Individual patient data systematic review and meta-analysis of optic nerve sheath diameter ultrasonography for detecting raised intracranial pressure: protocol of the ONSD research group.

BACKGROUND: The purpose of the optic nerve sheath diameter (ONSD) research group project is to establish an individual patient-level database from high quality studies of ONSD ultrasonography for the detection of raised intracranial pressure (ICP), and to perform a systematic review and an individual patient data meta-analysis (IPDMA), which will provide a cutoff value to help physicians making decisions and encourage further research. Previous meta-analyses were able to assess the diagnostic accuracy of ONSD ultrasonography in detecting raised ICP but failed to determine a precise cutoff value. Thus, the ONSD research group was founded to synthesize data from several recent studies on the subject and to provide evidence on the diagnostic accuracy of ONSD ultrasonography in detecting raised ICP. METHODS: This IPDMA will be conducted in different phases. First, we will systematically search for eligible studies. To be eligible, studies must have compared ONSD ultrasonography to invasive intracranial devices, the current reference standard for diagnosing raised ICP. Subsequently, we will assess the quality of studies included based on the QUADAS-2 tool, and then collect and validate individual patient data. The objectives of the primary analyses will be to assess the diagnostic accuracy of ONSD ultrasonography and to determine a precise cutoff value for detecting raised ICP. Secondly, we will construct a logistic regression model to assess whether patient and study characteristics influence diagnostic accuracy. DISCUSSION: We believe that this IPD MA will provide the most reliable basis for the assessment of diagnostic accuracy of ONSD ultrasonography for detecting raised ICP and to provide a cutoff value. We also hope that the creation of the ONSD research group will encourage further study. TRIAL REGISTRATION: PROSPERO registration number: CRD42012003072.

Ocular ultrasound to detect intracranial hypertension in trauma patients.

BACKGROUND: Increases in intracranial pressure (ICP) after head trauma require a rapid recognition to allow for adequate treatments. The aim of this study was to determine whether dilation of the optic nerve sheath, as detected by ocular ultrasound at the bedside, could reliably identify increases in ICP assessed with an intraparenchymal probe in adult head trauma patients. METHODS: Eleven head trauma injured adult patients admitted to the intensive care unit with a Glasgow Coma Scale score ≤8, with cerebral contusion confirmed by computed tomography scan, and that required invasive ICP monitoring, were enrolled in the study. ICP values ≤20 mm Hg were considered as normal. Patients with acute or chronic ocular lesion were excluded. Ten nontrauma intensive care unit patients, with no ICP monitoring, were enrolled as control group. Invasive arterial pressure was monitored, and optic nerve sheath diameter (ONSD) was assessed by ocular ultrasound in all the patients. RESULTS: Head trauma patients without intracranial hypertension had ONSD values, assessed by ultrasound, equivalent to those measured in control patients (5.52 mm ± 0.36 mm vs. 5.51 mm ± 0.32 mm). ONSD, instead, significantly increased to 7.0 mm ± 0.58 mm, when ICP rose in value to >20 mm Hg (p < 0.0001 vs. normal ICP and control). ONSD values were significantly correlated to ICP values (r = 0.74, p < 0.001). CONCLUSIONS: When ICP was higher than 20 mm Hg, the ONSD diameter increased, whereas when the ICP was below 20 mm Hg, the ONSD returned to values equivalent to those assessed in control nontrauma patients. Accordingly, ocular ultrasound may be considered as a good alternative for a rapid indirect evaluation of head trauma patients' ICP.