Field Anesthesia Flashcards
IV anesthesia is safely used for how long in horses?
Up to 1 hour
What are the contributing factors for mortality from anesthesia in horses?
Age
Duration of surgery
Drugs used for sedation
Inhalants
Preanesthetics must induce:
a state of calmness
What two arrhythmias are common in horses?
AV Block (1st and 2nd)
A-fib
What is an acceptable amount of time to fast a horse before anesthesia?
4-6 hours in general
Some need up to 24-48 hours
What are the three commonly used groups of anesthetics used for standing sedation and premedication?
Alpha2- agonists
Phenothiazines
Opioids
The two most common Alpha-2s used are:
Xylazine, Detomidine
Alpha-2 agonists cause 3 main effects, which are:
Sedation
Muscle relaxation
Analgesia
Peak effect of alpha-2 agonists occurs _____ minutes after IM injection or _____ minutes after IV injection
10-15 minutes; 3-5 minutes
T/F: Xylazine is more potent than Detomidine (Dormosedan)
FALSE
Dorm is more potent
Two of the main side effects of using Alpha-2s for sedation is:
Colic (GI dysmotility)
Increased urination
What are the potential reversal agents for Alpha-2 agonists?
Yohimbine, Atipemazole, Tolazoline
What should you always hold onto for horses sedated with alpha-2s?
The Halter
Oral detomidine takes how long to kick in?
~45 minutes
What is the protocol for delivering a Detomidine CRI for standing sedation procedures >20 minutes (lacerations, laser surgery, thoracoscopy) for a 1,000 lb. horse?
- 3mg Detomidine IV
- 12mg Detmodine in 250mLs NaCL
- Adjust rate up or down as needed throughout procedure
The most common phenothiazine used in horses is:
Acepromazine
What are the characteristics of using Acepromazine as sedation in horses? (4)
- Onset 15-30 minutes
- Duration 6-10 hours
- Minimal muscle relaxation & ataxia
- No analgesia
What are the potential side effects of using acepromazine?
-Priaprism (caution in breeding stallions)
-Hypotension
Which sedative class is more effective when used in conjunction with dissociatives?
Alpha-2 agonists
What are the 3 main opioids used in equine sedation protocols?
Butorphanol
Morphine
Transdermal Fentanyl
Why do we give opioids in addition to tranquilizers?
Opioids can cause excitement when given alone
What are the common drugs/classes used for induction and total IV anesthesia (TIVA)?
Dissociatives (Ketamine, Telazol)
Benzodiazepines (Midazolam, Diazepam)
Propofol
Which drug class causes muscle relaxation during induction and TIVA?
Benzodiazapines
Use of dissociatives results in a smoother induction and recovery when used in conjunction with:
Alpha-2 Agonists
The duration of Ketamine/Alpha-2 anesthesia is approximately:
15-20 minutes
When giving Xylazine and Ketamine together, the dose should be ______ IV for Xylazine and ______ IV for Ketamine
1 mg/kg (2 mg/kg if IM)
2 mg/kg
Adding what drug to xylazine and ketamine causes smoother induction & more muscle relaxation?
Diazepam
(0.02-0.1 mg/kg IV)
What is a potential negative side effect when using Telazol for anesthesia?
Prolonged/rough recovery when used with Xylazine
Telazol is the brand name for the combination of which two drugs, and what is the appropriate dosage?
Tiletamine & Zolazepam
1-2 mg/kg IV
TKD is short-hand for:
Telazol-Ketamine-Detomidine
How do we prepare TKD for anesthesia and what is the dose?
-Reconstitute Telazol powder with 4mL Ketamine and 1 mL Detomidine
-3mL/550 kg horse
What is the onset/recovery time for TKD?
Recumbency in 1 minute; sternal in 36 minutes/standing in 40 minutes
T/F: TKD alone is sufficient anesthesia for surgery
FALSE
Do not use alone for surgery
What are the “muscle relaxant” drugs/drug classes?
Guaifenesin
Benzodiazepines
Guaifenesin does not induce _____ and has no _____
Unconsciousness, analgesia
What are the signs of Guaifenesin overdose (~200 mg/kg)?
Extension of forelimbs
Labored breathing
Resp/cardiac arrest
What are the two main benzodiazepenes used in horses?
Diazepam, Midazolam
When are Benzodiazepenes used alone?
Young foals
Which Benzo is appropriate for IM use?
Midazolam- water soluble
Propofol is often limited in equine medicine because:
COST (need large quantities)
What limits the usefulness of Propofol in the field?
Respiratory depression
What other drugs can decrease the dose needed of propofol?
Guaifenesin, Ketamine
What are the best methods to prolong xylazine/ketamine anesthesia?
- Give 1/3 to 1/2 xylazine and ketamine
- Add Guaifenesin/Ket or GKX
- Use Detomidine first instead of xylazine
- Give 1/4-1/2 ketamine & valium
What is a “Triple Drip?”
Guaifenesin
Ketamine
Xylazine
How do we make a “triple drip” solution?
1L 5% Guaifenesin + 500mg xylazine + 1-2g Ketamine
When is triple drip most commonly used?
Induction in foals
Signs of triple drip overdose is most similar to:
A horse in light anesthetic plane
Why is it important to remove a halter during anesthesia?
Avoid facial nerve paralysis
What 3 eye signs can indicate a light plane of anesthesia?
Brisk palpebral
Tearing
Occasional nystagmus
As a horse gets lighter in their anesthetic plane, their HR ______ while respiratory rate _______
HR remains static, RR becomes more rapid and forceful
Healthy horses can tolerate hypoxia for up to:
45-60 minutes
Most injuries during anesthesia occur during __________, and injuries are more common when:
Induction/Recovery
Horse tries to stand too early
Techniques for recovering a horse in the field:
-Remove debris
-Tail assist
-Good footing
-Cover eyes with cloth
-Cotton in ears
-Prevent horse from gaining too much momentum
