Clonidine as coadjuvant in eye surgery: comparison of peribulbar versus oral administration.

STUDY OBJECTIVE

To determine whether the administration of peribulbar or oral clonidine would enhance analgesia and anesthesia in ophthalmologic surgery.

DESIGN

Randomized double-blind study.

SETTING

Teaching hospital.

PATIENTS

60 ASA physical status I and II adult patients scheduled for unilateral ophthalmologic surgery with peribulbar block.

INTERVENTIONS

Patients were assigned to one of 4 groups, and premedicated with oral 2 mL volume (clonidine or placebo). The peribulbar eye block consisted of local anesthetics plus 1 mL of the test drug. The control group (CG) received oral saline as premedication and peribulbar saline as the test drugs. The clonidine eye group (Clo-eye G) received oral saline and peribulbar 30 microg clonidine. The clonidine oral group (Clo-oral G) received oral 150 microg clonidine and peribulbar saline. The clonidine eye+oral group (Clo eye+oral G) had oral 75 microg clonidine and peribulbar 15 microg clonidine.

MEASUREMENTS AND MAIN RESULTS

Perioperative assessment included anesthesia, analgesia, blood cortisol; and adverse effects. The groups were demographically similar. The latency time to the onset of the peribulbar block was shorter in the Clo-eye G compared to the CG (p < 0.05). The CG presented higher blood pressure levels throughout surgery, compared to the others (p < 0.05). The time to first rescue analgesics was longer in all patients who received peribulbar clonidine compared to the CG (p < 0.05). Analgesic consumption was lesser in the Clo-eye G compared to the CG (p < 0.05). The blood cortisol level was higher during the intraoperative period in all groups (preoperative vs. intraoperative values) (p < 0.01).

CONCLUSION

Despite the higher intraoperative blood cortisol levels, 30 microg peribulbar clonidine decreased the onset time to anesthesia, while 15 and 30 microg peribulbar clonidine prolonged the time to first rescue analgesics in patients under peribulbar block, without increasing the frequency of adverse effects. Conversely, oral administration of clonidine alone did not enhance anesthesia or analgesia following eye block, suggesting a local mechanism of action of clonidine.