|Year : 2022 | Volume
| Issue : 4 | Page : 358-364
Peribulbar block for retinal surgery comparison among dexmedetomidine, fentanyl, and local anesthesia
Wesam A Abu-Elwafa, Islam M Ahmed, Salah-Eldin A Abdul-Aziz, Ahmed H Hassan
Department of Anesthesia and Intensive Care, Faculty of Medicine, Sohag University, Sohag, Egypt
|Date of Submission||13-Apr-2022|
|Date of Decision||28-Aug-2022|
|Date of Acceptance||04-Sep-2022|
|Date of Web Publication||29-Dec-2022|
MD Ahmed H Hassan
Department of Anesthesia and Intensive Care, Faculty of Medicine, Sohag University, Sohag 82524
Source of Support: None, Conflict of Interest: None
Introduction Among all the regional blocks, the peribulbar block is one of the most popular for most ophthalmic procedures as it has few complications.
Aim To study the effects of mixing local anesthetic with either dexmedetomidine or fentanyl in the peribulbar block for vitreoretinal surgery.
Patients and methods The study included 40 adult patients (ASA II–IV) who had a peribulbar block for elective retinal surgery at Sohag University Hospital. All patients received the following combination: lidocaine 2%, bupivacaine 0.5%, hyaluronidase 15 IU/Ml, in addition to either 20 μg of fentanyl (group F) or 20 μg of dexmedetomidine (group D). The duration of postoperative analgesia, the onset, and duration of sensory and motor blocks, along with other complications, were recorded.
Results The onset time of motor and sensory blocks was significantly longer in group F. For the duration of sensory and motor blocks, group D had a significantly greater duration than group F (P=0.05). Group D took substantially longer to request analgesia than group F (P=0.0002). Total paracetamol consumption was substantially higher in group F than in group D (P=0.001). The overall number of patients who required nalbuphine was substantially higher in group F (P=0.003) than in group D. At 2, 4, and 6 h postoperatively, the visual analog scale was statistically significantly greater in group F than in group D.
Conclusion Dexmedetomidine-local anesthetic mixture in the peribulbar block for retinal surgery was superior to fentanyl-local anesthetic mixture regarding onset and duration of motor, sensory block, postoperative analgesia, and analgesic requirement.
Keywords: dexmedetomidine, fentanyl, peribulbar block, retinal surgery
|How to cite this article:|
Abu-Elwafa WA, Ahmed IM, Abdul-Aziz SEA, Hassan AH. Peribulbar block for retinal surgery comparison among dexmedetomidine, fentanyl, and local anesthesia. Res Opin Anesth Intensive Care 2022;9:358-64
|How to cite this URL:|
Abu-Elwafa WA, Ahmed IM, Abdul-Aziz SEA, Hassan AH. Peribulbar block for retinal surgery comparison among dexmedetomidine, fentanyl, and local anesthesia. Res Opin Anesth Intensive Care [serial online] 2022 [cited 2023 Mar 26];9:358-64. Available from: http://www.roaic.eg.net/text.asp?2022/9/4/358/365789
| Introduction|| |
For many ophthalmic surgeries, peribulbar block is the best choice of anesthesia as it has fewer complications . Retinal procedures present numerous obstacles for anesthesiologists as they take a long time and have a high incidence of postoperative discomfort, where the majority of the patients are elderly and have multiple chronic conditions .
The peribulbar block is considered by most anesthesiologists as a safe technique, but the slow onset of orbital akinesia is the main disadvantage, and to produce it, repeated injections or more additional volume of local anesthetic solution is required owing to limited diffusion of local anesthetics . The frequency of complications such as globe perforation and peribulbar hemorrhage is also increased .
To improve peribulbar block and increase tissue perfusion of local anesthetic, hyaluronidase and other adjuvants such as epinephrine, clonidine, and alkalinization of local anesthetics are usually used ,. Hyaluronidase is an enzyme that catalyzes the depolymerization of hyaluronic acid to decrease the viscosity of the tissue, allowing a full spread of injected fluids through tissue planes . The primary benefit of hyaluronidase in regional anesthesia is to speed up onset and enhance quality of blocks , but in peribulbar techniques, the results are more conflicting .
Fentanyl is a synthetic narcotic, which is frequently added to local anesthetics, to prolong its action to give better analgesia . Dexmedetomidine is a selective agonist for the α2 adrenoreceptor with a selectivity ratio of 1620 : 1 . When used with local anesthetics, it activates central and peripheral neuronal blockades. It is used in peripheral nerve blocks, brachial plexus blocks, and retrobulbar blocks as an adjuvant to local anesthetics .
The current study aimed to evaluate and compare the efficacy, duration of sensory block and motor blocks, duration of postoperative analgesia, and any concurrent complications of adding fentanyl or dexmedetomidine as adjuvants to a mixture of lidocaine 2%, bupivacaine 0.5%, and hyaluronidase 15 IU/ml in the peribulbar block for retinal surgeries.
| Patients and methods|| |
The current randomized, prospective, double-blind study was conducted at Sohag University Hospital after obtaining the local ethical comitee approval and informed written conscent from all the patients regarding this type of regional anesthesia and the associated possible complications of the procedure or the drugs used. A total of 40 adult patients ASA II–IV of both sexes, aged 40–80 years, were assigned for elective retinal surgery under the peribulbar block.
The patients were separated into two groups, with 20 patients each:
- Group F had lidocaine 2%+bupivacaine 0.5%+hyaluronidase 15 IU/ml+20 g fentanyl.
- Group D had lidocaine 2%+bupivacaine 0.5%+hyaluronidase 15 IU/ml+20 g dexmedetomidine.
Patients excluded from the study were those with active ocular infection, history of coagulopathy or any blood diseases, those treated with any anticoagulants or antiplatelet therapy, had an allergy to any of the used drugs, who refused local anesthetic technique, or those who cannot lie flat.
The preoperative evaluation included the usage of an intravenous line (20 G). All patients had routine monitoring, including ECG, pulse oximetry, and noninvasive blood pressure. There were no sedatives or hypnotics provided before or during the treatment.
A 5% solution of betadine was used to clean the eyelids and the area around them. All patients had a peribulbar block by a single percutaneous inferolateral approach with a 24-G, 3/4-inch needle.
The injection was carried out with the eye fixed in the primary gazing position; the needle should be directed slightly medially and cephalad at the junction between the lateral one-third and medial two-thirds of the inferior orbital rim. After negative aspiration, 7 ml of anesthetic solution (3 ml lidocaine 2% plus hyaluronidase 15 IU/ml+3 ml bupivacaine 0.5%+1 ml of the study drug) was injected over 30–40 s, followed by a digital massage of the eyeball and compression of the injection site for ∼30 s performed.
During the postoperative phase, the duration of sensory block (time from loss of corneal sensibility to return of corneal sensation) and motor block (time from maximum akinesia to eyes moving freely) was measured every 30 min. Extraocular muscle akinesia was assessed in each of the four orientations (superior, inferior, lateral, and medial) using a three-point scoring system: two indicated normal movement, one indicated partial akinesia, and zero indicated entire akinesia, with a score ranging from 0 to 8 in all directions. A successful block with an akinesia score of 3 or less (no more than 1 in each direction) was completed .
Time from injection of a local anesthetic to loss of corneal sensation, which explains the onset of sensory block, was confirmed by loss of corneal reflex in response to touching the cornea with a cotton wick every 30 s. Visual analog scale (VAS) was used to assess the level of postoperative pain for each patient at 1, 2, 4, 6, 8, and 12 h (VAS score 0=no pain to 10=worst pain). If VAS more than 3, paracetamol 10 mg/kg was given by intravenous infusion over 15 min. If the patient complained of severe pain (VAS>7), nalbuphine 0.15 mg/kg would be given intravenously as a rescue analgesia medication. The number of patients requiring total paracetamol consumption, time of the first request for analgesia, and nalbuphine as rescue analgesia were recorded. Complications such as respiratory depression, bradycardia, tachycardia, hypertension, hypotension, and/or convulsions were recorded, as well.
Statistical analysis was carried out for numerical data using mean, SD, and minimum and a maximum of the range, whereas for certain data, numbers and percentages were used. Analyses were performed for quantitative variables using the one-way analysis of variance test for parametric data between the two groups. Data were reported as mean±SD and were analyzed using an independent sample t test. The χ2 test was used for qualitative data between groups. A power analysis considered a sample size of 20 patients in each group. The level of significance was set at P value less than 0.05.
| Results|| |
The study included 40 patients who were divided into two equal groups: group D and group F. Group D had ten males and ten females, with a mean age of 58±28 years (41–73 years). Group F had seven males and 13 females, with a mean age of 57±27 years (45–76 years). Age, weight, and the duration of the surgery showed no statistical significance in both groups ([Table 1]).
|Table 1 Comparison between group D and group F regarding age, sex, weight, and duration of surgery|
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The onset of sensory block was 87±42 s in group D, being faster than group F, which was 134±65 s. The onset of motor block was 7±3 min in group D, being faster than group F, which was 10±4 min. The duration of sensory block was 160±78 min in group D, being more than the duration of sensory block in group F, which was 150±70 min. The duration of motor block was 179±85 min in group D, being more than the duration of motor block in group F, which was 161±78 min. There was a statistical significance between group D and group F regarding onset time for sensory and motor block, and duration of sensory and motor block (P<0.05) ([Figure 1]).
|Figure 1 Comparison between group D and group F regarding onset time and the duration for both sensory block and motor block.|
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The first time for request analgesia was longer in group D (210±98 min) compared with group F (165±80 min). Moreover, group D showed significantly longer time to first request analgesia compared with group F. The number of patients who need paracetamol and nalbuphine was significantly higher in group F compared with group D. Total paracetamol consumption was 140±68 ml in group D, whereas total paracetamol consumption was 210±100 ml in group F. The number of patients who needed nalbuphine was two (10%) in group D and was eight (40%) in group F. There was a statistically significant difference between group D and group F regarding first time of analgesia request, total paracetamol consumption, and the number of patients requiring nalbuphine (P<0.05) ([Table 2]).
|Table 2 Comparison between group D and group F regarding the first-time request analgesia, total paracetamol consumption, and number of patients requiring nalbuphine|
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The patient’s level of pain evaluated using VAS at 1, 2, 4, 6, 8, and 12 h postoperatively was 1.3, 2.1, 3.3, 3.9, 2.8, and 2, respectively, in group D and was 2.5, 3.9, 7.2, 5.3, 4, and 2.9, respectively, in group F. The VAS was significantly higher in group F than group D at 2, 4, and 6 h postoperatively (P<0.05) ([Figure 2]).
| Discussion|| |
General anesthesia was the traditional technique for vitreoretinal surgery, but local anesthesia has now become widespread in recent years . Patients undergoing vitreoretinal surgeries are often old and have multiple systemic diseases, so the use of general anesthesia techniques with those elderly patients increases anesthetic risk .
Retrobulbar and peribulbar anesthetic blocks are two of the most common regional anesthetic blocks used in eye surgery, especially in older patients, to create adequate surgical and medical conditions for intraocular procedures ,,,,,. Although akinesia and appropriate fast anesthesia can be achieved with retrobulbar block, peribulbar block has become more routinely utilized due to its capacity to provide the same anesthetic effect with a reduced rate of problems such as bleeding, IOP, and anesthetic toxicity . Because injection of local anesthetic mixtures alone may not provide good surgical conditions in terms of block intensity and duration, especially for relatively long operations like retinal surgeries, additive drugs may improve the quality of the block and provide appropriate postoperative analgesia . Clonidine , rocuronium and magnesium , and dexamethasone are usually added to local anesthetic combinations to achieve this vital purpose .
The current study aimed to investigate how adding fentanyl or dexmedetomidine as adjuvants to a local mixture of lidocaine 2%, bupivacaine 0.5%, and hyaluronidase 15 IU/ml in the peribulbar block for retinal surgeries affected the efficacy and duration of sensory and motor blocks, duration of postoperative analgesia, and any concurrent complications. In the study, group D had considerably shorter onset times for both sensory and motor blocks as compared with group F.
In agreement with our study, a previous study compared the effects of adding dexmedetomidine versus fentanyl as an additive to the local anesthetic mixture in the peribulbar block also for retinal surgeries but with a larger volume of the anesthetic mixture than our study (9 ml) and found that group D had a significantly shorter onset time of both sensory and motor blocks (1.69 and 7.2 min, respectively) compared with group F (2.23 and 8.8 min, respectively) . A similar study evaluated the effect of the addition of three doses of dexmedetomidine (15, 20, and 25 µg) to 10 ml of a local mixture of lidocaine 2%+bupivacaine 0.5%+120 IU of hyaluronidase for peribulbar anesthesia in vitreoretinal surgeries . They found that the onset of globe sensory block was shorter in the dexmedetomidine group (1.8, 1.55, and 1.3 min in D15, D20, and D25, respectively) in comparison with the control group (2.5 min). The difference was significant in group D25 and group D20 in comparison with the control group . Furthermore, another study compared the effect of adding 1 ml fentanyl (20 μg) to 5 ml mepivacaine, 3 ml bupivacaine, and 1 ml hyaluronidase local anesthetic mixture in a peribulbar block in vitrectomy to a control group, which received the same local anesthetic mixture without fentanyl; they discovered that there was a statistically significant difference at 3 min, with three (15%) patients in the control group developing total akinesia and 14 (70%) patients at 5 min .
In contrast to our findings, a previous study noticed the effect of adding fentanyl to peribulbar anesthesia in keratoplasty surgery . They classified patients into group F, which received 12 ml peribulbar block containing 30 μg fentanyl and 0.5% bupivacaine and 75 U of hyalase, and group C, which received the same mixture without fentanyl. They found no significant difference in the onset time of anesthesia between groups, which was 4 min in group F and 5 min in group C. In spite of using more volume than our study and adding a bigger fentanyl dose of 30 μug, this difference might be explained by the use of lidocaine in our mixture with its more rapid onset of action than using bupivacaine alone .
Moreover, another study examined the effect of adding two different doses of dexmedetomidine in vitreoretinal surgery (25 or 50 µg) to levobupivacaine-hyaluronidase mixture in peribulbar anesthesia . They found that the onset of corneal anesthesia and globe akinesia in group D25 (1.35 and 8.13 min, respectively) was shorter than in the control group (1.68 and 9.10 min, respectively) but was statistically insignificant, which might be explained by the lack of short-acting local anesthetics; however, with the same mixture and by increasing dexmedetomidine dose to 50 µg (group D50), the onset of corneal anesthesia and globe akinesia (1.05, 6.9 min) was significantly shorter than in the control group .
Moreover, Channabasappa et al.  added dexmedetomidine to local anesthetics used in peribulbar anesthesia for cataract surgery. In that study, group C received 3 ml of 2% lidocaine with 3 ml of 0.5% bupivacaine, whereas group D50 and group D25 received an extra dexmedetomidine 5 and 25 µg, respectively. They reported that the onset of corneal anesthesia and globe akinesia was significantly shorter in group D50 (1.067 and 7 min, respectively) as compared with group C (1.717 and 8.60 min, respectively), whereas in group D25, the onset of corneal anesthesia was significantly faster (1.39 min) but not globe akinesia (8.2 min) as compared with group C, which might be explained by the small volume of local anesthetic mixture used.
In our study, the duration of sensory block was significantly longer in group D compared with group F, and the duration of motor block was also significantly longer in group D compared with group F. According to Khalil and Marouf , the duration of both motor and sensory blocks was considerably longer in the dexmedetomidine group D than in the fentanyl group F. Another study investigated the anesthetic effects of adding dexmedetomidine to a mixture of lidocaine 2% with 10 IU/ml of hyaluronidase and levobupivacaine 0.5% in cataract surgery and found that adding 100 g of dexmedetomidine significantly increased the duration of anesthesia and akinesia for the peribulbar block compared with the control group . In the study conducted by Abo El Enin et al. , it was found that adding fentanyl to local anesthetic mixtures in the peribulbar block considerably extends the duration of globe akinesia compared with the control. Another study compared the effects of adding fentanyl alone versus a combination of fentanyl and clonidine to a local anesthetic for a peribulbar block in cataract surgery and found that adding fentanyl alone 20 μg to a local anesthetic solution did not prolong the block duration, whereas adding both clonidine 15 μg and fentanyl 10 μg to a local anesthetic solution extended the block duration .
According to Hafez et al. , adding dexmedetomidine to the local anesthetic mixture significantly increased the duration of sensory block in group D25 (260 min) when compared with the control group (179 min), but not in group D20 (227 min) or group D15 (192 min). Although there was a lengthening of akinesia in all groups, the difference in the duration of globe akinesia was statistically significant only in group D25 compared with the control group . Furthermore, a previous study discovered that adding dexmedetomidine 25 and 50 g to a levobupivacaine-hyaluronidase mixture increased the duration of corneal anesthetic in group D50 (390.4 min) compared with groups D25 (164.4 min) and C (154.33 min) .
In the current study, we discovered that the first time a patient requested analgesia was longer in group D than in group F, resulting in lower total paracetamol consumption in group D than in group F. The number of patients requiring nalbuphine was two (10%) patients in group D and eight (40%) patients in group F. Similarly, Khalil and Marouf backed our findings, finding that the first time to request analgesia was longer in group D than in group A and group F. In addition, the number of patients who require nalbuphine was significantly higher in group F (70.8%) when compared with group D (13.8%) . Besides, another study discovered that addition of 20 g of dexmedetomidine to 10 ml local mixture in peribulbar anesthesia for vitreoretinal operations, the time it took for the first request for analgesia was much shorter than in the control group .
In the study conducted by Abo El Enin et al. , they discovered a significant difference between the fentanyl and control groups in the first and second hours after surgery, but not after 3 h. In contrast, Nehra and colleagues discovered that when fentanyl 25 was added to a 10-ml local anesthesia, 34 patients in the fentanyl group required the first analgesia in the 4th hour, whereas only one required it in the 3rd hour, which could be explained by the higher volume of the local mixture and higher dose of fentanyl used .
Furthermore, Botros and Boulos  discovered that the time to first request analgesia in the dexmedetomidine group (321.54 min) was greater than our findings, which could be explained by the larger dose of dexmedetomidine used in this study (100 g).
At the postoperative time, the VAS in group F was considerably greater than in group D in our study (2, 4, and 6 h, respectively). A previous study reported that the VAS scale was considerably higher in group F than in group D at postoperative 2, 4, and 6 h, but that both groups were comparable at 8, 12, and 24 h . Another study found a statistically significant differences in the median VAS between the fentanyl and control groups at 1, 2, 3, 4, 5, and 6 h . In comparison with the control group, the fentanyl group had a reduced median pain score.
Interestingly, a previous study used the VAS score to compare the quality of a single injection via peribulbar block in vitreoretinal operations using two different doses of dexmedetomidine added to mixtures of local anesthetic. They found that group D15 and group D30 had significantly lower VAS scores than the control group .
In contrast to our findings, a previous study used a five-point verbal rating score to assess postoperative pain after studying the addition of two different dexmedetomidine doses and found that patients with no pain were nonsignificantly higher in groups D25 and D50 than in the control group . Moreover, in the study conducted by Ahmed and colleagues, 20 g of dexmedetomidine was added as an adjuvant to a 10-ml local mixture in peribulbar anesthesia in patients undergoing vitreoretinal surgery, and it was found that the VAS score was statistically insignificant between the two groups (immediately postoperatively, 2, 4, 6, 8, 10, and 12 h) . There were no difficulties in either group in our investigation.
Previous studies by Khalil and Marouf and Abo El Enin et al. , who did not disclose any peribulbar block-related adverse effects during their studies, backed our findings. Moreover, the study conducted by Botros and Boulos  found that when dexmedetomidine was added to a local anesthetic mixture, the incidence of certain adverse effects was higher, such as dry mouth (group LD, 15%, versus group L, 12.5%), as well as nausea, hypotension, sedation, and shivering (10, 25, 37.5, and 5%, respectively, in group LD and 7.5, 10, 17.5, and 12.5%, respectively, in group L). Sedation was shown to be much more common in group LD (37.5%) than in group L (17.5%). In addition, when compared with group L, the incidence of bradycardia was substantially higher in group D (20%) .
In the study by Channabasappa et al. , in six patients of group D50, they observed bradycardia with the use of dexmedetomidine during the first 60 min after injection, necessitating the use of atropine (0.3 mg), as well as low arterial blood pressure for up to 30 min after injection with no pharmacological intervention. The inclusion of fentanyl in an anesthetic mixture was discovered to increase the likelihood of nausea and vomiting .
| Conclusion|| |
Dexmedetomidine as an additive to the local anesthetic mixture for the peribulbar block in retinal surgery was superior to fentanyl addition to the same mixture of local anesthetics regarding onset and duration of both motor and sensory blocks, analgesic requirements, and postoperative analgesia.
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Conflicts of interest
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[Figure 1], [Figure 2]
[Table 1], [Table 2]