The Effect of Body Inclination During Prone Positioning on Intraocular Pressure in Awake Volunteers: A Comparison of Two Operating Tables

Abstract

Visual loss is a rare, but catastrophic, complication of surgery in the prone position. The prone position increases intraocular pressure (IOP), which may lead to visual loss by decreasing perfusion of the anterior optic nerve. We tested whether the reverse Trendelenburg position ameliorates the increase in IOP caused by prone positioning. Furthermore, we compared two prone positioning set ups. The IOP of 10 healthy awake volunteers was measured in the prone position at 3 different degrees of inclination (horizontal, 10 degrees reverse Trendelenburg, and 10 degrees Trendelenburg) and in the sitting and supine positions in a randomized crossover study comparing the Jackson table and the Wilson frame. In a given eye, all prone IOP values (median [25th-75th percentile] exceeded those of the sitting (15.0 mm Hg [12.8-16.3 mm Hg]) and supine (16.8mm Hg [14.0-18.3 mm Hg]) positions. IOPs in the reverse Trendelenburg, horizontal, and Trendelenburg positions were 20.3 mm Hg (16.3-22.5 mm Hg), 22.5 mm Hg (19.8-25.3 mm Hg), and 23.8 mm Hg (21.5-26.3 mm Hg), respectively (P < 0.001 versus reverse Trendelenburg; dagger P < 0.001 versus horizontal). The reverse Trendelenburg position ameliorated the increase in IOP caused by the prone position. Furthermore, the reverse Trendelenburg position decreased the number of grossly abnormal IOP values (>23 mm Hg) by 50% and 75% compared with the prone horizontal and Trendelenburg positions, respectively. The prone positioning setups did not differ in their effect on IOP. The increase in IOP caused by prone positioning was ameliorated by the reverse Trendelenburg position and was aggravated by the Trendelenburg position. The short time period between changes in position and changes in IOP suggests an important role for ocular venous pressures in determining IOP. Therefore, IOP can be beneficially manipulated by operating table inclination in the prone position.

Position-Related Variability of CSF Opening Pressure Measurements

“…9 Other authors have shown that the prone position increases intraocular pressure, which correlates with central venous pressure, implying that prone positioning increases venous pressure. 10 These findings suggest that the prone position leads to increased CSF pressure by increasing central venous pressure. Our current study adds to this previous literature, because we observed increased CSF OP in the prone position.…”

Efeito da rotação da cabeça na pressão intraocular em decúbito ventral: estudo randomizado

“…Head elevation in prone position (reverse Trendelenburg) ameliorated the increase in IOP in prone fl at 6 . Ozcan et al 6 studied the effect of body inclination during prone positioning on intraocular pressure in awake volunteers. They showed that a 10 th reverse Trendelenburg position ameliorated the increase in IOP caused by the prone position in awake volunteers.…”

“…Some studies have shown that Trendelenburg position in prone resulted in further increase in IOP compared to prone position 1,6 . Head elevation in prone position (reverse Trendelenburg) ameliorated the increase in IOP in prone fl at 6 .…”

“…They showed that a 10 th reverse Trendelenburg position ameliorated the increase in IOP caused by the prone position in awake volunteers. Although that study did not include all the factors that might have affected the IOP in an operative setting, it suggested a strategy to positively infl uence the IOP by changing the operating table inclination for patients in the prone position 6 . The current study is original in that it is the fi rst study to compare IOP of subjects in prone position with head rotation 45 o laterally.…”

“…The risk of postoperative vision loss in patients undergoing spine surgery in prone position is 0.05% 1 . Some studies investigated the effects of head elevation in prone position to ameliorate the increase in IOP and had concluded that head elevation may cause a decrease in IOP 6 . Although primary open angle glaucoma is a bilateral disease, glaucomatous defects are usually asymmetrical between the two eyes and one eye is more affected than the fellow eye.…”