Which of the following agents is MOST likely to decrease intraocular pressure?
- □ (A) Fentanyl
- □ (B) Succinylcholine
- □ (C) Midazolam
Ophthalmic surgeries are the most commonly performed surgical procedures in the United States. Intraocular pressure (IOP) is defined by the pressure exerted by different components of the globe to the containing wall. A normal IOP is 16 ± 5 mm Hg, and a value above 25 mm Hg is considered abnormal. A normal IOP is important for maintaining the normal integrity of orbital structures and proper refractory index. IOP is also important for maintaining ocular perfusion pressure, the difference between mean arterial pressure and intraocular pressure. Low ocular perfusion pressures (below 50 mm Hg) have been reported to cause irreversible injury to the retinal cells.
Anesthetic agents and the overall management of anesthesia have relevant effects on IOP (Table). Knowledge of these factors is important to avoid the undue rise of IOP during anesthesia, especially during ophthalmic surgery. Most of the anesthetic agents used for induction of anesthesia (e.g., propofol) have been shown to decrease IOP, as have all volatile anesthetic agents and short-acting opioids (e.g., fentanyl). Nitrous oxide, used in combination with sevoflurane and remifentanil, has not been shown to have any effect on IOP.
Midazolam has not been shown to affect IOP. Succinylcholine has been shown to transiently increase IOP. This effect is thought to be due to the contraction of extraocular muscles during fasciculation. Rocuronium does not have any significant effect on IOP. Reversal of neuromuscular blockade with neostigmine and glycopyrrolate significantly increases IOP. However, the use of sugammadex does not affect IOP.