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Ruminant and Swine Anesthesia

Chapter 10

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Ruminant Anesthesia

Temperament and economics Ruminants don’t undergo general anesthesia as

often as horses and small animals Don’t require general anesthesia because of their

calm nature Many surgeries are performed using local or

regional anesthetic techniques and physical restraint

Must consider drug withdrawal times in food and milk-producing animals

General anesthesia in production animals is not often economical

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Ruminant Anesthesia (Cont’d)

Equipment Special equipment is needed because of their size Tilt tables, head gates, hoists, transporters Small animal equipment can be used for small

ruminants (lambs and kids) Anatomy and physiology

Ruminants produce more saliva, which can be aspirated during anesthesia

Ruminants are prone to regurgitation and bloat during general anesthesia

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Patient Preparation

Use the same principles as with small animals Assess, prepare, and weigh the patient Make sure the patient is fasted to prevent bloat Prepare equipment for and place IV catheter Calculate the volume of each agent to give including fluid

administration rates Review the oxygen flow rates Prepare equipment required to administer drugs and fluids,

equipment for endotracheal intubation, and monitoring equipment

Assemble and test the anesthetic machine and ventilator

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Selecting an Anesthetic Protocol

Factors to consider Minimum patient database Patient physical status class Type and duration of procedure

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Ruminant General Anesthesia

Equipment preparation Make sure all equipment is present before

induction begins Check circle system and ventilator of the

anesthetic machine Make warming equipment available for small

ruminants and calves Crash cart for emergency drugs and equipment

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Ruminant General Anesthesia (Cont’d)

Premedication or sedation Tranquilizers are generally not needed prior to IV

catheterization and induction in calm and tractable animals

May need tranquilizers for aggressive, excited, or stressed animals

Anticholinergic drugs cause saliva to become thick and ropy

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IV Induction

In a special padded area, in a transporter, on a tilt table

Goal Get to unconsciousness rapidly with minimal injury Get immediate control of the airway

Administration Double drip: ketamine and guaifenesin IV to effect Larger ruminants: IV agent bolus Smaller or compromised ruminants: IV agent to

effect

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IV Induction (Cont’d)

Position Sternal recumbency for intubation Watch for regurgitation to prevent aspiration

Check vital signs and intubate

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Equipment for Endotracheal Intubation

Appropriately sized endotracheal tubes (22-mm, 26-mm, or 30-mm tube)

Stylette (small ruminants and calves only) Mouth gag to hold the jaws apart

(adult cattle only) Laryngoscope (small ruminants and calves) Gauze sponge to grasp the tongue (optional) A syringe to inflate the cuff

10 mL for small ruminants and calves 60 mL for adult cattle

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Intubation of Small Ruminants and Calves

Small oral opening and thick caudal tongue make visualization of larynx challenging

Use of a stylette protruding beyond the end of the tube results in better visualization of the larynx

Head extended, tongue gently pulled forward, laryngoscope is placed to visualize the larynx

Pass stylette into airway Pass endotracheal tube over stylette and into the

larynx Inflate the cuff

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Intubation of a Calf

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Intubation of Adult Cattle

Intubation is done blindly Mouth gag is placed and head is extended by the

assistant Anesthetist protects endotracheal tube cuff with

nondominant hand Using nondominant hand, the anesthetist palpates

the larynx with the fingers and directs the endotracheal tube into the larynx, while advancing the tube with the dominant hand

Inflate the cuff and remove the mouth gag

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Maintenance of Anesthesia with Inhalant Agent

Small ruminants and calves Similar to small animals

Adult cattle Similar to horses

Ruminants tend to hypoventilate Place on ventilator if necessary

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Intravenous Maintenance of Anesthesia

Reserved for short (<20 minute) procedures in healthy patients

Can also be used to extend anesthesia in intubated patient

Double drip commonly used

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Patient Positioning, Comfort, and Safety

Use same principles as for small animals Additional concerns

Position ruminants with mouth lower than pharynx Provide padding to prevent neuropathy and

myopathy as in horses

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Ruminant Anesthetic Recovery

Ruminants tend to have a smooth recovery Patient transferred to padded recovery stall Place in sternal recumbency Make sure mouth is lower than pharynx Monitor for signs of excessive bloating Keep cuff inflated or partially inflated to prevent

aspiration Extubate when strong swallowing movements or

coughing appear

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Ruminant Anesthetic Recovery (Cont’d)

Ruminants tend to have smooth recovery (Cont’d) Remove more air from the cuff if extubation is

difficult Leave unattended after patient is lying in sternal

recumbency without support Don’t need to withhold food or water

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Positioning a Ruminant for Recovery

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Swine Anesthesia

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Physical Examination of Swine

General observation Assess respiratory rate and character Observe obvious problems

Swine are difficult to restrain for a more involved physical examination

Rely on patient history to determine health status

Assessing cardiovascular status and drawing blood samples are difficult to impossible

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Sedation of Swine

Sedatives administered IM No readily available peripheral veins Thick layer of subcutaneous fat

• Must use at least 1.5-inch needle Inject muscles of neck caudal to ear and 3-5 cm

lateral to dorsal midline

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Sedation of Swine (Cont’d)

Swine are resistant to sedative drugs Use a combination of tranquilizer or sedative, an

opioid, and a dissociative May produce sedation enough for short surgical or

nonsurgical procedures TKX: Telazol®, ketamine, and xylazine

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Pig Sedated with TKX

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IM Injection in Swine

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Anesthetic Induction

TKX often induces anesthesia Eyes are not suitable for information

regarding depth of anesthesia Relaxation of mouth muscles (so mouth can

be opened without resistance) is best indicator

If patient isn’t deep enough more anesthetic must be administered IV catheter in aural vein and administer IV

induction drug in small increments Administer inhalant anesthetic via a face mask

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Aural Vein Catheter Placement

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Use of a Face Mask in a Pig

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Swine Intubation

Challenging because of poor visualization Small mouth opening Narrow dental arcade Anatomy of larynx: ventral laryngeal diverticulum Proximal trachea Laryngotracheal junction at angle Laryngospasm

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Swine Intubation (Cont’d)

Methods Patient in sternal or dorsal recumbency Using a straight stylette and laryngoscope Using a curved stylette

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Swine Intubation (Cont’d)

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Maintenance of and Monitoring Swine Anesthesia

Use small animal anesthetic machine and circle system

Can use large animal machine on very large pigs Monitoring

Palpate pulse in the ear or on inside of the carpus Brachial artery in smaller pigs Doppler signal from tail artery Pulse oximeter transmission probes on tongue or snout and

ears of pink pigs Respiratory monitoring with breathing bag and capnometry

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Doppler Probe and Blood Pressure Cuff

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Pulse Oximetry Probe Placement

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Porcine Stress Syndrome

Malignant hyperthermia Can be associated with inhalant anesthesia Mutation in one gene that controls calcium

metabolism in muscle Symptoms

Muscle rigidity Rapid rise in body temperature Hypercapnia and hyperkalemia Death

Treatment Terminate anesthesia, deliver oxygen, dantrolene

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Anesthetic Recovery

General principles for extubation and recovery are the same as for small animals

Leave IV catheter in place if pig is to be hospitalized