A comparative evaluation of intravenous dexmedetomidine and midazolam in patients undergoing monitored anaesthesia care during cataract surgery

The  present  study  was  conducted  in  the  Department  of  Anesthesia  and  Intensive  Care,Government Medical College and Hospital, Chandigarh in collaboration with the department of Ophthalmology. After obtaining approval of institutional ethics committee and written informed consent, 60 patients (30 in each group) of either sex or ASA grade I - III, between 18 and 80 years of age and scheduled elective cataract surgery with MAC under local anaesthesia were enrolled. The present study was prospective, randomized, double blind and controlled study.

After obtaining written informed consent, all patients were evaluated a day prior to surgery to assess the fitness for the proposed surgical procedure. Randomization of patients was done by using coded sealed envelopes and subsequently they were allocated to one of the following group of 30 each to receive either dexmedetomidine (Group D) or midazolam (Group M).

Group D patients had dexmedetomidine 4µg/ml in the 50 ml syringe and saline in other two syringes.

Group M patients had saline in 50 ml syringe, and midazolam in 1mg/ml in the 5 ml syringe, and midazolam 20µg/kg premixed with saline to a total volume of 3 ml in the 3 ml syringe.

To ensure blinding, three syringes were used in all the patients in both the groups. The study drug was prepared in three maximally filled up coded syringes by a person not involved in study.  The  contents  of  syringe  and  group  of  the  patients  was  unknown  to  the  person administering the drug and the person involved in the data recordings. The codes were not be revealed until the completion of the study.

After completing the loading of the study drug in  both the groups,  the ophthalmologist  performed the peribulbar block.

Phacoemulsification was performed and intraocular lens was implanted. HR, MAP, RR,oxygen saturation (SPo2)  and expired CO2 was recorded every 5 minutes throughout the surgery. At the completion of surgery, in the recovery room, Modified Aldrete score  was determined every 5, 10,15,30,45 min until discharge and the need for any postoperative analgesia (fentanyl in dose of 25 µg) was recorded using VAS. All adverse events including, but not limited to bradycardia (HR <60 beats /min), hypotension were recorded.  Subjective sensation of nausea and vomiting, dryness of mouth  and  delirium  were  recorded  according  to  their  respective  scores.  Patients  were deemed ready for discharge when Modified Aldrete score of ≥12 was achieved .