The Effect of Alveolar Recruitment Manoeuvre on Optic Nerve Sheath Diameter in Laparoscopic Hysterectomies

Laparoscopic total hysterectomy is the most common gynaecological surgical procedure after caesarean section. In laparoscopic total hysterectomy, intraabdominal pressure increases, venous return decreases, hypercarbia and acidosis may occur due to pneumoperitoneum due to CO2 insufflation and upright trendelenburg position (TP). Cerebral blood flow, intracranial pressure (ICP) and intraocular pressure (IOP) increase. One study showed that TP and an intraabdominal pressure of mmHg significantly increased ICP. CO2 insufflation into the abdominal cavity causes upward displacement of the diaphragm, resulting in an increased risk of regurgitation, decreased lung volumes and compliance, atelectasis, increased airway resistance and ventilation-perfusion mismatch. At the same time, combined with the effects of general anaesthesia, a decrease in partial arterial oxygen pressure (PaO2) is expected in patients. The alveolar recirculation manoeuvre (ARM), is based on the technique of opening atelectatic lung fields by keeping the airway pressure high for a while. This manoeuvre can be performed with methods such as PEEP, CPAP, and pressure-controlled mechanical ventilation. High PEEP application may cause an increase in ICP and a decrease in cerebral perfusion pressure by increasing intrathoracic pressure and decreasing cerebral venous return. Therefore, intracranial pressure monitoring should be performed especially in patients with PEEP above 8-10 cmH2O. Intraventricular and intraparenchymal measurements, which are the gold standard methods for ICP monitoring, are invasive procedures with various risks. Noninvasive methods such as cranial CT, brain MRI, transcranial Doppler, and measurement of optic nerve sheath diameter (ONSD) can also be used for ICP measurement. Ultrasonography of the optic nerve sheath diameter is an increasingly common method because it is noninvasive and can be performed at the bedside. The optic nerve sheath is the continuation of the transverse subar