Optic Nerve Sheath Diameter as A Predictor of Early Tacrolimus Neurotoxicity After Living Donor Liver Transplantation

Neurotoxicity is mainly associated with tacrolimus and cyclosporin, amounting to 10 - 30% for CS and up to 32% for tacrolimus.(2) . Sirolimus, everolimus, and mycophenolate mofetil lack the neurotoxicity of calcineurin inhibitors (3-4).

Neurotoxicity mostly occurs in the early postoperative period increasing morbidity, mortality and hospital and intensive care stay. Neurotoxicity has variable manifestations and mainly affects the CNS. They are usually divided into minor manifestations as tremor, headache, insomnia and paraesthesia or major encephalopathy, akinetic mutism, seizures, speech disorders, polyneuropathy, myopathy, pseudobulbar palsy and even stroke. (2) The main pathogenesis of calcinurin inhibitors neurotoxicity appears to be fluid extravasation (vasogenic edema) due to disruption of blood brain barrier, not cell destruction (cytotoxic edema).(5) During liver transplant operation there are changes in the intracranial pressure and cerebral perfusion pressure especially during reperfusion that may affect the integrity of blood brain barrier. (6) There are multiple methods for monitoring of intracranial pressure invasive or non -invasive. The invasive method remains the gold standard for monitoring of intracranial pressure but there is a controversy about its use in liver transplantation as it may be complicated by bleeding and infections (7).

Also there are a multiple non-invasive methods for monitoring of ICP. Ultrasonographic measurement of the optic nerve sheath diameter (ONSD) was introduced recently as a useful noninvasive method for evaluating ICP. ONSD demonstrated a good correlation with the ICP level in many previously published studies. (8,9) Rajajee et al. found that the optimal cutoff of ONSD for the detection of an acutely increased ICP > 20 mm Hg was greater than 4.8 mm. (10) We hypothesize that the absolute value or the changes of ONSD during different stages of living donor liver transplantation operation may predict occurrence of early calcinurin inhibitor neurotoxicity (CNIN).We will investigate whether the absolute value or changes of ONSD during different stages of living donor liver transplantation operation may be a predictor of early calcinurin inhibitor neurotoxicity in the first month post liver transplantation. This is a prospective observational cohort study that will be conducted to all adult patients of both sex undergoing living donor liver transplantation operation at Gastro-Intestinal Surgical Centre (GISC), Mansoura university Hospitals, Mansoura, Egypt over the period covering more than 100 consecutive cases. After Institutional review board approval, we will secure informed consents from all included patients during the preoperative visits.

Anesthesia and surgery techniques will be done according to our center's protocol.(11)

Reperfusion: