Glaucoma comprises a group of related eye diseases that have a characteristic loss of optic nerve fiber layers and the appearance of optic nerve head excavation. Primary open angle glaucoma (POAG) accounts for 74% of glaucoma cases and is the second-leading cause of blindness in the world.1 Patients have decreased outflow through the trabecular meshwork, which results in increased intraocular pressure (IOP). It is estimated that POAG affects 2.2 million US citizens and that the number is expected to increase to 3.36 million by 2020.2
Prostate cancer is the second most common cancer in American men,3 and 80% of all radical prostatectomies performed in the United States are performed robotically.4 This surgical technique requires that patients be placed in steep Trendelenburg position, creating increased IOP3 and raising concern for postoperative visual loss (POVL).5–7 Despite the frequency with which these surgeries are performed, there are no current recommendations for the intraoperative monitoring and management of this expected increase in IOP.
Awad et al.7 report 2 patients with glaucoma scheduled for radical prostatectomy who were advised against this robotic technique performed in the Trendelenburg position in favor of an open technique in the horizontal position. Such concerns with respect to increased IOP are well warranted, and although POVL after robotic-assisted prostatectomy has not been described, concern regarding this possibility may preclude patients from having robotic-assisted surgery.
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Consent has been obtained from the patient for publication of protected health information in this case report. The patient has reviewed the case report and has given written permission for the authors to publish it.
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A 70-year-old, 182-cm, 76-kg man with POAG scheduled for a robotic-assisted radical prostatectomy had already lost vision in his right eye because of severe glaucoma and had visual field deficits in his left eye because of moderate disease.
Previous glaucoma treatment of his left eye included placement of a Baerveldt Implant 350 (Abbott Medical Optics, Abbott Park, IL) for aqueous filtration, pressure relief in 2002, and a laser trabeculoplasty in 2003. In 2011, his left eye developed a sudden increase in IOP, resulting in moderate progressive visual field loss, and the Baerveldt Implant was replaced. In 2012, the tubular portion of the left eye implant became exposed because of erosion through the conjunctiva; 2 revisions to cover the tube were unsuccessful, and the tube was removed. His left eye IOP was controlled subsequently within the normal range with the use of brimonidine 0.1% eye drops 3 times daily and dorzolamide-timolol eye drops twice daily.
Several weeks before the anticipated surgery date, his anesthesiologist became aware of the scheduled procedure and the severity of the patient’s glaucoma and raised concern regarding the effect of the steep Trendelenburg position on IOP required for robotic surgery with the resulting potential for further visual loss. There was full discussion of the concerns with the patient and consultations among the patient’s ophthalmologist, urologist, and anesthesiologist. The ophthalmologist recommended intraoperative monitoring of IOP and treatment of increased pressures with IV acetazolamide and mannitol as needed. The urologist was experienced in performing robotic prostatectomies and would attempt to keep surgical time to a minimum. The patient was asked to administer his usual dose of morning eye drops preoperatively.
General anesthesia was induced with propofol, and tracheal intubation was facilitated with rocuronium. Anesthesia was maintained using sevoflurane in 100% oxygen, and standard noninvasive monitors were used. After induction, baseline IOP in the supine horizontal position was 14 mm Hg. IOP was monitored every 15 minutes (the 75-minute time point was missed; Fig. 1). Measurements were taken by an experienced ophthalmology technician using the Tono-Pen XL Applanation Tonometer (Reichert Technologies, Depew, NY).
Intraperitoneal trocars were placed, and the Trendelenburg position was initiated in preparation for robotic surgery. Within 15 minutes, the IOP increased to 35 mm Hg at which time treatment was initiated with an IV bolus dose of acetazolamide 500 mg followed by a slow infusion of 100 g of 20% mannitol. With treatment, the patient’s IOP decreased to 17 to 20 mm Hg, despite his continuing in the Trendelenburg position. Total operative time was 120 minutes, after which IOP was measured at 10 to 12 mm Hg when the horizontal position was resumed.
The patient continued using his eye drops postoperatively, and a follow-up visit to the ophthalmologist 1 week later demonstrated normal IOP with no change in visual acuity.
POVL is a rare but devastating event.8 The incidence of permanent loss of vision after nonophthalmologic surgery is reported to be 0.0008%.9 In the setting of nonocular surgery, a possible risk factor for POVL is patient positioning.8 It is known that steep Trendelenburg position results in an increased IOP.3,5–7 Sanborn et al.5 reported on healthy subjects whose IOP increased to 35 to 40 mm Hg while in a head-down position. Eleven of the 19 subjects who were tested demonstrated reversible visual field defects. Friberg and Sanborn10 measured an approximate doubling of IOP in 16 subjects in the head-down position. These authors demonstrated reversible amplitude reductions in visual-evoked potentials associated with (head-down) gravity inversion-induced elevations in IOP and concluded that “gravity inversion activities pose potential risks to the eyes.” Nagaraju et al.6 investigated retinal ganglion cell dysfunction in glaucomatous DBA/2J mice. This mouse strain is a well-established model of spontaneous glaucoma. In this model, young mice (2–3 months of age) have normal IOP and optic nerves; however, baseline IOP increases with age and axonal damage in the optic nerve is apparent in 50% of eyes by 10 to 11 months.6 This study demonstrates both a gravity-induced reversible IOP increase and concomitant gravity-induced reductions in pattern electroretinogram (PERG) amplitude, which worsens with increasing age. Importantly, the head down–induced PERG reductions are more marked in older animals, thus demonstrating the increased sensitivity of the glaucomatous eye to gravity-induced, increased IOP. Notably, administration of mannitol to 11-month-old mice with increased baseline IOP and PERG amplitude reduction resulted in treatment-induced reduction in IOP, along with PERG amplitude improvement. In fact, Roth8 points out that acetazolamide decreases IOP and that diuretics, such as mannitol or furosemide, reduce edema.
Awad et al.7 describe 2 patients with glaucoma scheduled for robotic prostatectomy whose surgical plans were changed to avoid the effects of steep Trendelenburg position on IOP. In the case of our patient, when IOP increased after he was placed in the steep Trendelenburg position, administration of acetazolamide and mannitol resulted in a reduction in IOP even though the Trendelenburg position was continued.
Awad et al.3 report 33 patients without diagnosed eye disease undergoing robotic prostatectomy while in steep Trendelenburg position. They demonstrate elapsed time and end-tidal CO2 to be independent covariates for increased IOP. Our patient’s IOP increased by 18 mm Hg over baseline within 15 minutes of his being positioned head down. However, even though it appears to make good clinical sense and, without obvious harm to monitor and attempt to control the increased IOP, there is no conclusive proof of benefit.
Roth8 also cited abnormal optic nerve blood flow autoregulation as a possible contributor to POVL. Sehi et al.11 described mean optical perfusion pressure (MOPP) (i.e., 2/3 mean arterial pressure [MAP] − IOP) as the difference between MAP and IOP, and tracked diurnal changes in those measurements. Impaired optic nerve autoregulation8 may support the finding by Sehi et al.11 of greater diurnal variation in MOPP in patients with untreated glaucoma compared with healthy patients. In Table 1, measured changes in elapsed time, end-tidal CO2, MAP, MOPP, and IOP are noted for our patient.
In conclusion, we present the first reported case of a patient with significant open-angle glaucoma undergoing robotic surgery in whom IOP was monitored and successfully treated while maintaining steep Trendelenburg position. Further study is required before recommendations can be made for similar intraoperative management of patients with POAG undergoing surgery in the Trendelenburg position.
a Ghomi A. Robotics in practice: new angles on safer positioning. Contemporary OB/GYN 2012. Available at: http://contemporaryobgyn.modernmedicine.com/contemporary-obgyn/news/modernmedicine/modern-medicine-feature-articles/robotics-practice-new-angles. Accessed May 8, 2015.
b Jacobs DS, Trobe J, Sokol HN. Open-angle glaucoma: epidemiology, clinical presentation, and diagnosis. Available at: http://www.uptodate.com/contents/open-angle-glaucoma-epidemiology-clinical-presentation-and-diagnosis. Accessed May 8, 2015.
c NIH: National Eye Institute. Facts about glaucoma. Available at: https://www.nei.nih.gov/health/glaucoma/glaucoma_facts. Accessed May 8, 2015.
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