Correlation of Optic Nerve Sheath Diameter with External Ventricular Drain for measurement of Intracranial Pressure : An Observational Study

After getting institutional ethics committee  approval, CTRI no. and written consent of

patient’s nearest of kin, patients will be included in this study.The demographic data (age ,gender,

race),Glasgow Coma Score(GCS),pupillary size and reactions, vital signs(heart rate ,respiratory

rate,blood pressure,temperature) and CT scan findings will be recorded on admission to ITU. The

verbal score of GCS will be modified for intubated patients using the formula: Derived Verbal

Score=−0.3756+Motor Score×(0.5713)+Eye Score×(0.4233)[17].All patients will be sedated with

midazolam and fentanyl administered intravenously, according to the treating physician’s

discretion. Following the decision to place an ICP monitoring device (EVD) (by the attending

intensive care physician and neurosurgeon), the patients will be enrolled in this study.Ocular US

will be conducted with SonoSite Micromax (SonoSite Inc., Bothell, WA, USA) ultrasonography

(USG) machine. Each patient will be examined in the supine position using a linear USG probe of

10-5 MHz frequency to get ONSD at 3 mm posterior to the ocular globe. The probe will be applied

on the temporal part of the closed upper eyelid with coupling gel [18] [19]. For each patient,

investigator will perform two measurements on each eye in transverse plane. The resulting four

measurements will then be averaged to yield a mean ONSD to minimise intraobserver variability.

Initial US ONSD will be measured before placement of the EVD catheter. The opening pressure

after placement of the EVD catheter, will be used as the initial ICP, and Intracranial hypertension

will be considered present when the patient will be having ICP above 20 mmHg for a period of

time greater than 5 min.The investigator measuring the ONSD with ultrasonography will be

blinded to invasive measurements of ICP. The need for urgent life saving surgery i.e.

Decompressive Craniectomy will also be noted.