Abstract

Background/aims: An acute immunological stress reaction was previously reported to occur after the painful setting of retrobulbar anaesthesia before intraocular surgery. This study was conducted to find out whether an oral low dose premedication with midazolam would modify the immunological stress reaction.

Methods: 32 patients undergoing intraocular surgery using retrobulbar anaesthesia were included in a randomised, double blind trial. They received premedication with either 3.75 mg midazolam or placebo 30 minutes before the retrobulbar injection. Counts of leucocyte subpopulations, cardiovascular, and psychometric parameters were measured repetitively before and after the retrobulbar injection.

Results: The numbers of leucocytes increased significantly in the placebo group after the setting of retrobulbar anaesthesia (before retrobulbar injection: 6687 (SD 1025) cells ×10⁶/l; after injection: 7067 (1022) cells ×10⁶/l, p=0.0009) caused by rising numbers of neutrophils (before injection: 4111 (1063) cells ×10⁶/l; after injection: 4352 (1147) cells ×10⁶/l, p=0.0007) and natural killer cells (before injection: 290 (84) cell ×10⁶/l; after injection 354 (133) cells ×10⁶/l, p=0.003). There was no significant increase in total leucocytes (before injection: 5997 (1288) cells ×10⁶/l; after injection: 6189 (1215) cells ×10⁶/l) or in any leucocyte subpopulation in the midazolam group. A significant rise in systolic blood pressure occurred in the placebo group, but not in the midazolam group.

Conclusion: A low dose premedication with midazolam attenuates the immunological and cardiovascular stress reactions occurring with retrobulbar anaesthesia.