ICP monitoring in traumatic brain injury
UAB Vittamed Technologijos has developed cutting-edge non-invasive medical technologies that monitor absolute value of intracranial pressure, cerebral blood flow autoregulation and intracranial volumetric waves in patients with traumatic brain injuries, spinal injuries or other intracraniospinal pathologies. These compelling, disruptive solutions to common, critical and costly medical problems are designed to save lives and prevent disability. The innovative technologies overcome limitations of currently used invasive methods and start a new generation of accurate, reliable, safe and easy to use ultrasonic devices for brain pathology diagnosing and management.
Two most frequent causes of intracranial hypertension, traumatic brain injury (TBI) and stroke, are worldwide epidemics with an estimated joint annual incidence of between 400 - 600 cases per 100,000 inhabitants in the developed countries (1), (2). Over 3 million people in the US and Europe suffer TBI annually, with a mortality of 4% (3), (4). Furthermore, about one third of TBI and nearly half of stroke survivors suffer from permanent functional disabilities whose degree depends on the extent and severity of damages to the brain tissue: in the US only this translates into more than 6 million people (5). Motor vehicles accidents account for half of traumatic brain injuries and the majority of fatal cases.
A key objective after traumatic brain injury is the prevention of secondary insults caused by swelling of injured brain tissue. Because the brain is encased by the rigid skull, tissue swelling leads to raised intracranial pressure, which in turn reduces blood flow, and can lead onto the risk of brain damage and death. Prevention and control of intracranial hypertension are therefore the fundamental goals in the management of patients with TBI or stroke, and ICP monitoring might serve as a basis for making therapeutic decisions as well as provide an objective measure of success of the applied treatment (6).
However the severity of injury may be missed in up to 80% of patients putting them at risk for long-term disabilities and death. This reflects the fact that no specific clinical features or CT scan finding can reliably predict intracranial pressure - it must be measured directly. Intracranial pressure is measured in millimeters of mercury (mmHg): it ranges between 7-15 mmHg in normal adults. ICP levels above 15 mmHg are generally considered abnormal, with treatment usually initiated at levels above 20 mmHg.
Though ICP monitoring per se has never been subjected to prospective randomized clinical trials to establish its efficacy in improving outcome in TBI nor would it be ethically possible to do so, however, plenty of clinical studies (7), (8) and consensus clinical guidelines of the American Association of Neurological Surgeons (AANS) and Brain Trauma Foundation (BTF) (9), (10) support the use of ICP monitoring to guide therapeutic interventions and assess progress. Treatment guided by mean ICP or CPP was shown to have resulted in decreased mortality and shorter hospital stays (11), and improved functional outcome in survivors (12) as compared to patients in whom therapy was guided only by Standard clinical monitoring.
Current technology only allows intracranial pressure to be monitored by drilling a hole in the skull and inserting a pressure probe into the brain. The risks of this invasive approach include infection, bleeding, and brain damage. Invasive ICP monitoring rates can be as high as 27% (13).
In addition devices need to be regularly recalibrated, otherwise measurements tend to drift over time: studies have demonstrated that invasive devices (14) can develop errors of +/-10 mmHg or more over a few days. Prolonged duration of invasive ICP monitoring increases infection rate. The reinsertion and administrations of antibiotics are necessary, but this increases healthcare costs significantly.
Due to these risks, intracranial pressure is usually monitored only in patients with severe head injuries, and only if there is clinical or other evidence that the brain is at-risk due to increased pressure. Consequently many patients with TBI who might benefit from ICP monitoring do not receive it: in the USA ICP monitors are only used in 60% of patients who fulfilled agreed criteria for monitoring (15), while in Europe only a third of eligible patients received monitoring (16).
ICP is rarely monitored in patients with other conditions accompanied with intracranial hypertension. More than 10 million patients per year with conditions such as meningitis, subarachnoid haemorrhage, or hydrocephalus could also benefit from ICP monitoring, but are not monitored today due to the invasive nature of the procedure.
Non-invasive technologies solve high cost medical problems for patients, physicians, hospitals, and insurers. Innovative noninvasive technology turns a complex invasive procedure applied to only the sickest patients into one that is safe, accurate, simple and quick to perform in much wider patient groups and even in sport or aerospace medicine.
_____________________________________________________________________________________________________________
1 Brainin M et al. Eur J Neurol 2000; 7: 5-10.
2 Rutland-Brown W et al. The incidence of TBI in the US, 2003. J Head Trauma Rehabil 2006; 21(6): 544-548.
3 CDC 2006: 1.4 million cases of traumatic brain injury in the USA.
4 Eur J Neurol 2005: Suppl 1: 85-90: 1.6 million cases of traumatic brain injury in Europe.
5 Thurman DJ at al. TBI in the US: A public health perspective. J Head Trauma Rehabil 1999; 14: 602-615.
6 Popovic et al. Recent Patents on Biomedical Engineering 2009, 2, 165-179.
7 Resnick et al: J Trauma; 1997: 43; 1108-1111.
8 Fakhry et al; J Trauma: 2004: 56; 492-9.
9 Brain Trauma Foundation AANS: J Neurotrauma 2007:24: S37-44.
10 Andrews et at. Intensive Care Med: 2008: 34: 1362-1370.
11 Bulger et al. Management of severe head injury. Crit Care Med 2002; 30: 1870-1876.
12 Fakhry et al. Cent Nerv 2004; 56: 492-499.
13 The BTF Guidelines for the management of severe Traumatic Brain injury 3rd edition : J Neurotrauma 2007:24: S26.
14 Martinez-Manas: J Neurol Neurosurg Psychiatry 2000: 69: 82-86.
15 Bulger et al: Crit Care Med: 2002: 30: 1870-6.
16 Stocchetti et al: Intensive Care Med 2001: 26; 400-6