Anesthesia Flashcards
What is general anesthesia?
Unconsciousness produced by a reversible and controlled depression of the CNS
What are three things you should consider in your patient assessment, outside of your physical exam findings?
Signalment, procedure to be performed, pre-existing diseases
What are the big four in terms of pre-anesthetic bloodwork?
PCV, TP, glucose, and BUN/Azo
When are ECGs more readily considered for pre-anesthetic workups?
When patients are 7 years of age and older
What can you do to quantify the amount of physiological reserve that a patient possesses at the time at which they are assessed for a surgical procedure?
Evaluate their ASA physical status
A patient is given an ASA I status, what does this mean?
Normal healthy patient, elective procedure
A patient is given an ASA IIIE status, what does this mean?
Mild to moderate systemic disease with clinical signs but under control, emergency procedure
(T/F) For an animal with pre-existing cardiovascular disease, fluid administration must be decreased.
True
What should be monitored for maintaining good renal blood flow when a patient has pre-existing renal disease?
MAP
What type of drugs increase urine production?
Alpha 2 agonists
What is an anesthesia drug that is excreted unchanged in the urine of cats?
Ketamine
What should be avoided in an animal with an intracranial mass that is innately increasing ICP?
Further increases
What can be done to avoid further increasing the ICP of a patient with an intracranial mass?
Decrease fluid rate, avoid hypoventilation, avoid drugs that increase ICP, use drugs that decrease ICP
What drug should be avoided in animals with a history of seizures who are undergoing anesthesia?
Ketamine
What class of drug are atropine and glycopyrrolate?
Anticholinergics
What class of drug are acepromazine, benzodiazepines, and alpha 2 agonists?
Tranquilizers/sedatives
What is the mechanism of action for anticholinergic drugs?
Competitive antagonist of acetylcholine at the muscarinic cholinergic receptors
Is the mechanism of action for anticholinergic drugs reversible?
Yes
Listed below are different parts of the body or body processes, give the effect atropine has on them.
- Heart rate
- Heart
- Respiratory
- Eyes
- GI tract
- Heart rate (Increase)
- Heart (Treatment for 2o AV block)
- Respiratory (Bronchodilation)
- Eyes (Mydriasis)
- GI tract (Stasis)
(T/F) Atropine crosses both the blood brain barrier and the placenta.
True
Does glycopyrrolate, which has similar effects as atropine, cross the blood brain barrier or placenta?
No
Compared to atropine, glycopyrrolate has a _________ (shorter/longer) onset and duration of action.
Longer
Anticholinergics are used to decrease both respiratory secretions and salivation as well as prevent/treat what abnormality of the heart?
Bradycardia
When are anticholinergics contraindicated in terms of the effect it has on the heart?
When a patient has pre-existing tachycardia
Why are anticholinergics contraindicated in horses?
Can cause colic, still used in emergencies
What two chemicals does acepromazine block as its main mode of action?
Dopamine and serotonin
What type of receptors does acepromazine block?
Alpha 1 receptors
Acepromazine causes vasodilation by depression of vasomotor reflexes, blockage of peripheral alpha 1 adrenergic receptors, and causing direct relaxation of vascular smooth muscle, what side effect may it cause?
Hypotension
Acepromazine can cause reflex tachycardia, what does the tachycardia result from?
Results from the vasodilation, heart rate increases to keep cardiac output at a normal level
Acepromazine _________ (increases/decreases) myocardial sensitization to stimuli that would increase heart rhythm.
Decreases
What two CBC values does acepromazine affect?
Decreases PCV and TP
Acepromazine is an opioid ____________ (synergist/antagonist).
Synergist
(T/F) Acepromazine provides some analgesia to the patient.
F
Is acepromazine reversible?
No
What effect do benzodiazepines have on GABA receptors? (
ncreases their affinity for GABA and increases the frequency at which the channel opens
Overall, benzodiazepines _____________ (inhibit/potentiate) the inhibitory effects of GABA.
Potentiate
(T/F) The addition of 40% propylene glycol in diazepam solutions makes SQ and IM good routes of administration.
F, makes them bad routes of adm
(T/F) Diazepam is an anxiolytic.
True
Why is diazepam best for debilitated, old animals or foals < 1 month of age?
May cause paradoxical excitement in animals outside of those parameters, very reliable sedation for the parameters in the question
Which benzodiazepine is only used in a 1:1 mixture with tiletamine?
Zolazepam
What is the main advantage of midazolam?
Can be given SQ
What is the expensive, short acting, competitive antagonist for benzodiazepine drugs?
Flumazenil
What advantage do benzodiazepines have over acepromazine in terms of reversibility?
Reversible whereas acepromazine is not
What is the mechanism of action for alpha 2 receptor agonist drugs?
Binds to the presynaptic alpha 2 receptor → decreased release of norepinephrine
What effect does alpha-2 receptor agonists have on heart rate?
Causes bradycardia and 2o AV blocks
Is the biphasic effect that alpha-2 receptor agonists have on blood pressure (initial hypertension with subsequent hypotension) constant?
No, some patients will only have the initial hypertension while some will only have hypotension and then some will have the whole effect of increased hypertension with subsequent hypotension
What two things do alpha 2 receptor agonists decrease in relation to the respiratory system?
Decrease respiratory rate and tidal volume
Why might a pulse oximeter reading be low on a patient that was given alpha-2 receptor agonists?
Peripheral venous desaturation due to the peripheral vasoconstriction these drugs can cause
Do alpha-2 receptor agonists provide analgesia to the patient?
Yes
Besides the cardiorespiratory depression, what are two other disadvantages of using alpha-2 receptor agonists?
Causes emesis in cats and hyperglycemia, there are others but these were the two listed in the main disadvantages list
What is one of the biggest reasons why patients are premedicated prior to induction?
Decreases anesthetic requirements for both induction and maintenance
What effect does propofol have on the opening of chloride channels?
Increases the duration Cl channels are open
What is the result of the effect propofol has on chloride channels?
Hyperpolarization
Propofol causes ________ (hypo/hyper)tension.
Hypotension
Propofol __________ (decreases/increases) intracranial pressure and cerebral blood flow.
Decreases
Propofol causes a refractory __________ (increase/decrease) in heart rate.
Increase, in response to the vasodilation and possible hypotension
Propofol is a profound respiratory depressant and causes administration rate and dose-dependent apnea, what sign might be observed?
Cyanosis
(T/F) Multiple doses of propofol administered to a cat may cause Heinz body anemia.
True
Where is propofol rapidly redistributed to?
Vessel rich groups/organs such as the heart, kidneys, etc.
Where is propofol oxidatively metabolized?
Liver
Does metabolism of propofol rely entirely on the liver?
No, there is extrahepatic metabolism of propofol
Where is propofol excreted?
Kidney
Besides its cardiorespiratory depression, what are the disadvantages to using propofol?
Short shelf life and promotes bacterial growth, no analgesia, and myoclonus can occur
What is added to propofol 28 that makes it last 28 days after opening?
Benzyl alcohol
Can propofol 28 be used in feline patients?
Yes, benzyl alcohol may be toxic to cats but at repeated dosing, a single dose is okay
What is a disadvantage of propofol 28 that propofol does not have?
Cannot be given as a constant rate infusion
Why is etomidate painful on injection and can cause hemolysis at the site of injection?
Due to the solution base being propylene glycol
The enhancement of the effect of GABA is an ________ (direct/indirect) effect of etomidate while the evocation of chloride currents in the absence of GABA is a __________ (direct/indirect) effect.
Enhancement of GABA - indirect, evocation of chloride - direct
Etomidate __________ (increases/decreases) cerebral blood flow, intracranial pressure, and cerebral metabolic rate.
Decreases
What is etomidate the drug of choice for in terms of its cardiovascular effects?
Has minimal cardiovascular effects, drug of choice for significant cardiovascular diseased patients and hemodynamically unstable patients
What does etomidate decrease the synthesis of 3-4 hours after a single dose and of which the clinical significance is unknown?
Cortisol
What negative effect does etomidate have that is apparent upon induction, primarily securing an airway?
Nausea, retching
What results in the high osmolality of etomidate?
Hemolysis and hematuria
What does ketamine cause a dissociation between?
Thalamocortical and limbic systems
Does ketamine provide analgesia?
Yes
What is the mechanism of action for ketamine?
Noncompetitive antagonist at NMDA receptor
Ketamine is highly lipid soluble so it has a ________ (fast/slow) onset of action.
Fast
(T/F) Ketamine may induce epileptiform EEG activity
True
Ketamine __________ (increases/decreases) intracranial pressure, metabolic rate, and blood pressure.
Increases
Ketamine _________ (increases/decreases) heart rate, cardiac output, and myocardial oxygen requirements.
Increases
Which branch of the CNS does ketamine stimulate?
Sympathetic NS
Ketamine causes ___________ (significant/no significant) respiratory depression but may __________ (increase/decrease) respiratory rate and tidal volume while ____________ (increasing/decreasing) tracheal-bronchiol secretions and salivation.
No significant respiratory depression, decreases respiratory rate and tidal volume, increases tracheal-bronchial secretions and salivation
What can be used to prevent the hallucinations and delirium that can be caused by ketamine?
Sedatives/opioids
Ketamine can cross the placenta and cause what in puppies?
Neurologic depression
Where is ketamine metabolized and excreted?
Metabolized in the liver and excreted by the kidneys
Tiletamine is only available in a 1:1 solution with what other drug?
Zolazepam
What is the synthetic neuroactive steroid that enhances agonist binding to GABA receptors and has a similar molecular structure to progesterone?
Alfaxalone
Alfaxalone lacks what negative effect that allows veterinarians to use it off-label in IM and SQ routes?
Does not cause perivascular damage
Is alfaxalone safe for C-sections?
Yes, does cross placenta but has no effect on the fetuses
Does alfaxalone provide analgesia?
No
What are the benefits to administering a propofol-ketamine mixture?
Decreases side effects → cardiovascular effects are opposites so should neutralize in theory and less cardiorespiratory depression, lower dose of each drug, can be mixed in same syringe
When might chemical restraint of a patient be indicated?
For diagnostic procedures, minor surgical procedures, anesthetic machine not available, cost concerns, inhalant anesthesia not possible, very aggressive patients
What are some advantages to chemically restraining an animal?
No room contamination, anesthetic machine not needed, potentially reversible
What are some disadvantages to chemically restraining an animal?
Can be too much or not enough, prolonged recovery, no control of airway, and monitoring is overlooked
When is field anesthesia appropriate in large animal patients?
For simple procedures and healthy patients
What administration is ideal for chemical restraint in large animals?
Intravenous
In what two ways can chemical restraint be maintained?
Repeated boluses or constant rate infusion
Acepromazine use in large animals usually provides _________ (strong/mild/weak) sedation and ________ (good/weak/no) analgesia.
Weak, no
What two classes of drugs is acepromazine an adjuvant for?
Opioids and alpha-2 agonists
Why should acepromazine be used carefully in stallions?
Can lead to priapism
Acepromazine has a ________ (short/long) onset.
Long
Administration of what along with alpha 2 agonists decreases a patient’s responsiveness and makes sedation more effective?
Opioids
Do alpha-2 agonists provide analgesia?
Yes
Alpha-2 agonists cause __________ (brady/tachycardia) and ___________ (hyper/hypotension).
Bradycardia and hypertension
Alpha-2 agonists can cause ataxia in large animal patients but it is dependent on what?
Dose
Which of the alpha-2 agonists (xylazine, detomidine, and romifidine) causes less ataxia?
Romifidine
Which of the alpha-2 agonists is used more commonly for standing chemical restraint in horses?
Detomidine
What is romifidine used more commonly for and in what species?
Premed in bovines
Ruminant doses of alpha-2 agonists are how many times less than horses?
5-10x
What problems can xylazine cause when administered to sheep?
Pulmonary edema and hypoxemia
Tolazoline, yohimbine, or atipamezole have what relationship to alpha-2 agonists?
Reversal agents
Opioids provide good __________ (analgesia/sedation) with minimal ___________ (analgesia/sedation).
Analgesia, sedation
Opioids __________ (increase/decrease) the ataxia caused by alpha-2 agonists?
Increase
What can opioids cause when given to an unsedated horse?
Excitement and/or increased locomotor activity
Opioids __________ (decrease/increase) GI motility when given in high doses or for prolonged infusions.
Decrease
How long does morphine provide analgesia when given epidurally?
8-20 hours
What is used to reverse opioids?
Naloxone or naltrexone
In which species are benzodiazepines (diazepam and midazolam) not used for sedation because it causes excitement?
Horses, specifically adult horses
Although benzodiazepines provide very good sedation in ruminants, they provide no what?
Analgesia
Which of the benzodiazepines (diazepam/midazolam) can be given IM or IV, while the other is only IV?
Midazolam can be given IV or IM, diazepam IV only
What drug is the reversal agent for benzodiazepines?
Flumazenil
Which drug is a central muscle relaxant that provides no analgesia, has minimal cardiorespiratory effects, and is mostly used to improve sedation and make anesthetic induction smooth?
Guaifenesin
What drugs are used in a ‘triple dip’?
Ketamine, xylazine, and guaifenesin
What drug is left out of the triple drip, deemed a ‘double drip’, for ruminant patients to minimize excessive sedation?
Xylazine
Guaifenesin is an irritant to perivascular tissue and causes hemolysis at injection sites, what can this result in?
Necrosis
Does ketamine provide analgesia in addition to sedation?
Yes
Can ketamine be given IV, IM, or SQ?
Yes, all of the above
Ketamine increases sympathetic tone which means it has what effect on heart rate, blood pressure, and cardiac output?
Increases those three things
Can ketamine be reversed?
No
What makes up the triad of anesthesia?
Muscle relaxation, analgesia, and unconsciousness
What two characteristics does a drug need to have to have a rapid onset of action?
Fat soluble and crosses the blood-brain-barrier
What are some benefits of injectable anesthesia?
Little equipment needed, easy to administer, rapid and smooth induction, relatively cheap, and no environmental pollution
What are some disadvantages of injectable anesthesia?
Retrieval not possible, patient needs to be weighed accurately, high doses needed when given alone, potential for human abuse, and risk of self administration
Why can obese patients take longer to wake up from anesthesia and may have residual effects that last longer than a not obese patient?
Fat stores lipophilic drugs, of which some anesthetics are, so they will have more storage of the drug than not obese patients
What are the beginning and end of stage 1 of anesthesia?
Drug administration to loss of consciousness
(T/F) Excited animals may voluntarily hold their breath for short periods of time during stage 1 of anesthesia
True
The release of what chemical during stage 1 of anesthesia causes a strong, rapid heartbeat and pupillary dilation?
Epinephrine
What are the beginning and end of stage II of anesthesia?
Loss of consciousness to onset of a regular breathing pattern
Are animals still reactive to external stimuli during stage II of anesthesia?
Yes
What stage of anesthesia is the stage in which surgery can be performed?
Stage III
Patients are considered to be in light plane anesthesia until when?
Until eyeball movement ceases
Which reflex should always be present in a live animal?
Corneal reflex
What happens to the laryngeal and palpebral reflexes in a medium plane of anesthesia?
Laryngeal reflex - abolished, palpebral - sluggish
A patient who has centered and dilated pupils, a weak corneal reflex, profound muscle relaxation, and increased respiration with diaphragmatic breathing would be considered to be in what plane of anesthesia?
Deep plane
With what stage of anesthesia is extreme CNS depression associated?
Stage IV
Withdrawal of the anesthetic and artificial respiration must be initiated before what event to be able to reverse a patient in anesthesia stage IV?
Needs to be initiated before myocardial collapse
When should critical patients be instrumented in the anesthetic induction sequence and why?
The beginning, to allow for continuous monitoring throughout the induction process
What are anesthetized patients at a higher risk for that support the idea of securing an airway?
Hypoxia, upper airway obstruction, respiratory depression
What does securing an airway and using it as a route for inhalant anesthetic minimize?
Environmental and personnel contamination
What is the purpose of preoxygenation?
Creation of an oxygen reservoir in the alveoli
What are face masks used for in terms of oxygenation?
Preoxygenation or supplemental oxygen administration
What type of ET tube would you use for a procedure that involves extreme flexion of the head/neck and/or compression of the trachea?
Reinforced/guarded ET tube
What two species are supraglottic airway devices, V-GELs specifically for vet med, made for?
Cats and rabbits
ou just intubated a patient and are confirming the ET tube placement, what might you look for?
Sustained EtCO2, condensation in the ET tube, chest excursion
(T/F) The tie you use to secure the ET tube should be tight on the head and gentle on the tube.
F, other way around
