72. Secondary brain injury Flashcards
You are called to A&E to see a 40-year-old man with a GCS of 6, who
was brought in with a history of spontaneous headache and then a grand
mal fit.
What do you think the differential diagnosis could be?
This is a fairly classic history for a spontaneous sub-arachnoid haemorrhage,
although a history of trauma should be sought, backed up by careful clinical
examination.
The other major differential diagnosis is an infective CNS
cause such as bacterial or viral meningitis or encephalitis.
Other causes of a fit include
Primary epilepsy
Secondary epilepsy from a space occupying lesion or intra-cerebral
haemorrhage or infarct
Electrolyte disturbances
Hypoglycaemia
Assuming someone is dealing with his airway, breathing and
circulation, what tests do you want to do immediately?
Blood sugar
Arterial blood gas
Hypoxia
Hypercapnia
Profound acidosis
Ideally, the ABG would rapidly show relevant electrolytes such as sodium and calcium.
Assuming his GCS remains the same, what would you do?
He needs intubating and ventilating in order to
Secure his airway
Prevent aspiration
Control his pO2 and CO2.
Does he need an anaesthetic?
Yes! Even though he is unconscious, reducing the CMRO2 and minimising
ICP and MAP surges associated with intubation require adequate doses of
anaesthetic agents.
The quickest and safest way to secure his airway would be to use suxamethonium.
Does suxamethonium have an effect on ICP?
Probably. Animal data have demonstrated a rise in ICP and this has been
both confirmed and rejected by small human studies.
This has to be weighed against securing the airway safely and effectively
The technique could be modified with the use of an opioid or pre-treatment
with a small dose (10% ususal dose) of a non-depolarising muscle relaxant
to minimise the rise in ICP.
Doesn’t using an opioid alter the basis of the rapid sequence induction?
This is again something that has to be balanced carefully.
If the airway assessment does not reveal any cause for concern, then the use
of an opioid in such situations would minimise the risk of ICP changes.
If there is any doubt about safely securing the airway, then this has to be
the priority and a simple RSI may be the safest option.
Would you use Remifentanil?
There have been case reports of remifentanil (and other opioids) causing
asystole when delivered by bolus injection.
Combination with the vagotonic effects of suxamethonium or a raised ICP
has also led to profound bradycardias and asystole being reported.
Current advice is to avoid remifentanil and suxamethonium together unless
you can justify the benefits (profound, short-acting, blunting of the pressor
response to laryngoscopy).
Pre-treatment with a vagolytic such as glycopyrrolate would also be an
option.
What do you understand by the term secondary brain injury?
This is any ischaemic neurological damage that occurs after the primary injury.
Significantly worse outcome has been demonstrated in traumatic severely
brain injured patients with:
Hypotension defined as systolic blood pressure <90 mm Hg
Hypoxia with PaO2 <9 kPa
(or apnoea, cyanosis or an oxygen saturation <90%).
These factors must be monitored and avoided if possible and, at the very least,
corrected immediately.
The mean arterial blood pressure should be maintained above 90 mm Hg.
Infusion of fluids to attempt to maintain cerebral perfusion pressure (CPP)
greater than 60 mm Hg.
Hypotonic solutions should be avoided as they can contribute to cerebral
oedema.
What are your targets with regard to ventilation?
PaO2 greater than 13 kPa.
Low normocapnia with PaCO2 around 4.0 – 4.5 kPa.
Aggressive hyperventilation to sub-normal PaCO2 has been shown to
worsen outcome even in the face of raised ICP due to compromise of the
cerebral blood flow
What other options do you have to lower an acutely raised ICP?
Mannitol is effective for control of raised ICP after severe head injury.
Effective doses range from 0.25 g/kg body weight to 1 g/kg body weight.
The indications for the use of mannitol prior to ICP monitoring are
Signs of transtentorial herniation
Progressive neurological deterioration not attributable to extra-cranial causes.
Serum osmolarity should be kept below 320 mOsm/l.
Euvolemia should be maintained by adequate fluid replacement.
A urinary catheter is essential in these patients.
Central venous pressure monitoring is usually required.
Intermittent boluses of mannitol may be more effective than continuous infusion.
Other points of note in managing head injuries:
Simple ICU nursing care can be of great benefit in reducing ICP.
Ensure good venous drainage of the head – by ensuring that the neck
veins are not occluded or kinked.
Sit the patient 15 degrees head up.
Avoid coughing by paralysis and minimal tracheal suctioning.
Paralysing a patient can result in fits going undetected so deep
sedation is usually preferred if paralysis is not essential.
Adequate sedation for procedures can also minimise ICP rises
NICE 07 Head injury guide
National Institute for Clinical Excellence regarding the immediate
management of head injury. They broadly follow the ATLS scheme for
immediate attention to the airway with cervical spine control, breathing,
and circulation. In traumatic cases, there should be a concurrent
assessment of other injuries and stabilisation if appropriate. There is
further evidence to guide imaging, referral to a tertiary centre, and
when to measure and control ICP.
Intubation and ventilation of the head injured may be required for
several reasons.
To facilitate CT scanning in the obtunded or intoxicated patient.
To facilitate transfer in certain circumstances (long distances, likely deterioration).
GCS <8 or loss of laryngeal reflexes.
Ventilatory insufficiency as judged by blood gas estimation.
PaO2 < 9kPa on air (or 13 kPa on oxygen)
PaCO2 > 6
PaCO2 < 3.5 due to spontaneous hyperventilation.
If the patient needs transferring and there are facial injuries or a
dropping GCS which may need intervention en-route.
Would you use an anti-convulsant in this patient
Anti-convulsants may be used to prevent early post-traumatic seizures in
patients at high risk for seizures following head injury.
Phenytoin and carbamazepine have been demonstrated to be effective in
preventing early post-traumatic seizures.
However, the available evidence does not indicate that prevention of early
post-traumatic seizures improves outcome following head injury
Would you tape the patient’s eyes shut for a transfer?
This is a balance of the risks of sustaining a corneal injury, or missing the
signs of a raised ICP or intra-cerebral problem causing a III cranial nerve
palsy.
I would lightly tape the eyes and ensure that I regularly inspected the pupils.
