Field Anesthesia and Chemical Restraint Flashcards
T/F: recumbency is required for short surgical procedures
true
IV anesthesia can be safely used for up to ____ hr.
1
Mortality rate in horses undergoing anesthesia is higher. What are the 4 contributing factors?
- age (foals, older)
- duration of surgery (>3 hr risky)
- drugs used for sedation
- inhalants
Preanesthetics MUST induce …
a state of calmness
You should NEVER anesthetize an excited horse!! If you’ve given pre-sedation and the horse is still excited, then give something else prior to induction/anesthesia.
Pre-anesthetic physical examination should focus on what 2 body systems and why?
respiratory and cardiovascular.
This is because 1) subclinical respiratory disease can become overt after anesthesia and 2) You should ensure you are aware of any arrhythmias and murmurs (and ensure HR is >20)
How long should horses be fasted prior to undergoing anesthesia?
4-6 hours for adults
some surgeries require 24-48 hr (ex. laporoscopic cryptorchid)
What are 3 commonly used drug groups for standing sedation and premedication?
- alpha-2 agonists (xylazine, detomidine)
- phenothiazines (ace)
- opioids
Which of the following statements is FALSE about alpha-2 agonists?
A. they can be administered PO, IM, or IV
B. they produce sedation, muscle relaxation, and analgesia
C. they increase HR and CO which can lead to first and second degree AV blocks
D. peak effect is in 3-5 min (IV) or 10-15 min (IM)
E. they can decrease GI motility
F. they increase urination
G. they are reversible
C. they increase HR and CO which can lead to first and second degree AV blocks
they DECREASE heart rate and cardiac output, which can lead to 1st and 2nd degree AV blocks
How do you know when a horse is adequately sedated with pre-meds?
they assume the 5-point stance
head is down, eyelids and lips are droopy
T/F: detomidine is more potent than xylazine and therefore is a better drug
false – it is more potent, but it is not necessarily a “better” drug. Higher potency simply means that less is required to achieve the same effects.
what are the reversal agents for alpha-2 agonists?
- yohimbine
- atipamazole/ antisedan
- tolazoline
Detomidine can be given orally in applesauce, molasses, or alone but it takes ______ to take effect.
45 min
Which of the following statements is FALSE about a phenothiazine (acepromazine) as a pre-medication?
A. it can be given PO, IV, or IM
B. it produces a calming, relaxing effect, but horse can still be rousable
C. can create hypotension
D. onset is 5-10 minutes, duration is 6-10 hours
E. it produces very minimal muscle relaxation or ataxia
F. it does not provide analgesia
G. when combined with alpha-2 agonist, can enhance sedation
D. onset is 5-10 minutes, duration is 6-10 hours
onset is actually 15-30 minutes, duration is 6-10 hrs
Why are opioids (butorphanol, morphine, TD fentanyl) used in conjunction with tranquilizers such as xylazine?
When opiods are given alone, they can cause excitement.
Why are dissociatives like ketamine used as induction agents in horses?
their onset is rapid and the induction and recovery are very smooth if used with alpha-2’s (xylazine, detomidine)
T/F: ketamine should only be given IV
true
T/F: you should combine xylazine and ketamine in the same syringe when using them in conjunction for induction
false
give xylazine first, then ketamine.
Which of the following statements is TRUE about the xylazine + ketamine combination?
A. good muscle relaxation is achieved
B. tachypnea is common but resolves within the first 5 minutes
C. Adding diazepam provides smoother induction and greater muscle relaxation
D. major surgeries can be performed with this combo alone
C. Adding diazepam provides smoother induction and greater muscle relaxation
A is false because ket + xylazine alone has poor muscle relaxation
B is false because ket + xylazine can actually cause apneustic breathing
D is false because only minor surgeries should be performed with this combo
When using telazol (tiletamine/zolazepam) + xylazine, why are the recoveries “rough” or prolonged?
How could you improve this?
The xylazine is already gone and they are recovering off of the dissociative.
To improve that, you can used detomidine + telazol because detomidine lasts longer than xylazine.
what is the BEST / smoothest drug protocol for laying a horse down in the field?
xylazine + ketamine
T/F: TKD will induce recumbency in 1 minute and the animal will be back standing in 40 minutes. The combination is ideal because it requires less of each drug. However, this combo should not be used alone for surgery.
true
What are the benefits / purpose of use of Guaifenesin?
GG is a muscle relaxant.
It does not induce unconsciousness or analgesia and should not be used alone.
BUT, it allows for other drug amounts to be decreased.
What are the signs of GG overdose?
- extension of forelimbs
- labored breathing
- respiratory and cardiac arrest
it looks like the horse is “getting light”
What is the purpose of adding diazepam or midazolam into your anesthetic protocol?
provides additional muscle relaxation in conjunction with other agents.
It should NEVER be used alone.
T/F: there is not really any difference between midazolam and diazepam in terms of their effectiveness.
true
Propofol can be cost-prohibitive in horses due to the large volume required to achieve effect. What can you combine propofol with to reduce the dose required?
guaifenisin or ketamine
but note that respiratory depression still limits usefulness of propofol in the field.
To prolong xylazine/ketamine anesthesia, what are 4 potential options to add to the protocol?
- give 1/3-1/2 orginal dose of xylazine and ketamine
- add guaifenisin/ket or GKX
- use detomidine instead of xylazine (from the beginning)
- give 1/4-1/2 ketamine and diazepam
what is included in “triple drip”?
(give amounts of each too)
1 L of 5% guaifenisin or x amt of midazolam
500 mg xylazine
1-2 grams ketamine
Triple drip can be used to induce or maintain anesthesia safely for up to _____.
1 hr
but you should give supplemental oxygen if surgery is longer than 30 min.
Monitoring can be challenging for non-hospital situations. What are the most important components of monitoring for field anesthesia?
- provide proper padding, remove halter, protect eyes
- use IV catheter if doing TIVA
- All TIVA agents should be administered “to effect” (brisk palpebral, tearing, occasional nystagmus present)
- provide muscle relaxation
- digital pulse palpation, CRT, and MM color
- observe respiratory rate and rhythm
why is respiratory rate MORE reliable indicator of changing planes of anesthesia than heart rate is?
heart rate changes very little in horses during changing planes of anesthesia, whereas respiratory rate will become rapid and forceful as the horse gets lighter.
T/F: all recumbent horses are hypoxic to some degree
true
however, healthy horses can tolerate this hypoxia for short periods (45-60 min), oxygen supplementation should be provided to compromised patients.
When do most injuries occur during horse procedures?
during induction and recovery
especially if the horse is trying to stand early, so you must combine physical and chemical restraint methods to slow this process and protect them.
