Use of epinephrine for IFIS prophylaxis

Intraoperative floppy-iris syndrome (IFIS) associated with tamulosin was recently reported in this journal.1 Because tamulosin is a systemic α-1 adrenergic antagonist, it seems plausible that high doses of epinephrine directly delivered to the iris could overcome the adrenergic blockade. Since June 2005, I have been using intracameral epinephrine for prophylaxis against IFIS in patients taking tamulosin and have experienced uniform success. My technique involves using 1:1000 bisulfite-free epinephrine (American Reagent Laboratories, Inc.), which is mixed in a 1:3 dilution with my usual intracameral anesthetic mixture (“Shugarcaine”: 3 parts BSS Plus mixed with 1 part nonpreserved lidocaine 4% [Abbott Laboratories]) to ensure the pH is adequately buffered. Approximately 1 mL of this mixture is slowly injected into the anterior chamber before instillation of an ophthalmic viscosurgical device. Typically, iris flaccidity will resolve within a few seconds and about 1.5 mm additional mydriasis will occur over the next minute. In 1 patient, epinephrine was inadvertently omitted when operating on his first eye, and he exhibited moderately severe IFIS, whereas the second eye that received epinephrine exhibited no IFIS and achieved and maintained excellent dilation throughout surgery. It is my usual practice to repeat intracameral anesthesia between phacoemulsification and irrigation/aspiration, and I repeat injection of the intracameral mixture containing epinephrine in patients taking tamulosin to maintain dilation and iris tone for the rest of the case. Preservative-free, sulfite-free epinephrine at a 1:1000 concentration injected directly into the anterior chambers of New Zealand white rabbit eyes has been shown to cause much less corneal edema than had been found earlier with sulfite-containing solutions.2 However, some potential for toxicity was felt to exist owing to its pH falling outside the range of 6.5 to 8.5 necessary to avoid endothelial toxicity.3 To ensure lack of endothelial toxicity, the pH of this mixture and each of its components was measured with an Orion Research model 290A pH-meter (Thermo Electron Corporation) that was calibrated immediately before testing. The data are summarized in Table 1 and show that the mixture is well within the safe pH range. Note the highly acidic pH of stock epinephrine, which must be buffered as described above for safe intracameral injection. Stock lidocaine was also found to fall below the minimum safe pH for intracameral instillation, which was why the Shugarcaine mixture was originally formulated. Neither adverse systemic effects nor corneal edema have been observed. Although corneal endothelial measurements are not available, each of the eyes in which this mixture has been used has achieved 20/20 or better best corrected visual acuity on the first postoperative day, supporting the lack of endothelial toxicity.Table 1: The pH of the epinephrine and its components.My preliminary experience indicates that intracameral 1:1000 epinephrine appears to be safe and effective in the prophylaxis of tamulosin-related IFIS. Further research is necessary to determine whether there is a subset of patients predisposed to severe IFIS in whom sodium hyaluronate 2.3% (Healon5) or iris hooks or expansion devices will still prove necessary after intracameral epinephrine. I encourage others to use this therapeutic modality.