This was not always the case. In the 40s, 50s and 60s — well over half a century ago — death from anesthesia was about 1 in 400 for dogs and 1 in 260 for cats. These numbers are from referral hospitals, which are generally anesthetizing sicker patients, and that could increase the numbers over what you would expect to see in healthier pets in a general practice. There is a study from the early 2000s in the U.K. that followed mortality in a variety of practices (from general practices all the way to referral hospitals) and included dogs, cats, birds and pocket pets; in it, they found a death rate from 1 in 588 for dogs and 1 in 416 for cats. The risk has continued to drop, so that today those fatality numbers are around 1.7 in 1,000 dogs and 2.4 in 1,000 cats.

Although only statistics for dogs and cats have been created, the same improvement in risk applies to other pets such as rabbits, rats, hedgehogs, bearded dragons, and even goldfish as equipment and teaching new methods of anesthesia have improved over the years.

How does it work?

General anesthesia is given through an IV or an inhaled gas, or sometimes a combination of the two. It is similar, on a smaller scale, to a medically-induced coma. Oftentimes a sedative is given first.

It works by interrupting nerve signals in your pet’s brain and body. It keeps them temporarily unconscious: asleep, relaxed, and pain free during a procedure or surgery. It slows down automatic functions like breathing, heart rate, and circulation. During that coma-like period, brains cannot process pain, nor will the pet remember what happened during surgery.

During the procedure, the veterinarian or veterinary anesthesiologist will check some basic functions while your pet is under, such as breathing, temperature, heart rate, blood pressure, blood oxygen level, and fluid levels (as would happen in a human surgery). Monitoring doesn’t have to be done with expensive equipment, as having a trained person monitoring the depth of anesthesia as well as certain physical parameters can be just as valuable. Computerized anesthesia monitors can be used to enhance, but not replace, that person’s ability.

If those functions aren’t where the veterinarian wants them to be, adjustments in the level of anesthesia can correct them.

Monitoring doesn’t stop when surgery is over, or even when the equipment is removed. About half of the anesthesia deaths in small animals happen during the first 3 hours after surgery. The causes are usually breathing or heart problems. That makes this time critical for patient safety. Careful monitoring by a trained observer of physical variables, especially oxygenation and temperature, can help make this time period safer.

What main factors influence anesthetic risk?

Not unsurprisingly, the first is the health of the animal. Healthy patients, or patients with mild, controlled disease, are at less risk than patients who are sick. For healthy dogs, about 1 in 2,000 are expected to have a fatality and about 1 in 1000 cats would have one. In sicker patients, it would be closer to 13 dogs and 14 cats out of 1,000.

Having anesthesia in an emergency can also increase risk. That makes sense if you think about it. When you have time to plan a procedure, stabilize your patient and can schedule surgery at a time that is optimal for everyone, things go better. Having said that, the risk of anesthetic death with an emergency procedure, while higher than regular procedures, is still low.  Emergencies are emergencies because they can’t wait, and there are times that the pet will die if surgery is not done as soon as possible, such as with bloat.  

Veterinarians can decrease risk by focusing on monitoring and supportive care before, during, and after anesthesia. Preoperative planning is done with a good history, physical examination, and often baseline lab work to check liver and kidney function, among other things. Any abnormalities identified before surgery can be corrected if needed.

Follow all of your veterinarian’s pre-operative instructions exactly, including when to stop giving food the night before. Anesthetized patients lose their ability to swallow. If there is food in the stomach, the pet could vomit while under anesthesia or soon afterwards. If vomiting occurs before the swallowing reflex comes back, the vomited material can enter into the lungs, causing aspiration pneumonia. For emergency surgery, this factor is overlooked, but not for elective surgery.

While anesthetic risk is not zero and never will be, the risks are low and shouldn’t prevent any pet owner from providing health care for their pet whether it’s a dental cleaning or major surgery.

The Corneal Erosion

There are several causes of acutely red and painful eyes and one of the most common causes is a wound or scrape to the surface of the eye. The clear surface of the eye is called the cornea; because it is the outermost layer of the eye, it is prone to scrapes and tears. Common causes of corneal erosions include:

• Rough contact with plants, thorns, or bushes
• Scratches from another animal (note: the cat scratch wound can be especially serious as the wound quickly heals over, sealing infection within the eye.)
• Self-trauma (rubbing or scratching at a painful ear or even at the eye due to some other eye problem can lead to an inadvertent scratch to the eye.)
• Chemical irritation (such as getting shampoo in the eye during a bath.)
• Foreign body injury (plant material can get stuck under an eyelid and can scrape the cornea.)

A special fluorescent stain is used to confirm if there is an ulcer or erosion. Normally, water will run smoothly off the surface of the cornea, like rain washing off a windshield. If the cornea is damaged, the stain will stick to the damaged area and look bright green under a fluorescent lamp.

Treatment

Antibiotics

A routine corneal ulcer or erosion should heal easily. Since the damaged cornea is at risk of becoming infected (or may even already be infected, as demonstrated by a purulent discharge), a topical antibiotic is needed and ideally should be used four times a day or more. Since it is a rare pet owner that can accommodate any medication administration four times a day, we usually have to make do with three times a day but to properly sterilize the eye surface, the antibiotic should be used four times a day. Either drops or ointment can be used depending on the owner’s preference.

Pain Relief

The second part of treatment is pain relief: Atropine 1% drops or ointment. The atropine acts by temporarily paralyzing the pupil’s ability to constrict (the main source of pain is spasm in the pupil). Pupillary dilation is expected when this medication is used and the pet may be reluctant to experience bright sunlight while under the influence of this medication. Because the tear duct system is connected to the nose and mouth, the patient will also taste the above medications and atropine is famous for its bitter taste. Dogs do not seem to mind this unduly but cats will drool shortly after the medication is given in an effort to get the taste out of their mouths. This is a normal reaction to the Atropine as is the dilated pupil.

Some other procedures, and possibly a visit to a veterinary ophthalmologist, may be necessary. 

 If the inflammation associated with the ulcer goes deeper into the eye, the situation becomes more serious; it is very important not to skip that one-week re-check. If there is any question about the eye’s healing progress, the eye should be re-checked sooner.

It is important that the owner observe the progression of healing at home. If the eye is doing well but suddenly becomes more painful, if a discharge develops, or if the eye simply does not look right, have your vet recheck the pet sooner than the planned one-week appointment.

Some Special Ulcer Conditions

Indolent Ulcer

Some ulcers form with a small lip on their edge.  Since the ulcer is trying to heal from the bottom up, the lip interferes and creates an ulcer that seems to never get any smaller. Several techniques can be used to remedy this situation: the lip can be rubbed away, hyaluronan or PSGAG eye drops can be used to strengthen the cornea, or surgery can be performed. A technique that has gained popularity over recent years is called the grid keratectomy where a needle is used to scratch a grid of lines on the cornea. The cornea is then able to heal in, grid by grid. Poodles and boxers are notorious for these ulcers but they can occur in any breed. 

Melting Ulcers

When infection is present, the cornea will develop a yellow or tan gooey appearance because the bacteria or fungi causing the infection elaborate enzymes that actually dissolve corneal collagen fibers. The cornea softens and appears to be melting and can actually perforate. Culture and cell sampling for analysis are very helpful in determining the right antimicrobial therapy. In addition to antibiotic drops, the eye will need some sort of medication to inactivate the aforementioned collagen-dissolving enzymes. Often, this involves taking a blood sample from the patient and actually delivering the patient’s own serum as an eye drop.

Descemetocele

(Pronounced des’ĕ-met’ō-sēl) Descemet’s membrane is the thin attachment of the cornea to the fluid of the eye below. A Descemetocoele is an ulcer that has penetrated through the cornea completely except for the last thin membrane. An eye with a descemetocoele is at high risk for rupture and measures must be taken to protect the eye. Usually, surgery is needed. The brachycephalic breeds (Pekingese, pug, etc.) are predisposed to this problem due to their prominent eyes.

Again, corneal ulcers and erosions usually heal routinely but stay alert for any changes that could indicate a more serious turn of events. Be sure self-trauma (rubbing the eye) is prevented and be sure to go to a recheck at the proper time. If anything seems not to be proceeding properly, be sure to contact your veterinarian.