Abstract
Purpose::
A review of the recent literature on vitrectomy for retinal detachment in retinopathy of prematurity (ROP) demonstrates poor or no vision even following successful retinal reattachment. The purpose of the present study was to explore the hypothesis that this poor visual outcome may be caused by unintended lowering of the ocular perfusion pressure and possible ischemia during surgery.
Methods::
A retrospective analysis of thirty ICU records was performed to ascertain the conscious mean arterial pressure (MAP) in premature infants within the age range when ROP surgery is typically performed (37 - 41 weeks post-conception, average 39 weeks). Local pediatric anesthesiologists were polled to determine the typical drop in MAP in infants under anesthesia. Five retinal ROP surgeons were surveyed to ascertain typical infusion pressure settings (an index of intraocular pressure, IOP) used during ROP vitrectomy, the duration of the procedure, and how often the anesthesiologist reported the MAP to the surgeon.
Results::
Unanesthetized MAP ranged from 30 - 70 mmHg. Anesthetized MAP ranged from 21 - 56 mmHg. Infusion pressure settings ranged from 15 - 30 mmHg (occasionally higher to achieve hemostasis). Duration of surgery was 30 - 90 min. The MAP was not typically reported to the surgeon by the anesthesiologist.
Conclusions::
Blood flow through the ocular circulations is dependent on the ocular perfusion pressure (MAP minus IOP) which must be greater than zero to prevent complete ocular ischemia. The results of this study suggest that the potential exists for the perfusion pressure to fall below zero during ROP vitrectomy. To minimize the chance of ischemic injury, the surgeon should monitor the MAP and adjust the infusion pressure to assure a positive perfusion pressure.
Keywords: retinopathy of prematurity • retinal detachment • blood supply