7 Nov 2023
Mike Davies
Job Title
Image © yobab / Adobe Stock
Following a series of pivotal publications in this field – and the development of medicines and therapeutic diets specifically aimed at elderly pets – many practices introduced geriatric screening programmes, especially as studies clearly demonstrated the clinical and economic benefits of doing this (Davies, 2012). However, this activity is in serious decline, and I do not know any UK practices currently running successful programmes.
Nevertheless, a significant number of our patients are in the last quartile of their expected lifespan and require special considerations and screening. Every elderly patient is unique because of variable accumulated organ system damage, natural ageing changes, and the presence of clinical and subclinical disease.
Dogs older than nine years of age typically have seven major organ system problems (Davies, 2014), with concurrent conditions being common. Conditions regularly seen in geriatric dogs are in Table 1.
| Table 1. Conditions regularly seen in geriatric dogs | ||
|---|---|---|
| Condition | Prevention/treatment | Comments |
| Dental disease | Dental prophylaxis through brushing teeth, diet, dental supplements, surgical: descaling | Only recommend products approved by the Veterinary Oral Health Council (2023) |
| Obesity | Avoid excessive calorie intake. Set weight and body condition score (BCS) limits. Aim for a BCS of 4.6/9. Therapeutic diets to obtain weight loss. Maintain exercise | Obesity has many negative effects on body systems, is associated with serious disease and significantly shortens life expectancy |
| OA | Anti-inflammatories, analgesics, monoclonal antibodies, therapeutic diets, nutritional supplements, maintain regular exercise, physiotherapy, laser treatment | Only use products with proven safety and efficacy studies for long-term use in dogs. Follow data sheet recommendations. Try to avoid polytherapy. Most nutritional supplements have little or no evidence to support their use. |
| Chronic kidney disease | Therapeutic diets, antihypertensive medications if required | Only use products with proven safety and efficacy. Follow the International Renal Interest Society Guidelines available at http://iris-kidney.com |
| Neoplasia | Surgical interventions (excision, debulking), chemotherapy, immunotherapy, radiotherapy, hormone therapy, dietary management | Conduct a full geriatric screen and choose interventions to minimise risk to the patient |
| Liver disease | Low fat, control copper and iron intake, therapeutic diet, nutritional supplements (for example, SAMe, milk thistle) | Only use products with clinical studies to demonstrate efficacy and safety |
| Acute pancreatitis | Analgesics, therapeutic diets (low fat, highly digestible), pancreatic enzyme supplements if necessary | Only use products with clinical studies to demonstrate efficacy and safety |
| Prostatic disease | Benign hyperplasia – castration, finasteride, osaterone or deslorelin; MRI-guided ablation. Prostate cancer, surgery (poor results), cyclooxygenase inhibitors piroxicam or carprofen |
Guarded results with all treatment modalities |
| Endocrine disorders | ||
| Diabetes mellitus | Insulin and bodyweight control, therapeutic diets | Ensure diet remains fixed formula to avoid fluctuations in insulin requirement. Time insulin administration to same time as feeding or after food consumed Follow American Animal Hospital Association Guidelines (updated 2022) available at www.aaha.org/aaha-guidelines/diabetes-management/diabetes-management-home |
| Hyperadrenocorticism (Cushing’s syndrome) | Surgery, medications to suppress cortisol production (mitotane or trilostane) | Need to titrate drug dose accurately to the individual. Excess dose can cause Addison’s (hypodrenocorticism) |
| Hypothyroidism | Thyroid hormone (levothyroxine) | Titrate dose to post-administration T4 levels in blood |
| Cognitive dysfunction | Therapeutic diets, nutritional supplements, anxiolytic drugs | Only use products with clinical studies to demonstrate efficacy and safety |
The American Aging Association defines Geroscience as the study of the biology of ageing, the pathophysiology of age-related diseases and research on biomedical applications that impact ageing and/or the pathogenesis of diseases associated with old age.
In May of this year, the Purina Institute in Lausanne hosted a two-day meeting on advances in comparative geroscience, which focused attention on some of the most recent developments, including the following.
A gradual decline of the immune system due to natural ageing changes. For example, circulating T-cell (lymphocyte) levels in circulation, including gamma-delta T lymphocytes, decline in older dogs associated with involution of the thymus (Marchetti, 2020). In addition, an age-associated disturbance in the diversity of the T-cell receptor repertoire occurs in dogs (Holder, 2018). These changes impair immune response to novel antigenic challenges, including infection and vaccination. The important role of immunosenescence in dogs has been summarised by the late Michael Day (Day, 2010).
A chronic, sterile, low-grade inflammation that develops with advanced age in the absence of infection, and contributes to clinical manifestations of other age-related pathologies (Dugan et al, 2023; Fulop et al, 2021). Upregulation of the inflammatory response increases oxidative damage, which impacts many organ systems.
Few studies on inflammaging in dogs exist. One recent report (Jiménez, 2023) did not find any significant changes in concentrations of IL-6, IL-1β, and TNF-α between adult and elderly dogs. In another study (Alexander, 2018) involving 80 Labrador retrievers, serum levels of immunoglobulin M (p less than .001) and 8-hydroxy-2-deoxyguanosine (p less than .001) increased with age, but no effect existed on immunoglobulin G or C-reactive protein.
The role of Inflammaging in dogs has been summarised (Day, 2010).
An association between chronological age and higher reactive oxygen species production rate by mitochondria in brain cells occurs in dogs (Head et al, 2009). In another study looking at the genome of 4,169 canids representing 110 breeds (Nicholatos et al, 2019), mitochondrial bioenergetics were found to play a role in lifespan variation between breeds. It is not surprising, therefore, that mitochondrial dysfunction has been linked to age-related diseases including neurodegenerative and cardiovascular disease, as well as longevity (Amorim et al, 2022).
In a recent paper (Franco-Martínez et al, 2023), statistically significant higher ferritin levels mean corpuscular volume, mean cell haemoglobin concentration, total proteins, globulins, haptoglobin, total ferric fixation capacity, alkaline phosphatase, butyrylcholinesterase, triglycerides and calcium were observed in overweight/obese dogs – some of which indicate tissue hypoxia with serious implications for all body systems.
In another recent paper (Pan et al, 2023), the mean age of 30 dogs that were overweight/with obesity was 9.12 (standard deviation; ± 0.48 y [control group] and 9.73 ± 0.63 y [treated group].
Dogs fed a therapeutic weight loss diet lost more body fat (13.2%) than the control group and the diet prevented loss of lean body mass, and resulted in significantly lower fasting serum cholesterol, triglycerides, insulin, leptin, mean postprandial interstitial glucose and pro-inflammatory cytokines.
A multitude of clinical conditions occur in geriatric dogs – many of which, including endocardiosis OA and chronic kidney disease, start earlier in life.
In a lifetime study of 48 Labrador retrievers, restricted dietary intake increased life expectancy by a mean of 1.8 years and delayed onset by a mean of two years of age-related diseases (Kealy et al, 2002).
Mean body condition score (BCS) in the diet-restricted group was 4.6 ± 0.19 on a nine-point scale, so they were leaner than the current suggested “optimum” BCS of 5/9. The control group mean BCS was 6.7 ± 0.19, so they were overweight, but not obese. Furthermore, a delay of six years existed between the groups for early radiographic evidence of osteoarthritic changes in hips and none of the Labrador retrievers in the diet-restricted group developed clinical signs of hip OA.
It is recommended to tailor analgesia to the patient’s specific needs – for example, the pain in OA is moderated through upregulation of cyclooxygenase pathways and proinflammatory prostaglandins, somatic pain via alpha receptors and visceral pain by kappa receptors.
Follow data sheet guidelines, but for potent drugs with recognised serious side effects, administer the lowest effective dose and/or reduce the frequency of administration.
It is good practice to use a validated pain scoring system such as the Glasgow Composite Measure Pain Scale (Thomas,1996) to establish a baseline against which to assess efficacy of treatment. A short form of this is available at www.isvra.org/PDF/SF-GCPS%20eng%20owner.pdf and the Colorado Canine Acute Pain Scale is at https://vasg.org/pdfs/CSU_Acute_Pain_Scale_Canine.pdf
I like to use and recommend the Canine Brief Pain Inventory with clients to evaluate efficacy of treatment modalities. It is at www.vet.upenn.edu/research/clinical-trials-vcic/our-services/pennchart/cbpi-tool
Almost one-third of 11 to 12-year-old dogs and 70% of 15 to 16-year-old dogs show cognitive disturbances including spatial disorientation, social behaviour disorders such as failure to recognise family members, repetitive (stereotype) behaviour, apathy, increased irritability, sleep–wake cycle disruption, inappropriate toileting and reduced ability to accomplish tasks (Neilson et al, 2001).
The author finds it very useful to use a Canine Cognitive Dysfunction Assessment tool, such as the one available from Purina – www.purinainstitute.com/sites/default/files/2021-04/DISHAA-Assessment-Tool.pdf
Aged dogs with cognitive decline show cognitive improvement on an antioxidant diet or with behavioural enrichment.
An antioxidant fortified diet appears to improve cognition by maintaining mitochondrial homeostasis (Snigdha, 2016; Dowling and Head, 2012; Head et al, 2009).
To minimise the risk of adverse events in geriatric dogs, only use licensed medicines (POM-V) and non-medical interventions proven to be safe and effective in dogs. Pet owners are wasting millions of pounds every year on products being recommended and sold by veterinary practices when there is little or no scientific evidence to support their use.
As they may have impaired organ function, whenever possible polytherapy should be avoided. Problems associated with polytherapy include:
Health screening should be done before administration of potentially toxic medicines – especially before general anaesthesia (Davies and Kawaguchi, 2014) to ensure no renal or hepatic impairment as, if present, many drugs are contraindicated or need dose adjustment to be safely administered (Table 2).
| Table 2. Medicines contraindicated or requiring dose adjustment in elderly dogs with hepatic or renal impairment (Allerton, 2023) | ||
|---|---|---|
| Drug | Hepatic/renal | Adjustment required |
| Amikacin | Renal failure Nephrotoxic |
Avoid if possible or adjust dose as above |
| Amoxicillin | Renal failure | Double dosing interval or halve dose |
| Amphoteracin B | Renal failure Nephrotoxic |
Avoid if possible or adjust dose as above |
| Ampicillin | Renal failure | Double dosing interval or halve dose |
| Aspirin | Hepatic insufficiency Contraindicated |
Avoid |
| Azathioprine | Hepatic failure Contraindicated |
Avoid |
| Cefotaxime | Hepatic insufficiency | Avoid if possible or double dosing interval or halve dose |
| Cefalexin | Renal failure | Avoid if possible or increase dosing interval ×2 – ×4 depending on creatinine clearance rate |
| Chloramphenicol | Renal failure Hepatic insufficiency Contraindicated |
Avoid if possible Avoid |
| Clindamycin | Hepatic insufficiency Contraindicated |
Avoid |
| Cyclophosphamide | Hepatic insufficiency | Avoid if possible. Double dosing interval or halve dose |
| Diazepam | Hepatic insufficiency Contraindicated |
Avoid |
| Digoxin | Renal failure | Avoid if possible or adjust dose as above for nephrotoxic drugs |
| Doxorubicin | Hepatic insufficiency | Avoid if possible. Double dosing interval or halve dose |
| Doxycycline | Hepatic insufficiency | Avoid if possible. Double dosing interval or halve dose |
| Fluorouracil | Hepatic insufficiency Contraindicated |
Avoid |
| Furosemide | Hepatic insufficiency Contraindicated |
Avoid |
| Gentamicin | Renal failure Nephrotoxic |
Avoid if possible or adjust dose as above |
| Hydralazine | Hepatic insufficiency Contraindicated |
Avoid |
| Lidocaine | Hepatic insufficiency Contraindicated |
Avoid |
| Metronidazole | Hepatic insufficiency Contraindicated |
Avoid |
| Morphine | Hepatic insufficiency Contraindicated |
Avoid |
| Nitrofurantoin | Renal failure Contraindicated |
Avoid |
| NSAIDs | Renal failure Hepatic insufficiency |
Avoid if possible or adjust dose as above Avoid if possible. Double dosing interval or halve dose |
| Oxytetracycline | Renal failure Nephrotoxic Contraindicated |
Avoid |
| Paracetamol | Hepatic insufficiency Hepatotoxic |
Avoid |
| Penicillin | Renal failure | Double dosing interval or halve dose |
| Pentobarbital | Hepatic insufficiency | Avoid if possible. Double dosing interval or halve dose |
| Phenobarbital | Hepatic insufficiency | Avoid if possible. Double dosing interval or halve dose |
| Propanolol | Hepatic insufficiency | Avoid if possible. Double dosing interval or halve dose |
| Theophylline | Hepatic insufficiency | Avoid if possible. Double dosing interval or halve dose |
| Tobramycin | Renal failure Nephrotoxic |
Avoid if possible or adjust dose as above |
| Trimethoprim/ sulphonamide | Renal failure Nephrotoxic |
Avoid if possible or Increase dosing interval ×2 – ×4 depending on creatinine clearance rate |
| Vincristine | Hepatic insufficiency | Avoid if possible. Double dosing interval or halve dose |
| This is not a comprehensive review of all medicines that may be a problem in geriatric dogs with renal or kidney impairment so always review the product data sheet at the Veterinary Medicines Directorate before administering medicines and screen the patient for potential problems: www.vmd.defra.gov.uk/ProductInformationDatabase Non-nephrotoxic drugs are best avoided – if not, reduce dose or increase dosing interval. For nephrotoxic drugs avoid if possible – if not, a dose adjustment can be based on creatinine clearance rates; however, this is not done often in first opinion practice, so an alternative is to use the following: if isosthenuric (urine specific gravity values in the 1.008 to 1.010 range): normal dose × 0.33 (one third). If azotaemic: normal dose × 0.25 (one quarter). |
||
Many drugs and some nutrients have interactions with medicines resulting in increased or decreased efficacy, and increased deficiency or toxicity risks. Well-known examples are concurrent use of corticosteroids and NSAIDs, or the use of antacids and minerals/vitamins bioavailability. This is another reason to avoid polytherapy in geriatric patients.
If multimodal therapies are necessary, check on reported interactions before introducing them.
The veterinary profession’s objectives in geriatric patients are to prevent or delay the onset of age-related disorders, to delay progression and to maintain pain-free good quality of life for the dog.
Early diagnosis is important so intervention can be started as early as possible and client education is essential to put in place preventive strategies and help owners to recognise sentinel signs and report them as early as possible.
Owners should be provided with detailed verbal and written advice to avoid, delay or minimise the onset and progression of age-related diseases.
Based on our understanding of ageing and age-related diseases, the most important advice is the following.
Maintain a BCS of about 4.6/9 throughout life, so their dog should look lean.
The author recommends monthly to identify any changes early (for example, weight gain or loss) that might be an early indicator of nutritional inadequacy or subclinical disease.
Feed a complete balanced fixed formula ration that has been analysed post-production to ensure compliance with FEDIAF guidelines. Homemade rations are highly unlikely to be compliant and cannot be relied on (Davies, 2014b). Do not rely on the label declaration of “complete” on a pet food label as studies have shown that most UK pet foods do not comply with FEDIAF guidelines (Davies et al, 2017) with similar findings in relation to the Association of American Feed Control Officials guidelines globally (Burdett et al, 2018; Kanakubo, 2015).
Maintain a regular exercise regime.
Report to the veterinary practice as soon as possible:
As veterinary professionals, our obligation is to prevent or relieve suffering and in the management of geriatric dogs maintenance of a pain-free good quality of life existence is more important than increasing life span.
When facing end of life decisions, the author finds that many of my clients appreciate the opportunity to use the quality of life assessment form available through Ohio State University (bit.ly/3u3WlZW).
Our growing knowledge of the mechanisms underpinning ageing and age-related diseases helps to define the measures that we need to take to maximise healthy ageing and avoid or delay the onset and progression of disorders that can impact on quality of life and life expectancy. However, to achieve these objectives we need full cooperation of dog owners – especially regarding preventive measures through vaccinations and dietary advice.
Some drugs mentioned in this article are used under the cascade.
