Exam 2: Lecture 8: Pre-Medications Flashcards
Why do we premedicate animals for surgery?
- Easier handling of patient
- Lower does of induction and manitenacne drugs (Prolems with pulmonary and cardaic issues if we use too much)
- Pre-emptive analgesia
- Smooter recovery period
T/F: You can induce an unsedated horse?
False!!!
NEVER induce an unsedated horse
What are the benefits of premedication?
- Effective premed = lower amount of drug needed later
(Minimum alveolar concentration sparing effect for inhalent anesthetics) - Synergistic effects from combining drugs produces better results than a single drug alone
- Decreases cost because lower amounts of induction and maintenance drug used
The theory of pre-emptive or preventative analgesia is???
Reduces the amont of anesthestics required to produce a surgical plane of anesthesia
- Stabilize the maintence of anesthesia
- Reduced the amount of analgesics required intra-operatively and post-operatively
- Decreases overall patient morbidity associated with surgeyr and anesthesia
What is the goal of anaglesia?
Presurgical and postsurgical analgesia
What does part A described?
Surgical and post-surgical afferent input
What does part B described?
Post-surgical analgesia
What does part C described?
Pre-surgical analgesia
What does part D described?
Pre-surgical and post-surgical analgesia
Which Administration technique is preferred?
IM, SQ, IV
IV and IM is preferred over SQ
This type of medication administration is typeically given in more anxious or fractious patients to facilitate IV catheter placement
IM
This type of medication administration is typeically given if the patient already has a catheter, the dose can usually be lowered due to more immediae onset and greater degree of effect
IV
The following are examples of which administration type?
- Lumbar epaxial muscles on either side of the dorsal spinous processes
- Semimembranous and Semitendinosus
- Quadricpes femoris muscle
- Cervical epaxial muscles
- LA patients: Know the landmarks for the “Triangle” area to inject
IM site injections
On the pelvic limb what important structure should be avoided
Sciatic nerve
What are the 5 commonly used drug classes for premedication
- Anticholinergic
- Phenothiazines
- Alpha 2 agonists
- Benzodiazepines
- Opioids
Which class of premedication is described as:
- NOT routinely included in the premedication unless high vagal time is currently suspected or a pediatric patient
Anticholinergics
- prefer to give them only as required during anesthesia
Which anticholinergic drug is able to cross the blood brain barrier and placenta, but limited ability of glycopyrrolate to cross
Atropine
Which anticholinergic causes pupil dilation
- impairs vision and may lead to poor recovery in some species (EX: cats)
atropine
__________ in high doses inhibit urinary and GI motility
- use cautiously in horses and cattle because colic and rumen stasis may occur
Anticholinergics
What is the duration of action for Atropine
Varies by dose and species
- About 60-90 minutes
How should you administer atropine
IV, IM, SQ
in emergency it can be given via endotracheal tube
What is the effect of Atropine
Increased heart rate and blood pressure
- decreases salivary and bronchial secretions
What is the duration of action for Glycopyrrolate
Longer than atropine
- around 2 to 3 hours
How can Glycopyrrolate be administered?
Iv, IM, SQ
What is the effects of Glycopyrrolate
Increases heart rate and blood pressure
- Decreases salivary and bronchial secretions
Side effects of Anticholinergics include?
- Hot (as a horse)
- Dry (as a bone)
- Blind (as a bat)
- Red (as a beat)
- Mad (as a hatter)
EXTRA
EXTRA
Following IV injection of _____, an initial increase in vagal tone may occur and a transient decreased heart rate or heart block can occur. This is followed by the expected increae in heart rate
Atropine
What is recommended when giving Atropine
Recommended giving 1/2 atropine dose IV and then the rest IM or SQ
______ is less likely to cause an inital increase in vagal tone compared to atropine
Glycopyrrolate
What is the MOA for Phenothiazines (EX: acepromazine)
Dopamine (D1 and D2) receptor antagonist in the CNS
- acts like a straight jacket: looks calm and relaxed, but internally may be anxious SAME
Which drug is most commonly used for its tranqilizing and antimetic effects
Acepromazine
T/F: Acepromazine relives anxiety, which is why its a good tranq
FALSE!!!
- it does not relieve anxiety
What is the duration for Acepromazine given IV
Peak effect around 15 min.
What is the duration for Acepromazine given IM
Peak effect around 30 min
T/F: Acepromazine has a long lasting effect (4-8 hours) and has no reversal agent
TRUE!!!!
T/F: Acepromazine has some muscle relaxation and analgesia effects
FALSE!!!
Acepromazine has some muscle relaxation, but no analgesic effect
_______ works synergestically with analgesic drugs, so the dose can be lowered and still achieve the desired sedative effect
Acepromazine
What is the dose dependent MAC of Acepromazine
around 30-40%
Which drug has anti-histamine effects, so avoid using prior to skin testing for allergies
Acepromazine
Also has
- Anti-nausea effect
- Anti-arrythmic properties
- Altered thermoregulation
(decreases body temp when used)
FITB:
Acepromazine: a-1 adrenergic blockade = vasodilation = ?
- subsequent Epinephrine administration may cause a paradoxial drop in blood pressure (B2 effect) because alpha receptors are blocked
Hypotension
_________ causes anti-sympathetic effects due to decreased mobilization of catecholamines centrally and peripherally
Acepromazine
Which drug is histrocially not used in epipletic patients because it was thought to lower the seizure threshold. This is controversial because recent literature has not found an association btw the two
Acepromazine
Avoid using Acepromazine in what type of situations?
- Fractious or agressive patients or those with high anxiety
- Liver disease or portocaval shunts
- Valubale breeding stallions due to potential for paraphimosis (inability to retract the penis)
- Von Willebrands disease or other clotting disorders
- Shock or cardiovascular disease
What effect does Acepromazine have on Van Willebrands disease or other clotting disorders?
Acepromazine decreases platelet aggregation
what does Acepromazine have on pt’s with shock or cardiovascular disease
Reduced PCV due to splenic sequestrations of RBC’s
What drug has the following effects on boxers or short nosed dogs
- Spontaneous fainting or syncope may occur due to sinoatrial block caused by excessive vagal tone
- A low dose may be considered or it can be avoided if possible
- Atropine may help prevent these effects
Acepromazine
What drug class has the following effects:
- Overally effect in the patient is sedation
- muscle relaxation
- analgesia
Alpha 2 adrenoreceptors agonists
Xylazine, detomidine, romifidine, medetomidine, and dexmedetomidine are part of what drug class
Alpha 2 adrenoreceptors agonists
What is the physiology of Alpha 2 adrenoreceptors agonists
- Sedation
- Bradycardia
- decreased tachycardia
- Anti-shivering
- Vasoconstriction
- Vasodilation
- Dieuresis
- Analgesia
__________ are transmembrane G-protein coupled receptors located on pre and post synaptic sites on nerve and cell membranes in the brain, spinal cord, and periphery
Alpha 2 receptors
MOA of Alpha 2 adrenoreceptors agonists
Produces CNS depression by stimulation of pre and post synpatic A2 adrenoreceptors in the CNS and periphery = Decreased NE release and reduces ascending nociceptive input = decrease in CNS sympathetic outflow and decrease in ciruclating catecholamines
What are the 4 types of Adrenergic receptors
- Alpha 1
- Alpha 2
- Beta 1
- Beta 2
What type of Adrenergic receptor is described as:
- Vasoconstriction
- increased peripheral resistance ( blood flow)
- Increased blood pressure
- Mydriasis
- Increased closure bladder sphincters
Alpha 1
What type of Adrenergic receptor is described as:
- Inhibits NE release
- Inhibits AcH release
- Inhibits Insulin release
Alpha 2
What type of Adrenergic receptor is described as:
- Increased HR
- Increased lipolysis
- Increased myocardial contractility
- Increased Renin
Beta 1
What type of Adrenergic receptor is described as:
- Vasodilation
- Decreased peripheral resistance
- Bronchodilation
- Increased Glycogenolysis (muscle and liver)
- Increased Glucagon release
- Relaxes uterine smooth muscle
Beta 2
With A1 is there more NE or E
NE
With A2 is there more NE or E
E
With B1 is there more NE or E
NE = E
With B2 is there more NE or E
Way more E than NE
How can Alpha 2 adrenoreceptor agonist be administered
can be given IV, IM, buccally and by epidural route
Which adrenergic receptor selectively determines the amount of cardiovascular effects due to A1 stimulation
A2
Alpha 2 adrenoreceptors agonists are reversible with the use of _____ (Ex: yohimbine, tolazoline, and atipamezole)
A2 adrenoreceptors antgonists
What are the cardiovascular effects of Alpha 2 adrenoreceptors agonists
induced bradycardia due to
- increased systemic vascular resitance (SVR) in the periphery
- Decreased sympathetic tone due to decreased NE outflow in the CNS
Which drug can increase cardiac sensitivity to catecholamine induced arrythmias during halothane anesthesia
Xylazine
Cardiac output can fall how much due to decreased HR and increased vascular resistance due to which drug class
- PCV increase = MM pale + gray because hearder to get O2 to tissues
Alpha 2 adrenoreceptors agonists
Should you use an anticholinergic when giving an alpha 2 agonists?
NOT generally recommened to give together as a premed
If you are really concerned about the level of bradycardia in a patient that received an A2 agonists, then consider the following steps?
- determine the patients BP
- Check with surgeon (has stimulation started)
- How long since drugs were given
- if BP is low and it has been 30-45 min since a2 agonist admistration and surgical stimulation is either not helping or going to take a while to begin
- consider the administering anticholinergic IM or SQ
- Lidocaine could be considered instead
- Reversal with atipamezole (IM) +/- anticholinergic
What are the behavioral effects of an Alpha 2 adrenoreceptors agonists
- agression after administration is reported in horses
- If patient is very nervous or excited, it may show an inadequate response, strartle when touched or a loud noise occurs
What are the respiratory effects of a pt given Alpha 2 adrenoreceptors agonists
- Hypoventilation or apnea due to respiratory center depression
- Decrease sensitivity to increased PCO2 in the respiratory center
- Horses and brachycephalic animals are prone to stridor and dyspnea from upper airway obstruction
- Sneezing/ itchy nose noted occasionally in donkeys
What are the GI and renal effects of Alpha 2 adrenoreceptors agonists
- Decreased gastric acid secretions and GI motality
- May cause vomiting in dogs and cats
- Swallowing refles obtunded
- Excellent analgesic for treating GI pain
- Suppresses insulin release = hyperglycemia and glucosuria
- Reduces hepatic blood flow and rate of metabolism
- Inhibits anti-diuretic hormone and increases release of atrial natriuretic factor = diuresis with increased sodium and water excretion
With Xylazine, what is important to be aware of?
2 different concentrations for small animals and ruminants
What is the duration of Xylazine
Fast onset within 1-5 minutes and effects lasts 20-40 minutes after IV injection
Which drug may induce premature delivery in cattle due to oxytocin like effects
Xylazine
How can Detomidine be administered
IM or IV
there is a gel form that can be given sublingually to horses
What is the duration of Detomidine
Onset of action is slightly longer than xylazine
- Effects lasts 90-120 minutes
- dose depenedent and route dependent
What is the duration of Romifidine
Effects lasts 45 to 90 minutes (up to 2 hours) after IV injection
Which drug is generally thought to produce less ataxia than xylazine, so it became popular for use in dentals and other standing procedures
Romifidine
Which drug can be reveresed with Atipamezole
Dexmedetomidine
What is the duration of Dexmedetomidine
Quick onset after IV administration (1-3 minutes) and IM administration (5-10 minutes). Trasmucosal takes longer (30-60 minutes)
- effects lasts 90-120 minutes
Which drug has an onset in about 10 minutes afer IM injection and even faster if given IV
Medetomidine
Which drugs analgesia lasts about 30 minutes, but sedation can lasts up to 2 hours
Medetomidine
How can you reverse Medetomidine
Atipamezole
When you use Zenalpha what should you always do?
decrease the dose when you use
What two drugs make up Zenalpha and how are they important
Medetomidine (crosses the blood brain barrier)
Vatinoxan (Peripheral Alpha 2 antagonist and does not spike BP)
What are the 4 main points of Zanalpha
- Procedural sedation
- Short onset (5-15min)
- Short duration (30-45 min)
- CV stability / parameters maintained at more acceptable levels
What drug is typically used to reverse Xylazine
Yohimbine
What drug do you avoid using in camelids due to adverse effects?
Tolazoline
Which drug has a higher alpha 2 : alpha 1 selectivity so indicated for the reversal of medetomidine and dexmedetomidine
Atipamezole
The concentration of ____ was formulated so that the volume of injectate is the same (mL for mL) as the dose of dexmedtomidine given
Atipamezole
Atipamezole is always given?
IM - effects seen within 5 mintues
- Because it work so fast DONT give IV
Which class of drugs has many potential uses such as
- Centrally acting muscle relaxants
- anti-anxiety effects
- Treatment of active seizures
- Used during anesthesia
Benzodiazepines
What is the MOA of Benzodiazepines
Enhances the activity of the CNS inhibitory neurotransmitter gamma aminobutyric acid (GABA) by binding to a specific site on the GABAa receptor
- which opens chloride channels and hyperpolarizes the membrane
What are the effects of Benzodiazepines
- Reduces sympathetic output
- Minimal Sedation
- Muscle relaxation
- Antiseizure effects
- Minimal cardiovascular and respiratory effects
- No analgesia
Which drug must be formulated in propylene glycol to make drug soluble. So rapid IV administration can cause bradycardia, hypotention or apnea
Diazepam
What is the duration of Diazepam
Metabolized in liver and duration of action is 1 to 4 hours
- dirty drug
What is the paradoxial effect with Diazepam
Paradoxical excitment and agression can occur
Which drug is water insoluble, so do NOT give IM
Diazepam
Which drug is water soluble so you can give IM, IV, or via mucus membranes
Midazolam
______ is more potent than Diazepam
Midazolam
Which drug is metabolized in the liver, but metabolites are inactive (unlike diazpam). So shorter acting with less risk of accumulation
Midazolam
T/F: Midazolam is the better choice for sick, debilitated or older patients
true
What paradoxial effect may Midazolam have?
Excitement and aggression can occur
Which drug is fine for a certain population of patients but dont count on using it for an otherwisw healthy, normal patient
Midazolam
What drug causes excitation instead of sedation and now you have to restrain a cat who is both high and aggressive
Midazolam
Which drug will rapidly reverse all effects of Benzodiazepines
- Expensive
- Occasionally needed to reverse sedative and or dysmoprhic effets of benzodiazepines in the recovery period, during CPR or if the liver metabolism is impaired
- DO NOT give to an epileptic patient
Flumazenil
Which class of drugs are coupled to G protein receptors that ultimately decrease conducatance through calcium channels and open inward potassium channels = hyperpolarization of membranes and decreased propagation of action potentials
Opioids
What is MOA of Opioids
Reversible combination with one or more receptors (mu, kappa, and delta) in the brain and spinal cord
Where are Opioids metabolized
In the liver and the metabolites of some drugs have analgesic properties
What are the CNS effects of Opioids?
- Sedation
- Euphoria
- Dysphoria
Which drug class has respiratory effects inluding
- depression of the respiratory center response to hypercapnia and hypoxemia
- cough suppression
- Panting
Opioids
What effects do Opioids have on the cardiovascular system
Bradycardia
GI effects of which drugs include
- vomiting
- defectation
- salivation
- decreases gastric emptying time
- ileus
- vomiting is uncommon in painful animals
- Morphine is the only opioids to cause these effects
Opioids
Which species while on Opioids have Miosis and Mydriasis
Miosis = dogs
Mydriasis = cats
Which drug has a high affinity for mu receptors, but some affinity for delta and kappa receptors
- Hydrophilic compared to other Opioids so longer duration of action than lipophilic Opioids
Morphine
Morphine
- Can give IV = _______ release and subsequent hypotension
Histamine
What is the duration of Morphine
4-6 hours
- Dose dependent MAC sparing effect
Which drug is semi-synthetic pure mu agonist with similar properties to morphine (EX: hydrophilic)
Hydromorphone
Which drug is 5-10x more potent?
- Morphine
- Hydromorphone
Hydromorphone is more potent
Hydromorphone is dose dependent analgesia, so how can it be administered?
IV, IM, SQ
- Less likely to vomit if given IV
What is the duraction of action for Hydromoprhone
4-6 hours (for acute surgical pain, lasts about 3-4 hours)
When giving hydromorphone, which animals are reported to present with hyperthermia.
Cats
- but occurs with other Opioids
Which drug is a synthestic pure mu agonist that is 100x more potent than morphine
Fentanyl
What is the duration of Fentanyl
Fast onset (1-2 min) and short duration (around 30 min) due to lipophilicity
- Given IV bolus, followed by a continiouse rate infusion
Which drug is half as potent as Fentanyl
Remifentanil
Which drug us unique because it is metabolized by nonspecific esterases that occur in the body (mainly skeletal muscle). This leads to clinical advantage of extremly rapid clearence rate that is not dependent on liver or kidney function
Remifentanil
Which drug requires a CRI due to rapid clearence. Recivery occurs 3-7 minutes after discontinuation of CRi, so could be useful in situations in which intense analgesia is nedded for a short time period
Remifentanil
Which drug is a syntheteic pure mu agonist with similar potency to morphine, but causes less sedation and more dysphoria
Methadone
Which drug is least likely of a u-agonist opioids to cause vomiting
Methadone
Methadone is a ______ receptos antagonist and _______ reuptake inhibitor, which could improe analgesia and help prevent development of tolerance
NMDA
serotonin
What is the duration of Methadone
2-6 hours
What is one of the most used opioids?
Butorphanol
Which drug is a mixed agonist - antagonist (agonist at kappa receptor and parial mu receptor against IR considered an antagonist at mu)
Butorphanol
Which drug is used for mild to moderate visceral pain, that is not effective for severe or orthopedic / dental pain
Butorphanol
Which drug has mild sedation and anti-tussive effects; less respiratory depression than pure mu agonist “celling effect”
Butorphanol
What is the duration of Butorphanol
30 min to 2 hours
Which drug can be used to reverse sedative or respiratory effects of pure mu agonist
Butorphanol
Which drug is a partial mu agonist and an antagonist at kappa receptors
Buprenorphine
Which drug is not adequate for severe pain + does not provide much analgesia
Buprenorphine
Buprenorphine has a higher receptor affinity and can displace ___________ agonist, and makes it difficult to antagonize
Pure mu
In order to cause a response similar to full mu agonist, ________must occupy a higher number of receptors?
Buprenorphine
What is the duration for Buprenorphine
Long duration of action (4-8 hours, maybe 12 hours depending on dose), but slower onset of about 30 minutes to an hour after IV administration
How can Buprenorphine be administered
IV, IM and some SQ but can also be given via oral transmucosal route in cats
Simbadol is a brand of which drug that is for SQ injectable use in cats for 24 hour duration of surgical pain control
Buprenorphine injection
T/F: Simadol is FDA approved in cats?
true
Which drug was approved for use by the FDA in 2022 to help with post-op pain control up to 4 days in cats
- adminsiter transdermally - risk of accidental exposure, so wear gloves to apply
Transdermal buprenorphine
Which drug is Used to reverse pure
mu and mixed
agonist/antagonists (ex:
butorphanol) because it
has a high affinity for
mu and kappa receptors
but no intrinsic activity
Naloxone
What is the duration of Naloxone
Rapid onset (1-2 min) and lasts 30-60 min
Extra
What is the term for A state of CNS depression and analgesia
produced by the combination of a
tranquilizer or sedative and analgesic drug
Neuroleptanalgesia
- The patient may or may not remain
conscious - Useful for premedication or for short medical
or surgical procedures - Be aware that bradycardia and respiratory
depression can occur - Typically, the dose of each drug can be
lowered due to synergism
The follow are examples of?
- Acepromazine + opioid
- Benzodiazepine + opioid
- Alpha2-agonist + opioid
- Example: 20 mcg/kg Dexmedetomidine +
0.2 mg/kg Butorphanol + 5 mg/kg ketamine
IM produces heavy sedation to anesthesia
in cats having castration performed (this is
called “Kitty Magic” in some practices) - For dental or standing procedure in a horse:
detomidine 40 mcg/kg IV + morphine 0.3
mg/kg IV
Neuroleptanalgesia
Do we have to be careful providing Anesthesia for obese or normal sized pt’s
Obese
Opioids and propofol may depress ventilation or cause apnea so monitor _____, atrial blood gases and be ready to provide ______ while giving anesthesia for obese patient
ETCO2
ventilation
- Continue oxygen in recovery and keep intubated until patient can maintain airway
- reduce volume of drugs given via epidural route
Avoid what type of agonist if possible to due cardiovascular depression while giving anesthesia for obese patient
A2 agonists
