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Head of bed elevation during prone lumbar surgery decreases IOP
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Ischemic optic neuropathy is a rare, but devastating complication of spine surgery and the risk of such a complication, according to the literature, is increased due to duration of surgery, amount of blood loss, prone positioning during the procedure or systemic factors.
Elevating the patient’s head 10° during surgery has been shown to significantly decrease IOP, one of the potential causes of ischemic optic neuropathy, according to a presentation by Scott D. Daffner, MD, at the Lumbar Spine Research Society Annual Meeting in Chicago.
Scott D. Daffner
“We found the elevation of the head of the bed significantly decreases intraocular pressure in patients undergoing prone lumbar spine fusion. The data do not really prove that this is going to prevent posterior ischemic optic neuropathy or postoperative vision loss. It is just too rare of an event. But, this is one step we can take that is fairly simple, safe and low impact as far as how it is going to affect how we do a procedure,” Daffner said.
Prone vs elevated head position
Daffner and colleagues analyzed 52 patients who underwent posterior lumbar fusion surgery at a single institution. The patients were randomized into an experimental group and a control group of patients. All patients were positioned in Gardner-Wells tongs with 10 pounds of traction on a Jackson table, which held the neck in a neutral alignment and kept pressure off the eyes, according to Daffner.
In the experimental group, the head of the bed was elevated to 10° of reverse Trendelenburg using the bed control (while maintaining neutral alignment of the head and neck). In the control group, the patients’ heads remained in a neutral position with the face parallel to the floor.
Using an applanation tonometer, one investigator made all the IOP measurements in the preoperative holding area, with the patient supine after anesthetic induction, with the patient prone after positioning on the table and at regular intervals throughout the procedure.
The investigators also measured the patient’s blood pressure and CO2 values.
Elevated position may be less risky
“What you can see is that IOP in both groups gradually increased over time, but there is a significantly lower intraocular pressure in the group where we had the head elevated 10°, and that started around 30 minutes into the case,” Daffner said.
Based on the study results, patients in the experimental group had statistically significantly less IOP than patients in the control group (P = .0014). The difference between the groups was first evident 30 minutes into each case and the reduced IOP persisted for the duration of the procedure.
- Reference:
- Daffner SD, et al. Paper #1. Presented at: Lumbar Spine Research Society Annual Meeting; April 9-10, 2015; Chicago.
- For more information:
- Scott D. Daffner, MD, can be reached at West Virginia University, PO Box 9196, 3400 HSC, Morgantown, WV 26506; email: sdaffner@hsc.wvu.edu.
Disclosure: Daffner reports he owns stock in Pfizer and Amgen and is a member of several North American Spine Society committees.
Perspective
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Vikas V. Patel, MD, MA, BSME
This devastating complication of perioperative vision loss can affect up to 0.03% of spine surgical patients. Although many attempts have been made to study the cause of ischemic optic neuropathy, it remains elusive. Though the American Society of Anesthesiologists has tracked this phenomenon in the Postoperative Visual Loss Registry, the direct cause is still only hypothesized to be an elevation of venous pressure and interstitial edema that hampers the perfusion of the optic nerve. This venous pressure increases as the head is held lower than the level of the heart, which is the case in many lumbar and thoracolumbar spine surgeries.
This study by Emery and colleagues provides valuable insight into the intraocular pressure of the eyes and the relative contribution of head position to this pressure. More importantly, this study provides a simple method to reduce intraocular pressure by simply extending the neck by 10°, thus raising the head. If and how much this will reduce the risk of blindness will hopefully follow in future studies.
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