2016 SPRING: Local Analgesia | Osurnia | Is It Lymphoma? | Tracheal Collapse | CPR | Surgical Wound Healing Complications | Clinical Trials | Continuing Education
Indications for Local Analgesia
Local analgesia is an underused technique that can greatly enhance the overall analgesia in a patient; lead to use of less systemic drugs; and may be used in situations in which sedation, heavy systemic analgesia or anesthesia is contraindicated. Many animals that present to emergency are in shock, and those that are not in decompensated shock may be in compensated shock. Those in compensated shock are able to compensate because their sympathetic nervous system is maintaining their blood pressure and helping to maintain their oxygen delivery. In the intensive care unit, critically ill animals are dynamic with potentially minute-to-minute changes in cardiac output, blood pressure and oxygen delivery.
Almost all sedatives, analgesics and anesthetics blunt the sympathetic nervous system to some extent. This effect puts animals in the emergency department and critical care unit at risk for decompensation when receiving systemic drugs for analgesia, sedation or anesthesia. Local analgesic techniques may aid in decreasing systemic drug requirements in these patients.
Although shock patients in general are at risk for systemic decompensation with systemic sedatives and anesthetics, there are specific conditions in which these drugs should be particularly avoided or delayed if at all possible. Specific examples include head trauma, pulmonary contusions, pneumothorax, myocardial contusions (and subsequent arrhythmias), diaphragmatic hernia, liver fractures, splenic fractures, urinary tract rupture, severe anemia/hypoproteinemia and neurologic abnormalities. Avoidance of anesthesia and sedation in these cases is beneficial for the reasons indicated:
- Arrythmias: can be worsened or induced
- Head trauma: can alter blood flow to the brain and worsen trauma/neurologic status
- Liver/spleen fractures: Can cause intraoperative hemorrhage and hypotension
- Lungs with pulmonary contusions: more prone to atelectasis and subsequent hypoxemia
- Pneumothorax: can be worsened with positive pressure ventilation
- Urinary tract injuries: can cause severe life-threatening electrolyte disturbances (especially hyperkalemia)
In addition, many anesthetic drugs are protein-bound and become more bioavailable in animals that are acidemic, a common consequence of shock and trauma. Avoidance of anesthesia until full assessment and proper resuscitation is attained is critical. However, sometimes sedation or anesthesia in these cases cannot be avoided. Use of local analgesic techniques in these life-threatening situations frequently decreases the need for systemic drug use and makes for a safer overall procedure.
Because local anesthetics directly block nerve impulses, they decrease pain in an alternative way compared with systemic analgesics. When used preemptively, this decreases the likelihood of wind-up of the pain pathways, ultimately helps prevent hyperalgesia, and aids in the multimodal approach to patient analgesia.
Drug selection is an important part of the local anesthetic protocol. Most local anesthetics function by blocking nerve impulses. At a cellular level this occurs by blocking sodium channels in the nerve membrane. When sodium is blocked, the nerve cannot conduct an impulse, and therefore no sensation can be transmitted. Local anesthetics cause analgesia but can also cause complete loss of motor function depending on the properties of the drug, location and myelination of the nerve; or the dose and size of the nerve fibers. Generally, local anesthetics cause nerve blockade in a particular order by first numbing pain, then warmth, touch, deep pressure and finally motor function. However, large peripheral nerves are an exception to this and tend to have motor blockade before sensory blockade, as well as cause proximal extremity analgesia prior to distal extremity blockade. Local anesthetic drugs differ in their side effects, onset of action and duration of action. Consideration of these drug factors should influence drug selection.
For questions regarding the use of local analgesics at our BluePearl hospitals, feel free to call and speak to any of our specialists in Brandon, Clearwater, Tampa or Sarasota.
|Lidocaine||1-2 mg/kg||Short-acting analgesia for local infiltration, intrapleural and intraperitoneal blocks, and occasionally epidural use|
|Bupivicaine||1-2 mg/kg||Longer-acting analgesia for local infiltration, intrapleural, intraperitoneal and epidural use.|
|Dexmedetomidine||0.001-0.005 mg/kg||Epidural, intraarticular, or perineurally|
|Preservative-free morphine||0.1 mg/kg||Epidural|
We would like to thank our colleague from BluePearl in Utah, Vicki L. Campbell, DVM, DACVECC, DACVAA, for allowing us to use this article for Companion.
Osurnia: A New Product for a Challenging Problem
Many of us cringe when our clients present their dog for ear problems. The discomfort associated with ear conditions can make infected and inflamed ears both difficult to examine and to clean. Our owners face the same challenge when we ask them to clean and medicate their pet’s ears at home, so it’s no wonder many ear conditions don’t resolve and eventually become chronic problems. Because of their pet’s extreme discomfort, owner compliance with our treatment recommendations may not be realistic. And who can blame owners for their failure? Ears are hard to treat.
There may be a solution. Elanco Animal Health has developed a product, Osurnia®, to help us treat what some owners consider untreatable. Osurnia gel comes in a single-use tube. The product contains florfenicol (which is similar to chloramphenicol) to treat bacteria, terbinafine to treat yeast, and betamethasone to reduce inflammation. Its advantage is its two-dose treatment regimen. The medication is squeezed into the ear canal and massaged to spread the formulation. This is repeated 7 days later. That’s it. The infrequent dosing is a tremendous advantage when it comes to owner compliance. Another advantage is that to ensure the medication remains in contact with the ear canal surface, the ear should not be cleaned between uses or prior to the second administration.
According to the product label, Osurnia has not yet been evaluated in dogs with perforated ear drums, and therefore should be avoided in these patients. Vomiting was an infrequent adverse effect noted during clinical trials as was an elevation in the ALP value (probably secondary to the corticosteroid). Osurnia is not approved for use in cats.
Osurnia would be expected to be very effective for curing simple otitis. The recurrence of ear disease would suggest the need to identify and address an underlying cause. Should you have a pet with recurrent and/or poorly responsive disease, further evaluation by a dermatologist is suggested.
Is It Lymphoma?
We have all had patients in whom we suspect lymphoma, based on our exam and clinical assessment, only to have the cytology or biopsy results come back inconclusive or suggesting inflammation. This may be the result of poor sampling on our part, the presence of concurrent lymph node abnormalities such as inflammation or necrosis, or even a reflection of a less advanced stage or grade of disease. What now? We could pull out our old trusty corticosteroid, but if the patient actually has lymphoma, we might be doing more harm than good. Studies and clinical experience have suggested that treatment of lymphoma with corticosteroids alone will induce changes in the lymphoma cells making them less responsive to other chemotherapeutic agents when the final diagnosis of lymphoma becomes apparent.
So what other options do we have when cytology or biopsy samples are inconclusive?
If the cytology or biopsy results are inconclusive despite the suspicion for lymphoma, then the pathologist may suggest you perform a PARR, or PCR for antigen receptor rearrangement. Flow cytometry and immunohistochemistry/immunocytochemistry are additional tests that might be useful for both supporting the presence of lymphoma as well as determining the lineage of lymphoma.
How does PARR work?
PARR can be useful for differentiating neoplastic lymphocytes from normal lymphocytes whether they are retrieved from pleural effusion or an enlarged lymph node. Cancer cells are basically clones of a single cell. PCR amplification of the cellular DNA (responsible for encoding for the antigen receptors on the cell surface) within the lymphocytes is performed to determine if the DNA is derived from a single clone (same gene length and sequence) or is derived from multiple cell lines (variable and multiple gene lengths and sequences typical of normal immune responses). PARR testing can be performed on both cytology and biopsy samples.
Varying with the lab, PARR is reported to have a sensitivity of up to 90% in dogs, i.e. 90% of dogs with lymphoma will be correctly identified. PARR is less useful in cats where it is reported to have a sensitivity of only 65%. PARR is reported to have a specificity in both dogs and cats of approximate 92%, i.e. 8% of pets without lymphoma will be falsely positive. Much like any testing, the results of the PARR test should be used in conjunction with your other test results when formulating a final diagnosis.
What is flow cytometry?
Studies indicate that lymphoma cells, due to their clonal expansion, typically demonstrate identical antigen receptors. By comparison, normal lymphocytes demonstrate a huge variety of antigen receptors. To perform flow cytometry, live cells, such as those retrieved from lymph node aspirates, are injected into a vial of the patient’s serum or saline. Fluorescent-labeled antibodies which bind to proteins present on the cell surface of the lymphocytes are then added to the fluid. The labeled lymphocytes are run through the laser light of a flow cytometer producing a ‘scattergram’ which is used to determine whether the cells are homogeneous (typical of lymphoma) or heterogeneous. Because B- and T-cell type lymphomas express different surface antigens, the test is also useful for differentiating B- and T-cell types of lymphoma.
How about immunochemistry?
Immunocytochemistry and immunohistochemistry utilize special stains applied to cytology and histopath slides to identify cell markers that are typical for various types of cancers. The testing is useful for differentiating B- and T-cell lymphomas, mast cell tumors, melanomas, carcinomas and sarcomas. Further studies may find immunohistochemistry, as well as flow cytometry, useful for identifying the presence of specific proteins or other cell markers which may be associated with multidrug resistance, rate of cell division or other factors useful for predicting prognosis or the best treatment protocol.
Drs. Coyle and Kane see oncology appointments at our hospitals in Brandon, Clearwater and Tampa and are available for phone consults.
Tracheal Collapse: Diagnosis and Treatment
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. 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.
Tony Ishak, DVM, DACVIM-SAIM, DACVIM-Cardiology, is available to take your calls regarding tracheal stenting and can be reached at our hospital in Tampa.
We would like to thank our colleague from BluePearl in Tennessee, Carly Waugh, DVM, DACVIM, for allowing us to use this article in Companion.
Cardiopulmonary resuscitation (CPR) was originally developed over 50 years ago. Despite five decades of research, neurologically intact survival following cardiac arrest remains poor. Less than 6% of dogs and cats that experience cardiopulmonary arrest in the hospital survive to hospital discharge. However, positive outcomes are possible when appropriate measures are taken quickly and performed appropriately. Recently the American College of Veterinary Emergency and Critical Care published new guidelines for CPR in companion animals. These guidelines, collectively called the Reassessment Campaign on Veterinary Resuscitation (RECOVER), were published in a special issue of the Journal of Veterinary Emergency and Critical Care in June 2012. These guidelines were the culmination of many years of work and represent the closest thing to a “standard of care” for veterinary CPR that we have.
Basic Life Support
Basic life support involves the early recognition of cardiac arrest, administration of chest compressions, airway management and provision of ventilation. CPR should be administered to any non-responsive apneic animal. It is not necessary to auscult for a heart beat or palpate for pulses as this unnecessarily prolongs administration of CPR. In cats and small breed dogs, chest compressions should be administered directly over the heart. In medium and large breed dogs, chest compressions should be administered over the widest portion of the chest. For all animals, chest compressions should be administered at a rate of 100-120 compressions per minute. An airway should be obtained quickly in all patients undergoing cardiac arrest if possible. Ventilation should be administered at a rate of 10 breaths per minute. Ideally, a capnograph should be used to monitor any patient undergoing cardiac arrest as both hypoventilation and hyperventilation may negatively affect outcome.
Advanced Life Support
Advanced life support encompasses all components of veterinary CPR after initiation of basic life support until return of spontaneous circulation. This may include vasopressors, positive inotropes, anticholinergics, prompt defibrillation and correction of acid-base disturbances and volume deficits. Reversal of any sedative or anesthetic drugs should also be performed. Detailed information is available in the RECOVER guidelines.
Animals that achieve return of spontaneous circulation should be hospitalized in a 24-hour critical care facility for ongoing post-resuscitation care.
The entire RECOVER guidelines were published in the June 2012 issue of the Journal of Veterinary Emergency and Critical Care. This special issue is available online for no charge at www.veccs.org. If you would like more information regarding CPR, we would be happy to give you and your staff an in-clinic demonstration.
Common Complications in Surgical Wound Healing
Surgical wound repair is one of the most common procedures performed in veterinary medicine. Despite its routine nature there are still multiple complications that can arise. Here are some tips for the most common issues.
Excessive skin tension will result in dehiscence of the surgical wound. It is key that tension be placed on the subcutaneous tissue and not the skin. There are multiple tension relieving techniques that can be used to decrease tension including undermining, walking sutures, and different types of mattress sutures.
Infections of surgical wounds are not uncommon especially if dealing with an initially contaminated wound. Ideally, these wounds should be cultured because a large portion will have resistant infections, particularly if they have been in the hospital environment multiple times. Also, do not be in a rush to reclose an area that opens with infection. Most of these cases will heal with the appropriate antibiotic therapy and bandage care. However, if you try to close over an actively infected wound it will likely dehisce again, and as multiple surgeries are performed in the area the blood supply will be diminished. Judicious use of drains in these situations can also be beneficial. On average, allow at least 3-5 days to make the wound a healthier environment before closing. Typically, the surgeons at BluePearl only place drains in large pockets, keeping in mind the importance of treating drains as sterilely as possible as they are another source of potential contamination.
Most wound healing complications can be resolved with relatively conservative treatment. However, there are some situations in which more aggressive treatment needs to be applied. Our surgeons are available to discuss management of such cases.
Feline Anemia Trial
Our hospitals in Tampa and Brandon are currently recruiting patients for a fully-funded trial to evaluate the safety and efficacy of an oral medication to manage anemia associated with chronic kidney disease in cats. The study consists of two phases: the efficacy phase (28 days) and the maintenance phase (8 weeks).
- Cats, > 1 year old, male or female, > 2.0 kg
- Not pregnant, lactating or intended for breeding
- Diagnosis of chronic kidney disease
- Non-regenerative anemia with PCV < 27% at study days -7 and 0
- Stable concurrent medical conditions (i.e., heart disease, hyperthyroidism)
- Cats may be receiving SQ fluids
- Fractious cats
- Positive urine culture on study day -7
- Systolic blood pressure > 165 mmHg on study days -7 or 0
- Previous treatment with erythrocyte stimulating agents (ESA), including erythropoietin (EPO)
- Previous blood transfusion since being diagnosed with CKD
- Severe clinical signs of inflammation not attributed to CKD
- Other significant uncontrolled medical issues (i.e. lymphosarcoma, symptomatic pancreatitis etc.)
- FeLV+ or FIV+ (if not vaccinated, sponsor will cover the cost to test)
- Obvious signs of GI bleeding
The study medication, diagnostic lab work, and examinations will be provided at no cost to owners. Owners will be expected to administer the study medication at home, keep an owner diary, and comply with study protocols.
*Note that this study is not funded for diagnostic or treatment costs associated with the underlying renal disease. Those costs must still be assumed by the owner.
For more information or if you have a patient who may meet the above requirements, please contact any member of the BluePearl internal medicine team in Tampa or Brandon.
Canine Stage II Splenic Hemangiosarcoma Trial
This study will evaluate the effects of Yunnan Baiyao as a single agent or combined with a polysaccharopeptide on disease control and survival time in dogs with splenic hemangiosarcoma not receiving a standard chemotherapy protocol.
This study, selected for funding as a winner in a juried, national competition, is being underwritten by Frankie’s Friends charitable pet foundation.
Participants will receive the following:
- Free supply of Yunnan Baiyao during study enrollment
- Free recheck appointments every 6 weeks
- Free restaging tests (blood work, thoracic radiographs, abdominal ultrasound) every 12 weeks
The following pets may be considered for enrollment in the study:
- Postop splenectomy (within 2-3 weeks of procedure)
- Histologic diagnosis of hemangiosarcoma
- No detectable gross metastatic disease at the time of surgery based on thoracic radiographs, ultrasound, gross appearance of liver and surrounding abdominal organs at surgery, and/or liver biopsy
- No chemotherapy (i.e. doxorubicin or metronomic) was administered
Continuing Education: Come learn with us!
BluePearl is strongly committed to the veterinary community. One of the ways we demonstrate this commitment is through our continuing education program, which is subsidized in part by our Partners in Education. Please check our online calendar regularly for the most current information about courses, dates and locations.