Luis H. Tello, DVM, MS
Teamwork is essential and 'the name of the game'. Every member needs to know his or her assignment.
The most important step in treating thoracic patients (dogs and cats) is the initial assessment and examination. Thoracic trauma patients are always an emergency and your speed of action depends on how much distress is apparent.
In the ABCs, the respiratory system has our main attention:
1. Establishment of airway/oxygen
2. Breathing support/thoracic wall
3. Circulatory support/cardiovascular normality/pulse
The main sources for thorax trauma in dogs are: blunt trauma by vehicular accident; dog fights / bites specially the small dog-large dog lesions; mistreatment, kicks, punches and other type of blows; and penetrating wounds in domestic accidents or gun misuse (bullets, knives, etc.).
The main sources for thorax trauma in cats are penetrating injuries during or caused by: fights / bites; falls (high rise syndrome); vehicular accidents; and domestic accidents and intentional blows. In rural hunting areas, penetrating wounds due to shot guns are common in roaming cats. Blunt trauma can be related to: car accidents; falls from a height or high rise syndrome; kicks; penetrating trauma; bites or fights (small-large animal interactions); projectiles; and stabbing.
In a patient with severe or multiple trauma, initial assessment is made concurrent with other steps to stabilize the patient. Fluid therapy and shock treatment are initiated at the same time as the patient is being evaluated. A detailed history of the trauma incident may also provide vital clues.
The time lapse since the trauma occurred is important information that has to be asked of the owners. Many times, because of anxiety, the time lapse cannot be thoroughly determined. But, whenever possible, this is very useful data and can help with some of the actions to be taken.
The Physical Examination
A detailed inspection of the animal can reveal external, and some internal, injuries. Clipping the hair may facilitate visualization of bruises. Hypoxia and hemorrhage are two of the main causes of death among traumatized patients.
With every traumatized patient that presents in shock with no evidence of external bleeding, the possibility of third space accumulation of blood must be assessed and ruled out.
The physical evaluation must be done in an orderly fashion, always keeping in mind the ABC concepts: respiratory, cardiovascular, nervous, digestive and muscle/ skeletal systems.
Initial overall observation of the patient.
Superficial and deep.
Free fluid? gas? pain?
Decreased vesicular murmur, muffled or absent respiratory--heart sounds?
Draw blood for preliminary lab data: blood work and chemical panel, bladder catheterization: urine sample, rectal palpation: pain, fractures.
Rectal temperature, heart rate and respiratory rate, color of mucous membranes, capillary refill time and hydration status, pulse quality and rhythm, external bleeding assessment, skin integrity and lesions, level of consciousness (mentation).
Adequate ventilation, imbalance between ventilation and perfusion, upper airway disturbances, need tracheotomy? pneumothorax? Think about thoracocentesis, diagnosis or therapeutic, trauma or lung injuries? ruptured diaphragm? Hemo-, hydro- or chylothorax? Does any lesion require immediate surgery?
Any external, visible hemorrhage? Any hypovolemic or shock signs? Arterial blood pressure, pulse oximetry, rhythm and pulse characteristics, cardiac auscultation, cenous distention? IV catheter placement and open IV pathway, replace any volume deficiency, colloid requirements? Does any lesion require immediate surgery?
Level of consciousness? Alert, ambulates, reflexes, unconscious, gait? Depressed, paretic, paraplegic?
Has the patient received any medication that may alter the examination? Any pathological changes in the central or peripheral nervous system? Does any lesion require immediate surgery?
Abdominal trauma can be a challenge to diagnose. Around half of serious lesions are mis-diagnosed in human patients. It is highly important to keep in mind the suspicion of abdominal trauma every time we deal with traumatized patients. Are there any signs of acute hemorrhage? Ruptured spleen? Other hemorrhage sources like kidneys, liver, mesenteric vessels? Abdominocentesis / diagnostic peritoneal lavage (DPL), Gl tract assessment. Abdominal viscera exploration (i.e., urinary bladder, ureters, gall bladder, pancreas): ultrasound scan, radiography. Possible peritonitis? Need for immediate exploratory laparotomy?
Muscle Skeleton System
Gait abnormalities or lameness. Any visible signs of open fracture or luxation? Joint exploration, tendon laceration or avulsion?
X-rays must be taken if possible before any centesis or DPL (diagnostic peritoneal lavage) is performed since these procedures may introduce air / fluid into the abdominal cavity. Plain or contrast studies? Ultrasound? CT scan or MRI? Do we always need such expensive studies?
Assess and palpate for thoracic movement and respiratory pattern. Rib fractures. Do we need to pain treatment? Flail chest? Support bandages? Penetrating wounds. Locate heartbeat.
Look for pain, evidence for free fluid or abdominal distention. Diagnostic peritoneal lavage more accurate (20 ml/kg of warm saline or lactated Ringers). Identify every palpable organ whenever possible, retroperitoneal space evaluation.
Spine and Appendages
Temperature of extremities, evaluate for fractures or luxations. Check for wounds or any evident deformity, retroperitoneal space can be involved in spinal and/or pelvic fractures.
Evaluate aptitude to stand up and walk. Position of the extremities and presence of paresis / paralysis. Flaccidity or rigidity, cranial and peripheral reflexes.
Head and Neck
Blood loss coming from the natural openings? Look after injuries in the head, eyes, ears, nose and nostrils. Check for pain and range of motion of the head, open the mouth and explore it for tongue or dental lesions. Remember palate fractures in high rise syndrome. Airway obstruction due to saliva and blood clots?
Specific Thoracic Approach
Surgical intervention tips:
Exploratory surgery is warranted in dogs with thoracic trauma when there is:
1. An open connection to the pleura or peritoneum;
2. Extensive flail chest;
3. Progressing emphysema of neck and chest;
4. Progressive pneumothorax;
5. Any signs of internal organ damage or uncontrollable hemorrhage; and
6. Pulmonary contusions that get worse despite treatment if there is no mechanical ventilation available.
It is possible that the major decision in the approach to small animal patient with thoracic trauma, is to recognize the real need for surgical intervention when most thoracic injuries can be appropriately managed with simple measures to correct hypoperfusion and hypoxemia. Emergency thoracotomy should be considered in every unstable patient who has the source of instability potentially corrected by surgery.
'Tap it before rad it': This is an 'almost always' rule. Most of the lesions should be diagnosed by needle thoracocentesis instead of chest radiograph. A simple technique, the procedure involves a butterfly catheter, 10 cc syringe and 3-way lock. Cats with respiratory effort because of thoracic trauma need very gentle management, and normally they refuse to adopt particular positions during a radiographic examination. Attempts to force them can cause the death of the cat.
The thorax should be carefully re-evaluated. If respiratory distress increases or the lung sounds are again diminished, thoracocentesis should be repeated. The need for repeated thoracocentesis, or the inability to reach a permanent relief for respiratory distress, are indications for chest tube placement.
The intense pain associated with the movement of fractured ribs may cause hypoventilation. Rib fractures are generally treated conservatively with pain management. A good alternative for local pain control can be achieved with inter-costal nerve anesthetic blocks.
This condition involves free communication between the pleural space and the atmosphere, through a chest wall. It can be life-threatening according of the size of the wound. Patients come into the clinic showing respiratory effort and a rapid, shallow restrictive respiratory pattern. Auscultation reveals muffled thorax sounds: heart and respiratory. Diagnosis should be based on thoracocentesis and suction of a variable amount of free air.
Pneumothorax results in an increased width of air-filled space in the pleural cavity. The most sensitive view is a horizontal-beam, laterally recumbent thoracic radiograph. On a recumbent lateral thoracic radiograph, the lungs collapse and retract from the chest wall and the heart usually appears to be elevated from the sternum.
This apparent elevation of the heart is not noticeable on a standing lateral radiograph. Partially collapsed or atelectic lung lobes appear radiopaque when compared to the air-filled pleural space. As the lungs collapse, the vascular pattern will not extend to the chest wall. This may be particularly noticeable in the caudal thorax on a ventrodorsal view. However, non-surgical management of an open pneumothorax usually results in a bad outcome. Postoperative pneumothorax or pleural effusion must then be prevented as they will result in separation of the parietal and visceral pleura, precluding adhesion formation.
Closed Pneumothorax (Tension Pneumothorax)
This lesion creates a one-way valve phenomenon in the lungs, and results when the chest wall is punctured or air leaks from a ruptured bronchus (or a perforated esophagus) and eventually ruptures into the pleural space. Normally this a self limiting condition and requires only supportive care such as oxygen and fluids.
Diagnosis and initial treatment should be done by thoracocentesis and fine needle gas aspiration. Further treatment need chest tube placement and a permanent air suction system.
If the thoracocentesis reveals the presence of blood in a considerable volume, the patient should be treated as hypovolemic and fluid infusion using crystalloids, colloids or blood products. Hemorrhage can originate from internal bleeding structures such as great vessels, or lungs, or from laceration of intercostals or internal thoracic arteries. Ultrasound instead of survey radiographs can provide a fast and reliable diagnosis in these patients. Such lesions are rare in dogs and cats in comparison with human beings.
Treatment of hemothorax depends on the volume of blood involved, the presence of hypotension and the flow of hemorrhage in the pleural space. Therefore, mild hemothorax that does not induce significant respiratory distress should be managed conservatively to allow reabsorption of pleural blood.
Animals with substantial blood loss from the pleural space may require a blood transfusion, in addition to colloid and crystalloid volume replacement, to maintain an adequate packed cell volume.
Autotransfusion of the blood removed by pleural drainage provides a fast and readily available source of compatible blood in patients with severe hemothorax. Aseptic collection and use of filters in blood bags are needed. In this case, exploratory thoracotomy is indicated in an attempt to repair the site of hemorrhage. Exploratory thoracotomy should be undertaken by a median sternotomy approach if bilateral bleeding is found.
Mortality in these patients used to be very high due to fast exsanguinations, hypovolemic shock and the lack of preparedness of the hospitals for these types of procedures.