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Abstract #19719 Published in IGR 9-4
Changes in intraocular pressure due to surgical positioning: Studying potential risk for postoperative vision loss
Walick KS; Kragh JE; Ward JA; Crawford JJSpine 2007; 32: 2591-2595
See also comment(s) by Paul Palmberg •
STUDY DESIGN: Parallel group design. OBJECTIVE: Compare the intraocular pressure responses in the prone flat versus prone Trendelenburg's position. SUMMARY OF BACKGROUND DATA: Postoperative vision loss (PVL) complicates approximately 0.05% of spine surgeries. Prone positioning is considered a risk factor because it increases intraocular pressure, which may decrease perfusion pressure to the optic nerve (perfusion pressure = mean arterial pressure - intraocular pressure [IOP]). The prone Trendelenburg's position is often used during spine surgery; however, its effect on optic nerve perfusion is unknown. The purpose of this study is to compare the IOP responses in the prone flat versus prone Trendelenburg's positions to determine if prone Trendelenburg's position also risks PVL. METHODS: Twenty subjects randomized into two groups. Group 1 lay in the prone flat position (0°). Group 2 lay in the prone Trendelenburg's position (-7°). IOPs were measured with a hand-held applanation tonometer while seated, 1 minute after assuming the group's position (Time 0), and at ten-minute intervals for 60 minutes. RESULTS: The differences in mean IOPs with respect to positions and time were significant (P = 0.0001, P = 0.000). There was a significant difference between sitting and all other times for both groups. In Group 1, there was a significant difference in IOP between Time 0 and all other times prone flat (P < 0.05). In Group 2, there was a significant difference in IOP between Time 0 all other times prone Trendelenburg (P < 0.05). CONCLUSION: IOP increases in the prone Trendelenburg's position, and when combined with other factors, may be a risk factor for PVL. The pathophysiology is discussed and suggestions for clinicians are made.
Dr. K.S. Walick, 134 Lamont Ave, San Antonio, TX 78209, USA. Kristina.walick@amedd.army.mil
Classification:
6.1.3 Factors affecting IOP (Part of: 6 Clinical examination methods > 6.1 Intraocular pressure measurement; factors affecting IOP)
