Assessment of Optic Nerve Sheath Diameter in Preeclamptic Pregnant Women Using Ultrasonography and Anesthetic Management

Overview

Preeclampsia is a serious condition associated with complications such as pulmonary edema, placental abruption, hemolysis, thrombocytopenia, and cardiac, renal, and neurological complications, occurring at a rate of 2.7-8% in pregnant women (1,2). Neurological complications are believed to be associated with reversible cerebral vasoconstriction syndrome (3,4) and/or posterior leukoencephalopathy syndrome (4,5,6), sharing a common pathophysiology. Cerebral edema is primarily vasogenic, potentially linked to hyperperfusion resulting from impaired cerebral autoregulation, blood-brain barrier disruption, and endothelial cell dysfunction. In some eclampsia cases, computed tomography and magnetic resonance imaging may reveal signs consistent with significantly increased intracranial pressure (ICP) (7). However, the true incidence of elevated ICP in preeclampsia is unknown, clinical symptoms are nonspecific, and interpretation, especially during pregnancy and preeclampsia, can be challenging (2). Cesarean section, currently one of the most frequently performed surgeries worldwide, is conducted in 21.1% of women (8). Anesthesia for cesarean section can be divided into neuraxial and general anesthesia. The choice of anesthesia technique in conditions that may increase intracranial pressure, such as cerebral edema, may vary based on balancing risks and benefits. Neuraxial analgesia and anesthesia are the first choice in healthy pregnancies, but may be contraindicated in cases with intracranial lesions or increased bleeding risk (9). The presence of focal neurological deficits may favor general anesthesia for cesarean delivery (10). General anesthesia in these patients may result in an increased hemodynamic response to laryngoscopy. Agents used in induction and maintenance can also affect cerebral autoregulation (11). Anesthesia induction and maintenance for these patients should be planned to minimize the increase in intracranial pressure. The optic nerve, a part of the central nervous system, is surrounded by a dural sheath and a subarachnoid space containing cerebrospinal fluid. Three millimeters behind the ocular globe, the optic nerve is solely surrounded by fat, and the dural sheath can retract within its fatty environment, particularly in conditions of increased pressure in the cerebrospinal fluid (2). Recent clinical studies have reported that ultrasonographic measurements of the optic nerve sheath diameter (ONSD) are correlated with increased intracranial pressure symptoms and may serve as a non-invasive reliable indicator of ICP (12,13). Studies have reported high inter-observer reliability for ONSD measurements (14,15). ONSD measurement is easy, repeatable at the bedside, rapid, inexpensive, and does not involve radiation. Compared to healthy pregnant women, preeclamptic women are considered to have higher intracranial pressure during the childbirth process. Anesthetic management for delivery in these women can be complex and controversial. The aim of this study is to evaluate ultrasonographic measurements of optic nerve sheath diameter during the perioperative period, independent of anesthesia management, in healthy and preeclamptic pregnant women undergoing cesarean section. We believe that these assessments will contribute to more reliable anesthesia planning for preeclamptic pregnancies.