assessment of the effect of intravenous lidocaine, dexamethasone and different speeds of injection on fentanylinduced cough during cataract surgery

Background: fentanyl which is frequently used during cataract surgery has been found to induce cough. the aim of this study was to evaluate the effect of iv lidocaine and dexamethasone and different speeds of injection of fentanyl on cough induced by this drug. methods: in this randomized double blind clinical trial study, patients were allocated randomly to four groups to receive 1 mg.kg^-1 lidocaine (group i), 0.1 mg.kg^-1 dexamethasone (group ii) and 5 cc normal saline as placebo (group iii & iv) intravenously. four minutes later, all patients were given 1.5 µg.kg^-1 fentanyl intravenously. fentanyl was administered within 15 seconds in group i-iii and within 2 seconds in group iv. incidence, number and intensity of cough were recorded. heart rate and blood pressure were also recorded before administration of drug, 1 minute after administration of drug and 2 minutes after administration of fentanyl. results: 139 patients were evaluated. there was no significant difference in demographic features of groups including age, weight, gender and also heart rates and blood pressures. incidence and intensity of cough was significantly higher in group iv while there was no statistically considerable difference between other groups. conclusion: this study demonstrated that slowing injection of fentanyl can effectively reduce the incidence of cough induced by drug; hereby administration of lidocaine or dexamethasone becomes unnecessary in this speed of injection. additionally cough incidence after fentanyl injection is affected by patients' ethnicity.