THE MERCK VETERINARY MANUAL
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Trauma in Emergency Medicine

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Diagnostic and therapeutic efforts in emergency situations can be directed by the nature of the trauma. Blunt trauma is commonly associated with thoracic and abdominal bleeding, organ rupture, fractures, and neurologic injuries. Penetrating trauma is typically localized to the path of the penetrating object, which is rarely a straight line. Falling from a height causes long bone and facial bone fractures as well as thoracic and abdominal injuries. A dog bitten by a larger dog can have deep-penetrating bite wounds, spinal injuries, major abdominal and thoracic trauma (even without penetrating wounds), and tracheal rupture from the shearing forces sustained during thrashing motions. Resuscitation of the airway, breathing, and circulation; control of hemorrhage; and pain relief are followed by a careful evaluation of the nervous system, chest, abdomen, integument, and musculoskeletal system.

The traumatized animal should be approached as if multiple injuries are present. The neck and spine should be immobilized until a thorough examination for spinal fractures or luxations is made. Thoracic auscultation for cardiac arrhythmias and the presence and quality of lung sounds should be done to identify chest injuries. The abdomen should be palpated for pain, fluid, or hernias. Extremity fractures should be supported by bandages or splinted to prevent further injury. Significant swelling may indicate ongoing hemorrhage. Because many internal injuries may not be apparent for a significant amount of time after the initial trauma occurs (12–48 hr), close monitoring is essential to allow early detection of potentially life-threatening problems. An animal that appears normal and stable on initial examination may have substantial underlying injury, making monitoring of at least physical examination parameters in the hospital (eg, respiratory and heart rates, mucous membrane color, and mentation) appropriate.

Initial diagnostic evaluation should include the minimum database before fluids are administered, if possible. Point-of-care tests should minimally include a PCV, total solids, BUN test strip, and blood glucose. When hemorrhage first occurs, the peripheral blood PCV may be normal or even increased with a normal or decreased relative total protein level; this is a clinical indication of hemorrhagic shock in dogs and occurs because of splenic contraction. This release of RBCs into circulation may occur faster than interstitial to intravascular fluid shifts; therefore, serial PCV and total solid measurements should be monitored after trauma. Both PCV and total solids will decrease as hemorrhage and subsequent crystalloid/colloid resuscitation continues. An extended initial database includes arterial or venous blood gases, electrolyte panel, blood lactate, and prothrombin time/partial thromboplastin time. This baseline information is used to create the initial treatment plan and to provide the baseline for subsequent monitoring. Ionized hypercalcemia has been associated with a poorer prognosis after trauma and may warrant more intensive monitoring. Survey lateral radiographs of the chest and abdomen at presentation can demonstrate the initial changes resulting from thoracic and abdominal trauma. Orthogonal views should be performed as the animal's condition dictates. Ultrasound examination of the abdominal and thoracic cavities may provide additional information about internal injuries and can often be performed while fluid resuscitation is initiated.

Some scoring systems have been developed for trauma, such as the animal trauma triage score; this system assigns a number from 0 (slight or no injury) to 3 (severe injury) in the following categories: perfusion, cardiac, respiratory, eye-muscle-integument, skeletal, and neurologic. In one study assessing >200 dogs evaluated after vehicular trauma, dogs that died or were euthanized had signficantly higher scores (median 6) than those that survived (median 2); higher scores were also associated with higher cost of care.

Thoracic Trauma

Pulmonary contusions, pneumothorax, cardiac arrhythmias, pleural hemorrhage, pericardial hemorrhage, rib fractures, flail chest, and diaphragmatic hernia are some of the potentially life-threatening complications that must be considered in thoracic trauma. Oxygen supplementation and analgesics allow careful physical examination. An ECG, thoracic radiographs, blood gas analysis, and diagnostic or therapeutic centesis help determine the extent and severity of the problems.

Severe pulmonary contusions cause hypoxemia, labored breathing in a pattern consistent with parenchymal disease, and crackles and rales on pulmonary auscultation. If the animal does not improve with supplemental oxygen, pain medications, and fluid therapy, then tracheal intubation and positive-pressure ventilation with 100% oxygen are indicated. The airway should be suctioned to evacuate blood and debris that are obstructing the flow of air.

Labored breathing with asynchronous movement of the chest and abdomen and dull or quiet lung sounds is consistent with pleural air or fluid and warrants immediate thoracocentesis. Thoracocentesis should be performed before taking radiographs in animals with respiratory distress, because animals may struggle and decompensate while radiographs are being taken; assessment with ultrasound may be less stressful but should not delay therapy. When a negative pressure cannot be achieved, repeated thoracocentesis or continuous drainage of the pleural space by chest tube is required. Large quantities of whole blood removed on thoracocentesis or ongoing leakage of air after 72 hr of pleural drainage are indications for surgical exploration of the chest. Large volumes of blood aspirated during a centesis may be collected into an IV bag or blood transfusion bag, because they may be used for autologous blood transfusion.

The thoracic-focused assessment with sonography technique (TFAST) can help diagnose pneumothorax, hemothorax, or thoracic wall trauma and provides an alternative to radiographs when performed by a skilled sonographer familiar with ultrasonographic changes associated with these injuries. The chest cavity should be palpated for rib fractures with displaced bone, flail segments, avulsion of ribs, torn intercostal muscles, and herniations. When flail segments impair ventilation, the segment is stabilized by securing it to an external frame or cast, formed to the shape of the chest. Penetrating bite wounds over the chest should be explored under anesthesia for debridement and drain placement; if the wound is penetrating, the thorax may be surgically entered to inspect damage to underlying tissue, repair or debride that tissue as necessary, lavage the thoracic cavity, and place a thoracostomy tube before closure.

As the animal's condition allows, thoracic radiographs (two or three views) should be performed to assess for injury to the lungs. Many of the above-listed injuries may show up on routine radiographs; however, radiographic evidence of pulmonary contusions may not appear until 12–24 hr after the initial injury.

The heart should be ausculted and an ECG evaluated for arrhythmias. Arrhythmias may not be present at the time of injury but develop 12–48 hr after the event as myocardial contusions and hypoxemia affect the cardiac conduction system. Common arrhythmias seen after thoracic trauma include sinus tachycardia, ventricular premature contractions, and ventricular tachycardia. Treatment with lidocaine or other antiarrhythmic medications is warranted if the arrhythmias impair perfusion, if the rate is rapid and sustained (>180 bpm in dogs), if ventricular premature contractions are multiform, or if there are prefibrillatory rhythms (R on T phenomenon, torsades de pointes, ventricular flutter).

Abdominal Trauma

The extent and severity of abdominal injuries are often not initially apparent, unless there is visceral herniation outside the body cavity. The abdominal surface should be examined closely for evidence of bruising, abrasions, lacerations, protrusions, localized swelling, herniations, distention, and pain. Animals with evidence of abdominal pain that are in shock are considered to have intra-abdominal hemorrhage until proved otherwise. Rupture or laceration of the spleen or liver are the most common sources of intra-abdominal hemorrhage. However, all abdominal organs are susceptible to the shearing forces from blunt trauma. Other common sources of abdominal bleeding include avulsed mesenteric vessels, damaged muscle, or avulsion of the kidneys in the retroperitoneal space.

Approximately 40 mL/kg (just less than half of the circulating blood volume) is necessary before free blood in the abdominal cavity will be evident by palpation or visual inspection; this volume is associated with signs of poor perfusion (shock). Smaller volumes of abdominal fluid may be apparent with radiographs, abdominocentesis, or ultrasound of the abdomen. Abdominal distention from hemorrhage may become apparent if aggressive fluid resuscitation increases blood pressure and disrupts one or more blood clots that provided hemostasis. Small volume fluid resuscitation to achieve a low-normal blood pressure endpoint (90 mmHg systolic) is indicated to avoid sudden increases in arterial or venous pressures. When ongoing abdominal hemorrhage is confirmed, hindlimb and abdominal binding (see Hindlimb and Abdominal Binding) is indicated early to reduce the amount of hemorrhage until hemostasis is accomplished.

After injury of any abdominal organ, clinical signs of organ dysfunction or hollow viscus rupture typically develop over a period of hours but may be longer or shorter depending on the nature of the injury. Acute abdominal pain is a key physical finding. Survey abdominal radiographs can demonstrate organ displacement, distention, rotation, or free abdominal gas or fluid. Fluid can be recovered by four-quadrant abdominocentesis. Using the focused assessment with sonography technique (FAST, see Hemostasis), even small amounts of free fluid in the abdomen can be identified and aspirated using ultrasound guidance.

When free fluid is not readily identified, a diagnostic peritoneal lavage can be done. A fenestrated catheter is placed into the peritoneal space, and warm isotonic saline (20 mL/kg) is infused into the abdomen. The fluid is allowed to dwell for several minutes and distribute throughout the abdomen; it is then drained and evaluated.

Clear fluid indicates that the possibility of significant abdominal hemorrhage is minimal. Fluid with a 1% PCV indicates mild abdominal hemorrhage, whereas fluid with a PCV >5% indicates significant abdominal hemorrhage that warrants careful monitoring.

Fluid obtained from the abdomen should be examined cytologically for evidence of WBCs, plant or meat fibers, and free or intracellular bacteria. Biochemical evaluation for creatinine and potassium, bilirubin, amylase, and phosphorus help identify urinary system rupture, gallbladder rupture, pancreatic injury, or ischemic bowel, respectively. Abdominal fluid glucose 20 mg/dL or more below peripheral blood glucose is characteristic of a septic peritonitis and warrants exploratory surgery. The abdominocentesis, peritoneal lavage, or FAST ultrasound scan can be repeated in several hours if fluid from the first assessment did not indicate a significant problem but the clinical signs continue or progress. Retroperitoneal, fascial, or intramuscular (body wall) hemorrhage or hemorrhage into the GI system can be more challenging to identify.

Criteria for emergency exploratory laparotomy include ongoing hemorrhage; inability to stabilize shock; organ rotation, entrapment, or ischemia; diaphragmatic hernia; and evidence of organ rupture or peritonitis. Some simple bladder ruptures may be amenable to medical management and placement of a urinary catheter. Surgery to repair a diaphragmatic hernia should not be delayed, particularly with gastric displacement into the thoracic cavity, respiratory compromise, or ongoing hemorrhage.

Retroperitoneal, severe fascial compartment hemorrhage (associated with pelvic fractures), or hemorrhage into a hollow viscus is suspected in acutely traumatized animals that still have signs of a declining PCV/total solids, nonresponsive hemorrhagic shock, and no significant findings on abdominocentesis, peritoneal lavage, or FAST scan. Radiographs typically show expansion and loss of detail in the retroperitoneal space. An IV pyelogram should be done to help delineate disruption in the renal vascular supply or in the retroperitoneal portion of the ureter before proceeding with exploratory surgery in this situation.

Last full review/revision October 2013 by Andrew Linklater, DVM, DACVECC

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