term
what is the normal partial pressure of arterial co2?
Definition
40-45 mm Hg
Term
in regards to ventilation, increased CO2 indicates...
Definition
hypoventilation, overproduction, rebreathing
Term
in regards to ventilation, decreased CO2 indicates...
Definition
hyperventilation, cardiac arrest
Term
what is cardiogenic oscillation?
Definition
undulations in capnogram that are synchronous with cardiac contractions
Term
Reasons for rebreathing of carbon dioxide
Definition
dead space, faulty unidirectional valves, used up CO2 absorber
Term
Difference between a mainstream and a sidestream capnograph
Definition
Mainstream = sensor placed directly btwn ET tube and breathing circuit.
Sidestream = sensor chamber located in computerized monitor and air is pulled through a tube attached between the ET tube and breathing circuit.
Term
advantages/disadvantages of a sidestream
Definition
adds little dead space, but there is a 2-3 second delay
Term
3 methods of monitoring oxygenation
Definition
mucous membrane color, arterial blood gas analysis, pulse oximetry
Term
3 things that adequate oxygenation depends upon
Definition
adequate blood oxygen (bound and dissolved)
adequate hemoglobin content
adequate peripheral perfusion
Term
at what point on the oxyhemoglobin dissociation curve do you become hypoxic?
Definition
90% saturation of hemoglobin
PO2 of 60 mm Hg
Term
At what level of unsaturated hemoglobin does cyanosis occur? Why is this an unreliable indicator?
Definition
5 g unsaturated hemoglobin/100 ml
anemia, bad lighting, skin pigment
Term
How do you determine mathematically how much oxygen is bound to hemoglobin?
Definition
PCV/3 = Hgb/dl

(%saturation) x (hgb/dl) = g saturated hemoglobin
Term
Does the pulse ox determine P02 or saturation? Is this always a good indicator of perfusion?
Definition
Saturation
No, dissolved oxygen must be assessed
Term
Information provided by arterial blood gas analysis
Definition
acid-base status, hemoglobin saturation, PO2, partial pressure of carbon dioxide
Term
information provided by pulse ox
Definition
continuous reading of %saturation of hemoglobin.
pulse rate, rhythm, cardiac output
Term
How does the pulse ox work?
Definition
Hgb and Oxyhgb absorb at different wavelengths. Light passes through a tissue bed, and a sensor reads the absorption of light. HR is determined by detecting pulsations in the small arterioles
Term
What can cause interference with the pulse ox?
Definition
motion, poor perfusion, optical interference (external light, anemia, carbon monoxide, methemoglobin, intravascular dies)
Term
How to you monitor depth of anesthesia?
Definition
CNS activity (EEG), muscle tone, response to stimuli, sympathetic responses (HR, BP, RR,) eye position/movement
Term
surgical plane of anesthesia is indicated by what eye position?
Definition
cross-eyed and dull palpebral reflex
Term
In horses, what eye activity indicates a light plane of anesthesia?
Definition
nystagmus and tearing
Term
How to monitor blood loss - subjectively and objectively
Definition
subjectively - inaccurate, can't see it all, 1 gauze can contain 10 mls of blood
objectively - weigh swabs, measure volume in suction canisters
Term
Where is core body temperature taken? What about peripheral?
Definition
esophageal or middle ear
rectal, nasal
Term
Consequences of hypothermia during anesthesia
Definition
increased cardiac irritability, shivering increases oxygen requirements, decreases recovery time, decreases anesthetic requirements, hypoventilation, increased blood viscosity
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