OBJECTIVE - To determine whether there was a correlation between tonometric measurements of the intraocular pressure and transducer measurements of the intracranial pressure in the acute setting, and whether intraocular pressure can be used as a surrogate measure of intracranial pressure. Children with traumatic brain injuries commonly develop increased intracranial pressure requiring surgical placement of a pressure transducer to measure the intracranial pressure during the acute recovery period. The increased intracranial pressure may cause engorgement of the orbital compartments via dilation of the episcleral veins and manifest as increased intraocular pressure.
DESIGN - Prospective study.
SETTING - Tertiary academic pediatric intensive care unit.
PATIENTS - Children admitted with severe traumatic brain injury.
INTERVENTIONS - Tonometric intraocular pressure measurements.
MEASUREMENTS AND MAIN RESULTS - We performed an Institutional Review Board-approved, prospective study on 36 children (age range, 2.9-15.1 yrs) with traumatic brain injuries, requiring intracranial pressure monitoring. A total of 274 intraocular pressure measurements were made after placement of the pressure transducer, and concordance between the sites of injury and measurement was documented. The average age of the patients was 8.3 yrs. The mean intraocular pressure, intracranial pressure difference was -0.5 +/- 0.68 cm H2O, and the variance was 29.88 (sd, 5.47). The 95% confidence interval was between -11.22 and 10.22. With concordance between the sites of measurement and injury, the mean IOP, intracranial pressure difference was -0.02 +/- 0.61 cm H2O (variance, 23.28; sd, 4.82; 95% confidence interval, - 9.47 to 9.42). Concordance reduced the variance of the intraocular pressure, intracranial pressure discrepancy by 20.3%. The Pearson intraocular pressure-intracranial pressure regression coefficient and the Krippendorff's alpha reliability estimate analyses indicated good agreement. The patient's age or Paco2 did not influence the intraocular pressure, intracranial pressure difference. Using 20 cm H2O as a normal intracranial pressure cutoff, the intraocular pressure had a specificity of 0.7 and sensitivity of 0.97; with concordance, the values improved to 0.78 and 0.96, respectively.
CONCLUSIONS - Tonometry is a useful screening surrogate measure of intracranial pressure in children with traumatic brain injuries, but seems to lack the accuracy necessary for close management of intracranial pressure in the acute posttraumatic period.