Optic Nerve Sheath Diameter Measurement

The ophthalmic artery Doppler has been recently proposed as a potential "soft marker" for placental insufficiency in retrospective and observational studies, with similar clinical significance with respect to Uterine Artery (UA) Doppler evaluation and it is currently being investigated as an adjunctive clinical instrument to predict pre-eclampsia (PE) occurrence. Placental insufficiency strictly correlates with intrapartum fetal adverse outcomes and a concomitant induction of labor, alone, may further increase the hypoxic stress on the fetus during labor. This can be reflected by cardiotocographic alterations during labor, ultimately leading to emergency cesarean deliveries or instrumental vaginal deliveries. Despite great advancements in understanding various maternal-fetal pathologies, the investigators are still not able to properly detect fetuses that are at higher risk for intrapartum compromise among those receiving an induction of labor. Therefore, the aim of this prospective study is to investigate any potential association between altered ophthalmic artery Doppler PSV ratio measured before labor induction in at-term, pregnant patients with intra-partum fetal compromise. Furthermore, the investigators aim to also measure an additional parameter that is the optic nerve sheath diameter (ONSD) - an indirect measure of intracranial pressure - before and after the second stage of labour, with the aim of studying its physiology during and after delivery.

The aim of this study to compare the efficacy of hypertonic saline and mannitol in reducing intracranial pressure, as assessed by serial optic nerve sheath diameter (ONSD) ultrasound measurements, in patients with traumatic brain injury.

The aim of this study is to evaluate the effects of different carbon dioxide gas insufflation pressures on the ultrasound-guided optic nerve sheath diameter in patients undergoing laparoscopic cholecystectomy and to determine the possible relationship between these changes and intracranial pressure. The study aims to gain a better understanding of the neurophysiological effects of gas pressures used during laparoscopic surgery and to obtain scientific data aimed at improving patient safety.