Effect of Intravenous Administration of Mannitol on ONSD in Patients With Raised ICP

Effect of Intravenous Administration of 20% Mannitol on the Optic Nerve Sheath Diameter(ONSD) in Patients With Raised Intracranial Pressure

Osmotherapy with mannitol has been a common practice in patients with raised ICP. Monitoring its effect on ICP can be performed invasively and non-invasively. Due to a validated correlation between invasive ICP monitoring and ONSD measurement, it can be a tool to monitor acute and long term effects of osmotherapy non-invasively on ICP. This study examines the acute changes in sonographically measured ONSD brought about by the administration of mannitol. This can correlate with the changes in ICP in such patients and can be utilized as a tool for decision making/ point-of-care utility.

This is a prospective cohort based observational study including 40 patients admitted in the adult ICU at our center diagnosed as either a case of TBI/ acute stroke/ intracranial hemorrhages with a mean screening ONSD of more than 5mm under mannitol osmotherapy. ONSD were measured by a high frequency linear array probe (>10 Hz) at the time of screening. Mannitol was then administered at doses prescribed by the treating physician over 20-30 minutes via a dedicated intravenous line. ONSDs were measured again at 30, 60 and 120 minutes after completion of administration of mannitol. Demographic data, baseline ventilator parameters of patients on mechanical ventilation, GCS and mean arterial pressure at each time points were recorded. Comparison of variables at these time points were made.

Inclusion Criteria:

• age > 18 years
• diagnosed as a case of TBI/ acute stroke/ intracranial hemorrhages
• screening mean ONSD > 5 mm
• under osmotherapy with mannitol in standard doses (0.25 - 1 gm/kg)

Exclusion Criteria:

• baseline ocular pathology like tumors, Graves' disease and sarcoidosis
• previous ocular surgery
• Decompressive cranial surgery