The comparison of the effects of general anesthesia and spinal anesthesia on intraocular pressure in lumbar disc surgery

Aim: Perioperative visual loss is a rare but devastating complication. Its incidence is almost 4-fold in surgeries like lumbar discectomy, which are performed in prone position. Although the most frequent cause is posterior ischemic optic neuropathy, increase in intraocular pressure due to prone position may be another cause, as well. This study investigated if general anesthesia and spinal anesthesia have different effects on intraocular pressure in lomber discectomy surgery. Patients and Methods: After obtaining approval of the Local Ethics Committee, adult patients scheduled for elective lumbar discectomy by the Neurosurgery Department were included in the study. Intraocular pressure was measured before prone positioning following anesthesia, and after supine positioning after the end of surgery. In case of general anesthesia, measurement was delayed for 5 minutes to prevent false high readings due to intubation and extubation. vi Results: A total of 120 patients were included, and data from 77 patients were analyzed. It was found that intraocular pressure increased from baseline values after general anesthesia (p<0.001 for both eyes), whereas it was similar to baseline values after spinal anesthesia (p=0.727 and 0.699 for left and right eyes, respectively). It was observed that arterial blood pressure and heart rate abruptly increased following intubation in case of general anesthesia. A linear regression analysis of patient characteristics and intraoperative measurements showed that only body mass index was positively correlated with intraocular pressure. Conclusions: This study investigated discectomy operations which lasted less than 2 hours with no hemodynamic adverse events. It showed that intraocular pressure significantly increased after general anesthesia, whereas it did not change after spinal anesthesia. We are in opinion that if there are concerns about a rise in intraocular pressure during the intraoperative period, spinal anesthesia should be preferred. This suggestion applies to lumbar discectomy cases of short duration, where no hemodynamic adverse events or majör bleeding is expected. It should be noted that patients with higher body mass index may show more pronounced increase in intraocular pressure.