Author

Stephen J. Birchard DVM, MS, Diplomate ACVS

Tuesday, August 19, 2014

Buprenorphine in Cats: Is it an effective postoperative analgesic?

Evaluation of the perioperative
analgesic efficacy of buprenorphine,
compared with butorphanol, in cats
Leon N. Warne, DVM; Thierry Beths, DMV, PhD; Merete Holm, DVM;
Jennifer E. Carter, DVM; S├ębastien H. Bauquier, DMV

J Am Vet Med Assoc 2014;245:195–202

Summary

In this study the authors compared the analgesic efficacy of buprenorphine vs. butorphanol for cats undergoing ovariohysterectomy.  Cats were divided into 2 groups: one group was premedicated with buprenorphine in combination with medetomidine, and the other group premedicated with butorphanol and medetomidine prior to general anesthesia. A “validated multidimensional composite pain scale” was used to evaluate pain in all cats, and rescue analgesia (methadone and meloxicam) was administered if the score went above a predetermined level (>9 of 28 indicating moderate to severe pain).
The authors hypothesized that buprenorphine would provide superior postoperative analgesia to cats undergoing ovariohysterectomy.

In phase 1 of the study only a premedication dose of the buprenorphine or butorphanol was given. This phase of the study had to be stopped after 10 cats since 9 of them required rescue analgesia immediately postoperatively.

In phase 2 of the study the experimental methods were the same as phase 1 except a second dose of buprenorphine or butorphanol was given during incision closure. In this phase of the study all cats receiving butophanol required rescue analgesia, whereas none of the cats receiving buprenorphine required rescue analgesia.

Commentary

Two key points can be taken from this study:

  • Buprenorphine was clearly more efficacious than butorphanol in providing postoperative analgesia.
  • After premedicating with buprenorphine, a second dose was required prior to anesthetic recovery (during incision closure) to provide sufficient analgesia.
This is a very practical and well-designed study that has important clinical implications. Buprenorphine appears to be an effective postoperative analgesic for cats and should be considered as a useful element of the veterinary surgeon’s postoperative care in cats. Butorphanol was not an effective analgesic in the study and although possibly useful in other clinical situations, cannot be recommended for cats undergoing ovariohysterectomy or other surgeries with similar pain levels.


What is your experience with buprenorphine in cats as an analgesic?

Saturday, August 16, 2014

Scrotal Hematoma in Dogs After Castration: Why does it happen and how to prevent it.

Scrotal hematoma, the accumulation of blood in the scrotal sac, is a common postoperative complication of castration in dogs. (Fig. 1) 
Fig. 1: Scrotal hematoma that developed after castration in this golden retriever
Postoperative bleeding from one or both testicular arteries or veins is the most likely cause. Bleeding from these vessels can also accumulate in the abdominal cavity and be unrecognized until the dog becomes hypovolemic and develops shock. Bleeding from subcutaneous tissues could also result in a scrotal hematoma but is less likely, particularly in cases where bleeding is severe and the scrotal hematoma is large.

Etiology
Insecure ligatures are probably the cause of bleeding from testicular vessels. Ligature failure during castration may be due to a number of technical problems, such as loose ligature, improper suture material, or ligature slippage. Improper location of the suture ligature can also predispose to failure. If the spermatic cord is not adequately exteriorized the ligatures will be placed too close to the testicle. (Fig. 2) 
Fig. 2: The red dotted line indicates ligation of the spermatic cord too close to the testicle (T)
The ligatures in the figure are placed in the proper location.
(Modified from: Boothe, HW. Surgery of the testicles and scrotum. Saunders Manual of Small Animal Practice, Birchard and Sherding editors,  Figure 87-1, Elesevier, 2006, pg. 970.)
This causes excessive tissue to be incorporated in the ligatures. Insufficient stripping of the adipose tissue from the cord also predisposes the ligature to slippage.

Treatment
Scrotal hematomas can be managed medically with compresses (ice packs for the first 24 hours postoperatively, followed by warm compresses), Elizabethan collar, restricted exercise, analgesics such as NSAIDS, and antibiotics. In severe cases or those not responding to medical therapy, scrotal ablation is necessary to remove the entire scrotum and its contents.

Prevention
To prevent scrotal hematoma when performing castration, adhere to the following technical principles:
- After incising over the testicle and exposing it, break down the gubernaculum testis and place traction on the testicle to allow several centimeters of the spermatic cord to be exposed. (Fig. 3)
Fig. 3: Proper exposure and clamping of the spermatic cord during routine canine castration.
- Carefully and thoroughly strip the adipose tissue from the spermatic cord with a moistened surgical sponge.
- Triple clamp the cord with Carmalt clamps, cut between the 2 clamps closest to the testicle and perform routine ligatures with Monocryl or PDS suture (transfixing and full ligatures). The full ligature is placed in the crush area of the most proximal clamp after it is removed, the transfixing ligature is placed just distal to the full ligature. (Fig. 4)
Fig. 4: Proper ligature technique in a closed canine castration. (T=testicle)
(Modified from: Boothe, HW. Surgery of the testicles and scrotum. Saunders Manual of Small Animal Practice, Birchard and Sherding editors, Elesevier, 2006, Figure 87-1, pg. 970.)
- Check the vascular stump for bleeding prior to replacing it into the incision. Repeat the same procedure on the opposite side.  

I prefer closed castration, even on large dogs, because it allows excision of the testicular tunics along with the testicle. (Fig. 5)
Fig. 5: Closed castration allows removal of the parietal vaginal tunic with the testicle
Close the subcutaneous tissue routinely (3-0 or 4-0 absorbable suture in a simple continuous pattern). Although skin sutures can be used on the skin incision, I prefer do an intradermal closure in lieu of skin sutures. Fewer complications occur with an intradermal closure of castration incisions. In an unpublished study performed at Ohio State several years ago, dogs with intradermal skin closure had fewer incisional problems and even fewer scrotal hematomas postoperatively. Less self-trauma to the incision and scrotum were thought to be the reason for this finding.

What are your experiences and opinions regarding castration technique and complications in dogs? Do you have any tips or suggestions? Post questions and comments either on the blog or on facebook (Dr. Stephen Birchard, Veterinary Continuing Education) 

Thank you!