Prediction of Early Intracranial Hypertension After Severe Traumatic Brain Injury: A Prospective Study

Objective

This study aimed to assess the reliability of clinical features, noninvasive transcranial Doppler-related pulsatility index (PI) calculation, and optic nerve sheath diameter (ONSD) measured by ultrasound (US) and initial computed tomography (CT) scan (Marshall CT scan classification) in predicting the occurrence of early (<24 hours) high intracranial pressure (EHICP) (>20 mm Hg) after severe traumatic brain injury (TBI).

Methods

We conducted an observational prospective study in a level 1 trauma center. Patients were measured simultaneously for PI and US ONSD in the triage zone. Patients were categorized into 2 groups: those who had EHICP after TBI (EHICP+) and those who did not (EHICP−).

Results

Fifty-four patients were included; 32 were categorized as EHICP+ and 22 as EHICP−. PI >1.4 did not correlate with EHICP+ patients (69% vs. 46%, P = 0.09). US ONSD measurement was higher in the EHICP+ group (6.25; range, 6–6.95 vs. 5.7; range, 5.2–6.4; P = 0.005). The area under the receiver operating characteristic curve for US ONSD as a predictor of developing EHICP was 0.73 (95% confidence interval [CI], 0.59–0.86). CT ONSD measurement was higher in the EHICP+ group (6.71; range, 6.35–7.87 vs. 6.25; range, 5.8–6.93; P = 0.04). The area under the receiver operating characteristic curve for CT ONSD measurement as a predictor for EHICP+ was 0.67 (95% CI, 0.53–0.81). The diffuse injury III and IV categories in the Marshall CT scan classification were associated with the occurrence of EHICP (P = 0.004).

Conclusions

None of the clinical features or noninvasive tools assessed in this study enabled clinicians to strictly ascertain EHICP. Further studies are needed to establish their potential role before intracranial pressure probe insertion.

Introduction

High intracranial pressure (ICP) is associated with poor outcome after traumatic brain injury (TBI).¹ Continuous monitoring of ICP is recommended in cases of severe TBI to detect and treat early high intracranial pressure (EHICP) episodes.² A significant percentage of patients do not have access to this method of monitoring.3, 4 Moreover, EHICP occurring during the first hours posttrauma has been associated with an increased mortality rate after TBI.⁵ Noninvasive methods for high ICP detection have been proposed to shorten the delay in achieving more efficient and effective high ICP therapy. They primarily focus on developing strategies that enable nonspecialized centers to differentiate those patients that should be transferred to a neurocritical care unit (NCCU) from those that can be maintained in secondary care centers where they are awakened relatively shortly after injury without the need for ICP probe placement.

Optic nerve sheath diameter (ONSD) measurement using ultrasound (US), head computed tomography (CT) scanning, and magnetic resonance imaging have proved reliable in identifying high ICP.6, 7, 8, 9, 10 Recently, Robba et al.¹⁰ have interestingly described the combination of ONSD ultrasonography and venous transcranial Doppler (TCD) of the straight sinus for identifying high ICP in a mixed cohort of patients with acute brain injury. Given the unavoidable delays of invasive monitoring by ICP placement and because TCD is systematically performed in a repeated manner after severe TBI, our aim was to investigate the role of clinical signs, TCD, ONSD, and CT scan measurements to discriminate patients that subsequently experience EHICP (EHICP+) from those that do not (EHICP−). We selected patients with severe TBI who were exposed to EHICP because this population has an increased mortality rate.5, 11