Comparative evaluation of ropivacaine and lignocaine with ropivacaine, lignocaine and clonidine combination during peribulbar anaesthesia for phacoemulsification cataract surgery.

BACKGROUND: Peribulbar block is the most common type of local anaesthesia administered for cataract surgery, and continuous efforts are on to find a long-acting local anaesthetic (LA) drug with the safest pharmacological profile.

OBJECTIVES: A double-blind, prospective and randomized study was carried out in our institute to compare the anaesthetic effects of ropivacaine with the combination of ropivacaine and clonidine in administration of peribulbar block for phacoemulsification cataract surgery.

METHODS: A total of 200 patients of both sexes aged 50-80 years of American Society of Anaesthesiologists grade I and II, scheduled for phacoemulsification cataract surgery under monitored anaesthesia care, were enrolled for the study. Patients were assigned into two groups of 100 each; ropivacaine group (R) and ropivacaine clonidine group (RC). Group R received 10 mL of LA solution containing 5 mL of 2% lignocaine, 5 mL of 0.75% ropivacaine and 100 units of hyaluronidase while group RC received 8 mL of a similar mixture with the addition of clonidine 1 μg/kg and saline to make a total volume of 10 mL. Heart rate (HR), mean arterial pressure (MAP), pulse oximetry (SpO(2)), respiratory rate (RR), intraocular pressure (IOP), eye muscle movement scores and quality of peribulbar block were observed and recorded throughout the study period at regular intervals. At the end of the research project, the data was compiled systematically and was subjected to statistical analysis using the ANOVA test with post hoc significance for continuous variables and Chi-square test for qualitative data. Value of P<0.05 was considered significant and P<0.0001 as highly significant.

RESULTS: Demographic characteristics, SpO(2) and RR were comparable in both the groups. Mean HR and MAP were also comparable after a significant variation in the first 2-3 min (P<0.05). Onset and establishment of sensory and motor blocks were significantly earlier in the RC group (P<0.05). IOP decreased significantly during the first 6-7 min in the RC group after the administration of the peribulbar block. Duration of analgesia was prolonged in the RC group (6.5±2.1 h) as compared with the R group (4.2±1.8 h). The side-effect profile revealed a higher incidence of nausea, vomiting, headache and dizziness in Group R, while a considerably higher incidence of dry mouth was observed in Group RC.

CONCLUSIONS: Addition of clonidine to ropivacaine not only decreases the total volume of LA to be used but also augments early onset and prolonged offset of sensory analgesia as well as provides smooth operating conditions with a good sedation level as well by providing a wider safety margin of LA.