Optic nerve sheath ultrasound for bedside diagnosis of intracranial hypertension in the ICU: A single institution experience

Lisandro Montorfano, MD, Federico Perez Quirante, MD, Alejandro Cracco, MD, Hira Ahmad, MD, Rajmohan Rammohan, MD, Nisha Dhanabalsamy, MD, Alex Ordonez, MD, Emanuele Lo Menzo, MD, PhD, FACS, FASMBS, Samuel Szomstein, MD, FACS, FASMBS, Raul J Rosenthal, MD, FACS, FASMBS. Cleveland Clinic Florida

Introduction: The aim of our study was to evaluate the ultrasonographic modifications observed on the optic nerve sheath diameter in patients in the surgical ICU.

Material and Methods: We prospectively collected data from patients in the ICU between March and August 2015. The optic nerve sheath diameter (ONSD) was measured sagittally with a 12-MHz transducer. The ONSD was measured 3 mm posterior to the globe. Two measurements were averaged. The measurements were obtained the second day of admission in the ICU. We considered normal optic nerve sheath measures up to 5.0 mm in diameter. If the patient had an abnormal measurement the optic nerve sheath diameter was re-measured before discharge. Student’s T test was used to asses the statistical significance of our findings.

Results: A total of 12 patients admitted to the ICU were included in this study. The mean age of this population was 60 years old (range 45–79). The mean weight and body mass index was 82.5 kg (range 30– 122.47 Kg) and 31 kg/m2 (range 23– 43). The mean systolic blood pressure was 116 mmHg (range 91- 152) and the mean diastolic blood pressure was 63 mmHg (range 41- 97).

When measuring the optic nerve sheath diameter for the first time we found that 6 patients (50%) had a measurement lesser than 5.0 mm and 6 patients (50%) had a measurements greater than 5.0 mm. The mean optic nerve sheath diameter was 4.69 mm (range 4.11-4.97) for the first group and 6.09 mm (range 5.51-6.55) for the second group (p<0.001). The second group included 2 patients that were intubated (16.6%), 1 patient that had sepsis (8.3%), 1 patient had foregut surgery due to esophageal cancer (8.3%) and 2 patients had neurologic complications, such as a CVA (8.3%) and cerebral aneurysms (8.3%). The optic nerve sheath diameter was remeasured in those patients that had a first measurement above 5.0 mm. The second ONSD measurement was 4.79 mm in average. (range 3.77- 5.5). The difference between the first and second measurement was statistically significant (p= 0.02)

Conclusion: It is possible to detect raised ICP by measuring the Optic Nerve Sheath Diameter (ONSD) using ultrasound in the ICU. Changes in the ONSD due to acute events reflect a temporary and reversible increase in the ICP in the ICU. Further studies are necessary to assess the benefit of this additional monitoring modality in terms of mortality or morbidity in these patients.