By Michael Petty, DVM

Drawing on your own experience with your patients: how many of the cute wiggly puppies coming into your practice for "puppy shots" change their attitude after their spay or neuter procedures? With few exceptions, most puppies enjoy coming into our exam rooms; it is an adventure filled with new people, treats, and attention. Then we spay or neuter them and when they come back for vaccine boosters in their first year, many of them are reluctant to even walk into our clinic.

The relationship between fear and pain is an emerging area of interest in veterinary medicine. There are many well-documented human studies of how under-treated procedures (or traumatic injuries) that cause pain can impact not only the intensity of future pain events, but the emotions around them. With the founding of Fear Free (fearfreepets.com), new interest is being given to the effect these painful events have on the future well-being of the animals in our care. The emerging consensus is every pain-filled interaction we have with our patients impacts how they will handle pain both physically and emotionally.

Since I started local blocks in all neutering procedures for dogs and cats about 12 years ago, I have had a significant decline in the number of those animals coming to my clinic at one year of age, filled with fear and dreaded anticipation. Combined with Fear Free and the Cat Friendly Practice methods, most of my patients are happy to be seen by me.

This surgery article is not about how you might perform the actual neuter, but how with a few simple steps you can minimize, even prevent, the pain associated with it. This is not some complicated procedure requiring time and effort to learn; it is a procedure that takes one minute to learn and two minutes to master. In my practice, I am never the person who does the actual procedure, but one nurses perform as part of the surgical preparation.

The materials

Any local anesthetic can be used for this procedure. However, these are highly vascular regions, so consideration needs to be given to the possible injection of the local anesthetic going in the vein, an artery, or arteriole. Bupivacaine is a popular choice for local anesthesia, but given the dangers of inadvertent injection into the blood stream, it can only be used with caution.

On top of that, the preparation for these surgical procedures only takes moments, and waiting the 10 minutes for bupivacaine to come to full effect can slow the entire procedure down; causing down time and frustration for the waiting surgeon that might impact the decision to do a local block in the future.

Instead, lidocaine should be the local anesthetic of choice. In the doses we are using for these blocks, there are no concerns if the anesthetic should inadvertently be injected into the blood stream. If given early in the surgical preparation, the couple of minutes it takes to come to full effect will have passed in plenty of time for the surgeon to start the procedure.

The safe dose for lidocaine should be under 4 mg per kg. This gives a more than adequate amount for the block you need to perform. As a quick rule of thumb, I like to calculate the dose of two percent lidocaine at no more than 1 cc per 10 lbs. of the dog or cat.

Needle size is a consideration when injecting a testicle. I always use 22- or 23-gauge needles; I pick a length that will allow me to enter the caudal pole of the testicle and reach the cranial pole. For cats, this is usually a 23-gauge, 3/4-inch needle. For small dogs, it might be the same. For large dogs, I might need to resort to a 22 gauge, 1.5-inch needle.

The procedure: Orchidectomy

In either a dog or cat, the method is the same. After an alcohol prep, the testicle is firmly grasped with the non-syringe hand, and the needle is inserted into the caudal pole of the testicle and advanced just shy of the cranial pole. While maintaining a firm grasp, aspirate to make sure you are not in a blood vessel, then start to inject just until you feel the slightest pressure under your fingers.

For a cat, this will take perhaps ¼ cc of lidocaine per testicle. For a large dog, up to 1 cc of lidocaine per testicle might be needed. Withdraw the needle and repeat with the other testicle.

In dogs, you can also use the same needle to do a line block over your intended incision area.

Complications are limited to localized bleeding. This usually results in what appears to be bruising of the testicle; sometimes there is a small hematoma. Only once, after many hundreds of procedures, was there a significant hematoma under pressure, which had a comical effect (to my staff) as it exploded in my face. There were no serious concerns in any of these cases as the hematoma/bruising is contained within the testicle and is removed surgically.

The procedure: Ovariohysterectomy

For obvious reasons, the lidocaine injection during an ovariohysterectomy must be done by the surgeon. The drawback to this is it can take time for the lidocaine to take effect, which can slow down the procedure by several minutes. To overcome this time lag, once the ovary is exteriorized, an injection is made and it is dropped back into the abdomen. I then find the second ovary, inject and drop that one back into the abdomen. By the time this happens, the first ovary is blocked and ready for ligation.

Unlike the neuter, I do not inject directly into the ovary. Instead, I pass a needle through the combined ovarian and round ligaments, avoiding any obvious blood vessels, and dribble lidocaine as I withdraw the needle.

For most animals, this is sufficient to provide analgesia to the ovary. In both dogs and cats, the amount of lidocaine is minimal, 1/4 cc per ovary for cats, 1/2 to 3/4 per ovary for dogs. (See "See the procedure" box for details to view a video from the author.)

The potential for complications is slightly larger, but manageable for this procedure. The only serious one is hitting a blood vessel while passing the needle through the ligaments. Despite avoiding obvious blood vessels, it can still happen. If it does, I immediately clamp below the bleed and proceed without waiting for the lidocaine to take effect.

The other possible complication is in the hard-to-find ovaries. Without fat-shaming, you know the breeds I am talking about. After a five-minute struggle to find and then inject an ovary, I am reluctant to drop it back into the abdomen. In these cases, I simply wait two or three minutes and then proceed with clamping and cutting that side.

Conclusion

Utilizing local blocks during surgical procedures is simple to learn and do, is good for both pain control and the emotional well-being of our patients, and is cost-effective (charge a fee for it). Please take a moment for you and your staff to review the videos and add these procedures to your pain control repertoire.

Michael Petty, DVM, is a graduate of the veterinary school at Michigan State University. As the owner of Arbor Pointe Veterinary Hospital and the Animal Pain Center in Canton, Michigan, he has devoted his professional life to the care and well-being of animals, especially in the area of pain management. Dr. Petty is the past president of the International Veterinary Academy of Pain Management. A frequent speaker and consultant, he has published articles in veterinary journals and serves in an advisory capacity to several pharmaceutical companies on topics of pain management. Petty has been the investigator/veterinarian in 12 FDA pilot and pivotal studies for pain management products. He has lectured both nationally and internationally on pain management topics.