вторник, 18 сентября 2012 г.

An overview of pediatric spay and neuter benefits and techniques - Veterinary Medicine

Many veterinarians now perform these procedures in dogs and cats at an earlier age. The surgery is faster, the perioperative complication rate is lower - even the healing time is shorter than in adult animals.

Each year in the United States, millions of homeless or unwanted dogs and cats are euthanized in animal shelters and humane societies. While precise numbers are difficult to obtain, the Humane Society of the United States estimates that between three and four million dogs and cats are euthanized each year.1 Many factors have led to the overpopulation of dogs and cats, and the solution will be multifaceted, as well. Until safe and effective chemical or immunologic sterilization is available, ovariohysterectomy and orchiectomy will be the cornerstone of any program to reduce the overpopulation and, thereby, reduce the number of animals relinquished and euthanized each year.

The most effective way to ensure that animals adopted from shelters do not reproduce is to spay or neuter them before adoption. Voucher programs or prepaid spay-neuter programs in which arrangements are made at the time of adoption to have an animal spayed or castrated at a later date simply do not work for the majority of these animals. The national compliance rate of these programs is < 40%.24 With preadoption spays and castrations, compliance is not an issue, obviously.

In the shelter environment, we recommend spaying or neutering dogs and cats before adoption and as young as 6 weeks of age. In a practice treating owned animals, we recommend scheduling one more appointment at the end of the puppy or kitten vaccination series. With this schedule, puppies and kittens are spayed or neutered before 5 months of age, before sexual maturity.

Ovariohysterectomy or orchiectomy of pediatric dogs and cats is supported by the American Veterinary Medical Association (AVMA) and is becoming increasing popular, especially in the shelter and high-quality, high-volume spay-neuter environments. The AVMA policy statement says, 'The AVMA supports the concept of pediatric spay/ neuter in dogs and cats in an effort to reduce the number of unwanted animals of these species. Just as for other veterinary medical and surgical procedures, veterinarians should use their best medical judgment in deciding at what age spay/neuter should be performed on individual animals/'5 Other organizations supporting pediatric neutering are the Canadian Veterinary Medical Association,6 the British Small Animal Veterinary Association,7 and the American Animal Hospital Association.8

ADVANTAGES OF PEDIATRIC SPAY AND NEUTER

In addition to the commonly accepted health benefits associated with ovariohysterectomy and orchiectomy, such as reducing the incidence of mammary neoplasia and behavioral problems, pediatric (between 8 and 16 weeks of age) spay and neuter offer additional advantages. They are effective tools for dealing with the overpopulation of unwanted dogs and cats. The surgical procedures are easier, faster, and less expensive than they are in adult animals.9,10 With shorter surgery times and shorter anesthetic episodes, the incidence of perioperative complications is low.9 Anesthetic recovery and healing are shorter than in adults as well.9,11

HISTORICAL CONCERNS

Historically, veterinarians have expressed concerns about pediatric spay and neuter. The concerns have focused on either potential long-term physiologic effects or anesthetic risk.

Physiologic effects

The adverse physiologic effects mentioned have been obesity, stunted growth, musculoskeletal disorders, perivulvar dermatitis, puppy vaginitis, feline lower urinary tract disease, and urinary incontinence. Most concerns appear to be unfounded.

Obesity. Obesity is a multifactorial problem with a tendency to occur regardless of the age at which an animal is spayed or neutered. A long-term study conducted by researchers at Cornell University followed 1,842 dogs that underwent gonadectomy and were adopted from a shelter before 1 year of age and followed for up to 11 years. The results revealed a decrease in obesity for male and female dogs that had early-age gonadectomy.12

Stunted growth. Initial concerns that pediatric neutering may result in stunted growth have proved to be false in dogs. Removal of the hormonal influence actually results in delayed closure of growth plates.13 The long bones of dogs that undergo pediatric neutering are a little longer than those of animals neutered after 6 months of age; however, the growth is not disproportionate, and the curve is the same.13 There does not appear to be any clinical relevance to the delayed physeal closure.13

Hip dysplasia. Some veterinarians have questioned if pediatric spay or neuter results in an increased incidence of hip dysplasia in dogs. Research on this subject has proved to be equivocal. A study at Texas A&M University showed no increase in hip dysplasia,14 while a study at Cornell University showed a slight increase in incidence.12 Interestingly, the Cornell study also showed that dogs sterilized at a traditional age were three times more likely to be euthanized because of hip dysplasia.12

Perivulvar dermatitis. Perivulvar dermatitis has been documented in intact and spayed female dogs. The age at the time of neutering appears to have no significant influence on the incidence.13 This condition is related to a recessed vulva and is made worse by obesity.

Puppy vaginitis. The incidence of puppy vaginitis is the same regardless of the age of the dog at the time of ovariohysterectomy12

Feline urinary obstruction. The suspicion that pediatric castration would decrease the diameter of the penile urethra in cats and, thus, lead to urinary obstruction has proved to be unfounded. The diameter of the penile urethra in an adult male cat does not vary between animals neutered at 7 weeks or at 7 months of age or from intact males.15-17

Urinary incontinence. Studies have shown differing conclusions with respect to estrogen-responsive urinary incontinence in dogs. The Cornell study mentioned above revealed a slightly greater risk of urinary incontinence in dogs spayed earlier than 12 weeks of age,12 while the Texas A&M study showed no difference.14 A third study showed a higher incidence of urinary incontinence in dogs spayed after their first estrous cycle.18

Anesthesia

Anesthetic management in the pediatric patient can be safe, provided appropriate attention is paid to a few basic principles and to the unique concerns associated with pediatric patients.

Given that metabolic development is largely complete by 6 weeks of age, the same anesthetic protocols that are used in adults can be safely used in pediatric patients.9'19 However, pediatric patients have lower body fat percentages, a decreased ability to shiver, and a larger surface-area-to-volume ratio. Each of these factors makes attention to the maintenance of body temperature critical. Pediatric patients are also at a greater risk of hypoglycemia. Body temperature and blood glucose concentration can be easily managed, allowing surgical anesthesia with minimal risk.9

Preoperative and intraoperative recommendations. Perform a preoperative physical examination on all patients.19 It is at the veterinarian's discretion whether the packed cell volume, total solids, blood urea nitrogen concentration, and glucose concentration are measured; however, these tests are usually not performed in the shelter environment.

According to the Association of Shelter Veterinarians guidelines for spay and neuter programs: 'Warmth is best preserved by reducing contact with cold surfaces, limiting body cavity exposure, and providing carefully protected contact with circulating warm water or heated containers, such as carefully monitored water bottles or rice bags. Forced hot air or convective warming can also be an effective means of maintaining body temperature perioperatively.'19 These measures in conjunction with a short surgical time and the reversal of anesthetic agents at the completion of surgery minimize hypothermia.20

Hypoglycemia can be avoided or minimized by restricting preoperative fasting to two to four hours, avoiding preoperative excitement, and feeding the patient a small amount of its regular food immediately upon anesthetic recovery.20,21

Anesthetic and analgesic protocol. Many anesthetic protocols have been recommended for pediatric surgery. Most recommend multimodal analgesia and avoid the administration of barbiturates, likely because these patients have minimal fat.22 In our experience, an intramuscular injection of a dexmedetomidine, ketamine, butorphanol combination (Tables 1&2) followed by maintenance with oxygen through either a face mask or an endotracheal tube and supplemented with isoflurane, if needed, is safe and effective. Following the injection, a surgical plane of anesthesia is achieved within five minutes and will last for up to 30 minutes.

The dexmedetomidine can be reversed with atipamezole immediately after surgery and will frequently result in the patient being mobile within five to 10 minutes (Tables 1&2). We recommend administering a nonsteroidal anti-inflammatory drug, such as meloxicam, after induction of anesthesia and before the start of surgery for postoperative analgesia according to the labeled dosages for cats and dogs.23

ORCHIECTOMY IN PEDIATRIC CATS

Feline pediatric orchiectomy is performed essentially the same as castration in adult cats. For a surgeon just starting to perform pediatric surgery, the most difficult aspect is localizing and securing the testicles for incision. The choice of an open or closed orchiectomy technique depends on the surgeon's preference. We prefer a scrotal approach and a closed orchiectomy technique, which are described here.10 A closed technique is no more difficult to perform than an open technique in pediatric patients and it does not require entry into the peritoneal cavity.

Place the anesthetized patient in dorsal recumbency with the rear legs pulled forward. Clip the scrotum and perineal area of hair, and perform a surgical scrub. Grasp the first testicle between the thumb and index finger, and secure it within the scrotum.

Make a scrotal incision over the testicle, and exteriorize the testicle from the scrotum with digital pressure. Apply gentle traction to the testicle and spermatic cord while stripping the fat and fascia from the spermatic cord with a gauze sponge. Use a hemostat tie for hemostasis and excise the testicle. To perform a hemostat tie, place the tip of the hemostat under the cord and then rotate the tip around the cord. Open the jaws of the hemostat as the distal (testicle) end of the cord is advanced around and into the hemostat jaws and clamped. Next, transect the cord between the clamp and testicle by using a scalpel blade or scissors.

After removing the testicle, push the knot off of the tip of the hemostat. Tighten the knot to ensure its security, but leave about 5 mm of tissue distal to the knot to ensure that it does not unravel.

Perform the identical technique on the second testicle, and leave the incisions open to heal by second intention.10

ORCHIECTOMY IN PEDIATRIC DOGS

Canine pediatric orchiectomy is performed essentially the same as feline pediatric orchiectomy is. The surgical incision is made in the scrotum just as in the cat. In most patients, only one scrotal incision is needed. We prefer a scrotal approach and a closed orchiectomy technique, which are described here.

Place the anesthetized patient in dorsal recumbency. Clip the scrotum of hair, and perform a surgical scrub. Grasp the first testicle between the thumb and index finger, and secure it within the scrotum.

Make a scrotal incision over the testicle, and exteriorize the testicle with digital pressure. Apply gentle traction to the testicle and spermatic cord while stripping the fat and fascia from the spermatic cord with a gauze sponge. Use a hemostat tie for hemostasis, and excise the testicle.

Move the second testicle into the surgical wound and incise the fascia overlying the testicle. The excision and hemostasis of the second testicle is performed in a manner identical to that of the first testicle, and the incision is left open to heal by second intention.

OVARIOHYSTERECTOMY IN PEDIATRIC CATS

Feline pediatric ovariohysterectomy is performed essentially the same as ovariohysterectomy in adult cats is; however, the structures are smaller and the exposure can be markedly less.

Place the anesthetized patient in dorsal recumbency, perform an abdominal surgical clip and scrub, and make an incision at the midpoint between the umbilicus and cranial brim of the pubis on the ventral abdominal midline. The incision can be as small as 1 to 2 cm in length. Excise any subcutaneous fat (there is usually none) in the surgical field, exposing the linea alba.

Make an incision in the linea alba. The linea alba is narrow in the pediatric cat, and it may be difficult to make the incision completely on the linea. There are, however, no adverse consequences if the incision is slightly paramedian. With the abdominal incision this far caudal, the urinary bladder can generally be easily visualized. Elevation of the bladder allows direct visualization of the uterine body and uterine horns. If the bladder is not visible, the uterine horn can be exteriorized with a spay hook.

Deliver one uterine horn through the incision. Apply enough caudal traction to the uterine body to expose the proper ligament and ovary. Clamp the proper ligament with a mosquito hemostat, and apply slight upward traction, exposing the suspensory ligament. Transect the suspensory ligament with scissors or a scalpel, and tear a hole in the broad ligament just caudal to the ovarian vessels. The ovarian vessels can be tied off and transected by using the same hemostat tie technique as in a feline orchiectomy.23

Gentle caudal traction on the first uterine horn will expose the uterine body and the second uterine horn. Expose the second ovary, and tie off and transect the second ovarian pedicle in a manner identical to that of the first.

Incise the broad ligaments to the uterine vessel on both sides to allow exposure of the uterine body. It is not necessary to remove the entire uterine body to the level of the cervix. One ligature placed with a Miller's knot without clamping the uterus is sufficient for hemostasis in pediatric patients. The suture type and size depends on the surgeon's preference; we prefer using 3-0 monofilament synthetic absorbable suture.

Create the Miller's knot by passing a length of suture material around the uterine body twice, creating a loop. Then pass the needle holders through the loop and create a standard square knot throw. Secure the knot, and tighten both loops evenly by elevating the loops as they are tightened, ensuring that the tissue is thoroughly compressed. Finish the Miller's knot with a series of square knots to prevent loosening. Then transect the uterine body distal to the ligature.

Closure consists of a simple continuous pattern in the body wall followed by simple interrupted subcuticular sutures to close the skin.10

OVARIOHYSTERECTOMY IN PEDIATRIC DOGS

Canine pediatric ovariohysterectomy is performed similar to ovariohysterectomy in a pediatric cat with only a few differences. The structures in the pediatric dog are smaller than in the adult dog. The ovaries are more easily exteriorized, and it is more difficult to exteriorize the uterine body. For these reasons, the abdominal incision in the pediatric dog is slightly caudal to that in the adult dog.

To perform this procedure, place the anesthetized patient in dorsal recumbency, perform a surgical clip and scrub, and make an incision just cranial to the midpoint between the umbilicus and cranial brim of the pubis on the ventral abdominal midline. Subcutaneous dissection on the midline exposes the linea alba, which is nicked with a scalpel blade. Extend the linea incision with scissors, exposing the abdominal contents. The urinary bladder may be visible, and if so, elevate it to allow direct visualization of the uterine body or uterine horns. If the bladder is not visible, exteriorize the uterine horn with a spay hook.

Deliver one uterine horn through the incision. Apply enough caudal traction to the uterine body to expose the proper ligament and ovary. Clamp the proper ligament with a mosquito hemostat, and apply slight upward traction, exposing the suspensory ligament. Transect the suspensory ligament with scissors or a scalpel, and tear a hole in the broad ligament just caudal to the ovarian vessels. Use a standard three-clamp technique on the ovarian pedicle, and transect and l�gate the pedicle. The suture type and size depend on the surgeon's preference; we prefer using 2-0 monofilment synthetic absorbable suture. Generally, only one ligature is necessary on each pedicle in a pediatric canine spay.

Gentle caudal traction on the first uterine horn will expose the uterine body and the second uterine horn. Expose the second ovary and transect and ligate the second ovarian pedicle in a manner identical to that of the first.

Incise the broad ligaments to the uterine vessel on both sides, allowing exposure of the uterine body. One ligature placed with a Miller's knot without clamping the uterus is sufficient for hemostasis in pediatric patients. Transect the uterine body distal to the ligature.

Closure consists of a simple continuous pattern in the body wall followed by interrupted or continuous subcuticular sutures to close the skin.10

POSTOPERATIVE CARE

Even though puppies and kittens recover rapidly from sterilization surgery, it is still important to attempt to minimize activity for three to five days after surgery Advise owners to keep surgical areas clean and dry and to seek veterinary care if bleeding, swelling, or separation of wound edges occurs.

CONCLUSION

Recognizing the shorter anesthetic and surgical times and lower complication rates for younger patients, many practitioners have begun performing spays and neuters at an earlier age in pets. Historically, practitioners have routinely seen kittens and puppies for a series of vaccinations and wellness visits between 6 and 16 weeks of age, and then advised owners to return a few months later for neutering. This gap in care may have contributed to many pets being spayed or neutered after puberty and after the birth of unintentional litters. By spaying and neutering pets at 4 or 5 months of age, two to three weeks after standard vaccinations, practitioners can allow time for the animals to develop immunity through vaccination while ensuring that they are neutered before sexual maturity. Since owners generally establish a routine of veterinary appointments for their pet during the wellness visits, there is no gap in veterinary care between the vaccine series and the surgical appointment and compliance may be improved.23

By performing spay or neuter surgery at this age, veterinarians are also able to ensure numerous health benefits for their patients, including a dramatic reduction in the risk of mammary tumors and the elimination or reduction of highly objectionable behaviors, including scent marking, spraying, fighting, and roaming. Additional benefits include avoiding the stresses and costs associated with spaying while in heat, with pregnancy, or with pyometra. Furthermore, spaying and neutering young puppies and kittens is technically easier for surgeons and more cost effective than neutering these pets once they are mature.

[Sidebar]

Pediatric spay and neuter are easier, faster, and less expensive than in adults.

[Sidebar]

Picturing the process

To see Dr. Bushby 's photographs of pediatric spay and neuter, go to dvm360.com /SpayNeuter.

[Reference]

REFERENCES

1. The Humane Society of the United States. Estimates of pet overpopulation. Available at: www.humanesociety.org/issues/ pet_overpopulation/facts/overpopulation_estimates.html. Accessed Dec. 20, 2010.

2. Manning AM, Rowan AN. Companion animal demographics and sterilization status: results from a survey in four Massachusetts towns. Anthrozoos 1992;5:192-201.

3. American Veterinary Medical Association. National shelter census results revealed. / Am Vet Med Assoc 1997;210(2):160-161.

4. Petsmart Charities. Motivators, barriers for pet adoption and spay/neuter. Available at: www.petsmartcharities.org/resources/adoption-spay-neuter-barriers-research .html. Accessed Dec. 20, 2010.

5. American Veterinary Medical Association. Pediatric spay/ neuter of dogs and cats. Available at: www.avma.org/issues/ policy/animal_welfare/spay_neuter.asp. Accessed Dec 20, 2010.

6. Canadian Veterinary Medical Association. Dog and cat spay/ castration. Available at: canadianveterinarians.net/ShowText. aspx?ResourceID=414. Accessed Dec 20, 2010.

7. British Small Animal Veterinary Association. Policy on neutering of cats. Available at: www.bsava.com/Advice/PolicyStatements/Neuteringofcats/tabid/161/Default.aspx. Accessed Dec 20, 2010.

8. American Animal Hospital Association. Pediatric neutering gonadectomy/overiohysterectomy/orchiectomy) of companion animals statement. Available at: secure.aahanet. org/eweb/DynamicPage.aspx?site=resources&webcode=refe renceDetail&postKey=lbc32a74-b97d-488f-8ae9-ec013839blc7. Accessed Dec 20, 2010.

9. Howe LM. Short-term results and complications of prepubertal gonadectomy in cats and dogs. JAm Vet Med Assoc 1997;211(l):57-62

10. BohlingMW, Rigdon-Brestle YK, Bushby PA, et al. Veterinary seminars in spay-neuter surgeries: pediatrics (video). Available at: vimeo.com/10283573. Accessed Dec. 20, 2010.

11. Faggella AM. Evaluation of anesthetic protocols for neutering 6- to 14-week-old pups . / Am Vet Med Assoc 1994;205:308-314.

12. Spain CV, Scarlett JM, Houpt KA. Long-term risks and beneftis of early-age gonadectomy in dogs. JAm Vet Med Assoc 2004;2243):380-38Z

13. Salmeri KR, Bloomberg MS, Scruggs SL, et al. Gonadectomy in immature dogs: effects on skeletal, physical, and behavioral development. JAm Vet Med Assoc 1991;198(7):1193-1203.

14. Howe LM, Slater MR, Boothe HW, et al. Long-term outcome of gonadectomy performed at an early age or traditional age in dogs. JAm Vet Med Assoc 2001;218(2):217-221.

15. Stubbs WP, Bloomberg MS, Scruggs SL, et al. Effects of prepubertal gonadectomy on physical and behavioral development in cats. JAm Vet Med Assoc 1996;20911):1864-1871.

16. Herron MA. The effect of prepubertal castration on the penile urethra of the cat. / Am Va Med Assoc 1972;160:208-211.

17. Root MV, Johnston SD, Johnston GR, et al. The effect of prepuberal and postpuberal gonadectomy on penile extrusion and urethral diameter in the domestic cat. Vet Radhl Ultrasound 1996;37:363-366.

18. Arnold S, Arnold P, Hubler M, et al. Urinary incontinence in spayed bitches: prevalence and breed predisposition. Eur ] Companion Anim Pract 1992;2:65-68.

19. Looney AL, BohlingMW, Bushby PA. The association of shelter veterinarians veterinary medical care guidelines for spayneuter programs. / Am Vet Med Assoc 2008;233(l):74-86.

20. Howe LM. Prepubertal gonadectomy in dogs and cats-part I. Compend Coniin Educ Pract Vet 1999;21(2):103-111.

21. Kustritz MV Early spay-neuter in the dog and cat. Vet Clin North Am Small Anim Pract 1999;294):935-943.

22. Cistola AM, Golder FJ, Levy JK, et al. Comparison of two injectable anesthetic regimes in feral cats at a large-volume spay clinic. Vet Anaesth Analg 20??�?2)?-?.

23. Griffin B, DiGangi B, Bohling M. A review of neutering cats. In: August JR, ed. Consultations in feline internal mediane. 6th ed. St. Louis, Mo: Elsevier Saunders, 2009776-790.

[Author Affiliation]

Philip A. Bushby, DVM, DACVS,

and Brenda Griffin, DVM, DACVIM

Philip A. Bushby, DVM, DACVS

Department of Clinical Sciences

College of Veterinary Medicine

Mississippi State University

Mississippi State, MS 39762

Brenda Griffin, DVM, DACVIM

Department of Small Animal

Clinical Sciences

College of Veterinary Medicine

University of Florida

Gainesville, FL 32608