Anesthesia - Final: Take the Pain Away

What is the mortality rate of horses in elective anesthesia?

1 in 100 (high)

What is the side effect of Ace?

Hypotension by alpha 1 blockade (bad for stallions since can't retract)

What category of drugs provide reliable analgesia, sedation, and muscle relaxation in horses?

Alpha 2 agonists

T/F: Sedation lasts longer than analgesia in alpha 2 agonists

True, be careful

What are the main side effects of Alpha 2's?

AV block

Resp depression

Decreased cardiac output

What alpha 2 has horses hold up their heads better during sedation?

Romifidine

What is a concern of opioids in horses?

GI stasis --> colic

What is an advantage of detomidine over other alpha 2 agonists?

More stable

What is the most commonly used induction agent in horses?

Ketamine

What is the major disadvantage of telazol?

Rough recovery

What is the main side effect of propofol?

Hypotension

What is propofol combined with for induction for better sedation and recovery?

Ketamine

What is the central acting muscle relaxant used in triple drip?

Guaiphenesin

What drugs are combined in triple drip?

Ketamine

Xylaxine

5% guaifenesin

Mortality rates increase significantly after how long under anesthesia?

3 hours

Local anesthetics other than what can be cardiotoxic and should not be administered IV?

Lidocaine

Give the local anesthetics in order of duration (short to long)

Lidocaine (1 - 2)

Mepivacaine (2 - 4)

Bupivacaine (4 - 8)

Blockage of what nerve over the zygomatic arch allows for a motor block of the eyelid?

Auriculopalpebral (no analgesia)

Blockade of which nerve accessed through a small foramen dorsal to the orbit results in anesthesia of the upper eyelid in horses?

Supraorbital

How can we provide local anesthesia for castration?

Inject lidocaine into the balls

What is necessary to prepare a horse of anesthesia?

PE

Clin path

Catheter

Remove shoes

Pick feet

Rinse mouth

What are the common sites for an IV catheter?

Jugular

Lat thoracic

Cephalic

T/F: When a horse is getting light, you should turn up the gas first

False, too big a time constant means injectable should be first

How can we measure depth of anesthesia?

Muscle tone

Palpebral

Nystagmus (faster = lighter)

What electronic monitors are used in equine anesthesia?

ECG

BP (arterial line)

ETCO2

Blood gas

What synthetic catecholamine is a beta agonist that increases cardiac output, commonly used for support in horses?

Dobutamine (preferred in horses over dopamine)

What are horses prone to when laying down?

Muscle compression

What is the goal when lying down a horse when referring to the position?

What ever the horse looks like standing up, aim to keep it in that "neutral" position, and pull the down legs forward

What are the common sedatives given during recovery and why?

Alpha 2's or ace, to reduce crashing and injury

What are the methods of recovery?

Free recovery (just get up)

Special recovery (ropes, air pillow, pool)

Why does myopathy occur after general anesthesia in horses?

Ischemic muscle damage due to poor padding and hypotension, making it lame and rock hard

What measures can be taken to prevent

post-anesthetic myopathy?

Decrease duration

Padding

Proper positioning

If myopathy occurs, how is it treated?

Make horse stand

Give fluids

Mannitol

Why does neuropathy occur after general anesthesia in horses?

Prolonged recumbency and inadequate padding/position

What is the most commonly affected nerve for neuropathy?

Radial due to dropped elbow

What measures can be taken to

prevent post-anesthetic neuropathy?

Pull down limb forward

What condition of young, heavy horses affects the pelvic limbs, causing dog sitting and loss of deep pain?

Spinal Cord Myelomalacia

Give a quick difference between after surgery complications

Myopathy: Hard and swollen muscle

Neuropathy: Loss of sensation

Myelomalacia: Hind limbs loss of function

What are two muscle disorders that affect anesthesia?

Hyperkalemic Period Paralysis, where too much potassium needs to be lowered with dextrose (stimulates insulin) and,

Polysaccharide Storage Myopathy, where lots of CK indicates they use carbs and not fat for energy

What causes the release of of proinflammatory cytokines?

Endotoxemia from gram negative bacteria

What is the treatment of endotoxemia which binds the toxins?

Polymyxin B

What is the preanesthetic prep for ruminants?

Withhold food/water (small = 12 - 24 hr, large = 24 - 48)

Catheter (jug)

What vein should be catheterized in a llama?

Right jugular (it's deep, so right avoids esophagus)

What is the method for intubating small ruminants and llamas?

Sternal recumbency

Hyperflex head/neck

Visualize larynx

Insert stylet

Insert tube

What drug combination is used for caudal epidural?

2% lidocaine (1 ml/100 kg)

PLUS

Medetomidine (15 mcg/kg)

OR

Xylazine

Where is the lumbosacral epidural space located?

Between the dorsal iliac spines and between lumbar spinous process and sacral spines

With lidocaine, how much do you need to reduce the dose for subarachnoid analgesia in a lumbosacral epidural?

35 - 50%

What nerve block is used for standing laparotomy or LDA?

Paravertebral nerve blocks (T13 - L2)

What paravertebral nerve block blocks nerves before they branch out, and thus only requires one block?

Proximal paravertebral nerve block

What are the pros of paravertebral nerve blocks?

Reduced volume

Uniform anesthesia

Decreased abdominal pressure

What are the cons of paravertebral nerve blocks?

More likely to f*** up

What is a physical sign that your paravertebral nerve block was successful?

Scoliosis (bend toward injection cuz relaxed muscles)

What are the pros of Line and L block?

Cheap

Easy

Few side effects

What are the cons of line and L block?

Variable relaxation

Reduced area

High volume required (toxic)

T/F: Sensitivity to xylazine is 10x that in horses

True

What effect does xylazine have on urine output?

Increases 7x, so not used in urinary obstruction

What cardiac effects does xylazine have?

Bradycardia

Arrhythmia

Hypertension then hypotension

What effect does xylazine have in sheep?

Hypercapnia, hypoxemia, and pulmonary edema

What is the alpha 2 antagonist?

Atipamezole

You want to reduce recumbency and have your patient standing in 60 minutes. What drug combo you want?

Midazolam and Xylazine

You use Midazolam and Xylazine, but you want more muscle relaxation and longer duration of anesthesia. What drug you add?

Acepromazine

You want to induce sedation in a bull. What's yo drug combo?

Xylazine and Ketamine

What is the llama lullaby drug combo?

Xylazine

Butorphanol

Ketamine

What is the combination of bovine triple drip?

Xylazine

Ketamine

Guaifensin

What combination do you use for patients with increased anesthetic risk?

Midazolam and Ketamine

What analgesics should you give during induction of ruminants?

Butorphanol (with Midazolam)

and

Morphine (with Ketamine/Propofol)

You got an unruly cow that needs deep sedation, whatchu doin?

Telazol + Ketamine + Xyalazine

You can use a SA machine for inhalant anesthesia if they be <150 kg, but you gotta do what first?

Double that CO2 canister

Why might you put a tire under a cow that ain't awake?

Prevent radial nerve paralysis

T/F: Ruminants be salivating

True, keep that head down

T/F: Camelids be sensitive to fluid

Ture, don't fluid overload them

What should be given for recovery of ruminants?

100% oxygen

T/F: Swine are difficult to intubate

True, small mouth, long soft palate, dorsal tongue, etc.

What is a concern when intubating pigs?

Vomit (withhold food, avoid stress)

Where are IM injections given in pigs?

Base of ear (not hind legs)

Where are IV injections given in pigs?

On ear (use rubber band as torniquet)

What injectable anesthetics are combined for moderate sedation of pigs?

Midazolam and Butorphanol

What drugs are used for induction in pigs?

Xylazine and Ketamine

What drugs are used for deep sedation in pigs?

Detomidine + Butorphanol (Alpha2 + Opioid)

or

Morphine + medazolam

For shorter recumbency and time to non-responsiveness, like bandage change, you can give what?

Detomidine + Midazolam + Ketamine

Most induction for intubation uses what drug?

Mask inhalants

What drugs are used for intratesticular injection?

Xylazine and Ketamine

What are the post-op complications of pigs?

Hypoventilation

Hypotension

Hypothermia

You induce a pig and because of a mutation in the ryanodine receptor, there is a massive release of calcium, causing muscle contraction and rigidity, increasing body temp and CO2, depleting ATP, and causing arrhythmias and acidosis. This is what?

Malignant Hyperthermia

What is the goal for anesthesia?

To have warm, oxygenated, basic, circulating blood

What is the best indicator if a patient with cardiac disease is suitable for anesthesia?

Lack of exercise intolerance

Changes in what in the heart are most critical to drug selection?

Afterload (increased hurts valve, decreased = less blood)

What are we trying to balance when anesthetizing the heart?

Heart rate and blood pressure (keep whatever preanesthetic was)

What are the effects of anesthetics on the CV system?

Impair calcium utilization

Alter vascular resistance

Alter rate and rhythm

Develop intracellular acidosis

What drugs are contraindicated with CV compromise?

Sedatives like Ace and Alpha-2s

What induction agents are used for unstable cardiac patients?

Etomidate or benzo

What induction agents are used for stable cardiac patients?

Propofol or alfaxalone

What should be avoided systemically with valve disease?

Vasoconstriction (more afterload = more valve stress)

What pain management is highly useful in cardiac patients?

Opioids (minimal effect)

What drug should be avoided with valve disease?

Alpha 2 (increased afterload)

How should patients with DCM be induced?

Etomidate/benzo

What can be given as cardiac support for DCM?

Dobutamine

What drugs are avoided with DCM?

Ketamine

Ace

Alpha 2s

(Impair function or increase afterload)

T/F: In cardiac patients, lots of fluid is good

False, don't want to worsen pressure

With HCM (and other cardiac patients), we build the premed protocol around what drug?

Opioids