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AMBULATORY ANESTHESIA

Preoperative Peribulbar Block in Patients Undergoing Retinal Detachment Surgery Under General Anesthesia: A Randomized Double-Blind Study

Département d’Anesthésie-Réanimation, Service d’Ophtalmologie, Hôpital Bellevue, Saint-Etienne, France

Address correspondence and reprint requests to Jean Pascal, MD, Département d’Anesthésie-Réanimation, Hôpital Bellevue, 42055 Saint-Etienne cedex 2, France. Address e-mail to jean.pascal{at}chu-st-etienne.fr.

	Abstract

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Retinal detachment surgery is frequently associated with significant postoperative pain and emesis in adults. In this randomized, double-blind, controlled study we sought to demonstrate that 1% ropivacaine peribulbar (PB) block in conjunction with general anesthesia (GA) improves operative conditions and postoperative analgesia compared with GA combined with subcutaneous normal saline injection into the inferior eyelid. Thirty-one patients were included in each group. Anesthesia was performed with target-controlled infusion propofol and continuous remifentanil infusion adjusted to maintain bispectral index values between 40 and 50. Postoperative analgesia included fixed-dose IV infusion of propacetamol and IV injection of nefopam via a patient-controlled analgesia device. Tramadol was infused IV as rescue medication. Demographic data were comparable between the groups and bispectral index values were maintained at the objective target. In the PB group, fewer patients presented an oculocardiac reflex (6 versus 17; P < 0.01); bleeding interfering with the surgical field was reduced (1 versus 11 patients; P < 0.01); mean time to first nefopam request was longer (148 ± 99 versus 46 ± 58 min; P < 0.01); mean nefopam consumption was diminished during the first 6 h after tracheal extubation (18.9 ± 13.9 versus 28.5 ± 14.7 mg; P < 0.05); immediate postoperative pain scores were lower; and fewer patients required rescue medication (5 versus 23; P < 0.01). The two groups were similar with respect to the incidence of postoperative nausea and vomiting. Overall, PB block combined with GA improved operating conditions and postoperative analgesia in retinal detachment surgery.

	Introduction

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Retinal detachment surgery involving scleral buckling and intraocular expansive gas injection is associated with significant postoperative pain and emesis in adults (1–4). In comparison with general anesthesia (GA), regional anesthesia reduces the incidence of oculocardiac reflex (5) and decreases postoperative pain and vomiting (3). However, surgical dissatisfaction because of insufficient akinesia with partial blockade (6,7) and patient discomfort during prolonged surgery involving scleral buckling are potential limitations (6,8). The combination of GA and peribulbar (PB) block might limit these drawbacks but has been little studied in the context of retinal detachment surgery (1,9). The aim of this study was to evaluate the effects of 1% PB ropivacaine combined with GA on oculocardiac reflex, surgical bleeding, postoperative pain, and occurrence of nausea and vomiting (PONV).

	Methods

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After approval of the study by the Institutional Ethics Committee and the written informed consent of each patient, we enrolled 62 patients scheduled for primary retinal detachment surgery and presenting an ASA physical status I–II. Exclusion criteria included age younger than 18 yr, the usual contraindications for regional anesthesia, clotting abnormalities, impaired mental status, drug abuse, and surgical procedures entailing vitrectomy without scleral buckling. All operations were performed by the same experienced surgeon (PG). Patients were randomly allocated to one of two groups to receive either GA plus PB block (PB group, n = 31) or GA plus subcutaneous injection of normal saline (control group, n = 31). The randomization list was provided by the hospital biostatistics department. The technique to be used for each patient was revealed by opening a sealed envelope. All patients received hydroxyzine 1.5 mg/kg orally 1 h before surgery. In the anesthetic induction room, a peripheral IV catheter was inserted and heart rate (HR), oxygen saturation, and noninvasive arterial blood pressure were monitored. Propofol 0.5 mg/kg was injected IV to obtain a brief period of sedation during PB puncture. All punctures were performed in the induction room by a senior anesthesiologist experienced in the technique who was not involved in the perioperative management and evaluation of the patients. The study solutions were prepared by this physician at the bedside just before the injection. In the PB group, 1% ropivacaine was injected into the PB space through the inferior eyelid at the junction of the lateral third and medial two thirds of the inferior orbital edge (10). A single transcutaneous injection was performed using a 25-gauge 30 mm short-bevel needle, the injected volume being adjusted individually for each patient. The injection was discontinued when lid fullness appeared, accompanied by a sensation of ‘full orbit.‘ In the control group, normal saline (2 mL) was injected subcutaneously at the same site on the inferior eyelid, using a 25-gauge 15-mm needle. Intermittent compression was applied for 10 min in both groups, using a Honan balloon set at 30 mm Hg. The anesthesiologist who had performed the injection then evaluated ocular globe motility on a scale of 1 to 3 in the 4 quadrants (10) as follows: 0 = ocular movement <1 mm, 1 = ocular movement >1 mm but <4 mm, 2 = ocular movement >4 mm. A score 4 was considered to indicate successful motor block. If the motor block was unsuccessful, no further injection was performed to maintain the patient blinding. Sensory block was assessed according to abolition of the corneal reflex and the eye was dressed until induction of anesthesia.

Management of patients was then standardized in the two groups. Neither the anesthesiologist involved in perioperative and postoperative care nor the surgeon knew the randomization group of the patients. An electroencephalogram signal was obtained via electrodes applied in a bifrontal montage. The Bispectral index (BIS) was displayed using the A-1050 BIS Monitor (Aspect Medical System, Inc., Newton, MA). Anesthesia was induced with propofol using a Diprifusor® target-controlled infusion system. The target plasma concentration of propofol was initially set at 1 µg/mL and was then increased stepwise by 0.5 µg/mL increments every 2 min until a target BIS value of 40 was reached. The effect-site concentration dictated by the BIS value was then targeted and a continuous infusion of 0.15 µg · kg^–1·min^–1 remifentanil was started. Tracheal intubation was performed 1.5 min later after topical application of 5% lidocaine to the glottis. All patients’ lungs were ventilated with a mixture of 50% oxygen and 50% air to maintain an end-tidal carbon dioxide pressure of 30–35 mm Hg. HR and arterial pressure were noted 3 min after tracheal intubation; these readings were taken as baseline values as described previously (11). During surgery, remifentanil infusion was titrated stepwise by 0.05 µg · kg^–1 · min^–1 increments every 2 min to maintain BIS values between 40 and 50. If this treatment was unsuccessful after two infusion rate adjustments, the propofol target concentration was increased or decreased by 0.5 µg/mL increments according to the BIS level. These adjustments could lead to discontinuation of remifentanil infusion before the predictable end of surgery. The oculocardiac reflex was considered to be present if the HR decreased by 20% from the baseline value or if dysrhythmias or sinoatrial arrest occurred during ocular manipulation (11). If the HR did not increase after release of surgical stimulation, atropine 0.5 mg was administered. Postoperative analgesia was started 1 h before the end of surgery by IV administration of propacetamol 2 g and nefopam 10 mg. Infusion of propofol and remifentanil was stopped as soon as the eye had been dressed (end of anesthesia). After the patient’s transfer to the recovery room and tracheal extubation, pain was controlled for the first 48 h by systematic intermittent IV administration of propacetamol (2 g/6 h) and IV injection of nefopam via a patient-controlled analgesia device. The patient-controlled analgesia pump delivered a 5-mg bolus and had a lockout time of 30 min with no continuous infusion. A 10-cm visual analog scale (VAS) was used to assess pain intensity; the evaluation was performed by a nurse blinded as to the treatment group. If the VAS score was 4 or more, 100 mg tramadol was infused as rescue medication. If necessary, this treatment was followed by continuous infusion of tramadol at 300 mg/day for 24 or 48 h. PONV (2 episodes within 1 h or persistent vomiting) was treated with 0.1 mg/kg IV ondansetron.

The doses and mean infusion rate of all anesthetics were calculated, as were the duration of surgery and anesthesia. The number of patients in whom remifentanil infusion could be stopped for at least 10 min was noted. Perioperative bleeding was scored by the surgeon using a 3-point rating scale as follows: 0 = absent; 1 = does not interfere with surgery; 2 = interferes with surgery. Time to extubation, time to first analgesic supplement, and time to first analgesic rescue medication was determined from the end of anesthesia. VAS pain scores were assessed at 30 min and at 1, 2, 4, 6, 12, 24, and 48 h after tracheal extubation. The consumption of nefopam and tramadol was noted, as was the incidence of PONV during the periods 0–6 h and 6–48 h postoperatively. Intraocular pressure (IOP) was measured preoperatively and at 24, 48, and 72 h postoperation. Data were collected by the physician responsible for anesthesia during surgery and by the nurses caring for the patient in the surgical unit and the recovery room.

We chose nefopam consumption as the primary end-point to calculate the required sample size for this clinical study. The number of patients was determined on the basis of the results of a preliminary investigation during which we established that for similar retinal surgery performed under GA, the mean ± sd consumption of nefopam was 34 ± 10 mg during the first 6 h postoperatively. The required sample size was calculated to be 30 patients per group to detect with a power of 90% and = 0.05 a difference of at least 25% in nefopam consumption during the first 6 h after the end of surgery. The power and sample size were calculated using the Power^TM program (12). The statistical analysis included data from all patients according to intention-to-treat and was performed using the Statview^TM package (Abacus Concepts Inc., Berkeley, CA). A two-sided ² test or Fisher’s exact test was used to compare qualitative variables; repeated-measures analysis of variance and an unpaired t-test were used for quantitative variables. P < 0.05 was considered statistically significant.

	Results

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Thirty-one patients were included in each group. The two groups were comparable with respect to age, weight, ASA physical status, and gender distribution (Table 1). None of the patients manifested a decrease in HR or arrhythmia during induction of PB block. The mean volume of ropivacaine administered was 11.2 ± 2.1 mL. Successful motor block (akinesia score 4) was achieved within 10 min in 19 patients in the PB group (61%). All but three patients showed abolition of the corneal reflex; motor block was unsuccessful in two of these patients. No differences in surgical procedures were reported between the two groups. The number of meridians concerned by scleral buckling was 5.5 ± 2.4 and 6 ± 3 and the volume of gases injected into the eye was 0.6 ± 0.2 mL and 0.6 ± 0.2 mL in the PB and control groups, respectively (not significant). The durations of surgery and anesthesia were longer in the control group (Table 2). The BIS values measured every 5 min were maintained at 40–50 throughout surgery in both groups; the mean BIS value was 45 ± 11 in the PB group versus 43 ± 9 in the control group (P < 0.01). Mean arterial blood pressure (MAP) was comparable in the 2 groups during anesthesia, the mean value of MAP being 74 ± 14 mm Hg in the PB group versus 76 ± 15 in the control group (not significant). However, there was a significant difference between the PB and control groups with regard to hemodynamic profile. The time during which MAP was <30% of the preoperative value represented 46% ± 30% and 28% ± 29% of the total duration of anesthesia in the PB and control groups, respectively (P < 0.05). Increases in MAP were recorded in 11 patients in the control group during surgery but in only 4 patients in the PB group (not significant). Patients in the PB group had less perioperative oculocardiac reflex compared with the control group (Table 2).

Ten patients developed bradycardia requiring atropine administration in the control group compared with four patients in the PB group (not significant). Surgical bleeding was reported by the surgeon as having been more profuse in the control group than in the PB group, interfering with the surgical field in 11 patients versus 1 patient (P < 0.01; Table 2). During maintenance of anesthesia, remifentanil requirements were significantly smaller in the PB group than in the control group according to mean remifentanil consumption (Table 2). Similarly, remifentanil infusion was discontinued before completion of surgery in 22 patients in the PB group, but in none of the patients in the control group. Propofol consumption and time to tracheal extubation were comparable in the two groups. In the postoperative period, the VAS pain score was higher in the control group during the first 2 h after tracheal extubation (Fig. 1). Adequate analgesia (VAS 3) was observed throughout the study period in the PB group, but only from 4 h postextubation onwards in the control group. The time to the first nefopam request was longer in the PB group, and nefopam consumption was reduced in this group compared with the control group during the first 6 h after tracheal extubation (Table 3). The number of patients requiring rescue medication, as well as the cumulative dose of tramadol over 48 h and the need for its continuous infusion during 24 h or 48 h, were also less in the PB group (Table 3). The two groups were similar with respect to the incidence of PONV (8 versus 7 patients in the PB and control group, respectively). IOP was identical in the 2 groups during the whole study period (data not shown). No incidents or complications occurred in either group.

View larger version (13K): [in this window] [in a new window]   Figure 1. Time course of visual analog scale pain score after tracheal extubation (mean ± sd). *P < 0.01 versus peribulbar group.

	Discussion

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In this randomized double-blind study, the use of GA plus PB block improved operating conditions and resulted in more effective postoperative analgesia compared with GA alone. In the PB group, the incidence of oculocardiac reflex was decreased and surgical bleeding was reduced. Immediate postoperative pain scores were lower, and the time to administration of the first postoperative analgesic was longer when PB block was performed. Both the number of patients who required an analgesic supplement and the total amount of additional analgesic requested were smaller in the PB group. These results were obtained despite the fact that successful motor block at 10 minutes was achieved in only 19 patients (61%). Similar success rates, as judged by akinesia scores, have been described when PB blocks were performed with or without hyaluronidase (10,13,14); total akinesia is much more difficult to achieve than analgesia (14). Although akinesia is generally used as the main criterion for effectiveness of anesthesia in the context of surgery performed under PB block alone (14), our results suggest that the beneficial effects of PB block combined with GA are primarily related to sensory block. Indeed, corneal reflex was abolished in 28 patients (90%). During surgery, it was possible to stop remifentanil infusion, according to BIS values, in 22 patients (71%). The apparent discrepancy observed between the success rate for sensory block and the percentage of patients in whom remifentanil infusion could be stopped, can be explained by the fact that BIS primarily monitors unconsciousness and does not measure analgesia directly (15). The lack of any additional anesthetic injection when motor block was unsuccessful may have contributed to the limited quality and, more specifically, the limited duration of postoperative analgesia. However, it is still important to emphasize that, despite this limitation, both the number of patients requiring supplemental analgesia and the cumulative doses of analgesics injected were smaller in the PB group for 48 hours after the operation.

PB anesthesia, or medial canthus episcleral anesthesia, combined with GA has been reported to decrease the intraoperative incidence of oculocardiac reflex, postoperative pain intensity, and analgesic supplement requirements after vitreoretinal surgery (4,9). However, almost half the patients were scheduled for surgery without scleral buckling in these studies. Placement of a scleral buckle entails extensive dissection of the conjunctiva and sclera and requires repeated traction on extraocular muscles, leading to an increased occurrence of oculocardiac reflex and greater postoperative pain (2). The benefit of PB combined with GA in elective retinal detachment surgery with scleral buckling was evaluated by Shende et al. (1). These authors reported an attenuation of the oculocardiac reflex and a smaller number of patients requiring analgesic supplements during the first 12 hours after surgery in the PB group (1). Despite the reduction in pain scores in the PB group during the 12- to 18-hour period postoperation, a mean pain score >3 was measured in both groups during the 6- to 24-hour period. The more efficient analgesia achieved with PB block in our study could be explained by the different schedule of analgesic administration and by the fourfold larger quantity of ropivacaine received by our patients relative to the quantity of bupivacaine administered in the study by Shende et al.

The incidence of PONV during the first 24 hours postoperation was similar in the two groups (26% and 23% in the PB and control groups respectively) and, although no pharmacological prophylaxis of PONV was administered, it was substantially less than that previously reported in retinal detachment surgery performed under GA (1,16). In the study by Shende et al., the PONV incidence was less frequent in the PB group (40% versus 77%), as described in other investigations (9,16). Nitrous oxide omission and propofol anesthesia decrease the incidence of PONV (17). In a recent meta-analysis, the use of BIS monitoring was found to reduce anesthetic consumption and PONV risk in ambulatory patients (18). All these factors might have contributed to reducing the overall incidence of PONV in our study and could explain why we found no difference between the two groups with regard to the incidence of this adverse event.

A crucial result of our study is the decreased bleeding observed in the PB group. Surgical difficulties related to excessive bleeding were more frequent in the control group and might have prolonged surgery, particularly as the other main factor influencing duration of surgery, i.e., the number of meridians concerned by scleral buckling, was similar in the two groups. The reduced bleeding might possibly have been related to the decrease in IOP induced by PB block (19). Relaxation of extraocular muscles, and possibly a smaller intraocular blood volume resulting from the vasoconstrictive properties of ropivacaine, have been proposed to explain the reduction in IOP after PB block accomplished with ropivacaine (19). Unfortunately, this remains a hypothesis because IOP was not measured after PB anesthesia in our study. As MAP remained below 30% of the preoperative value for a longer period in the PB group, it is also very likely that relative hypotension contributed to the reduced bleeding seen in this group. Deliberate induction of hypotension has been advocated as a means of facilitating intraocular surgery by reducing IOP (20). However, scientific proof of such an effect is lacking. On the contrary, it was demonstrated in an anesthetized pig model that deliberately induced arterial hypotension does not decrease IOP (21).

Complications associated with PB block are infrequent, but nevertheless do occur. Published data from the National Survey of Local Anesthesia for Ocular Surgery in the UK indicate a total incidence of orbital and systemic adverse events of 2.7% and 0.8%, respectively (22). The risk of complications of regional anesthesia, such as globe perforation, brainstem anesthesia, or orbital hemorrhage, should be reduced by using sub-Tenon’s anesthesia (medial canthus episcleral anesthesia) as the needle is then inserted under direct vision and the depth of insertion is limited (14,23). However, although sub-Tenon’s anesthesia is an effective and suitable alternative to PB anesthesia (14), its safety remains to be evaluated in a larger-scale study.

In conclusion, PB block combined with GA was superior to GA alone for retinal detachment surgery with scleral buckling, resulting in less bleeding and preoperative oculocardiac reflex and also improving postoperative analgesia. Further studies are needed to investigate whether other techniques of regional anesthesia might offer the same benefit as PB block.

The authors acknowledge the valuable discussions with Gilles Thuret and Paul Zufferey during this work. They also thank Paula Harry (MediBridge SA, Velizy, France) for editorial assistance.

	Footnotes

 
Accepted for publication November 8, 2005.

	References

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a colleague Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Morel, J. Articles by Molliex, S. Search for Related Content PubMed PubMed Citation Articles by Morel, J. Articles by Molliex, S. Related Collections Ambulatory Regional Anesthesia