Effects of Crystalloid versus Colloid and the α-2 Agonist Brimonidine versus Placebo on Intraocular Pressure during Prone Spine Surgery

Anesthesiology, 04/06/2012

Brimonidine slightly reduced the primary outcome of intraoperative time–weighted average intraocular pressure (IOP), whereas there was no significant difference between goal–directed albumin or crystalloid administration. Brimonidine thus helps reduce IOP during spine surgery, but maintaining adequate blood pressure might play a more important role.


  • Patients having complex prone spine surgery were factorially randomized to albumin and topical placebo (n=15); albumin and topical brimonidine (n=16); lactated Ringer's solution and topical placebo (n=13); and lactated Ringer's solution and topical brimonidine (n=16).
  • IOP was measured with a pneumotonometer.
  • The primary outcome was time–weighted average intraoperative IOP.


  • Prone positioning increased IOP a mean±SD of 12±6mmHg.
  • IOP increased to 38±10mmHg at the end of anesthesia (approximately 5.5h).
  • Time– weighted average intraoperative IOP in the brimonidine group was 4(95% CI: 1, 8)mmHg lower than in the placebo group (P=0.023), but no different in the crystalloid and albumin groups (mean difference (95% CI) of –2(–5, 2)mmHg (P=0.34).
  • There was no interaction between the two randomized factors.

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