final prep Flashcards
define anesthesia
loss of sedation - one extreme in a continuum level of CNS depression
first inhalant anesthetic used?
diethyl ether
define general anesthesia
reversible state of unconsciousness, immobility and muscle relaxation
define surgical anesthesia
a stage of GA, analgesia and muscle relaxation
must be maximum effect to eliminate pain and movement during procedure
what is the biggest difference between general anesthesia and surgical anesthesia?
the level of pain control
define sedation
CNS depression, drowsiness, drug-induced
various levels from slightly aware to unaware of surroundings, aroused by noxious stimuli
when would we use sedation over anesthesia?
minor procedures
define tranquilization
calmness but not sleeping - patient is reluctant to move but still aware of surroundings
define hypnosis
drug-induced sleeplike state
impairs patient’s ability to respond to stimuli but can be aroused with sufficient stimulation
define narcosis
drug-induced state caused by narcotics - patient is not easily aroused
define local anesthesia
targets a small/specific area of the body
loss of sensation by drug infiltrated into the desired area
define regional anesthesia
loss of sensation to a limited area of the body
i.e. nerve blocks, epidurals and dental blocks
define balanced anesthesia or multimodal therapy
using multiple drugs in smaller quantities to maximize benefit
what are some advantages to using an endotracheal tube during anesthesia?
open airway less anatomical dead space precision administration of anesthetic agent prevent aspiration respond to respiratory emergency monitor respiration
what are the different types of endotracheal tubes available?
murphy tubes - beveled end w/ side holes
cole tubes - no side hole or cuff (birds and reptiles)
what type of ETT do we use here?
murphy tubes
what is the difference between a high volume/low pressure cuff and a low volume/high pressure cuff?
high vol/low pressure distribute pressure evenly where low vol/high pressure exert high pressure to only a small animal - this is a high risk for tissue damage
why would you want to make sure the ET tube is in the middle branch of the lungs?
if the ET tube is too deep it can cause atelectasis or CO2 buildup
what patients might you choose a supraglottic airway device over an ET tube with?
rabbits primarily, available for cats also
what is unique about SADs?
they allow airway management without invading the tracheal lumen
what are the two kinds of laryngoscope blades?
miller - straight
mcintosh - curved
what four components make up the anesthetic machine?
- compressed gas supply
- anesthetic vaporizer
- breathing circuit
- scavenger system
what level of oxygenation is necessary to maintain cellular metabolism under anesthesia?
30%
how do you know the flow of compressed gas will stop completely?
when the valve stem is turned completely clockwise
what safety issues do we associate with compressed gas?
combustibility
yoke attachment - must be attached properly
high pressure release
proper storage
what does the tank pressure gauge do?
indicates the pressure of gas remaining in a compressed gas cylinder - measured in psi
what does the pressure reducing valve do? is it okay to adjust?
reduces outgoing pressure to a constant usable level to 40-40 psi
NEVER touch the pressure reducing valve
is 40-50 psi a safe level for a patient to receive oxygen?
NO must be further reduced by the flowmeter to be safe for patient
what does the line pressure gauge do?
indicates pressure in the gas line between the pressure-reducing valve and flowmeter
what should the line pressure gauge read if the tank is open?
40-50psi
what does the flowmeter do?
indicates the gas flow expressed in L/min
reduces pressure of gas to 15 psi
what does the oxygen flush valve do?
delivers a short, large burst of pure oxygen directly into the rebreathing circuit/common gas outlet
why should you NEVER touch the oxygen flush while your patient is attached?
the flush valve bypasses the vaporizer and flowmeter so the pressure will KILL YOUR PATIENT
why would you use your oxygen flush valve?
leak test
what does the vaporizer do?
converts liquid anesthetic to a gaseous state
where does the mixture of oxygen and inhalant anesthesia go to be delivered to the breathing circuit?
vaporizer outlet port
what is the mixture of oxygen and anesthetic gas called?
fresh gas
what are the induction and maintenance rates for isoflurane?
induction: 3-5%
maintenance: 1.5-2.5%
how might multimodal therapy effect the induction and maintenance rates of your iso?
multimodal decreases the rates as you will need less of each drug
what does the breathing circuit do?
carries anesthetic gas and oxygen from the fresh gas inlet to the patient
conveys expired gases away from the patient
what are the different types of breathing circuits?
rebreathing
nonrebreathing
what type of patient would you use a rebreathing circuit for?
a patient >7 kg
all but very small
t/f - with a rebreathing system exhaled air will not be inhaled again
false - a rebreathing system removes carbon dioxide from exhaled air and it is inhaled again with added oxygen and anesthetic
what type of patient would you use a non-rebreathing circuit for?
the little guys! <7 kg
where does the fresh gas that reaches the patient come from in a non-rebreathing system?
directly from the vaporizer
do you need a CO2 absorber cannister for non-rebreathing? why/why not?
no - none of the exhaled air will be reinhaled by the patient
is it easier to control anesthetic depth with a rebreathing or non-rebreathing circuit?
non-rebreathing as they are not rebreathing anything - adjustments made ot the flowmeter/vaporizer will affect your patient quicker
which system has a high gas volume, rebreathing or non-rebreathing?
non-rebreathing
what is dead space?
gas that is inspired at every breath but does not participate in gas exchange
why would we want to reduce dead space in our surgical patients?
to ensure the maximum amount of air reaches the alveoli
what is included in the animal’s dead space?
mouth to alveoli
what is the mechanical dead space?
animal’s mouth to the machine
what can cause resistance?
valves
abosrber cannister
hose length/diameter
would a smaller hose diameter increase or decrease resistance?
increase
what might happen if you let your tubes just hang off of the table while the patient is intubated?
you may cause circuit drag which can lead to extubation of the patient
what do the unidirectional valves do?
control the direction of gas flow
how can unidirectional valves assist in intubation?
can look at the valves to see if ETT is in the trachea - if it was placed wrong the valves will not flutter with inspiration and expiration
what does the pop-off valve do?
allows excess carrier and anesthetic gases to exit the breathing circuit and enter the scavenge system
prevents excessive pressure or volume of gases in the circuit
when are the ONLY times you can use your pop-off?
manual ventilation
leak test
what will happen if you forget to open the pop-off after manual ventilation and your patient is still attached?
they will die - too much pressure for the patient to breathe out
what are some reasons to manually ventilate your patient?
prevent atelectasis (ventilate every 5-10min)
force fresh gas into alveoli to normalize gas exchange
normalize resp rate - make sure they are getting enough gas
when patient is apneic to prevent them from waking up (they are holding their breath so not receiving any gas)
do you use the pressure manometer in both non-rebreathing and rebreathing systems?
no - only specific for rebreathing
what does the pressure manometer do?
indicates pressure of gases WITHIN the breathing circuit
what units are used for the pressure manometer?
cmH20
mmHg
kPa
what level do you not want to exceed on the pressure manometer when manually ventilating?
20cmH20
what does an air intake valve do? do all machines have one?
admits room air into the circuit if there is presence of negative pressure in the circuit (collapsed reservoir bag)
not all machines have this function
what does a universal control arm contain?
pop-off valve pressure manometer scavenger attachment reservoir bag attachment bain attachment
what are the 3 types of scavenging systems we discussed?
passive
active
activated charcoal
how does a passive scavenge work?
uses the expiratory effort of the patient - no active suction
how does an active scavenge work?
suction created by vacuum/fan - need to monitor reservoir bag to ensure there isn’t a vacuum created there
how does an activated charcoal canister work?
used only when no active or passive system available - can be portable with use of an E-tank
what system would you use an F circuit with?
rebreathing
what is the benefit of coaxial tubing?
allows expired air to warm the inspired air
maintains humidity
prevents heat loss
what system would you use with a coaxial bain?
non-rebreathing
what system is used for an aryes t-piece?
non-rebreathing
how do you know what size reservoir bag to use?
tidal volume x 6
tidal volume is 10-20 ml/kg
what is the minimum flow rate? why?
500ml
vaporizer is not guaranteed under 500ml
how do you calculate flow rate for a mask?
30 x tidal volume
what is the flow rate for a chamber?
5 L/min
what is the induction flow rate for a rebreathing system?
50-100 ml/kg/min
what is the maintenance flow rate for a rebreathing system?
20-40 ml/kg/min
what is the maintenance flow rate for a non-rebreathing system?
200-300 ml/kg/min
what is an anesthetic agent?
any drug used to induce a loss of sensation with or without consciousness
what is an adjunct?
a drug that is not a true anesthetic - it is used during anesthesia to produce other desired effects such as sedation, muscle relaxation, analgesia REVERSAL neuromuscular blockade or parasympathetic blockage
is it ethical to use inhalant anesthetics on their own?
no - they provide no pain control
what is vapor pressure?
the tendency of an inhalation anesthetic to v aporize to its gaseous state
what are volatile agents?
halogenated compounds - soflurane, sevoflurane, etc.
what is the blood-gas partition coefficient?
the measure of the solubility of an inhalation anesthetic in blood as compared to alveolar gas (air)
indicates the speed of induction and recovery for an inhalant anesthetic
what would you expect with a low blood-gas partition coefficient?
faster expected induction and recovery
inhalant tends to remain in gas phase
agent is more soluble in alveolar gas than in blood at equilibrium
agent is less soluble in blood
do you want a high blood-gas partition coefficient or a low blood-gas partition coefficient?
low
t/f - with a low blood-gas partition coefficient there will be a steep diffusion gradient between alveoli and tissues
true
what does MAC stand for?
minimum alveolar concentration
what is minimum alveolar concentration?
the potency of a drug
the lower the MAC the more potent the anesthetic and lower vaporizer setting
what patient specifics can alter MAC?
age metabolic activity body temperature disease stress pregnancy other drugs etc
what do agonists do?
bind to and stimulate target tissue
most anesthetic agents and adjuncts
what do antagonists do?
bind to target tissue without stimulating
reversal agents
what common drug class falls under partial agonists and agonist-antagonists?
opioids
what do partial agonists do to pure agonists?
block
what are the step by step instructions for intubating dogs and cats?
preoxygenate for 3 min with mask or flow by oxygen
administer the IV induction to effect
position your patient in sternal recumbency
assess depth of anesthesia (muscle tone before jaw tone - prevents bites)
where should you place your laryngoscope in the throat of your feline patient?
tip of laryngoscope just rostral to the epiglottis and pressed down
what special consideration needs to be made for cats in regards to intubation?
laryngospasm
how do you inflate the cuff?
inflate with a syringe in 0.5 ml increments until no leak is heard
what is referred to as the “fourth vital sign”
pain
what is a nociceptor?
a sensory neuron that responds to damaging or possibly damaging stimuli by sending possible threat signals to the spinal cord and brain
what is the pain pathway?
transduction
transmission
modulation
perception
what are the consequences of untreated pain?
catabolism and wasting
immune system suppression
inflammation and delayed wound healing with stress secondary to pain
anesthetic risk and increased anesthesia doses
what is primary hyperalgesia?
peripheral hypersensitivity
what is secondary hyperalgesia?
CNS hypersensitivity or windup
what physiological changes can be caused by pain?
catabolic state and wasting
sympathetic stimulation leading to cardiac arrhythmias
what is preemptive analgesia?
administration of pain medication before the pain occurs
should opioids be used on their own?
not often - can cause excitable wake up
what gastrointestinal effects will you see with opioid use?
initial increased motility (nausea, vomiting, defecation) followed by a slow down in motility (ileus, colic, constipation)
what are the common opioids?
morphine oxymorphone hydromorphone methadone fentanyl butorphenol
what kind of pain is morphine used for?
moderate to severe visceral and somatic pain
t/f - morphine can cause excitement and dysphoria in horses and cats
true
what ocular changes might you see with morphine administration in dogs and cats?
dogs - miosis
cats - mydriasis
t/f - oxymorphone has a shorter duration of effect than morphine
false - oxymorphone has a longer duration of effect
what special characteristic does butorphanol have?
can be used to reverse effects of hydromorphone, morphine, fentanyl
is butorphanol sufficient analgesic for surgical pain?
no
t/f - buprenorphine is used for moderate to severe pain
false - buprenorphine is used for mild to moderate pain
what are potential adverse reactions associated with opioids postop?
respiratory depression bradycardia excitement apprehension hypersalivation mydriases excessive sedation panting increased sensitivity to sound urinary retention gastrointestinal effects
what are steroidal anti-inflammatory drugs?
glucocorticoids
what are the short-acting glucocorticoids
hydrocortisones
intermediate acting glucocorticoids?
prednisone, prednisolone
long acting glucocorticoids?
dexamethasone (lots of side effects)
what conditions can occur with overuse of glucocorticoids?
cushing’s disease
diabetes mellitus
heart failure
what patient should never receive NSAIDs?
patients on steroids!
what is gabapentin useful for?
chronic pain in dogs and cats unresponsive to NSAIDs x
what is a good combination of drugs for animals with arthritis and liver/kidney disease?
gabapentin, tramadol, buprenorphine
what added benefits are seen when lidocaine/epinephrine are administered together?
local vasoconstriction producing a reduction in bleeding and longer duration of action
what happens to a local anesthetic near inflammation or infection?
effectiveness is decreased
where does an infraorbital block effect the mouth?
upper lip and skin of upper lip
inferior alveolar block?
lower jaw teeth of specific cside with buccal and labial mucosa, skin of lower lip
mental block?
mandibular incisors on the side of the block
maxillary block?
maxilla and maxillary teeth of side that is blocked, roof of nasal cavity, skin of lateral part of nose
what are the four dental blocks?
infraorbital
inferior alveolar
mental
maxillary
what are the vital signs?
homeostatic mechanisms response to anesthesia heart rate heart rhythm respiratory rate and depth mucous membrane colour capillary refill time pulse strength blood pressure body temperature
what will the patient’s reflexes look like if they are at a light depth of anesthesia?
eye position - central/rotated pupil size - normal pupil response - positive to light muscle tone - good reflex response - poor swallowing/others present but reduced
what will the patient look like at a moderate plane of anesthesia?
eye position - ventrally rotated pupil size - slightly dilated pupil response - sluggish muscle tone - relaxed reflex response - corneal present w/ others absent
what will a patient look like at a deep plane of anesthesia?
eye position - central pupil size - moderately dilated pupil response - sluggish/absent muscle tone - greatly reduced reflex response - all diminished or absent
what is the palpebral reflex?
the blink reflex in response to a light touch at the medial or lateral canthus
light - present
medium - lost
what is the corneal reflex?
retraction of eyeball within orbit and/or a blink in response to corneal stimulation
light - present
medium - present
deep or excessive - lost
what is the pedal reflex?
check by firmly pinching digit - observe if animal retracts leg/paw
light - present
medium - lost
what is the PLR?
papillary light reflex - shine a light into the eye, both pupils should constrict even though light is only shining in one
light - present
medium - present
deep - lost
what is the dazzle reflex?
blink response to bright light shone on retinas
very early - lost
how many stages of anesthesia are there? which has multiple planes?
there are four stages
stage three is divided into four planes
what is stage 1 anesthesia?
period of voluntary movement, patient begins to lose consciousness
stage ends with loss of ability to stand and recumbency
what is stage 2 anesthesia?
period of involuntary movement aka excitement stage
actions are not under conscious control
stage ends with muscle relaxation, decreased resp rate and decreased reflex activity
what is stage 3 anesthesia?
period of surgical anesthesia
divided into four separate planes
what is stage 3 plane 1?
not adequate for surgery
eyeballs begin to rotate
ETT can be passed and connected
reflexes present but decreased
what is stage 3 plane 2?
suitable depth for most procedures BP and HR slightly decreased relaxed muscle tone pedal and swallowing reflexes absent ventromedial eye position PLR sluggish
what is stage 3 plane 3?
deep anesthesia
too deep ofr most procedures
central eyeballs
reflexes totally absent
what should you do if your patient is too deep?
manual ventilation
decrease ISO
if becomes too light add a local or opioid
what happens at stage 3 plane 4?
early anesthetic overdose abdominal breathing fully dilated pupils marked cardiovascular depression flaccid muscle tone all reflexes absent EMERGENCY!!
what causes bradycardia?
depressant effect of most anesthetics
alpha2s and opioids
excessive anesthetic depth
adverse effect of drugs
what causes tachycardia?
anticholinergics and cycloheximines inadequate anesthetic depth pain hypotension blood loss/shock hypoxemia and hypercapnia (high CO2 levels)
what does a first degree A-V heart block look like?
prolonged P-R interval
what does a second degree A-V heart block look like?
occasional missing QRS complexes
what does a third degree A-V heart block look like?
randomly irregular P-R intervals
supraventricular premature complexes?
one more normal QRS complexes closely following the previous QRS complex
what is the absolute minimum MAP you should have?
60
what is MAP the best indicator of?
tissue perfusion
what is osciollometric blood pressure monitoring?
cuff inflated over artery
MAP is most accurate this way
what is the doppler blood pressure monitor?
detects blood flow by emitting ultrasound signal that hits blood in the artery
sphygmomanometer inflates cuff until above when pulse is no longer audible
slowly decrease pressure in cuff - first time you hear pulse is systolic BP
what is PaO2?
partial pressure
norm - 80-120 mmHg
what is SaO2
percent oxygen saturation
norm - >95%
what kind of relationship do partial pressure and oxygen saturation share?
non linear direct relationship
as one decreases so does the other but not at the same rate
which decreases faster, partial pressure or oxygen saturation?
partial pressure
what can low PaO2 and SaO2 indicate during anesthesia?
hypoxemia
need for oxygen supplementation or assisted ventilation
what does a pulse oximeter do?
measures the saturation of hemoglobin and the HR
what is a normal pulse ox reading?
> 95%
hypoxemic - <90-95%
therapy required @ <90%
medical emergency @ <85% for more than 30 seconds
what are the two different kinds of pulse oximeter probes?
transmission - clothespin configuration
refelective - placed in esophagus or rectum
