For intraocular procedure such as extraction of cataract it is desirable to achive a normal or reduced IOP.[1] Anaesthesiologist can optimize the conditions for cataract surgery by providing an immobile uncongested field, decreasing IOP and thus minimizing the danger of expulsion of intraocular contents when the eye is opened.[2]

 

Dexmedetomidine is a selective alpha2 adrenoreceptor agonist, which provides “conscious sedation” with adequate analgesia, without causing respiratory depression[3].

 

It is sedative-hypnotic, anxiolytic and sympatholytic that can attenuate the stress response to surgery(mitigating tachycardia, hypertension) and also decreases IOP during ophthalmic surgery under local anaesthesia. It also allows patients to respond to verbal commands during the sedation. Easy conversion from sleeping to awakening is possible.[4-7]

 

Fentanyl is a potent synthetic opioid agonist with rapid onset and strong analgesic activity. It is widely used as an anaesthetic adjunct. However, dose-dependent respiratory depression and oxygen desaturation may occur, particularly in elderly patients.[6]

 

Cataract surgery is most commonly done under local anaesthesia with sedation. Several drugs have been used for sedation during this procedure including benzodiazepines, propofol and opiods. However, propofol may cause oversedation and disorientation. Benzodiazepines may result in oversedation, respiratory depression and confusion particularly when administered to elderly patients. Opiods are associated with increased risk of respiratory depression and oxygen desaturation.[6]

The purpose of the current study is to compare between dexmedetomidine and Fentanyl in inducing conscious sedation in Patients undergoing cataract surgery.

 

A total of 64 Inpatients at hospitals attached to Bangalore Medical College and Research Institute, Bangalore, scheduled to undergo cataract surgery under regional anaesthesia. During the period of Nov 2016 – May 2018 will be taken for study, satisfying the inclusion and exclusion criteria Sample size: With reference to the previous study, a minimum sample size of 42, with 21 per group was calculated based on considering 5% alpha error, 90% power 2 SD in each group of change in haemodynamic parameters and intraocular pressures,and to be sensitive enough to identify difference of2 mm Hg of IOP reduction. For better result, a sample size of 60 with 30 in each group has been chosen. Inclusion Criteria: 1. Patients aged 40-70 yrs of either sex. 2. Patients posted for cataract surgery under regional anaesthesia. 3. Patients with ASA (American society of Anaesthesiologists) Grade 1 & 2 Exclusion criteria: 1 Patients with baseline heart rate less than 60 per minute. 2 Patient with COPD,chronic renal failure and hepatic dysfunction. 3 Patients with glaucoma METHODOLOGY After obtaining clearance and approval from Institutional Ethical Committee, patients who were posted for cataract surgery under regional anaesthesia, fulfilling inclusion and exclusion criteria who give informed written consent will be included in the study. Patients were randomly allocated using a computer generated number to one of the two groups: Dexmedetomidine group (Group D) and Midazolam group (Group M)(n = 32each). Group D: Dexmedetomidine 0.25 µg/kg diluted in 20 mL normal saline, administered intravenously over 10 minutes. Group F: Fentanyl 1 µg/kg diluted in 20 mL normal saline, administered intravenously over 10 minutes. Preoperative evaluation of all patients was done, which includes medical history, physical examination and laboratory tests like CBC, RFT, LFT, ECG. The patient will be premedicated with tablet alprazolam 0.5mg the night before surgery. In the pre-operative room, patient will be put on standard monitors like non-invasive blood pressure, pulse oximetry and electrocardiogram. All basal parameters were recorded including IOP in non-operating eye by using schiotz tonometer. In Group D,patients were received 0.25 µg/kg of dexmedetomidine diluted in 10ml of NS over 10 minutes as IV injection. Patients in Group F received fentanyl 1 µg/kg diluted in 20 mL normal saline and administered intravenously over 10 minutes. Under aseptic precations in supine postion, peribulbar block was given with injection lignoadrenaline(8-10 ml) with hyaluronidase10 minutes after the injection of drug and all vital parameters were recorded including IOP in non-operating eye using schiotz tonometer. Level of sedation is assessed by Ramsay Sedation Score and level of analgesia by Visual Analogue Scale. Modified Alderet Score is used to assess the readiness for discharge post-operetively.HR, MAP, SpO2, RSS and VAS score were recorded pre-operatively every 5th minute till 30th minute. Post-operatively HR, MAP, SpO2, RSS, VAS and MAS score were recorded. Adverse effects like hypotension, bradycardia and decrease in saturation(desaturation) were recorded. Operational Definition Hypotension: as 20-30% decrease in MAP and treated with fluid bolus followed byinjmephentramine. Bradycardia:as heart rate <60 beats per minute and is treated with inj atropine. Decrease in saturation (Desaturation):as SpO2<90% and is treated with administration of oxygen. Statistical analysis: Statistical analysis will be performed as follows: Student's t-test was used to compare continuous variables between the two groups, while the chi-square test was used to compare categorical variables. A p-value <0.05 was considered statistically significant,. All the analysis will be done using SPSS 16 version.