Lesson 27 - Anesthesia in Ruminants

What are the most used techniques for restraining large ruminants?

1. halter

2. tail raising or leg tie

3. casting

4. mechanical

What are the restraining methods for small ruminants?

1. standing restrain

2. lie down/sitting restraint

What is the acclimation period for small ruminant restraint?

3 days prior to sedation/anesthesia

What are subclinical diseases that can affect anesthesia in small ruminants?

1. pulmonary disease

2. anemia

What pulmonary diseases do small ruminants have?

1. parasites

2. lentiviruses

3. OPA

What causes anemia in small ruminants?

haemonchus contortus

What subclinical diseases do bovines have?

1. electrolyte imbalance

2. mastitis

What electrolyte imbalances do bovine have?

ketosis

What is the concern with mastitis?

endotoxemia

What are the signs of bloat?

1. left sided distension

2. drum-like sound when tapping left flank

3. stop grazing

4. respiratory distress

What are specific considerations for ruminants anesthesia?

1. eructation

2. salivation

3. regurgitation

4. heavy GI signs

5. rumen bloating

How can increase rumen content affect a patient during anesthesia?

increase intra-abdominal pressure which compresses diaphragm and major vessels causing hypoventilation and hypotension and V/Q mismatch

What are the types of anesthesia we can do for ruminants?

1. loco-regional anesthesia

2. general anesthesia

Why do we do locoregional anesthesia for ruminants?

with a touch of sedation because ruminants tend to assume sternal recumbency

What are the risks with general anesthesia in ruminants?

1. risk of bloating

2. risk of regurgitation

3. risk of aspiration

What premedications can be used for ruminants?

1. acepromazine

2. opioids

3. benzodiazepines

What is important about acepromazine for ruminants?

1. rarely used

2. not approved for food producing animals in us

3. mild sedation with prolonged duration

What are the side effects of acepromazine in ruminants?

1. relaxes cardias increased risk of regurgitation and aspiration

2. penile prolapse in bulls

What opioids are used for ruminants?

1. butorphanol

2. buprenorphine in small

What are the indications for opioids for ruminants?

combined with benzodiazepines and alpha 2 agonists for quality sedation and sedation in sick animals

What is important about opioids in ruminants?

1. not approved in us for food animals

2. high dose causes behavioral changes and tachycardia and excitation

What is important about benzodiazepines for ruminants?

1. not approved in us for food animals

2. muscles relax

3. no cardiopulmonary depression

4. sedation is dose and route dependent

What is midazolam used for in goats?

1. sedation without sternal recumbency

2. hypnosis when given IV

What is important about xylazine?

1. ruminants 10 times more sensitive than horses

2. different doses give sedation with or without recumbency

What are the side effects of xylazine in ruminants?

1. reduced GI motility

2. decreased heart rate and AV blocks

3. hyperglycemia

4. diuresis

5. oxytocin-like effect

What is important about detomidine?

more selective than xylazine, less prone to recumbency, oxytocin-like effect less pronounced

What are the clinical signs of sedation in ruminants?

1. head down

2. ptosis

3. excessive salivation

4. ataxia

5. sternal and lateral recumbency

What drugs lead to pulmonary edema in ruminants?

alpha 2 agonists

How do alpha 2 agonists cause pulmonary edema?

1. increase airway resistance due to bronchospasm

2. pulmonary hypertension

3. activation of pulmonary macrophages

4. pulmonary alveolar damage

5. pulmonary edema

What are the symptoms of pulmonary edema in ruminants?

1. severe and sustained hypoxemia

2. cyanosis

3. fatal respiratory failure

How do we treat pulmonary edema in ruminants?

1. oxygen administration

2. atipamezole

How do we prevent pulmonary edema in ruminants?

vatinoxan which is a peripherally acting alpha 2 antagonist

What veins are used in ruminants?

1. coccygeal vein and artery

2. auricular vein and artery

3. jugular vein

4. cephalic vein

5. saphenous vein

6. milk vein

What are the cornerstones of analgesia for ruminants?

1. preemptive analgesia

2. multimodal analgesia

3. balance analgesia

What are the five classes of drugs used for preoperative analgesia in ruminants?

1. NSAIDs

2. local anesthetics loco regional techniques

3. alpha 2 agonists

4. ketamine

5. opioids

What are the head blocks used in cows for dehorning?

1. cornual nerve

2. cutaneous branches of II cervical nerve

What are the head blocks used in small ruminants for dehorning?

1. lacrimal nerve

2. infratrochlear nerve

What are the indications for lumbosacral and caudal epidural anesthesia?

1. uterine/rectal prolapse

2. dystocia correction

3. perineal urethrostomy

4. orthopedic

What are the approaches for lumbosacral and caudal epidural anesthesia?

1. lumbosacral epidural L6-S1

2. caudal epidural S-Co1 and Co1-Co2

How do you locate the space for the caudal epidural anesthesia?

palpation during vertical movements of the tail

What are the indications for inverted L block?

1. laparotomy

2. desensitization of nerves supplying the surgical field

What drug is used for inverted L?

lidocaine and epinephrine

What are is the inverted L administered?

paralumbar fossa

What are the disadvantages of inverted L?

only superficial structures numbed

What nerves are blocked for paravertebral block for complete anesthesia of the flank?

T13-L3

What are the approaches for paravertebral blocks?

distal and proximal

What is the indication for the BIER block?

anesthesia of distal limb, draining abscess, claw amputation, digits surgery

What are the advantages of bier block?

simple, rapid onset, muscle relaxation

What are the disadvantages of bier block?

position in lateral recumbency, possible hematoma, limited duration, damage of nerves under tourniquet, local anesthetic toxicity

What is the preferred surgical protocol for ruminants?

standing with local or regional anesthesia

What technique is used for dosing sedative for standing ruminant procedures?

5-10-20 technique (butorphanol, xylazine, ketamine)

What are field anesthetic surgeries missing with ruminants?

1. no airway protection

2. no oxygen supplementation and ventilation

What do we administer to help maintain airway protection in ruminant field anesthesia?

ketamine

What are the fasting protocols for ruminants?

hay 36 hours, grain 24 hours, water 12 hours

Why do we want to fast ruminants?

reduce volume of the rumen causing less pressure on the diaphragm and limits gas formation leading to less risk of bloating

What are the side effects of fasting?

increase vagal tone which decreases heart rate

Which ruminants do you not want to fast?

pre-ruminant (

What are the effects of right lateral recumbency?

increase pressure on lungs and big vessels leading to V/Q mismatch and decrease venous return

What is right lateral recumbency used for?

access to the rumen for trocarisation

What are the effects of left lateral recumbency?

less access to rumen but better V/Q mismatch and venous return

What are the induction drugs used for ruminant?

ketamine and guaifenesin

What are the uses of guaifenesin?

1. double drip

2. triple drip

3. induction

4. maintenance

How do we prepare for endotracheal intubation?

wash the mouth before sedation

What ruminants are prone to laryngospasm?

sheep and goats

When do you not want to attempt endotracheal intubation?

if anesthesia is too light wait for gag reflex suppression

What do you do if regurgitation occurs during esophageal intubation?

leave the ETT in esophagus, place another ETT in the trachea, remove the original ETT

How do you intubate small ruminants?

1. extend the head and neck 180 degrees

2. topical lidocaine spray

3. insert a stylet and slide the ETT over the stylet

How do you intubate cows?

digital palpation of the epiglottis with mouth held open with retractor

When is inhalation a good anesthesia maintenance option for ruminants?

long procedures

When is TIVA a good anesthesia maintenance option for ruminants?

simple and field procedures

What do you need to consider when positioning ruminants for surgery?

1. myopathy and neuropathy

2. bloating and hypoventilation and regurgitation

What do you use to prevent myopathy and neuropathy during surgery?

mats, inner tube, and H block

How do you prevent bloating, regurgitation, and hypoventilation during surgery?

1. fasting

2. head and body positions

3. suctioning saliva

How do you detect anesthesia depth in bovine?

changes in eyeball position

How do you detect anesthesia depth in sheep and goat?

changes in pupillary size

How do you know if a bovine is at a surgical plane of anesthesia?

rotate ventrally to where only sclera is seen

How do you know if a sheep or goat is at a surgical plane of anesthesia?

squared central pupil no palpebral reflex

How do we deal with saliva production?

1. position and suction

2. anticholinergic agent but not used routinely because makes saliva thick

Why does bloat happen during anesthesia?

gas is still being produced from bacteria in GI but eructation is suppressed

What is the effect of right lateral recumbency?

worst position because rumen can expand freely

What is the effect of left lateral recumbency?

rumen can't expand freely but less access to the rumen

How do we treat intra-operative bloating?

1. positioning by elevating front end

2. stomach tube

3. trocarisation

4. rumenotomy

5. anti-foaming agents

What causes dose dependent respiratory depression in ruminants?

inhalants

What level is diagnostic for hypoventilation under anesthesia?

EtCO2 >60 mmHg

What is the treatment for hypoventilation under anesthesia?

check anesthetic depth and institute mechanical IPPV

What is the heart rate for adult sheep, goats, and calves?

85-120 bpm

What is the heart rate for adult cattle?

70-90 bpm

What is the invasive blood pressure of ruminants?

mean 75-100 mmHg, diastolic 60-80 mmHg

What do we need to maintain in order to maintian perfusion?

cardiac output

What is the treatment for hypotension?

1. reduce anesthetic depth

2. bolus of fluid IV

3. epinephrine CRI

What is recovery like for ruminants?

patient and stay sternal recumbency until awake and functional

What do we need for ruminant recovery?

1. left lateral or sternal recumbency to discourage bloating

2. pad under the head below the larynx to keep it lifted

3. best friends present when they wake up

4. good footing and calm environment

Why is pain assessment difficult in ruminants?

prey animals so they stay stoic

What is good analgesia protocol?

preemptive treatment using local regional techniques