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From the *Department of Anesthesiology B and Medical and Surgical ICU and Department of Gynecologic Surgery, Amiens University Hospital, Amiens, France.
Abstract
BACKGROUND: Bilateral ilioinguinal nerve block may be useful to control postoperative pain in gynecologic surgery, especially hysterectomy.
METHODS: In a prospective, randomized, double-blind study, we compared the combination of ropivacaine and clonidine (block group) versus saline (control group). The main objective of this study was to compare the total dose of morphine required during the first two postoperative days. All patients received antiemetic prophylaxis and multimodal IV analgesia.
RESULTS: Seventy patients were randomized. The total morphine consumption during the first two postoperative days was decreased by 51% in the block group compared with the control group (21 ± 9 mg vs 41 ± 24 mg, P < 0.0001). This difference was not only due to morphine titration, but remained significant over the following 2 days. The course of the visual analog scale was equivalent between the two groups. No difference was observed in the side effects of morphine.
CONCLUSION: The use of bilateral ilioinguinal nerve block for postoperative analgesia after hysterectomy decreased morphine consumption by one-half during the first two postoperative days without differences in side effects from morphine between groups.
Multimodal analgesia strategies are now the standard approach to limit the intensity of postoperative pain (1,2). Morphine is widely used for postoperative analgesia, but is often associated with nausea and vomiting (3). Laparoscopic gynecologic surgery is particularly associated with postoperative nausea and vomiting (4). Regional analgesic techniques may be combined with IV analgesia to decrease morphine requirements (5). Bilateral ilioinguinal nerve block (IIB) has been proposed for postcesarean delivery analgesia (6) and posthysterectomy analgesia (7). However, published studies have not clearly demonstrated the real efficacy of this block in these situations, although it has been highly successful in pediatric surgery (8,9) and for inguinal surgery in adults (10). The aim of this study was to investigate morphine consumption with the use of bilateral IIB during the first 2 days after elective nonlaparoscopic hysterectomy or prolapse repair.
METHODS
After obtaining Independent Ethics Committee approval (CCPPRB du CHU d’Amiens) and signed informed consent from each patient, 70 female patients from the Amiens Teaching Hospital Obstetrics and Gynecology Department were prospectively randomized according to a double-blind design to bilateral IIB with ropivacaine and clonidine (block group) or saline (control group). Inclusion criteria were surgery for hysterectomy or prolapse repair with a Pfannenstiel skin incision, patients over the age of 18 yr with an ASA physical status I or II. Patients were not included if they had any of the following diseases: psychological or linguistic disorders interfering with their compliance with the trial (inability to understand the informed consent form), body mass index more than 30, allergy to either local anesthetics or nonsteroidal antiinflammatory drugs, peptic ulcer or renal disease, or infection at the site of IIB.
Surgery was performed under general anesthesia. Patients were premedicated orally with 5 mg of midazolam. General anesthesia was induced with propofol, administered by target-controlled infusion (Diprifusor®) at a dose of 5 µg · mL–1, with sufentanil (0.3 mg · kg–1) and cisatracurium (0.1 mg · kg–1). Patients were tracheally intubated and ventilation was performed with a mixture of oxygen and air. Anesthesia was maintained with a continuous propofol infusion (1–3 µg · mL–1) adjusted to mean arterial blood pressure, sufentanil (0.2 µg · kg–1) every 20–30 min, and cisatracurium (0.03 mg · kg–1) when train-of-four was 
3. After induction of anesthesia but before surgery, patients received an IV bolus of dexamethasone (4 mg) and metoclopramide (20 mg). Postoperative IV analgesia was initiated before the end of surgery with acetaminophen (1 g) and ketoprofen (100 mg). A specialized nurse blinded to the treatment allocation initiated the morphine titration in the postanesthesia care unit (PACU) when the visual analog scale (VAS) was >3 according to the following protocol: IV injection of 3 mg of morphine every 5 min until VAS was 
3. Patient-controlled analgesia (PCA) with morphine was then initiated (concentration of 1 mg/mL, no continuous infusion, refractory period of 7 min, no maximum dose). In the surgical ward, IV analgesia consisted of acetaminophen 1 g q.i.d. and ketoprofen 50 mg q.i.d.
Bilateral IIB was performed immediately after the end of surgery (patient asleep) as previously described (6) by an anesthesiologist blinded to the treatment allocation, but according to a simplified technique, as shown in Figure 1. The anterior superior iliac spine was identified and the needle was inserted at the junction of the lateral third and medial two-thirds of a line between the umbilicus and the anterior superior iliac spine. A blunt needle was directed obliquely at an angle of 45° inferiorly, medially, and anteriorly towards the Pfannenstiel incision (24G Plexuflix Braun® needle). The needle was advanced until a loss of resistance was noted on piercing the fascia of the external oblique muscle. According to our modified technique, no injection was performed between the internal oblique and transversus abdominis muscles, and no intradermal injections were performed laterally and medially. After a negative aspiration test, 15 mL of saline was injected in the control group and 15 mL of a mixture of 5 mg · mL–1 ropivacaine and 0.5 µg · kg–1 clonidine was injected in the block group between the external and internal oblique muscle layers bilaterally. Nerve block success was not assessed.
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Pain was assessed by a 10 cm VAS consisting of a horizontal line with the words "no pain" and "worst pain imaginable" at the left and right ends of the line, respectively. Pain scores were obtained on arrival in the PACU and 6, 12, 18, 24, and 48 h after the end of surgery. The patient’s perception of nausea, itching, postoperative vomiting, or urinary retention (requiring catheterization) was recorded during the first two postoperative days. Respiratory insufficiency defined as Spo2 93% and/or respiratory rate <8 per min, was assessed in the PACU. Morphine consumption was recorded in the PACU at the beginning of titration (T0) and the cumulative dose of morphine administered by PCA (48H) was determined. The total number of postoperative PCA-morphine orders was recorded.
Twenty-seven patients per group were necessary to detect a 50% decrease of morphine consumption between the IIB group and the control group with a power of 95% and a bilateral 
risk of 5%. This calculation was based on a pilot study assuming that the total 48-h morphine consumption was 40 ± 20 mg in the control group. It was decided to include a total of 70 patients. Randomization was performed before the beginning of the study using a randomization table with blocks of six. Seventy sealed envelopes indicating the assigned group were prepared. Results are expressed as mean ± sd or number and percentage (%). A Mann–Whitney test was used to compare groups for quantitative variables. An ANOVA for repeated measures was used to compare groups for the course of morphine consumption and VAS. Bonferroni correction was used as the post hoc test for multiple repeated measures. A 
2 test with Yates’ correction or a Fisher’s exact test was used for qualitative data. No post hoc tests were performed. A P < 0.05 was considered significant.
RESULTS
The groups were similar in terms of operating time, duration of anesthesia, and total intraoperative dose of sufentanil (Table 1). A 51% decrease of total morphine consumption during the first 48 h was observed in the IIB group compared with the control group (21 ± 9 mg vs 41 ± 24 mg, P < 0.0001). In addition, there was more rapid control of early postoperative pain in the IIB group compared with the control group as assessed by less total morphine titration consumption in the PACU (P < 0.001). The morphine consumption during the subsequent periods in surgical wards was significantly lower (P < 0.05) in the IIB group than in the control group (Fig. 2). The course of VAS is shown in Figure 3 with no significant difference between groups (P = 0.06). No difference in terms of side effects and complications was observed between the IIB group and the control group (Table 2). However, the total number of episodes of nausea was higher in the control group than in the IIB group (P = 0.03).
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DISCUSSION
This study shows a 51% decrease of cumulative morphine consumption during the first 48 postoperative hours after hysterectomy or prolapse repair when bilateral IIB was performed with ropivacaine plus clonidine compared with the control group. No significant difference was observed for pain scores and the side effects of morphine except for more episodes of nausea in the control group.
No complication due to the block was observed during this study. However, the absence of assessment of the success or failure of our technique constitutes a limitation of this study. IIB is easy to perform, easy to learn, and few complications have been reported in the literature. The main complications described are intravascular and intraperitoneal injection of local anesthetics (11). These two complications are limited by aspiration tests and the use of a blunt needle. The potential risk of IV or intraperitoneal administration of 30 mL of 0.5% ropivacaine is low (150 mg), as a study in healthy male subjects showed that the maximum IV dose before onset of the first symptoms of neurologic toxicity ranged between 85 and 165 mg (12). Cases of quadriceps paresis have been reported in pediatric surgery due to diffusion of the local anesthetic (13). Another potential risk is bowel perforation, but this complication has never been reported in the literature.
The bilateral IIB technique has been proposed in pediatrics (8,9) and in adults for hernia surgery, with a good analgesic effect (10,14). A study has shown the positive effects of this block in combination with PCA-morphine after hysterectomy (7). Morphine consumption was very high (69 mg in the first 24 postoperative hours in the control group versus 44 mg in the IIB group) (7). This may have been due to the use of morphine alone without multimodal analgesia. Finally, the adverse effects of morphine were not reported (7). IIB had less impact on pain and morphine consumption after cesarean delivery (6). In the study evaluating IIB for postcesarean delivery analgesia, the authors reported only a 28% decrease of the first 24 h morphine use in the block group, with no difference between the groups in terms of side effects (6). Ropivacaine 5 mg · mL–1 is a good anesthetic choice, mainly because of its good benefit/risk balance (15,16). Anesthesia is very rapid, and the 12 h of analgesia may be increased by the addition of clonidine (17). However, some pediatric studies have failed to demonstrate the benefit of addition of clonidine for IIB (18). In the specific context of IIB, clonidine provided only a slight increase in postoperative analgesia (1 h) and more patients experienced orthostatic hypotension (19).
No major difference in the side effects of morphine was observed in this study, despite a 51% decrease of cumulative morphine use, except for the number of episodes of nausea, which was higher in the control group. The first explanation is a lack of power to detect such a difference, since this was not the main goal of the study. Furthermore, the total dose of morphine used was not very high in either group. However, this does not suggest a major impact of IIB. Similar results have been published for postcesarean delivery analgesia (6). Second, the systematic use of antiemetic prophylaxis with dexamethasone and metoclopramide and the protocol of anesthesia may have decreased the global incidence of postoperative nausea and vomiting. Ondansetron was not used in this study, although it is now a standard treatment for the prevention of postoperative nausea and vomiting in nonlaparoscopic gynecologic surgery (20).
In conclusion, bilateral IIB in combination with morphine PCA analgesia decreased, by one-half, the total dose of morphinenecessary to obtain good postoperative analgesia for patients after hysterectomy. The effect of decreased morphine consumption on reduction of morphine-related side effects needs to be investigated in larger prospective trials. IIB has a low benefit/risk ratio in the case of a multimodal program for postoperative analgesia after hysterectomy.
Footnotes
Accepted for publication December 5, 2006.
Supported by University Hospital of Amiens, France.
Address correspondence and reprints to Hervé Dupont, Département d’Anesthésie Réanimation Polyvalente B, CHU d’Amiens, Place Victor Pauchet, 80054 Amiens Cedex, France. Address e-mail to dupont.herve{at}chu-amiens.fr.
REFERENCES
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