Presenting problem: Trauma in Ferrets

Introduction

Ferrets are small, flexible, mischievous, and curious. This combination means that traumatic injury is a common problem, particularly when owners do not supervise their pets or “ferret proof” their living quarters. For instance, reclining chairs have been implicated in the deaths of many ferrets (Brown 2007). Ferrets may also be accidentally stepped on or become trapped within a confined space.

Trauma can result in a constellation of injuries that may affect the head, thorax, abdomen, spine, and limbs.

Head trauma may involve:
  • Eye injury
  • Skull fracture
  • Dental injury
  • Traumatic brain injury

Secondary brain injury, mediated by excitatory neurotransmitters and inflammatory mediators, occurs hours to days after the initial event. Secondary brain injury results in edema, ischemia, increased intracranial pressure, and decreased cerebral perfusion (Macintire 2006).

Thoracic injuries are common in any patient suffering from significant trauma, and multiple chest injuries may be found in one individual.

Thoracic injuries may include:
  • Pulmonary contusions
  • Pneumothorax
  • Hemothorax
  • Rib fractures
  • Diaphragmatic hernia
  • Myocardial contusions

Pulmonary contusions frequently occur following blunt chest trauma. Contusions consist of interstitial and alveolar hemorrhage accompanied by parenchymal destruction. This hemorrhage begins immediately after the injury, but can worsen within 24-48 hours (Serrano 2009).

Abdominal injuries may include:
  • Abdominal wall rupture
  • Hemoabdomen (hemoperitoneum)
  • Hemothorax
  • Hemoretroperitoneum
  • Uroabdomen (uroperitoneum)

Splenomegaly is a very common finding in the ferret, therefore the risk of splenic laceration or rupture may be higher in ferrets. Uroabdomen or uroretroperitoneum may develop secondary to urinary bladder rupture, or trauma to the urethra or ureter (Weisse 2002).

Spinal trauma may include vertebral fracture, luxation or subluxation. Although intervertebral disc extrusion is rare but possible in the flexible ferret, however mechanical injury to the spinal cord can lead to compression, laceration or vascular disruption of the cord. Secondary injury occurs as seen in head trauma. Myelomalacia may develop as inflammatory mediators travel in central gray matter (Macintire 2006). Pelvic or limb fractures, luxations and tendon or ligament injuries may also be incurred.

 

Signalment

Traumatic injury may be seen in all ages, but is most common in young ferrets less than 3 years of age.

 

History

Traumatic injury is rarely a subtle presentation, and owners typically report a specific incident. Also consider trauma when owners do not “ferret proof” their home , supervise their ferrets, or when owners allow ferrets free run of the home.

 

Physical examination

“A Crash Plan”

Assume the injured ferret is painful and may nip. Scruff the patient as needed and proceed gently and carefully. Muzzle during assessment if need be but beware of compromising respirations. Cover external wounds until they can be managed, and wrap the ferret to conserve heat.

Traumatic injury in the provide provides a good opportunity to follow the mnemonic “A Crash Plan” during the physical examination:

Potential causes of pelvic limb paresis, ataxia, or paralysis in the ferret:

Airway: Is the airway patent?
If there is respiratory noise or if the patient is stuporous, pull the tongue forward and gently and carefully extend the head and neck. Remove any debris obstructing the airway, using suction and a laryngoscope if need be.
Cardiovascular: Is there evidence of cardiac function?
Check the heart rate and rhythm.
Are heart sounds muffled?
Palpate pulses. What is pulse quality? Is pulse synchronous with the heartbeat?
Is there hemorrhage? Apply firm steady pressure to prevent further blood loss.
What is the capillary refill time? What is blood pressure?Signs of shock:

  • Depression
  • Pallor
  • Prolonged capillary refill time
  • Poor pulse quality
  • Tachycardia

Suspect hemoabdomen in when shock is recognized without obvious signs of blood loss.

Respiratory: Is the animal breathing? Are the gums pink?
What is the respiratory rate and pattern?
Is there respiratory noise?
Is the animal orthopneic? Is there other evidence of respiratory distress?
Is there increased respiratory effort?Auscult the chest bilaterally.
Palpate the neck, sides of the chest, and the dorsal neck region for evidence of tracheal displacement, subcutaneous emphysema, or rib fractures (Ford 2006).
Abdomen: Palpate the abdomen.
Is there pain? Penetrating injury? Fluid wave? Mass lesion?
Reddening around umbilicus can suggest intra-abdominal hemorrhage.
Many ferrets are thinly furred on the ventrum, but clip fur overlying the abdomen if need be to examine the patient for bruising or penetrating wounds.Auscult the abdomen for borborygmus.
In cats, blunt abdominal trauma causes 59.1% of uroabdomen cases. The cause of urine leakage being a ruptured bladder in 84.6% of cases (Aumann 1998). Affected patients may also be dehydrated or hypoproteinemic (Macintire 2006). Animals with uroabdomen will often present with hematuria before signs of uroabdomen are apparent (Culp 2009). Voiding may be normal in affected animals, and the absence of clinical signs does not rule out urethral tear.Possible signs of urethral trauma

  • Dysuria
  • Hematuria
  • Pain, swelling
  • Ascites
  • Discoloration of skin in perineal region
Spine: Palpate the spinal vertebrae, checking for pain, swelling, or asymmetry.
Evaluate the toe pinch as well as spinal reflexes
Secondary spinal trauma may develop within 24-48 hours. Clinical signs of myelomalacia may include fever, progressive loss of sensation and motor function. Death from respiratory paralysis may occur within 3-7 days (Macintire 2006).
Head Examine the eyes-ear-nose-throat for evidence of head trauma.Look for evidence of head trauma:

  • Epistaxis
  • Blood of cerebrospinal fluid in ear canal
  • Head tilt, nystagmus, strabismus
  • Reduced level of consciousness
  • Evidence of reduced mental activity, obtunded
  • Anisocoria
  • Slow or absent pupillary light reflex
  • Reduced or absent menace or palpebral reflexes
Pelvis Evaluate the pelvis.
Examine perineal and rectal areas, including external genitalia.
Be sure to check anal tone and tail tone as well.
Limbs Examine the limbs for evidence of fracture or luxation.
Arteries
Nerves: The initial neurologic examination should focus on the patient’s level of consciousness, posture, pupil size and symmetry (Fletcher 2009).

Secondary survey

Secondary survey of the patient should include a complete physical exam once life-threatening cardiopulmonary problems have been addressed. A more complete neurologic exam should evaluate peripheral nerves for motor and sensory input and output to limbs and tail, cranial nerve reflexes including menace, blink, gag, and the oculovestibular reflex, as well as assessment of jaw tone. Stain the corneas with fluorescein in all case of head trauma (Ford 2006).

Evidence of increased intracranial pressure (ICP)
  • Cushing response*
  • Deterioration of mental status
  • Dilated, non-responsive pupils
  • Loss of physiologic nystagmus
  • Decerebrate posturing (unconsciousness, rigidity of all four limbs)

*The Cushing or vasopressor response is the most specific indirect marker of increased ICP that includes (1) widening pulse pressure, (2) irregular breathing patterns, and (3) bradycardia.

If rectal examination is indicated, sedation and small fingers are needed in the ferret.

 

Differential diagnoses

Owners typically report a traumatic incident, but remember that pre-existing illness is common in middle-aged to older ferrets. Concurrent disease like insulinoma, Helicobacter gastritis, and cardiovascular disease may manifest with the stress of trauma.

 

Diagnostics

Assuming the ferret has undergo major trauma, initial testing should include:

  • Packed cell volume/total protein
  • Blood glucose
  • Blood urea nitrogen
  • Urine specific gravity
  • Electrocardiogram
  • Blood pressure: In small animals, the target mean arterial pressure (MAP) is 80 mmHg. If only systolic blood pressure is available, 100 mg is considered equivalent (Jasani 2011).
  • Pulse oximetry: Oxygen saturation (SpO2) on room air greater than 95% is satisfactory (Jasani 2011).

Ancillary testing performed as soon as possible may include:

  • Complete blood count
  • Peripheral blood smear to evaluate platelet count and cell morphology
  • Urinalysis
  • Whole body or chest/abdomen survey radiographsTake radiographs once the patient is more stable and can tolerate positioning. Determine technique and gather all supplies together before placing the patient on the x-ray table. Provide oxygen supplementation as needed. Stabilize the spine during transport by securing the ferret to a small, rigid board. Be aware that radiographic signs of pulmonary contusions may lag 24 hours behind clinical signs (Jasani 2011). Skull radiographs are an insensitive test. Where available, CT or MRI is preferable for patients with traumatic brain injury (Fletcher 2009).
  • Arterial blood gas
  • Biochemistry panel including electrolytes.
  • Coagulation parameters

Extensive testing may be necessary to fully assess the status of a patient suffering from abdominal trauma. Additional tests that may be indicated include:

  • Abdominocentesis and abdominal fluid analysis
  • Intravenous urogram
  • Abdominal ultrasonography

Any ferret with confirmed pelvic fractures should be thoroughly evaluated for additional injuries since it takes considerable external force to fracture the pelvis.

 

Therapy

Initial stabilization with resuscitation fluids:

  • Address extra-cranial life-threatening injuries immediately. For systemic hypotension caused by hypovolemic or hemorrhagic shock, establish vascular or intraosseous access and begin resuscitation measures. Start with 1/4th of the dog shock dose (22 ml/kg/h) or use the cat shock dose of 44 ml/kg/h. Administer isotonic crystalloid fluids, or give colloids if pulmonary contusions are suspected or if there is an inadequate response to crystalloids. Monitor your small patient carefully to avoid hypervolemia, as this will increase intracranial pressure. Administer fluids conservatively once hypovolemia has been corrected.
  • Correct electrolyte abnormalities, especially hyperkalemia, in patients with uroabdomen.
  • Provide animals that are hypoxemic or hypoventilating with supplemental oxygen. Also address any problems that may interfere with normal respirations such as pneumothorax.

Conservative versus surgical management

  • Conservative management may sometimes be selected for conditions such as hemoabdomen. Provide cage rest and place an abdominal bandage, which has been shown to stabilize MAP and improve survival rates (McAnulty 1986).
  • The decision to perform surgery is case-dependent, however surgery is often needed to correct severe abdominal trauma. Additional supportive care may be required before surgery. Also identify any anesthetic risks that are evident.

Thoracic injury
Pneumothorax:

  • Thoracocentesis is not required for cases of pneumothorax. Air may be resorbed over days to weeks. Thoracocentesis should be performed when pneumothorax appears to be compromising respiration in a clinically significant way.

Hemothorax:

  • Clinically significant hemothorax is rare; blood is resorbed over several days
  • If thoracocentesis is performed, remove as small a volume as possible (20 ml/kg) to prevent subsequent anemia (Jasani 2011).

Pulmonary contusions: There is no specific treatment, however management typically includes oxygen supplementation, cage rest, and analgesia as needed for concurrent chest wall injuries. Severe cases may require ventilatory support (Serrano).

  • The incidence of bacterial pneumonia subsequent to pulmonary contusions is low, and empirical use of antibiotics is not recommended.
  • Administer fluid therapy cautiously being careful not to overhydrate or cause hypervolemia.
  • Clinical signs caused typically resolve within 2-7 (sometimes 10) days unless pneumonia develops (Jasani 2011; Serranof 2009).

Rib fractures or flail chest are often diagnosed radiographically:

  • No specific therapy is usually required.
  • Rib fractures are painful, so analgesia is often indicated.

Management of traumatic brain injury

Although prognosis varies, even patients with severe deficits can recover with aggressive supportive care.

  • Medical therapy for cerebral edema relies upon mannitol or hypertonic saline. Mannitol is effective in treating intracranial hypertension, but can interfere with cerebral perfusion if intravascular volume is not replaced promptly. Hypertonic saline is less likely to lead to hypovolemia and decreased cerebral perfusion (Table 1).
  • Supplemental oxygen is indicated in all head trauma patients to limit hypoxic neuronal injury (Macintire 2006). Use oxygen supplementation to maintain SpO2 above 95%. Intubate and ventilate if SpO2 below 90% where possible (Jasani 2011).
  • Promote venous drainage from the brain to prevent or reduce intracranial hypertension. Keep the head elevated 15-30 degrees above horizontal, and minimize jugular compression. Avoid jugular venipuncture and restraining the patient around the neck.
  • Minimize increases in cerebral metabolism. Administer anticonvulsants as needed, and sedate if the ferret if it is distressed and flailing although most traumatized ferrets tend to lie quietly and listlessly (Table 1).
Table 1. Drug therapy for traumatic brain injury
Medication Dosage Route Freq Comments
Buprenorphine 0.01-0.05 mg/kg SC, IM, IV q8-12h
Butorphanol 0.1-0.5 mg/kg SC, IM, IV q4-6h
Diazepam 1-2 mg/kg IM Tranquilization, seizure control
1 mg/animal IV Seizure control
0.5-1.0 mg/kg CRI
Hypertonic saline IV
Mannitol 0.5-1.0 mg/kg IV Administer over 20 min
SC: subcutaneous; IM: intramuscular; IV: intravenous; CRI: constant rate infusion; q: every; h: hour

Corticosteroid use is still appears in some literature on traumatic brain injury, but the research suggests their use is of no value and may actually have a detrimental effect on patient outcome. The Brain Trauma Foundation recommends steroids not be given to patients with traumatic brain injury.

 

Spinal trauma

  • Cage rest ferrets with spinal trauma for at least 4-6 weeks.
  • As with brain injury, the use of corticosteroids is controversial with spinal trauma, but may be most effective if given within 2 hours of injury (Macintire 2006).

Soft tissue or orthopedic injury

  • Cover wounds with a temporary bandage to reduce the risk of nosocomial infection.
  • Immobilize fractures or luxations with a temporary splint to prevent further damage and to help control pain.
  • Handle all injuries gently and carefully, and always evaluate peripheral nerve function and pulses before placing the bandaging.

Analgesia

  • Opioids are a good choice for orthopedic pain and they produce minimal cardiopulmonary depression.
  • Utilize multimodal techniques by also administering local or non-steroidal analgesia.

Nutritional support

  • Tempt the ferret to eat as soon as it is stabilized. Injuries such as severe brain trauma can increase caloric requirements by 2-2.5 fold.
  • Avoid syringe-feeding patients with severe head trauma as there is an increased risk for aspiration as well as exacerbation of the injury. An esophagostomy tube is indicated in such patients once they are strong enough for general anesthesia.

Nursing care

  • Handle patients gently, taking care to minimizing their stress by being calm and quiet.
  • Although ferrets are small and relatively lightweight, they can develop decubital ulcers so provide them with thick, dry, well-padded bedding. Turn the patient regularly every 2-4 hours.
  • Provide gastroprotectants, like H2-blockers and/or sucralfate, especially when corticosteroids are given. The high incidence of subclinical Helicobacter gastritis in ferrets means that gastroprotection is often beneficial in the ferret that has suffered serious trauma. The stress associated with the traumatic event can lead to clinical gastritis with bruxism, anorexia, ptyalism, pawing at the mouth, and/or vomiting.
  • If the patient is unconscious or stuporous, lubricate the eyes every 4-8 hours to prevent corneal drying and ulceration.
  • Provide appropriate bladder management by gently expressing the bladder every 4-8 hours.
  • Gentle, careful, passive range-of-motion physical therapy every 8-12 hours will also prove helpful for long-term management unless there is spinal injury.

Monitoring

Victims of serious trauma should be monitored closely. For instance, clinical signs with pulmonary contusions may progress over several hours (Serrano 2009). Ferrets with
traumatic brain injury must be watched closely for development of seizure activity,
bradycardia (which can signal an increase in intracranial pressure), and respiratory distress caused by neurogenic pulmonary edema.

Animals that do not respond to initial resuscitation or that begin to decline usually have severe ongoing or preexisting physiologic disturbances (Ford 2006).

Clinical signs of decompensation:
  • Weak peripheral pulse
  • Cool peripheral extremities
  • Cyanosis, gray, or pale mucous membranes
  • Prolonged capillary refill time
  • Hypothermia (hyperthermia)
  • Confused or inappropriate mentation, depression
  • Tachycardia, bradycardia, arrhythmia*
  • Declining hematocrit
  • Distended, painful abdomen
  • Increased respiratory effort, dyspnea
  • Hematochezia, hematemesis

*Remember that a prominent sinus arrhythmia is common in the normal ferret.

 

There are many potential causes of decompensation including acute renal failure or respiratory failure, bowel or organ rupture, cardiac arrhythmias, edema, hemorrhage, coagulopathy, multi-organ dysfunction, pulmonary thromboembolism, sepsis, and systemic inflammatory responses.

References