2016 FALL: Bruised Lungs | Laryngeal Paralysis | Oxygen Therapy | Aspiration Pneumonia | Lights, Camera, Veterinarians | Meet Neurologist David Weinstein | Wanted: Diabetic Cats
The standard of care for patients suffering significant trauma, such as being hit by a car, is to take thoracic radiographs checking for internal injuries. In humans, 25 to 30% of individuals suffering trauma to the chest have been reported to demonstrate pulmonary contusions. The estimated mortality in these same individuals resulting directly from these pulmonary contusions is 15 to 40%. Pets are also at risk for lung injury. It has been reported that up to 44% of pets hit by cars presenting for fractures also have pulmonary contusions.
A contusion is a mechanical injury which results in hemorrhage. Contusion of the lungs, i.e. pulmonary contusions, can result from direct trauma to the lungs (think penetrating wound) or from blunt trauma to the chest wall. Blunt trauma to the chest wall induces pressure changes within the airways as the thoracic wall quickly contracts and expands. The resulting shock wave travels through the lung tissues causing overlying alveolar tissue to shear away from denser underlying supportive tissues. Compression of the lungs from blunt trauma also causes the air filled alveoli to burst like balloons.
The severity of pulmonary contusions frequently progresses over hours to days as an inflammatory reaction to the injury develops. Blood from damaged capillaries immediately fills the airways and alveoli. Later protein rich fluid leaks into the airways as inflammatory cells and chemical mediators alter vascular permeability. Loss of surfactant within the alveoli causes them to collapse. The elasticity and compliance of the affected lung regions becomes compromised.
Radiographs typically demonstrate a patchy or diffuse alveolar and interstitial lung pattern. Radiographs may need to be repeated to monitor the progress of the condition.
Signs of pulmonary contusions can vary from mild to severe. Many patients may be asymptomatic on presentation only to have signs of respiratory compromise progress over several hours. It can take up to 72 hours to determine the full extent of the respiratory compromise in chest trauma patients.
The diagnosis of pulmonary contusions is based on the patient’s history or physical signs of trauma, clinical evidence for respiratory compromise or hypoxemia, and thoracic radiographic findings.
Signs of pulmonary contusion:
- Increased respiratory effort
- Mental dullness
- Open mouth breathing
The first goal of treating pulmonary contusions is to stabilize the patient.
- Patients demonstrating shock should receive IV fluids in smaller measured increments until the perfusion goals of normalizing blood pressure and volume are achieved. Take care not to over-infuse the patient or the excessive intra-vascular perfusion pressure and volume could contribute to further fluid leakage into the lungs. Patient monitoring should include pulse quality, mucus membrane color, capillary refill time, blood pressure measurement, patient mentation and strength.
- Oxygen therapy is required by most patients with moderate to severe pulmonary contusions. Oxygen can be supplemented via flow-by techniques, oxygen cages, oxygen hoods or placement of a nasal oxygen catheter. The more severely compromised patients will benefit from positive pressure ventilation. Oxygen is blown into the lungs to open the airways and alveoli. This typically requires placement of an intratracheal catheter or endotracheal intubation. Those patients who cannot adequately ventilate on their own require mechanical ventilation. Pulse oximetry and/or blood gas analyses are recommended in these patients for monitoring.
- Analgesics will benefit patients when discomfort compromises their willingness to take deeper breaths.
Flow-by oxygen support may be necessary while the patient is first being evaluated.
How about diuretics, corticosteroids, or antibiotics?
Diuretics are not recommended. In studies, they have not been shown to reduce the severity of the pulmonary contusions and can lead to dehydration. Meanwhile, corticosteroids have not been shown to reduce the degree of inflammation when administered after an injury. Corticosteroids, by suppressing the immune response, could make the patient more susceptible to infection. Finally, antibiotics are not warranted unless a secondary infection (characterized by increased coughing and fever) develops.
What’s the prognosis?
The severity of the pulmonary lesions will determine whether the patient can survive. Hypoxemia typically becomes the limiting factor in the patient’s life. The more severely affected patients should be hospitalized in a setting where they can receive continuous oxygen therapy, supportive care, and monitoring.
Exercise intolerance; difficulty inspiring; voice changes; and a loud, raspy stridor or roar arising from the larynx, most obvious when a dog is panting, are just a few of the signs associated with laryngeal paralysis.
Laryngeal paralysis refers to the failure of the laryngeal arytenoid cartilages to reflexively open during inspiration, thereby obstructing upper airway flow. It typically occurs in middle-aged or older large-breed dogs, especially retrievers and hunting breeds. The condition is progressive, eventually leading to an inability to inspire.
The diagnosis of laryngeal paralysis requires a light general anesthetic to evaluate the movement of the arytenoid structures. The arytenoids fail to abduct, or open laterally, during inspiration.
Treatment of laryngeal paralysis is life-saving. A laryngeal tie-back procedure in which one of the obstructing arytenoids is sutured in a permanently open position, is typically recommended.
The obstruction to inspiration is immediately resolved. Most dogs are sent home the following day. Aspiration pneumonia, resulting from the loss of the protective function of the newly sutured arytenoid cartilage, is an uncommon side effect.
A loud roar or wheeze heard during inspiration are reasons to give one of our surgeons a call.
Can’t Catch your Breath?
Jeff Dennis, DVM, DACVIM
1. Blow-by: An oxygen source is held free flowing in front of the patient’s face. This is most useful for immediate administration. It can achieve oxygen concentrations in the immediate region of 35% using 5 L/min flow.
2. Elizabethan collar (e-collar) oxygen canopy: An oxygen source is taped to the inside of an e-collar that has been partially covered with cellophane wrap. This technique allows the patient some mobility and you have continued access to the patient for exams and treatments. It can achieve oxygen concentrations of 70% using 5 L/min flow. The upper 25% of the e-collar opening should be left uncovered to allow heat, moisture and CO2 to escape. The e-collar has to be big enough that the wrap does not contact the nose.
3. Conventional cage with plastic wrap covering the door: An oxygen source is taped to the inside of the cage. The top of the cage door should be left uncovered to allow heat, moisture and CO2 to escape. The cage allows the patient some mobility; however, access to the patient is limited because the oxygen within the cage dissipates as soon as the door is opened. It can achieve oxygen concentrations of 50% using 5 L/min.
4. Manufactured oxygen cage: Many of these cages have the ability to regulate not only the oxygen concentration within the cage but also the temperature and humidity. The cage allows the patient some mobility; however, access to the patient is limited because the oxygen within the cage dissipates as soon as the door is opened. Newer cages can achieve oxygen concentrations of 50% or higher.
5. Intranasal oxygen catheters: Catheters are placed into the patient’s nasal openings through which oxygen is delivered. This is the most effective and efficient means of delivering oxygen to the patient. This technique allows the patient some mobility, and you have access to the patient for exams and treatments. You can increase the concentration of oxygen inhaled by the patient by increasing the oxygen flow rate or utilizing two catheters, one for each nasal planum. The oxygen should be humidified.
6. Intra- or trans-tracheal catheters: A catheter or tube to deliver oxygen is passed into the trachea. This technique will provide the highest oxygen concentration in the inspired air; however, it can cause irritation and coughing. It is useful in patients with laryngeal dysfunction, and typically requires some degree of sedation. The oxygen should be humidified.
Some may suggest that the level of pain is the ultimate measure of a patient’s suffering. I disagree. The sensation of dyspnea has to be one of the worst symptoms a patient can experience. It may be my anthropomorphic assessment, but I believe patients with dyspnea look a lot more ‘scared’ then patients with pain. Effective treatments exist to relieve most pain, but relieving dyspnea is much more difficult. The lives of dyspneic patients are at risk. The options available to treat respiratory compromise are more limited than pain relief, yet pretty straightforward. Dyspneic patients need oxygen delivered to their alveoli.
The first purpose of oxygen supplementation is to restore oxygenation in animals with illnesses that increase oxygen demand or decrease oxygen delivery. Without adequate oxygenation of the tissues, energy production pathways in the body change from aerobic to anaerobic resulting in less energy (ATP) production for the cells to utilize and increased acid byproduct (lactic acid) production. Both the lack of ATP and the low pH of the environment cause dysfunction of cellular metabolic pathways leading to cell death. Organ function within the body becomes compromised.
The second purpose of oxygen supplementation is to decrease the ventilator and myocardial work necessary to maintain adequate oxygen delivery to the tissues. The body will recognize when oxygen concentrations needed to maintain cell health are low and trigger the respiratory and cardiac centers in the brain to stimulate deeper and more rapid respirations and cardiac contractions. The additional work induces energy stores to be used up faster, thereby weakening the body further.
What are some indications for oxygen therapy?
- Pulmonary disease (pneumonia, pulmonary contusions, thromboembolism)
- Airway disease (tracheal collapse, laryngeal paralysis, feline asthma)
- Pleural disease (pleural effusion, pneumothorax, diaphragmatic hernia)
- Heart and vascular compromise (congestive heart failure, pulmonary edema, shock)
- Cerebral injury (trauma)
- Hypoventilation (anesthetic recovery, chest wall compromise, neurologic or mental depression)
- Increased oxygen demand by the tissues due to high metabolic demands (hypothermia, hyperthermia, sepsis)
Did you know? Some oxygen facts
- Ambient room air has an oxygen concentration of 20%.
- Oxygen concentrations exceeding 50% for more than 24 hours can damage the lungs.
- Therapeutic oxygen should be humidified when supplementation is required for more than a few hours or if nasal or tracheal catheterization is used.
- Oxygen concentrations delivered by anesthetic machines approach 100%.
- The larger the chamber to be filled with oxygen, the longer it takes to displace the ambient air contained within the chamber with oxygen.
Methods of assessing patient oxygenation
- Clinical signs
- Open mouth breathing
- Extended head and neck
- Restlessness or unwillingness to lie down
- Dark mucous membranes
- Mental dullness
- Rapid and deep respirations
- General weakness
- Pulse oximetry
- Arterial blood gas analysis
How to create an Elizabethan collar oxygen canopy
An e-collar oxygen canopy is a quick, easy, economical, low stress technique for delivering oxygen to a patient. High oxygen concentrations can be achieved within the canopy very quickly. The patient is not ‘trapped within a cage’ providing you easy access to the patient for evaluation and treatment. To create an e-collar canopy:
- Choose an e-collar big enough that the patient’s nose won’t reach the outside edge.
- Cover the front of the e-collar with cellophane wrap leaving 25% open at the top for heated expired air to rise and escape.
- Tape the oxygen tube inside the bottom of the e-collar. The oxygen source should not be humidified.
- Place the e-collar on the patient fixing it so it won’t spin.
How to place intranasal oxygen catheters
Intranasal catheters are easy to place, economical, and they don’t inhibit access to the patient for evaluation and treatment. By delivering oxygen directly to the larynx where it is inhaled, it is one of the best techniques available to oxygenate a patient. You can double the oxygen concentration that is inhaled by doubling the oxygen flow rate or utilizing two nasal catheters at the same time.
To place an intranasal catheter:
- Use the largest red rubber catheter that you feel you can comfortably place into the nose. The larger the catheter, the less the resistance to oxygen flow.
- Pre-measure the red rubber catheter from the corner of the eye to the tip of the nose and mark with a pen.
- You can pre-bend the catheter by gently heating it with a match or lighter at the mark which helps to prevent the catheter from backing out. Be careful not to melt the catheter.
- Drip topical anesthetic into the nasal opening.
- Feed the catheter tip through the nares opening and then ventro-medially.
- Advance the catheter to the mark or bend.
- Fix the outside of the catheter in place with a skin staple placed just lateral to the nasal planum. Suturing or stapling the catheter through butterflied tape applied to the catheter is a convenient method for securing the catheter to the nose and face and preventing it from sliding.
- Apply an e-collar to prevent the patient from removing the catheter.
- Attach the catheter end to a humidified oxygen source.
BluePearl Veterinary Partners provides oxygen therapy 24/7 to patients in need of such support in our ICU ward. Patients are continually monitored under the watchful eyes of our technicians and clinicians providing vital time for their underlying conditions to be diagnosed and treated. If you feel your patient might benefit from oxygen therapy, please give us a call.
Aspiration pneumonia occurs when oropharyngeal, gastric, or foreign material is inhaled into the lower airways. The inhaled substance can compromise normal pulmonary function by causing mechanical obstruction of the airways, inducing bronchoconstriction, chemically damaging the airway walls, and introducing bacteria into the lower airways. If the damage is severe enough, the animal will be presented for evaluation.
Aspiration pneumonia is most often a complication of vomiting and therefore secondary to another disease. It is a risk for dogs with megaesophagus and is of concern for patients who are undergoing or recovering from general anesthesia or sedation. Patients who are being force fed are also at risk for aspirating.
The diagnosis of aspiration pneumonia is formulated from the patient’s clinical history, signs, lab results and radiographic findings. The history may include such details as excessive vomiting, chronic regurgitation, generalized musculoskeletal weakness, or a recent episode of anesthesia. Most patients present with acute dyspnea, fever, coughing and lethargy. Lab tests may or may not reveal a leukocytosis. Patients typically demonstrate low oxygen saturation levels on pulse oximetry as well.
Thoracic radiographs are the most important diagnostic tool for diagnosing aspiration pneumonia. Two-view thoracic radiographs commonly demonstrate patchy alveolar consolidation and air bronchograms involving the ventral aspect of the left cranial and right middle lung lobes. The bronchus leading to the right middle lung lobe branches off of the trachea ahead of and ventral to the other bronchi, making it the most likely site for aspiration pneumonia. Pulmonary disease involving the caudal and dorsal lung fields are much less likely to be associated with aspiration and should prompt the clinician to search for another disease process. Radiographic evidence of aspiration pneumonia may not be evident for up to 24 hours after the aspiration has occurred. Therefore, the lack of radiographic evidence does not initially exclude aspiration in a respiratory patient.
Aspiration pneumonia is a life-threatening disease that requires immediate medical attention. Initial treatment should include basic balanced IV fluid therapy and oxygen support. Placement of single or double nasal oxygen catheters are the most efficient means of raising blood oxygen concentrations. Additional treatments include antibiotic administration, pulmonary coupage and nebulization. Antibiotics are best chosen based on bacterial culture results procured from a transtracheal wash, bronchoalveolar lavage, or fine needle aspiration of the lungs. However, these procedures are frequently bypassed because of the patient’s severe respiratory compromise. It can take several days for the pneumonia to respond to therapy. Respiratory rate, respiratory pattern, pulse oximetry and radiographs are all used to document clinical improvement or worsening in aspiration patients.
Aspiration pneumonia can lead to sepsis, acute respiratory distress syndrome, and even multiple organ failure. Those patients that have aspiration pneumonia are often at risk of getting it again if the underlying condition has not resolved. Therefore, the underlying condition which contributed to the patient’s aspiration must also be diagnosed and treated. The prognosis for a patient with aspiration pneumonia is guarded. Milder cases in which the underlying cause can be identified and treated carry a more favorable prognosis.
FROM THE MEDICAL DIRECTOR
Veterinarians Are But Actors
If all the world is not a stage, then certainly the exam room is. Are we not all actors, initially reading off of our scripts and then improvising to the words, expressions and actions of our clients and our patients? As I try to read the client’s intentions my suggestions change, my expressions of empathy change, my phrasing changes, even my goals for the visit change. As actors we should look at exam room visits as one act plays. And like the best of improvisational plays, you can’t predict where the story will lead. You only hope the client claps at its end.
Jeff Dennis, DVM, DACVIM
Meet our specialist…
David Weinstein, DVM, DACVIM-Neurology
David Weinstein, DVM, DACVIM-Neurology
Dr. David Weinstein is excited to be settling down in a new home here in the Midwest where his veterinary training started. A graduate of Kansas State, he subsequently completed a small animal internship in New York City and then a neurology internship in Atlanta. Having now finished residency training and completing the credentialing process, we are happy to welcome him to BluePearl in Kansas City as a full-time, board-certified specialist in veterinary neurology. David is joined by his school teacher wife, their young son and a crazy, some may even say psycho dog. We were able to distract David from attending to his seizuring and paretic patients for a few minutes to get his responses to a few questions:
What is the last book you read?
“Shelter” by Harlan Coben. I enjoyed it because it was suspenseful.
What was your first job?
I was a veterinary assistant in a primary care practice in New Jersey. After a couple of days, I knew this would be my future profession.
How do you unwind at the end of the day?
By watching TV with my family, especially sports, and taking my crazy, totally untrained golden doodle for walks
What is in your refrigerator right now?
Lots of leftovers from area restaurants. We do not cook and go out to eat most nights of the week.
What keeps you up at night?
My wife’s snoring…. but don’t tell her
WANTED- Diabetic Cats
For a fully-funded clinical study to evaluate an investigational oral medication for the treatment of feline diabetes mellitus
To qualify, cats must meet all of these criteria:
- Newly diagnosed cats or cats treated with insulin or oral anti-diabetic drugs for 250 mg/dL at screening
- Either glucosuria OR serum fructosamine ≥ 400 μmol/L
- Persistence of at least one clinical sign consistent with diabetes mellitus (lethargy, polyuria, polydipsia, polyphagia, weight loss and/or plantigrade posture of hind legs (DM polyneuropathy))
- Cats must otherwise be in general good health.
Owners must be able to present their cats for up to six visits over a 2-month period for examination and blood and urine sampling. All study-required tests and evaluations, as well as the investigational medication, will be provided to owners at no charge.
For more information or to enroll you client and patient in this study:
Please contact Beth Rogers (firstname.lastname@example.org) or Dr. Jeff Dennis (email@example.com) at 913.642.9563.