Moderate and severe traumatic brain injury: Viva

Branch 1: Severity grading and the meaning of the hypotension

The candidate should grade the injury as severe using the Glasgow Coma Scale. A strong candidate states that the scale scores eye opening from 1 to 4, verbal response from 1 to 5, and motor response from 1 to 6, that the total of 6 places the child in the severe band of 3 to 8, and that the line that matters is at 8, because a child at or below 8 cannot protect the airway and is at high risk of raised intracranial pressure. The candidate should add that the verbal component is modified for the preverbal child, with the score of 5 for coos and babbles down to 1 for no response, as reviewed by Kirkham. [1][2]

If the examiner presses on the hypotension, the candidate should explain that a single hypotensive episode doubles the mortality in severe paediatric traumatic brain injury, because the falling mean arterial pressure collapses the cerebral perfusion pressure. The candidate should link this to the equation that cerebral perfusion pressure equals mean arterial pressure minus intracranial pressure, and state that the blood pressure is therefore defended from the first contact with isotonic fluid and blood. [4]

Branch 2: The intracranial pressure management ladder

If asked to run the ladder, the candidate should first state the two guideline thresholds, the intracranial pressure treatment threshold of 20 mmHg and the cerebral perfusion pressure floor of 40 mmHg, from the Brain Trauma Foundation pediatric guidelines. The ladder then begins with the head elevated to 30 degrees and kept midline, sedation and analgesia, and a neuromuscular blocker if needed, with cerebrospinal fluid drained through an external ventricular drain. [4]

For the rising pressure, the candidate should give the hyperosmolar doses, a 3 percent saline bolus of 2 to 5 mL per kg as the preferred first agent, or mannitol 0.25 to 1 g per kg, titrated to the pressure and the serum sodium. The candidate should add that the ventilation targets normocapnia with a PaCO2 of 35 to 40 mmHg, and that prophylactic hyperventilation and prophylactic hypothermia are both avoided, with a brief period of hyperventilation reserved only for the acutely herniating child. [4][5]

For the refractory case, the candidate should describe a barbiturate coma with pentobarbital or thiopentone titrated to burst suppression on the electroencephalogram, and decompressive craniectomy as the last-resort surgical option. A strong candidate notes that the child is kept normothermic, that the seizures are treated and that prophylactic anticonvulsants are given in the first seven days, and that the intracranial pressure monitor is placed because the scan, though it shows no surgical mass, shows swelling that puts her at high risk of intracranial hypertension. [5]

Branch 3: Appraising the trial evidence

If the examiner moves to the evidence, the candidate should appraise the two landmark trials at the refractory end of the ladder. The Hutchison trial of 2008 randomised children with severe injury to prophylactic hypothermia or normothermia, and it found that the cooling did not improve the outcome and raised a concern about harm, which is why normothermia is the target and hypothermia is not used as a treatment. [7]

The candidate should then appraise the DECRA trial of Cooper and colleagues from 2011, which randomised adults with refractory intracranial hypertension to an early bifrontal decompressive craniectomy or to standard care and found that the early operation was associated with worse outcomes. The candidate should conclude that decompressive craniectomy is therefore reserved for the genuinely refractory case that has failed the medical ladder, not used early, and should acknowledge that DECRA was an adult trial whose conclusion is applied cautiously to children. [8]

A strong candidate closes by stating that the Brain Trauma Foundation pediatric guidelines, reported by Kochanek and colleagues in the second and third editions, remain the single most testable source, that the dominant message of the whole topic is the prevention of the secondary brain injury of hypotension, hypoxia, hypercapnia, hyperthermia, and seizures, and that the prognosis turns on the initial score, the perfusion, and the lesion rather than on the age alone. [4][5]