Outline the causes, and principles of management of raised intra-cranial pressure in the patient with a severe closed head injury.
Raised intracranial pressure (usually considered > 20 to 25 mmHg) in the setting of severe closed head injury is a relatively frequent phenomenon. The causes usually dictate the specific therapy. specific causes to be considered included artefact, transient elevations associated with coughing/valsalva manoeuvres, , increased brain parenchymal volume (ie. cerebral oedema), increased cerebral blood volume (especially haematomata), increased CSF volume (especially decreased drainage). The likelihood of each is related to the individual circumstances, and relative timing with respect to the injury itself.
Principles of management depend upon what techniques/interventions have already been instituted, but include: provision of adequate oxygenation, ventilation (usually mechanical, aiming for normocapnia if normal bicarbonate [situation less clear if abnormal bicarbonate]) and circulation (adequate CPP [usually considered > 70 mmHg] with euvolaemia and/or use of vasopressors); elevation of head and neck, and ensuring that there is no obstruction to venous drainage; if not already done, establishment of invasive monitoring (to confirm diagnosis and allow titration of therapy); exclusion of artefactual error (zeroing, levelling and calibration as able); minimisation of coughing/valsalva and reduction of metabolic demand with sedation and/or paralysis; drainage of CSF via ventricular drain (if available); detection and drainage of intracerebral haematomata; correction of hyponatraemia (administration of hypertonic saline may provide some short term control); techniques to decrease metabolic demand include anti-seizure treatment/prophylaxis, and temperature control at least to normothermic levels (induced hypothermia is controversial, but seems to decrease ICP in refractory cases); osmotherapy using mannitol may be useful in refractory cases or when buying time before definitive surgery (keeping osmolality < 320 mOsm/kg); other techniques for refractory cases include barbiturate coma, decompressive craniectomy, and possibly hyperventilation (for short term use only).
This was a broad question, about a familiar topic, and could be answered with gusto. A detailed examination of management of raised intracranial pressure is available elsewhere.
- Increase in the volume of CSF (eg. hydrocephalus)
- Increase in the volume of the brain parenchyma (eg. cerebral oedema)
- Increase in the volume of intracranial blood (eg. haemorrhage or decreased venous drainage)
- Foreign material inside the skull (eg. tumour or abscess).
Methods of management: I will not digress extensively about these;
- Draining the EVD
- Positioning the head
- Removing the C-spine collar
- Propofol sedation to decrease distress and thus decrease ICP
- Barbiturate coma if other methods of lowering ICP have failed
- Controversial measures
- Decompressive craniectomy
Chapter 43 (pp. 563) Cerebral protection by Victoria Heaviside and Michelle Hayes, and
Chapter 67 (pp. 765) Severe head injury by John A Myburgh.