equine anesthesia

Veterinary Anesthesia & Surgical Assisting
Jean H. Eye, DVM

Focuses on the specific tasks involved in equine anesthesia, addressing preanesthetic, perianesthetic, and postanesthetic responsibilities.

History & Physical Examination (Hx & PE)
- Obtain complete history of the horse (including any existing medical conditions).
- Conduct physical exams to assess the horse's health status.
Medication Preparation
- Draw up necessary medications prior to the procedure.
Equipment Preparation
- Ensure all anesthesia equipment is ready for use.
Patient Preparation
- Prepare the horse for the anesthesia process.
Keeping Horse Calm
- Maintain a calm environment to reduce stress for the horse.

Rapid Induction
- Successfully and swiftly induce anesthesia.
Protection of Horse and Staff
- Ensure the safety of both the horse and the veterinary staff during the anesthesia.
Monitoring and Support During Anesthesia
- Continuously monitor the horse's vital signs and support its physiological functions throughout the procedure.

Provide Smooth Recovery
- Ensure the horse recovers smoothly from anesthesia.
Protection of Horse and Staff
- Continue to safeguard both the animal and the attending staff following the procedure.

Overview
- Preferred method of anesthesia when circumstances allow.
Factors Influencing Use
- Dependence on the procedure type and horse's temperament.
Recommended Agents
- Administer Alpha 2 Agonist in combination with opioids; may also utilize local anesthetics for additional sedation.

Definition
- Involves general anesthesia for procedures lasting less than 1 hour.
Preparation Steps
- Induction via IV bolus.
- Maintain anesthesia with repeated boluses or constant rate infusion (CRI).
Commonly Used Drugs
- Ketamine in conjunction with Alpha 2 Agonist.
- Guaifenesin as an adjunct muscle relaxant.

Purpose
- General anesthesia suitable for procedures longer than 1 hour, such as abdominal surgeries or those requiring significant support during the process.
Induction Protocol
- Begin with IV induction, followed by the use of inhalant anesthetics to maintain anesthesia.
- Drugs used include Isoflurane or Sevoflurane.

Anticholinergics
- Generally not used as pre-med due to potential side effects like ileus leading to colic.
- Atropine may be administered for cardiac arrhythmias.
Acepromazine
- Commonly employed as a premedicant, requiring 10 minutes for IV and 20-30 minutes for IM effectiveness.
Opioids
- May induce excitement, particularly with morphine; typically used in combination with tranquilizers or sedatives.
Diazepam
- Can be administered with Ketamine.
Guaifenesin
- Acts as a muscle relaxant but can provoke excitement if administered alone; given IV just before induction or as part of CRI.
Alpha 2 Agonists
- Includes Xylazine and Detomidine; used for both standing restraint and as part of general anesthesia protocols.
Ketamine
- Most common agent for inducing anesthesia and can be utilized in CRI applications.

Restraint Setup
- Horses are commonly secured in stocks before the procedure.
Preparation Steps
- Ensure readiness of all materials before administering premedications.
- Utilize an IV catheter when possible for convenience.
Catheter Specifications
- A 4-6 inch, 14-18 g catheter is typically placed in the jugular vein.
Environmental Considerations
- Minimize noise and activities that may disturb or excite the horse.
Signs of Sedation
- Head drooping towards knees, lower lip relaxation, a wide-based stance, reluctance to move, and decreased environmental interest.
- Moving the horse into position may briefly excite it; prolonged drooping can lead to nasal congestion, hence using cross ties keeps the horse's neck positioned neutrally.

Procedure Location Selection
- Considerations must be made for environment—grass preferred over rocks, anthills, or cactus.
- Ensure available shade for comfort.
Material Assembly
- Gather all materials prior to starting the process, including IV catheter, pre-medication supplies, and presurgical antibiotics.
Positioning for Anesthesia
- Proper position is critical to avoiding complications such as neuropathy.
- Remove the halter and use soft materials to prevent eye and facial nerve injuries.
- Maintain the thoracic limb position to alleviate pressure on the brachial plexus and radial nerve.
- Keep hind limbs separated to ensure safety.
Monitoring During Anesthesia
- Assess pulse (facial artery), respiratory rate, eye positioning, palpebral reflex (should be depressed), and monitor for nystagmus during recovery.
Recovery Protocol
- To aid recovery, kneel on the horse's neck to keep it grounded until it can stand.
- Additional sedation or tranquilizers may be necessary for a smooth recovery.

Transfer Between Facilities
- Horses may need to be moved from induction stall to surgery room while still anesthetized.
- Ensure all medications and equipment are accessible in the procedure room prior to starting.
Preparation Steps
- Administer pre-medications and keep the horse in a quiet environment.
- Transfer horse to a padded induction room where IV induction with a rapid bolus is performed.
Intubation Process
- Use a 22-30 mm cuffed endotracheal tube; extend the horse's neck, place a mouth gag, and perform blind intubation with cuff inflation.
- Move the horse to the surgery room after securing intubation.
Monitoring and Support Specifics
- Major complications include hypoventilation, hypoxemia, and hypotension.
Equipment for Monitoring
- Utilize a mechanical ventilator in conjunction with the anesthetic machine.
- Employ an arterial catheter (facial artery or dorsal metatarsal artery) for blood samples to assess blood gases within 15 minutes.
- Direct measurement of blood pressure should be maintained above 70 ext{ mm Hg}.
Recovery Protocol
- Place in padded stalls with ropes attached to the halter and tail to assist standing.
- Additional sedation and nasoendotracheal tubes may be required for recovery assistance.

Video links provided by the University of Minnesota on various aspects of equine anesthesia, including induction, surgical preparation, and recovery phases.