Patient Positioning Used in Surgery May Elevate Pressure

While the steep Trendelenburg position (>45 °) benefits surgical access to a patient’s abdominal and pelvic organs, it leads to a gradual, significant rise in intraocular pressure (IOP), which — if it persists — can cause anterior ischemic optic neuropathy and blindness. Previous research has found a correlation between rise in IOP and rise in mean arterial pressure (MAP) and end-tidal carbon dioxide (EtCO2).

The study, published in the Journal of Anaesthesiology Clinical Pharmacology, sought to uncover the relationship that the quantitative rise in IOP has with other confounding factors to better understand the causes of postoperative visual loss (POVL).

The observational study (NCT02646033) took baseline IOP value following intubation under anesthesia of 100 patients undergoing robotic prostatectomies or hysterectomies.

IOP was measured 10 minutes after intubation (time point 1), post pneumoperitoneum (time point 2), post steep Trendelenburg (time point 3), and the rest of the readings were taken 30 min apart. 

The mean IOP at time point 1 was 19.181 mm Hg OS and18.462 mm Hg OD, and IOP gradually rose as surgery progressed, reaching a maximum of 40.02 mm Hg OS and 41.543 mm Hg OD at time point 8 before patients were reversed to the supine position, the study explains. Ten minutes after returning to supine, IOP decreased to 21.419 mm HG OS to 20.671 mm Hg OD. MAP, EtCO2, and positive inspiratory airway pressure (PIP) remained consistent throughout surgery while IOP levels gradually and significantly rose, researchers found.

“This information is important, especially in patients suffering from glaucoma and ocular hypertension as it may convert an advanced surgical technique into an ocular nightmare for the patient along with medico-legal issues for treating physician,” the research says.

The researchers suggest conducting regular tonometric assessment of IOP both before and after patients undergo surgery in steep Trendelenburg position to avoid ocular complications.

The study was limited by the fact that it was conducted on small-duration surgeries, though it can be extended on patients kept in steep Trendelenburg position for several hours, and the use of the Schiotz tonometer while other technology options exist.

Reference

Goel N, Chowdhury I, Dubey J, et al. Quantitative rise in intraocular pressure in patients undergoing robotic surgery in steep Trendelenburg position: A prospective observational study. J Anaes Clin Pharm. Published online January 18, 2021. doi:10.4103/joacp.JOACP_96_20