Cataract surgery can be performed using regional or topical anesthesia or both.1–3 Regional anesthesia techniques are invasive and can be painful. Additionally, they may cause retrobulbar hemorrhage, optic nerve damage, globe perforation, respiratory arrest, prolonged postoperative akinesia, ptosis, diplopia, extraocular muscle dysfunction, and increased blood pressure.4,5 Although topical anesthesia is noninvasive and simple, it has the risk of insufficient analgesia. During surgery, discomfort and pain may develop from the operating microscope light, iris manipulation, irrigation/aspiration, and intraocular lens implantation.6,7 Sudden movements, deep sedation, and pain may cause problems during cataract surgery. Therefore, it is difficult to decide which sedative agent should be used.
Dexmedetomidine is a highly selective alpha-2-adrenoceptor agonist with both sedative and analgesic effects.8 Although it has been used to sedate patients who underwent cataract surgery and better pain control and patient satisfaction has been provided, cardiovascular depression and delayed recovery may accompany it.1,8,9 Midazolam is an imidazo-benzodiazepine that minimizes the anxiety. In studies, it did not seem to reduce pain and anxiety significantly during cataract surgery.10,11 In a previous study, we demonstrated that fentanyl increased patient comfort and provided a decreased verbal pain scale (VPS) score during cataract surgery with topical anesthesia.12,13 But opioids produce a dose-dependent respiratory depression, especially in elderly patients.14
The current study sought to compare dexmedetomidine and midazolam+fentanyl sedation under both topical and peribulbar anesthesia primarily based on patient satisfaction during phacoemulsification. Other factors including surgeon satisfaction, intraoperative and postoperative pain control, intraocular pressure alterations, and operative and recovery times were also compared.
Patients and Methods
The current study is a randomized, double-masked, prospective study. After Institutional Ethics Committee approval, written informed consents were obtained from the patients. Patients aged between 50 and 70 years and eligible for elective phacoemulsification surgery by a single surgeon under peribulbar or topical anesthesia were enrolled. Exclusion criteria were combined glaucoma and cataract surgery, communication difficulties, nystagmus, claustrophobia or orthopnea, sensitivity to the study drugs, history of cardiac or hepatic disease, and use of narcotics, barbiturates, or psychotropic drugs.
Eighty American Society of Anesthesiology (ASA) grade I–II patients were included in the study. Using a computer-generated randomization schedule, patients were randomized to one of the following four groups (20 patients in each group): patients receiving dexmedetomidine under topical anesthesia (DT group); patients receiving dexmedetomidine under peribulbar anesthesia (DP group); patients receiving midazolam+fentanyl under topical anesthesia (MFT group); and patients receiving midazolam+fentanyl under peribulbar anesthesia (MFP group). Dexmedetomidine and midazolam were prepared by the first anesthetist in similar 20-mL syringes and mixed with saline in 0.6 and 20 μg/kg/20 mL doses, respectively.
Patients received any preoperative medication and were taken into the operating room. Standard monitors (Siemens SC 7000; Siemens Corporation, Danvers, MA) were used and continuous heart rate via electrocardiography, noninvasive systolic blood pressure (SBP) and diastolic blood pressure (DBP), respiratory rate, and oxygen saturation (SpO2) via pulse oximetry were recorded preoperatively (basal), after sedation, after local anesthesia, at the 5th and 15th minutes intraoperatively, and at the completion of surgery.
Intraocular pressure (IOP) was measured using Goldmann applanation tonometer 1 hour before surgery (IOPB) and at the 1st hour (IOP1) and 24th hours (IOP24) postoperatively. The ophthalmologist who measured the IOP was blinded to the group assignment.
Oxygen was administered at a rate of 2 L/min by a nasal cannula; all patients also had an intravenous cannula. After the bolus fentanyl dose of 0.5 μg/kg intravenous in the MFT and MFP groups, the mixture of the sedative drugs was administered as an intravenous bolus 120 mL/h over 10 minutes using an infusion pump by a second blinded anesthetist. This was followed by the continuous infusion of dexmedetomidine (0.1 to 0.5 μg/kg/h) and midazolam (5 to 15 μg/kg/h) to a Ramsay sedation scale (RSS) score of 3. RSS scores were evaluated after infusion, after local anesthesia, at the 5th and 15th minutes intraoperatively, and at the completion of surgery. The total amounts of drugs and the other data were recorded by the second blinded anesthetist intraoperatively and postoperatively.
After completion of the loading dose of the study drugs, the blinded ophthalmologist performed topical or peribulbar anesthesia. Topical anesthesia including benoxinate and 2% lidocaine, 2 drops each, was applied to the surface of the cornea 5 minutes before surgery. Peribulbar anesthesia was performed using 2 mL of 0.5% bupivacaine and 3 mL of 2% lidocaine. After anesthesia, surgery was performed when the patients achieved an RSS score of 3. Pain was determined by the VPS (0 = no pain and 10 = worst pain imaginable) during iris manipulation, irrigation/aspiration, and lens implantation. When the VPS score exceeded 3, titrated 10 mg of intravenous propofol was administered and recorded. Paracetamol (500 mg/50 mL, Perfalgan; Bristol-Myers Squibb, Rueil-Malmaison, France) was administered by intravenous infusion and recorded when the postoperative VPS score was more than 3.
The patients were asked to rate their satisfaction with the operative experience on a 5-point satisfaction scale as follows: 0 = extremely dissatisfied, 1 = dissatisfied, 2 = neither satisfied nor dissatisfied, 3 = satisfied, and 4 = extremely satisfied. Furthermore, the surgeons were asked to rate their satisfaction about the sedation using the same method and scale, at the completion of surgery. All adverse events, including but not limited to bradycardia (heart rate < 60 beats/min), hypotension (SBP< 80 mm Hg sustained for > 10 min), respiratory depression (respiratory rate < 10 bpm), oxygen desaturation (SpO2 < 92%), nausea/vomiting, disorientation, or unplanned hospital admission, were recorded.
In the recovery room, the modified Aldrete score15 was determined every 5 minutes until discharge. Patients were deemed ready for discharge when they achieved an Aldrete score of 10. Operative and recovery times were recorded.
All statistical procedures were performed using PS Power and Sample Size Calculations Program, version 2.1.31 (Copyright 1997 by W. D. Dupont and W. D. Plummer) and SPSS statistical software (SPSS, Inc., Chicago, IL), version 15.0 for Windows. All statistical tests were two-tailed, all figures and tables are presented as mean (SD), and the statistical significance level was considered as a P value of less than .05. Satisfaction scores were compared using the Mann–Whitney test. Gender, ASA physical status, and pain and sedation scores were analyzed by Pearson’s chi-square tests. Aiming for power at the 90% level to detect a difference of patient satisfaction scores at the 5% level, a sample size of 20 patients was calculated for each group.
No significant difference was detected with patient characteristics, such as gender, sex, weight, and ASA status, between groups in the study (P > .05). There were no episodes of bradycardia, hypotension, or oxygen desaturation in any group.
There were no significant differences between the groups with respect to all measurement times of heart rate, SBP, DBP, and respiratory rate (P > .05). There was a statistically significant decrease in heart rate, SBP, and DBP values in all measurement times compared to basal values in all groups (P < .001), but no significant change was observed in the respiratory rate. SpO2 was between 92% and 99% in all groups.
There were no significant differences between the groups in terms of mean IOPB (P > .05) or the IOP1 and IOP24 when compared to the IOPB values in each group (P > .05).
The RSS score was in the range of 3 to 4 after sedation in all groups. The sedation scores were similar between groups at all measurement times (P > .05). The total dose of dexmedetomidine administered by continuous infusion was 8.54 and 8.92 μg in the DT and DP groups, respectively, whereas the total dose of midazolam was 213.80 and 226.24 μg in the MFT and MFP groups, respectively. No significant difference was detected between the groups with respect to the infusion dose of drugs (P > .05).
The VPS values ranged from 0 to 5 in the dexmedetomidine groups and 0 to 3 in the midazolam+fentanyl groups. VPS scores were significantly lower in the midazolam+fentanyl groups than in the dexmedetomidine groups (P < .001, Fig. 1), but there were no significant differences between the peribulbar and topical groups with respect to VPS values (P > .05). An intraoperative additional analgesic (propofol 10 mg) administration was done 1 patient (10 mg) in the MFT group, 2 patients (total 30 mg) in the MFP group, 6 patients (total 90 mg) in the DT group, and 5 patients (total 90 mg) in the DP group. So intraoperative analgesic requirement was significantly lower in the midazolam+fentanyl groups than the dexmedetomidine groups (P < .05, Fig. 2). The clinical situations that have high VPS value were lens implantation of 50%, irrigation/aspiration of 35%, and iris manipulation of 15%.
Figure 1. Verbal pain scale (VPS) scores by groups. VPS scores were significantly lower in the midazolam+fentanyl groups than in the dexmedetomidine groups (P < .001). IM = iris manipulation; IA = irrigation/aspiration; LI = lens implantation; MFT = midazolam+fentanyl and topical anesthesia group; MFP = midazolam+fentanyl and peribulbar anesthesia group; DT = dexmedetomidine and topical anesthesia group; DP = dexmedetomidine and peribulbar anesthesia group.
Figure 2. Administration of intraoperative additional analgesic requirement (IOAA) and postoperative analgesic requirement (POA) by groups. Both IOAA and POA requirements were significantly lower in the midazolam+fentanyl groups (P < .05). MFT = midazolam+fentanyl and topical anesthesia group; MFP = midazolam+fentanyl and peribulbar anesthesia group; DT = dexmedetomidine and topical anesthesia group; DP = dexmedetomidine and peribulbar anesthesia group.
The number of patients who needed postoperative analgesia (paracetamol) was 2 (10%) in the MFT group, 3 (15%) in the MFP group, 8 (40%) in the DT group, and 6 (30%) in the DP group. So there were significant differences between the dexmedetomidine and midazolam+fentanyl groups (P < .05, Fig. 2). Conversely, the number of patients who needed postoperative analgesia was similar between the topical and peribulbar groups.
The mean patient and surgeon satisfaction values were 3.60 to 3.75 in the MFT group, 3.65 to 3.70 in the MFP group, 3.15 to 3.25 in the DT group, and 2.90 to 3.25 in the DP group. Both patient and surgeon satisfaction scores were higher in the midazolam+fentanyl groups than in the dexmedetomidine groups and there were significant differences (P < .05, Fig. 3). There were no significant differences between the topical and peribulbar groups with respect to patient and surgeon satisfaction values (P > .05).
Figure 3. Patient satisfaction (PS) and surgeon satisfaction (SS) scores by groups. Both PS and SS scores were higher in the midazolam+fentanyl groups than in the dexmedetomidine groups (P < .05). MFT = midazolam+fentanyl and topical anesthesia group; MFP = midazolam+fentanyl and peribulbar anesthesia group; DT = dexmedetomidine and topical anesthesia group; DP = dexmedetomidine and peribulbar anesthesia group.
The mean values for the operative time of patients in the DT, DP, MFT, and MFP groups were 22.40, 21.80, 22.40, and 20.20 minutes and the mean recovery time values were 33.50, 35.80, 26.60, and 25.20 minutes, respectively. Whereas there was no statistically significance in operative time between groups (P > .05), recovery time was significantly shorter in the midazolam+fentanyl groups (P < .05).
Nausea and vomiting were only observed in one patient each in the DT and DP groups, but were not observed in any patients in the other groups. Disorientation or unplanned hospital admissions were also not observed in any of the patients.
Outpatient cataract surgery is frequently performed by the recently popular combination of the regional/topical anesthesia and sedation. However, there is no common consensus regarding the type of regional anesthesia and the sedative drug to be administered. The results of the current study have demonstrated that sedation with midazolam+fentanyl provided high-level satisfaction scores, low-level pain scores, and shorter recovery time under both topical and peribulbar anesthesia in outpatient cataract surgery.
Although the preference of topical anesthesia is increasingly gaining popularity in cataract surgery performed by phacoemulsification techniques, it has been demonstrated to provide inadequate analgesia in some clinical studies. Gombos et al.3 demonstrated that topical anesthesia was less effective in pain management compared to retrobulbar anesthesia, and that topical anesthesia should be administered in combination with sedation. Rodrigues et al.16 also reported that patient and surgeon satisfaction were not good with topical anesthesia. The patient dissatisfaction may be related to the inadequate sedation in this study. In the study conducted by Fung et al.,17 different combinations of sedatives were administered with topical anesthesia and an increase in the incidence of postoperative pain was reported. In the current study, similar pain scores and similar patient and surgeon satisfaction levels were demonstrated in the topical and peribulbar groups. But the topical anesthesia may be recommended as a non-invasive procedure compared with peribulbar anesthesia. We observed that the patient satisfaction and pain control cannot be provided with only local anesthesia, so the sedation is absolutely required.
In the current study, although hemodynamic changes developed in all groups, there were no episodes of bradycardia, hypotension, or oxygen desaturation in any group. The transient decrease in heart rate, SBP, and DBP values was suggested to be associated with sedation in all study groups. But severe hemodynamic depression was not observed.
These are physiologic changes secondary to anxiolytic effect, which occurs as a result of decreased sympathetic activity by dexmedetomidine, midazolam, and fentanyl.10 Alhashemi,9 Abdalla et al.,1 and Habib et al.10 associated these physiologic changes with sympathetic blockage of dexmedetomidine and midazolam in similar studies. Aydin et al.12 observed no significant differences in heart rate, SBP, and DBP after intravenous fentanyl 0.7 μg/kg during cataract surgery. In the current study, bolus doses of drugs were kept low and were administered with a slow infusion to prevent the risk of severe hemodynamic and respiratory depression. In a study by Muttu et al.,18 despite maintaining the slow infusion (20 min), the high dose of dexmedetomidine (1 μg/kg) was the reason for the severe hypotension. Interestingly, in the study of Alhashemi,9 values of the respiratory rate were observed to increase in the midazolam group. This was associated with the development of a compensatory response to decreased tidal volume to maintain minute volume.
However, an increase in the respiratory frequency due to a decreased tidal volume may not be expected in elderly patients under sedation as in the current study. The explanation of this condition might have been easier if the arterial blood gas pCO2 had been examined. In our study, respiratory changes (respiratory rate and SPO2) were not observed. Although we did not examine the arterial blood gas pCO2, the evidence of hypercapnia as tachycardia and hypertension did not develop.
The avoidance of severe increases or decreases in IOP during and after cataract surgery is important in terms of the success of the operation. In several studies, it was demonstrated that dexmedetomidine, midazolam, and fentanyl decrease IOP by both similar and different pathways.19–21 These drugs suppress sympathetic activity, decrease the tonus of the ocular drainage system, enhance the release of aqueous humor, and thereby decrease the IOP.19,20 Moreover, dexmedetomidine decreases the production of aqueous humor by providing vasoconstriction in the afferent vessels of the ciliary body.19 In our study, a decrease in the IOP values might not have been observed because the measurements were taken at a late period (IOP1). It was thought that Mowafi et al.22 and Abdalla et al.1 reported a decrease in the IOP values because they measured IOP immediately following the sedation in their studies. In our ophthalmology clinic, the routine IOP measurements were done at the 1st and 24th hours after phacoemulsification surgery.
In the current study, moderate sedation was provided in all groups. Although the RSS range was between 3 and 4, adverse events such as cooperation disorders or sudden head movements were not observed. In the study conducted by Alhashemi,9 it was suggested that dexmedetomidine was not an appropriate sedative agent because it led to prolonged recovery time. In the current study, we observed similar results: dexmedetomidine groups had a prolonged recovery time. Although we used a lower dose of dexmedetomidine, the reason for the prolonged recovery time may be an additional propofol administration. Although propofol has a short half-life and was used in a low total dose, it may delay recovery time with dexmedetomidine.
In our study, midazolam+fentanyl provided better pain control in both the intraoperative and postoperative period. Although Abdalla et al.1 used a small dose of dexmedetomidine such as in our study, they provided adequate pain control. We think that this confusion may be related to the method of local anesthesia, but they did not mention local anesthesia. Although two anesthetic drugs were used for either topical or peribulbar anesthesia in our study, the dose of drugs may be insufficient. Erdurmus et al.23 demonstrated that dexmedetomidine significantly reduced the need for an additional analgesic. In the current study, the dexmedetomidine dose was lower than that of Erdurmus et al. In our study, VPS and the additional propofol requirement rate was less in the midazolam+fentanyl groups. The postoperative analgesic requirement was also less in the midazolam+fentanyl groups than in the dexmedetomidine groups. Habib et al.10 demonstrated that midazolam without opioid did not provide significant pain management during cataract surgery under topical anesthesia. In the current study, additional fentanyl in the midazolam+fentanyl groups caused low VPS scores.
The determinants of patient satisfaction in cataract surgery include factors such as the type of local anesthesia, pain, anxiety, and nausea/vomiting. Determinants of surgeon satisfaction include patient satisfaction and patient cooperation and sudden head and eye movements. In our study, we cannot claim that the local anesthesia was effective in assessment of patient and surgeon satisfaction because there was no statistical difference between the topical and peribulbar groups with respect to patient and surgeon satisfaction. In the midazolam+fentanyl groups, the high rate of patient and surgeon satisfaction may be related to the sufficient pain control and sedation. Erdurmus et al.23 reported that surgeon and patient satisfaction were better in cataract surgery performed under sedation with dexmedetomidine using topical anesthesia compared to surgery without sedation. Cok et al.24 reported a high rate of patient satisfaction for sedation with midazolam during cataract surgery performed under retrobulbar anesthesia.
Our study demonstrated that the determinative factor for patient satisfaction is a type of the sedative drug but not a local anesthesia procedure during phacoemulsification. Our study also revealed that the midazolam+fentanyl combination provided high-level satisfaction scores, low-level pain scores, and shorter recovery time. In addition, both of the peribulbar and topical anesthesia procedures showed similar efficiency. However, if the injection pain and potential risks of peribulbar anesthesia were considered, topical anesthesia appeared to be a safe choice for phacoemulsification.
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