STERILIZATION IN PET ANIMAL PRACTICE

STERILIZATION IN PET ANIMAL PRACTICE

 Indramani Nath and Jayakrushna Das

Department of Veterinary Surgery and Radiology, College of Veterinary Science and Animal Husbandry, O.U.A.T., Bhubaneswar – 751 003.

The term sterilization/ castration are used to mean removal of the testicles or removal of the ovaries. But by common use the term is only confined to removal of testicles. Removal of ovary is denoted by the term spaying or oophorectomy. The term ovariotomy is used for removal of diseased ovary rather than normal ovary.

Indications:

1. Prevention of breeding nuisance (population control of stray dogs) to reduce prevalence of rabies.
2. Neoplastic growths or crushing injuries affecting the testicle.
3. In enlarged prostrate.
4. Perineal hernia.
5. To make the animal more docile and domesticated.
6. To avoid fighting tendencies in Tom cats.
7. The urine of male cat has a strong pungent smell and this smell is much less after castration.

Anesthetic protocols:

1. Xylazine- Atropine- Ketamine- Diazepam Pre-medication

• Xylazine @ 1mg/ kg b wt (administered intramuscularly, maximum dose 1ml)
• Atropine @ 04mg/ kg b wt (however, there is increasing evidence that atropine should not be given as a premedicant and should only be administered following induction to maintain cardiac output).
  

  Induction:

  To be given 10 minutes after administration of Xylazine and Atropine.

  • Ketamine @ 5mg/ kg b wt + Diazepam @ 0.25mg/ kg b wt.
  • Mix equal volumes of ketamine (50mg/ ml) and diazepam (5mg/ ml) in the same syringe.
  • Dose: 1ml of mixture per 10 kg bw, given slowly intravenously to effect, to premedicated

  Maintainance:

  Increments to be given at half the induction dose.

  Fluid therapy:

  Ringer’s lactate should be administered by I/V route throughout the surgical procedure.

  Respiration:

  • Open mouthed with gag and spontaneous respiration/ via endotracheal
  • Endotracheal tube inserted cuff inflated if necessary.

  N.B. Anesthetic overdose of xylazine can be reversed by using yohimbine hydrochloride @ 0.1mg/ kg b wt I/Vly.

   

  1.  Anesthetic protocol 2

  Triflupromazine/ Atropine/ Thiopentone or Xylazine/ Atropine/ Thiopentone Premedication:

  • Triflupromazine @ 1mg/ kg b wt or Xylazine @ 1mg/ kg b wt
  • Atropine @ 04mg/ kg b wt

  Note: the combination of Xylazine-Ketamine-Thiopentone is not considered safe for old, weak, and young patients and it is recommended that Protocol 2 be used only by an experienced vet.

  Induction:

  Thiopentone @ 25mg/ kg b wt I/V.

  (Note Perivenous administration of thiopentone sodium will cause severe local reaction and must be treated with local infusion of at least three times the volume of sterile saline; this risk can be reduced by the use of a 2.5% solution and by ensuring that thiopentone sodium is given by intravenous route only. Facility of artificial ventilation using oxygen with the help of AMBU bag must be in reach while following this protocol).

  Maintainance:

  I/V Thiopentone at half the induction dose may be repeated as small I/V boluses but will lead to prolonged anesthesia and longer recovery time.

  Fluid therapy and Respiration:

  Same as Protocol 1.

  The surgeon should use the anesthetic technique with which he is most familiar.

  Sterilization Surgery: General Considerations

  The choice of surgical approach is at the discretion of the veterinary surgeon.

  As with all surgery, great attention must be paid to ensure that Halstead’s surgical principles are diligently followed which includes

  • Complete asepsis
  • Accurate hemostasis
  • Careful tissue apposition
  • Gentle tissue handling
  • Obliteration of dead space
  • Post operative rest

  The timing of operation

  The dogs can be sterilized at any stage of estrous cycle because it is easy to grasp the ovaries due to enlarged size. However, since estrogen can delay blood clotting it is important to provide proper hemostasis for female dogs that are operated in estrous.

  Surgical procedure for female dogs

  1. Right flank approach (not recommended for pregnant and pyometra cases)
  • The right flank method of surgery has been considered as the ideal and preferred method for
  • The dog is positioned lying on its left side and the abdominal cavity is entered through the right flank with the ventral aspect of the dog directed towards the surgeons.

  Location of incision site for flank spaying

  • In adult bitches incision is made about 4cms behind the most caudal curve of the last rib, parallel to spine and about 9cms ventral to the transverse processes of the lumbar vertibrae.
    • The incision often falls at the cranial end of the fold of skin connecting the stifle to the abdominal In young bitches (under 6 months), the incision is placed more caudally. Failure to do this in young dogs results in difficulties in exteriorizing the uterine body near the bifurcation/ cervix to allow identification and removal of the second uterine horn.
    • Note: The right ovary is more closely adhered to the right kidney and body wall than the left ovary and thus easier to exteriorize if incision is made on the right flank.

    Tissues incised

    Skin, Subcutaneous tissue or fascia, external abdominal oblique muscle, Internal abdominal oblique muscle and Transverse abdominal muscle to which the peritoneum is often attached.

    The skin is cut with a scalpel. Subsequent layers are separated using scissors and blunt dissection. Incising the three muscle layers can cause hemorrhage. Splitting the muscles along their fibers reduces bleeding, causes less trauma and faster healing, but may result in a smaller aperture in which to work.

    Inexperienced surgeons often find gaining entry to the abdominal cavity the most challenging part of this approach. Cutting these muscle layers is easiest if they are located using Allis tissue forceps by an assistant and if the surgeon’s scissors are held perpendicular to the body wall.

    The steps of spaying by this approach are as follows

    1. locating the uterine horn and ovary
    2. clamping the ovarian blood vessels
    3. securely tightening ligature in place around the ovarian vessels
    4. clamping the uterus and blood vessels just above the cervix.
    5. securely tightening ligature over the groove made by the clamp
    6. the ovarian vessels are cut from the ovary
    7. ovary and uterus are removed taking care
    8. wound closure

    Advantages of flank approach

    • The wound is under less tension than with midline incision since the three separate muscle layers each individually sutured (catgut can safely be utilized in this space). Wounds are not under the weight of abdominal
    • Post operative checking and dressing can be carried more easily in difficult animals.
      • Should wound breakdown occur following release of the patient, life threatening complications is unlikely unless a lengthy incision was made.
      • Less tension in incision area and increased vascularity can reduce healing time.
      • In young lean animals the spay can easily be performed through a very small incision.
      • Animals can be released earlier than with midline.

      Disadvantages of flank approach

      • Approach is more traumatic (i.e. through three muscle layers) rather than midline, and therefore increased post-operative pain is possible.
      • Access to the left ovary or cervix may be more difficult, especially if the initial incision was incorrectly placed.
      • Retrieval of a dropped ovary or bleeding ovarian stump or pedicle is difficult: if this occurs, the recommended procedure is to quickly suture the skin wound and prepare the dog for exploratory laparotomy via a ventral midline approach. Once the problem is addressed, the procedure is completed via the midline and then the flank incision is closed in layers as normal.
      • Cutting through the three muscle layers can cause bleeding which may be sufficient to obscure the surgical field and can lead to increased risk of post-operativer infection
      • Severe reaction to catgut can Degradation sometimes produce swelling within the muscle and needs to be monitored. As it is a favorable site for infection.

      Midline Spay Technique Approach

      • Tissue incised skin, subcutaneous tissue, linea alba – white fibrous tissue (aponeurosis) and

      peritoneum.

      • The incision extend from one inch caudal to the umbilical scar.
      • Precaution taken not to make incision
      • Spaying is done as in flank.
      • Closure is done in one layer using vicryl as catgut degrades too quickly and linea alba heals Nylon sutures are recommended for skin closure.

      Advantages

      • Less hemorrhage
      • Less post-operative pain
        • Incision can be extended in case of complication like hemorrhage or dropped peddicle.
        • Most familiar technique to the surgeon.

        Disadvantage

        • Failure to give incision on exact midline makes the incision paramedian.
        • The wound is more inaccessible for post-operative care in fearful animal.
        • Longer convalescence period because of slow healing.
        • Incision is under the full weight of the abdominal organ and increased risk of wound break down and herniation.

         

        https://www.pashudhanpraharee.com/animal-birth-control-procedure-to-control-population-of-street-dogs/

        Clinical Complications

      • 1.     Hemorrhage

        • Hemorrhage occur during tearing of ovarian vascular complex while stretching/ breaking suspensory ligaments.
        • Bleeding can occur due to tension on the uterine body.
        • Indisual ligation of the large vessels (fat dog)
        2. Recurrent sign of estrous or heat
        • Occurs due to remnant of ovarian tissue.
        3. Uterine stump pyometra
        • If any portion of uterus is not removed this complication occurs when it is recommended to do complete ovariohysterectomy rather than tubectomy or ovarioctomy.

        Surgical Procedure of castration in male dog

      • Approach

        • Males are castrated through a single pre-scrotal incision.
        • One testicle is advanced cranially and skin is incised over the tensed testicle.
        • In sub-cutaneous tissue, dartos and external spermatic fascia are incised.
        • The testicle within the spermatic sac is grasped and pulled free.
        • The spermatic sac is then incised at its most ventral part.
        • The vaginal tunic is reflected revealing the testicle and associated structure.
        • The vaginal tunic is separated from the tail of the epididymis by breaking the ligamnetous attachmen leaving the tecsticle attached to the spermatic vessels in one bundle and ductus deference by the mesorchium.
        • The ductus deference and spermatic vessel clamped and ligated. Once the vessels are ligated the testicle is severed from The spermatic vessels usually retract after severance.
        • The contra-lateral testicle is now advanced in to skin incision and removed as usual.
        • It is a good practice to suture the vaginal tunics of the two testicles so that potential opening in to the abdominal cavity is Skin is sutured as usual.
        • Particular must be paid to ensure hemostasis, to reduce the chance of post-operative hematoma, considerable post-operative bruising and swelling is common.
        • The technique in other pet animals like cat, mongoose, guinea pig and rabbit are similar after proper anesthesia.
        • https://www.frontiersin.org/articles/10.3389/fvets.2020.00342/ful

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