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Brain Injury Basics

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You see a male lying at the base of a ladder as you drive up to the scene. After assuring the scene is safe, you approach the patient. Holding his head, you assess his airway, breathing and circulation. He's awake, responding to you appropriately with a strong radial pulse. He tells you he was washing windows when he lost his balance and fell backward, striking his head on the pavement below. He thinks he was knocked unconscious after the fall, but he isn't sure how long. His only complaint now is a headache. A rapid assessment reveals blood trickling from his nose and ears. As you and your partner begin to immobilize the patient on a long board, he loses consciousness.

As you arrive at the hospital, you're met by the emergency department (ED) physician, who tells you the neurosurgeon is on the way. The ED physician performs a quick but thorough physical exam and sends the patient for a CT scan, which reveals an epidural hematoma. The neurology team is able to evacuate the clot, and the patient's prognosis is good.

Traumatic Brain Injury 101

Of all types of trauma to the body, traumatic brain injuries result in the most deaths. They commonly result from motor vehicle collisions and sporting accidents, but chronic alcoholics and the elderly are also at risk.

Closed head injuries (CHI) can have an acute onset, as well as a chronic presentation, based on the vessels injured (arteries versus veins) and the location in the brain.

Epidural bleeds are usually arterial in nature. Generally caused by damage to the middle meningeal artery, blood rapidly fills the potential space between the dura mater and cranium. Epidural bleeds commonly have a "lucid interval." A patient is rendered unconscious, regains consciousness for a short period of time and, then, as the bleeding continues to put pressure on the brain, they go unconscious again.

Subdural hematomas can be caused by an arterial bleed but are most commonly venous in nature. The bleed fills the potential space between the dura and arachnoid layers of the menengies. This CHI can present more slowly, with signs and symptoms presenting days to weeks after the injury. Subdural bleeds are common in patients who are prone to falls, such as the elderly and alcoholics.

Signs and Symptoms

Regardless of the type or location of the bleed, there are some common signs and symptoms. As the pressure within the cranial vault increases, pressure is placed on the brain. Early signs of this increased pressure involve changes in mentation. These changes may present as agitation, changes in personality or disorientation. As the pressure continues to increase, the blood vessels in the brain (cerebral vessels) become compressed, limiting blood and oxygen supply to the brain.

The brain requires oxygen to function. When blood supply to the brain is decreased, it triggers the release of chemical messengers, causing an increase in systemic arterial pressure, which helps to facilitate cerebral perfusion. Unfortunately, as the increased arterial pressure allows the brain to remain perfused, it also causes an increase in intracranial pressure (ICP). The increased ICP results in a further increase in systemic arterial pressure. A vicious cycle ensues.

The EMT will see a rise in the systolic blood pressure, moving away from the diastolic pressure. This results in a widening pulse pressure (the difference between the systolic and diastolic pressure). In response to the increase in arterial pressure, the heart rate slows down. The patient will initially breathe quickly to help with cerebral oxygenation.

As ICP increases, pressure will eventually be placed on the brain stem, altering the respiratory pattern and resulting in Biot's, Apneustic or Cheyne-Stokes respirations. This pattern (increased blood pressure, bradycardia and altered respirations) is known as "Cushing's response" or "triad," and, when seen during patient assessment, suggests a CHI with ICP. Other signs associated with ICP are nausea, visual changes, headache and seizures. Physical assessment may reveal unequal pupils (anisocoria), bleeding from the ears, and bruising behind the ears and around the eyes. The latter suggests a fracture to the basilar skull.

Treatment for ICP begins with a thorough history. As suggested above, the traumatic event causing the ICP may be several days prior to the call to EMS. Airway management is a priority. If the patient has an appropriate rate and depth of breathing, provide supplemental oxygen via an NRB mask. The patient's respiratory drive must be monitored. As ICP progresses, airway management will be required.

The airway can be opened with a head-tilt, chin-lift procedure or jaw thrust if a neck injury is suspected. Consider the placement of an oral pharyngeal airway and use of a bag-mask device. Keep suction on standby; vomiting is common. If allowed, consider the placement of an advanced airway, such as a Combitube or King LT airway.

For agencies able to monitor capnography, maintain a CO level of 28 32. If a neck injury is suspected, immobilize the patient as guided by local protocol. If allowed, obtain vascular access but limit fluid administration. Transport the patient to a medical facility with neurological capabilities. Monitor the patient for changes, such as vomiting and seizures. Monitor vital signs closely, watching pulse rate, blood pressure and pulse pressure for trends suggesting ICP. Always consider other possible causes for the altered mentation, such as hypoglycemia or intoxication.

Resource

Kraus JF: "Epidemiology of head injury."Head Injury.3rd edition. pp. 1 25. Lippincott Williams & Wilkins: Baltimore, 1993.

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