The Effects of Lateral 45° Downward Position on the Optic Nerve Sheath Diameter

Overview

Trendelenburg position and carbon dioxide (CO2) pneumoperitoneum are in association with increased intracranial pressure (ICP) reflected by the optic nerve sheath diameter (ONSD). Measurement of ONSD by ultrasound (US) guidance can be used in the diagnosis of ICP. The investigators interrogated the effects of lateral 45° downward position and CO2 insufflation on ONSD in patients undergoing laparoscopic transperitoneal nephrectomy.

Transperitoneal laparoscopic nephrectomy is a popular and increasingly used alternative to the laparoscopic retroperitoneal approach because of benefits such as minimal invasion, the transperitoneal path provides a larger working space and familiar anatomic landmarks. This technique requires a steep (35° to 45°) lateral downward (SLD) position and a CO2 pneumoperitoneum. SLD may lead to pathophysiological changes such as pulmonary dysfunction with the formation of atelectasis and increasing airway pressure as well as ocular complications. These are firstly reported 2 patients with bilateral ischaemic optic neuropathy (ION) after a da Vinci robotic-assisted procedure. SLD has raised concerns that prolonged elevation of venous pressure in the head may increase the risk of developing ION. However, a few investigations have yet been made into intraoperative changes in intraocular pressure (IOP) and optic nerve sheath diameter (ONSD) - correlating with intracranial pressure (ICP) - and their adverse ocular effects. The operative conditions get better the steeper the positioning, providing an excellent intraabdominal view and probably less bleeding. The hypothesis of the study is that patients placed in SLD for several hours have a high risk for ocular changes and peri- and postoperative complications. The aim of this study was to investigate the influence of capnoperitoneum and permanent 45° SLD on IOP and ONSD in patients undergoing laparoscopic transperitoneal nephrectomy. The investigators also analyzed the hemodynamic and respiratory parameters, duration of surgery during laparoscopic nephrectomy. Perioperative and postoperative complications were also recorded.

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