Equine Surgery and Anesthesia Flashcards

Flashcards on Equine Surgery and Anesthesia for veterinary technicians.

Standing Surgery

•  Vast array of procedures now available

•  Range from simple laceration repair to laser surgery and laparoscopy

•  Divided into two major categories

• Standing surgery procedures

• General anesthesia (recumbent) procedures

Benefits of Standing Surgery

• Avoids risks associated with general anesthesia, especially during recovery.

•  Recovery from general anesthesia is the single largest risk for large animal surgery patients (even elective procedures on healthy patients)

 Criteria/Indications for Standing Surgery

• Safety for the patient, surgeon/personnel, and the equipment

• Beneficial for sick, debilitated, or geriatric patients

• Decreases risk of compartment syndrome of large or heavy muscled breeds

• Less risk in trauma/extremely stressed patients

• If patient has history of problems with general anesthesia/recovery

• Less cost

Disadvantages of Standing Surgery

• Surgeon discomfort

• decreased visualization

• difficult to maintain sterile field

• potential danger due to patient movement — Dangerous to patient, surgeon, and the equipment

Preparation for Standing Surgery

•  Feed is normally withheld for 6 hours before standing sedation

•  Feed is normally withheld for 6-24 hours before general anesthesia depending on the procedure

•  Water is usually not withheld

•   Clean, dry, dust-free environment

•  Elevate sterile instruments off the ground

•  Patient under proper restraint

•  Commonly used chemical restraining agents:  acepromazine; xylazine; detomidine; butorphanol

•  Don’t forget analgesia

Local Anesthesia Nerve Blocks

• If a nerve can be reached with a needle, then local anesthetic can be applied to that nerve

• Anesthetic and sensation “maps” for major nerves are available

Local Anesthesia Field blocks and line blocks

• Usually to desensitize skin and subcutaneous tissue around surgical area

• Line blocks useful for lacerations

• Field blocks useful for abdominal procedures performed through flank

Caudal Epidural

• Used routinely for analgesia of the tail, perineum, anus, rectum, vulva, vagina

• Decreases straining during reproductive procedures or dystocia

• Analgesic is placed in epidural space between 1^st and 2^nd coccygeal vertebrae

 Three classes of drugs useful for epidural

• Local anesthetics – lidocaine, mepivacaine, bupivacaine

  • Block sensory and motor fibers

  • May cause ataxia, collapse of hindlimbs (rare)

• Alpha-2 agonists – xylazine, detomidine

  • Block sensory fibers only, minimal effect on hindlimb function

• Opioids – morphine, butorphanol

  • Block sensory fibers, minimal effect on hindlimb function

Post-Op Care of Standing Surgery

NPO until horse swallows normally, followed by small amounts of water and hay, and monitoring urine/fecal output.

General Anesthesia Considerations

Importance of preoperative patient exam, lab evaluation, and correction of imbalances.

Ventilation Problems During General Anesthesia

Common due to abdominal organ weight pressing on the diaphragm; improved by fasting patients.

Why are anticholinergics (atropine) avoided in horses?

Anticholinergics depress gastrointestinal motility which may lead to ileus

General Anesthesia Preparation Steps

Surgical clip/prep, IV catheter placement, equipment check, proper positioning, oral cavity flush, patient cleaning.

Prevention of Compartment Syndrome During General Anesthesia

Minimize anesthesia time, maintain adequate blood pressure and lightest plane possible, use padding.

◦Lateral recumbency – pull “down” limb cranially, pad between limbs

◦Dorsal recumbency – let forelimbs fold at carpus, let hindlimbs “frogleg”

Compartment Syndrome

• Arteries bring blood but veins/lymphatics collapse. Pressure rises inside muscle compartments and causes damage.

• To resist the pressure of the muscles, blood pressure must be maintained during recumbency

Induction Methods for General Anesthesia

Injectable drugs alone, injectable drugs followed by gas anesthesia, or gas anesthesia alone (small foals only).

 Endotracheal Intubation:

• Orotracheal (preferred)

• Nasotracheal (primarily foals and small individuals < 100 kg)

• Direct tracheal (uncommon)

Large Animal Anesthesia Machine Preload

Rubber components absorb anesthetic gas, so need to preload circuit before attaching patient—takes 10-15 mins to preload

Monitoring General Anesthesia

• Patient monitoring is essential—TPR, heart rhythm, CRT/mm color, EKG

• Anesthetic depth:  eye position (rolled rostral/down); reflexes (slow palpebral)

  • Too light:  nystagmus; HR, RR, BP increase

• Maintain anesthetic records, regardless of length of procedure

• Primary concerns

  • Hypothermia

  • Hypoventilation

  • Hypotension

  • Bradycardia

Primary Anesthesia Concerns

Hypothermia, hypoventilation, hypotension, bradycardia.

Recovery from General Anesthesia Risks

Due to the horse's natural inclination to stand quickly, even before the anesthetic drugs have fully metabolized and compartment syndrome.

Foals considerations during recovery

Foals should never be left alone, best if two people monitor

ET tube removal

ET tube removed once swallowing

Recovery from General Anesthesia: Post-Standing Considerations

• Returned to stall by two people

• Walk close to horse

• Avoid sharp turns, small aisles and small doorways

• Monitor fecal output/GI motility closely

• NPO immediately after recovery, make sure not eating bedding

• Start with water sips, then increase

• Hay usually 2 hours after recovery, small amounts to monitor swallowing

• Full rations the next day