Head, Spinal, and Burn Trauma

Head, Spinal, and Burn Trauma

1. Severe Traumatic Brain Injury

Start with the pressure relationship — it explains every target below.

Normal intracranial pressure is 2–12 mmHg. Cerebral perfusion pressure is mean arterial pressure minus intracranial pressure. So the brain can lose perfusion from either end. Hypotension drops the MAP side. Rising ICP eats into the same equation from the other side. Hypotension and rising ICP do the same damage by different routes.

That's why one hypotensive episode is so costly in a head injury. And it's why you never lower a hypertensive blood pressure in a head injury — that hypertension is the body defending its own perfusion pressure. Treat it and you take away the one thing keeping blood flowing to the brain.

Injury types. Coup is the injury under the point of impact. Contrecoup is on the opposite side, where the brain slammed into the skull as it rebounded. Diffuse axonal injury is a shearing of white-matter tracts — a profound deficit even though the head looks unremarkable.

Then there are the two bleeds the exam loves to contrast.

Epidural is fast because it's arterial pressure filling the space. Subdural is slow because it's venous. That's the mechanism behind the pattern — you don't have to memorize the timeline separately from the vessel.

Skull fractures are linear, depressed, open, or basilar. Basilar signs are periorbital bruising, mastoid bruising, and CSF leaking from the nose or ears.

Herniation is what happens when rising ICP pushes brain tissue out of its compartment. The named syndromes are uncal, central, and cerebellar. What you'll actually see in the field is a cluster of signs. A unilateral blown, sluggish pupil, posturing, and Cushing's triad — that's rising blood pressure, falling pulse, and irregular respirations — with a falling GCS.

Posturing tells you how bad it is. Decorticate posturing is flexion toward the core — arms curled in. Decerebrate is extension — arms and legs straightening and rotating out. Decorticate comes from a higher lesion; decerebrate, a lower one, closer to the brainstem. So a patient going from decorticate to decerebrate is getting worse, not better.

The evidence-based bundle. Every one of these targets exists because a single bad episode measurably worsens outcome in severe TBI.

Ventilate to a normal CO₂, not to a habit. Hyperventilating a head injury used to be standard teaching, and it's wrong. Prophylactic hyperventilation constricts cerebral vessels and cuts perfusion to tissue that's already hurt. Brief, mild hyperventilation is reserved for active herniation signs only. That's the blown pupil, the posturing, or Cushing's triad with a rapid decline. It's a temporary bridge, and the rate goes back to normal as soon as those signs let up.

Airway management in TBI is high-stakes. Hypoxia and hypotension during intubation are the two events most tied to worse outcomes. So preoxygenate deliberately, resuscitate the pressure before you induce where you can, and use the smallest effective doses of any agent that drops blood pressure. Confirm placement with waveform capnography, then control the ventilation deliberately afterward — an over-ventilated intubated head injury is common, and it's avoidable.

Also elevate the head about 30 degrees, keep the neck midline, and avoid tight collar straps — they impede jugular drainage, which raises ICP right back up. Treat seizures promptly. Manage pain and agitation, since both raise ICP, but weigh that against the hypotension your sedation can cause.