Trauma is a common reason for dogs and cats to present to veterinary practices.

Trauma is defined as any physical injury as a result of an external force, such as blunt trauma (that is, road traffic collisions or falls from a height) or penetrating injury (that is, gunshot or bite wounds)¹. They can produce mild injuries or affect multiple organ systems, and be severe and life-threatening.

Most trauma patients (72.3%) are admitted due to polytraumatisms², hence a thorough evaluation and global approach are essential to improve patient outcome. With appropriate management in referral hospitals prognosis is usually good, and survival to discharge is reported in around 90% of dogs³ and 76% of cats⁴.

Triage

Before presentation to hospital, owners can already institute first aid measures when required and telephone advice should be provided. Profuse bleeding can be stopped with a pressure bandage. Large open wounds should be covered with a clean cloth. Non-ambulatory patients should be secured in a lateral position, and patients showing breathing difficulty can benefit from being kept in sternal recumbency.

If penetrating objects are present, owners should not remove them, but should ensure that the object will not penetrate further or cause additional damage during transport by securing it⁵.

As with any kind of emergency, a primary survey following ABC (airway, breathing and circulation) should be performed.

Airway should be assessed for patency and, if necessary, intubation and positive pressure ventilation initiated. Oxygen supplementation should be provided in any animal with respiratory distress by mask or flow-by.

Respiratory function can be evaluated subjectively, assessing respiratory rate and effort, and thoracic auscultation. Oxygenation can be further evaluated via arterial blood gas analysis or oxygen saturation (pulse oximetry). Inverse or asynchronous breathing pattern, or dull lung sounds on auscultation should raise the suspicion of pleural space disease or diaphragmatic hernia⁶. Crackles, coughing and/or blood in the mouth without evidence of facial trauma can be suggestive of pulmonary contusions.

Point-of-care ultrasound (POCUS) is used for early detection of potential life-threatening conditions. POCUS of the thorax can help diagnose pleural effusion, pneumothorax (absence of glide sign), pulmonary contusions (increased number of B-lines) or diaphragmatic rupture (abdominal viscera within the thoracic cavity)⁷. It also allows evaluation of presence of pericardial effusion⁸, assessment of cardiac chamber size and heart contractility.

POCUS of the abdomen is used to detect peritoneal and retroperitoneal effusion, and to evaluate the integrity of the urinary bladder and gall bladder. Serial assessments of both thorax and abdomen are recommended to monitor progression and to detect abnormalities that may not be evident on initial evaluation.

Initial assessment of the cardiovascular system aims to evaluate the evidence of shock. Pale mucous membranes, prolonged capillary refill time, tachycardia (or bradycardia in cats or late decompensated shock in dogs), weak or bounding peripheral pulses and hypotension are indicators of poor tissue perfusion or decreased cardiac output.

Blood pressure should be measured directly or indirectly via Doppler or oscillometric techniques. However, a normal blood pressure measurement does not imply good tissue perfusion.

Diagnosis

After ABC evaluation, venous access should be obtained and a blood sample taken for minimum database, including PCV, total protein (TP), lactate, blood glucose and electrolytes. Further investigations include haematology and blood smear interpretation, serum biochemistry and venous blood gas analysis. Coagulation testing, and viscoelastic testing if available (thromboelastography), are also indicated for evaluation and aid in the diagnosis of acute traumatic coagulopathy.

In patients with acute haemorrhage, PCV and TP are both usually low as a consequence of dilution effect produced by fluid shift from interstitial space and IV fluid therapy. Nevertheless, both can be normal if assessed during the initial stages, or PCV can be normal or high due to splenic contraction – especially in dogs.

Haemorrhage can be external or internal –  internal bleeding can occur within the pleural space, peritoneal or retroperitoneal spaces, or gastrointestinal tract, or around long bones after fracturing. High blood lactate and acidaemia are usually seen as a consequence of poor tissue oxygenation and anaerobic metabolism.

ECG is indicated to detect possible arrhythmias, which can occur secondary to myocardial contusion, with ventricular tachycardia and ventricular premature contractions being the most commonly reported^9-11.

Abdominocentesis should be performed if abdominal free fluid is present. Cytological examination and measurement of PCV, total solids (TS), creatinine, potassium and total bilirubin of the effusion should be performed. In active or recent bleeding, PCV and TS of the effusion should reflect the PCV and TS of the peripheral blood.

Uroabdomen is confirmed when an effusion-to-serum creatinine concentration is greater than 2.0, and an effusion-to-serum potassium greater than 1.9 in cats and greater than 1.4 in dogs^12,13. The presence of bile pigments on cytological examination or a total bilirubin in effusion that is at least twice the total bilirubin in serum confirms bile peritonitis¹⁴. Presence of suppurative inflammation with intracellular bacteria is indicative of septic peritonitis.

Thoracic injuries are common in polytraumatised patients. Pulmonary contusions and pneumothorax are the most frequent injuries, although haemothorax, rib fractures, flail chest and diaphragmatic rupture can also occur.

Radiography should be delayed until the patient is stable for further investigation of intrathoracic, abdominal and musculoskeletal injuries. Potential pulmonary lesions may not be seen initially as radiographic changes can take up to 24 hours to appear^15,16. In patients with severe polytrauma, full-body CT scan can be considered as it may provide a more accurate assessment of all injuries and can be helpful for planning of surgical intervention¹⁷.

Full neurological examination should be performed to evaluate the presence of traumatic brain injury (TBI) or spinal cord damage. Movement of these animals should be restricted until spinal cord injury can be excluded. Serial neurological examinations are necessary to evaluate progression of clinical signs and response to therapy.

The Modified Glasgow Coma Scale can be used in head trauma cases to assess prognosis. Total score ranges from 3 to 18, with lower scores being associated with more severe injury and non-survival^18,19.

The urinary system can also be affected; therefore, renal function parameters and urinary output should be monitored. Azotaemia and hyperkalaemia raise the suspicion of urinary tract rupture¹². Abdominal ultrasound, urinary contrast studies and/or CT can be used if urinary tract rupture is suspected to determine the site of rupture.

Finally, a complete orthopaedic examination and evaluation for external wounds should be performed, as multiple parts of the body may be affected². A rectal examination and palpation of the pelvic canal help to evaluate for fractures, instability and evidence of frank haemorrhage. Penetrating wounds may appear externally as mild injuries, but they should be assessed thoroughly as they can result in significant internal organ injury, and when necessary, surgical exploration must be performed after patient stabilisation.

The Animal Trauma Triage (ATT) score can be used to classify the degree of trauma. Total score ranges from 0 to 18. Animals with higher ATT scores are less likely to survive compared to animals with lower scores; however, this should not be used to withdraw treatment – rather to increase monitoring and level of intervention as it shows the patient has suffered a more severe degree of trauma^18,19.

Continued monitoring of these patients is essential and owners should be aware that despite apparent stability at initial presentation, complications may arise days to months after trauma.

Treatment

The initial goal in the management of trauma patients is to restore tissue perfusion and oxygen delivery. If hypovolaemia is suspected, fluid resuscitation with IV boluses of balanced isotonic crystalloid solution (10ml/kg to 20ml/kg over 10 to 20 minutes) should be administered.

Improvement of mentation, perfusion parameters, blood pressure and minimum database can help determine the need of additional fluid administration.

In haemorrhagic shock, a conservative resuscitation strategy, also known as “hypotensive resuscitation”, is currently recommended. This strategy aims to restore a lower-than-normal systolic blood pressure (approximately 80mmHg to 90mmHg, to ensure a mean arterial pressure of more than 65mmHg), which would restore perfusion, but would also reduce the risk of re-bleeding, avoiding blood clot dislodgement and reducing the degree of haemodilution. However, this strategy should be avoided in patients with head trauma^20-22.

In terms of type of fluid therapy, several considerations exist when treating patients with haemorrhagic shock.

Although synthetic colloids can still be considered an option, they have been associated with complications such as acute kidney injury and coagulopathy; therefore, its use is not recommended in these patients^23-27.

Administration of hypertonic saline during fluid resuscitation (3ml/kg to 5ml/kg bolus over 5 to 10 minutes) can be especially beneficial in patients with hypotension and TBI due to its simultaneous effects of expanding intravascular volume and reducing intracranial pressure²². Resuscitation with blood products would be ideal due to multiple reasons, including the increase of intravascular volume, increase of oxygen carrying capacity and reversal of coagulopathy if present, as well as avoiding haemodilution^28-31.

The requirement for transfusion of red blood cells is based on clinical evidence of hypoperfusion and whether ongoing bleeding is present, rather than on a specific PCV value³². It should be considered in anaemic patients or patients with haemorrhagic shock that present with tachycardia, hypotension, weak or bounding pulses, altered mentation and/or tachypnoea.

If shock is not responsive to fluid therapy, other causes should be investigated and ruled out, such as ongoing haemorrhage requiring surgical intervention, cardiogenic shock due to arrhythmias, or obstructive shock due to pericardial effusion or tension pneumothorax.

Thoracocentesis may be life‑saving in severely dyspnoeic patients with pleural space disease. In animals with pleural effusion, thoracocentesis should only be performed in case of severe respiratory distress, as haemothorax usually resolves spontaneously³³.

Haemoabdomen after blunt trauma usually results from liver or spleen bleeding. If the haemorrhage is mild or does not progress, surgery will likely not be required². Conversely, surgical intervention is warranted in cases of continued abdominal bleeding non-responsive to medical management, abdominal wall penetration or hernia, diaphragmatic rupture, urinary bladder rupture, septic peritonitis or bile peritonitis.

Should the patient require any kind of surgical procedure, it should be delayed until the animal is haemodynamically stable to minimise complications during general anaesthesia.

Wounds should be kept clean, moist and protected until further evaluation and definitive treatment can be performed. They should be clipped, cleaned aseptically and covered with a sterile dressing. Bleeding wounds should be addressed by application of direct pressure and ligation of exposed vessels if necessary. Limb fractures should be temporary immobilised with a soft padded bandage⁵.

In patients with TBI, therapeutic considerations include:

• ensuring adequate cerebral perfusion by maintaining an appropriate systemic blood pressure
• adequate blood oxygen saturation, administering oxygen supplementation when necessary
• reduce intracranial pressure by administration of mannitol (0.5g/kg to 1g/kg IV over 20 to 30 minutes) or hypertonic saline (3ml/kg to 5ml/kg IV over 5 to 10 minutes) and keeping the head elevated 15° to 30°
• avoiding jugular sampling
• avoiding tight collars or wraps over the neck
• avoiding sneezing, coughing and vomiting

Analgesia will depend on severity of trauma. IV full mu agonist opioids, such as fentanyl or methadone, are most commonly used. As part of a multimodal analgesia, other drugs such as paracetamol, ketamine or lidocaine can be added according to patient requirements; however, paracetamol and lidocaine are contraindicated in cats. NSAIDs should be avoided initially, as these patients may be hypotensive and/or hypovolemic^34-37.

Finally, acute traumatic coagulopathy is a syndrome that can occur in trauma patients and may contribute to ongoing blood loss. The early use of antifibrinolytics, such as tranexamic acid (10mg/kg to 15mg/kg every eight hours), appear to be beneficial as they can prevent clot dissolution and additional haemorrhage, and have a good safety margin^38-42.

Referral options

Trauma cases include a very wide range of clinical presentations and, therefore, every case should be managed according to severity – varying from mild cases, which can be treated as outpatients, to polytrauma cases with multiple systems affected that will require critical care and specialised treatment.

Severe cases – such as patients suffering with TBI or spinal cord damage, unresponsive haemorrhagic shock, thoracic or abdominal wall penetration or hernia, urinary tract rupture and septic or bile peritonitis – have a higher risk of complications, which can lead to systemic inflammatory response syndrome, sepsis and multiple organ dysfunction. Therefore, patients with confirmed or suspected severe injuries can be referred for optimal care.

• Some drugs mentioned in this article are used under the cascade.