Anesthesia: Swine

Find guidelines for pig anesthesia, including recommended anesthetic drugs and procedures.

Research Animal Resources (RAR) veterinary staff designed these guidelines to be general recommendations, not an inclusive list of all possible drug combinations for pigs.  Consequently, they do not include reference to specific research-associated concerns.

If you have questions about using anesthetics for your particular situation, please work with your area veterinarian to develop the most effective anesthetic plan.


Species-specific considerations

Malignant hyperthermia (MH)

Some breeds – primarily Landrace, Pietrain, and Poland China– are susceptible to malignant hyperthermia (MH) with certain anesthetic protocols. MH is a hypermetabolic state of the skeletal muscle induced by volatile inhalational anesthetics, succinylcholine, and stress.  

  • Early signs of MH include decreases in pH and pO2, and increases in lactate, ETCO2, PCO2, potassium, and body temperature.
  • If MH is suspected, discontinue anesthesia, administer oxygen, and contact the area veterinarian.
  • The body can be cooled with cold water packs, or ice packs wrapped in towels.

Postoperative condition

There is a postoperative condition in swine that resembles MH but is considered a distinct condition. It is characterized by critically elevated body temperature and hyperlactatemia greater than 2.5 mmol/L during the recovery period.

Anesthetic depth indication

Jaw tone is the most reliable indicator of anesthetic depth in swine and should be assessed throughout the procedure. Rigidity of the mandibular muscles indicate the anesthetic depth is light.


General considerations

Acclimation

Do not use newly arrived animals for experimental procedures until 72 hours after entry into the facility. A one-week acclimation period is recommended. This stabilization period is not required for animals used acutely (anesthetized and euthanized at the end of the procedure), although it is recommended. This provision allows animal to acclimate to the facility and reduce the chance of stress-induced disease, including anesthetic death.

Fasting

Pigs can vomit and aspirate stomach contents while under general anesthesia. To help prevent this, fast animals overnight prior to general anesthesia. Never restrict water.

Heat

Because most anesthetic drugs cause hypotension and hyperthermia, provide supplemental heat to animals under anesthesia. Regardless of heat source, never place animals directly on the heat.

Catheterization

Following sedation, place an indwelling catheter to administer anesthetic drugs, emergency drugs, and intravenous fluid support. The auricular vein is most commonly used.  Lateral saphenous and cephalic veins can also be used for catheterization or IV injections.

Fluid support

Provide supplemental fluid support for animals that will be under anesthesia for longer than 30 minutes. Appropriate fluid rates range from 5-10 mls/kg/hour, and may vary based on the anesthetic combination.

Monitoring

Standard mammalian monitoring techniques apply to swine. The goal of monitoring is to maintain cardiovascular homeostasis and core body temperature.

Understanding the basic physiologic effects of the anesthetics used is paramount to correctly interpreting monitoring parameters. View descriptions of anesthetic agents.

Parameters to monitor in an anesthetized swine include anesthetic depth, heart rate, respiratory rate, oxygen saturation, expired CO2 (EtCO2), temperature, blood pressure, and mucous membrane color. Monitoring body temperature is critical  especially in breeds prone to MH.

Normal ranges (without anesthesia)

  • Temperature = 100-102.5°F
  • Heart rate (beats/minute) = 70-180
  • Respiratory rate (breaths/minute) = 20-40 resting
  • Blood pressure = >60 mm Hg (mean) and >90 mm Hg (systolic) 
  • Oxygen saturation = >95%
  • EtCO2 = 35-45
  • Mucous membranes = pink, not pale, white, gray, or blue

Normal range (with anesthesia)

  • Temperature = >98°F
  • Heart rate (beats/minute) = 60-140
  • Respiratory rate (breaths/minute) = 6-20
  • Blood pressure = >60 mm Hg (mean) and >90 mm Hg (systolic)
  • Oxygen saturation = >95%
  • EtCO2 = 35-55 (note: Sudden increases can signify the onset of MH)
  • Mucous membranes = pink, not pale, white, gray, or blue

For more involved procedures, EKG, invasive pressure monitoring, and blood gas analysis may be indicated.  


Anesthetic drugs and procedures

Swine anesthesia is generally broken into premedication (sedation), anesthetic induction, and anesthetic maintenance.

As with other species, anesthesia (maintenance) can be accomplished via inhalation or parenteral methods.

Sedation

Sedation

Administering sedative drugs decreases excitement and causes relaxation to allow for the placement of indwelling catheters (for IV drug and fluid administration) or allow for intubation (for inhalation anesthesia).

Induction (see below) is often required in addition to sedation to provide a sufficient level of sedation/anesthesia for intubation.

An excellent induction combination is Telazol (tiletamine/zolazepam) with Xylazine. This provides rapid sedation for intubation and catheter placement (refer to chart below for doses).

The anticholinergics glycopyrrolate (0.004-0.01 mg/kg IM) or atropine (0.04 mg/kg IM) are used as a premedication to dry oral and respiratory secretions and for its vagolytic effects (i.e., ability to block vagal nerve stimulation and consequent bradycardia) during endotracheal intubation.


Telazol® + Xylazine – recommended

Dose: Telazol: 2-8 mg/kg Xylazine: 1-3 mg/kg
Route: Intramuscular (IM)


Telazol + Ketamine + Xylazine – recommended

Dose: 0.02-0.04 mls/kg of mixture – see comments
Route: IM
Comments: Preparation: Reconstitute an unused vial of Telazol with 2.5 mL ketamine (100 mg/mL) and 2.5 mL xylazine (100 mg/mL). This results in 100 mg/mL dissociative (tiletamine and ketamine), and 50 mg/mL each of xylazine and zolazepam. The benzodiazepine component is reduced to 25% of the total drug dose compared to the TX mixture.


Tiletamine + Zolazepam (Telazol®)

Dose: 2-8.8 mg/kg
Route: IM
Comments: Difficult intubation due to minimal muscle relaxation.


Ketamine + Xylazine

Dose: Ketamine: 20 mg/kg + Xylazine: 2 mg/kg
Route: IM
Comments: Short-acting in swine (~5-10 minutes).

Induction

Induction

Induction refers to an anesthetic administered to place an animal in an unconscious state and allow for tracheal intubation.


Isoflurane

Dose: 2-4%
Route: Inhalation/facemask


Propofol

Dose: 0.83-1.66 mg/kg
Route: IV 
Comments: Can cause respiratory depression and apnea– use “to effect”. Propofol can cause hypotension when given as a bolus.


Pentobarbital

Dose: 20-40 mg/kg
Route: IV
Comments: Cardiodepressant, prolonged recovery. Not recommended for recovery surgery.

Maintenance

Maintenance

Maintenance refers to drugs administered to keep animals unconscious and allow for surgical (or other) procedures to be performed.

Endotracheal intubation: Inhalation anesthesia can be delivered by a facemask, but is generally delivered via endotracheal intubation. 

  • Swine are one of the more difficult species to intubate, and improper technique can result in significant trauma. 
  • Trauma can result in laryngeal rupture, laryngeal edema, or passage of the endotracheal tube in the subcutaneous space. To facilitate proper intubation, the animal should be in a deep anesthetic plane prior to passing the endotracheal tube. Swindle (Second Edition, pg. 40-41) provides a detailed description of swine intubation (Swindle, M.M. (2007). “Swine in the Laboratory: Surgery, Anesthesia, Imaging, and Experimental Techniques” Second Edition. CRC Press).
  • The endotracheal tube should extend approximately from outside the mouth to the thoracic inlet. This can be a guide for how far the tube should be inserted upon intubation. 
  • Verify proper placement of the endotracheal tube by ausculting all lung fields for strong breath sounds. If no breath sounds are heard, back the tube out until sounds are heard in all lung fields. 
  • Nitrous oxide may reduce the concentration of isoflurane required. It cannot be used as a sole anesthetic agent and must be delivered in a 1:1 or 2:1 mixture of nitrous oxide to oxygen combined with other inhalant anesthetics. Additionally, nitrous oxide is not absorbed by charcoal canisters and can only be used with vacuum scavenging anesthetic systems.

Gas anesthesia machines: Facemasks and intubation require gas anesthesia machines with an oxygen source and a precision vaporizer. For swine, use a rebreathing system.

Gas scavenging systems: When using inhalant anesthesia, use an anesthetic system equipped with a gas scavenging system to minimize occupational exposure to exiting gases.

Ophthalmic ointments: For anesthetic events lasting more than five minutes and whenever facemasks are used, apply an ophthalmic ointment (e.g., Paralube® or Lacrilube®) to eyes to prevent corneal drying and trauma.

Ventilator pressure: Maintain between 11-20 cm H2O. Swine have very fragile pulmonary tissue, which can be damaged by hyperinflation.


Isoflurane

Dose: 1-2%
Route: Inhalation/endotracheal tube


Propofol 

Dose: 14-20 mg/kg/hour
Route: IV 
Comments: Propofol causes respiratory depression. Any animal receiving propofol should be intubated following administration.


Pentobarbital

Dose: 5-40 mg/kg/hour
Route: IV
Comments: Cardiodepressant, prolonged recovery. Not recommended for recovery surgery.


References for these guidelines are available by request.