Monitoring Changes in Noninvasive Intracranial Pressure Markers Using Ocular Ultrasonography in Adults Undergoing Ventriculoperitoneal Shunt Surgery: A Prospective Observational Study

Optic nerve sheath diameter (ONSD) reflects the change in cerebrospinal fluid pressure. ONSD/eyeball transverse diameter (ETD) is a new ultrasonic indicator, devoid of influences of age, gender, and ethnicity. We studied the changes in the ocular sonographic parameters: ONSD, ETD, and ONSD/ETD ratio in patients of hydrocephalus before and after ventriculoperitoneal (VP) shunt placement and the factors associated with their changes. The parameters of ONSD, ETD, and ONSD/ETD were measured in 40 patients by a single observer with Sonosite machine at three time points: before induction of anesthesia, immediately after extubation, and at 24 hours of extubation to detect changes. We examined the association between changes in clinical characters before and after shunt insertion with the ocular sonographic parameters. ONSD at 24 hours after extubation, that is, 5.29 ± 0.26 mm, was substantially lower compared to the baseline value of 5.40 ± 0.31 mm (p < 0.01). Mean ONSD/ETD ratio at 24 hours after extubation, that is, 0.228 ± 0.01, was significantly reduced compared to the baseline value of 0.233 ± 0.01 (p < 0.01). No differences in the parameters were observed between the baseline and immediately after extubation. We did not observe any substantial changes in ETD across the three time points. The reduction in ONSD and ONSD/ETD parameters from baseline to 24 hours was significantly associated with headache (p = 0.00) and nausea and vomiting (p = 0.002). ONSD and ONSD/ETD ratio, both useful bedside parameters, reflect intracranial pressure (ICP) changes in patients undergoing VP shunt surgery. A decrease in the postoperative value of these parameters compared to preoperative values was consistent with relief of clinical symptoms, reflecting a reduction in ICP from successful surgery.