TECHNIQUE

Caudal Epidural Anaesthesia in Sheep 

Summary Information
Type of technique Health & Management / Ruminants Pain Management / INDIVIDUAL Technique:
Synonyms and Keywords --
Description Caudal epidural anaesthesia involves injection of local anaesthetic and/or other appropriate drugs into the epidural space at the sacro-coccygeal or first intercoccygeal junction in order to produce analgesia of the tail, perineum, genitalia and pelvic viscera. (B342.16.w16)

Injection into the sacrococcygeal space:
  • Restrain the ewe in a standing position against a wall; if recumbent then place in sternal recumbency. (J15.13.w4)
  • Clip and surgically prepare an approprite area over the sacrum and anterior coccygeal vertebrae (sacrum and tail base) to produce an aseptic area. (J15.13.w4; B205.13.w13); an area 20 cm wide by 40 cm long suggested (J15.13.w4).
  • Locate the sacrococcygeal space. 
    • Gently raise and lower the tail to find the most anterior sacrococcygeal articulation, a depression cranial to a line drawn between the tuber ischii, at which only slight movement is felt when the tail is manipulated. 
      • For the first intercoccygeal joint there will be obvious movement when the tail is manipulated. (J15.13.w4)
      • The sacrococcygeal space is located by palpation at the most cranial point of articulation when the tail is moved up and down. (B205.13.w13)
      • Move the tail with one hand and feel for the site of needle insertion with the other. (B359.App8.w30)
  • Accurately determine the midline. This may be simple in a thin individual; in fatter individuals it may be determined by placing the thumb and middle finger on either side of the sacrum then placing the index finger in the midline over the sacrococcygeal space so that the three digits form a triangle. (J15.13.w4)
  • Insert a 1 to 1.5 inch (2.5 to 3.75 cm) long, 20 or 21 gauge needle, with the bevel of the needle facing cranially, at an angle of about 45 degrees to the skin. (J15.21.w4)
    • At approximately 45 degrees to the curvature of the rump (B205.13.w13)
    • At an angle of 30 to 45 degrees cranially. Note that the angle varies considerably between individuals. (J15.13.w4)
    • Insert at an angle of 20 degrees to the horizontal. (J15.18.w2)
    • Insert a 20 gauge needle midline, directed cranially, at approximately 45 degrees to the spine curvature of the rump to allow the needle to enter the vertebral column. (B359.App8.w30)
  • Advance the needle until it enters the epidural space or touches bone. If it touches bone it must be redirected. When the epidural space is reached there is often a reflex waggle of the tail and a mild pain reaction. (J15.13.w4).
    • A "pop" may be felt as the needle passes through the interarcuate ligament and into the epidural space. (B359.App8.w30)
    • Lack of contact with bone during insertion of the needle, and lack of resistance to injection, indicate correct placement. (J15.18.w2)
    • If the needle passes through to touch the floor of the vertebral canal, it should be pulled back slightly (about 1 mm), clear of the bone, before injecting. (V.w69)
  • Inject the anaesthetic solution. This requires little pressure if the needle is within the epidural space. If a small air bubble is left in the syringe over the local anaesthetic the attempting to inject into the wrong space will cause the bubble to be compressed. (J15.13.w4)
    • Inject 1 ml of local anaesthetic initially and wait for one minute, assessing response. If a response results (indicating correct placement) then inject increments of 0.5 ml to reach the desired affect. (J15.13.w4)
      • Note that if doses of more than 2.0 ml are injected this may result in hindlimb incoordination. (J15.13.w4)
    • Inject about 2 ml of 2% lidocaine. (J234.12.w2)
      • Doses greater than 3 ml of 2% lidocaine in sheep or goats (of about 60 kg bodyweight) may result in hindlimb incoordination and recumbency. (J234.12.w2)
    • 2 ml of 2% lidocaine is sufficient for a 60 kg ewe if a short duration anaesthetic is required. (B359.App8.w30); for an effect of at least 24 hours use 1.75 ml 2% lidocaine mixed with 0.25 ml of 2% xylazine. (B359.App8.w30)
    • Inject about 2 ml (range 1 to 4 ml) of 2% lidocaine; xylazine at 0.05 mg/kg may be added to prolong the analgesia for up to 36 hours. (B205.13.w13)
  • Allow several minutes for analgesia to develop after injection. (B205.13.w13)
  • Development of tail flaccidity indicates successful anaesthesia. (J15.21.w4)
  • A small number of sheep may show mild ataxia and pelvic limb weakness but can maintain sternal recumbency and may stand when approached. (J15.18.w2)
  • If there is no response then the drug was not injected into the correct place. (J15.13.w4)

Injection into the first intercoccygeal space:

  • In fat ewes or individuals in which the sacrococcygeal space does not allow entry of a needle then the first intercoccygeal space may be used.. (J15.13.w4)
  • For injections into the first intercoccygeal space the procedure is similar to that for injection into the sacrococcygeal space, however the space is much smaller therefore penetrating it accurately is more difficult. (J15.13.w4)
  • When the tail is gently raised and lowered there will be obvious movement at this joint. (J15.13.w4)
  • 1 to 4 ml of 2% lidocaine is injected with the needle held at right angles to the skin; loss of resistance to injection occurs when the needle enters the epidural space. (J15.22.w1)

Epidural analgesia for tail docking in lambs (J3.79.w1)

  • Position the lamb standing and held to minimise movement of the hind quarters. (J3.79.w1)
  • Locate the sacro-coccygeal or first inter-coccygeal space by moving the tail up and down in a vertical plane and palpating the depressions between the sacral and coccygeal, or inter-coccygeal spines. (J3.79.w1)
  • Insert the needle downwards and forwards. (J3.79.w1)
  • Inject the appropriate amount of local analgesic agent. (J3.79.w1)
  • 0.75 to 1.0 ml of 1% lidocaine is sufficient. (B205.13.w13)
  • Analgesia is considered to have occurred when muscle control of the tail has been completely lost; elapse of an additional five minutes is recommended to ensure full analgesia. (J3.79.w1)
  • Slight ataxia of the hind limbs may occur in some individuals following epidural injection of local anaesthetic. (J3.79.w1)

Epidural catheterisation:

Placement of an epidural catheter may be used to allow continuous caudal block to give relief from painful conditions of the vagina and rectum resulting in severe continuous straining. (B205.13.w13)

  • The catheter is placed into the epidural space using a Tuohy needle.
  • Insert a 5 cm, 17 gauge spinal needle (Tuohy needle) with the bevel directed craniad. (B205.13.w13, J234.12.w2)
    • The needle has a curved end which directs the catheter. (B205.13.w13, J234.12.w2)
  • Remove the stylet and inject 2 ml lidocaine solution to confirm that the tip is placed in the epidural space. (J234.12.w2)
  • Insert the catheter through the needle and advance 6 to 8 cm into the epidural space. (B205.13.w13); for 2-4 cm beyond the tip of the needle. (J234.12.w2)
  • Withdraw the needle leaving the catheter in place. (B205.13.w13, J234.12.w2)
  • Secure the catheter in position using adhesive tape sutured to the skin. (J234.12.w2)
  • The free catheter end must be protected to ensure that injections into the catheter will be sterile; for example the catheter may be capped and then wrapped in sterile gauze. (B205.13.w13, J234.12.w2)
  • Local analgesic solution is injected whenever the animal shows signs that sensation to the blocked region is returning, or at 2-4 hour intervals. (B205.13.w13, J234.12.w2)
Appropriate Use (?)
  • Anaesthetises the vulva, vagina, perineum. (J15.13.w4)
  • "Provides excellent perineal analgesia and muscle relaxation, minimal cardiovascular and respiratory effects, and rapid recovery." (J234.12.w2)
  • Reduces stress associated with procedures involving the vulva, vagina or perineum. (J15.13.w4)
  • Uses: vaginal or uterine prolapse, painful conditions of the vagina, removal of dead fetuses. (J15.13.w4)
  • For relief of pain associated with the posterior reproductive tract. For vaginal, uterine and rectal prolapses. (J15.18.w2)
  • For replacement of vulval prolapse. (B349.15.w15)
  • To relieve starting and facilitate replacement of prolapsed vagina and cervix. (B359.App8.w30)
  • To facilitate replacement of the prolapsed uterus. (B359.App8.w30)
  • Controls the pain while and after dead lambs are removed; care must be taken to ensure the operator does not damage the ewe while removing the lambs. (J15.13.w4)
  • For prolapses the procedure allows replacement without straining, relieves pain and allows easy stitching of the desensitised vulva. (J15.13.w4)
  • For vaginitis this technique controls the symptoms and prevents straining and the risk of prolapse, while the cause of the vaginitis is identified and treated. (J15.13.w4)
  • For amputation of the tail if this is required for therapeutic reasons. (B359.App8.w30)
  • For urethrostomy or amputation of the penis associated with urethral obstruction. (B359.App8.w30)
Notes
  • The procedure is easier to perform if the animal is held skillfully. (J3.79.w1)
  • Strict attention to aseptic technique is important. (B205.13.w13); the area in which the injection is to be made should be clipped and thoroughly cleaned with disinfectant and surgical spirit before the injection is made. (J15.21.w4)
  • It is advisable to keep treated individuals in separate pens to allow careful supervision and provision of extra feed. (J15.18.w2)
  • This technique is rapid. (J3.79.w1)
  • This technique requires only small volumes of local anaesthetic solution. (J3.79.w1)
  • The sacrococcygeal space is preferred but the first intercoccygeal space may also be used. (B359.App8.w30)
Doses and duration of analgesia:
  • Duration of analgesia following injection of local anaesthetic agent is generally 1-3 hours, depending on the drug and dose used. (J15.13.w4)
  • Following a single epidural injection of xylazine, caudal analgesia of up to 36 hours may be produced without marked associated sedation. (J15.18.w2)
  • A combination of xylazine and lignocaine produces rapid onset of analgesia (within two minutes) as well as prolonged action. (J15.18.w2)
  • Intramuscular administration of an NSAID (e.g. flunixin meglumine, 2 ml per 45 kg bodyweight, intramuscularly) may be given at the same time; note: this is not licensed for use in sheep in the UK. (J15.13.w4)
  • 0.5 mg/kg 2% lidocaine (2 ml for an adult 80kg ewe) provides caudal analgesia within two minutes and lasting for up to four hours. (J15.18.w2)
  • 0.07 mg/kg xylazine (0.25 ml of 2% xylazine) provides caudal analgesia for up to 36 hours. These can be used in combination. 5 mg/kg 2% lidocaine. (J15.18.w2)
  • Lidocaine at 2 ml (1-4 ml) of 2% solution in adults; xylazine at 0.05 mg/kg may be added to prolong the analgesia for up to 36 hours. (B205.13.w13)
  • For a short duration anaesthesia use 2 ml of 2% lidocaine in a 60 kg ewe. (B359.App8.w30)
  • For an effect of at least 24 hours use 1.75 ml 2% lidocaine mixed with 0.25 ml of 2% xylazine. (B359.App8.w30)
Complications/ Limitations / Risk
  • Problems in the use of epidural analgesia include lack of skill of handlers and difficulties in maintaining high hygiene standards under farm conditions. (J3.79.w1)
  • Use of epidural anaesthesia on large numbers of lambs in dirty farm yards would risk the development of spinal abscesses in some individuals and may also lead to overdose in some individuals. (P61.53.w1)
  • A small number of sheep may show mild ataxia and pelvic limb weakness but can maintain sternal recumbency and may stand when approached. (J15.18.w2)
  • Injection into the first intercoccygeal space may be less reliable for production of anaesthesia than injection into the sacrococcygeal space. (J15.21.w4)
  • It may be difficult to identify the first intercoccygeal space in tail docked sheep. (J234.12.w2)
  • Doses greater than 3 ml of 2% lidocaine in sheep or goats (of about 60 kg bodyweight) may result in hindlimb incoordination and recumbency. (J234.12.w2)
  • Rare complications include postural instability, recumbency, haemorrhage if a venous sinus is punctured and infection if sterility is not maintained during the procedure. (J234.12.w2)
Equipment / Chemicals required and Suppliers
  • 20 gauge (0.9mm) 1.5 inch needle (J15.13.w4, J15.18.w2); 1 to 1.5 inch needle, 20 or 21 gauge (J15.21.w4); 2.5 to 3 cm long, 19 or 20 gauge needle. (B359.App8.w30)
  • 2 ml or 5 ml syringe (J15.13.w4, J15.18.w2)
  • Local anaesthetic agent such as 2% lidocaine. (J15.13.w4)and/or xylazine (J15.18.w2). 
  • 2 ml of 2% plain lidocaine (no adrenaline) for a 75 kg ewe for short-acting effect. (J15.21.w4)
  • 1.75 ml lidocaine plus 0.25 ml 2% xylazine for a 75 kg ewe for longer effect (e.g. 24 hours) (J15.21.w4)
  • 1.75 ml of 2% lidocaine mixed with 0.25 ml 2% xylazine in a 65 kg ewe to provide relief from straining foe 24 hours or more. (B359.4.w4)
  • Clippers or scissors (J15.13.w4)
  • Surgical scrub (J15.13.w4)
Expertise level / Ease of Use
  • Procedure should only be undertaken by an individual with appropriate clinical training and practical experience; this would usually be a veterinarian or someone with advanced veterinary technician training.
  • Practice is required to learn this technique and become familiar with it. (J15.13.w4)
  • "This is a technically difficult procedure which can only be done by a veterinary surgeon." (D153)
Cost/ Availability
  • Inexpensive.
Legal and Ethical Considerations
  • Following the procedure, the animal should be maintained in a separate pen to allow extra supervision and additional feeding and attention. (J15.18.w2)
  • Accurate identification of treated individuals, and accurate recording of treatments given, are essential to comply with legislation regarding drug withdrawal times. (J15.18.w2)
  • Note: xylazine is not licensed for use in sheep in the UK. A minimum 35-day withdrawal period must be observed following xylazine administration. (J15.18.w2)
In some countries there may be legislation restricting the use of this type of technique to licensed veterinarians. For example in the UK: "The Veterinary Surgeons Act 1966 (Section 19) provides, subject to a number of exceptions, that only registered members of the Royal College of Veterinary Surgeons may practice veterinary surgery." (see: LCofC1 - RCVS Guide to Professional Conduct 2000 - Treatment of Animals by Non-Veterinary Surgeons).
Author Dr Debra Bourne MA VetMB PhD MRCVS (V.w5)
Referee Graham Bilbrough MA, VetMB, CertVA, MRCVS (V.w69)
References B205.13.w13, B342.16.w16, B349.15.w15, B359.4.w4, B359.App8.w30, J3.79.w1, J15.18.w2, J234.12.w2, P61.53.w1, D153, LCofC1 , V.w69

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