Traumatic Brain Injury, Paediatrics (012)

Traumatic Brain injury (TBI) is a major source of mortality amongst older children. Public health measures have had the biggest impact on reduction in mortality and morbidity in recent years (safety helmets, seatbelts, speed reduction). 

The intensive care management of these injuries focus on preventing secondary injury and being alert to a surgically remedial event. This includes trying to prevent or reduce any further factors that may increase brain injury. Avoidance of hypoxia, hypotension, pyrexia and hypoglycaemia are probably the only factors that clinicians agree should be avoided. There is general acceptance that trying to minimise further swelling of the brain and control the intracranial pressure (ICP) may be useful. Therefore in some brain injuries particularly if the GCS<8 and with an abnormal CT a direct monitor for ICP may be placed.

Maintaining the cerebral perfusion pressure (CPP) of the brain is felt to be even more important.

CPP= MAP -ICP

This formula is most useful when both the ICP and MAP are directly measured. See below for age-related values.

A basic strategy for preventing secondary brain injury is good basic intensive care. Sedate and minimise oxygen demand, employ minimal handling to prevent surges in ICP, oxygenate well, maintain blood pressure (therefore keeping CPP adequate), treat pyrexia and avoid hypoglycaemia.

Until fairly recently it was standard management to hyperventilate patients and aim for a low pCO2 – this definitely reduced the ICP but as it works via cerebral vasoconstriction it also reduced oxygen delivery to the brain. A more conservative approach is now taken aiming for a low normal pCO2 (4.5-5 kPa) and only resorting to hyperventilation if there are concerns of impending cerebral herniation. Judicious use of inotropes to maintain and support CPP is important. There is some evidence that noradrenaline is superior to dopamine. However it is more important to maintain CPP than differentiate between agents.

If the above basic management fails other steps may be taken to control ICP. Mannitol and hypertonic saline (osmotic diuretics) are both highly effective at reducing ICP quickly. The debate as to whether one is superior to the other continues.

If the ICP is difficult to control sometimes an external ventricular drain (EVD) will be placed by the neurosurgeon. An EVD can be technically difficult to insert in a swollen brain and may require the aid of a volume CT scan which is only performed during the day. If an EVD is present then one response to raised ICP is to let some CSF drain out and allow the ICP to normalise. (See EVD guideline).

The evidence for all secondary therapeutic measures to reduce ICP and prevent secondary brain injury is patchy at best. There was and remains great hope on the basis of animal, neonatal and adult data that therapeutic hypothermia may minimise secondary brain injury. Cooling appears to improve survival and function in both neonatal encephalopathy and post-cardiac arrest in adults. However most head injury trials have failed to correlate cooling with improved survival. The only randomised controlled trial (RCT) in paediatrics to date cooled for 24hours and found no benefit. It may be that we just don’t know how long, how quickly or how cold to cool patients as yet to be effective. Alternatively in the future it may be that cooling is discounted as a treatment strategy. Meanwhile it is common practice to undertake cooling as a secondary intervention if ICP remains problematic. If actively cooling paralysis should be commenced to prevent shivering which increases ICP and oxygen demand.

Thiopentone coma remains a standard treatment when ICP is difficult to control but needs to be undertaken carefully. Thiopentone infusion will lead to a fall in blood pressure and measures must be in place to avoid this (eg. noradrenaline). CFAM monitoring or EEG should be used in conjunction with thiopentone coma aiming for a reduction in ICP primarily or burst suppression. Thiopentone is a particularly toxic substance which has a long half-life. An irritating side-effect of thiopentone is that it may induce fixed dilated pupils. This removes one of the key areas of brain function assessment when paralysed and sedated. Brain stem testing cannot be performed until thiopentone levels have fallen. A Cochrane Review concluded that barbiturate therapy did not improve outcome in head injury

Decompressive craniectomy is an age old surgical treatment which literally allows the rigid box of the skull to be opened. This allows room for the brain to swell and therefore reduces ICP. There is concern that decompressive craniectomy may increase survival but at a very poor functioning level (eg. persistent vegetative state). A recent randomised study DECRA did not include children and failed to reveal a positive outcome. Decompressive craniectomy may have a place in a few well selected cases, current consensus is that outcomes may be improved if decompressive craniectomy is performed early.

The general aims of PICU management of children with severe head injuries are to meticulously maintain adequate oxygenation of the arterial blood, achieve a blood pressure that will perfuse the brain and an intracranial pressure of less than 20mmHg. It is also necessary to bear in mind continually the possibility of the development of an intracranial lesion that may require surgery.

• Elevate head of bed to 30^o.
• Head kept midline & in the neutral position (neither flexed or extended).
• Cervical collar not impeding cerebral venous return.
• Place oral-gastric tube. (avoid nasal route as may have basal skull fracture).
• Meticulous attention to pressure areas. (A pressure-relieving mattress must not be used in any patient in which there are concerns regarding spinal injury).
• Adequate drainage of urine (increased intra-abdominal pressure will ↑ ICP).
• Cooling blanket in place if need is anticipated.

Treat all TBI as having a C-spine injury

Oral ETT placed. (avoid nasal route as may have basal skull fracture). The aim of ventilation is to maintain adequate oxygenation with low normocapnia.

PaO2 >10 -13kPa PaCO2 4.5- 5 kPa

This should be achieved at the lowest possible PIP and PEEP (<5mmHg). 

Some literature suggest there may be a place for Pressure Regulated Volume Controlled Mode of ventilation (ie SIMV Autoflow, rather than BIPAP). More important than mode is to measure end-tidal pCO2 continuously and react to changes.

Arterial gases should be performed at least 4-6 hourly in the first few days of admission. A change in end-tidal pCO2 or rise in ICP should result in a repeat gas.

Endotracheal suctioning (ETS) may produce significant (usually transient) rises in ICP. It remains necessary, but should be minimised and some means of prophylaxis –sedation boluses ( Fentanyl 2micrograms/kg IV) or endotracheal instillation of lignocaine 1% (max 2mls)- should be considered.

C-spine – ensure correct collar placement and careful moving and handling as per APLS guidelines. Log-roll –no straight lifting. See separate moving and handling guideline.

Hypotension should be considered an emergency

If adequate filling alone fails to produce an adequate blood pressure then judicious use of inotropic support will be necessary. Consider noradrenaline/ dopamine/adrenaline to titrate to BP. Arterial and central venous catheters will generally be placed to allow continual monitoring of arterial and CVP. Transducers will be levelled to the right atrium. Femoral lines are preferred in view of less disruption to cerebral venous return. Aim for a CVP 6-10mmHg.

Fluids: 0.9% saline (75-100% calculated maintenance) Glucose should be withheld from the IV solution if the serum glucose is above 10 mmol/l. When serum glucose reaches the normal range the IV solution should be changed to 5% dextrose/0.9% saline.

Avoid hypoglycaemia -if found treat quickly and ensure followed up carefully. Give 2ml/kg of 10% dextrose and repeat sugar at 30 mins and 1 hour minimum.

Electrolytes Hyponatraemia may produce further brain swelling in this context (particularly if inappropriate ADH syndrome occurs) therefore target:

[Na] at >140mmol/l and a serum osmolality of >280mOsm

Aim for normokalaemia.

Maintaining an optimal Cerebral Perfusion Pressure (CPP) is critical, as well as controlling the ICP.

CPP = MAP – ICP

Agree target ICP and CPP for intervention for each individual patient with intensivist and neurosurgeon.

Neuro-observations must be performed regularly – every 30 minutes if an ICP monitor is not in-situ. 2 hourly if ICP monitor in place. Any changes should be alerted to a doctor.

ICP monitoring – If present be alert to changes. For set up and background to ICP -See separate ICP monitoring guideline.

If elevation of ICP is >20mmHg for >5min then move on to CONTROL ICP ALGORITHM

Analgesia and Sedation

Patients should receive an infusion of narcotic (morphine or fentanyl) and midazolam. Inadequate sedation should be a first consideration for raised ICP Once adequately sedated, a muscle relaxant may be added prn as a bolus to prevent coughing on suction. If cooled, paralysis should be delivered as a continuous infusion to prevent shivering and its associated metabolic demands.

Seizures

Patients have a high risk of seizures which can be difficult to recognise in a sedated +/- paralysed child. Seizures increase ICP substantially, therefore a prophylactic approach has been adopted. Load with phenytoin IV (18mg/kg over 30 mins) and then continue maintenance dose for at least 7 days.

• Core (rectal or bladder) temperature should be monitored continually in these children. The aim should be to maintain a temperature of 36.5 -37°C using paracetamol and cooling blanket if necessary.
• If the child is therapeutically cooled for raised ICP then they must NOT be allowed to shiver. Continuous paralysis should be commenced.
• Where possible place a second cooling blanket on top of the patient.
• If the temperature is slow to fall consider use of cold packs, take care to monitor for cold injury, rotate frequently.
• Be vigilant against pressure areas on cooling blankets.
• Once target temperature reached remove 2nd blanket and ice packs.
• See separate Blanketrol guideline for further details on set up and use of cooling blankets.

When re-warming after hypothermia:

• Rewarm by 10C every 4 hours by setting the blanket temp up 0.5 ^OC every 2 hours.
• Be vigilant that the patient does not re-warm faster.
• Therefore in practice if at 33^oC the child will take 14 hours to re-warm.

• Enteral feeding should be considered early and should follow our standard nutrition guidelines.
• Ranitidine 1mg/kg IV every 6 hours should be prescribed until feeds are well established.
• Regular laxatives/aperients are started early to avoid straining. 

Eye Care

• Standard eye care treatment as per eye care guidelines.
• Beware ophthalmic assessment: long-acting dilating agents are contraindicated as these mask pupillary response and render us unable to evaluate brain injury

Infection and Sepsis

• Blood, urine and BAL cultures if pyrexial. BAL – same care as suctioning.
• Daily CSF cultures if EVD in Situ – See separate EVD guideline. 

Laboratory Tests

• Morning bloods: Daily U &E’s, FBC, clotting including serum osmolality.
• 8 hourly U&E’s in first 3 days or if remains unstable.
• Art gases- 4-6 hourly
• If the child becomes polyuric consider diabetes insipidus – record specific gravity, send U&E’s and paired blood and urine for osmolality.- See separate Diabetes Insipidus guideline

DVT prophylaxis

• If child is large enough (eg > 40Kg) apply correct size TED stockings if child is immobile >48hrs (if other injuries allow).
• Consider use of Low molecular weight heparin (enoxaparin) – discuss with neurosurgeon.

 In the case of a patient who has no known radiological injury to the cervical spine and who is well sedated and immobile (paralysed), the purpose of the cervical collar is to serve as a warning of a potential neck lesion. The initial hard collar should be exchanged for a suitably sized long –term collar (eg.Miami –J). The collar should be left in situ but should be left open except when the patient is being moved to scan etc. or log rolled. The head should still be protected with sandbags either side. A sign should be placed above the bed declaring “ C-spine not cleared” .The collar must not be allowed to obstruct venous return or become a source of pressure necrosis. The collar MUST be fastened up again when the child is moved, log rolled, woken up or when the paralysis is discontinued.

KEY POINTS

• Good oxygenation at all times
• Avoid / Treat aggressively any drops in Cerebral Perfusion Pressure
• If these measures fail to control ICP: elevation of ICP is >20mmHg for >5min then move on to CONTROL ICP ALGORITHM

Treatment threshold is a sustained ICP rise above target limit for > 5 minutes.

Ensure all general management outlined is being achieved if not correct this first.

→ Consider mass lesion – CT SCAN & Neurosurgical Opinion

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First Tier Therapy

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ICP STILL RAISED

Second Tier Therapies (all lack conclusive proof of benefit)

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ICP STILL RAISED or impending cerebral herniation?

*Thiopentone is a potent and toxic drug. It acts on GABA A and offers cerebral protection. It should be used with caution, using the smallest dose possible and titrated to effect, aiming to lower ICP. CFAM monitoring should always be used. It accumulates over time as it undergoes zero-order kinetics. Levels need to be checked prior to being able to perform brain stem testing. Alternatively propofol infusion can be considered in older children but consider carefully propofol syndrome.

^1. NB. Thiopentone can reduce the life-span of gas machine cartridges – if a patient is on a thiopentone infusion all samples from that patient should be run through the same gas machine. The gas machine should be labelled thiopentone. It can continue to be used for other patients.

The above is intended as a guide. It may be more appropriate in individual cases to tolerate a mildly elevated ICP (eg. 25mmHg) rather than proceed to second tier therapies.