Patients undergoing robotic-assisted laparoscopic radical prostatectomy (RALRP) are placed in a steep Trendelenburg position along with carbon dioxide abdominal insufflation to improve the surgeon’s visualization during the procedure. It is well known that these maneuvers are associated with an increased intraocular pressure (IOP).1 Because aqueous humor drains into the episcleral venous circulation, an increase in central venous pressure in the head-down position results in impaired aqueous outflow and an increase in IOP. Choroidal expansion may also be a contributing factor to the increase of IOP in this body position. Previous studies have reported an average peak IOP change of 5 to 15 mm Hg after prolonged steep Trendelenburg positioning, and 25% of normal individuals experience IOP ≥ 30 mm Hg.1–3
The transient increase in IOP in patients undergoing RALRP is likely inconsequential for most patients. Many ocular procedures produce similarly increased IOP, and sequelae rarely develop. An IOP ≥ 30 mm Hg was observed in 24% of patients 24 hours after pars plana vitrectomy,4 and 26% of patients undergoing cataract extraction experience IOP ≥ 35 mm Hg within 24 hours postoperatively.5 Treatment with medications used to control IOP is not routinely used in patients without glaucoma undergoing these ocular procedures. However, a diagnosis of glaucoma implies that pressure-induced damage has already developed in the optic nerve such that even a temporary increase in IOP in patients with glaucoma raises concern and may prompt prophylactic treatment with acetazolamide, mannitol, or timolol at the time of ocular surgery.
Various forms of glaucoma exist, and they present with different degrees of increased IOP. Terminology can be confusing, resulting in several classifications: acquired versus congenital, high IOP versus normal pressure, acute versus chronic, and open angle versus narrow or closed angle. Chronically increased IOP produces slow damage to the optic nerve over the course of years in most patients with glaucoma, including those with primary open-angle glaucoma (the glaucoma type of this case report’s subject). The effect of transient but significantly increased IOP in patients with chronic glaucoma is not well known. More rapid glaucoma-related optic nerve damage may develop over days to weeks in acute forms of glaucoma associated with markedly increased IOP (usually 40–60 mm Hg), such as acute angle-closure glaucoma. In normal-tension glaucoma, damage to the optic nerve occurs with IOP in the clinically normal range. It is unclear why the optic nerve is more vulnerable to pressure-induced injury in normal-tension glaucoma, but it is a common disease accounting for 24% of all glaucoma in the United States6 and 92% of open-angle glaucoma cases in Japan.7
As speculated by Lee et al.,8 prophylactic treatment with glaucoma medications during RALRP seems advisable in select patients, especially those with normal-tension glaucoma and/or advanced disease. An incremental worsening of glaucoma has a higher risk of being visually significant in a patient with advanced disease.9 In addition, patients with normal-tension glaucoma have demonstrated a greater sensitivity of their optic nerves to IOP-induced damage, so preventing even a transient increase in IOP seems desirable in the subgroup of patients with glaucoma. Longer procedures seem to increase the likelihood of a substantial IOP increase, and treatment seems warranted when the operative time exceeds 5 hours.1–3 However, patients who have previously undergone successful glaucoma surgery (i.e., trabeculectomy or tube shunt implantation) are more protected against the effects of increased IOP with Trendelenburg positioning, so prophylactic treatment may not be needed.
Specific attention should be directed toward identifying any history of glaucoma during the preoperative evaluation of patients in whom RALRP is planned. If the patient has a known diagnosis of glaucoma, we concur with Lee et al. that a discussion of the perioperative management with the treating ophthalmologist is recommended. Interventional therapy and serial intraoperative IOP measurements are not warranted for the majority of patients with glaucoma for the reasons elucidated earlier. Targeted treatment with IV acetazolamide and mannitol may be appropriate for a select subset of patients with glaucoma, including those with severe disease, greater optic nerve sensitivity, normal-tension glaucoma and when prolonged operative duration (>5 hours) is anticipated. The anesthesiologist must also weigh the concomitant risks of exposing an elderly patient with cardiopulmonary comorbidities to osmotic agents, particularly mannitol. In these patients, an open prostatectomy procedure may be considered if there is a high level of concern vis-à-vis the increased IOP during RALRP.
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