Introduction

Spinal cord injuries are among the most common problems encountered by general practitioners, neurologists and surgeons, with trauma and intervertebral disc disease (IVDD) being the two most prevalent etiologies. Whilst IVDD is rare in cats, trauma is commonly encountered in this species, with a prevalence between 0.02-0.12% (1,2), whereas IVDD accounts for more than 2% of all conditions diagnosed in dogs (3). Other causes of spinal cord disabilities include wobbler syndrome, discospondylitis, fibrocartilaginous embolism (FCE), neoplasia and degenerative myelopathy. For many spinal pathologies, surgical treatment improves the prognosis for functional recovery, but in others it is not indicated or not applicable. Even with an accurate diagnosis and specific therapy (e.g., surgery), if subsequent nursing care is inadequate, the spinal patient may not recover optimally, and can suffer unnecessary discomfort, pain, or even fatal complications. This article seeks to emphasize the most important aspects of supportive care, with the aim of making rehabilitation of the spinal patient both more successful and humane. 

Pain control

Discomfort in the spinal patient is often a complex combination of injury to the spinal cord or nerve roots (referred to as neuropathic pain), myalgia, or surgically induced trauma. Clinical history and careful examination to identify pain generators are necessary to develop a patient-specific pain management protocol. This complex pain may not be controllable with any single pharmaceutical or modality, and a multimodal approach is to be preferred – bear in mind that the use of gabapentin in combination with an opioid, nonsteroidal anti-inflammatory drugs (NSAIDs) or antidepressants has shown positive responses in the treatment of neuropathic pain in people (4). Commonly used drugs for animals are described in Table 1.

• NSAIDs are valuable as analgesics, either alone or as part of a multimodal analgesic plan. Commonly used NSAIDs in dogs include aspirin, carprofen, etodolac, meloxicam, ketoprofen, deracoxib, firocoxib, meclofenamic acid, and tolfenamic acid. NSAID administration should be only considered in normotensive, well-hydrated patients with normal hepatic, renal, gastrointestinal and hemostatic function. In addition, NSAIDs should not be combined with corticosteroids, and two or more NSAIDs should not be administered concurrently.
• Acetaminophen (paracetamol) is not traditionally considered an NSAID because it does not have significant anti-inflammatory activity; the analgesic and antipyretic actions of the drug are related to COX-3 inhibition. Acetaminophen is occasionally used as an analgesic in dogs as a stand-alone medication, or in combination products containing codeine, hydrocodone or tramadol. Acetaminophen is contraindicated in cats at any dosage because of fatal side effects.
• Opioids are some of the most effective analgesics used in veterinary medicine. They interact with various types and subtypes of opioid receptors present in the central and peripheral nervous system. This directly inhibits the ascending transmission of nociceptive information arising from the dorsal horn cells and activates pain-control circuits that descend from the brain to the spinal cord. In addition, these drugs interact with opioid receptors in sensory nerves, thus opioids assist in both central and peripherally mediated analgesia (5).
• Gabapentin and pregabalin are synthetic branched-chain amino acids that inhibit calcium influx-mediated release of excitatory neurotransmitters, including substance P. Gabapentin and pregabalin are used as anti-seizure drugs in people and animals, but both also reduce neuropathic pain, with pregabalin having the greater effect (6). Gabapentin use has increased significantly in veterinary medicine over the past several years, and although there are no clinical trials evaluating its safety and efficacy as an analgesic agent in dogs, it has anecdotally been used to treat many types of pain, including neck and back pain in animals with IVDD.
• Amantadine is a drug that blocks N-methyl-d-aspartate (NMDA) glutamate receptors. These receptors are important in central nervous system sensitization and hyperalgesia. Amantadine may enhance the analgesic effects of NSAIDs, opioids or gabapentin/pregabalin (7).

Table 1. Commonly used analgesic medications for spinal pain.

Neurology of the bladder

One of the most important aspects of nursing support for a paralyzed patient is the assessment of the animal’s ability to urinate effectively. Unfortunately, urine retention is too often overlooked because there is a focus on the obvious limb dysfunction, and overflow incontinence can be misinterpreted as voluntary micturition. The consequences can be discomfort, a predisposition to urinary tract infection (UTI), and chronic bladder distension and detrusor atony. It is therefore important that client education should always emphasis the need for good bladder management. Techniques for manual bladder evacuation (when possible) may be instructed during the animal discharge from the clinic, but usually needs further communication during recheck visits. As a rule of thumb, most dogs and cats recover voluntary control over micturition concomitant with recovery of voluntary/purposeful appendicular motor function (even if yet non-ambulatory). 

Micturition, the process of storing and periodically voiding urine, involves a complex series of neural pathways that control the urinary bladder and urethra. The primary control center for micturition is located in the pons, with nerve pathways projecting from the micturition center traveling caudally in the spinal cord to the lumbar and sacral segments that innervate the bladder and urethra. Depending on the localization of the spinal injury, there are two types of urine retention.

Upper motor neuron (UMN) bladder 

In most cases of intervertebral disc extrusions, the spinal cord lesion is cranial to the sacral spinal cord segments. With severe lesions, the ascending sensory pathways and descending motor pathways responsible for micturition are compromised. Detrusor and urethral tones are increased because of loss of inhibition from the brain. The bladder becomes over-distended and feels firm, and there is substantial resistance to manual evacuation of the bladder, although there may be inconsistent leakage of urine from an overly full bladder (overflow incontinence). Patients usually develop a variable degree of so-called “reflex voiding” after two weeks; this is still involuntary and occurs often when stimulated by abdominal pressure, such as picking up the patient. It is quite common for the owner to view this as evidence of voluntary micturition, but actually it is still incomplete voiding.

Lower motor neuron (LMN) bladder 

Less common in patients with disc extrusions, here the lesion affects the caudal lumbar spinal cord segments or sacral nerves. This results in loss of voluntary micturition, accompanied by decreased tone in the detrusor muscle and urethra. Typically, the bladder feels flaccid and is easily expressed. Overflow incontinence is common when the bladder is distended, and the patient often leaks urine spontaneously or in response to abdominal pressure. Patients with LMN bladder are much easier for the owner to manage, as less effort is needed to evacuate the bladder.

Management of urine retention 

All patients with paresis should be monitored closely for micturition compromise, as urine retention increases the risk of UTI, as well as bladder overdistension or persistent atony (8,9). As explained above, patients may leak urine due to decreased urethral tone (LMN bladder) or overflow incontinence (UMN bladder). For a paretic patient, the way to evaluate bladder function is to take it outside and allow adequate time for voluntarily urination. Even if the patient voids, the bladder residual volume should then be assessed by ultrasound exam; normal residual volume after voiding is 0.2-0.4 mL/kg (usually < 10 mL total) (8).

In patients that do not urinate voluntarily or have excess residual volume, the first step is to attempt manual bladder expression. This can be done with the patient in lateral recumbency or supported in a standing position, whichever is more comfortable (Figure 1). If the patient starts to tense its abdominal muscles, it is important to release pressure until the patient relaxes and then start again; never try to “overpower” the patient.

If the bladder cannot be comfortably expressed, the next step is catheterization. This should be done as aseptically as possible, and sedation may be helpful for patient comfort. Catheterization of male animals is straightforward, but somewhat more difficult in females (Figure 2). Where catheterization is expected to be difficult or uncomfortable, it is often beneficial to place an indwelling silicone Foley urinary catheter or cystotomy catheter through the abdominal wall (Figures 3 and 4).

Drug therapy is helpful in altering detrusor and urethral tone, but no drug will restore voluntary urination in a patient with spinal cord disease. Such therapy is only one component of management and not a substitute for other therapies such as manual bladder expression or catheterization. Commonly used drugs are described in Table 2.

Table 2. Frequently used medications for management of urinary retention. 

Urinary tract infection 

UTI is a common complication of spinal cord disease, occurring in 27-42% of patients. Risk factors for the development of UTI include loss of ambulation, inability to voluntarily urinate, duration of inability to urinate, and a body temperature less than 35°C during anesthesia. Perioperative administration of cefazolin decreased the risk of UTI in one study (10). Escherichia coli and Enterococcus spp. are the most common isolates, but many UTIs are occult, with no clinical signs and no hematuria or pyuria detected on urinalysis. Any confirmed UTI is treated with (at least) a 10-day course of antibiotics chosen on the basis of susceptibility testing. Several days after antibiotic therapy is discontinued, another urine sample should be submitted for culture to ensure infection is eradicated. 

Defecation 

Generally speaking, fecal incontinence is less concerning than urinary incontinence in paralyzed dogs and cats. Animals with lesions cranial to S2 may well have some degree of constipation, but signs of discomfort in patients with fecal retention are rarely recognized, and the reflexive emptying of stool appears to occur with much less effort than with urine emptying. As with LMN bladder incontinence described earlier, the key nursing care element is prevention of fecal soiling and subsequent dermatitis, as the patient may be unaware of (and unable to move away from, due to paralysis) any bowel movement. 

Indeed, since soiling is a risk with both fecal and urinary incontinence, nursing care should aim to minimize the potential for secondary skin damage in either situation. Fecal soiling can be combated by frequent examination and cleansing, shaving the perineum, and wrapping the tail, and appropriate dermal medications can also be employed to soothe irritated skin. 

Hydration and nutrition 

Patients with acute paralysis usually have anxiety and discomfort, which may adversely affect their intake of food and water. Dehydration is particularly harmful for animals with spinal cord injury, as this may cause a reduction in spinal cord blood flow where circulation in the injured segments may already be compromised. It is therefore always a consideration as part of the early and ongoing nursing care and management of patients with spinal trauma and neurologic deficits to provide intravenous fluid support. 

Adequate nutrition is important to slow catabolism and provide precursors for optimal immune function, tissue repair, and drug metabolism. Nutritional support must be considered for any patient that has had inadequate food intake for more than three days. Patients that cannot or will not eat, but have a normally functioning gastrointestinal tract, should receive enteral feeding of some sort – nasoesophageal tubes are generally used for short-term support (3-7 days).

Recumbency and decubital sores 

The inability of spinal patients to rise and walk predisposes them to pressure/decubital sores. An important part of nursing care is therefore provision of suitable substrates for the patient to lie on, and frequent shifting of position. Decubital sores are most common over bony prominences such as the ischium and greater trochanter (Figure 5). Moist skin increases the risk of sores developing, so the skin should be kept clean and dry. Recumbent patients should be kept on appropriate bedding such as sheepskin, foam or air mattresses, or trampolines. 

Sheepskin minimizes friction, absorbs moisture, and can be laundered. Air mattresses evenly distribute pressure, but can be punctured by a patient’s nails; they are also difficult to clean and do not absorb moisture, so must be covered with sheepskin or other suitable material. Trampolines (consisting of a plastic tubular frame that supports fiberglass netting) are excellent for larger recumbent patients (Figure 6); the trampoline distributes the patient’s weight evenly and the netting allows drainage of urine away from the patient’s skin. 

Doughnut-shaped bandages can be placed over bony prominences to prevent or treat decubital sores (Figure 7). Medical therapy for decubital ulcers includes topical antibiotic preparations and enzymatic debriding agents. Systemic antibiotics, frequent wound lavage, wet-to-dry bandaging, or surgery is indicated for more severe wounds (11). 

Respiratory care 

Recumbent patients can be at risk of developing several respiratory complications such as atelectasis and pneumonia. Pulse oximetry and blood gas analysis are indicated whenever respiratory compromise is suspected or anticipated, and chest radiographs must be obtained when pneumonia is considered. Recumbent patients should be turned every 4 hours to minimize atelectasis; keeping the patient in sternal recumbency or supported with a sling is also helpful. Nasal oxygen therapy should be administered in patients with decreased respiratory function. Pneumonia is treated with systemic antibiotics, nebulization, and coupage. 

Rehabilitation therapy

Physiotherapy, done at home or at a specialized facility, can play an important role in the treatment of animals with spinal cord disease. It may prevent secondary complications, and helps support the health and function of musculoskeletal tissues during recovery through various mechanisms (Box 1). 

Box 1. Benefits of physiotherapy in spinal patients.

As an example, establishment of realistic goals in the impaired IVDD patient will provide the owner with both a definition of success and an awareness of a potential therapeutic endpoint. Goals should focus on the re-establishment of ambulation and a level of musculoskeletal strength sufficient to provide a minimum level quality of life. Following patient assessment and establishment of treatment goals, a rehabilitation therapy program should be designed. The primary components include:

• Passive and Active Range of Motion exercises to maintain or improve proper joint and spinal function,
• exercises to increase both proprioceptive and kinesthetic awareness, 
• limiting disuse atrophy, and strengthening core muscles, 
• exercises to maintain or improve cardiovascular fitness,
• gait retraining.

Assessment of patient outcome is essential, so periodic reviews to document improvement are mandatory. Neurologic examination, video assessment and functional grading should be included in all re-evaluations.

Conclusion

Veterinarians must be aware of the various potential problems that can develop in spinal injury patients, and avoid becoming too focused on only the ambulation deficits that typically form the owner’s chief concern, and which are the most obvious, but not necessarily the most significant, functional loss the pet faces. By having in mind the potential for pain, urinary, fecal and respiratory problems that might accompany a paralyzed patient, and addressing these early on (with both the patient and owner), the clinician will be doing much to improve patient comfort, health, recovery, and client understanding of what management entails. 

References

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