Background:
Prostate cancer is the second most common cancer in American men, and 80% of all radical prostatectomies in the United States are performed robotically. It is known that robotic surgery, which is associated with pneumoperitoneum and steep Trendelenburg positioning, significantly raises intraocular pressure (IOP). Intraperitoneal carbon dioxide due to insufflation elevates choroidal blood volume. In addition, since aqueous humor drains into the episcleral venous circulation, elevated central venous pressure (CVP) due to head-down positioning impairs aqueous outflow. In one study of 33 patients, IOP was found to reach an average peak level 13 mm Hg higher than that prior to anesthetic induction. Thus, special concern is raised when patients with primary open-angle glaucoma, who have elevated IOP at baseline, undergo robotic radical prostatectomy.
Case Description:
We present a case of a 69-year-old male with prostate cancer, hypertension, and open-angle glaucoma who underwent robotic radical prostatectomy over a 4-hour period at our affiliated institution. His home medication regimen included timolol-dorzolamide eye drops, which reduce aqueous secretion by the ciliary body. Preoperatively, in order to prevent pupillary dilation, we medicated bilateral eyes with neostigmine eye drops. Intraoperatively, opioids (intravenous fentanyl and morphine) were also given for the dual purpose of pain control and the prevention of mydriasis. To reduce orbital edema, a steady infusion of mannitol and a bolus of furosemide were administered. To keep CVP low, a nitroglycerin infusion was continued throughout the case. A low-dose propofol infusion also supplemented our anesthetic maintenance with isoflurane, as propofol has been shown to reduce IOP by inhibiting arginine vasopressin (AVP) release. Furthermore, in order to prevent the choroidal vasodilation associated with hypoxemia/hypercarbia, we followed ABGs and adjusted ventilator settings as needed, keeping the PaCO2 between 35 and 40 mm Hg. Peak inspiratory pressure (PIP) and PEEP were also kept low, as some studies have shown an association with increased PIP, PEEP, and elevated IOP. Finally, we prevented coughing, bucking, and vomiting – all of which can significantly increase IOP – by ensuring adequate neuromuscular relaxation prior to intubation, titrating propofol prior to emergence, and by administering anti-emetics (dexamethasone and ondansetron). As a point of interest, we were aware that giving intravenous acetazolamide intraoperatively has been described as a way to prevent increases in IOP. Carbonic anhydrase inhibitors interfere with the production of bicarbonate, which is necessary for the synthesis of aqueous humor. However, we opted not to use acetazolamide due to the risk of metabolic acidosis and the choroidal vasodilation that could ensue. Our patient’s vision remained intact both immediately after and during follow up throughout his 3-day hospitalization, as well as one month after discharge, when he returned for another procedure.
Discussion:
Increased IOP and potential visual dysfunction is a real concern in patients with glaucoma undergoing robotic surgery. We prevented this in our case by preventing pupillary dilation, reducing orbital edema, lowering CVP, preventing hypoxemia/hypercarbia, preventing sudden increases in PIP and PEEP, and by preventing coughing, bucking, and emesis.
