Anesthesia Guidelines: Ferrets

Research Animal Resources (RAR) veterinary staff designed these guidelines to be general recommendations, not an inclusive list of all possible drug combinations that can be used in ferrets. Consequently, guidelines do not reference specific research-associated concerns.

These guidelines are for healthy adult ferrets, and special considerations apply for sick or young ferrets. If you have questions about using anesthetics for these scenarios or for your particular situation, please work with your area veterinarian to develop the most effective anesthetic plan.


Species-specific considerations

Fasting

Due to the relatively fast gastric transit time of ferrets, a fasting time of 3-4 hours for healthy adult ferrets is recommended, with shorter periods for young or sick animals. Fasting for longer periods of time will cause low blood glucose levels, which will prolong recovery and disturb the acid-base balance of the ferret.

Hypoglycemia

Long, invasive procedures may warrant monitoring and maintaining the glycemic status of the ferret perioperatively and intraoperatively. Ferrets with a hypoglycemic status can be supplemented with dextrose orally or incorporated into the material used for fluid support before or during the procedure.

Cardiac arrhythmias

Ferrets are prone to experiencing cardiac arrhythmias under the influence of isoflurane or ketamine/xylazine. Head and neck manipulation, gastrointestinal manipulation, pressure in the chest, or an unknown trigger can stimulate the vagal reflex. Either of these occurrences can cause a decrease in heart rate or complete cardiac arrest. Premedication of ferrets with atropine 0.4-1 mg/kg SC is recommended, as well as appropriate monitoring equipment and a plan of action should this arise (additional doses of atropine 0.5 mg/kg SC or IV as needed to control bradycardia is recommended).

Gastrointestinal ulceration (even if previously undetected) can cause histamine release that can affect blood pressure and heart rate. Consult your area veterinarian for recommendations for antihistamine premedication if there is a concern.


General considerations

Acclimation period

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 the animal to acclimate to the facility and reduces the chance of stress-induced disease, including anesthetic death.

Heat support

Ferrets are susceptible to hypothermia, which slows recovery and further stresses the animal. This is due to their large surface area relative to their body mass and the fact that most anesthetic agents lower body temperature. To prevent hypothermia, provide supplemental heat during anesthetic procedures and recovery. Use a device that provides circulating warm water or air, not electric heating pads in order to reduce the risk of thermal injury. Regardless of heat source, do not place animals directly on the heat.

Catheterization

Following sedation, place an indwelling catheter to administer anesthetic drugs, emergency drugs, and intravenous fluid support. The jugular, cephalic, or lateral saphenous veins are the preferred sites. Ferret skin is tough and the subcutaneous fat layer can be thick, which can make catheterization difficult. Using the beveled edge of a 20 gauge needle or small blade to make a small incision in the skin can ease insertion of the catheter (a short 22-26 gauge catheter size is recommended). Applying a topical anesthetic to the skin 30 minutes before venipuncture reduces discomfort.

Fluid support

Provide fluid support to ferrets that will be undergoing procedures longer than 30 minutes or are dehydrated. 5-10ml/kg preoperatively and intraoperatively as needed is generally appropriate. Lactated Ringer’s or 0.9% NaCl are commonly used, often with 2.5-5% dextrose incorporated for glycemic support.

Monitoring

Regardless of the anesthetic administered, monitor ferrets to avoid excessive depression of cardiac and respiratory functions, or insufficient anesthesia. 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 ferret include:

Required

Temperature
Anesthetic depth: Toe pinch, palpebral reflex
Heart rate
Respiratory rate and pattern
Expired CO2 (if intubated)
Oxygen saturation (pulse oximetry)

Recommended, especially for involved or prolonged procedures

EKG - To monitor for arrhythmias
Blood pressure

Normal Values

  • Temperature (F): 100-102.5 (can be as high as 104)
  • Heart rate (beats per minute): 180-250 (can be as high at 400)
  • Respiratory rate (breaths per minute): 30-40
  • Blood pressure (mmHg): Systolic: 140-164, Mean: 161 (male)/133 (female), Diastolic: 110-125
  • Mucus membranes: pink, moist, capillary refill time <2 seconds, not gray, white, blue

Anesthetized Values

  • Temperature (F): >98
  • Heart rate (bpm): 185–225
  • Respiratory rate (breaths per minute): Approximate to the pre-anaesthetic value
  • Blood pressure (mmHg): Systolic: 90–155. Mean: 69-109, and should be above 60, Diastolic: 55 to 90 mmHg.
  • Mucus membranes: pink, moist, capillary refill time <2 seconds, not gray, white, blue
  • Expired CO2 (ETCO2): 35-45 mmHg
  • Oxygen saturation (SpO2): >95%

Recovery

During the immediate post-anesthetic period, remove food and water from the cage. Do not replace food and water until the animal is fully awake and ambulatory. Ferrets should eat as soon as possible after an operation to help prevent hypoglycemia.


Anesthetic drugs and procedures

Ferret anesthesia is generally broken up 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 placement of indwelling catheters (for IV drug and fluid administration) or allow for intubation (for inhalation anesthesia). For some procedures, sedation and maintenance are covered by the initial drug administration.

The injectable anesthetics of choice is ketamine combined with xylazine. If additional anesthesia is needed, re-dose with 1/3 the original calculated dose of ketamine. Do not redose xylazine due to its hypotensive effects.


Ketamine + Xylazine (Rompun®) (Recommended)

Dose: Ketamine: 20-30 mg/kg + Xylazine: 2-5 mg/kg, with premedication with 0.4 mg/kg of atropine
Route: IM, IP
Comments: Analgesia, muscle relaxation, and smooth recovery. Cardiac arrhythmias, hypotension and hypothermia possible. Thermal support is crucial, monitoring for cardiac arrhythmias is recommended. To prolong anesthesia, supplement with 1/3 dose of ketamine only. Xylazine can be reversed with 0.2-0.5 mg/kg yohimbine IP or IM, or 0.1 –1 mg/kg atipamezole, IP, IV or SC, or IM.


Ketamine + Dexmedetomidine

Dose: Ketamine: 5 mg/kg + Dexmedetomidine: 0.04 mg/kg
Route: IM, IP
Comments: Analgesia, muscle relaxation, and smooth recovery. Cardiac arrhythmias, hypotension and hypothermia possible. Thermal support is crucial, monitoring for cardiac arrhythmias is recommended. To prolong anesthesia, supplement with 1/3 dose of ketamine only. Dexmedetomidine can be reversed with the same volume of atipamezole that was given for dexmedetomidine, given SQ, IV, or IP.


Ketamine + Xylazine + Butorphanol

Dose: Ketamine: 15 mg/kg + Xylazine: 2 mg/kg + Butorphanol: 0.2 mg/kg
Route: IM
Comments: Analgesia, muscle relaxation, and smooth recovery. Cardiac arrhythmias, hypotension and hypothermia possible. Thermal support is crucial, monitoring for cardiac arrhythmias is recommended. To prolong anesthesia, supplement with 1/3 dose of ketamine only. Xylazine can be reversed with 0.2-0.5 mg/kg yohimbine IP or IM, or 0.1 –1 mg/kg atipamezole, IP, IV or SC, or IM.


Ketamine + Acepromazine*

Dose: Ketamine: 30 mg/kg + Acepromazine: 0.3 mg/kg
Route: IM
Comments: Mild anesthesia and analgesia for minor procedures such as a blood draw or IV catheterization. Hypotension and hypothermia may occur.

*A dose of acepromazine alone at 0.1 mg/kg IM can produce adequate sedation for minor procedures such as ear cleaning, toenail clipping, blood collection or imaging, but not intubation. At higher doses, hypothermia and a prolonged recovery can occur.


Ketamine + Midazolam

Dose: Ketamine: 5-15 mg/kg + Midazolam: 0.25-0.4 mg/kg
Route: IM
Comments: Varied sedative effects reported. Mild anesthesia and analgesia for minor procedures such as a blood draw or IV catheterization to heavy sedation. Reversal of midazolam with flumazenil at 0.01-0.2 mg/kg IM.


Other considerations when using the following agents:

Diazepam

Ferrets exhibit signs of excitement, poor sedation and muscle relaxation, resistance to procedures, and responsiveness to noise when given this agent. The large intramuscular injection volume of diazepam (5 mg/ml) coupled with the small muscle mass of ferrets can result in treated ferrets exhibiting temporary lameness during the recovery period. If used, it is best given via the intravenous route. Please consult your area veterinarian for recommendations for dosing, if requested.

 

Induction

Induction

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


Ketamine + Xylazine (Rompun®) (Recommended)

Dose: Ketamine: 20-30 mg/kg + Xylazine: 3-5 mg/kg, with premedication with 0.4 mg/kg of atropine
Route: IM
Comments: Thermal support is crucial. To prolong anesthesia, supplement with 1/3 dose of ketamine only. Xylazine can be reversed with 0.2-0.5 mg/kg yohimbine IP or IM, or 0.1 –1 mg/kg atipamezole, IP, IV or SC, or IM.


Telazol® (Tiletamine + Zolazepam) + Xylazine

Telazol (3 mg/kg) + xylazine (3 mg/kg)
Comments: Thermal support and oxygen supplementation is crucial. To prolong anesthesia, supplement with 1/3 dose of ketamine only. Xylazine can be reversed with 0.2-0.5 mg/kg yohimbine IP or IM, or 0.1 –1 mg/kg atipamezole, IP, IV or SC, or IM.


Propofol

Dose: 1-3 mg/kg
Route: IV
Comments: Propofol causes respiratory depression, even apnea, as well as depressed myocardial contractility. Any animal receiving propofol should be intubated following administration.


Isoflurane

Dose: 3-5%
Route: Inhalation
Comments: Pre-sedation is recommended if using isoflurane for induction to prevent distress to the ferret, with Acepromazine at 0.1 mg/kg SC given prior to induction. Induction via induction chamber or nose cone on a non-sedated animal can lead to distress and struggling, and is not recommended. Isoflurane decreases hematocrit, hemoglobin concentration, and red blood cell counts and plasma protein in ferrets, as well as causes profound salivation, making visualization during intubation more challenging.

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 may be delivered by a facemask or endotracheal tube. The laryngeal anatomy of the ferret can make intubation difficult.

  • If using an endotracheal tube, a size 2.0-2.5 mm uncuffed tube is generally appropriate for ferrets under 1kg. For ferrets over 1 kg, a cuffed 3.0 mm or uncuffed 3.5 mm endotracheal tube may be appropriate.
  • The endotracheal tube should extend approximately from outside of the mouth to the thoracic inlet. This can be a guide for how far the tube should be inserted upon intubation.
  • A small amount of topical anesthetic spray (such as lidocaine or cetacaine) applied at the laryngeal opening may facilitate the endotracheal intubation but is not necessary
  • 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.

Gas Anesthesia Machines

Facemasks and intubation require gas anesthesia machines with an oxygen source and a precision vaporizer. Due to the small respiratory capacity, use a non-rebreathing system.

Ventilation Respiratory Rates and Volumes

The tidal volume of ferrets is estimated as 10–15 ml/kg. A respiratory rate of 8–30 breaths/min of generally appropriate (may be set as high as 70 to achieve acceptable EtCO2 and SpO2), and a peak inspiratory pressure not exceeding 10–15 cm of water is necessary.

Gas Scavenging System

When using inhalant anesthesia, use a fume hood or 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, use an ophthalmic ointment (e.g., Paralube® or Lacrilube®) to prevent corneal drying and trauma.


Isoflurane (Recommended)

Dose: 1-4% maintenance
Comments: Using isoflurane as the sole agent of anesthesia induction may be associated with excitement and distress. Isoflurane decreases hematocrit, hemoglobin concentration, and red blood cell counts and plasma protein in ferrets, as well as causes profound salivation, making visualization during intubation more challenging. It may also cause cardiac arrhythmias in otherwise healthy young ferrets.

Please contact your area veterinarian for dose and rate recommendations if you wish to use a continuous rate infusion for maintenance of anesthesia.


References

  • Jeff Ko, Robert P. Marini, Chapter 16 - Anesthesia and Analgesia in Ferrets, Editor(s): Richard E. Fish, Marilyn J. Brown, Peggy J. Danneman, Alicia Z. Karas, In American College of Laboratory Animal Medicine, Anesthesia and Analgesia in Laboratory Animals (Second Edition), Academic Press, 2008, Pages 443-456, ISBN 9780123738981, https://doi.org/10.1016/B978-012373898-1.50020-6. (http://www.sciencedirect.com/science/article/pii/B9780123738981500206)
  • Johnson-Delaney, Cathy, Ferret Cardiopulmonary Resuscitation in Seminars in Avian and Exotic Pet Medicine, Vol 14, No 2 (April), 2005: pp 135–142. DOI: 10.1053/j.saep.2005.04.008
  • Johnson-Delaney, Cathy. Analgesia and Anaesthesia in Ferret Medicine and Surgery. 2017. CRC Press.
  • Matchett, Andrew C., Marr, Rena, Berard, Felipe M., Cawthon, Andrew G., Swing, Sonya P. The Laboratory Ferret. 2012. CRC Press.
  • van Zeeland, Y.R.A. Wilde, A.,Bosman, I.H.,Uilenreef, J.J.,Egner, B.,Schoemaker, N.J. Non-invasive blood pressure measurement in ferrets (Mustela putorius furo) using high definition oscillometry,2017/10// The Veterinary Journal.228.53-62 https://linkinghub.elsevier.com/retrieve/pii/S1090023317302010