Premedication Agents Flashcards
What 7 things should be provided in an anesthesia experience?
- critical body system support and protection (depressed function of the respiratory, circulatory, and nervous systems)
- sedation
- muscle relaxation
- anxiety reduction
- pain relief
- amnesia
- novel means to facilitate intervention or surgical approach
What are the 3 goals of anesthesia protocols?
- reduces pain, stress/anxiety, and inflammation (PSI)
- provide reversible CNS depression, no movement, musculoskeletal relaxation, and amnesia
- offer a controlled shock state with oxygen/glucose delivery and waste disposal
What part of the anesthesia protocol is the most important? Why?
premedication
allows for a majority of analgesia, relaxation, and anxiolysis
Is premedication only sufficient to provide good anesthesia?
NO
What 5 things are high inhalant concentrations linked to?
- post-op nausea and vomiting
- post-op congnitive dysfunction
- poor wound healing
- organ dysfunction (CNS and cardiorespiratory depression!)
- musculoskeletal disability
What does inhalant anesthetics not provide?
lasting pain, stress, or inflammatory relief
What are the 6 premedication goals? What is a possible additional goal?
- sedation
- anxiety reduction or loss
- muscle relaxation
- pain relief
- GI motility and protection
- decreased inflammation
amnesia
What are the most common GI agents, analgesics, and anti-anxiety/sedatives used in premedications?
antiemetics, motility agents, gastric protectants
opioids, alpha agents
benzodiazepines, phenothiazines
What are 6 common antiemetics and GI motility modifying agents used in premedications? What are some examples of each?
- antihistamines: Diphenylhydramine, Acepromazine
- dopamine antagonists: Metclopramide, Acepromazine
- serotonin antagonists: Ondansetron, Dolasetron
- antimuscarinics: Scopolamine, Glycopyrolate
- neurokinin antagonists: Maropitant (Cerenia)
- phenothiazines: Acepromazine, Chlorpromazine
How does the use of Maropitant (Cerenia) affect inhalant anesthesia?
decreases the anesthetic requirements
- decreases MAC by 15%
What are 3 reasons for adding butorphanol to other opioids for premedications?
- great sedative
- antiemetic
- antitussive
What aspect of the GI system is important to minimize perianesthetically?
acid and its deleterious effects
What 5 drug classes are used as esophageal and duodenal protectants in premedications? What are examples of each?
- antacids - calcium carbonate (neutralizes acid)
- mucosal protectant - Sucralfate
- H2 antagonists - Famotidine
- prostaglandin analog - Misoprostal
- PPI - Omeprazole (blocks H/K ATPase)
When are oral antacids especially useful?
- upper GI surgery
- thoracic surgery
In what 5 situations is the use of antiemetics especially helpful?
- if opioids are used in premeds
- obese patients
- patients with pre-existing GI disease or laryngeal/pharyngeal disease
- upper GI/abdominal surgery
- brachycephalics
How do the outcomes with PRN vs preemptive narcotic use in surgery compare?
PRN = IV bolus when pain recognized = increased beta-endorphin (stress hormones), increased lactate, sepsis, DIC, 27% mortality rate
PREEMPTIVE = CRI fentanyl = reduced beta-endorphin, <1% mortality rate
What novel long-acting opioid option has been developed? What allows it to reach the optical environment?
transdermal fentanyl solution with one-time application for moderate surgical pain (3-4 day repository effect)
octyl salicylate and isopropanol = crosses the stratum cornea
What opioids provide the most pain relief? Which one is most common in veterinary medicine?
- fentanyl
- oxymorphone
- hydromorphone**
- morphine
- buprenorphine
- butorphanol
How is the type of opioid chosen?
pure Mu agonists are used when pain is significant
- hydro/oxymorphone vs torb
What opioid works fantastically in cats?
buprenorphine
When are long-acting opioids commonly used? Examples?
in premedications
- fentanyl
- sufentanil
- alfentanil
- remifentanil
What opioids are not typically coupled with antiemetics? What 3 things do opioids not provide?
oxymorphone and methadone
- inflammatory relief
- stress relief
- keep animals asleep —> narcotization, nausea requires the repetitive administration of propofol or ket/val boluses
How is opioid use affected by ASA status? What 3 effects does it have on systemic organs?
regardless of ASA class, they are the first line treatment for acute and severe pain
- cardiovascularly soothing
- improves respiratory pattern
- improves post-op hemodynamics
What opioid is not shown to improve respiratory patterns?
potent fentanyls
What are 8 disadvantages to using opioids in premedications?
- immunosuppression
- narcosis
- ileus
- nausea
- inappetence
- urinary retention
- tumor metastasis and angiogenesis
- carbon dioxide non-responsiveness
How are alpha-2 agents used as premedications? Examples? How do they compare to opioids? When is use contraindicated?
great sedatives and analgesics in one drug - Xylazine, Medetomidine, Dexmedetomidine
very potent, resulting in significant reduction in cardiac output
patients in cardiac failure
What are 7 advantages to using alpha-2 agonists?
- analgesic and sedative (unlike opioids)
- excellent muscle relaxant (unlike opioids)
- possibly amnesic
- potentiates opioids
- vasoactive
- reversible (unlike Ace)
- works consistently (unlike midaz)
How are alpha-2 agonists able to potentiate opioids? How are they vasoactive? Why are they great for at risk patients?
work at the same G-protein mechanism = supradditive effect
limits capillary bleeding and increases blood pressure
they are reversible
What are the 3 major disadvantages to using alpha-2 agonists?
- need to be combined with other agents for best effects (opioids and benzos)
- need to be used at micro or mini doses
- extremely potent
What are the 3 major potent effects of alpha-2 agonists?
- reduces cardiac output
- reduced need for induction and inhalant anesthetics
- require hemodynamic physiology primer to understand benefit
What are some common benzodiazepines used as premedications? How do they act?
Midazolam (Versed), Diazepam, Flumazenil
short-acting (like fentanyl)
How do benzodiazepines as solo sedative agents compare in sick/neonates and other classes of patients?
work well
often disorients and excites patients —> do not work well
How do benzodiazepines act when combined with other sedatives?
minimizes the more potent agent, acting as a benign filler
How do the doses of Midazolam alter its affect?
LOW DOSE (0.05-0.1 mg/kg) = anxiolytic, increases appetite, arousal
MID DOSE (0.1-0.2 mg/kg) = sedation in sick patients, arousal in healthy patients
HIGH DOSE (0.3-0.7 mg/kg) = very sedating in sick, excitatory (disinhibitory) in healthy
What are 4 advantages to using benzodiazepines as premedications?
- safe - no hemodynamic consequences
- cheap
- may be amnesic
- work well when combined
What are 3 disadvantages to using benzodiazepines as premedications?
- don’t practically work by themselves
- often excite and disorient patients
- valium requires a carrier to work with other drugs (propylene glycol)
What phenothiazine is a common premedication? What are 8 advantages?
Acepromazine
- antiemetic
- antiserotonin
- antidopaminergic
- antihistaminic
- sound, reliable sedation
- splenic enlargement
- relaxation
- catheter friendly
What are 4 disadvantages to using acepromazine as a premedication?
- nonspecific
- vasodilatory
- all or not sedation with little titrability
- no reversibility
How is the use of anti-anxiety medications different in ASA II and III patients?
ASA II = IM or IV administration with the use of stealthier sedatives, like Acepromazine and Dexmedetomidine (mini and macro doses)
ASA III = IV administration with the use of weaker sedatives at higher doses, like Midazolam +/- microdoses of Dexmedetomidine or Acepromazine
What anticholinergics are commonly used as premedications?
Glycopyrrolate (Robinul), Atropine
What is the main advantage of using anticholinergics as premedications? 4 disadvantages?
can induce tachycardia +/- antiemetic
- induced tachycardia!
- SV decreases and HR increases
- viscous sludging in the pancreas, lacrimal glands, bladder, and salivary glands
- ileus
In what 5 cases are the use of anticholinergics as premedications particularly helpful?
- bulbar ocular surgery
- pre-existing GI disease
- heavy vagal tone
- pediatrics
- if blood pressure is low
What are 3 reasons anticholinergics are no longer standard use in small animal practice?
- tachycardia is not helpful to perfusion, rather bradycardia allows for better filling and perfusion of ventricles
- sludging of secretions and GI ileus can last much longer than the half-life
- species difference in CNS effects
Why can’t we use anticholinergics with alpha-2 agents?
profound hypertension is likely, which increases myocardial work when oxygen extraction is already maximal
Why are pain and inflammation commonly correlated? Why do analgesics cover inflammation?
both associated with redness, heat, and swelling
worsens inflammation with opioid-induced hyperalgesia (OIH) due to glutaminergic systems, NMDA activation, facilitation of protein kinase C calcium channeling, and interneuron crosstalk
What are some common NSAIDs used as premedications?
- Rimadyl
- Previcox
- Deramaxx
- Etogesic
- Ketofen
- Phenylzone
- Zubrin
- Banamine
- Metcam
- children’s aspirin
What are 5 advantages to using NSAIDs as premedication?
- potent anti-inflammatory
- mechanism similar to steroids - decreases prostaglandin production
- analgesic
- antipyretic
- non-dependence
What are 6 common side effects associated with NSAID usage in premedication? What causes them?
- gastric ulceration
- renal ischemia
- coagulopathy - anticoagulation, increased vasoactivity
- bronchospasm
- hypertension (humans)
- reproductive issues - altered uterine blood flow and muscular activity
inhibits constitutive COX and LOX
When are NSAIDs used pre/intra-op and post-op?
PRE/INTRA = elective ASA I or II cases, with preexisting fluids, tons of evidence
POST = pre-existing hypovolemia, cogulopathies, pre-existing hypotension, ALI/ARDS, little evidence
What action do steroids have as a premedication? In what 5 cases are they considered safer than NSAIDs?
prednisone/prednisolone —> excellent anti-inflammatories at appropriate doses
- brachycephalics
- laryngeal surgery
- CNS surgery
- endotoxemia
- renal disease
What are some other anti-inflammatory techniques or drugs?
- cryotherapy
- low-level laser therapy
- topical arnica
- DMSO
Why do we use reversal agents?
- to arouse sedated animals
- remove some effects of premedication agents, like sedation and analgesia
- arouse in emergencies
How is timing and dose important in the administration of initial reversal agents?
TIMING = if Dex or an opioid was given 2 hours ago, most is probably gone and reversal is not needed
DOSE = high doses have lengthier duration, so a reversal is needed, however at low doses, animals should wake up by themselves
How should reversal agents be given?
- IM, unless there is emergent use (IV)
- as partial reversals to leave some stress/pain relief and muscle relaxation on board
What are 4 reversals for opioids?
- Naloxone
- Naltrexone
- Nalbuphine
- Butorphanol
What reversal is used for benzodiazepines?
Flumazenil
What are 3 reversals for alpha-2 agonists?
- Atipamezole
- Yohimbine
- Vatinoxan
How do the aspects of premedications differ in low risk and high risk ASA patients?
ASA I, II = unlimited drugs at standard doses, multimodal
ASA III, IV = limited drug choices at modified doses, more multimodal
What are the 3 modes of administration of most premedication?
- IM - quads most reliable, most common in patients within 30 mins of procedure
- IM and IV - long procedures that need sudden and sustained effects
- IV - obese or brachycephalic patients
When are oral premedications able to be given?
- giving time for proper absorption (night prior)
- not perioperatively
What is the last resort for premedication administration?
transmucosal
(or pre-hospital entrance for severe anxiety)
How does the timing of premeds differ in anxious/aggressive and calm patients? How can existing medications alter timing?
- anxious/aggressive = give premeds first then catheterize
- calm (or ASA IV) = place catheter first
if opioids have already been given within hours, a full dose is not necessary
What 3 modifications of premedications in healthy, aggressive patients may be necessary?
- addition or increase in alpha-2 agents
- addition of ketamine
- avoid acepromazine
What modification of premedications in sick, aggressive patients may be necessary?
addition of low doses of alpha-2 agents, ketamine, butorphanol, or midazolam
How should the patient be moved once sedated?
- on a back board or gurney
- protection of key areas, like head and neck
What are 3 important agents needed in premedications? What are 2 possible additional agents?
- opioid, preferably one that lasts longer than fentanyl!
- sedative, preferably one that counteracts the side effects of the opioid and provides sleep and reduced anxiety
- Anti-inflammatory modality or drug
- Anticholinergic=glycopyrolate (vs. atropine) if needed (pediatric, low resting heart rate, high vagal tone, intraocular or intracranial disease)
- Gastrointestinal motility, protective agents
What are the 3 agents found in “kitty magic?” When is it given?
- ketamine
- dexmedetomidine
- torb
mixed and given IM for elective procedures
What are 2 common premedication protocols for low-risk patients?
- Dexmedetomidine + opioid of choice at usual dosage
- Acepromazine + opioid of choice at usual dosage
What is a common protocol for patients at higher risk (ASA III)?
Midazolam + opioid of choice + Dexmedetomidine
What is a common protocol for patients at the highest risk (ASA IV, V)? How is it given?
Midazolam + Ketamine + Hydromorphone + Butorphanol
combined and given to effect IV
All of the following are essentials of the “checklist” in devising an anesthesia menu or protocol for a small animal patient undergoing general anesthesia EXCEPT:
a. muscles are relaxed and procedural stiffness if obtained
b. CNS is irreversibly depressed
c. pain, stress, and inflammation are addressed
d. nausea, GI motility and protection are addressed
B
Which of the following might be a suitable premedication combination for an apparently healthy aggressive pit bull mix who needs 2 sutures in his carpal pad?
a. Acepromazine and butorphanol delivered OTM
b. Butorphanol and Acepromazine delivered OTM
c. Dexmedetomidine and Butorphanol +/- ketamine IM
d. Dexmedetomidine and Butorphanol delivered in the fat
e. Acepromazine and Butorphanol delivered IV
C
Which of the following classes of premeds and actual agents within that class are correctly matched?
a. Benzodiazepines: medetomidine, dexmedetomidine
b. Phenothiazines: acepromazine, chlorpromazine
c. Benzodiazepines: buprenorphine, butorphanol, fentanyl
d. Alpha-2 agonists: buprenorphine
e. Opioids: midazolam, diazepam
B
Which describes the best area to deliver an Intramuscular injection in a small animal patient for premedication?
a. lateral cervical neck area
b. right radius
c. quadriceps or cranial thigh
d. left toe
e. epaxials
C
Most services and hospitals have a LOW risk patient anesthesia protocol and a HIGH(er) risk patient anesthesia protocol. Which of the following best describes the difference between the two in terms of the premeds?
a. low risk anesthesia protocol uses a lot of etomidate in premeds
b. higher risk anesthesia protocol may contain a high dose Dexmedetomidine, as it is very safe
c. low risk anesthesia protocol usually contains a lot of ketamine
d. low risk case anesthesia protocol may contain high-dose midazolam, as it works well for healthy patients
e. high risk anesthesia protocol may contain high dose Midazolam, as it is a very safe drug in high risk cases
E
A 225 pound mastiff presents for neutering. His premedication drugs would be altered best according to which statement?
a. premed OTM since he has large jowls
b. premed IV with relatively lower doses of all drugs based on BW and metabolism
c. premed with higher doses of all drugs in case of possible aggressive episode
d. premed IM with a short 25 g needle
e. premed IM with a long 25 g needle
B
An obese patient presents for anesthesia and you need to premedicate it. Which best describes what you will use, do, and when (drugs, routes, timing)?
a. give high dose of Acepromazine orally
b. dose on lean weight and give everything IM
c. give high dose of Dexmedetomidine IM
d. dose on lean weight, use potentially reversible combinations, and give them both IV
e. give high dose of Acepromazine IM
D
Opioids are an essential part of any premed and are first line agents in treating pain because they are essentially devoid of severe cns, cardio, and respiratory depressant effects. They do have some downfalls, side effects, or disadvantages however, and amongst them are all of the following EXCEPT:
a. urine retention
b. nausea or vomiting
c. narcosis
d. pain
e. inappetance
D
A hypothyroid dog presents for anesthesia and his TT4 level is high (6.0, normal 1.3-4.0ng/dl). He has been oversupplemented with levothyroxine. Which statement below best describes how thyroxine can affect your premedication?
a. avoid anticholinergics (atropine, glycopyrolate) and give lesser doses of excitatory opioids (hydromorphone)
b. current state has no effect on premed drug choices, doses, or timing
c. this dog should not be going under general anesthesia
d. use atropine
e. avoid opioids
C
All of the following are means to relieve inflammation in surgical patients EXCEPT:
a. local anesthetic
b. low level laser therapy, cold lasers
c. opioids
d. cryotherapy
e. NSAIDs and steroids
C
An overall healthy patient is struggling and making catheter placement difficult. Which of the following premedications would be helpful in allowing the placement of the intravenous catheter?
a. Fentanyl SQ
b. Midazolam OTM
c. Dexmedetomidine and hydromorphone mixed IM
d. Propofol IV
e. Ketamine IV
C
Dexmedetomidine and hydromorphone help provide all of the following EXCEPT:
a. sedation
b. analgesia
c. increased need for inhalant
d. anxiolysis
C
patient is calm = less inhalants needed
What is Zenalpha?
IM injection of Medetomidine and Vatinoxan for dogs
What is the difference between Medetomidine and Dexmedetomidine?
MED = mixture of Levemedetomidine and Dexmedetomidine that is half as potent
DEX = active component of Medetomidine that is 2x as potent
What are the 2 phases of the key cardiovascular effects of Dexmedetomidine and Medetomidine?
PHASE 1 = initial 30-45 mins where there is vasoconstriction and reflex bradycardia
PHASE 2 = central sympatholysis, bradycardia, and vasodilation
What is the difference between Atipamezole and Vatinoxan?
ATIPAMEZOLE - antagonizes both central and peripheral alpha-2 receptors
VATINOXAN - poor penetration of the BBB only reduces peripheral cardiovascular effects of alpha-2 agonists
