ONSD Trajectory in Rebound ICH

Traumatic brain injury (TBI) is a major cause of morbidity and mortality worldwide. Cerebral edema and elevated intracranial pressure (ICP) are common secondary complications that require prompt management to prevent further neurological injury. Osmotherapy with hypertonic saline or mannitol is routinely used to reduce ICP; however, withdrawal or weaning of osmotherapy may be associated with rebound intracranial hypertension, which can worsen neurological outcomes if not recognized early.

Optic nerve sheath diameter (ONSD), measured by bedside ocular ultrasonography, is a non-invasive surrogate marker of raised intracranial pressure. Although ONSD has been shown to correlate with ICP in several clinical settings, the predictive value of serial ONSD measurements during osmotherapy weaning for identifying rebound intracranial hypertension has not been adequately investigated.

• Optic Nerve Sheath Diameter Ultrasonography (Diagnostic test): Serial ultrasonographic measurement of optic nerve sheath diameter (ONSD) will be performed bilaterally using a standardized transorbital ultrasound technique immediately before osmotherapy reduction or discontinuation (baseline) and at 4, 6, 12, and 24 hours after weaning. Additional measurements may be obtained if clinical deterioration suggestive of rebound intracranial hypertension occurs. ONSD measurements are performed for observational purposes only and will not influence routine clinical management.

Primary outcomes

• Prediction of rebound intracranial hypertension using serial ONSD measurements [Within 24 hours after osmotherapy reduction or discontinuation]

Secondary outcomes

• Mortality [From ICU admission until ICU discharge or death, assessed for up to 28 days.]: Death from any cause occurring during the patient's ICU stay following traumatic brain injury and during the study observation period.
• 2. Length of ICU Stay: [From ICU admission until ICU discharge or death, assessed for up to 28 days.]: The total duration of ICU admission measured in days from ICU admission until ICU discharge or death.
• Need for rescue ICP therapy: [Within 48 hours after osmotherapy weaning.]: Requirement for additional ICP-lowering interventions beyond restarting osmotherapy due to suspected or confirmed rebound intracranial hypertension. Rescue therapies include: (a) barbiturate infusion (thiopental or pentobarbital), (b) therapeutic hypothermia (target temperature ≤35°C), or (c) controlled hyperventilation (PaCO₂ <30 mmH
• Glasgow Coma Scale trajectory post-weaning [Measured at baseline (immediately before osmotherapy weaning), then at 4, 6, 12, and 24 hours after weaning (aligned with ONSD measurement time points). The primary analysis will use change in GCS from baseline to 24 hours as a continuous variable.]: Neurological status assessed using the Glasgow Coma Scale (GCS). The GCS total score ranges from 3 to 15, with higher scores indicating better neurological function. A decrease of ≥2 points from the baseline GCS score after osmotherapy discontinuation is considered neurological deterioration suggestive of rebound intracranial hypertension.
• Time to rebound intracranial hypertension [Assessed continuously during the first 48 hours after osmotherapy weaning. For patients who do not develop rebound, time will be censored at 48 hours.]: The interval (in hours) from complete osmotherapy discontinuation (T0) to the first documented episode of rebound intracranial hypertension. Rebound is identified by either: (a) decline in GCS of ≥2 points from baseline not attributable to other causes, or (b) worsening on brain imaging showing increased cerebral edema or mass effect.

Sex: All, ages: 18 Years to 80 Years

Inclusion Criteria:

* Adults (≥18 years) with blunt traumatic brain injury admission GCS ≤12
* (or GCS 13-15 with CT signs of elevated ICP including midline shift ≥5 mm, effaced cisterns, or significant cerebral edema)
* clinical decision to initiate 20% mannitol osmotherapy

Exclusion Criteria:

* Ocular conditions precluding ONSD measurement (glaucoma, prior ocular surgery,
* globe or optic nerve trauma,
* periorbital edema, orbital masses, optic nerve sheath cysts);
* planned decompressive surgery or evacuation of mass lesion within 48 hours; limitation of life-sustaining therapy; pregnancy; contraindications to mannitol (baseline sodium >155 mEq/L, osmolality >320 mOsm/kg, eGFR <30 mL/min); penetrating TBI; or concurrent spinal cord injury with shock.