Preanesthetic Agents Flashcards
Intramuscular
Stressed or excited patients
Allow 15-30 min for max effect
Muscle location important
Intravenous
Place IV catheter first
Allow 3-5 min max for effect
T/F: SQ not recommended for premedication
TRUE
Subcutaneous
Less vascular supply= slow rate of absorption
Uptake of drug is dependent on tissue perfusion
Lead to patchy absorption (drug dependent)
Most adverse drug effects are associated with _________
High drug doses
10 steps for anesthesia drug selection
- Antiemetic
- NSAID
- Opioid
- Sedative agent
- Is anticholinergic warranted
- Induction agent
- Maintenance agent
- Local/ regional blocks
- Intra- op nociceptive stimulation
- Post-op analgesic plan
Medication for pre-hospital sedation
Gabapentin and Pregabalin
Trazodone
Gabapentin & Pregabalin MOA
Binds to alpha 2 delta subunit or voltage dependent channel in CNS
↓ the release of glutamate , dopamine, NE, and serotonin
Gabapentin & Pregabalin uses
High doses= sedation
Adjunct analgesia or neuropathic pain
Trazodone MOA
Serotonin antagonist and reuptake inhibitor
Histamine antagonist and alpha-1 adrenergic antagonist
Trazodone uses
Sedation and anxiolysis within 1-2 hours
Caution of trazodone
Combining with SSRI, TCA, or MAOIs = serotonin syndrome
Chill protocol for pre-hospital sedation
Gabapentin night before visit
Gaba and melatonin 1-2 prior to appointment
Acepromazine admin 30 before appointment
Pre-anesthetic drug classes
Antiemetics
NSAIDs
Opioids
Phenothiazines
Benzodiazepines
Alpha-2 agonists
Anticholinergics
Antiemetic medications
Maropitant and Ondansetron
Maropitant (Cerenia)
Neurokinin (NK1) receptor antagonist
SQ or IV 45 min- 1 hr before premed
PO 2 hr before premed
Ondansetron (Zofran)
5-HT3 (serotonin type 3) receptor antagonist
IV, IM, SQ, PO
30 min before or with premeds
T/F: antiemetics will not decrease the incidence of gastroesophageal reflex (GER)
TRUE
What are NSAIDs used for?
Mild to moderate inflammatory pain
Onset time: 30-60 minutes
FDA approved NSAIDs in dogs
Carprofen, meloxicam and robenacoxib
FDA approved NSAIDs in cats
Meloxicam, robenacoxib
Precautions of NSAIDs
GI toxicity: excessively high dose, two NSAIDs @ the same time, conjunction with corticosteroids
Hypoalbuminemia
Metabolism in cats (deficiency glucoronyl transferase enzymes)
NSAID contraindications
Pre-existing hypotension, hypovolemia or renal dz
GI procedures
Opioids MOA
Bind to opioid receptors located @ presyn. and postsyn. sites in the CNS and peripheral tissues (mu, kappa, delta)
Pure agonist opioids
Morphine, hydromorphone
Class 2 controlled drugs
Pure opioid uses
Prevention and tx of pain (visceral and somatic)
Sedation in pediatric, geriatric or debilitated patients
Pure agonist opioid precautions
IV morphine or meperidine (histamine release)
Morphine less efficacious in cats
Dose dependent ↓ in RR, HR, and BP
Post-op hyperthermia in cats (hydro)
Vomiting
Partial agonist opioids
Buprenorphine
Simbadol (more concentrated buprenophine)
Zorbium (transdermal buprenorphine)
class 3 drugs
Buprenorphine
Less efficacious than the pure agonist opioids
For visceral and somatic pain
Buprenorphine PK
Slow onset (30-45 min IM, 15-30 min IV)
High affinity for Mu receptors
Ceiling effects on resp. depression
30x more potent than morphine
Zorbium use
Major orthopedic or neuro procedures
Dentals that require extensive extractions
Zorbium PK
Onset time 1-2 hrs
Duration 4 days (96 hrs)
Must wear PPE or application
T/F: Zorbium is for cats only
TRUE
Agonist/ antagonist opioids
Butorphanol (class4 drug) and nalbuphine
Agonist/ antagonist opioid uses
Treats mild visceral pain ONLY
Partial reversal agent for pure agonist
Agonist/ antagonist opioid PK
Duration: 30 min- 1 hr
Ceiling effect on analgesia
4-7x as potent as morphine
Buprenophine is 30x as potent as morphine and butorphanol is 4-7x. What does this information tell you?
It takes less of both drugs to achieve the desired effect
Antagonist opioids
Naloxone and Nalmefene
Reversal agent for all opioid cases→ overdose and impending arrest
Antagonist opioid precautions
Acute awareness of pain → sympathetic surge
Partial reversal difficult
Analgesia options limited after reversal
Phenothazines (acepromazine) uses
Dopamine receptor antagonist → sedation
Major tranquilizer
Antiemetic, antihistamine and antiarrhythmic
Acepromazine precautions
↓ PCV (sequestration of RBCs) → avoid in patients with anemia, blood loss and plate dysfunction
Patients with MDR1 mutation
Benzodiapepines
Diazepam, midazolam
Benzodiazepine uses
Anxiolytic
Enhance GABA and GABAa receptor
Mild sedation (minor tranq)→ young, old critically ill
Anticonvulsant
Skeletal m. relaxation
Benzodiazepines are reversed with ___________
Flumazenil
Benzodiazepine precautions
No analgesia
Not effective sedation in normal healthy patients
Caution with hypoproteinemic patients
Avoid patients with severe hepatic dz
Alpha-2 agonists
Demedetomidine, medetomidine, xylazine, detomidine, romifidine
Alpha-2 agonists uses
Profound sedation (major sedative)
Analgesia → short duration of action
M. relaxation
Dexmedetomidine precautions
Cardiovascular effects- biphasic effect on BP and significant bradycardia
Inhibits ADH and insulin release
Appear unconscious but aren’t
Alpha-2 agonists/ antagonists
Medetomidine, Vatinoxan hydrochlorides
IM injection
Onset- 5-15 min, duration 45 min
Medetomidine
Central and peripheral effects
Provides sedation and analgesia
Vatinoxan hydrochlorides
Alpha-2 antagonist (peripheral effect only)
Don’t cross BBB, affect sedation or analgesia
Alpha-2 antagonists
Atipamezole
Yohimbine and tolazoline
Atipamezole
Competitive reversal for dexmed and medtomidine
IM only
10x more concentrated than dexmed and 5x than metom
When shouldn’t you use atipamezole?
Patient under general anesthesia→ hypotension and cardiovasc collapse
Post-op unless medical reason
Yohimbine and tolazoline
Competitive reversal for xylazine
Administered slowly IV diluted with saline
Anticholinergics
Atropine and glycopyrrolate
Anticholinergic MOA
Block acetylcholine @ muscarinic receptors
Anticholinergic uses
Tx sinus bradycardia or AV block
Tx ainoatrial arrest (atropine)
Anticholinergic precautions
↓ salivation but ↑ viscosity
Arrhythmogenic
T/F: routine use of anticholinergics is no longer recommended
TRUE
unless patients < 12 wks
