Preanesthetic Agents Flashcards by Trenni Jefferson

Intramuscular

Stressed or excited patients
Allow 15-30 min for max effect
Muscle location important

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Intravenous

Place IV catheter first
Allow 3-5 min max for effect

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T/F: SQ not recommended for premedication

TRUE

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Subcutaneous

Less vascular supply= slow rate of absorption
Uptake of drug is dependent on tissue perfusion
Lead to patchy absorption (drug dependent)

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Most adverse drug effects are associated with _________

High drug doses

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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

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Medication for pre-hospital sedation

Gabapentin and Pregabalin
Trazodone

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Gabapentin & Pregabalin MOA

Binds to alpha 2 delta subunit or voltage dependent channel in CNS
↓ the release of glutamate , dopamine, NE, and serotonin

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Gabapentin & Pregabalin uses

High doses= sedation
Adjunct analgesia or neuropathic pain

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Trazodone MOA

Serotonin antagonist and reuptake inhibitor
Histamine antagonist and alpha-1 adrenergic antagonist

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Trazodone uses

Sedation and anxiolysis within 1-2 hours

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Caution of trazodone

Combining with SSRI, TCA, or MAOIs = serotonin syndrome

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Chill protocol for pre-hospital sedation

Gabapentin night before visit
Gaba and melatonin 1-2 prior to appointment
Acepromazine admin 30 before appointment

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Pre-anesthetic drug classes

Antiemetics
NSAIDs
Opioids
Phenothiazines
Benzodiazepines
Alpha-2 agonists
Anticholinergics

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Antiemetic medications

Maropitant and Ondansetron

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Maropitant (Cerenia)

Neurokinin (NK1) receptor antagonist
SQ or IV 45 min- 1 hr before premed
PO 2 hr before premed

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Ondansetron (Zofran)

5-HT3 (serotonin type 3) receptor antagonist
IV, IM, SQ, PO
30 min before or with premeds

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T/F: antiemetics will not decrease the incidence of gastroesophageal reflex (GER)

TRUE

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What are NSAIDs used for?

Mild to moderate inflammatory pain
Onset time: 30-60 minutes

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FDA approved NSAIDs in dogs

Carprofen, meloxicam and robenacoxib

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FDA approved NSAIDs in cats

Meloxicam, robenacoxib

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Precautions of NSAIDs

GI toxicity: excessively high dose, two NSAIDs @ the same time, conjunction with corticosteroids
Hypoalbuminemia
Metabolism in cats (deficiency glucoronyl transferase enzymes)

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NSAID contraindications

Pre-existing hypotension, hypovolemia or renal dz
GI procedures

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Opioids MOA

Bind to opioid receptors located @ presyn. and postsyn. sites in the CNS and peripheral tissues (mu, kappa, delta)

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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*