Anesth Analg 2005;101:1659-1662
© 2005 International Anesthesia Research Society
doi: 10.1213/01.ANE.0000184046.64631.50
AMBULATORY ANESTHESIA
Inguinal Herniorrhaphy Under Monitored Anesthesia Care with Ilioinguinal-Iliohypogastric Block: The Impact of Adding Clonidine to Ropivacaine
Marc Beaussier, MD,
Henri Weickmans, MD,
Zoubida Abdelhalim, MD, and
André Lienhart, MD, PhD
Department of Anesthesia and Intensive Care. Hôpital St. Antoine, Université Pierre et Marie Curie, Paris, France
Address correspondence and reprint requests to Marc Beaussier, MD, Département d'Anesthésie Réanimation. Hôpital St. Antoine. 184 rue du Fbg St-Antoine, 75012 Paris. France. Address e-mail to marc.beaussier{at}sat.ap-hop-paris.fr.
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Abstract
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There is no information concerning the association of ropivacaine and clonidine for ilioinguinal-iliohypogastric block. In this prospective, double-blind study, we randomly assigned 40 adult patients scheduled for inguinal herniorrhaphy under monitored anesthesia care to receive either 225 mg ropivacaine (7.5 mg/mL) alone (control group) or combined with 75 µg clonidine (clonidine group) for preoperative ilioinguinal-iliohypogastric block. After completion of surgery, patients were transferred to the postanesthesia care unit and were asked to stand up and walk around at the second postoperative hour. After leaving the postanesthesia care unit, patients could take oral propacetamol (500 mg) and codeine (30 mg) on request. Pain intensity was assessed with a 100 mm visual analog scale. Time to first request of supplemental analgesics (median [95% confidence interval]) was 10 h (7.1–14.5 h) and 9 h (6.4–>24 h) respectively in the clonidine and control groups (P = 0.83). Pain at rest did not differ between groups whereas pain at motion was reduced on the third postoperative day in the clonidine group. More patients who received clonidine experienced orthostatic hypotension upon standing up within the first postoperative hours (6 of 20 versus 1 of 20 in the control group; P < 0.05). In conclusion, the benefit of adding clonidine 75 µg to ropivacaine for ilioinguinal-iliohypogastric block for motion pain on the third postoperative day must be balanced with an increasing risk of orthostatic hypotension in the immediate postoperative period.
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Introduction
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Ilioinguinal-iliohypogastric block (IIHB) is an efficient technique for relieving intraoperative and postoperative pain in adult patients operated on for inguinal open herniorrhaphy (1–5). The analgesic benefit of IIHB with ropivacaine 7.5 mg/mL has been demonstrated to last until 24 h after surgery (4). However, despite this interesting result, further efforts must be made to prolong the duration of the local blockade because pain after the initial postoperative period remains a matter of concern (6). Clonidine is a 
2-adrenergic agonist drug that enhances the action of local anesthetics in peripheral block (7,8). There is no information concerning the association of ropivacaine and clonidine for IIHB in adult patients scheduled for open inguinal hernia repair.
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Methods
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After approval from our University ethics committee and written informed consent, 40 adult patients scheduled for unilateral inguinal herniorrhaphy using the Shouldice procedure were included in this prospective, randomized, double-blind study.
IIHB was performed according to a modified Shouldice technique (5). In the clonidine group, the patients received 225 mg of ropivacaine (7.5 mg/mL) with 75 µg of clonidine (0.5 mL). In the control group, clonidine was changed for physiologic serum 0.5 mL. Just before the incision, the surgeon infiltrated the incision site with 10 mL of lidocaine 1% in all patients. Failure of IIHB was defined as the need for additional intraoperative local anesthesia or of a deepening of sedation with large doses of propofol.
Sedation was induced with sufentanil 5 µg and a target-controlled continuous infusion of propofol (Diprifusor®). The objective was to keep the patients at level 2 of the Observer's Assessment of Alertness/Sedation (9). All patients received intraoperative administration of IV paracetamol 1 g.
Patients remained in the postanesthesia care unit (PACU) during the first 2 h postoperatively. At this time, and before leaving the PACU, patients were asked to stand and walk. In the PACU, moderate to intense pain was treated with boluses of IV morphine. After leaving the PACU, patients could take oral propacetamol (500 mg) and codeine (30 mg) on request. Pain intensity was assessed with a 100-mm visual analog scale.
Arterial hypotension and bradycardia were defined as a 20% reduction from preoperative systolic blood pressure and heart rate baseline values. Orthostatic hypotension was defined as a decrease >20 mm Hg in systolic blood pressure or >10 mm Hg in diastolic blood pressure during waking (10). Nausea and vomiting were recorded and they were rated severe if treatment was required. The level of sedation was monitored at 30 min, 1 h, 4 h, 8 h, 12 h, and 24 h with a 4-point rating scale (0 = fully alert, 1 = sleepy but easily arousal with verbal stimulation, 2 = sleepy but hardly arousable, and 3 = unconscious patient not answering to contact). Follow-up telephone evaluation was done 3 days after surgery to determine pain intensity at rest and while walking.
The primary end-point was the time from the end of surgery until the first analgesic request. There is no standard deviation of the time interval to first analgesic request after a IIHB with ropivacaine in adults patients. In Narchi et al.'s study (4) the median time interval was 7.7 h but the range remains unknown. The standard deviation was estimated to be 2 h, corresponding approximately to a period of 12 h between upper and lower sides of the range. We considered an extension by 2 h (25%) to be a clinically significant time to first analgesic request in the patients receiving clonidine. The calculated sample size for a statistically significant difference of 2 h between the two groups with a risk of 5% and a ß risk of 20% was 17 patients in each group.
Continuous data were analyzed with the nonparametric Mann-Whitney U-test. Categorical data were analyzed with contingency tables. Survival curves were compared with the Kaplan-Meier method. Hazard Ratio (HR) was calculated with the COX method. Data are presented in mean ± sd or median (95% confidence interval).
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Results
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Twenty patients in each group successfully completed the study. No failure of IIHB was observed. Demographic data and intraoperative characteristics did not differ between groups (Table 1). The time to first demand for postoperative analgesic did not differ between groups (Fig. 1). The time was 10 h (7.1–14.5) and 9 h (6.4–>24) in the clonidine and control groups, respectively (HR = 0.93 [0.46–1.86], P = 0.83). The between-group difference was –0.3 h (–5.2–+4.7).
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Figure 1. Percentage of patients who did not ask for postoperative analgesics within the first 24 h postoperatively. Presentation as survival curves. Comparison with the Kaplan-Meier method. No difference between the two groups.
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Pain intensity at rest and while walking did not differ between groups, except for motion pain on the third postoperative day (P < 0.05) (Fig. 2).
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Figure 2. Pain intensity measured with a 100-mm visual analog scale (VAS). A) pain at rest. B) pain during walking. No difference between the two groups, except for a better pain control during walking on the third postoperative day in the clonidine group (P < 0.05).
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The incidence of side effects is presented in Table 2. More patients in the clonidine group experienced orthostatic hypotension when standing within the first postoperative hours (P < 0.05). The occurrence of orthostatism was associated with severe dizziness and prevented patients from maintaining a sitting position and standing. All patients were able to stand and walk without difficulty after 24 h postoperatively.
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Discussion
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The results of the present study show that the addition of clonidine 75 µg to ropivacaine 225 mg (7.5 mg/mL) for IIHB in adult patients having surgery for inguinal hernia repair increases the occurrence of orthostatic hypotension while standing within the first postoperative hours but improves pain while walking on the third postoperative day. We were unable to demonstrate any benefit with respect to analgesic effect within the first postoperative 24 hours. The post hoc variability of the time to first analgesic request greatly exceeds our a priori hypothesis, making the current study underpowered to make definite conclusions. We could, however, conclude that there was a significant between-group difference of at least 7 hours with a power of 0.8.
After inguinal hernia repair, the addition of 0.5 µg/kg clonidine to lidocaine 1% in wound infiltration improved immediate postoperative pain (11). In another study, however, the addition of clonidine 150 µg to bupivacaine 0.25% did not enhance postoperative analgesia (12). Considering these results, it can be hypothesized that the prolongation of local anesthetic block induced by clonidine may be masked when combined with long-acting local anesthetics, such as ropivacaine. In our study, the dose of clonidine was arbitrarily selected. It can be argued that the dose was too small to have a significant impact in this setting. Furthermore, it cannot be excluded that clonidine might have an effect when added to a smaller concentration of ropivacaine.
The only benefit from the addition of clonidine that we observed was the slight pain decrease when walking on the third postoperative day. This long-term effect is difficult to interpret but has been described after the coadministration of clonidine with ropivacaine for local infiltration analgesia after tonsillectomy (13).
In the present study, the addition of clonidine to ropivacaine led to more patients experiencing orthostatic hypotension in the second postoperative hour while standing. The occurrence of hypotension has been reported with clonidine even when using very small doses (14). In the ambulatory setting, this side effect could lead to a prolongation of hospitalization.
In conclusion, the benefit of adding clonidine 75 µg to ropivacaine 225 mg (7.5 mg/mL) for IIHB in adult patients having surgery for inguinal hernia repair is to reduce motion pain on the third postoperative day. This benefit must be balanced with an increasing risk of orthostatic hypotension in the immediate postoperative period.
The authors wish to thank P. Y. Boelle, PhD (Department of Biostatistic, St-Antoine Hospital, Paris, France), for his assistance in statistical analysis.
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Footnotes
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Supported, in part, by a grant from AstraZeneca S.A.
Accepted for publication June 7, 2005.
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References
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Abstract
Introduction
