Year : 2014 | Volume
: 2 | Issue : 3 | Page : 162--165
The use of transcranial doppler pulsatility index to guide intracranial pressure monitoring in intoxicated traumatic brain injury patients
Department of Neurosurgery, King Fahd Hospital of the University, University of Dammam, Al-Khobar, Kingdom of Saudi Arabia; Department of Neurology and Neurosurgery, Montreal, Neurological Institute/Hospital, McGill University, Montreal, Canada
C/o Luisa Birri, 3801 University Street, Suite 109, Montreal, QC, H3A 2B4, Canada
Introduction: Management of intracranial pressure (ICP) represents a cornerstone in the care of traumatic brain injury (TBI) patients. On occasions, intoxicated TBI represent a clinical challenge since their initial imaging is not significantly correlating with elevated ICP yet their neurological exam concerns toward that possibility.
Materials and Methods: We present an initial series of intoxicated TBI patients in which the trans-cranial Doppler (TCD) were conducted to noninvasively judge the ICP and correlate those with the clinical findings.
Results: A total of four patients is reported in this series. About 50% of the patients had evidence of elevated ICP based on TCD parameters confirmed by ICP monitors.
Conclusion: From our series, TCD screening examinations were helpful in expediting an objective guided decision for intracranial pressure monitoring.
|How to cite this article:|
Al-Jehani H. The use of transcranial doppler pulsatility index to guide intracranial pressure monitoring in intoxicated traumatic brain injury patients.Saudi J Med Med Sci 2014;2:162-165
|How to cite this URL:|
Al-Jehani H. The use of transcranial doppler pulsatility index to guide intracranial pressure monitoring in intoxicated traumatic brain injury patients. Saudi J Med Med Sci [serial online] 2014 [cited 2018 Jul 18 ];2:162-165
Available from: http://www.sjmms.net/text.asp?2014/2/3/162/142506
Intracranial hypertension is a major determinant of poor outcome in a variety of neurological and neurosurgical diseases. Determination and control of intracranial pressure (ICP) has long been of paramount importance to optimize cerebral perfusion pressure (CPP) and as a result cerebral homeostasis. , Apart from traumatic brain injury (TBI), there are no clear guidelines for ICP monitoring.  The insertion of ICP monitors in the form of external ventricular drains or intraparenchymal pressure sensors, is an invasive procedure with inherent risks and could be contraindicated in case of severe coagulopathy. Trans-cranial Doppler (TCD) pulsatility index (PI) has emerged as a surrogate marker for ICP.  For the most part, it is currently used as a snapshot screening tool, mainly because it is cumbersome to utilize in a continuous monitoring fashion and second because there is a lack of consensus as to the accuracy and applicability in the therapeutic decision making.
The Brain Trauma Foundation issued and updated its guidelines for ICP monitoring, recommending the use of ICP monitors for patients with a Glasgow Coma scale (GCS) score 8 that are at risk of having elevated ICP. , The major decision point is the clinical examination based on the post-resuscitation GCS level.
Evaluation of TBI patients heavily depend on the GCS which is universally accepted and used for assessing the level of consciousness.  The GCS was used initially to evaluate patients in coma for more than 6 hours, to account for temporary confounders of GCS level such as hyoxia, hypotension, and alcohol intoxication. 
There are several factors that might interfere with the assessment of the level of consciousness by GCS. First and foremost in a level 1 trauma center in an urban North American setting is alcohol intoxication. It has been reported that alcohol is involved in up to 40% of severe closed head injuries. 
"High risk" TBI patients are those defined as closed head injuries who were incapable of following commands or utter recognizable words after cardiopulmonary resuscitation. Patients who are likely to have high ICP had abnormal findings on head computed tomography (CT) scan or normal CT scan at admission, with two of the following three features: Age >40 years, unilateral or bilateral motor posturing, or systolic blood pressure <90 mm Hg. Knowing the ICP provides an indirect measure of CPP and was shown to be a strong predictor of outcome. ,, We present our experience in utilizing the TCD as a surrogate assessment of ICP.
MATERIALS AND METHODS
This is a proof-of-concept technical report with illustrative cases on the use of PI to judge the ICP in series of intoxicated patients presenting with nonsurgical lesions on their initial imaging. TCD ultrasonography (Zonare, zone. one) was used in the Intensive Care Unit (ICU) to obtain the PI and predict the ICP. All TCD examinations were performed by a single operator (HA), using an L4-9w probe, operated at 2-3 MHz to insonate the temporal windows bilaterally. The target vessels were the middle cerebral artery and the anterior cerebral artery. For each case, the PI was obtained after hemodynamic stability was achieved. As an internal control, we used a previously described optic nerve ultrasonography as a reflection of the ICP to objectively corroborate the trend seen in the PI. ,
A total of four patients were included. All patients were males with an age range from 22 to 35 years of age. All patients had closed head injuries with no surgical lesions on their initial imaging, defined as any extra-axial hematoma with mass effect. A median alcohol level blood alcohol concentration of 0.21 was detected (range: 0.19-28). The unifying clinical feature of all the patients was combative, aggressive behavior with one patient having tendency to loss of contact at times. The rest of secondary trauma server was noncontributory, and all patients were hemodynamically stable at the time of the TCD.
Radiological imaging was normal in one patient and showed scattered small contusions in the remaining 3, normally not associated with an elevation of the ICP, but in light of the agitation, elevated ICP could not be excluded, and the TCD was performed.
Trans-cranial Doppler was done in the ICU upon admission. In one patient, the PI was 0.7, denoting a normal result. In the second patient the PI was 1.2, which suggests an ICP of 12-14. In both patients, the optic nerve ultrasonography was normal. These two patients had a conservative approach geared to treating the agitation without ICP monitoring with resolution of the agitation overnight and normal neurological status and discharge from the ICU within 12 h of admission.
The third and fourth patients had PI of 2.1 and 2.3, respectively with a correlated ICP of 23-26. The optic nerve ultrasonography revealed a diameter of 5.6 and 6.7 mm, which is pathological correlating with elevated ICP. This TCD assessment resulted in an expedited ICP monitoring in the latter two patients. Insertion of the ICP monitors confirmed the elevated ICP, for which the TBI protocol was instituted.
Trans-cranial Doppler was introduced in 1982 by Aaslid as a tool to assess flow velocities in the vessels of the brain.  TCD gained popularity for its application in patients with subarachnoid hemorrhage and the diagnosis of vasospasm, with variability in adopting systematically due to the lack of consistency of TCD finding and the correlation with clinical outcomes. This led to diminished use of the TCD in the guidance of therapy. Recently, the mobile design of the current TCD machines, the refinement of the ultrasound probes and the development of reliable paradigms to calculate various indices renewed the interest in including TCD in the tools used in the Neurocritical care arena. The TCD PI was described first by Gosling, as the peak systolic velocity minus the end diastolic velocity divided by the mean flow velocity, irrespective of the angle of insonation. , In a simplistic physical sense, PI is thought to reflect the impedance of the environment around intracerebral vessels during the cardiac cycle. This makes the PI an acceptable parameter to server as an objective surrogate to estimate the ICP.
Although this case series is limited in number, we present a novel use for the PI in TBI patients. In these special TBI patients, the documented intoxication and low impact cerebral imaging creates the equipoise in terms of candidacy for invasive ICP monitoring options. The PI was predictive of the initial ICP and thus could be instrumental in future patients by objectively guiding the therapy through avoiding unnecessary ICP monitoring or expedites such monitoring when needed.
There are factors that can influence the PI determination. These include general hemodynamic and respiratory parameters such as tachycardia. To some extent, the extent of tissue compliance such that of aging brains or craneictomized patients (unpublished observation) and severe atherosclerotic or diabetic cerebrovascular disease that increases the rigidity of the vessels, thus seriously affecting the PI determination. , As a consequence, and to overcome the concern of the reliability of the TCD-PI assessment as a surrogate marker of ICP, we utilize the optic nerve ultrasonography as a second objective anatomical parameter to judge the pressure in the intracranial compartment. In this series there was found a good correlation between the TCD-PI assessment and the optic nerve sonography measurements, making the PI result more robust and more reliable.
The use of TCD-PI to prioritize or defer ICP monitoring in patients with confounded neurological exam is a novel one, based on the review of the available recent English literature. If used consistently, it would be a reliable tool to guide therapy for these vulnerable patients and allocate resources appropriately to them. This is not to undermine the value of serial neurological examination. So if the clinical condition is not progressing as predicted, repeat TCD-PI could offer grounds for repeat intracranial imaging and identify interval changes that could be missed given the confounded neurological exam. Hypothetically, this could be an excellent tool to "triage" patients in the field or in mass casualty situations. 
Although the data is prospectively collected, the limited number is a drawback to generalization of our findings. Besides, we employ resources as provided by tertiary level 1 trauma centers in urban metropolitan North American city. These resources could not be available or utilized in such a manner in other setups. These points raise the need for a multi-center; and potentially, multi-national trial to accommodate different TBI protocols and assesses the utility of the TCD parameters as adjuvant markers for decision making in TBI patients. Randomization of patients in light of established guidelines is a difficult proposal to justify, but an initial observational study is warranted to verify this concept and potentially incorporate it in our management guidelines.
The use of TCD PI is a useful adjunct to guide the use of ICP monitoring in intoxicated patients. It is useful to combine the PI determination with an anatomical evaluation of the optic nerve diameter to eliminate confounding factors in PI determination.
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