Clinical Suite: Traumatic Brain Injury

Head trauma consists of both primary and secondary brain injuries. Are you prepared to combat the ensuing complications?

Overview

Pamela Fettig, DVM, DACVECC, Oradell Animal Hospital, Paramus, New Jersey

Traumatic brain injury (TBI) can occur in up to 25% of dogs following severe blunt trauma.¹ Head trauma cases are caused by vehicular accidents, purposeful harm, penetrating wounds, crush injury, falls from heights, and other traumas.²

Figure 1

Blood flow to the brain. Blue line = PaO2; red line = mean arterial blood pressure (MAP); and gray line = PaCO2. The normal brain has the ability to maintain cerebral blood flow (CBF) despite any changes in cerebral perfusion pressure (CPP). This is caused by pressure and by chemical autoregulation, which prevents under- and overperfusion of the brain. A  MAP or CPP between 50 mmHg and 150 mmHg helps maintain adequate CBF. Outside this range, blood flow becomes linear with MAP. PaO2 and PaCO2 can change the diameter of vessels and affect blood flow to the brain. This autoregulation is lost after head trauma.3,10

Common head trauma injuries include^3,4:

• Concussion: A brief loss of consciousness with no underlying histopathologic lesion.

• Contusion: Bruising of the brain associated with hemorrhage and edema.

• Coup and contrecoup lesions: At the site of impact and in the opposite brain hemisphere, respectively.

• Lacerations: Disruption of the brain parenchyma—the most severe injury.

• Hematomas: Several types can occur within the brain parenchyma (axial) or outside the brain (extraaxial) in the subarachnoid, epidural, or subdural sites. Any type of bleeding or hematoma formation can lead to increased intracranial pressure (ICP).

Head trauma consists of primary and secondary brain injuries. Primary injury (eg, fracture, hemorrhage) is the physical disruption of intracranial structures at the time of the event. Secondary injury, which can occur minutes to days following the TBI, is associated with a massive release of excitatory neurotransmitters and decreased availability of adenosine triphosphate (ATP), the energy required by all cells, which leads to cellular and cerebral edema.^5,6 Cerebral cells with low energy availability induce concurrent overproduction of oxygen free radicals, leading to further cell death.^5-7

Severely increased ICP can ultimately impair blood flow to the brain (see Figure 1), leading to increased cerebral CO₂; the subsequent sympathetic nervous system response to increase blood pressure in an effort to restore cerebral blood flow (CBF) can lead to reflex bradycardia (Cushing reflex).^6,7 Hypercapnia can induce vasodilation and increase ICP; hypocapnia can induce vasoconstriction with subsequent cerebral ischemia. Pain and agitation can increase ICP.^6,7

Treatment Plan

Pamela Fettig, DVM, DACVECC, Oradell Animal Hospital, Paramus, New Jersey

Focus assessment on the ABCs (ie, airway, breathing, circulation)  and amelioration of shock. Correction of hypotension, hypoxemia, and either hypercapnia or hypocapnia is primary.⁶ Once shock resuscitation and extracranial stabilization have occurred, repeated assessment using the Modified Glasgow Coma Scale can indicate survival probability and response to therapy^6-8 (see Figure 2). Avoid worsening other orthopedic injuries.

Extracranial Therapy

• Fluids: Rapidly restore normal extracellular fluid volume and composition to ensure adequate CPP with isotonic saline (in the absence of significant sodium derangements or other electrolyte disturbances) and/or artificial colloids.^4,6,7

• Oxygen: Aim for PaO₂ of 80 to 100 mmHg or SpO₂ of 94% to 98%; avoid hyperoxemia.⁷

• Ventilation: Aim for low normal values for PvCO₂ of 40 to 45 mmHg and PaCO₂ of 35 to 40 mmHg, and for end tidal capnography, it can be up to 5 mmHg less than PaCO₂.^4,7

• Blood pressure: Maintain mean arterial blood pressure (MAP) at 80 to 100 mmHg (above 100 mmHg with Doppler⁴); with a Cushing reflex, immediate hyperosmolar therapy to lower ICP is indicated.

• Opioids-mu agonists (reversible): For example, fentanyl.⁷

Figure 2

A portion of the Modified Glasgow Coma Scale.8 Total score of 3-18. The lower the score, the more guarded the prognosis. For the complete scale, see veterinaryteambrief.com/modified-glasgow-coma-scale.

Intracranial Therapy

• Provide hyperosmolar therapy to decrease cerebral edema: Mannitol or hypertonic saline increase the osmotic gradient across the blood brain barrier and improve blood flow through cerebral vessels. Hypertonic saline is preferred with hypotension and increased ICP but contraindicated with severe sodium derangements and dehydration; hypovolemia is a relative contraindication for mannitol.^4,7

• Aim to maintain normothermia and avoid hyperthermia.⁶ Induction of hypothermia has been reported in the literature but not extensively studied in veterinary medicine.^4,6

• Aggressively treat seizures.^4,7

Further Diagnostics

Patients nonresponsive to aggressive medical management may need diagnostics such as a brain CT.^4,7

General Care

Care should include dry, well-padded bedding, bladder care if indicated (intermittent catheterization is preferred), frequent turning, passive range of motion, eye lubrication, GI protectants, nutritional support, and head elevation to increase venous drainage (15°-30° from horizontal).^3,6,7

Contraindications

Corticosteroids are not recommended for TBI.^4,6,7,9 Jugular venipucture for blood sampling is also contraindicated.

Conclusion

Oxygen, blood pressure, body temperature, and ventilation maintenance are imperative to maintain normal CPP. Hypovolemic shock and extracranial therapy must be instituted before intracranial assessment and therapy; shock can contribute to poor mentation and neurologic status. In the author's experience, these patients can do quite well.   

Related Article: The Art of Triage

Team Roles

Pamela Fettig, DVM, DACVECC, Oradell Animal Hospital, Paramus, New Jersey

Time is critical when managing a traumatic brain injury and each team member plays an important part. Use this checklist to clarify your role.

Team Training Plan

Debbie Boone, CCS, CVPM, 2 Manage Vets Consulting, Gibsonville, North Carolina

Because time is critical for TBI patients, the practice should have a protocol in place. Make protocol development a fun team exercise. During a team meeting, ask every team member to write on sticky notes each step he or she should take to handle a TBI situation, using one note per step. Then, ask each team member to stick his or her notes on a wall in step-by-step order. The team should decide if they need to add any missing steps. This exercise will also emphasize each team member’s role in aiding the patient and client.

Once the protocol is finalized, the team should role-play a TBI presentation.

Following is a suggested protocol:

• The front-desk team greets the patient and client, recognizes the emergency situation, and visually assesses the patient: Is the patient conscious? Bleeding? Breathing? Having a seizure?

• Often the client is extremely distraught; team members should calm him or her and offer to call friends or family.

• One team member obtains the patient’s records and gathers patient and client information.

• Veterinary technicians or assistants carry the patient to the examination or treatment room. Other veterinary technicians should prepare the necessary tools (eg, x-ray machine, IV catheters and fluids).  

• The front-desk team members alert the veterinarian, who joins the technicians in evaluating the patient. They stabilize the patient, if possible, and create a treatment plan that includes a probable prognosis.

• The veterinarian meets with the client and discusses the prognosis, including treatment options or euthanasia if the prognosis is extremely poor.

• The veterinary technician reviews the treatment plan and the costs with the client.

• The veterinary technician or a front-desk team member ensures the appropriate forms are signed and a deposit is collected.

Quick action is essential for TBI cases and every team member must be well-trained in the steps required to care for both the patient and the client.

Related Article: How to Normalize Emergencies in Practice

Communication Keys

Debbie Boone, CCS, CVPM, 2 Manage Vets Consulting, Gibsonville, North Carolina

Clients whose pet has a TBI are often extremely upset, and the entire team is responsible for helping soothe and support them. Team members should be able to read client body language and react appropriately. Some clients will be more emotional and want physical contact, whereas others will be more controlled and just want verbal reassurance.

A steady, panic-free veterinary team can provide the most comfort to the client. Feeling that competent, well-prepared team members are caring for his or her pet is encouraging and stress-reducing. Here are some tips for communicating with clients:

• When explaining the patient’s care and treatment, all team members should avoid medical language that may be confusing to the client. Describe the situation so that the client can relate. For example, make drawings that show brain swelling or use a pain scale to help with understanding the degree of pain.

• Front-desk team members are likely first to support and calm clients. Show empathy for their distress.

• Veterinary technicians should also show empathy when discussing the treatment process. Let the client know that a test will take 10 minutes rather than leaving him or her in an examination room with no idea what is taking place. Show compassion and collaboration by sitting beside the client instead of standing across the examination table during discussions. Take care to show the value and necessity of suggested services.

• Despite the situation’s urgency, the veterinary technician should always take a history. Ask open-ended questions that require the client to tell a story about what happened. Note the difference between What questions do you have, which opens the dialogue, and Do you have any questions, which likely closes the conversation with No.

• If the patient is hospitalized, continue to communicate with the client about any changes in the treatment plan with updates on the patient’s progress and treatment costs.

• If the prognosis warrants euthanasia, concern for the client is paramount. Every team member should show compassion and understanding. Make a quiet place available for the client to say Goodbye. If necessary, have a team member stay with the client until he or she gains composure, especially if the client is too distraught to drive. Handle the remains with respect.

This article was originally published in the October 2015 issue of Veterinary Team Brief.