2016 WINTER: Tracheal Collapse | When Care is Critical | Hyperthyroidism and Kidney Failure | Obesity and Osteoarthritis | Meet Our New Criticalist and Oncologist | Continuing Education
Tracheal Collapse: Diagnosis and Treatment
Carly Waugh, DVM, DACVIM
Tracheal collapse is a progressive disease of the cartilaginous rings within the trachea seen often in middle-aged, small-breed dogs. This is most commonly found in Yorkshire terriers, Pomeranians, pugs, Chihuahuas and toy poodles and results in dorsoventral narrowing of the tracheal lumen. The cause is unknown, but a strong genetic predisposition is suspected. Tracheal collapse should be suspected when dogs have a “goose honk” cough, noisy breathing and periodic dyspnea. Coughing episodes are worsened with excitement, anxiety and pressure on the trachea and can result in respiratory distress in severely affected dogs. As the condition progresses, the degree of collapse worsens, causing the cartilaginous rings to become more ovoid. This increases the cough severity and causes exercise intolerance. Severe tracheal collapse can also result in pulmonary hypertension and right-sided heart disease.
Definitive diagnosis and characterization of tracheal collapse is based on a combination of thoracic and cervical radiographs, fluoroscopy and tracheobronchoscopy. Collapse of the cervical trachea is best seen during inspiration, and intrathoracic collapse is seen best during exhalation on radiographs. With tracheobronchoscopy, tracheal collapse severity can be graded from grade I to IV (25-100% collapse). Laryngeal function and main stem bronchial collapse can also be assessed. Samples are often obtained for culture and cytology.
Medical management of tracheal collapse is the most important aspect of treatment, particularly when signs of collapse are first noted. Weight loss, limiting exposure to irritants (dust, cigarette smoke) and utilizing a harness rather than a collar are of paramount importance and can dramatically improve clinical signs. Oral antitussives (butorphanol, hydrocodone, diphenoxylate) are also important medications in helping to limit the clinical signs and progression of the disease. Tapering doses of corticosteroids (prednisone or inhaled fluticasone), bronchodilators (theophylline, terbutaline), and tranquilizers (acepromazine) are also used to treat affected patients. These patients are also predisposed to the development of bacterial tracheitis, necessitating antibiotic treatment if present.
When medical management is not successful in controlling clinical signs, more definitive treatment should be considered. Extraluminal placement of prosthetic rings can be performed, although this requires surgery. Recurrent laryngeal nerve damage can be a complication with this approach, and the blood supply to the trachea can be disrupted, causing tracheal necrosis.
Minimally invasive structural support of the trachea is now readily available, reducing risk of complications seen with extraluminal ring placement. Self-expanding nitinol stents can be placed, helping the trachea stay open by relying on the cylindrical shape of the stent. They are particularly advantageous due to the short post-operative recovery, rapid restoration of the airway and minimally invasive nature of placement. Measuring the tracheal diameter and length of stent can be challenging as the stents foreshorten during placement. Final stent width should be 10-20% larger than the maximal diameter of the trachea to prevent stent migration. The stent should be at least 1 cm caudal to the cricoid cartilage and 1 cm cranial to the carina and span the entire length of the collapse. Sizing is performed with the patient under general anesthesia with a measuring catheter in the esophagus, ideally with stent placement immediately following under the same anesthesia.
After stent placement, the patient is recovered and discharged with antitussives, sedatives, a tapering dose of corticosteroids and antibiotics. Aggressive control of the cough should be achieved for at least 4 weeks after stent placement in order to prevent stent fracture or granulation tissue formation. Radiographs are repeated at 1, 3 and 6 months post-placement. It should be noted that cough will persist after placement of the stent due to tracheal irritation, but improvement in quality of life should be noted quickly in appropriately selected patients.
BluePearl is pleased to now offer tracheal stenting in our Franklin hospital. For more information, please call and ask to speak with Carly Waugh, DVM, DACVIM.
When Care is Critical
Critical care medicine encompasses a wide variety of clinical diseases that overlap with many other veterinary specialties. Due to this overlap it is sometimes difficult for the public, or even other veterinarians, to understand the role of a criticalist. It is sometimes easier to start by understanding what a criticalist is not, in order to grasp what they are. The most common misunderstanding is that critical care and emergency medicine are the same. Although the specialty covers both areas, they are very different.
Emergency medicine is meant to receive incoming patients that are not scheduled; some of these will be true emergencies, and others will be due to owner convenience or perceived emergency. The main goal is to recognize the severity of illness, triage the patient and generate a starting plan focused on the most life-threatening problem.
A critical care service is meant to continue the daily care and diagnostic workup of the very sick patient that comes in through the emergency service or even from other services. Depending on the hospital and the level of illness, a patient may be transferred to a critical care service shortly after admission or even the next morning. The main goal of critical care is to monitor, anticipate and preempt patient needs. The focus is on the whole animal and to maintain as well as protect all body systems. Often, expertise from other services is sought for these patients, but the criticalist amalgamates the overall care so that nothing is missed.
So what constitutes the very sick? This is a bit subjective, and sometimes this is more obvious than others; however, there are some rules to go by. Classically, patients requiring mechanical ventilation and post-cardiac arrest patients are placed in the critical care service as well as patients with sepsis or shock of any etiology. Patients that are recovering from major abdominal or thoracic surgery also benefit from critical care, especially when the surgeon is in surgery and cannot check on them frequently enough. A critical care team, rather than an internist trying to see a full day of appointments, may better serve acute presentations of many medical illnesses such as diabetic ketoacidosis, pneumonia and IMHA. This is not to say that the ICU does not get busy, but the criticalist may have more flexibility in availability for patients than other services with appointments booked. Trauma and intoxications are other large areas under the umbrella of critical care. A trauma patient may require surgical repair of a fracture; however, this is usually best delayed until the patient is stable or proves he is not going to destabilize.
Essentially any patient that is unstable or may acutely change for the worse will benefit from a criticalist overseeing their care. The exact caseload will vary depending on each hospital and its specific needs.
Criticalists hope to demonstrate the benefit of critical care to the community we serve and become a vital part of the specialty services available for your patients.
Hyperthyroidism and Kidney Failure – a Concern?
Both hyperthyroidism and kidney failure are commonly seen in older cats. Occasionally, they may be present in the same patient. Unfortunately, hyperthyroidism can mask the signs and abnormal laboratory findings in cats with kidney failure making it difficult to confirm the presence of both conditions.
How does hyperthyroidism affect the kidney?
Thyroid hormone appears to enhance the responsiveness of beta-adrenergic receptors in the heart leading to increased heart rate, increased left ventricular contractility, and subsequently increased cardiac output. Thyroid hormone also appears to act on smooth muscle cells within the peripheral arteries causing relaxation and decreased peripheral vascular resistance. The decrease in arterial filling volume induces activation of the renin-angiotensin-aldosterone system, which stimulates increased sodium reabsorption by the kidneys and secondary water retention. The subsequent increase in blood volume increases blood return to the heart (increased preload). The increase in preload in combination with the decreased systemic vascular resistance also increases cardiac output.
An increase in cardiac output increases renal blood flow and, in turn, the glomerular filtration rate (GFR). BUN and creatinine are cleared more effectively from the body. The concurrent presence of kidney failure in cats with concurrent hyperthyroidism as assessed using BUN, creatinine, or even tests on GFR, is masked.
Now if you correct the hyperthyroid state, the patient’s cardiac output, and subsequently the GFR, return to normal. Kidney values once again increase. Azotemia has been reported to occur in 15% of hyperthyroid cats after treatment, despite the type of treatment.
Can you predict which cats will develop azotemia post-treatment?
Studies to date have failed to identify a marker that will identify those hyperthyroid cats with concurrent kidney failure. Pretreatment values for BUN, creatinine and even urine SG have failed to be reliable predictors for the development of post-treatment azotemia.
How long after treatment before azotemia would become evident?
Studies have indicated that the GFR will decrease during the first 2-4 weeks after treatment.
What is a methimazole trial?
Because it is the correction of the hyperthyroid state and not the type of treatment that unmasks the azotemia, it is possible to get a preview of the cat’s true kidney function, prior to curing the thyroid condition with radioactive iodine or surgery by performing what has been termed a methimazole trial. To perform a trial, administer methimazole with the goal of dropping thyroid hormone levels into the low-normal range. Once thyroid levels have normalized and are maintained for 4 weeks, blood tests performed 4 weeks later would be expected to demonstrate the BUN and creatinine values that you may see after radioactive iodine therapy or thyroidectomy.
When would a methimazole trial be performed?
We do not typically advise a methimazole trial since it does not exactly mimic what may be expected post-radioiodine. Additionally, the literature shows that the prognosis for cats treated with radioiodine, with or without azotemia, is better than those treated with methimazole. However, some clinicians recommend the trial be performed in cats 14 years of age or older and in those cats with any suspicion for concurrent kidney disease based on the patient’s history, exam findings and lab test results (significantly elevated BUN value and isosthenuria).
What if kidney failure develops after thyroid treatment?
The good news is that, despite the development of post-treatment azotemia, most cats continue to do fine. In one study, the median survival time in cats treated for hyperthyroidism that developed azotemia post-treatment was similar to treated cats that did not develop azotemia (>500 days). The treatment for kidney failure includes ensuring hydration, feeding an appropriate diet, and addressing the complications of kidney disease such as hypertension. Additionally, if the azotemia is secondary to post-radioiodine hypothyroidism it may resolve or be markedly stabilized with early identification and thyroid supplements.
Is there a preferred treatment for hyperthyroidism?
Radioactive iodine therapy is considered the most consistent and predictable means for curing hyperthyroidism in cats. It is technically simpler than other treatment options and involves only a single injection of the liquid chemical. There is no need to administer tablets or creams for the life of the cat or to feed an exclusive diet. Surgical thyroidectomy carries the risk of damaging the parathyroid glands. Meanwhile, poor client compliance, inadequate dosing, a risk for side effects, and the expense of the medication and recommended thyroid monitoring, associated with the use of methimazole are additional reasons to consider treating hyperthyroid patients with radioactive iodine. In one study, hyperthyroid cats treated with radioactive iodine were shown to live longer than those treated with methimazole, regardless of kidney status and despite the fact that the radioactive iodine-treated population was actually older in age.
Obesity and Osteoarthritis
The incidence of obesity is continuing to trend upwards, with the most recent AAHA weight management guidelines for dogs reporting that as many as 59% of our canine patients are obese. Obesity is defined as excess body fat capable of causing or exacerbating disease. When a body condition scale of 1-9 is used, each uptick in score beyond ideal is equivalent to 10-15% excess body weight.
Osteoarthritis (OA) affects at least 20% of dogs over one year of age. It can be very difficult to discuss weight management with owners; however, it is one of the most effective (and safe) treatments for OA in dogs. The take-home message for the owners of any obese dog with OA is that dogs are expected to live longer and more comfortably if they are a healthy weight. Labrador retrievers kept at a lean body weight (BCS 4-5/9) lived, on average, two years longer than their overweight littermates (BCS 6-7/9). In addition, continual pharmacologic treatment for OA is necessary in obese animals three years earlier than in those kept at a healthy weight.
Weight loss may be a daunting process for many owners. Start with small, achievable goals. Positive reinforcement is key – encourage the owners to stop by for a weight check on the clinic scale every 2-4 weeks, and make adjustments as necessary. It has been experimentally demonstrated that as little as 6% weight loss in obese animals can increase weight bearing and quality of life in dogs with osteoarthritis. Encourage moderate, controlled exercise. Gradually increasing distance of leash-walks, especially during the cooler times of day (dawn and dusk) will help maintain joint comfort and muscle mass and facilitate shedding the pounds. In the warm months of the year, swimming is also a fantastic means of exercise. Encourage owners to get into the water up to their knees to prevent their pets from running into and out of the water. Finally, professional physical therapy in conjunction with weight loss has shown more benefit than weight loss alone.
The first step to achieving weight loss is to determine exactly what is being fed. Encourage the owners to keep a journal of everything that is offered over a week’s time. Remember to keep it simple. Owners are less likely to be compliant if a “crash diet” is recommended. In addition, dogs that lose weight gradually are more likely to keep the weight off than those that quickly drop weight.
Calculate the patient’s energy requirement, and ensure that the owners are weighing the food at mealtime or using an eight-ounce measuring cup for precision and repeatability. Encourage low-calorie treats or breaking treats into multiple small pieces. Fruits and vegetables make excellent low calorie snacks (no grapes or raisins). It is important to remember that the nutrient composition of any food is calculated to provide balanced nutrition of all essential nutrients when fed based on caloric density. Therefore, if appropriate weight loss is not achievable on the diet the patient currently eats, it is recommended to switch to a weight control diet rather than substitute large volumes of food with green beans, pumpkin, etc., as deficiencies may result.
Finally, a multimodal approach to OA therapy including use of neutraceuticals, chondroprotectants, specific joint diets, NSAIDs and other analgesics is key in helping these animals be as comfortable as possible while achieving their weight loss. If an owner feels that their pet is exceedingly uncomfortable after exercise, they are unlikely to continue. When sedentary, these animals gain weight, become increasingly lame, and continue on a downward spiral.
We’d like to thank our colleague from BluePearl in Kentucky, Patricia Sura, MS, DVM, DACVS,
for allowing us to use this article for Companion.
FROM THE MEDICAL DIRECTOR
Medical Director’s Column
To our partners in the veterinary community,
We would like to take this opportunity to thank you for your trust and confidence in referring your patients to BluePearl Veterinary Partners in Franklin. We value our relationship with the primary care veterinary community and strive to provide you, your clients and their pets the highest level of veterinary emergency and specialty services.
As many of you may know, BluePearl Veterinary Partners has decided to join Mars Petcare, a family-owned business that is dedicated to the pet care industry. This is an exciting opportunity for our organization’s growth and support, and presents us with some new opportunities to improve the way we help pets.
We want to assure you that we will continue to maintain our absolute commitment to serving all members of the primary care veterinary community, because we know these relationships provide the necessary foundation for the best possible care for our patients.
We will also continue our commitment to offer high-quality referral specialty and emergency care and, consistent with our historical model, we will not offer primary care services. The decision to join Mars Petcare will not change our relationship with pet parents or the referral community.
Our leadership structure remains the same, as does our mission: to provide remarkable care for pets. With your support, we hope to continue toward our goal of being the community’s choice for veterinary specialty and emergency care.
If you have questions in regards to BluePearl joining Mars Petcare, please feel free to contact me at any time. I look forward to our continued partnership.
I would also like to take this opportunity to introduce our new criticalist, Dr. Kristen Datte, to our critical care team. We now are able to offer critical care services 7 days a week. We also have a new oncologist, Dr. Pamela Lucas, joining the oncology team. She will be seeing cases Tuesday through Friday. Please check out their bio introductions.
Kevin Au, BVMS, MS, DACVS-SA
Meet our specialists…
Kristen Datte, DVM, DACVECC
Critical Care Service
How do you go about helping to ease the concerns of an upset client?
I find that giving options for treating/addressing diseases allows clients to feel in control of situations. I initially focus on describing all concerns about the pet’s disease and options for treating each of these. I feel that educating people about the disease and complications and allowing them to choose the treatment option increases confidence in their decisions and me.
How do you like to work with the primary care veterinarian?
The primary care veterinarian has many roles, including initial diagnosis, therapy and discussion of the disease process with the owners. Primary care veterinarians have years of experience with the clients and their pets. I am happy to discuss cases with the primary care veterinarian and provide progress updates. Follow up after discharge is turned over to the primary care veterinarian. I am always happy to follow the case afterwards with the primary care veterinarian.
Was there an event or course in vet school that changed the direction of your career?
Two parts of vet school changed the direction of my veterinary career. The first was the musculoskeletal course where I realized that my initial plan of becoming an orthopedic surgeon was unlikely to occur. I realized that the complex repair of bones or purposefully breaking bones was not really for me! However, I was then lucky to begin to working in the ICU. That’s where I discovered the challenges of critical care – both mentally and emotionally. I thrived as part of the team that cared for the critical patients who came in through the emergency room and readily embraced the challenge.
Pamela Lucas, DVM, DACVIM-Oncology
How do you go about helping ease the concerns of an upset client?
Many of my clients have concerns about quality of life for their pet with cancer. They are grieving the loss of the pet, even with just the cancer diagnosis. I feel having an open dialog, and stressing that I share their goals, helps most clients. I don’t dictate what “needs” to be done; I give the family options, so they can make informed decisions for the care of their beloved pet. I have lost three of my own pets to various cancers. Relating to clients on a personal level and sharing my loss helps clients feel we are a team in the fight against cancer.
How do you like to work with the primary care veterinarian?
I could not be an oncologist without primary care veterinarians. They are on the “front line” when it comes to diagnosis and providing options for families. We are a team, and I rely on the family veterinarian to provide the daily, weekly, monthly and annual care that I cannot give to my patients. The primary care veterinarian has a long, sometimes lifetime rapport with families, which provides invaluable information and aid for me, especially while we are guiding people through difficult times.
Tell us about a case that touched your heart and taught you something meaningful about yourself and your practice.
“Sadie” was a 10-year-old female spayed rat terrier mix who presented on emergency for pleural effusion leading to dyspnea while I was in private practice in South Carolina. She presented on a very cold day, just before Christmas. The owner just lost her mother suddenly to cancer, and Sadie was her late mother’s dog. Tests showed that Sadie had multiple splenic and liver masses in addition to her pleural effusion. Cytology of the masses was diagnostic for a metastatic sarcoma, and the fluid was consistent with sarcomatosis, which is rare in veterinary medicine. The owner felt that losing Sadie would be like losing her mom again, so we started therapy despite a guarded prognosis. Sadie had no response to chemotherapy initially, so we started her on tyrosine kinase inhibitors, even though it was not known whether it would be helpful. Within two weeks, Sadie’s pleural effusion dried. We then added doxorubicin chemotherapy.
Sadie’s cancer stabilized for over three years! We monitored her closely, and although she continued to have large masses in both the spleen and liver, she was happy and asymptomatic. Over the years, Sadie’s owner and I became close. She shared with me what Sadie meant to her, and she called Sadie her “miracle dog.” Sadie eventually passed from her cancer; the owner was ready and able to grieve both Sadie and her mom in a healthy manner. Sadie taught me to offer therapies and treatments to patients, as long as there is still quality of life, even when the odds seem stacked against us. I never know what will happen if we try a therapy. I always know what happens if we do nothing.
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|Mar 17||7PM||Doctor||Coughing Dog: Heart Disease, Tracheal Stents & Medical Management of Respiratory Conditions
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