Effects of Different MAP Targets on Ocular Perfusion and Optic Nerve Microvasculature During Rhinoplasty

Overview

This randomized controlled trial aims to evaluate the effects of two different mean arterial pressure (MAP) targets during controlled hypotension on ocular perfusion and optic nerve head microvasculature in patients undergoing elective rhinoplasty or septorhinoplasty. A total of 60 patients will be randomized in a 1:1 ratio to a target MAP of either 50-60 mmHg or 60-70 mmHg during general anesthesia. Intraocular pressure (IOP) will be measured at predefined perioperative time points, and estimated ocular perfusion pressure (OPP) will be calculated using simultaneous MAP and IOP measurements. Optical coherence tomography angiography (OCTA) will be performed preoperatively and postoperatively to assess changes in peripapillary, optic nerve head, and macular microvascular parameters. The primary objective is to compare changes in peripapillary vessel density between the two MAP target groups. Secondary objectives include evaluating changes in optic nerve head microvasculature, intraoperative OPP and IOP, and the relationships between the depth and duration of hypotension and OCTA-derived microvascular changes.

Controlled hypotension is commonly used during rhinoplasty to reduce intraoperative bleeding and improve surgical field visibility. However, reductions in mean arterial pressure (MAP) may also decrease ocular perfusion pressure (OPP), particularly when accompanied by changes in intraocular pressure (IOP). Although perioperative ischemic optic neuropathy is rare, hypotension and other factors that reduce tissue perfusion have been reported as potential contributors to perioperative visual complications. The effects of different controlled hypotension targets on ocular perfusion and optic nerve head microvasculature during rhinoplasty remain insufficiently characterized. This prospective randomized controlled trial will include 60 patients aged 18-50 years with American Society of Anesthesiologists (ASA) physical status I-II who are scheduled for elective rhinoplasty or septorhinoplasty under general anesthesia. Participants will be randomized in a 1:1 ratio using computer-generated block randomization to one of two intraoperative controlled hypotension strategies: a target MAP of 50-60 mmHg or a target MAP of 60-70 mmHg. Participants and the ophthalmologist performing the postoperative OCTA assessment will be blinded to group allocation, whereas the attending anesthesiologist and surgeon will not be blinded. All patients will receive standardized general anesthesia. MAP and other standard monitoring parameters will be continuously monitored. IOP will be measured noninvasively in the same eye using tonometry at predefined perioperative time points: before induction of anesthesia, after endotracheal intubation, after achieving the target MAP, 15 minutes after establishment of controlled hypotension, every 30 minutes thereafter during maintained hypotension, at the end of surgery, and during the early post-extubation period. MAP will be recorded simultaneously with each IOP measurement, and estimated OPP will be calculated as MAP minus IOP. Optical coherence tomography angiography (OCTA) will be performed using the same device before surgery and during postoperative follow-up. Preoperative OCTA will be obtained 1-7 days before surgery, and postoperative assessments will be performed within 24-72 hours, at 1 week, and at 1 month. OCTA-derived parameters will include peripapillary vessel density, optic nerve head vessel density, and superficial and deep macular vascular density. The primary outcome is the change in peripapillary vessel density from the preoperative measurement to the early postoperative assessment. Secondary outcomes include changes in optic nerve head and macular microvascular parameters, minimum intraoperative estimated OPP, maximum change in IOP, and the relationships between the depth and duration of controlled hypotension and postoperative OCTA-derived microvascular changes. The study is designed to determine whether different MAP targets used during controlled hypotension are associated with different patterns of ocular perfusion and subclinical optic nerve head microvascular change. The study is not designed to determine the incidence of perioperative ischemic optic neuropathy or other rare postoperative visual complications.