CASE STUDY: TRAUMATIC BRAIN INJURY
A 30 year old male is brought to the Emergency Department with a traumatic brain injury. The history is an alleged assault with respiratory arrest following. He has been intubated by the paramedics and has been given adrenaline for hypotension. His pulse rate is 140bpm and his blood pressure is 95mmHg systolic.
On arrival and after initial assessment there are several requests made by various members of the trauma team.
“Can we please give mannitol?”
“Should he have a vasopressor as his BP is low?”
“Can we please paralyse him?”
Which of these requests are valid and why?
Should we use mannitol?
The whole reason for using mannitol is to decrease viscosity and thus increase cerebral blood flow through osmotic diuresis. Does this increase cerebral perfusion pressure?
Mannitol will work only with an intact blood-brain barrier. In fact, current guidelines will only recommend its use in normotensive, euvolaemic patients with clinical signs of raised intracranial pressure.
There is no evidence that dehydration in neurotrauma improves outcome (Neurol Res 1999). To the contrary, the use of mannitol in hypotensive patients can affect cerebral perfusion pressures and lead to decreased perfusion which is an independent predictor of worse outcome (J Trauma 1993).
If indicated the doses warranted are 0.5-1g/kg.
Certainly in this patient mannitol was not indicated as part of the initial resuscitation.
A LITTLE BIT OF TRIVIA ABOUT MANNITOL
As recently reported in the BMJ, there is doubt directed at the original studies, three in total that support high dose mannitol. The studies were published in Neuroscience and Journal of Neuroscience between 2001 and 2004 and recommended 1.4g/kg on average of mannitol. According to Roberts who writes this article, the studies allegedly were conducted by Dr Julio Cruz, a neurosurgeon at the Federal University of Sio Paulo. Apparently the University denies ever having employed him, and his co-authors are not able to verify the patients used. Dr Cruz himself cannot be called on to support his studies as he apparently committed suicide in 2005.
USE OF VASOPRESSORS IN ACUTE BRAIN INJURY
There has been significant discussion about the use of vasopressors to increase Cerebral Perfusion Pressure (CPP).
CPP = Mean arterial pressure(MAP) – Intracranial pressure(ICP)
CPP has been proposed as being beneficial if >70mmHg.
There is significant effect on autoregulation in head injury.
At present, there is no significant evidence for the use of vasopressors in acute head injury. In fact, the data indicates a worse outcome in this patient group (J Neurosug 1995).
Should patients be paralysed?
There is evidence that long term paralysis use in patients may have a detrimental effect and should be used for those patients with known raised intracranial pressure (Crit Care Med 1995). In these patients with initial presentation and GCS of 3, following intubation, sedation may be adequate.
The CT showed extensive subarachnoid blood and a tight brain. ICP was measured at 100mmHg.