A Japanese study shows that intraocular pressure (IOP) increases during robotic-assisted radical prostatectomy with the patient in a steep Trendelenburg position, but this is not associated with an increased risk for postoperative complications or changes in visual function.
Previous concerns had been raised that the surgical position, which requires the head to be 23–45° lower than the feet, could result in postoperative ocular complications such as ischemic optic neuropathy.
However, researchers Yuko Hoshikawa (St Luke’s International Hospital, Tokyo) and colleagues found that although mean IOP nearly doubled from 13.2 mmHg before surgery to a maximum of 24.0 mmHg during, there were no significant changes in visual acuity, mean retinal nerve fiber layer thickness, or other ocular complications after surgery.
The study included 31 patients undergoing robotic-assisted radical prostatectomy in a 23° head-down position, who were in surgery a mean of 4.57 hours. The researchers took measurements from the left eye of each patient on the day of the operation, and when they were awake while supine (baseline), immediately after anesthesia induction while supine, hourly during surgery, immediately after return to a supine position, and 30 minutes after awakening.
They found that IOP was significantly lower than baseline immediately after anesthesia but then rose gradually during surgery, reaching a peak at 4 hours. However, it returned to baseline levels within 30 minutes postoperatively.
The mean change from baseline was –8.1 mmHg after anesthesia, +3.6 mmHg 1 hour into surgery, +4.5 mmHg at 2 hours, +4.4 mmHg at 3 hours, and +5.3 mmHg at 4 hours.
Writing in the British Journal of Ophthalmology, Hoshikawa and team say that theirs is the first report including ocular complications following this type of surgery. They suggest that their observed changes in IOP, which have also been reported in a prior study, are likely due to an increase in central venous pressure due to gravity, and may also be influenced by the absorption of intraperitoneal CO2 during surgery, which can increase choroidal blood volume.
The researchers note that their study is limited by a small sample size, and they also suggest that the impact of IOP changes on ocular complications during surgery of a longer duration and at more extreme positioning angles should be explored.
In the meantime, they conclude that “thorough informed consent is prudent before robotic surgery because of the risk of ocular complications.”
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