Anesthesia Final (new material)
Terms in this set (304)
What are your biggest concerns with anesthetizing large ruminants?
their size and behavior and logistically planning how to maneuver them where they need to be while keeping them asleep
What are your biggest concerns with anesthetizing small ruminants?
they can look completely normal but have severe pneumonia, GI disease, and/or lice
What are your biggest concerns with anesthetizing swine?
they are difficult to achieve venous access or tracheal intubation on , and their fatty tissue can trap drugs and prevent their action from occurring at the expected time
How long should large ruminants be fasted prior to anesthesia?
48 hrs food, 24 hrs water
How long should small ruminants be fasted prior to anesthesia?
24 hrs food/water
How long should swine be fasted prior to anesthesia?
12 hrs food, 6-8 hrs water
Why is positioning so important for large ruminants under anesthesia?
they are HEAVY and must be able to constantly drip saliva and regurgitate
Explain proper positioning in large ruminants under anesthesia
the up limb should always be propped up to prevent crushing the brachial plexus between the pectorals and triceps; poll should be the tallest point of the head/neck
Why is positioning so important for small ruminants under anesthesia?
they must be able to constantly drip saliva and regurgitate, so the poll should always be the tallest point of the head/neck
What are concerns with using anticholinergics (atropine, glycopyrrolate) in ruminants? Use?
they are good for increasing the HR BUT cause secretions to become thick and thus may lead to bloat; only used to treat bradycardia
What are concerns with using alpha-2 agonists in ruminants?
they are VERY sensitive to these; in small ruminants they can cause deadly pulmonary edema
Why are telazol, propofol, and alfaxalone rarely used in large ruminants?
WAY too expensive in adult animals
What are concerns with using inhalants in ruminants?
the cost, cardiovascular effects, and the special equipment needed for large ruminants
Where should you inject pigs IM? IV?
right behind the ear (1.5 in 18 G needle); auricular vein (use a rubber band to make it stand up)
What is unique about monitoring large ruminants under anesthesia?
they are normally hypertensive (120/80) but should be maintained at ~100 and their ionized calcium is lower than in other species
What is unique about monitoring small ruminants under anesthesia?
their ocular reflexes are unreliable
Why is intubation in large ruminants challenging?
there is often no laryngoscope large enough to reach the larynx; you palpate to ID, put a stomach tube between the arytenoids, and insert the trach tube over it
Why is intubation in small ruminants challenging?
they must be WELL sedated and are prone to laryngospasm so lidocaine should be used; you MUST visualize the arytenoids during intubation (mouth doesn't open wide- straight line from shoulder to tongue!)
Why is intubation in swine challenging?
must go 3 directions in 1 pass to get past the laryngeal diverticulum and middle laryngeal ventricle, which is very friable and bloody. The longer it takes, the more saliva and blood accumulate and the less you can see. There is also risk of causing a pneumothorax when using a guiding catheter.
What are concerns for recovery in large ruminants?
they should be in sternal, you should hear eructation and they should be able to lick their nostril before the tube is removed, the cuff should be partially inflated on removal, and their head should be kept out of the shavings in the stall
What are concerns for recovery in swine?
it must be quiet and well-ventilated because they are so fat they will overheat easily; they must be separated from other pigs or they will be killed
What is malignant hyperthermia? Cause?
inherited disease resulting in abnormal release of calcium in skeletal muscles, causing muscle contraction, hyperthermia, increased CO2 production (metabolic acidosis). It can be triggered by inhalants, drugs, or stress
How is malignant hyperthermia treated?
discontinuing the inhalant and switching machines, cooling the animal rapidly using IV fluids, ventilate, oxygenate, and use steroids to correct metabolic acidosis
When using a demand valve to maintain horses oxygenation status post-inhalant anesthesia, what must be monitored?
avoid hypocapnia because it will prevent the animal from breathing on its own and will cause inhalant to be rapidly depleted, causing the animal to wake up quickly. If using 1-way valve, remove it to allow exhalation
What are common drug choices in horses on recovery from inhalant anesthesia?
alpha-2 agonists, ketamine/xylazine combo
What is the concern in deflating the cuff on a horse recovering from anesthesia?
you can no longer use a demand valve to provide oxygen, so you must ensure they are ventilating on their own
What are considerations prior to extubating a horse?
spontaneous ventilation, swallowing, adequate nasal airflow
What is the danger in horses experiencing upper airway obstruction during recovery from anesthesia?
they may collapse and experience pulmonary edema as a result of the obstruction
What nerves are most commonly affected by neuropathy in horses under anesthesia?
facial, radial, femoral
How long does it take horses to recover from neuropathy post-anesthesia?
48 hrs (usually)
What puts a horse at greater risk for femoral nerve neuropathy during anesthesia?
stretching legs for MRI
What is the most common cause of myopathy in horses undergoing anesthesia? How can you distinguish this from neuropathy?
hypotension; myopathy is very painful
How are horses experiencing post-anesthetic colic/ileus treated?
lidocaine to increase motility, monitor gut sounds, administer reversals, give fluids IV
What factors increase risk of post-anesthetic colic/ileus in horses?
anesthesia duration, >10 yrs, arabian, PCV >45%, hyperproteinemia, hyperalbuminemia, anesthesia >2.5 hrs, surgery >3 hrs, resection and anastomosis, lesions of the small intestine
What anesthetic complication is more common in fresians/draft horses?
What are expected electrolyte changes seen with fluid therapy in horses?
calcium, potassium, magnesium
What are results of endotoxemia on the cardiovascular system of the horse?
vasodilation, reduced contractility, inadequate venous return (decreased CO and BP)
Explain the changes that allow you to distinguish poor contractility verses vasodilation
SAP will be more affected by contractility, DAP will be more affected by vasodilation
Explain the pulmonary changes seen with colic in horses.
Distended abdominal contents cause decreased FRC, decreased ventilation/oxygenation due to atelectasis; both result in hypoxemia
What must you balance when using recruitment maneuvers to reduce hypoxemia in a colic horse under anesthesia?
decreased venous return caused by positive pressure
Explain the cause and effect of HYPP in horses.
sodium channels open and fail to close, depolarizing. Then K is released to try to balance this, resulting in hyperkalemia. Muscles try to contract, causing faciculations, then they collapse; can cause cardiopulmonary collapse
What drugs should be avoided in horses with HYPP undergoing anesthesia?
K-penicillin, depolarizing neuromuscular blocking agents, Old stored blood transfusions, K-sparing diuretics, K-containing solutions
Explain voltage gated sodium channels and the effects of local anesthetic son them.
opens when depolarization (trying to cause contraction of muscle due to signaling of a nerve) occurs and Na+ ions flood into the cell; local anesthetics are large molecules that physically block open sodium channels, preventing Na influx
List the sodium channels in the order they are blocked. How many must be blocked to desensitize a nerve?
Ay> Ao>Aa>Ab>C; 3 or more nodes of ranvier
How do you increase the extent and duration of a local block?
inject a small volume, high concentrate solution
What channels are of the most importance in the spinal cord/epidural space? Why?
K channels, Ca channels, and substance P; they are inhibited from binding the dorsal horn by anesthetics, preventing nociception and inhibiting glutaminergic transmission which blocks NMDA/NK depolarization
Blocking what molecules blocks pain?
substance P and glutamine
What is pKa?
Degree of dissociation of your compound; pH at which 1/2 a drug is ionized and 1/2 is non-ionized
If a drug is more ionized, will it be more or less able to cross a membrane?
Relate high pKa, ionization, water solubility, and onset of action.
high pKa= high ionization= increased water solubility= slower onset of action
Relate low pKa, ionization, water solubility, and onset of action.
low pKa= lo ionization= increased lipid solubility= faster onset of action
Explain why bupivavaine is more potent than lidocaine.
bupivacaine is more lipid soluble
List the speed of systemic absorption in the nerves below in order: epidural, sciatic/femoral, brachial plexus, intercostal
intercostal> Epidural> Brachial plexus> Sciatic/femoral
Explain how ion trapping occurs in the placenta.
local anesthetics are weak, basic drugs. They get trapped in their ionized form in more acidic locations because they do not cross membranes well in this form. The fetal pH is lower than maternal pH, so they will accumulate there.
What metabolizes ester local anesthetics? List the drugs in this category.
nonspecific pseudocholinesterases; benzocaine, procaine, tetracaine
What metabolizes amino amide local anesthetics? List the drugs in this category.
CYP450; lidocaine, bupivacaine, mepivacaine
What is the purpose of adding epinephrine to local anesthetics?
vasoconstriction to keep the drugs there and lengthen duration of effect
What is the purpose of adding hyaluronidase to local anesthetics?
improve tissue penetration/shorten onset of action
What is the purpose of adding alpha-2's to local anesthetics?
vasoconstriction, synergistic analgesic effects
What drug may be added to penicillin to increase duration of action?
What local anesthetic commonly causes methemoglobinemia, and is thus avoided in cats/pets?
What local anesthetic is very cardiotoxic if given IV?
bupivacaine, mepivacaine, ropivacaine
What local anesthetic is used commonly in joint injections in horses due to low chondrotoxicity?
What physiologic conditions promote toxicity of local anesthetics accidentally given IV?
hypercapnia, hypoxemia, and acidosis
What is the duration of effect for EMLA cream? nocita?
2 hrs, 72 hrs
What is desensitized with this block? name?
upper dental arcade adjacent to the injection and cranial/rostral on the same side where you inject. Upper lip, nose, soft/hard palates, and dorsal aspect of nasal cavity; infraorbital
What is desensitized with this block? name?
all teeth on that side, including upper lip, nose, soft/hard palates, and dorsal aspect of nasal cavity; maxillary
What block would be appropriate for removal of a canine on the upper arcade of a dog?
maxillary or infraorbital
What is desensitized with this block? name?
all teeth on that side, skin and soft tissue of lower lip, the mandible, rostral 2/3 of the tongue; mandibular nerve block
What is desensitized with this block? name?
rostral mandible, the ipsilateral canine and incisors, upper lip, nose, soft/hard palates, and dorsal aspect of nasal cavity; mental nerve block
What is desensitized by the brachial plexus block?
elbow and distal; radius/ulna
If you have a humeral fracture, would a brachial plexus block be appropriate multimodal analgesia?
no; it desensitizes lower than this
What are challenges to use of the brachial plexus block?
you need U/S or nerve stimulator to accomplish this with any degree of success. Many vessels, arteries, and veins present so use extreme caution
What block is easier and more effective than a brachial plexus block?
What block is appropriate for toe amputation?
RUMM block, forefoot block, brachial plexus block
Where are intercostal nerve blocks placed to provide analgesia for an incision/injury?
along the caudal border of the rib 2-3 rib spaces cranial and caudal to the location (nerve overlap)
What hind-limb nerve blocks are typically used together?
femoral and sciatic
Would a sciatic/femoral nerve block combo be effective for a distal stifle fracture?
Would a sciatic/femoral nerve block combo be effective for a pelvic procedure?
What drugs may be used in epidurals?
lidocaine, bupivacaine, morphine, buprenorphine, oxymorphone (bupivacaine and morphine are most common)
What is the benefit of buprenorphine over morphine in epidurals in large dogs?
does not cause urinary retention, decreasing the risk of bladder rupture
What are methods to confirm your placement in the epidural space?
hanging drop, loss of resistance
What is a complicating factor in confirming placement of your epidural in the correct space?
less obvious pop and lack of consistent negative pressure in small dogs/cats
When are epidurals contraindicated?
Sepsis, coagulopathy, local infection, uncorrected hypovolemia, anatomical abnormalities (basically anything that could cause an abscess or hematoma in the spinal cord don't do it)
Why should you never give an epidural to a hypovolemic patient?
the anesthetic will move up the spinal cord to the area that controls the sympathetic nervous system, blunting its response. This causes hypotension due to vasodilation and prevents venous return (big deal when you don't have much moving in the first place)
When would morphine provide analgesia in a joint?
in inflamed joints, opiate receptors are upregulated and 24 hours of pain control can be achieved with morphine injections
What is the disadvantage of an inverted L block?
only blocks the superficial layers, so incomplete analgesia, risk of toxicity (you're using a lot), increased cost due to
What is the advantage of an inverted L block?
simple, not interfere with ambulation, not interfere with incisional area
How do you know lumbar paravertebral blocks were successful?
poke the skin with a needle, muscle relaxation causing scoliosis especially with the proximal paravertebral
What are the advantages of the lumbar paravertebral blocks?
small dose, wide and uniform area of analgesia and muscle relaxation, absence of local anesthetic at sx site
What are the disadvantages of the proximal paravertebral block?
scoliosis of the spine (closing difficulties), landmarks in obese animals are difficult to see, takes more skill must be careful to avoid major vessels (aorta), might accidentally go epidural (dangerous because the animal may go down)
What are the advantages of the distal paravertebral block over the proximal?
Lack of scoliosis, easier, more consistent, minimal ataxia, not going to hit the aorta
What are the disadvantages of the distal paravertebral block over the proximal?
requires a larger dose, varied efficacy due to anatomical variation
What is the term for stopping movement of a structure?
What are the 4 blocks used to desensitize the area around the equine eye? Which is most common?
*supraorbital, lacrimal, infratrochlear, zygomatic
What nerve must be desensitized to block the area colored in green?
What nerve must be desensitized to block the area colored in blue?
What nerve must be desensitized to block the area colored in yellow?
What nerve must be desensitized to block the area colored in purple?
What blocks are used for enucleation?
What are concerns with the retrobulbar nerve block?
possibility of injecting the optic nerve, potential for oculo-cardiac reflex causing bradycardia
What nerves must be blocked for dehorning in cattle?
cornual branch of the zygomaticotemporal
What nerves must be blocked for dehorning in goats?
cornual branch of the zygomaticotemporal, cornual branch of the infratrochlear
What nerve block is useful for surgical procedures for the tail perineum, anus, rectum, vulva, prepuce, and scrotal skin?
cranial or caudal epidurals
What is the change in risk of anesthetic mortality in patients over the age of 12?
7x (700%) more risk
What are cardiovascular changes that increase the risk of anesthetic complications in geriatric patients?
reduced CO, increased vagal tone, more arrythmias, increased cardiac disease
What are pulmonary changes that increase the risk of anesthetic complications in geriatric patients?
atrophied intercostal muscles, blunted response to hypoxia
What are hepatic changes that increase the risk of anesthetic complications in geriatric patients?
Up to 50% decrease in liver mass, even with normal liver values, meaning they produce less hepatic enzymes. These enzymes deal with glucose, coag factors, proteins (colloidal pressure), and metabolism
What is a combined effect of cardiac and hepatic/renal changes in geriatric patients that increases anesthetic risk?
the liver/kidneys has decreased blood flow due to decreased CO, meaning there is decreased metabolism and decreased excretion of drugs
What are renal changes that increase the risk of anesthetic complications in geriatric patients?
up to 50% decrease in kidney function puts the kidneys at greater risk if faced with anesthetic hypoxia
What are concerns with using anticholinergics (atropine, glycopyrrolate) in geriatric patients?
they become EXTREMELY tachycardic, so a 1/2 dose or less should be used if at all
What are concerns with using acepromazine in geriatric patients?
hypotension, prolonged effects, lack of analgesia, and no reversal available
What are concerns with using benzodiazepines in geriatric patients?
may cause excitement in high-strung animals, but overall good sedation with little CV effect
What are concerns with using alpha-2's in geriatric patients?
they first get hypertensive and HR drops, HR stays low but vasoconstriction goes away and they get hypotensive
What drug classes are best avoided as premeds in geriatric patients?
What induction agents are used for sedation effects in geriatric patients?
propofol, etomidate, alfaxalone
What are considerations for use of propofol as an induction agent in geriatric patients?
it is the most CV depressing, but can be used with multimodal protocols (best to avoid)
What are considerations for use of etomidate as an induction agent in geriatric patients?
very difficult induction, but very CV supportive
What are considerations for use of alfaxalone as an induction agent in geriatric patients?
can be given IM, more CV stable than propofol but less than etomidate
What induction agents are best avoided as sole drugs in geriatric patients, but may be used together?
What are considerations for the response to anesthetics in pediatric patients?
they are very sensitive and have a high metabolic rate, so it may take time to reach the right level of sedation and then the drug is used up really quickly; you MUST maintain their HR to maintain their BP
What are cardiovascular concerns when anesthetizing pediatric patients?
born with small, weak hearts that can only alter contraction 30%, no real fight-or-flight response, may have persistent fetal circulation, often anemic (transition from fetal to adult hemoglobin)
What are renal/hepatic concerns when anesthetizing pediatric patients?
won't have fully functioning enzymes until 8-12 weeks of age
What are respiratory concerns when anesthetizing pediatric patients?
minimal oxygen reserve; very compliant lungs that easily experience atelectasis due to lack of stability to force alveoli open
What are the 2 biggest things to consider when trying to stabilize a pediatric patient?
keep them warm and oxygenated
What cardiovascular changes are expected in pregnant animals?
relative anemia, increased CO (30-35%) to maintain BP which would otherwise decrease due to vasodilation from estrogens/oxytocin
What additional cardiovascular changes are expected in pregnant animals in labor?
greater CO increase to provide the necessary blood flow to the uterus
When anesthetizing a pregnant animal, what cardiovascular concerns should be considered?
we will depress their compensatory responses, which can lead to dangerous decreases in BP and CO
What respiratory changes are expected in pregnant animals?
progesterone causes increased sensitivity to CO2, shifting the curve to the left, oxygen consumption and minute ventilation increase, FRC may decrease due to bronchodilation and pressure of the fetuses on the diaphragm
What additional respiratory changes are expected in pregnant animals in labor?
oxygen consumption will reach its highest point but PaO2 will decrease due to hypoventilation, making them very prone to hypoxemia
When anesthetizing a pregnant animal, what respiratory concerns should be considered?
they MUST be preoxygenated to prevent hypoxic injury to the tissues and fetuses.
What GIT changes are expected in pregnant animals?
progesterone slows GI motility, the LES tone decreases, HCl production increases, and growing fetuses put pressure on everything, increasing risk of regurgitation.
When anesthetizing a pregnant animal, what GIT concerns should be considered?
regurgitation risk in these patients is HIGH so they should be put on antiemetics and drugs to increase gastric emptying
What liver changes are expected in pregnant animals?
total plasma protein concentration may be decreased due to the relative increase in plasma volume
When anesthetizing a pregnant animal, what liver/kidney concerns should be considered?
the decreased plasma proteins may alter how drugs act in circulation, and increased GFR may clear drugs more quickly
Why should a high BUN/CRE be of special concern in pregnant animals?
due to increased GFR during pregnancy, these may be even lower than expected. This means if they are even slightly elevated, they are effectively REALLY high and should be addressed
What kidney changes are expected in pregnant animals?
increase in GFR (60%)
What uterine blood flow changes are expected in pregnant animals?
there is no autoregulation to the uterus, so maintaining blood flow to the fetuses is dependent upon overall perfusion pressure
When anesthetizing a pregnant animal, what uterine concerns should be considered?
anything that could decrease MAP and thus alter perfusion pressure should be avoided, because the uterus has no autoregulation to adjust to changes
Why are inhalants of such concern in pregnant animals?
they cause hypotension, decreasing MAP and thus reducing blood flow to the uterus; also progesterone decreases anesthetic requirements by up to 40%
What factors alter clearance of inhalants in pregnant animals?
progesterone decreases anesthetic requirements by up to 40%, increased GFR and CO will clear drugs more quickly, and plasma protein concentration and pH in the placenta/fetus alter VOD
Why is high-dose oxytocin of such concern in pregnant animals?
Produces vasodilation, which may decrease MAP, and results in myometrial contraction, which may alter myometrial vascular resistance
What drugs are we most concerned about with ion trapping? Why?
local anesthetics and opioids; their pKa is close to physiologic pH, and fetal pH is lower so upon entering the fetus they may change to their ionized form and be unable to pass through the membranes to exit
Explain how drugs get into a fetus.
enter through the placenta, move through the umbilical vein, pass through the fetal liver (processes some drug, but not yet 100% functional) or go to fetal systemic circulation
What is the difference between fetal hemoglobin and adult hemoglobin?
fetal hemoglobin has higher oxygen affinity due to decreased levels of 2,3-DPG; this causes many neonates to be anemic as they transition from one form to the other after birth
Pregnant sheep under ax. PO2: 550, PaCO2: 25, pH: 7.48. (fetal pH: 7.24). Consequences?
The animal is hypocapnic and hypotensive. Hypocapnia produces vasoconstriction, decreasing perfusion of the uterus. The pH difference indicates ion-trapping will occur
What are the goals of ax during pregnancy?
maintain tissue perfusion, cellular function, and oxygenation (CO and O2 content), avoid maternal depression, maximize neonatal vigor and viability
What are risks of regional anesthesia in pregnant animals?
recumbency, unpredictable levels of effect, may produce hypertension due to sympathetic effects; need assistance to control animal movements
What are benefits of regional anesthesia in pregnant animals?
decreases systemic exposition and fetal exposition, decreased risk of aspiration, provides analgesia
Sacrococcygeal and lumbo-sacral blocks are examples of what type of anesthesia?
If you must do non-obstetric surgery in a pregnant patient and you have a choice, when in the pregnancy is it least risky?
What is the most effective vasopressor used to maintain perfusion to the uterus?
What alterations must you make when calculating drugs for pregnant animals?
recognize the fetus is up to 16% of the maternal weight, and take care to dose accordingly
What are expected effects of acepromazine, benzodiazepines, or alpha-2 agonists on pregnant animals?
respiratory depression, sedation, decreased fetal feeding
What anticholinergic and analgesic are best for pregnant animals?
glycopyrrolate- doesn't cross the placenta, has a reversal;
opioids- has reversals
What induction agents are best for pregnant animals
propofol or alfaxalone (alfaxalone better in cats)
What is the expected effect of ketamine on a fetus?
significant respiratory depression
When preparing a mare for c-section, what is the most important thing to remember about sedatives?
they are often necessary but everything should be given in LOW doses
We are doing a c-section on a mare and her MAP is 45 mmHg- what should we do?
check anesthetic depth, bolus fluids, give vasoconstrictors and ionotropes for BP and heart
What are cardiovascular effects of acepromazine?
Produces vasodilation, producing hypotension, decreasing venous return, the preload, and ultimately CO
What are cardiovascular effects of benzodiazepines?
little cardiovascular/respiratory effect
What are cardiovascular effects of alpha 2's?
Good sedation, significant vasoconstriction, increasing afterload, then produce bradycardia
What are cardiovascular effects of opiates?
Produce some respiratory depression and then bradycardia
What are cardiovascular effects of inhalants?
all depress the cardiovascular system by causing vasodilation, negative ionotropic effects, decreased autonomic ability to adapt to changes
What are cardiovascular effects of ketamine?
maintain or increase HR
What are cardiovascular effects of propofol?
produces vasodilation and decreased contractility, decreasing CO, producing low peripheral pressures
What are cardiovascular effects of alfaxalone?
tends to produce tachycardia (especially in dogs), but may also cause vasodilation, decreasing CO
What are cardiovascular effects of etomidate?
Most heart problem dogs are classified as what ASA status?
2 and above; most commonly 3
Why are infusions common anesthetic methods with cardiovascular patients?
they maintain the animal at a constant level of anesthesia compared to boluses
What pathophysiology category do DCM and myocarditis fall into?
What are the goals of anesthesia in patients with myocardial failure?
increase CO, decrease cardiac workload, avoid renal compromise, control arrhythmias, decrease edema
What pathophysiology category do HCM, restrictive cardiomyopathy, pericardial effusion, and constrictive pericardial disease fall into?
What are the goals of anesthesia in patients with diastolic dysfunction?
Increase cardiac filling, increase myocardial perfusion, drain pericardial constriction, control arrhythmias, decrease edema
What pathophysiology category do subaortic stenosis, pulmonary stenosis, systemic hypertension, pulmonary hypertension fall into?
What are the goals of anesthesia in patients with pressure overload?
Relieve stenosis (if possible), maintain myocardial perfusion, avoid edema and arrhythmias
What pathophysiology category do PDA, CVD, VSD, mitral insufficiency, and aortic/tricuspid insufficiency fall into?
What are the goals of anesthesia in patients with volume overload?
Decrease valve regurgitation, +/- support contractility, decrease cardiac workload, increase forward output, decrease edema and arrhythmias
Explain the physiologic effects of ace inhibitors and why we are concerned with them in anesthetized patients.
decrease angiotensin II levels, causing vasodilation to decrease afterload; increased risk of hypotension under ax
Explain the physiologic effects of beta blockers and why we are concerned with them in anesthetized patients.
help with relaxation of the heart decrease HR; produce bradycardia and act as negative ionotropes, decreasing contractility; high risk of bradycardia and decreased contractility
Explain the physiologic effects of pimobendan and why we are concerned with it in anesthetized patients.
positive ionotrope, increasing contraction of the myocardium. It also decreases afterload by causing vasodilation, increased lusitropy; no concerns (it is increasing CO)
Explain the physiologic effects of spironolactone and why we are concerned with it in anesthetized patients.
K sparing diuretic; can produce hyperkalemia and lead to arrythmias
What factors affect the level of regurgitation experienced in cardiovascular patients under anesthesia?
size of the hole, length of each beat, pressure gradient in the heart
Why would you not want to use inhalants on a patient with significant cardiovascular regurgitation?
they will increase afterload which could exacerbate the problem
What are goals in anesthetizing a patient with cardiovascular regurgitation?
smooth induction with little stress, avoid hypoxemia and provide sufficient analgesia
Why not use alpha-2s for premeds in a patient with cardiovascular regurgitation?
they increase afterload and produce vasoconstriction
Why not use phenothiazines for premeds in a patient with cardiovascular regurgitation?
they are long acting
Why not use benzodiazepines for premeds in a patient with cardiovascular regurgitation?
they may produce excitement in many small animals, which we want to avoid in these patients
What is the best choice for premeds in patients with cardiovascular regurgitation? Why?
opioids; provide good analgesia, have mac sparing effect (decreased inhalant)
Why not use high dose opioids for premeds in a patient with cardiovascular regurgitation?
may decrease HR (in low doses, this is your go-to premed in these patients)
Why not use propofol for induction in a patient with cardiovascular regurgitation?
it is a negative ionotrope, so decreases contractility of the heart, and it produces vasodilation
Why not use ketamine for induction in a patient with cardiovascular regurgitation?
can be arrhythmogenic
What are the best choice drugs for induction in a patient with cardiovascular regurgitation?
etomidate and benzodiazepines OR ketamine and benzodiazepines
What fluid rate should not be exceeded in patients with advanced stages of cardiovascular regurgitation?
5 ml/kg/hr crystalloids
What are goals in anesthetizing an animal with subaortic stenosis?
maintain CO, maintain preload, maintain or decrease HR to increase filling time, improving preload. NO stress (increases oxygen consumption and arrhythmias). Contractility is usually not an issue.
Why not use acepromazine for induction in a patient with subaortic stenosis?
causes vasodilation, decreasing preload and CO. This is likely to lead to ischemia
What premed should only be used in cardiac patients that are stable?
What induction agents should only be used in cardiac patients that are stable?
What drugs are most useful in patients with DCM to increase systemic vascular resistance? decrease?
What drugs are most useful in patients with subaortic/pulmonary stenosis to cause vasoconstriction?
What drugs are most useful in patients with HCM to cause vasoconstriction?
What drugs are most useful in cardiovascular patients with hypotension to cause vasoconstriction?
What are concerns with using anticholinergics as premeds in patients with respiratory disease?
decreased vagal tone, bronchodilation, and increased cardiac work
What are concerns with using acepromazine as a premed in patients with respiratory disease?
long acting, pharyngeal relaxation, no reversal; no severe impact on the respiratory system unless in high doses
What are concerns with using alpha-2 agonists as premeds in patients with respiratory disease?
good sedation, upper airway relaxation, reversible
What premed should be avoided in sheep due to the likelihood of causing pulmonary hemorrhage and edema?
What are concerns with using opiates as premeds in patients with respiratory disease?
produce respiratory depression (varies in severity by species), potentiate depression, increased risk of vomiting, reversible
What are concerns with using benzodiazepines as premeds in patients with respiratory disease?
poor sedation in some species (small animal), minimal respiratory effect, reversible
What is apneustic breathing and what anesthetic is known to cause this, and thus should be used carefully in patients with respiratory disease?
What are concerns with using propofol as an anesthetic in patients with respiratory disease?
can cause apnea if given too quickly, causes bronchodilation
What are concerns with using alfaxalone as an anesthetic in patients with respiratory disease?
less respiratory depression than inhalants, and does not accumulate
What are concerns with using etomidate as an anesthetic in patients with respiratory disease?
significant respiratory depression and short acting
Why are anticholinergics useful in brachycephalic patients?
they often have high vagal tone and this can help to decrease it
What is the best choice for premeds in brachycephalic patients?
antiemetics, anticholinergics, low dose opioids, sedatives
What is the best choice for induction in brachycephalic patients?
propofol or alfaxalone
Choose the appropriate anesthetic plan for a brachycephalic dog getting corrective brachycephalic surgery.
1. High-dose Acepromazine, hydromorphone, etomidate, halothane,
2. Methadone, Propofol, sevoflurane, fentanyl CRI
3. Hydromorphone, sevoflurane induction and maintenance
4. Butorphanol, fentanyl, ketamine/midazolam, sevoflurane
Methadone, Propofol, sevoflurane, fentanyl CRI
What drug should not be used with butrophanol due to counteracting actions?
Why is hydromorphone contraindicated in patients with respiratory disease?
it causes panting which increases risk of respiratory collapse
With what type of airway disorder is increased PEEP helpful?
lower airway disease
With mechanical ventilation, what is the target level for PaCO2?
35-50 mmHg; Horses can be up to 60
With mechanical ventilation, what is the target level for pH?
With mechanical ventilation, what is the target level for PaO2?
500 mmHg with 100% O2, 80-120 mmHg with 21% O2
With mechanical ventilation, what is the peak inspiratory pressure??
With mechanical ventilation, what is the target I:E ratio?
With mechanical ventilation, what is the target inspiratory time in smaller animals?
With mechanical ventilation, what is the target inspiratory time in larger animals?
List the pressure and frequency with which "sighs" should be used in animals with lower airway disease during anesthesia.
<30 cmH2O every 30 mins
What is the effect of hyperventilation on the oxygen saturation curve and pH? effect?
sharp shift to the left; alkalosis; decreases oxygen bound to hemoglobin, making oxygen delivery to the tissues more difficult
How do you identify the cause of hypoxemia?
Calculate the alveolar-arterial gradient: PAO2- PaO2;
<15 is hypoventilation or decreased PiO2, >15 is venous admixture
how do you correct hypoventilation?
increase minute ventilation
What are the causes of venous admixture?
diffusion barrier impairment, V/Q mismatch (dead space, shunting), or anatomic shunting
What PAO2 indicates normal oxygenation?
What PAO2 indicates mild hypoxia?
What PAO2 indicates moderate hypoxia?
What PAO2 indicates severe hypoxia?
What kidney functions have a big effect on anesthesia?
removes salts and nitrogenous waste, maintains water and electrolyte balance, regulates pH and volume status, controls RBC production and BP
Why is proteinuria a concern with anesthesia?
you are losing what holds fluid and often transports drugs in the vasculature
What aspects of stabilization are VIP in patients with kidney problems? What else should be addressed?
BP and hydration; Electrolytes, anemia, acid/base, and azotemia
What drugs are most detrimental to the kidneys?
ketamine and NSAIDS
What is the minimum BP that should be maintained in kidney patients under anesthesia?
What electrolyte imbalance is of particular concern in patients with kidney issues?
What fluid flow rates should be maintained in patients with kidney issues? When must you use caution with this?
10 ml/kg/hr; with cardiac disease, hypoproteinemia, urinary tract obstructions
What may be the result of urinary obstruction/uroabdomen?
What condition does this ECG represent?
What are poor prognostic indicators with hepatic disease?
ascites, prolonged PT/PTT, thrombocytopenia, anorexia, hypoglobulinemia
Why is maintaining CO of upmost importance in patients with liver disease?
the liver needs oxygen, but also the liver needs blood flow to accomplish its purpose
What drugs should not be used in patients with hepatic disease (pretty much never use)?
benzodiazepines (prolonged sedation), NSAIDS, +/- alpha 2's because clearance is significantly altered
What are good choices for induction in patients with hepatic disease?
etomidate (NO concurrent benzodiazepines in these patients!), propofol
What are expected changes in bloodwork expected with PSS?
hypoglycemia, hypoalbuminemia, coagulopathies
Why can laparoscopic liver biopsies be a problem in patients with liver disease?
they inflate the abdomen to see things, which can compress the diaphragm and vena cava
What are the most important parts of the protocols used in patients with GI disease?
anti-emetics and gastro protectants
If a patient becomes suddenly severely bradycardic during GI surgery, what can be immediately done?
stop running the bowel to decrease vagal stimulation
What is a common sequelae to hyperthyroidism in the cat?
What are factors in hyperthyroid cats that increase anesthetic risk?
often concurrent cardiovascular disease, hypertension, arrhythmias, high metabolic demand, and increased PCV or liver values
What is a thyroid storm?
thyroid releases massive amounts of hormone all at once, causing a sudden increase. Most often seen in recovery due to catecholamine release in stress. Results in tachycardia, arrhythmias, hypertension.
What are drugs that can instigate a thyroid storm?
What are protocol changes that should be utilized as part of the protocol in a hyperthyroid cat?
propfol CRI, regional blocks, and opioids
What are protocol changes that should be avoided as part of the protocol in a hyperthyroid cat?
ketamine (thyroid storm), anticholinergics (inc. HR), acepromazine (vasodilation), full dose alpha-2 agonists (vasoconstriction)
What are factors in hypothyroid dogs that increase anesthetic risk?
ventilation due to obesity, decreased metabolic rate, cardiovascular depression, neuromuscular changes, hypothermia
What are protocol changes that should be utilized as part of the protocol in a hypothyroid dog?
opioids, benzodiazepines, ketamine, propofol
What are protocol changes that should be avoided as part of the protocol in a hypothyroid dog?
What are factors in animals with hypoadrenocorticism that increase anesthetic risk?
dehydration, hypothermia, electrolyte abnormalities
What are protocol changes that should be utilized as part of the protocol in an animal with hypoadrenocorticism?
steroids at 1/4- 1/2 the normal daily dose administered
What are protocol changes that should be avoided as part of the protocol in an animal with hypoadrenocorticism?
etomidate (adrenal suppression)
What are factors in animals with hyperadrenocorticism that increase anesthetic risk?
hypertension, cardiac disease, poor ventilation, weak intercostal muscles
What are protocol changes that should be utilized as part of the protocol in an animal with hyperadrenocorticism?
monitor VERY closely, supply fluids, support ventilation (weak intercostal muscles)
What is a particular risk associated with anesthesia in dogs with hyperadrenocorticism?
What are the effects of a pheochromocytoma in the body?
significant tachycardia and hypertension
What is phenoxybenzamine and for what is it used?
an alpha adrenergic antagonist that can help manage the tachycardia and hypertension seen with a pheochromocytoma
What is the risk in managing the cardiovascular effects of a pheochromocytoma?
if you treat with phenoxybenzamine you must gradually increase the dose to avoid a swing from hypertension to hypotension. BUT if the animal must undergo an anesthetic event, this will prevent the animal from responding to attempts to correct hypotension, should it occur
What is a particular risk associated with anesthesia in animals with diabetes?
animal becoming hypoglycemic
What are protocol changes that should be avoided as part of the protocol in an animal with diabetes?
alpha-2's (cause hyperglycemia)
What is the target range for glucose in animals with diabetes under anesthesia?
What does the monroe-Kellie doctrine state?
there are 3 things in the skull (brain, CSF, blood) and if the ICP is too high, MAP is too low, or if the brain tissue is swollen, perfusion can't be maintained
What is a cushing reflex?
in a patient with brain trauma, the brain begins to swell and is unable to be perfused, so it signals for BP to increase to try to force blood into the brain. The heart reacts by causing bradycardia to counteract this
What 3 signs should signal cushing's reflex?
hypertension, bradycardia, diminished respiratory effort
How can you help to decrease intracranial pressure in a patient?
elevate the head, hyperventilate to cause vasoconstriction, give mannitol/hypertonic saline to draw fluid from the brain. May also give steroids
What are protocol changes that should be included as part of the protocol in an animal with increased ICP?
dexmedetomidine, midazolam, opioids, propofol; pre-oxygenation, support of ventilation to stabilize CO2, analgesics to prevent hypertension from pain
What are protocol changes that should be avoided as part of the protocol in an animal with increased ICP?
anything that significantly alters BP, ketamine, acepromazine, using >1 MAC, nitrous oxide
What are medication side effects to avoid in patients with increased ICP?
Coughing, gagging, and vomiting, holding off jugulars
What are the most common issues during recovery?
delayed emergence, dysphoria
What are the most common causes of delayed emergence in recovery?
inappropriate dosing of drugs or inappropriate monitoring under anesthesia
What are drug factors that affect delayed emergence?
protein binding, hypothermia, electrolyte imbalances
What are the primary electrolytes of concern in patients experiencing delayed emergence?
K, calcium, glucose, lactose
Explain how to identify the cause of prolonged emergence.
A- check for airway obstruction,
B- monitor breathing for hypoventilation,
C- check for poor circulation or poor CO,
D- reverse appropriate drugs,
E- check electroytes, acid-base, calcium and glucose,
G- get the animal up and moving,
F- failure to find a cause (usually neurologic issue)
Explain the decision tree for reversing drugs that may be responsible for prolonged emergence
benzodiazepines, alpha-2's, then opiates
What are patient factors that contribute to the likelihood of a patient experiencing dysphoria?
age, vision impairment, ASA status (how sick they are), sepsis, metabolic distrubances
What are perioperative conditions that increase the risk of dysphoria?
airway obstruction, hypoxia/hypercapnia, bladder distension, vomiting
What are drugs that are known for causing dysphoria?
benzodiazepines, opioids, dissociatives
What are methods to help prevent dysphoria in recovery?
Reduce nausea, express bladder, reverse agents that may be causing this
What drugs should be considered to treat dysphoria in recovery?
acepromazine, dexmedetomidine, other alpha-2 agonist
What are species-specific concerns in recovery for cats?
mucous plugs, laryngospasm, hyperthermia in response to drugs
What physical characteristic allows succinylcholine to work?
it physically resembles an acetylcholine molecule so it can bind its sites, causing depolarization and contraction
What is the onset and duration of succinylcholine?
quick onset (30 s), short duration (5 mins)
What category of drug is succinylcholine?
depolarizing neuromuscular blocker
What drug is a reversible, competitive inhibitor of Ach?
What category of drug is atracurium?
non-depolarizing neuromuscular blocker
What is the onset and duration of atracurium?
acute onset (3-5 mins), intermediate duration (30 mins)
How is atracurium cleared from the body?
How is succinylcholine cleared from the body?
hydrolization by pseudocholinesterases
What is a side effect of prolonged, high doses of atracurium?
development of laudanosine, which causes seizures
What is the difference in action of succinylcholine and atracurium?
succinylcholine causes muscle faciculations, then relaxation; atracurium causes flaccid paralysis
What is the number one use of neuromuscular blockers?
eliminate laryngeal spasms and facilitate fast airway access
Other than for ease of intubation, what potential uses are there for neuromuscular blockers?
ocular surgeries, prevention of small, spontaneous movement, reduce resistance to mechanical ventilation, allow surgical access
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