Avaliação ultrassonográfica do diâmetro da bainha do nervo óptico de pacientes com traumatismo cranioencefálico grave e sua correlação com técnica invasiva

Abstract

Introduction: increased intracranial pressure (ICP) may deteriorate the clinical conditions of traumatic brain injury (TBI) patients. For this reason, its identification and prompt treatment could modify morbidity and mortality in these set of patients. Among several described techniques to estimate intracranial pressure, one has emerged as non-invasive and easily performed at bedside: ultrasonographic measurement of optic nerve sheath diameter (ONSD). Method: 40 severe TBI patients were included and they were admitted to a level I trauma hospital. They were underwent intraparenchymal device placement, sedated and on mechanical ventilation. After a family member have signed informed consent, ultrasonographic measurement of ONSD was performed and compared with intracranial pressure invasive measurement in order to evaluate association between them and determine a threshold value. People under eighteen years old, penetrating TBI and direct ocular trauma were excluded from this study. Results: 53 ONSD measurements were performed in all patients; 44 measurements (83%) were in patients whose intracranial pressure was < 20 mmHg and nine measurements (17%) in those whose intracranial pressure was ≥ 20 mmHg. ONSD mean value of the group with intracranial pressure < 20 mmHg was 5.4 mm ± 1.0 and while that of the group with intracranial pressure ≥ 20 mmHg was 6.4 mm ± 0.7 (p = 0.0026). There was not statistically significant diference between left and right eyes measurements. Positive and statistically significant correlation was noted between ultrasonographic measurement of ONSD and invasive measurement. On the statistical analysis of ROC curve, the best cut-off was 6.18 mm, with a 77.8% sensitivity and 81.8% specificity. Conclusion: this was the first study in Brazil to evaluate the ONSD measurement in a quantitative analysis and the study with largest sample with severe TBI patients only underwent intracranial pressure invasive measurement already published. From this article, it is possible to conclude a positive correlation between ultrasonographic measurement of ONSD and intracranial pressure invasive measurement with a threshold of 6.18 mm. This validation does not intend to replace the invasive technique, however it demonstrates that this non-invasive technique might be a complementary tool in the neurocritical care when there are not available scans, medical supplies or neurosurgical team.