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 focuses on preventing secondary injury and being alert to a surgically remediable event. This includes mitigating clinical factors that may increase brain injury. There is good evidence that it is beneficial to avoid hypotension; hypoxaemia; hyperthermia; and hyperglycaemia. While evidence for benefit in lowering of ICP is more limited, raised ICP and brain swelling are known to be harmful. Therefore, in some patients with TBI (particularly those with GCS<8 and an abnormal CT) a direct monitor for ICP may be placed.
Maintaining the cerebral perfusion pressure (CPP) is also thought to be beneficial, although detailed discussion is beyond the scope of this guideline.
CPP = MAP - ICP
This formula is only accurate when both the ICP and MAP are directly measured. See below for age-related values. Some patients may benefit from a strategy primarily focused on reducing ICP, whereas others may benefit from a strategy focused on maintaining CPP, depending on autoregulatory status.
Preventing secondary brain injury starts with good basic intensive care and attention to detail - 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.
Hyperventilation with the aim of achieving a low pCO2 reduces ICP, but achieves this via cerebral vasoconstriction and therefore may cause cerebral ischaemia. A more conservative approach is now taken aiming for a low-normal pCO2 (4.5-5 kPa), and only resorting to hyperventilation in emergencies, such as impending cerebral herniation, or as a bridge to imminent surgery. 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. Hypertonic saline and mannitol (osmotic diuretics) are both highly effective at reducing ICP quickly, with hypertonic saline now being the first choice and the only advice within this guideline for reducing ICP that is supported by level 2 evidence.
If the ICP is difficult to control, an external ventricular drain (EVD) can be placed by the neurosurgeons in selected cases.. If an EVD is present then one response to raised ICP is to drain 5-10mL of CSF and allow the ICP to normalise. (See EVD guideline).
The evidence for all subsequent therapeutic measures to reduce ICP and prevent secondary brain injury is patchy at best. There was 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 randomised controlled trial (RCT) evidence in paediatrics to date has found no benefit to routine prophylactic cooling in patients with traumatic brain injury. Moderate cooling (32-34oC) as a secondary intervention can be considered if ICP remains problematic after osmotic diuretics are given. If actively cooling, paralysis should be commenced to prevent shivering which increases ICP and oxygen demand.
Thiopental coma is an advanced treatment when ICP is refractory to treatment, but needs to be considered and undertaken carefully. Thiopental 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 thiopental coma aiming for a reduction in ICP primarily or burst suppression. Thiopental is a particularly toxic substance which has a long half-life. An irritating side-effect of thiopental 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 thiopental levels have fallen. A Cochrane Review concluded that barbiturate therapy did not improve outcome in head injury.
Decompressive craniectomy is a 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. Evidence from the RESCUEicp trial (exclusive of children) shows a small mortality benefit, but at the cost of an increase in severely disabled survivors (including outcomes such as persistent vegetative state) However, children may well have better potential for neurological recovery after craniectomy than adults. Decompressive craniectomy may have a place in well- selected cases. ICP dose burden (ie longer periods of time with high ICP) is harmful, and so there is some expert opinion that outcomes may be improved if decompressive craniectomy is performed early.