ABSTRACT. The effect of the cyclooxygenase inhibitor, indomethacin, on choroidal (ChBF) and retinal (RBF) blood flow during hypercarbia was examined in 16 paralyzed and mechanically ventilated piglets less than 8 d old. The animals were randomly assigned to a control group (mean 2 SEM: wt, 1.66 2 0.1 kg; n = 8) that received a placebo infusion or to an indomethacin treatment group (wt, 1.68 f 0.2 kg; n = 8) that received an infusion of indomethacin (5 mg/kg i.v. over 30 min). Baseline ChBF and RBF were measured using radiolabeled microspheres in room air before and 15 min after the administration of placebo or indomethacin. Animals were then exposed to 30 min of hypercarbia (6-7% COz, arterial COz pressure 8-10 kPa) and measurements were repeated. There were no significant differences in RBF between control (40 2 3 mL/