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.

The mean age for Group D was 58.53±7.34years and for Group F was 59.44±6.72years. The p value is 0.6 which is not significant.46.9% female and 53.1% male patients were there in Group D and 50% of female and 50% male were there in Group F with p=0.6 which is not significant.On comparison of age and sex distribution was similar in both groups which is statistically not significant. Therefore age and sex  distribution was comparable in both groups.

Table 1: Mean age of patients in both the groups

Table 2: ASA Grade distribution of patients in both the groups

In Group D, ASA Grade 1 patients were 50% and ASA Grade 2 were 50%. In Group F ASA Grade 1were 70% and ASA Grade 2 were 30% with the p value of 0.2(Table 2)

Figure 1: ASA grade distribution

Table 3: BMI distribution of patients studied

  BMI for Group D was 23.63±1.37 and for Group F was 23.87±2.00 with p value of 0.6 which is not significant(Table 3).

Table 4:  Duration of surgery in both the groups

The mean duration for surgery for Group D was 26.66±2.32 minutes and for Group F was 27.31±1.62 minutes with the p value of 0.2 which is not clinically and statistically significant(Table 4).

Table 5: Baseline HR, MAP, SpO_2, IOP distribution in both the groups

There was no statistically significant difference in baseline HR, MAP, SpO₂, IOP between both the groups.Mean baseline HR in Group D was 86±11.25 and in Group F was 81.97±9.88 with p value of 0.2 which is not significant(Table 5).

Table 6: Comparison of HR in both the groups

Group D patients had decrease in heart rate when compared to Group F patients at intra-operative 5^th minute to post-operative 15^th minute(Table 6).

Table 7: Comparison of MAP in both the groups

 Group D patients had lower MAP when compared to Group F patients at post bulbar block to post-operative 15^th minute which is not significant.

Table 8: Comparison of SpO₂ in both the groups

The mean SpO₂ in Group F was lower when compared to mean SpO₂ in Group D at all the time which is statistically significant.

Table 9: Comparison of IOP in both the groups

IOP was significantly lower in Group D compared with Group F following drug administration and after the bulbar block (p<0.05).        

Table 10:  Comparison of RSS Score in both the groups

RSS score in Group D is lower than Group F at intra-operative 15^th minute to post-operative 15^th.

Table 11: Comparison of VAS score in both the groups

VAS Score was comparable between both the groups

Table 12: Comparison of MAS Score in both the groups

Mean MAS score in Group D is 9.22±0.42 at post-operative 5^th minute with p value of 0.15, 9.34±0.48 at post-operative 10^th minute with p value of 0.06, and 9.50±0.51 at post-operative 15^th minute with p value of <0.0001. This p value was statistically significant, but not clinically as all the patients had MAS Score of 9-10.

The present study compared dexmedetomidine (Group D) and fentanyl (Group F) as sedative and analgesic agents during cataract surgery. The two groups were comparable with respect to age, sex, ASA grade, BMI, duration of surgery, and baseline HR, MAP, SpO₂ and IOP. This baseline comparability indicates that the observed differences were likely related to the study drugs rather than demographic or clinical differences between the groups. The mean age was 58.53 ± 7.34 years in Group D and 59.44 ± 6.72 years in Group F, with no statistically significant difference (p=0.6). Sex distribution was also comparable between the groups (p=0.6). Similarly, ASA grade, BMI, weight, height and duration of surgery showed no statistically significant differences. Therefore, both groups were adequately matched at baseline. Heart rate showed a progressive reduction in Group D compared with Group F, with a statistically significant difference at the 15th intraoperative minute (75.78 ± 8.87 vs. 80.38 ± 8.80 beats/min; p=0.042). This finding is consistent with the sympatholytic action of dexmedetomidine, an α2-adrenergic agonist, which decreases sympathetic activity and may produce bradycardia [7,8]. Although MAP was slightly lower in Group D at several time points, the differences were not statistically significant. This suggests that dexmedetomidine produced a modest haemodynamic effect without clinically significant hypotension. A major finding of the present study was the significantly better maintenance of SpO₂ in Group D. Following drug administration, SpO₂ remained around 97–98% in Group D, whereas it decreased to approximately 94–95% in Group F. The difference was statistically significant from post-drug administration onwards, with p<0.0001 at most intraoperative and postoperative time points. This finding is clinically important because fentanyl, as an opioid, can cause respiratory depression and oxygen desaturation. In contrast, dexmedetomidine produces sedation with relatively preserved spontaneous respiration. Na et al. reported that dexmedetomidine provided effective monitored anaesthesia care during cataract surgery without significant respiratory depression [9]. Similarly, studies evaluating dexmedetomidine in cataract surgery have demonstrated preservation of oxygen saturation and respiratory function [7,8]. *Thus, the higher SpO₂ observed in the dexmedetomidine group in the present study supports its respiratory-sparing advantage over fentanyl. Baseline IOP was comparable between the groups. Following drug administration, IOP decreased significantly in Group D from 16.63 ± 2.20 mmHg to 14.40 ± 2.25 mmHg and further to 12.58 ± 2.12 mmHg after bulbar block. The corresponding IOP values in Group F were higher. The reduction in IOP with dexmedetomidine is consistent with previous studies. Ayoglu et al. reported a significant reduction in IOP following dexmedetomidine administration during cataract surgery [7]. Virkkilä et al. also demonstrated that dexmedetomidine reduced IOP in patients undergoing day-case cataract surgery [8]. This reduction may be advantageous during ophthalmic surgery by providing a more favourable surgical environment. RSS was comparable between the groups during the early intraoperative period. However, from the 20th intraoperative minute onwards, Group D showed significantly lower RSS values compared with Group F. This suggests that patients receiving dexmedetomidine were more easily arousable during the later intraoperative and postoperative periods. Dexmedetomidine is known to produce a distinctive form of sedation resembling natural sleep, in which patients remain relatively easy to arouse and cooperate with verbal commands [9]. This characteristic is particularly useful during cataract surgery, where patient cooperation is important. VAS scores were comparable between the groups, with almost no pain reported during surgery and only minimal pain postoperatively. This indicates that both dexmedetomidine and fentanyl provided adequate analgesia when used along with the regional block. The Modified Aldrete Score was comparable at 5 and 10 minutes postoperatively. At 15 minutes, Group D had a statistically higher score than Group F (9.50 ± 0.51 vs. 9.06 ± 0.44; p<0.0001). However, this difference was not clinically significant because patients in both groups achieved scores of 9–10, indicating satisfactory postoperative recovery.

Dexmedetomidine provides effective conscious sedation comparable to fentanyl during cataract surgery under regional anaesthesia. Dexmedetomidine is associated with greater preservation of oxygen saturation and a greater reduction in intraocular pressure, with acceptable haemodynamic stability. Fentanyl provides satisfactory sedation and analgesia but may be associated with a greater tendency for oxygen desaturation.