Assessment and care of the senior cat (Proceedings)

Definition

Whether you call these patients geriatric, or "mature", special considerations are required in evaluating, examining, hospitalizing, and generally caring for older felines. Veterinarians and owners must understand that OLD AGE IS NOT A DISEASE, IT IS A STAGE OF LIFE.

None of us would be very happy with our physicians if we went to their offices complaining about an ache or pain, lump or bump and were told, "You are just getting old, and there's nothing we can do about that". Like humans, older cats do develop problems associated with advancing age.1 We veterinarians must be aware of these common problems so that we can recognize and treat them specifically and enhance our feline patients health and longevity in their golden years. The objectives of a managed program of feline geriatric health care include recognizing and controlling health risk factors, detecting preclinical disease, correcting or delaying the progression of existing disorders, and improving or restoring residual function.

Aging in the body is time dependent. However, various tissues age at different rates, depending on their cell and organ type. Some types of cells (e.g., nerve tissue) have little or slow regenerative capacity. Other tissues (e.g., epithelial cells) generally have a good regenerative response. Kidneys have a great reserve capacity, as does the liver. Myocardium is much less forgiving of injury. Environmental effects including husbandry (diet, housing, medical care) also have a great impact on longevity. Feral tomcats have an average lifespan of 3 years, whereas castrated male housecats can live well into their late teens or early 20s with proper care.

Genetics may also play a role in longevity although this has not been well documented. Some highly inbred cats may be more likely to have heritable defects in organ development or function or immune system defects that may limit longevity.2

Age Comparison

Owners often ask us to compare cat years to human years. A figure that is commonly used is 7 cat years for each calendar year. However, this rule of thumb is not completely accurate. Feline development through puberty to young adulthood is accomplished over a period of about 18 to 24 months rather than 21 years as in humans. Thus, the cats first calendar year is more like 18 human years and the cat's second calendar year is more like 5-7 human years (up to an equivalent age of 21 to 23 years in humans). After that, add about 4 years for each calendar year of cat life. Thus, an 8-year-old cat is like a 46 year old person. A ten-year-old cat would be 54, a 15 year old cat 74, and a 20 year old cat, 94 cat years of age. Experts differ as to when one would consider an aging cat to be geriatric, but you can select your own cut-off based on this comparison to the equivalent age in humans.

Morbidity and Mortality

The feline patient population is getting older as advances in animal health care and nutrition as well as lifestyle changes (more indoor only cats) have enhanced longevity. A survey by AVMA in 1996 shows that patients over the age of 6 years comprise 47% of the patient population in the average veterinary practice. It is likely that this graying of our feline patient population will continue. The most common causes of death in aged cats include renal failure, cancer, and infectious disease.2 In contrast, the most frequent causes of death among old dogs are cancer, cardiac failure, and renal failure.

Common chronic diseases of aged cats include hyperthyroidism, inflammatory bowel disease, renal insufficiency, diabetes mellitus, dental/periodontal disease, degenerative joint disease, and feline immunodeficiency virus (FIV) infection. All of these recognized disease conditions provide opportunities for veterinary management that will improve the health of affected patients and improve the quality of life as well as prolonging life.

Evaluation

Each veterinarian and practice should develop a logical approach to evaluation of the geriatric cat so that abnormalities can be detected in an early, treatable stage. In addition to being consistent with the practice philosophy and appropriate health care objectives, each geriatric care program should be evaluated - from the cat owner=s perspective to be affordable, within the owner=s ability to comply with recommendations, and consistent with the owner's philosophy of the level of care they want for their pet.

Each clinician should decide if a thorough annual examination and evaluation is sufficient or if it would be best to recommend examination as frequently as every 6 months for apparently healthy mature feline patients. Some feline practitioners recommend blood pressure evaluation as part of this examination. However, obtaining accurate blood pressure measurements in cats is often problematic. I do not believe that essential hypertension (hypertension without underlying disease such as renal insufficiency or hyperthyroidism) is sufficiently common in cats to warrant this additional patient stress and owner expense. For patients with chronic problems that are already receiving medical care, reevaluation should obviously be scheduled as indicated by the specific condition and the patient=s response to management.

If you plan to include laboratory evaluation as part of the routine yearly healthy geriatric patient evaluation, the following are recommended :

     • Complete blood count

     • Serum biochemistry profile with electrolytes

     • Complete urinalysis (collected by cystocentesis because bacterial UTI, although uncommon in cats, is more likely in older patients) – UPC if evidence of CPRD is present

     • Serum total T4

Other tests should be considered for selected patients. Feline leukemia virus (FeLV) antigen and FIV antibody tests are always recommended for sick patients and should be considered for healthy animals that are outdoor or indoor/outdoor pets with possible exposure to these retroviruses. Fecal examination for parasites may be important for cats with outdoor exposure. Thoracic radiographs, and further cardiac evaluation (electrocardiography, echocardiography, blood pressure measurement) may be recommended for cats with apparent pulmonary signs, or cardiac murmurs or arrhythmia. Abdominal radiographs and ultrasound may be indicated for cats with evidence of chronic progressive renal disease (CPRD).

Management Principles

Older animals may have some age-related deterioration of the immunologic system that makes them more susceptible to infectious diseases or allows infectious diseases (e.g., FIP, FIV) that have been kept in check by the immune system to cause clinical signs. However, routine yearly revaccination policies are currently undergoing reexamination in light of concerns about vaccine-associated sarcoma development in cats. In addition, newer information about the duration of immunity actually provided by our biologic products is becoming available. At present, many progressive practitioners recognize that yearly revaccination recommendations are not based on good science and have extended revaccination intervals in adult cats. In addition, we must be selective about which vaccines are really necessary for each particular patient. Just because a vaccine is available does not mean that it should be used in every patient - regardless of age, health status, and environment.

Older animals (like older humans) tend to get less exercise as they age. This is particularly true of cats which generally have a more sedentary lifestyle than dogs have. Diminished exercise reduces muscle tone and bone and joint strength, and causes a tendency towards obesity. Degenerative joint disease is poorly recognized in cats and contributes to the "slowing down" with age and reduced enthusiasm for exercise.

Geriatric animals also have a decreased thirst response. Therefore, they are more likely to become dehydrated with illness or even during routine hospitalization or boarding. Dehydration can obviously compromise already marginally functioning body organs and compound deficiencies in renal function.

Taste sensation is reduced in older cats and this can lead to anorexia - again, often associated with illness or a change in surroundings. Feeding highly aromatic diets and warming food to body temperature before serving will improve palatability.

Cataracts are uncommon in cats but some degree of visual impairment occurs with age-associated nuclear sclerosis and retinal degeneration Hearing loss is usually gradual and may not be noticed by owners until the cat becomes completely deaf. Both visually and hearing-impaired cats can and often do function quite normally in a protected environment such as the home. However, they should not be allowed outdoors unsupervised because they would be at risk for potentially fatal encounters with such environmental hazards such as dogs and motor vehicles.

Older cats typically spend less time grooming. Also, the skin and haircoat tend to become drier with age. Owners should be advised to brush mature cats frequently, thus helping to remove debris and improve the distribution of natural oils on the skin and in the haircoat. If necessary, the cat can be bathed with mild hypoallergenic, nondrying, shampoo. Long haired cats may have more problems with hair mats as they age and the haircoat may need to be clipped to make it easier for the owner to groom the cat. Obesity and DJD also restrict mobility and ability to groom adequately.

     Musculoskeletal disease (e.g., degenerative joint disease, osteoarthritis) is not well recognized in cats compared to dogs. However, it is surprising how often degenerative joint disease is discovered as an incidental finding on feline radiographs. Sometimes, degenerative joint disease may be a cause of the cat apparently "slowing down with age". In these cases, treatment may markedly improve the cat's mobility and general well being.

Ostochondritis dessicans occurs in cats but is often not recognized in the early stages when surgical intervention is helpful. Fragmented coronoid process is another disorder often overlooked until severe DJD is present. Hip dysplasia is very common in cats and will often be a significant cause of pain and decreased mobility with age. The stifles may be affected in cats with hip dysplasia and medial patellar luxation is a common associated finding in these cats. Cruciate ligament tears most often involve avulsion of a small fragment of bone from the distal tibial plateau attachment of the ligament rather than via a central tear as in dogs. This avulsion may be seen as a small joint mouse on radiographs. Early recognition and joint stabilization can prevent severe DJD if either of these stifle problems are recognized early in the course. Tarsal DJD occurs rarely and may cause fusion and reduced range of motion in the joint. Lumbosacral instability and compression may be a reason for hypersensitivity and pain in the LS and dorsal pelvic region of cats. Because pain is elicited when the cat postures to eliminate, litter box aversion and ectopic elimination behaviors may be a manifestation of this problem. True vertebral disc protrusion is uncommon in cats but will cause signs similar to dogs.

Environmental approaches to improving comfort in cats include providing ramps to allow easier access to higher locations such as beds, cat trees, and windowsills. Food and water bowls should be placed on the floor or some other more readily accessible location. Litterboxes with low sides will make it easier for the cat to enter and leave the box. Providing a source of heat that the cat can move on and off voluntarily will often be attractive to cats with DJD and will provide a source of comfort particularly in cold weather.

Unfortunately, we do not have many choices for pain and inflammation control for osteoarthitis in cats because they are intolerant of many NSAIDs. Agents that have been recommended include Adequan [Equine formulation] (0.15 ml/10 lb BW IM once weekly x 4-6 weeks, then q2-3 weeks), Cosequin, and other nutraceuticals. The NSAID, meloxicam (Metacam®), is not approved for oral use in the cat in the US at this time, however, it has been used safely and successfully in cats in other countries for several years. The dose for cats is 0.1 mg/kg PO q24h for 1-2 days loading dose then 0.1 mg TOTAL dose q24-72h. Try to reduce the frequency of administration to the minimum needed to keep the cat comfortable. Side effects of NSAIDs include vomiting, anorexia, and GI ulceration and owners should be warned to stop medication immediately and contact you if any of these signs occur.

Buprenorphine (0.01-0.03 mg/kg q6-12h sublingual), tramadol (12.5 mg (¼ of 50 mg) PO q12h), and amantidine ( 3 mg/kg PO q24h), can be used in cats that do not tolerate NSAIDs or as an adjunct to NSAIDs. Gabapentin (3 mg/kg PO q12-24h) may be most helpful for cats with LS instability and neurologic pain.

Oral cavity disorders (including periodontitis, gingivitis, stomatitis, dental disease, oral ulcers, or oral cavity tumors) are often overlooked as the cause of significant morbidity in geriatric cats. It is remarkable how often appropriate treatment for these oral problems leads to a marked improvement in quality of life and activity. The common signs of oral cavity disease include inappetence, weight loss, halitosis, chattering teeth, abnormal chewing and/or swallowing behavior, decreased grooming, or nasal discharge (usually unilateral). Infection often accompanies oral cavity disease and may result in intermittent bacteremia or septicemia. This may in turn lead to disorders in other body systems (including hyperglobulinemia due to immune stimulation, immune-complex renal disease, chronic interstitial nephritis, hepatitis, and possibly cardiovascular disease).

Apparent senility does occur in cats. In some of these aged individuals, behavior changes include confusion, aimless wandering around the house, or getting trapped in a corner or under a piece of furniture - the cat is apparently unable to remember how to get out. In others, the changes may include aggression or changes in elimination behavior (usually breaks in housetraining). It is very important to perform a thorough physical examination and laboratory workup to eliminate possible medical problems (e.g., hyperthyroidism, primary central nervous system disease/neoplasia, hepatoencephalopathy, or urinary tract infection) before assuming that these changes are due to senile dementia. For true cognitive dysfunction, deprenyl can be used at 2.5 mg PO q24h.

Impaired thermoregulation is another central nervous system change that may occur in older cats. These animals may be more heat or cold seeking depending on the season and ambient temperature. Body temperature must be monitored closely during and following anesthetic procedures and if the animal is hospitalized.

Geriatric Diets

There are differences of opinion as to whether a specific, specialized diet is necessary or recommended for geriatric cats.20 Clearly, animals with specific medical problems that may be helped by special diets (e.g., renal disease [restricted protein and phosphorus], inflammatory bowel disease [select protein, limited antigen], diabetes mellitus [high protein?, high fiber]) should be fed the most appropriate diet for their condition.21,22 Acidifying diets are not recommended unless there is a documented medical reason for their use. But what about the apparently healthy geriatric patient?

The best diets for older feline patients should be well-balanced, nutritionally complete, highly palatable, highly digestible, and replete with potassium and taurine. Excesses of mineral and protein should be avoided. Several commercially available products fulfill these criteria. Supplements should not be necessary with these products unless specific deficiencies (e.g., hypokalemia) are detected.

Some clinicians routinely recommend feeding older cats restricted-protein diets (i.e., those designed for animals with renal insufficiency) in the belief that these diets will prevent or slow the development of renal failure. However, recent studies suggest that lower protein diets are not renal protective and are not necessarily beneficial unless or until renal insufficiency has developed.

Older cats do tend to eat more meals but smaller meals than younger cats. Therefore, leaving food available all day may help these cats maintain to good body weight. Some cats are social eaters and will eat more if the owner is present and if he/she is giving the cat attention at meal time. Older cats may not like to put their face into a small bowl to eat so they may eat more enthusiastically if food is placed on a flat dish or saucer. Be sure that competition from younger, more active housemates is not interfering with the older cat's ability to find food and eat without disturbance.

Drug Therapy

In addition to the normal species-related vagaries in drug handling, age related changes affect the absorption, distribution, and metabolism of various drugs in older cats. Decreased gastric secretion of hydrochloric acid may affect the absorption of some drugs that require an acid environment. Decreased intestinal blood flow may reduce the amount of drug absorbed from the intestinal tract. Faster gastric emptying (decreased gastric emptying time) can reduce the amount of contact time for some drugs absorbed from the stomach.

Changes in body mass affect drug distribution. As an animal ages, the percentage of body fat tends to increase and lean body mass decrease. Consequently, dose adjustments may be required if a drug dose is based on lean body mass. Changes in serum proteins and protein binding may affect drug availability and elimination kinetics.

Decreased cardiac output increases circulation time, may reduce blood flow to certain organs or tissues, and further alter drug metabolism or pharmacokinetics. Reductions in liver mass and function can reduce the rate of metabolic conversion of a drug to either active or inactive metabolites. Alterations in renal blood flow and glomerular filtration rate can reduce the rate of clearance of unmodified drug or metabolites from the body. The hepatic and renal changes result generally in a decrease in first-pass drug metabolism and tend to result in higher drug levels in the body. Finally, because older patients are likely to have more than one problem as they age, veterinarians need to be aware of the effects of polypharmacy and the potential for adverse drug interactions.

Common Diseases of Older Cats:

Hyperthyroidism, Chronic progressive renal disease, Hypertension, Oral cavity disease, Neoplasia, Inflammatory bowel disease, Diabetes mellitus.

Euthanasia

Despite the veterinarian's best efforts, there often comes a time when the clinician must help the owner make the difficult decision to end the patient's life. This is a heavy responsibility and none of us should take it lightly. In addition to gently alleviating the suffering of the patient, we must be sensitive to the bond between the pet and its owner. If possible, euthanasia should be performed after regular business hours when the clinic is quiet and time is available to perform the procedure calmly, compassionately, and gently. Our ability to communicate with the owner and help them through this difficult time is very important.

AAFP Geriatric Practice Recommendations

The American Association of Feline Practitioners (AAFP) has an updated major panel review documenting recommendations and suggestions for practitioners interested in improving the health maintenance and management of older feline patients. Most of this information is contained in the document above but is expanded in the AAFP document. Copies of this document are available online at: http://www.aafponline.org

References available upon requestion