The effects of tourniquet on intraocular pressure during knee surgery.

BACKGROUND In this prospective study we aimed at examining the effects of pneumatic tourniquet on intraocular pressure during elective knee surgery. METHOD Twenty patients undergoing elective knee surgery under general anesthesia with tracheal intubation were inluded the study. Anesthesia was induced with pentothal, rocuronium and fentanyl, then maintained with sevoflurane and nitrous oxide in oxygen. Intraocular pressure measurements were performed at 7 time points; awake (baseline), following induction, following tracheal intubation, just before tourniquet inflation, after the inflation of tourniquet, before tourniquet deflation, after the deflation of the tourniquet. RESULTS Baseline IOP was 15 +/- 1 mmHg. Following the induction of anesthesia IOP was reduced significantly (12 +/- 1 mmHg) (p < 0.05), then increased to 16 +/- 1 mmHg after tracheal intubation (p < 0.05). IOP was significantly higher after tourniquet inflation compared with just before (13 +/- 1 mmHg vs 16 +/- 1 mmHg recpectively) (p < 0.05). There was no significant difference between the IOP measurements after the inflation and before the deflation of the tourniquet (p > 0.05). The lowest value was 12 +/- 0 mmHg measured after the tourniquet loosened and it was significant compared with the baseline and the measurement performed before deflation of the tourniquet (16 +/- 0 mmHg) (p < 0.05). CONCLUSION Pneumatic tourniquet may cause a significant IOP increase in patients performing knee surgery under general anesthesia.