Podcast #230 - ATLS Episode 6: Head Trauma (Chapter 6)

The newest Advanced Trauma Life Support (ATLS) blog and podcast is here!  This time we talk about head trauma.  Get the key pearls and pitfalls as provided by Chip Lange and Mike Sharma.

Remember that the primary goal of treatment for patients with suspected traumatic brain injury (TBI) is to prevent secondary brain injury.  This includes that computed tomography (CT) should not delay patient transfer to a trauma center that is capable of immediate and definitive neurosurgical intervention.  This does not mean that CT should never be performed, but that obvious cases that need transfer should not be delayed by CT being performed at the initial facility.

Brief Anatomy:

• Scalps have a generous blood supply
  • Lacerations to the scalp can result in major blood loss, hemorrhagic shock, and even death.
  • Patients with long transport times are at particular risk for these complications.
• The brain consists of the brainstem, cerebellum, and cerebrum
  • The brainstem is composed of the midbrain, pons, and medulla and is essential for vital functions which means that even a small lesion can be associated with severe neurological deficits.
  • The cerebellum is responsible for mainly coordination and balance.
  • The cerebrum is higher order functions (speech, emotions, thought, etc).
• The ventricular system contains cerebrospinal fluid (CSF) and when there is blood it can impair reabsorption resulting in increased intracranial pressure.
• The oculomotor nerve (cranial nerve III) runs along the edge of the tentorium.
  • It may become compressed against it during temporal lobe herniation.
  • Parasympathetic fibers that constrict the pupil lie on the surface of the third cranial nerve and compression of these superficial fibers during herniation causes pupillary dilation due to unopposed sympathetic activity (often referred to as a "blown" pupil).
  • Ipsilateral pupillary dilation associated with contralateral hemiparesis is the classic sign of uncal herniation.

Brief Physiology:

• Monro-Kellie Doctrine
  • The total volume of the intracranial contents must remain constant because the cranium is a rigid container incapable of expanding.
  • When the normal intracranial volume is exceeded, intracranial pressure (ICP) rises.
  • ICP will rapidly increase once such volume has been exceeded (see figure below).
• Make every effort to enhance cerebral perfusion and blood flow by reducing elevated ICP, maintaining normal intravascular volume and mean arterial pressure (MAP), and restoring oxygenation and ventilation. 
• Hematomas and other lesions that increased intracranial volume should be evacuated early.

Head Injury Classification:

• A Glasgow Coma Scale (GCS) can be used to help grade injury severity.
  • When there is right/left or upper/lower asymmetry, be sure to use the best motor response to calculate the score because it is a more reliable predictor of outcome.
  • A GCS of 8 or less has become the generally accepted definition of coma or severe brain injury.
  • A GCS of 9-12 is a "moderate injury" and GCS of 13-15 is a "mild injury" when graded.
• Do not underestimate the significance of a skull fracture because it takes considerable force to fracture the skull.
• Epidural hematomas are relatively uncommon, occurring in about 0.5% of patients with TBI but 9% of TBI with comatose.
  • They are typically biconvex or lenticular in shape as they push the adherent dura away from the inner table of the skull.
  • The classic presentation is a lucid interval between the time of injury and neurological deterioration ("talk and die" syndrome).
• Subdural hematomas are more common are occur in approximately 30% of severe TBIs.
  • They often develop from the shearing of small surface or bridging blood vessels of the cerebral cortex.
  • Damage underlying an acute subdural hematoma is typically much more severe than that associated with epidural hematomas due to the presence of concomitant parenchymal injury.
• Cerebral contusions are fairly common and occur in approximately 20-30% of severe TBIs.
  • Patients with contusions generally undergo repeat CT scanning to evaluate for changes in the pattern of injury within 24 hours of the initial scan.

Treatment Guidelines:

• Never ascribe alterations in mental status to confounding factors until brain injury can be definitively excluded.
• Mild TBI management
  • A history of a brief loss of consciousness (LOC) can be difficult to confirm and the clinical picture can be confounded by alcohol or other intoxicants.
  • CT scanning is the preferred method of imaging although obtaining this should not delay patients that require transfer.
  • Obtain a CT scan in all patients with suspected brain injury who have a clinically suspected open skull fracture, any sign of basilar skull fracture, and more than two episodes of vomiting.
  • Patients 65 years old and older should also have a CT.
  • Additional considerations for CT would be a LOC of greater than 5 minutes, retrograde amnesia longer than 30 minutes, a dangerous mechanism of injury, severe headaches, seizures, short term memory deficit, alcohol or drug intoxication, coagulopathy, or a focal neurological deficit.
  • Check out the Canadian CT Head Rule as this is a great way to go through imaging indications.
• Moderate TBI management
  • Approximately 15% of patients with brain injury who are seen in the emergency department have a moderate injury.
  • They may still follow simple commands, but they usually are confused or somnolent and can have focal neurological deficits such as hemiparesis.
  • Approximately 10-20% will lapse into a coma.
• Severe TBI management
  • Approximately 10% of patients who are seen in the emergency department with a brain injury will be severe.
  • Patients are unable to follow simple commands, even after cardiopulmonary stabilization.
  • A "wait and see" approach in such patients can be disastrous and prompt diagnosis and treatment are extremely important.

Resuscitation:

• It is imperative to rapidly achieve cardiopulmonary stabilization in patients with severe TBI.
• Hypotension usually is not due to the brain injury itself except in the terminal stages when medullary failure supervenes or there is a concomitant spinal cord injury.
  • Maintain systolic blood pressure (SBP) at 100 mm Hg or higher for patients between 50 to 69 years of age.
  • Maintain SBP at 110 mm Hg or higher for patients 15 to 49 years of age or if they are 70 years or older in age.
• When a patient demonstrates variable responses to stimulation, the best motor response elicited is a more accurate prognostic indicator than the worst response.
  • Never attempt a doll's-eye test until a cervical spine injury has been ruled out.
  • It is important to obtain the GCS and perform a pupillary exam before sedating or paralyzing the patient because knowledge of the patient's clinical condition is important for determining subsequent treatment. 
• A shift of 5 mm or greater often indicates the need for surgery to evacuate the blood clot or contusion causing the shift.

Therapies:

• The basic principle of TBI treatment is that if injured neural tissue is given optimal condition in which to recover it can regain normal function.
• Hypovolemia in patients with TBI is harmful as well as hyperglycemia and hyponatremia.
• Use hyperventilation only in moderation and for a limited period of time.
  • Hyperventilation acts by reducing PaCO2 and causing cerebral vasoconstriction.
  • Prophylactic hyperventilation (pCO2 < 25 mm Hg) is not recommended.
• Hypertonic saline versus mannitol is a bit of controversy and debate.
  • Hypertonic saline may be preferable for patients with hypotension.
  • Mannitol is also an acceptable option, but may not be as well supported.
  • There is signal for benefit with hypertonic saline versus mannitol but worth checking a variety of sources including the Cochrane Library, Journal of Intensive Care, Surgical Neurology International, and Critical Care Medicine.
• Surgical management is a key component, but this is generally out of the purview of emergency medicine (with some exceptions).
• Below is an overview of the management of TBIs based on severity and is a great recap.

Let us know what you think by giving us feedback here in the comments section or contacting us on Twitter or Facebook.  Remember to look us up on Libsyn and on Apple Podcasts.  If you have any questions you can also comment below, email at [email protected], or send a message from the page.  We hope to talk to everyone again soon.  Until then, continue to provide total care everywhere.

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