Pearls of Wisdom

Pearls of Wisdom #1

Keratoconjunctivitis Sicca (KCS)

“Dry Eye Syndrome”

Keratoconjunctivitis sicca (KCS) technically means a dry, inflamed cornea and conjunctiva. It is a medical condition, however, that progresses to severe corneal opacities, ulcerations and eventual blindness involving one or both eyes. It occurs when there is a deficiency in the water portion of the tear film that normally accounts for about 95% of the tear volume.

Common signs:

• Tacky, mucoid discharge that clings to the eyelid and surface of the eye; lids may even seem adhered
• Conjunctiva become red, thickened and possibly pigmented
• Surface of the eye loses its luster
• Excessive blinking or squinting along with rubbing or pawing at the eye noted by owner
• Associated dysautonomia: dilated non-responsive pupils, protrusion of the 3 rd eyelid (cherry eye)
• Associated systemic autonomic dysfunction: urinary and fecal incontinences, bradycardia, hypotension, dysphagia, and dry nose (xeromycteria)
• Concurrence of dermatological disorders, specifically atopy and seborrhea

KCS, especially in the early stages, is typically misdiagnosed as bacterial conjunctivitis. Topical antibiotic therapy will help during this period but signs return within 2-3 days after treatment is stopped.

Etiologies of KCS:

• Congenital hypoplasia or a retarded functional development of the tear producing glands (Yorkshire Terriers)
• Autoimmune adenitis. The structure of the gland breaks down due to immune mediated inflammation (Cocker Spaniels, Miniature Schnauzers and West Highland White Terriers)
• Trauma to Cranial Nerves V or VII or damage in the area of the tympanic bullae, especially in horses
• Distemper virus
• Secondary to chronic conjunctivitis
• Herpes respiratory virus (cats)
• Anesthesia (up to 2 days post)
• Administration of the following drugs: potentiated sulfonamides, sulfa drugs, phenazopyridine, etodolac, long term use of atropine, and other drugs
• Accidental removal of the gland during “Cherry Eye” surgery

Diagnosis:

Late stage KCS is generally fairly easy to diagnose by using clinical signs. The only available test to confirm KCS is the Schirmer Tear Test (STT). A test strip is placed in the outer corner of lower eyelid for 60 seconds and the area of moisture wetting the strip is measured in millimeters.

Normal: 15 mm or greater

Borderline: 11-14 mm.

Dry: 10 mm

Severely dry: < 5 mm

Treatment:

Cyclosporine 0.2% topical solution (CsA) is currently the primary treatment. The drug allows tear production to be restored by suppressing immune destruction. Dogs with a STT as low as 2 mm have shown an 80% response rate to this drug. The drug has a convenient dosing schedule of once or twice a day. The eyes are re-evaluated in 3 weeks and the dosing regimen changed as needed.

Tacrolimus 0.5% topical solution is also an immunosuppressant with similar therapeutic effects of CsA.

Artificial Tears are often combined with other therapies as a soothing measure.

Antibiotics are often necessary with initial treatment due to secondary infections.

Mucomyst® Eye Drops (acetylcysteine) are used to help remove the thick mucoid discharge. They are often used in combination with pilocarpine, artificial tears and an antibiotic. The mixture is commonly referred to as “Severin's Solution” and originated from an article published in 1996 by Dr. Severin, a veterinary ophthalmologist at Colorado State University .

Parotid Duct Transposition is the only true cure for KCS. The surgical procedure, typically performed only by board certified veterinary ophthalmologists, uses the parotid salivary gland duct to provide a continuous source of moisture to the eye. The parotid duct is the salivary gland found in either side of the facial cheek. It produces saliva which is carried to the mouth by a long duct. The duct is carefully dissected and moved to the eye to deliver moisture in the form of saliva over the eye. If performed correctly there are few complications. A few dogs that are rapid, greedy eaters may actually spurt saliva out of the eye while eating!

Pearls of Wisdom #2

Kaopectate™ and cats

Just a reminder that Kaopectate™was reformulated in 2004 to contain bismuth subsalicylate. This is bad news for cats as they don't metabolize aspirin or aspirin equivalents well at all.

One tablespoonful of the reformulated childrens and regular Kaopectate™ contains 130 mg aspirin equivalent.

One tablespoonful of the reformulated extra strength Kaopectate™ contains 230 mg aspirin equivalent.

At the most, cats should receive 10 mg/kg aspirin every other day or 20-25 mg/kg aspirin once. Based on this, it is easy to see how cats can develop aspirin toxicity from the newer, reformulated Kaopectate™.

Pearls of Wisdom #3

Gastric Dilatation/Volvulus points to remember:

1. Can occur in rare incidences in small dogs, cats and even small pocket pets such as guinea pigs.
2. Dilatation can occur multiple times even after tacking (gastropexy) of the stomach .
3. Plasma Lactate concentrations have been closely associated with patient outcome. After decompression, sequential readings every 15 minutes along with fluid resuscitation are the current practice standard in determining prognosis. A lactate concentration above 6.0 mmol/L, with no decline during fluid resuscitation is a good indicator of gastric necrosis and severe systemic hypoperfusion and gives a grave prognosis.
4. Early decompression of the stomach is vital for treatment.
5. Oxyglobin administration provides an excellent source of colloid therapy in hypovolemic shock as well as increased tissue perfusion once decompression and torsion has been relieved.
6. Many complications can arise within the postoperative period based on the severity and length of the GDV. Some common problems are: cardiac arrhythmias, continued shock, gastroparesis, excessive vomiting, hypokalemia and gastric distention. Less common risks are pancreatitis, disseminated intravascular coagulopathy or DIC, incisional dehiscence, peritonitis, gastric ulcers, ischemia and necrosis.

Information for Clients

•  Avoid feeding one large meal per day. Several small meals prevent gastric overload.

•  Limit exercise immediately after feeding

•  Feed high-quality protein, low-fat diets.

•  Average hospital stay for GDV surgical candidate is 3-7 days

•  Mortality rate is between 15-18%

•  Surgical correction and gastropexy are NOT a guarantee against rare future episodes of dilatation or even torsion.

 

Pearls of Wisdom #4

Changes in serum chemistry profiles are expected when corticosteroids are used in dogs. Alkaline phosphatase (ALP) is the enzyme most veterinarians associate with corticosteroid use in dogs. Alkaline phosphatase increases, often greater than 5000 U/L, are due to cellular membrane secretion and induced synthesis.  It is important to remember that other enzymes increase in activity as well. Alanine transaminase (ALT), aspartate transaminase (AST) and gamma-glutamyl transferase (GGT) activities also rise after corticosteroid use. In general, ALP shows the highest increase, followed by GGT, ALT and AST. Remember that cats rarely show any rise in liver enzyme activity after corticosteroid use.

Pearls of Wisdom #5

Phytonadione or Vitamin K1 is the drug of choice for treatment of anticoagulant rodenticide toxicity. The reported oral dosage range in dogs and cats is from 2 to 5 mg/day. To obtain the maximum effect, the total daily dose should be divided and given 2 or 3 times a day. The duration of therapy depends on many things, in particular the specific rodenticide and amount ingested. Treatment of long acting anticoagulant ingestion may need to be continued for weeks to months. The prothrombin time (PT) may be used to guide the need for continued therapy, but the animal needs to be off phytonadione for 48 hours before the PT is performed.

Pearls of Wisdom #6

The use of anesthetic agents in sighthounds should be undertaken with the utmost care! Thiobarbiturates and sighthounds don't mix well at all. There are now over a dozen “breeds” of sighthounds that need special attention when undergoing anesthesia. Continue reading below for more information.

Some of the oldest breeds of dogs known in history are sighthounds, with the earliest European recorded description of what is thought to be a Saluki, dating back to the 2 nd century AD. This ancient group of dog breeds has been selectively bred for hunting high speed quarry, primarily by speed and sight alone.

Included in the Sighthound group are the following breeds: Greyhound, Italian Greyhound (not a true sighthound), Whippet, Deerhound, Irish Wolfhound, Pharaoh Hound, Afghan Hound, Saluki, Borzoi, Ibizan Hound, Basenji, and Rhodesian Ridgeback. Some additional sighthounds not recognized by the AKC are the American Staghound, Sloughi, and Azawakh. While not a complete list, the majority of breeds are represented here.

Many unique factors associated with this group of dogs render them more vulnerable to adverse events associated with anesthesia. Some of their idiosyncrasies are thought to be related to the following factors:

1.) Lean body conformation, which predisposes them to hypothermia.

2.) Nervous demeanors which can lead to stress-induced clinical complications.

3.) Hematological differences; sighthounds generally have a higher packed cell volume and lower serum protein.

4.) Impaired biotransformation of drugs by the liver resulting in prolonged recovery from certain intravenous anesthetics, especially thiopental; and increased risk of drug interactions.

Safe anesthetic management of sighthounds should include sedative premedication and appropriate use of analgesic drugs to minimize perioperative stress. All thiobarbiturates should be avoided! Propofol or ketamine/diazepam is recommended for intravenous induction. Co administration of agents that inhibit drug biotransformation, such as chloramphenicol and others, should be avoided. Isoflurane is the preferred anesthetic for maintenance. Utilize measures to maintain normal body temperature and monitor closely throughout the anesthetic procedure and throughout the recovery period.

Refer to the following reference for a complete review. Court MH. Anesthesia in the sighthound. Clin Tech Small Anim Pract 1999; 14(1):38-42.