EFFECT OF INJECTION PRESSURE ON THE SUCCESS RATE OF PERIBULBAR BLOCK

The aim of this prospective double-blind study was to evaluate the eff ect of the pressure on injection of local anaesthetic during peribulba r anaesthesia. Fifty patients scheduled for cataract surgery under per ibulbar anaesthesia, with a two injection site technique, were randoml y assigned to receive a mixture of 5 ml of etidocaine 1%, 4 ml of bupi vacaine 0.5% and hyaluronidase 50 IU, injected under a constant pressu re of either 140 g.cm(-2) (group 1) or 250 g.cm(-2) (group 2). After o rbital compression, the degree of akinesia of the extra-ocular and orb icular muscles was graded by clinical assessment. A significantly high er rate of satisfactory akinesia of the extra-ocular muscles was found in group 2 (72% vs 28% in group 1) (p<0.01). No significant relations hip was found between the time taken to administer the anaesthetic mix ture at constant pressure and the quality of the block.