Guidelines

Guidelines on Anesthesia and Analgesia in Ruminants

Unit for Laboratory Animal Medicine
Mar 1, 2018 12:00 am

This set of guidelines was prepared by the ULAM veterinary staff to provide general recommendations for anesthesia and analgesia in laboratory ruminants. This is not intended to be an all-inclusive tutorial, and does not factor in specific research-related concerns.

  • Responsibility

    1. Principal Investigator: Responsible to ensure appropriate anesthesia and/or analgesia is provided for all ruminants undergoing painful procedures including ruminant survival surgery unless otherwise indicated in the relevant approved protocol.
  • Glossary Definitions

    Sedation

    Central depression causing stupor where the animal is unaware of its surroundings but still responsive to painful procedures.

    Small Ruminant

    Sheep and goats.

  • Procedures

    1. Specific Concerns in Ruminant Anesthesia

    1. Acclimation Period: Newly arrived ruminants will receive an intake examination by a veterinarian. Newly arrived animals should be acclimated at least 3 days prior to anesthesia or sedation though one week is highly recommended. This allows them to adjust to a different environment and ensure proper nutritional status.
    2. Fasting: Bloat or rumen distention can be minimized by fasting calves and small ruminants for a minimum of 12-24 hours (with no water restriction). The fasting of young animals less than 4 months old is not recommended because of the potential for hypoglycemia and prolonged recovery.
    3. Vascular Access: When venous access is necessary, the jugular vein is the most common location for catheterization or IV injections. Other locations include the cephalic, ear, and saphenous veins. The maintenance fluid rate for small ruminants is 1 mL/lb/hr. Commonly used replacement and maintenance fluids in small ruminants include Lactated Ringer’s Solution (LRS) and normal saline (0.9% NaCl).
    4. Table 1: Catheter Sizes Based on Location 
         Vein       Catheter Size   
         (length)   
         Jugular       16 or 18 g   
         (3.25 - 3.5")   
         Cephalic       18 - 20 g   
         (1 - 2")   
         Auricular       20 - 22 g   
         (0.75 - 1.0")   
         Saphenous       18 - 22 g   
         (1 - 2")   
    5. Intubation: Tracheal intubation with appropriate inflation of the cuff immediately following anesthetic induction is necessary to protect the airway from saliva and rumen contents.
      1. Table 2: Endotracheal Tube Sizes Based on Weight 
           Body Weight (kg)       Endotracheal   
           Tube Size (mm)
           
           <30       4 - 7   
           100 - 150       12 - 14   
           60 - 80       10 - 12   
           30 - 40       8 - 11   
    6. Rumen Tube Placement:
      1. Regurgitation: Regurgitation during anesthesia is a common problem in ruminants. Lowering the head of the animal and periodic suctioning of the mouth may facilitate fluid drainage. Passing a stomach tube into the rumen can also help to decrease the risk of aspiration. The risk of regurgitation decreases significantly when feed is withheld for 12–24 hours prior to anesthesia in small ruminants.
      2. Bloat: In the event that an animal becomes bloated, gas can be evacuated from the rumen by passing a stomach tube. If you are suspicious of bloat, please contact the ULAM veterinary staff for assistance.
    7. Positioning:
      1. Proper padding and optimal positioning of ruminants during surgery is important to prevent limb nerve damage. Ruminants should be placed on a flat surface with sufficient padding (min. 1-2” thickness recommended for calves, sheep and goats).
      2.  Due to salivation and regurgitation, the head should be lowered. Placing a sandbag or rolled-up towel under the neck of a small ruminant to elevate the throat latch allows saliva to escape, avoiding the potential for aspiration. This technique also helps to minimize the flow of passive regurgitation during deep anesthesia.
    8. Special Considerations: Additional PPE is required due to the risk of exposure when working with sheep with Orf lesions or increased risk of Q fever transmission. Refer to Animal Handler Occupational Health & Safety Program and Procedures to Reduce Human Exposure to Orf and Q Fever for further information.

    2. Monitoring & Recovery

    1. Standard mammalian monitoring techniques are applicable to ruminants – the goal of monitoring should be to maintain cardiovascular hemodynamics and core body temperature. Understanding the basic physiologic effects of the anesthetics used is paramount to correct interpretation of monitoring parameters. For uncomplicated, brief surgeries, monitoring vital signs (e.g. BP, HR, RR, pO2), and ECG may be adequate. For more involved procedures, invasive pressure monitoring and blood gas analysis may be indicated.
    2. Table 3: Monitoring Parameters 
         Parameter       Expected Values - Anesthetized   
         Heart Rate   
         (beats per minute)   
         80 - 150 (sheep, goats, calves)   
         70 - 100 (adult cattle)
         Direct Blood Pressure       75 - 100 mm Hg (mean)   
         60 - 80 mm Hg (diastolic)   
         Respiratory Rate   
         (beats per minute)   
         20 - 40 (sheep, goats, calves)   
         20 - 40 (adult cattle)   
         End-tidal CO2       35 - 40 mm Hg   
         Temperature (oF)       >98 (all species)   
    3. Jaw tone most reliably reflects depth of anesthesia and should be assessed throughout the procedure. The eye rotates ventrally as anesthesia deepens and only the sclera is seen; it then rotates centrally during deep anesthesia. Palpebral reflex is lost at light planes of anesthesia in ruminants and is, therefore, of little value as a measure of anesthetic depth in these species.
    4. Adequate ventilation is crucial in ruminants. Organs can push against the diaphragm, therefore not allowing for normal tidal volumes with decreased respiratory efforts due to the anesthesia. Ventilation should be assisted or controlled by squeezing the rebreathing bag with a positive pressure of 20 to 25 cm H2O if an inhalation anesthetic is used. A mechanical ventilator is highly recommended to alleviate this effect and prevent atelectasis. Keeping the ventilator pressure at 20 mm Hg and sometimes even a little higher periodically, not to exceed 40 mm Hg, will help open all of the alveoli. Tidal volume should be set to 10 mL/kg.
    5. During recovery from anesthesia, after rumen tube and endotracheal tube are removed, recover ruminant in a sternal position.

    3. Agents Used for Sedation or Restraint

    1. Table 4: Sedatives Used in Small Ruminants 
         Agent       Sheep Dose (mg/kg)       Comments   
         Phenothiazines       
         Acepromazine       0.02 - 0.05 IV   
         0.05 - 0.2 IM   
         Slow onset of mild sedation, usually without recumbency   
         α-2 Agonists         Drugs of this class may cause pulmonary edema and hypoxemia   
         in sheep, especially when given at high dose or IV.   
         Xylazine       0.016 - 0.1 IV   
         
         
         0.05 - 0.3 IM   
         Standing sedation 30 - 60 min   
         Recumbency for 60 min   
         
         Recumbency for 60 min   
         Can result in severe hypoxemia and pulmonary edema:   
         monitor lung sounds and oxygenation.  Use with extreme caution   
         in animals with cardiovascular disease or in late pregnancy.
         Yohimbine for xylazine reversal (0.1 - 1.0 mg/kg IV).   
         Atipamezole may also be used for reversal (0.1 - 0.2 mg/kg IV or IM).   
         Xylazine +   
         Butorphanol   
         0.1 - 0.2 (X) IV + 0.01 - 0.02 (B) IV   
         0.02 (X) IM + 0.05 - 0.07 (B) IM   
         Butorphanol may cause slight CNS stimulation, especially when   
         used in animals that are not in pain.  Twitching of the facial   
         muscles, lips, and head may occur.   
         Dexmedetomidine       0.015 IM       Atipamezole used for reversal (0.1 - 0.2 mg/kg IV or IM).   
         Benzodiazepines         Very low doses of benzodiazepines can cause excitement   
         when given IV.   
         Diazepam       0.5 - 1.0 IV slowly       Provide muscle relaxation, hypnosis, decreased anxiety, and mild   
         sedation. Reverse with flumazenil (0.02 mg/kg IV or IM).   
         Midazolam       0.3 - 0.5 SC, IM, IV       Provide muscle relaxation, hypnosis, decreased anxiety, and mild   
         sedation. Reverse with flumazenil (0.02 mg/kg IV or IM).   
    2. For calves, a combination of injection and inhalation with xylazine (0.2 mg/kg), ketamine (2 mg/kg), and isoflurane (1.5-3.0 vol%) was associated with fewer pain-associated reactions compared to injection or inhalation alone (Hefti 2012). The triple drip described in Table 3 can also be used in calves.

    4. Preferred General Anesthetics

    1. Inhalation Agents: Inhalation anesthesia with a rebreathing system is the method of choice for maintaining anesthesia for long periods of time. Advantages of inhalant anesthesia are rapid control of anesthetic depth and rapid recovery. Use caution when recovering animals from inhalant agents due to the potential for dysphoria and risk of injury to the animal when it’s attempting to stand upright. Circle rebreathing systems common to most human and veterinary anesthetic machines are suitable for use in small ruminants (<150 kg).
    2. Table 5: Inhalant Anesthetics Used in Ruminants 
         Agent       Oxygen Flow       Vaporizer Setting (MAC)   
         Isoflurane       Induction: 20 ml/kg/min   
         Maintenance: 12 ml/kg/min   
         Induction: 3 - 5%   
         Maintenance: 1.5 - 3%    
         Sevoflurane       Induction: 20 ml/kg/min   
         Maintenance: 12 ml/kg/min   
         Induction: 4 - 6%   
         Maintenance: 2 - 4%   
    3. Parenteral Anesthetics: Generally used to induce anesthesia prior to inhalant anesthesia or for short-term procedures. As an alternative to inhalants, a combination of xylazine, ketamine, and guaifenesin has been used to induce and maintain anesthesia as a constant rate infusion. This combination is associated with minimal cardiopulmonary depression. However, intubation with supplemental oxygen and a stomach tube are recommended. Repeated doses of the parenteral agents discussed above have also been used to maintain anesthesia, but intubation and maintenance with an inhalant anesthetic is preferred.

    5. Ruminant Anesthetics and Combinations

    1. Table 6: Injectable Anesthetics Used in Ruminants 
         Drug       Route       Sheep Dose   
         (mg/kg)
         Comments   
         Induction           
         Propofol       IV       2 - 6 (induction)   
         0.3 - 0.5 mg/kg/min   
         Rapid recovery   
         Maintenance infusion   
         (Discard unused portion)   
         Alphaxalone       IV       1.2 - 6       Induction   
         Dexmedetomidine +   
         Ketamine   
         IM   
         IM   
         0.015 IM +   
         1 IM   
         Atipamezole used for reversal   
         (0.1-0.2 mg/kg IV or IM).   
         Ketamine   
         1000 mg = 10 ml of 100 mg/mL   
         Xylazine   
         100 mg = 1 ml of 100 mg/mL   
         Butorphanol   
         10 mg = 1 ml of 10 mg/mL   
            
         IV   
            
         IV   
            
         IV   
         0.1 ml/20 lbs       Total volume = 12 ml   
         Small ruminant combination agent   
         Diazepam +   
         Ketamine   
         IV       0.5 - 1 mg/kg +   
         3 mg/kg IV to effect   
       
         Telazol       IV   
         IM   
         1.1 - 5.5   
         2 - 6
         Rapid onset. Anesthesia more   
         profound than ketamine-diazepam.   
         Total intravenous anesthesia   
         (TIVA)   
           
         Triple Drip   
         (Guaifenesin, Ketamine & Xylazine)   
         IV       induction: 0.5 - 2 ml/kg   
         maintenance: 0.7 - 2.6 ml/kg/hr   
         Given "to effect" for intubation and   
         continue on a slow drip until isoflurane   
         has taken effect.
    2. For additional combinations, please contact ULAM veterinarians.

    6. Neuromuscular Blocking Agents (NMBA)

    1. Extreme care must be taken to ensure that a proper level of anesthesia and analgesia is achieved prior to administering a neuromuscular blocking agent.
    2. Neuromuscular blocking agents require special monitoring procedures which are detailed in Anesthesia and Sedation Monitoring Guidelines.
      1. Concurrent positive pressure ventilation is required. Reversal of NMBAs with neostigmine and glycopyrrolate is possible under specific conditions. Please consult the ULAM veterinarians for instructions on NMBA reversal.
      2. Table 7: Neuromuscular Blocking Agents 
           Drug       Sheep Dose   
           (mg/kg)   
           Route       Duration of   
           Effect   
           Vecuronium       0.004       IV       14 minutes   
           Pancuronium       0.005       IV       21 minutes   

    7. Local Anesthetics

    1. Appropriate for minimally invasive procedures such as skin biopsy, or as a supplement to sedation, anesthesia and analgesia.
      1. Local anesthetics are excellent analgesics for use in minor procedures or as "splash blocks" for post-operative incision pain.
      2. Local anesthetics can be administered via a wound soaker catheter or epidurals. Contact ULAM veterinary staff if interested.
      3. Table 8: Local anesthetics 
           Drug       Dose (mg/kg)       Route       Duration of Effect       Notes   
           Lidocaine       <6 (<3 ml/kg of   
           a 2% solution)   
           Infiltrate       0.75 - 2 hours   
           (1 - 5 minute onset)   
           May need to dilute to   
           achieve appropriate   
           volume for infiltration.   
           Bupivacaine       <2 (<0.8 ml/kg of   
           a 0.25% solution)   
           Infiltrate       4 - 8 hours   
           (30 minute onset)   
           May need to dilute to   
           achieve appropriate   
           volume for infiltration.   

    8. Analgesics

    1. Signs of pain in ruminants may include, but are not limited to, the following:
    2. Table 9: Signs of Pain 
         Observational Signs              Physical Exam Signs   
         Lethargy              Elevated Body Temperature   
         Rigid Posture              Elevated Respiratory Rate   
         Restless              Elevated Heart Rate   
         Shifting Weight              
         Vocalization              
         Kicking at Painful Area              
         Teeth Grinding              
         Reduction in Feed Intake              
         Tail Swishing              
    3. Assessment of pain in ruminants can be challenging to recognize due to their stoic temperament and the natural instinct of prey animals not to attract the attention of predators when injured. Behavioral changes associated with pain in ruminants, as well as physiologic parameters such as body temperature or respiratory rate may not always be reliable indicators of pain.
    4. Table 10: Analgesics in Ruminants 
         Analgesic       Route       Dose (mg/kg)       Frequency       Comments   
         Opioids        
         Buprenorphine       IV   
         IM   
         0.006   
         0.005 - 0.01   
         4 - 6 hours       Slow onset of action   
         Butorphanol    IV   
         IM   
         0.05 - 0.5       2 - 4 hours       Administer in combination with α-2   
         agonist or acepromazine. Unreliable   
         sedation.  Ataxia and restlessness   
         when administered alone.
         Fentanyl a       Transdermal       2 µg/kg/h    40 hours       Sedation may be noted. The ideal time   
         for preemptive administration is 12 - 24   
         hours prior to surgery. See directions   
         below for application.
        NSAID's          Potentially valuable for preemptive analgesia in ruminants.      
         Carprofen       SC       4       24 hours       More selective inhibitor of COX-2.   
         Meloxicam       PO       2 mg/kg 1st day
         then 1 mg/kg PO   
         24 hours       More selective inhibitor of COX-2.   
         Flunixin   
         meglumine   
         IV       1.0 - 2.2       24 hours       Lower doses are recommended in goats   
         rather than in sheep. Non-selective COX   
         inhibitor.
         Ketoprofen       IM or IV       1 - 3       24 hours       Up to 3 days. Non-selective COX inhibitor.   
         Phenylbutazone       PO       5 - 10       24 hours       NOT recommended for sheep; okay for   
         goats and cattle. Non-selective COX   
         inhibitor.
      a Clip site with clipper blades carefully to not graze or cut the skin. Clean skin with a 70% v/v chlorhexidine/ alcohol solution. Allow skin to fully dry before patch application. After application, wrap the site with a single layer of elastic conforming bandage (Vetrap, 3M) held in place with sticking plaster (Tensoplast Vet, Smith & Nephew). This method ensures good patch/skin contact with no slippage. See figure 2 in Christou 2015.

    9. Anesthetic Emergencies

    1. In the event of an anesthetic crisis, turn anesthetic gases off and contact a ULAM veterinarian at (734) 936-1696 or (734) 764-0277 immediately. Use the following guidelines to support the animal until the veterinarian arrives:
      1. Ensure a patent Airway: Place an endotracheal tube or confirm patency of tube already in place.
      2. Assist in Breathing if necessary: Turn anesthetic gases off and ventilate with 100% oxygen. A rapid ventilatory rate (30 per min) is recommended to remove carbon dioxide, prevent acidosis, and decrease cerebral pressure.
      3. Provide Cardiovascular Support as indicated: Chest compressions in ruminant species are often futile due to animal size. Administer the following agents as indicated by the situation:
      4. Table 11: Emergency Drugs 
           Atropine       0.1 mg/kg IV       If severely bradycardic heart rate.   
           Epinephrine       0.01 mg/kg IV       If no detectable heart beat.   
           Crystalloid fluid bolus       60 ml/kg IV       Following administration of either above   
           agent, or if heart beat is present, lung   
           sounds are clear, blood pressure is not   
           high, and no other agent is given.   
    2. Please contact the ULAM Training Core at ULAM-trainingcore@umich.edu or 734-763-8039 if further instruction on emergency resuscitation is desired
  • References

    1. Ahern BJ, Soma LR, Rudy JA, Uboh CE, Schaer TP. Pharmacokinetics of fentanyl administered transdermally and intravenously in sheep. Am J Vet Res. 2010 Oct;71(10):1127-32.
    2. Christou C, Oliver RA, Rawlinson J, Walsh WR. Transdermal fentanyl and its use in ovine surgery. Res Vet Sci. 2015 Jun;100:252-6.
    3. Flecknell P. 2015. Laboratory Animal Anesthesia. Academic Press, New York, NY.
    4. Hefti A, Schlemmer I, Sauter-Louis C, Metzner M. Comparison of three different anesthesia procedures in calves with respect to possible pain-associated reactions. Berl Munch Tierarztl Wochenschr. 2012 Jul-Aug;125(7-8):315-25. German. PubMed PMID: 22919925.
    5. Muir et al. 2012. Handbook of Veterinary Anesthesia. CV Mosby Co. St. Louis, MO
    6. Plumb DJ. 2015. Plumb’s Veterinary Drug Handbook, 8th Edition. Blackwell Publishing. Ames, IA.
    7. Pugh DG, ed. 2012. Sheep & Goat Medicine. Saunders. Philadelphia, PA.
    8. Riebold, TW. 2002. Ruminant Anesthesia. In.Greene SA, ed. Veterinary Anesthesia and Pain Management Secrets. Philidelphia:Hanley&Belfus, Inc. p 253-262
    9. Stock ML et al. Pharmacokinetics of intravenously and orally administered meloxicam in sheep. Am J Vet Res. 2013 May;74(5):779-83.
    10. Torres MD et al. Effects of an intravenous bolus of alfaxalone versus propofol on intraocular pressure in sheep. Vet Rec. 2012 Mar 3;170(9):226.
    11. Zullian C et al. Plasma concentrations of buprenorphine following a single subcutaneous administration of a sustained release formulation of buprenorphine in sheep. Can J Vet Res. 2016 Jul;80(3):250-3.
Species: Cows Sheep
Questions?

If you have questions or comments about this document, contact ULAM Veterinary Staff (ULAM-vets@umich.edu or 734-936-1696).

The ULAM Training Core (ULAM-trainingcore@umich.edu or 734-763-8039) can be contacted to provide training in techniques at no charge.

For any concerns regarding animal health after work hours or on holidays/weekends, contact DPS (3-1131) who will contact the on-call veterinarian.