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We assessed the analgesic efficacy of postoperative epidural ropivacaine 0.1% with and without sufentanil 1 µg/mL in this prospective, randomized, single-blinded study of 30 ASA physical status IIII patients undergoing elective total hip replacement. Lumbar epidural block using 0.75% ropivacaine was combined with either propofol sedation or general anesthesia for surgery. After surgery, the epidural infusion was commenced. Fifteen patients in each group received either an epidural infusion of 0.1% ropivacaine with 1 µg/mL sufentanil (R+S) or 0.1% ropivacaine without sufentanil (R) at a rate of 59 mL/h. All patients had access to IV piritramide via a patient-controlled analgesia device. The R+S group consumed six times less piritramide over a 48-h infusion period than the R group (median 12.7 vs 73.0 mg; P < 0.001). Motor block was negligible for the study duration in both groups. Patient satisfaction was excellent. The incidence of adverse events, such as nausea, was similar. We conclude that a continuous epidural infusion of 0.1% ropivacaine with 1 µg/mL sufentanil is more effective than ropivacaine alone in treating pain after elective hip replacement without motor block. Implications: This is the first randomized study comparing the efficacy of the epidural combination of ropivacaine 0.1% and sufentanil 1 µg/mL versus plain ropivacaine 0.1% in treating pain after hip replacement. We found that ropivacaine 0.1% and sufentanil 1 µg/mL led to a sixfold reduction in opioid requirements after total hip replacement by producing a negligible motor block.
In isolated rabbit vagus nerve preparations, ropivacaine 0.10.2 mM caused a sensory nerve block similar to bupivacaine 0.10.2 mM, but with a lesser degree of motor blockade (1). However, an epidural infusion of ropivacaine 0.2% and 0.3% after abdominal surgery caused both sensory and motor blockade. Only ropivacaine 0.1% was devoid of motor block, although twice as much patient-controlled analgesia (PCA) morphine was required compared with patients who received ropivacaine 0.2% (2,3). Clinical studies with epidural bupivacaine have shown that its analgesic efficacy can be improved by the addition of an opioid (4,5). No data are available on the epidural combination of ropivacaine 0.1% with an opioid, with the specific aim of avoiding motor blockade of the legs. We compared the analgesic efficacy and the degree of motor blockade after a continuous epidural infusion of ropivacaine 0.1% combined with 1 µg/mL sufentanil (R+S) and ropivacaine 0.1% (R) alone for patients undergoing total hip replacement (THR).
After obtaining institutional ethic committee approval and written informed consent, 30 patients were enrolled in our study. Eligible patients were those scheduled for elective THR, aged 3085 yr, ASA physical status IIII, weighing 45125 kg and 145195 cm tall. Exclusion criteria were any contraindications to epidural anesthesia, allergy to local anesthetics or opioids, or communication difficulties that would prevent reliable postoperative assessment. Patients were randomly allocated to two groups. Oral premedication of 7.515 mg of midazolam was given 1 h preoperatively. After the administration of at least 500 mL of isotonic saline solution over 15 min, an epidural catheter was inserted 35 cm into the epidural space at L35 via an 18-gauge Tuohy needle with cephalad direction of the needle curvature and the patient in the lateral position. With the catheter secured and the patient in the supine position, a 3-mL test dose of ropivacaine 0.75% was given over 15 s through the catheter after aspiration for cerebrospinal fluid or blood was negative. Five minutes later, a further 12 mL of ropivacaine 0.75% was administered over 5 min. If sensory block to pinprick did not reach T10 within 30 min after injection, an additional 5-mL top-up dose of ropivacaine 0.75% was administered. Patients were sedated with propofol or general anesthesia was induced, if desired by the patient, with thiopentone, cisatracurium, isoflurane, and oxygen in nitrous oxide (low-flow anesthesia) and a maximal dose of fentanyl 100 µg. Additional doses (35 mL) of 0.75% ropivacaine were injected epidurally every 2 h during surgery. No additional doses of fentanyl were allowed. If the epidural block was not adequate (e.g., requirement of additional doses of fentanyl), patients were excluded from this study. On arrival in the recovery room, an epidural infusion with either 0.1% ropivacaine or 0.1% ropivacaine and 1 µg/mL sufentanil was commenced at a rate calculated as follows: (height in centimeters -100) x 0.1. All patients had access to IV piritramide, a commonly used opioid in Europe (6) with approximately half the potency of morphine, via a PCA device (Abbott Lifecare PCA Infusor; Abbott Laboratories, North Chicago, IL) with 1.5-mg bolus doses, a 6-min lockout time, and a 45-mg dose limit over 4 h. Wound pain at rest and on coughing was assessed by using a 100-mm visual analog scale ranging from 0 (no pain) to 100 (worst pain imaginable). Sensory block was assessed bilaterally by using analgesia to pinprick with a short-beveled 27-gauge needle, and motor block was assessed according to a modified Bromage scale (7) (0 = no motor block, 1 = inability to raise extended legs, 2 = inability to flex knees, 3 = inability to flex ankle joints). All postoperative assessments at 4, 8, 16, 24, 32, 40, and 48 h were performed by one of the authors. PCA piritramide consumption was recorded. The quality of pain management was judged by the patients and recorded at the last assessment on a 4-point scale (1 = poor, 2 = fair, 3 = good, 4 = excellent). Monitoring included noninvasive blood pressure, heart rate, and respiratory rate. Hypotension was defined as systolic blood pressure <80 mm Hg or >30% decrease compared with baseline; hypertension was defined as blood pressure >180 mm Hg systolic or 110 mm Hg diastolic; bradycardia was defined as heart rate <50 bpm; and tachycardia was defined as heart rate >120 bpm (2,3). Bradypnea was defined as a respiratory rate <12 breaths/min and tachypnea was defined as a respiratory rate >20 breaths/min. Sedation was recorded on a 4-point scale (0 = no signs of sedation, 1 = mild sedation, 2 = moderate sedation, 3 = severe sedation). The incidence of nausea and vomiting was recorded. Statistical analysis was performed using the SPSS statistical package (SPSS Inc., Chicago, IL). Because there were no available data on piritramide consumption under similar circumstances, it was not possible to calculate sample size in advance with respect to statistical power. PCA piritramide consumption was compared in a paired manner using the two-tailed Wilcoxon rank sum test. Differences were considered statistically signifiant at P < 0.05. Demographic data are presented descriptively. Data are presented as the means ± SD.
We enrolled 37 patients. Two were withdrawn because the epidural catheter could not be placed. One patient mistook the PCA button for the bell to summon the nursing staff. Three patients were erroneously disconnected from the PCA device during the study period. One patient required emergency surgery due to bowel perforation on the second postoperative day. The data of 30 patients were eligible for statistical analysis (15 in each group). The two groups did not differ in demographic data (Table 1).
Catheter insertion level, duration of surgery, time until commencement of epidural infusion and PCA device, and the number of patients receiving either general anesthesia or sedation were comparable in both groups (Table 1). The R+S group required 6 times less piritramide than the R group over 48 h (P < 0.001) (Fig. 1). The R+S group used less than half the piritramide as the R group (P < 0.05) in the first 8 h after beginning the epidural infusion; at 16 h, the R+S group required 3 times less piritramide than the R group (P < 0.001) (Fig. 1). The R+S group had a minimal, but constant, piritramide use over the study period, whereas the R group had peak uses at 1624 h and a decrease after that.
Pain scores at rest and on coughing were 0 at all seven assessment times in the R+S group. Two patients in the R group had pain scores of 2040 mm at rest and on coughing 4 h after starting the epidural infusion, and one patient had pain scores of 50 mm at rest and on coughing 16 h after the start of the infusion. Motor block resolved rapidly in both groups. Four patients in the R+S group showed a Bromage grade 1 motor block, and three patients showed a grade 2 motor block 4 h after beginning the epidural infusion. One patient had a grade 1 motor block after 8 h. In the R group, two patients experienced a grade 2 motor block at 4 h, and one patient had a grade 3 motor block in his left leg and a grade 2 motor block in his right leg. Sensory block regressed equally in both groups. The sensory block was still at T10 within 4 h after starting the continuous infusion in two patients in each group. After 8 h of epidural infusion, sensory block had completely regressed. All patients rated the quality of pain management as excellent or good. Nausea was experienced by five patients (four female, one male) in the R+S group, with all women experiencing vomiting. In the R group, two patients (one male, one female) had nausea. Four patients (two male, two female) in the R group had mild to moderate sedation, whereas just one patient in the R+S group was moderately sedated. One patient from each group experienced pruritus. Most side effects were mild and except for the administration of IV metoclopramide for nausea, no other specific treatment was required.
This is the only published study in which epidural ropivacaine 0.1% was combined with an opioid. Because we had no previous experience combining epidural sufentanil and ropivacaine and IV piritramide, we decidedin the interest of patient safety (ward setting)to unblind the observer to group assignment. Although a single-blinded design may introduce observer bias, we thought that the primary efficacy measure of PCA piritramide use was uneffected. We found that the epidural combination of ropivacaine with sufentanil for postoperative pain relief after THR caused a sixfold reduction in analgesic requirements over 48 h without motor blockade. Although theoretical advantages for adding lipophilic drugs to epidural local anesthetics have been postulated (8,9), the risk/benefit analysis of this techniquecompared with epidural opioids alone or IV PCA opioidsis controversial (10,11). Our study does not resolve, nor was it specially designed to address, these issues, and this detracts from its clinical usefulness. The longest period of observation in comparable ropivacaine studies was 21 hours (2,3). Our observation period allowed us to identify differences reliably in opioid requirements and in the degree of sensory and motor blockades in both study groups. The prolonged duration of ropivacaine 0.75% given intraoperatively is the most likely explanation for the sensory (4 of 30) and motor blockades (7 of 30) seen four hours postoperatively. The low pain scores in our study were almost certainly due to the type of surgery. THR is thought to be less painful than abdominal and knee surgery. Total knee replacement often causes severe pain on motion that requires different local anesthetic concentrations. Like bupivacaine (12), ropivacaine causes hypotension in a dose-dependent manner (2). The absence of hypotension in our study is most likely due to the low concentration of ropivacaine used. We observed twice as much nausea and vomiting in the R+S group compared with the R group. It would require further studies with a much larger number of patients to determine whether the incidence of nausea and vomiting with R+S, compared with plain R, would reach statistical significance. In summary, we showed that the combination of ropivacaine 0.1% with sufentanil 1 µg/mL is a safe technique for postoperative analgesia after THR, causing no motor weakness and requiring only minimal analgesic supplementation in the first 48 hours.
We thank Prof. W. Buzello for his critical reading of the manuscript and Drs. H. Knopf and H. Stützer for their statistical guidance.
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