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Departments of
*Anesthesiology and
Ophthalmology, Centre Hospitalier Universitaire, Clermont-Ferrand, France
Address correspondence and reprint requests to T. Gillart, MD, Département d’Anesthésie-Réanimation, Centre Hospitalier Universitaire, 63003 Clermont-Ferrand, France.
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Abstract |
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Implications: One percent ropivacaine may be a more appropriate agent than 0.5% bupivacaine for peribulbar anesthesia by single medial injection. Combined with lidocaine, it provides better akinesia and similar analgesia.
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Introduction |
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Methods |
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The 100 patients were randomly allocated to two groups of 50 by random number table: Group B was given a mixture of 50% bupivacaine (0.5%) and 50% lidocaine (2%), and Group R, 50% ropivacaine (1%) and 50% lidocaine (2%), combined with 25 U hyaluronidase per mL in both groups. After checking for reflux, the local anesthetic mixture was injected at room temperature (20–23°C), without adjustment of pH, and mechanical orbital compression was then applied for 10 min. The amount of anesthetic mixture injected was determined by the degree of lid fullness. In the case of major pain, protrusion of the eyeball or other complication, administration was stopped, but no such complications occurred.
The efficacy of the peribulbar motor block was assessed by an independent, blinded observer immediately after the compression was removed, i.e., 10 min after the block. The patient was asked to close the eyelids firmly and turn the eyes in all directions. Akinesia of the extraocular muscles for each direction (abduction, adduction, elevation, and depression) was scored 0, 1, or 2, depending on whether movement of the eyeball was absent, <2 mm, or >2 mm. Akinesia of the eyelid muscle was scored 0, 1, or 2 depending on whether movement was absent, moderate, or considerable. A cumulative score of 10 indicated normal movement of the eye and the eyelid, and a score of 0 indicated absence of movement. The operations were performed by the same surgeon. He was not aware of the mixture administered and decided whether reinjection was necessary. If akinesia was considered inadequate, a second injection was made at the caruncle, lower temporal, or supranasal level, depending on how much residual movement there was, and akinesia was then scored again. A patient could be reinjected in several sites, as needed. The number, precise location, and amount reinjected were noted. In each case, the duration of the operation and the time that elapsed between injection and incision were noted and compared. Peroperative akinesia was assessed at the end of the operation by asking the surgeon whether it had been adequate or had required a repeat injection.
The pain caused by injection was assessed by questioning patients after their recovery from sedation and was scored from 0 to 3, according to whether it was negligible (0), slight (1), moderate (2), or intense (3) if an injection had to be stopped. During the operation, oxybuprocaine was reinstilled in case pain occurred. If this treatment was not sufficient, a sub-tenon reinjection of 1% lidocaine was performed by the surgeon.
All patients were examined for the occurrence of pre- and postoperative ptosis and conjunctival hemorrhage, which was scored as absent, >3 mm. or <3 mm. When appropriate, surgical explorations were conducted for diplopia.
We noted arterial pressure, heart rate, and SpO2, which were measured noninvasively before the block, after injection, and every 5 min during surgery. Patients were also examined for any other complication after the injection.
The Gaussian distribution of variables was assessed using the analysis of variance log test. The parametric data such as age, weight, axial length of the eye, amount injected, time from injection to incision, and duration of procedure, are expressed as mean ± SD and compared using the unpaired Student’s t-tests. We used the 
2 test to compare the number of reinjections between the two groups and the percentages of patients presenting the same akinesia or sedation scores in each group. All comparisons were two-tailed, and P values of <0.05 were considered significant.
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Results |
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After superonasal reinjection, we observed one case of moderate ptosis (drop in the eyelid reaching the pupil) in each group. In both cases it regressed totally within 1 mo. Three postoperative cases of strabismus were also noted and, after investigation, were attributed to internal rectus muscle retraction. Ten patients in Group B had conjunctival hemorrhage, exceeding 3 mm in seven cases, and eight patients in Group R, exceeding 3 mm in three cases. The exact site of hemorrhage in Group B was inferolateral (4), superomedial (3), and at the caruncle (3), and in Group R, inferolatera (4), superomedial (2), and at the caruncle (2). The percentage of cases of hemorrhage was significantly lower after injection at the caruncle (P < 0.05).
No major complications were observed, including local anesthetics toxicity.
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Discussion |
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With equal doses and concentrations, clinical studies suggest that, with respect to onset, duration, and extent of sensory block, ropivacaine is similar to bupivacaine (4,5). Concerning akinesia, some authors have found that ropivacaine produced a less potent motor block at the same concentration (6). However, there is a greater margin of safety with ropivacaine, which means it can be used in larger concentrations. In animals, it was found to be less toxic to the heart and central nervous system (7). In healthy volunteers, it led only to mild symptoms of central nervous system toxicity at doses 25% larger than bupivacaine, while evidence of reduced cardiac conductivity and contractility appeared at doses 33% larger, and at plasma concentration levels 38% larger (8). For these reasons, ropivacaine may be a more appropriate anesthetic for peribulbar anesthesia than bupivacaine, at least for ensuring per- and immediate postoperative analgesia, the motor block being mainly achieved by adding lidocaine.
In this study, the best results for akinesia were obtained with the combination of ropivacaine and lidocaine. This result is close to that found during hip surgery with epidural 1.0% ropivacaine, which was found to provide longer lasting analgesia and motor block for more patients than 0.5% bupivacaine, as well as a more intense motor block and satisfactory analgesia (9). A difference of this magnitude may be a result of the use of ropivacaine concentrations twice as high as those of bupivacaine, attributable to the lower toxicity of ropivacaine. Perhaps 1% ropivacaine and 0.75% bupivacaine are more equivalent in potential, but 0.5% bupivacaine is the maximal concentration available in France.
The proportion of reinjections reported in the literature after supra- and infraorbital double injection varied between 4% and 50% (10,11). Regarding medial canthus single injection, Ripart et al. (3) and Brahma et al. (2) reported reinjection percentages of approximately 10% using prilocaine, bupivacaine, and lidocaine, or bupivacaine and etidocaine, whereas Döpfmer et al. (12) had a reinjection rate of 45% after administration of prilocaine, and of 63% with a mixture combining equal parts of 2% lidocaine and 0.5% bupivacaine. However, reinjection percentages vary, depending on the degree of akinesia required by the surgeon. In addition, it is difficult to compare the various peribulbar anesthesia studies because of the great differences between the substances used and the ways in which local anesthetics are administered. We showed, for example, that the volumes injected and the speed of administration were likely to affect the number of reinjections by a ratio of 1 to 3, with reasonable amounts of anesthetics varying from 9 to 13 mL, and injection speeds ranging from 5 to 12 mL per minute (13). In our study, interpretation of the results was not affected by bias connected with volume injected, because this was similar for patients who presented satisfactory akinesia and those who received reinjection.
Under the conditions in which the current local anesthesia was performed, i.e., light sedation with propofol, no difference was observed between the groups for pain scores at injection. The number of patients who experienced peroperative pain justifying additional treatment was also similar in the two groups. This kind of result was predictable, given the lasting action of bupivacaine and ropivacaine and the relatively brief duration of this type of operation. A difference in postoperative analgesia might emerge some time after the surgical procedure, but the postoperative course generally involves relatively little pain, which makes assessment of the different cases difficult.
With respect to postoperative complications, we paid most attention to the occurrence of ptosis, diplopia, or conjunctival hemorrhage, which often occur after local anesthesia. The occurrence of ptosis is probably rendered more likely by mechanical surgical factors, such as dehiscence or the separation of the levator aponeurosis, caused by bridle suture or ischemia after eyelid compression by a speculum (14). Anesthesia may also be responsible for ptosis, especially after IM injection of the anesthetic mixture or the use of an excessively large concentration of anesthetic. The myotoxic effect of local anesthetic drugs on the optic musculature is indeed believed to play an important part in the etiology of temporary postoperative ptosis or diplopia. This effect has been reported in the rat and primate (15,16). It has been found for the entire class of aminoacyl anesthetics and seems, in most cases, to be reversible and concentration-dependent (17). In daily clinical practice, numerous studies have revealed more cases of ptosis after peribulbar anesthesia with suprabulbar injection than after retrobulbar or general anesthesia (18–20). In a previous trial, we found that, after peribulbar anesthesia with double superonasal and inferolateral injection, 62 of 140 patients displayed either new onset ptosis or more severe ptosis than preoperatively. This number dropped significantly after one month, when there were only seven patients with new or more severe ptosis (13). In our study of 100 patients, only two cases of moderate de novo ptosis persisted 24 hours after surgery, and they regressed after one month. In both cases, new ptosis occurred after superonasal reinjection. Although we did not compare the results of superonasal and inferolateral injection here, the occurrence of these cases constitutes an argument in favor of single medial injection, which avoids the risk of accidental lesion to the levator palpebrae superioris muscle by the needle. However, this mode of administration involves the risk of injection through the internal rectus muscle in the case of deep injection. This risk can be avoided by using short needles, <25-mm long, which also considerably reduces the risk of direct injection into the subarachnoid space and injury to the optic nerve (21,22). In view of the three episodes of internal rectus muscle retraction we observed, we suggest, like Loken and Hamilton (23), that the needle be introduced 5° medially from the sagittal plane in order to avoid this complication.
Another theoretical advantage of the juxta caruncular injection site is its avascular nature, which may reduce the risk of hematoma. Thus, in our series, only 5% of the cases of hemorrhage occurred at the juxtacaruncular site, whereas 25% of the inferotemporal and 17% of the superonasal reinjections resulted in conjunctival hemorrhage. Note that there were no cases of compressive hematoma in any of our patients, for whom the preoperative work-up always included a coagulation test.
In conclusion, this randomized study shows that the combination of lidocaine plus ropivacaine results in a better quality motor block than lidocaine plus bupivacaine, and in a similar perioperative analgesia for both combinations. In both groups, low rates of early and late ptosis were observed, attributable to the peribulbar anesthesia technique of using a single medial injection. At the same time, the occurrence of three cases of diplopia, caused by contracture of the internal rectus muscle, prompts us to stress the importance of a relatively superficial injection and of introducing the needle strictly in the sagittal plane or even in a slightly medial direction.
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This article has been cited by other articles:
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  D. K. Woodward, A. T. S. Leung, M. W. I. Tse, R. W. K. Law, D. S. C. Lam, and W. D. Ngan Kee Peribulbar anaesthesia with 1% ropivacaine and hyaluronidase 300 IU ml-1: comparison with 0.5%bupivacaine/2% lidocaine and hyaluronidase 50 IU ml-1 Br. J. Anaesth., October 1, 2000; 85(4): 618 - 620. [Abstract] [Full Text] [PDF]
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