Defining the Geriatric Patient
Identifying the Geriatric Patient
In human and veterinary patients alike, the body endures physiological changes as it ages. It can be somewhat arbitrary to assign a specific age to separate geriatric patients from their younger counterparts. The World Health Organization considers men aged 65 and older as elderly and those aged 80 and older as the oldest-old (or aged) (Beaglehole et al., 2001). Due to the difference in body size and mass in breeds of dogs, there is generally a sliding scale for assigning age group labels based on dogs’ body weights. A study from the United Kingdom reinforced previous reports stating that giant dog breeds lived shorter median life spans than small and toy breed dogs (Adams et al., 2010). The 2006 Demographic Survey of U.S. Pet Ownership by the AVMA reported 29.8% of the canine pet population was aged 6–10 years old and 14.1% was aged 11 years and older (American Veterinary Medical Association, 2007). Extrapolating from Table 18.1, between 14.1% and 43.9% of the pet population is moving into the second half of their life span. Understanding aging is important so that adjustments can be made to accommodate for physiologic changes that occur in older patients.
Adapted with permission from Goldston (1995).
|Dog size||Body weight (lb)||Age (mean ± SD)|
|Small||0–20||11.48 ± 1.86|
|Medium||21–50||10.19 ± 1.56|
|Large||51–90||8.85 ± 1.38|
|Giant||>90||7.46 ± 1.27|
The Physiologic Changes of Aging
Aging is a complex process that occurs at the genomic, cellular, and organ level. Each organ system experiences decreased function and degeneration with aging, known as senescence. Susceptibility to disease increases with age as the body’s ability to respond to stress and maintain homeostasis declines. Cellular metabolism releases reactive oxygen species that cause free radical or oxidative damage (Figure 18.1). Oxidative damage reduces mitochondrial function, which affects the normal mechanisms of cell differentiation and apoptosis (Johnson et al., 1999). In the case of cancer, it is suspected that normal apoptosis is interrupted, and rapidly dividing cells or cells with mutations propagate.
As the body ages, lean body mass including muscle, bone, and cartilage declines (Metzger, 2005). These changes are often seen as muscle atrophy, which may be secondary to loss of muscle fibers themselves, reduced oxygenation of the muscles, or fibrosis developing within the muscles (Goldston, 1995). Muscle atrophy leads to loss of strength in the tendons. Decreased support for the joints to combat weight-bearing forces leads to increased stress on the bone and cartilage. Studies have shown a decline in the number of chondrocytes of aging patients due to cell senescence and decreased ability to respond to growth factors. Additionally, the water content of the cartilage declines with age, leading to thinning of the cartilage layer (Martin and Buckwalter, 2003; Loeser, 2010). Age-related thinning of cartilage and increased stress on the joints due to loss of muscle strength predispose the geriatric patient to eburnation of subchondral bone and the onset of osteoarthritis, one of the most common musculoskeletal conditions seen in geriatric patients.
While we do not recognize osteoporosis as a common condition in dogs, their bones can become more brittle with age due to infiltration of fat into the bone marrow and thinning of the cortex (Beaglehole et al., 2001). Consequently, fracture healing is often slower in geriatric patients as it is more difficult for bone callous to form. Aging patients lose lean body mass while body fat increases, often leading to obesity (Figure 18.2). Both obesity and brittle bones can exacerbate the symptoms and rate of progression of degenerative joint disease (DJD).
Coordination and proprioception decline in older patients, leading to ataxia. Combined lack of proprioception, loss of muscle strength, and postural instability contribute to falls in elderly humans. Awareness of joint movement (kinesthesia) and where the body is in space (joint position sense) contribute to proprioception, which, along with sensory factors such as vision and vestibular input, is important for maintaining balance.
Mechanoreceptors innervated by large myelinated nerve fibers provide input necessary for proprioception. The muscle spindle is a stretch-sensitive mechanoreceptor that provides input on joint position and facilitates coordinated movement. With aging, muscle spindle cells become less sensitive, joint and tendon mechanoreceptor volume declines, myelinated nerve fibers decline, tactile sensitivity decreases at a greater rate in distal extremities, and nerve conduction velocity slows in the advanced elderly, presumably all contributing to a decline in proprioception (Figure 18.3) (Shaffer & Harrison, 2007).
Aging patients experience sensory losses including decreased vision and hearing leading to lack of awareness of their environment. Vision can be affected by trauma, corneal issues such as keratoconjunctivitis sicca (KCS), lens issues such as cataracts or lens luxation, and retinal issues such as degeneration and detachment secondary to hypertension. Hearing can decline due to sensorineural changes known as presbycusis in people (which encompasses loss of hair cells, neural loss, and strial or cochlear audio-conductivity loss), drug ototoxicity, or trauma (Shimada et al., 1998).
Cognitive decline is seen along with several neurodegenerative changes in the brain in geriatric dogs. Documented changes in the brain include oxidative stress, deposition of β-amyloid plaques (as seen in human patients with Alzheimer’s disease), DNA fragmentation or damage, and changes in intracellular signaling leading to a loss of neurotrophic factors (Dimakopoulos & Mayer, 2002). Grossly, cortical atrophy and increased ventricular volume have been noted in the aged canine brain, along with reduced neurogenesis in the hippocampus, which is responsible for learning and memory (Head, 2011). Cognitive dysfunction syndrome (CDS) is a diagnosis of exclusion when signs such as change in sleeping habits, lack of recognition of the environment, decreased interaction with other pets and people in the house, restlessness, apathy, anxiety, altered appetite, aggression, or vocalization develop.
Metabolic changes in the geriatric patient include decreased metabolic rate and immune compromise (Goldston, 1995). Maintenance energy requirements (MERs) in older dogs decline by approximately 20% as compared to young adult dogs. Senior diets are commonly restricted in calories due to reduced caloric needs in an attempt to prevent weight gain. However, they should provide an increased percentage of highly digestible protein, with a total of at least 25% (Laflamme, 2005).
Proficiency of the bone marrow declines with age. A study in Beagles showed that the phagocytic ability of neutrophils declined by about 39% in 10-year-old dogs (Hall et al., 2010). Another study in German Shepherds showed decreased white blood cell and peripheral lymphocyte counts in older dogs. However, it contradicted the more recent study in Beagles and did not detect a difference in phagocytic ability of the polymorphonuclear cells (Strasser et al., 2000). Lymphocytic proliferative responses to mitogenic stimulation decline with age, and CD4 : CD8 (or helper T cell : cytotoxic T cell) ratios decline, indicating impairment of cell-mediated immunity. Geriatric dogs maintain humoral immune responses allowing them to respond to vaccines and novel antigenic stimulation. Further research is warranted to investigate the effect chronic antigenic exposure has on low-level inflammation in the body and the relevance it has to the development of inflammatory disease later in life (Day, 2010).
Other Changes Associated with Aging
The stability of the cardiovascular system should be evaluated in the geriatric rehabilitation patient. Cardiopulmonary changes in elderly patients include declining cardiac output, decreased elasticity with concurrent fibrosis of the pulmonary tissue, and decreased cough reflexes. Pulmonary secretions often have decreased viscosity, leading to difficulty expelling air and reduced resistance to respiratory disease (Goldston, 1995).
Behavioral issues may develop in geriatric patients, including decreased interaction with the owner, house soiling, altered sleep cycles, restlessness, disorientation, anxiety, and aggression. All of these issues can have individual causes, medical causes, or can also be related to CDS.
Owner Concerns for the Geriatric Patient
Owner concerns when presenting a geriatric dog include reduced mobility (trouble rising, inability to use the stairs and get in or out of the car, and decreased willingness to go on walks), increased pain, urinary or fecal incontinence, changing appetite, and decreased mental alertness or interaction with the family. The goal for rehabilitation therapists is to improve functional ability in the home environment, to improve quality of life and interaction with the owner, and to assist the owner to manage the patient’s compromised function (Figure 18.4).
Medical Issues Commonly Encountered in Geriatric Patients
Physiologic changes in the body due to aging lead to decreased reserves in the organ systems. Routine screening for medical conditions with more frequent physical examinations and diagnostic testing should be encouraged. Physical rehabilitation in geriatric patients often must be tailored to accommodate for medical issues to avoid compromising the patient’s condition when providing treatment.
Metabolic, Endocrine, and Hematologic Disorders
Older patients can have issues with lethargy, weakness, wound healing, change in quality of hair coat, urinary habits, body weight, and general immune resistance to infection. Proper diagnosis of conditions that contribute to these issues is important to allow patients to tolerate and receive more treatment and to protect them from exposure to other patients in the physical rehabilitation environment.
The most common causes of primary hypothyroidism in the dog are lymphocytic thyroiditis and idiopathic atrophy of the thyroid parenchyma. Secondary hypothyroidism due to a dysfunction in the pituitary gland can occur, leading to lack of thyroid-stimulating hormone. Skin issues that may develop in hypothyroid patients include seborrhea, hyperpigmentation, secondary pyoderma, and otitis externa. These issues can impede treatment choices, including use of electrical stimulation over compromised skin or the ability to use hydrotherapy.
Hypothyroidism should be considered in patients exhibiting muscle atrophy or neurologic signs such as weakness, knuckling, ataxia, seizures, vestibular signs, or facial nerve paralysis (Figure 18.5). Thyroid supplementation can help resolve most of the clinical signs associated with this endocrine disorder.
Hyperadrenocorticism (Cushing’s disease) leads to pituitary-dependent, adrenocortical, or iatrogenically induced excess cortisol in the blood. Cushing’s patients can exhibit skin issues such as hyperpigmentation and calcinosis cutis. They are predisposed to obesity, a pot-bellied appearance, muscle wasting, and neurologic signs such as ataxia and circling.
Hypoadrenocorticism (Addison’s disease) is characterized by lack of mineralocorticoid and glucocorticoid secretion, and is often due to an immune-mediated destruction of the adrenal gland. Lethargy and weakness are the most common clinical signs affecting the rehabilitation patient. Addisonian patients should be monitored for response to stress during visits to the rehabilitation facility and may need additional glucocorticoid supplementation.
Patients with diabetes mellitus may present for signs of peripheral neuropathy such as scuffing, dropped tarsi (a plantigrade stance more common in cats), or other issues related to weakness (Figure 18.6). Secondary complications include cataracts and poor wound healing. Adequate diabetic control is necessary when treating these patients to ensure progress with therapy is not hindered.
Anemia is decreased red blood cell mass in the body and often presents as pallor and weakness. Some causes of anemia are irreversible, so rehabilitation should be pursued more cautiously with these patients to prevent depleting their energy due to poor perfusion of oxygen to the tissues.
Immune compromise may be secondary to diseases such as neoplasia, iatrogenic drug suppression, or resistant infections. Routine screening with lab work and urine cultures should be pursued, and these patients should receive appropriate antibiotic therapy if warranted.
Obesity is exacerbated by poor metabolism secondary to some of the medical issues mentioned above. Fat tissue contains leptin, a hormone that promotes the release of inflammatory mediators such as tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, IL-6, and C-reactive protein (Laflamme, 2005). Increased inflammation in the body and concussive forces on the joints due to carrying more body mass predispose obese patients to more severe osteoarthritis.
A study published in 2002 showed that food-restricted dogs had longer median life spans and delayed onset of chronic disease (Kealy et al., 2002). Weight reduction (11–18% of body weight) decreased hind limb lameness in dogs with radiographic evidence of hip osteoarthritis in one study, while another showed weight loss (6.10–8.85% of body weight) decreased lameness and improved kinetic gait analysis scores in dogs with radiographic evidence of elbow or hip osteoarthritis (Figure 18.7) (Impellizeri et al., 2000; Marshall et al., 2010). Yet another study showed intensive physiotherapy in addition to caloric restriction provided improved weight loss, mobility, and ground reaction forces in dogs with osteoarthritis over caloric restriction alone (Mlacnik et al., 2006).
In a survey of breed clubs in the United Kingdom in 2004, the most common cause of death was cancer (27% of patients surveyed) (Adams et al., 2010). Aging increases the risk of patients developing cancer. Monitoring for rapid weight loss (cachexia), muscle wasting, dyspnea, peripheral lymphadenopathy, or enlargement of the abdomen is recommended. Many of the modalities used in physical rehabilitation are contraindicated over areas of malignant tumors as they increase regional blood flow. Patients receiving chemotherapy should be monitored for nadirs in white blood cell counts, which may warrant postponing therapies such as hydrotherapy until their blood counts stabilize.
Cardiovascular and respiratory conditions more commonly encountered in geriatric patients include endocardiosis, cardiomyopathy, arrhythmias, pulmonary fibrosis, laryngeal paralysis, neoplasia, pneumonia, and bronchitis. Symptoms of coughing, abdominal swelling (due to ascites), exercise intolerance, syncope, dyspnea, or cyanosis are all indications of cardiac disease.
Parenchymal pulmonary conditions that may be encountered in geriatric rehabilitation patients include pulmonary fibrosis, pneumonia, or neoplasia. Pulmonary fibrosis is an interstitial lung disease overrepresented in West Highland White Terriers (Norris et al., 2005). Exercise intolerance, coughing, and dyspnea are the most common clinical signs. Pneumonia often has an infectious (viral or bacterial) origin, and can be incited by aspiration. Chronic bronchitis, most commonly seen in older small breed dogs, is characterized by exercise intolerance and a slowly progressive cough.
Dogs with laryngeal paralysis may present with stridor, respiratory distress, or changes in bark. Paralysis of the recurrent laryngeal nerve, which innervates the muscles that abduct the arytenoid cartilages, results in upper airway obstruction. Caution should be used with these patients in the underwater treadmill to avoid compromising air exchange secondary to exertion or excitement. Laryngeal paralysis is often idiopathic, but polyneuropathy, hypothyroidism, and neoplasia should be considered when patients present with signs of this condition. One study documented denervation of muscles in the larynx and pelvic limbs (associated with the recurrent laryngeal and sciatic nerves) in 11 laryngeal paralysis cases, supporting evidence of polyneuropathy with this condition (Thieman et al., 2010).
Megaesophagus in an older dog is acquired esophageal weakness, due to primary idiopathic causes or secondary to a neuropathy, myopathy, or junctionopathy. Most patients present for regurgitation, and a common complication of the disease is aspiration pneumonia. Treatment of underlying diseases such as myasthenia gravis, hypothyroidism, or hypoadrenocorticism can be beneficial in controlling megaesophagus, so a diagnostic workup should be recommended in patients with regurgitation. A recent study found all dogs enrolled with idiopathic laryngeal paralysis (n = 32) also had esophageal dysfunction. Of 24 dogs that were evaluated at 1 year, 100% of the subjects had developed neurologic signs including ataxia, weakness, conscious proprioceptive deficits, or muscle atrophy while only 25% of the subjects exhibited some form of these signs at enrollment (Stanley et al., 2010).
Chronic renal disease is commonly encountered in older patients. Renal blood flow and the reserve of healthy renal glomeruli decline with age (Goldston, 1995). Patients with compromised renal reserves are more sensitive to insults such as dehydration and should not be overworked in the physical rehabilitation environment.
Urinary and Fecal Incontinence
Urinary and fecal incontinence may occur secondary to resistant urinary tract infections, neuropathies, reduced sphincter control, or hormonal imbalance. Neurologic conditions often have side effects of loss of urinary and anal sphincter control. Sanitary concerns should be addressed in these patients when determining appropriate treatments. Many rehabilitation facilities will not allow incontinent patients in the underwater treadmill or pool. These patients should be evaluated for urine scald or irritation of the perineal area. Laser therapy is useful in treating compromised skin. Owners can learn how to express the urinary bladder or stimulate bowel movements (e.g., cotton swabbing the rectum) to maintain a sanitary elimination schedule.
Resistant Urinary Tract Infections
Patients that are unable to fully empty their urinary bladder are predisposed to urinary retention and subsequent urinary tract infections. Dogs with spinal cord injuries are at risk for compromise of the nerves supplying the bladder sphincter and can be susceptible to resistant urinary tract infections. Multidrug-resistant Escherichia coli as well as methicillin-resistant Staphylococcus pseudintermedius (MRSP) and methicillin-resistant Staphylococcus schleiferi (MRSS) are being encountered more commonly in recumbent geriatric patients due to the tendency to develop antibiotic resistance as they age (Hoekstra & Paulton, 2002). The cause of antibiotic resistance may be inappropriate drug use, such as underdosing the patient or not treating an infection for an adequate duration. One study of dogs with multidrug resistant extraintestinal E. coli and Enterobacter spp. infections found the urinary tract to be the most common infection site (62%) with predisposing factors including prior antimicrobial use, increased duration of hospitalization (more than 2 days), or a prior surgical procedure. As is common in human patients, urinary catheterization is a predisposing risk factor (Gibson et al., 2008).
Regular urinalyses and urine cultures should be performed to evaluate appropriate antibiotics to treat urinary tract infections while aiming to prevent the development of antibiotic resistance. It is prudent to avoid putting patients with resistant urinary tract infections in the underwater treadmill or therapy pool.
Decubital ulcers or pressure sores occur as a result of unrelieved pressure on the skin over bony prominences. Loss of blood supply to the tissue and necrosis of the subdermal tissue occurs. The skin initially becomes erythematous, alopecic, and thinner, and later appears darker in color. Recumbent patients with thin body condition and poor muscle mass are at greatest risk for decubital ulcers (Figure 18.8). These patients should not go in the underwater treadmill or therapy pool without a waterproof seal over the wound. The decubital ulcer should be cultured to determine appropriate antibiotic therapy, pressure should be relieved if possible, and the wound should be cleaned regularly. Topical therapy may be used in addition to oral antibiotics and laser therapy to promote local blood supply and wound healing.