Effects of crystalloid versus colloid and the α-2 agonist brimonidine versus placebo on intraocular pressure during prone spine surgery: a factorial randomized trial.
BACKGROUND
Volume replacement with colloid solution and topical α-2 agonists may each moderate the progressive increase in intraocular pressure (IOP) during prone surgery. The authors tested the hypotheses that during prolonged prone surgery, IOP increases less with goal-directed intravenous administration of 5% albumin than with goal-directed administration of lactated Ringer's solution, and with topical α-2 agonist brimonidine than with placebo eye drops.


METHODS
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.


RESULTS
Prone positioning increased IOP a mean ± SD of 12 ± 6 mmHg. IOP increased to 38 ± 10 mmHg at the end of anesthesia (approximately 5.5 h). 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.


CONCLUSIONS
Brimonidine slightly reduced the primary outcome of intraoperative time-weighted average 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.
Department of General Anesthesiology, Cleveland Clinic, Cleveland, Ohio 44195, USA. farage@ccf.org
Ehab
E
Farag
Daniel I
DI
Sessler
Bledar
B
Kovaci
Lu
L
Wang
Edward J
EJ
Mascha
Gordon
G
Bell
Iain
I
Kalfas
Edward
E
Rockwood
Andrea
A
Kurz
D058647:Adrenergic alpha-2 Receptor Agonists / Q000008:administration & dosage* / Q000737:chemistry; D000328:Adult; D000368:Aged; D000068438:Brimonidine Tartrate; D002626:Chemistry, Pharmaceutical; D003102:Colloids / Q000008:administration & dosage* / Q000737:chemistry; D000077324:Crystalloid Solutions; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000187:drug effects* / Q000502:physiology; D007430:Intraoperative Care / Q000379:methods*; D007552:Isotonic Solutions / Q000008:administration & dosage* / Q000737:chemistry; D008297:Male; D008875:Middle Aged; D016684:Prone Position / Q000502:physiology*; D011810:Quinoxalines / Q000008:administration & dosage* / Q000737:chemistry; D013118:Spinal Cord Diseases / Q000188:drug therapy / Q000601:surgery*; D016896:Treatment Outcome
D058647:Adrenergic alpha-2 Receptor Agonists; D003102:Colloids; D000077324:Crystalloid Solutions; D007552:Isotonic Solutions; D011810:Quinoxalines; D000068438:Brimonidine Tartrate