osmotics prior to select glaucoma surgeries, especially when the preoperative IOP is very high, i.e., around 50 mmHg. Preoperative lowering of IOP with osmotics is felt to decrease the risk of certain intraoperative and postoperative complications, such as suprachoroidal hemorrhages and decompression retinopathy. These complications are more commonly seen if a very high eye pressure is suddenly dropped to zero at the time of the initial surgical incision [15–17].

When using mannitol infusion preoperatively, 20% mannitol may be given over 60 min starting 1–1.5 h before surgery in order to achieve the maximum IOP reduction before surgery. Although 1 g/kg can be used (Table 27.2), others have suggested using 100 ml of 20% mannitol (20 g dose of mannitol) [2]. The use of mannitol can lower the IOP and increase the anterior chamber depth by dehydrating the vitreous [2, 13]. Six ounces of 50% oral glycerin can be used for the same purpose; however, it may induce problematic vomiting [5]. Since having a patient drink too much fluid prior to eye surgery can create anesthesia concerns, IV mannitol is preferred as a preoperative osmotic. Preoperative ocular digital massage also helps to lower the IOP and reduce positive pressure [13].

Summary for the Clinician

››20% mannitol may be given intravenously over 60 min, either 1 g/kg or 20 g total, preferably starting 1 h before surgery in order to reduce severe intraoperative/postoperative complications in select predisposed patients.

Acknowledgments  Massachusetts Eye and Ear Infirmary Pharmacy Department: Judy Yee RPH, Ann Papadopoulos RPH, and Christine Finn PharmD.

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