Background: The purpose was to evaluate a level supine intervention (LSI) during laparoscopic surgery in steep Trendelenburg position (Lap ST). Increased intraocular pressure (IOP) and decreased ocular perfusion pressure have been monitored during Lap ST procedures. Peri-orbital swelling and venous congestion in addition to IOP may produce a low perfusion state in the eye, via a compartment syndrome mechanism potentially exacerbated by trabecular meshwork dysregulated pressure dependent outflow. Research in rodent models has confirmed that in the ST position IOP can increase to critical thresholds of > 40 mmHg and studies have determined that even brief 30-40 minute episodes of acute IOP elevations can result in retinal cell ganglion (RCG) dysfunction. A LSI for one 5 minute interval at the 60 minute time point was introduced and was hypothesized to normalize IOP.
Methods: A repeated measure prospective design was employed. After giving informed consent patients having Lap ST surgery were enrolled. IOP was measured at base in supine position, 30 minute intervals in ST and end of case in supine using a calibrated Reichert Tonopen XL tonometer over duration of the case. An anesthesia research team confined to five people was credentialed and after completing a series of inter-rater reliability tests collected data over a one year period. A control group maintained in the ST position was also monitored. Comparative analysis was completed.
Results:IOP in Lap ST without LSI at 120 minutes ranged 25-54 mmHg ( 31.6 ± 10.18). At end of case 11% returned to normal baseline ( 20.0 ± 6.16). IOP of LSI group ranged 10-33 mmHg (18.4 ± 4.98) at 120 minutes. End of case 75% of LSI patient's IOP's returned to normal baseline (13.9 ± 4.50). Analysis showed statistically significant decrease in mean IOP (P<0.001)
Conclusions: An LSI can minimize the impact of lengthy Lap ST positioning on increasing IOP. Prevention of critical threshold > 40 mmHg should be a consideration during ST position procedures since current research has validated findings that elevated IOP may in fact lead to RCG dysfunction and could potentially lead to a postoperative visual loss event.
Keywords: Intraocular pressure (IOP), posterior ischemic optic neuropathy (PION), ischemic optic neuropathy (ION), ocular perfusion pressure (OPP), postoperative visual loss (POVL), mean arterial pressure (MAP) - IOP = OPP