11 – Alpha2-Agonists Clinical Application Flashcards
(38 cards)
1
Q
What are the many applications of alpha2 agonists in vet med?
A
- Pre-medication
- Sedation for minor procedures
- Infusion intra- and post- operatively
- Sedation in recovery period
- Adjunct for local blocks
- Epidural administration
2
Q
Premedication: small animals example
A
- Dexmedetomidine
3
Q
Dexmedetomidine: premedication for small animals
A
- Highly selective for alpha 2 receptor
- Excellent sedative for healthy exotics
- Always combine with an opioid for more reliable results
- Quality of sedation is profound, but can overrride
4
Q
if IV administration of dexmedetomidine (premed for small animals)
A
- Decrease dose by half
5
Q
Dexmedetomidine dose dependent CV and respiratory depression: choose dose based on number of factors:
A
- Patient temperament
- Hydration status
- Anticipated pain levels of procedures
6
Q
Dexmedetomidine onset of action (IM)
A
- 15mins
7
Q
Dexmedetomidine duration of action
A
- 45mins to 1hr
8
Q
Dexmedetomidine reversable available
A
- Atipamezole
9
Q
Premedication: large animals example
A
- Xylazine
10
Q
Xylazine (premedication large animals)
A
- Horses, ruminants, camelids
- Excellent sedative for healthy patients
- Quality of sedation=excellent
- Reflex bradycardia profound but transient
- *can be reversed if necessary (RARE)
- **does for ruminants is lower=more sensitive
11
Q
Xylazine (premedication large animals): onset of action
A
- Minutes
12
Q
Xylazine (premedication large animals): duration of action (IV)
A
- 30-45 mins
13
Q
Premedication: horses example
A
- Detomidine
14
Q
Detomidine (premedication in horse)
A
- Good quality sedation: may be slight more ataxic/depressed then with xylazine
- Onset and duration similar to xylazine
15
Q
Sedation for minor procedures; small animals example
A
- Dexmedetomidine
16
Q
Dexmedetomidine (minor procedures in small animals)
A
- Profound sedation for minor procedures (quill removal, laceration repair)
o Even more with IV (place catheter for ‘top ups’ to be easier) - Combine with opioid to improve quality of sedation
- Combined with local block if possible
17
Q
Dexmedetomidine (minor procedures in small animals): reversible
A
- Get rid of drugs once procedure is complete
18
Q
Sedation for standing procedures: large animals example
A
- Xylazine
- Detomidine
19
Q
Xylazine (sedation for standing procedures): horses
A
- Teeth floats, minor lacerations
- Feet firmly planted, but can still kick!
- Often combined with BUTORPHANOL
20
Q
Xylazine (sedation for standing procedures): cows
A
- Foot trims
- Combine with BUTORPHANOL
- Will result in recumbency in 15mins
- Duration of action: 60mins
- *reversible with Tolazoline IM (avoid excitement)
21
Q
Detomidine (sedation for standing procedures)
A
- Often combined with opioid (BUTORPHONAL)
- Longer standing procedures=make up infusion and administer to effect
o Laparoscopic ovariectomy
o Rectovaginal fistula
22
Q
Dexmedetomidine: infusion during surgery
A
- *anesthetic sparing and analgesia
- Be aware of bradycardia with bolus
- More effective when combined with an opioid infusion (Fentanyl/Remifentanil)
- Not commonly administered to cats as an infusion
- *very beneficial in horses (less used in dogs and cats)
23
Q
Dexmedetomidine: infusion during post-operative period
A
- *analgesia and sedation
- Indications
o Anxious dogs
o Fractious dogs
o Painful dogs (need something more than an opioid)
24
Q
Dexmedetomidine: addition to local anesthetic
A
- *prolongs duration of block
- Mix with local anesthetic and administer in same syringe
o Amount is small - Some systemic uptake=may see increased levels of sedation
25
Mechanism of action with dexmedetomidine + local anesthetic
- Vasoconstriction associated with alpha2 agonist DELAYS clearance of local anesthetic from the site
26
Dexmedetomidine in epidurals: small animals
- Not routinely used
- Direct neurotoxic effects have not been fully tested
27
Dexmedetomidine in epidurals: large animals
- Prolongs duration of blockade
- Easily accessible for practitioners
- Does NOT produce motor blockage
- Often combined with local anesthetics or opioids
- Produce analgesia
- Adverse effects (ataxia, recumbency): can be reversed
- Systemic absorption occurs: CAUTION
28
Xylazine in epidurals: horses
- Provide 2.5 hours of perineal analgesia
- No hind limb ataxia 1/5th the dose typically given systemically
- *if combined with lidocaine=do NOT exceed 10mL
o More volume you put in=further it will spread
29
Detomidine in epidurals: horses
- Potent analgesic AND sedative effects
- Sedation, ataxia, recumbency, and CV effects can occur
- Use low doses
- Analgesia will spread cranially
- Duration is shorter than xylazine: 2 hours
- Diuresis occurs
30
Romifidine in epidurals: horses
- Analgesia inconsistent: if works=4hrs of analgesia
- Spreads cranially similar to detomidine
- Sedation, bradycardia and decreased RR has been reported
31
Xylazine alone in epidurals: cattle
- Onset of action: 10mins
- Duration of action: 3-4hours
32
Xylazine combined with lidocaine in epidurals: cattle
- Onset of action: 5mins
- Duration of action: 6hrs
33
Side effects of xylazine +/- lidocaine in epidurals: cattle
- Mild to moderate sedation
- Mild ataxia
- Decreased ruminal motility
- Bradycardia
34
Romifidine in epidurals: cattle
- Analgesia and sedative effect=dose dependent in intensity and duration of action
35
Specific breed/species considerations
- Bradycephalics and animals with laryngeal paralysis
- Blocked cats
- Diabetic implications
- *UNEXPECTED AROUSAL: do NOT trust it!
36
Bradycephalics and animals with laryngeal paralysis considerations
- Beware of use
- Pharyngeal and laryngeal MUSCLE RELAXATION may further impair compromised airway
- *DECREASED ESOPHAGEAL SPINCTER TONE=increased risk of regurgitation
37
Blocked cats considerations
- MUSCLE RELAXATION may aid in passage of urethral catheter
38
Diabetic implications: considerations
- Reduced insulin leads to increased hepatic glycogenolysis and gluconeogenesis causing HYPERGLYCEMIA
- Clinical relevance: minimal (can manage hyperglycemia and they will be hyperglycemic due to stress)
