Intraocular pressure and ropivacaine in peribulbar block: a comparative study with bupivacaine

The aim of this study was to compare the effects on intraocular pressure (IOP) of ropivacaine and bupivacaine in peribulbar block.

The study involved 40 patients with ASA physical status I, II or III undergoing cataract surgery under peribulbar block. Patients were allocated to two groups according to the local anesthetic used: Group R (n=20), 1.0% ropivacaine and Group B (n=20) 0.75% bupivacaine, both associated with 50 IU. ml-1 hyaluronidase, in peribulbar double injection technique. IOP was measured at four time points: 0=before block (control); 1=1 min after block; 2=5 min after block; 3=15 min after block.

Mean values of IOP (mm Hg) after block were significantly lower in Group R in comparison to Group B: time point 1=13.4+/-3.2 vs 20.8+/-4.7; time point 2=10.9+/-3.7 vs 14.4+/-3.8; time point 3=7.7+/-4.0 vs 10.5+/-3.1. The variation of IOP was different in each group. In Group R, the mean values obtained at the three time points after block were significantly lower than the control; in Group B, the mean value of IOP rose significantly 1 min after block and was lower than control only at time point 3.

Ropivacaine 1.0% associated with hyaluronidase in peribulbar block is better than 0.75% bupivacaine under the same standard conditions for lowering IOP in intraocular surgery. This effect is probably due to relaxation of the extraocular muscles after the block with both anesthetics, and possibly to a smaller intraocular blood volume due to vasoconstriction in the case of ropivacaine.