Interscalene patient-controlled analgesia (PCA) after shoulder surgery was shown to provide better pain relief and a higher degree of patient satisfaction compared with IV PCA with opioids.1 After major open shoulder surgery, ropivacaine 0.2% was associated with better preservation of strength in the hand and less paresthesia in the fingers than bupivacaine 0.15%, while providing comparable analgesia.2
The influence of 2 different concentrations of ropivacaine used for perineural interscalene postoperative analgesia after open rotator cuff repair has not been reported. The aim of this study was to compare ropivacaine 0.3% versus ropivacaine 0.2% with regard to the quality of postoperative analgesia. We hypothesized that there would be better postoperative analgesia with similar degree of motor block in the hand and paresthesia in the fingers with ropivacaine 0.3% compared with 0.2%. The primary outcome was postoperative IV morphine consumption 24 hours after the initial ropivacaine administration through the interscalene catheter.
After obtaining approval of the local ethical committee (Kantonale Ethikkommission, Gesundheitsdirektion des Kantons Zürich) and written informed consent, 80 adult patients of both sexes (classified as ASA physical status I–III, aged 18–75 years, and weight 50–100 kg) scheduled for elective open rotator cuff repair were included. Exclusion criteria before the study were severe bronchopulmonary disease, myocardial infarction within the last 6 months, hemostasis abnormality, known allergy to 1 of the trial drugs, known neuropathy, or neurologic damage to the brachial plexus. Randomization was performed during preanesthetic preparation the day before surgery. Patients were randomized according to a computer-derived list to receive either ropivacaine 0.3% (group 0.3%) or ropivacaine 0.2% (group 0.2%) for continuous postoperative interscalene analgesia. Patients were excluded after randomization in case of inadequate placement of the interscalene catheter or accidental catheter removal before the end of data assessment. The day before the operation, patients were instructed on how to use the IV PCA device with morphine for postoperative rescue analgesia.
All patients received oral premedication with 0.1 mg/kg midazolam 1 hour before the start of the anesthetic procedure. In the induction room, monitoring (electrocardiography, blood oxygen saturation, and noninvasive arterial blood pressure) was applied and an 18-gauge IV catheter was inserted in the arm not requiring surgery. The interscalene brachial plexus catheter was placed before induction of general anesthesia. Skin disinfection was performed with a 2-layer application of an alcoholic povidone-iodine solution (Betaseptic®; Mundipharma, Basel, Switzerland). After local anesthetic skin infiltration with lidocaine 1%, the interscalene brachial plexus was identified according to the modified lateral approach.3 The proximal end of the 21-gauge, 70-mm, short-bevel needle (Polymedic®; Polyplex, Te me na, Carnières-sur-Seine, France) was connected to a nerve stimulator (Stimuplex HNS 11®; B. Braun Melsungen AG, Melsungen, Germany), operated by the second person. The initial nerve stimulator setting was 1.4-mA current intensity, 0.1-millisecond impulse duration, and 2-Hz impulse frequency. The final needle position was considered successful when a contraction of the deltoid or proximal triceps muscle was obtained with a minimal current output between 0.3 and 0.4 mA and an impulse duration of 0.1 second. A 20-gauge interscalene catheter (Polymedic; Polyplex, Te me na, Bondy, France) was placed with the cannula-over-needle technique and advanced 3 cm over the tip of the needle. After subcutaneous tunneling through an 18-gauge IV catheter for 4 to 5 cm, the interscalene catheter was fixed with transparent adhesive tape and connected to a microfilter (200 nm). At that time, the initial interscalene block was performed preoperatively through the interscalene catheter with 40 mL ropivacaine 0.5% (200 mg). Before general anesthesia, the block was assessed and considered successful if a sensory block (inability to recognize cold) involving the supraclavicular, axillary, radial, and median nerves and a motor block involving the axillary (arm abduction), radial (forearm extension), and musculocutaneous (forearm flexion) nerves were present within 30 minutes after the administration of the local anesthetic.
General anesthesia was performed with propofol target-controlled infusion (Diprifusor including the Marsh program for propofol, Graseby pump; Sims Graseby Ltd., Watford, Hertfordshire, UK). Fentanyl 0.25 μg/kg and rocuronium 0.9 mg/kg were given to facilitate endotracheal intubation. Rocuronium supplementation was given as necessary. After induction of general anesthesia, all patients received 1 g acetaminophen IV, which was repeated every 6 hours until the end of the study. No additional drug was administered through the interscalene catheter during the operative procedure. In all patients an open rotator cuff repair was performed by the same surgeon, with or without tenotomy of the biceps muscle, but without transfer of the latissimus dorsi muscle.
At the end of surgery, patients were tracheally extubated and transferred to the postanesthesia recovery unit. Patients were connected to the IV PCA device filled with morphine 1 mg/mL for rescue analgesia. The initial setting of the device was 2-mL bolus and lockout time of 10 minutes without basal infusion. Four hours after the initial interscalene bolus (T0), continuous infusion through the interscalene catheter was started for 48 hours (until T48) with an infusion rate of 14 mL/h in both groups. The pumps and syringes containing either ropivacaine 0.3% or ropivacaine 0.2% were prepared by our pharmacist. The syringes of both groups were identical, and the patient, the attending anesthesiologist, and the study nurse were unable to identify patients' group assignment. When patients fulfilled the criteria of the modified Aldrete score,4 they were transferred to the ward.
The following variables were assessed in all patients by a study nurse blinded to the study drug concentration: total postoperative IV morphine consumption through the PCA device separately for the time periods T0 to T24 and T24 to T48; the time to first IV morphine bolus through the PCA device; and postoperative pain intensity in the operated shoulder at rest and with motion by the means of a visual analog scale ranging from 0 (no pain) to 100 (worst pain imaginable) every 8 hours postoperatively until T48 and motion was defined as passive inward and outward rotation of the arm and passive elbow flexion, guided by a physiotherapist. Handgrip strength was measured in the hand of the operated arm by means of a standard electronic pressure sensor and a soft rubber bulb, “the bulb grip device”2 (Appendix 1). Measurements were performed preoperatively, at T24, T48, and 6 hours after the end of continuous ropivacaine infusion (T54). Motor block (normal, weakened, or no motor function) in the hand of the operated arm was assessed at T24, T48, and T54 by asking the patient to adduct the thumb and to flex or to extend the fingers to test the function of the ulnar, median, and the radial nerves. The presence of paresthesias in the tip of the fingers of the operated arm was recorded at T24, T48, and T54. Sleep quality was assessed by patient awakening during the first postoperative night. Only patients awakening because of pain and asking for supplementary analgesia was recorded. Other disturbances interfering with sleep were not considered. Side effects such as nausea, vomiting, pruritus, hoarseness, and Horner syndrome were noted. Patients were interviewed by phone call 1 month later about the presence of paresthesia or any other sensory or motor deficit.
Based on our previous experience using interscalene PCA with ropivacaine 0.2%, interindividual variation of postoperative IV morphine consumption after open rotator cuff repair is approximately 50%. A 35% reduction of morphine consumption during the first 24 hours in patients receiving ropivacaine 0.3% was considered significant. Based on these data, a power analysis indicated that a sample size of 32 patients per group would be sufficient to have an 80% power at the 95% significance level. To increase the power, we decided to include 40 patients per group.
Demographic and surgical data were compared with the Mann-Whitney test. Visual analog scale values, morphine consumption, and muscle strength were analyzed with the Mann-Whitney test with Bonferroni correction for multiple repeated measurements. Side effects, the incidence of paresthesias, and motor block were analyzed with the χ2 test. Results are expressed as mean ± SD if not otherwise specified. For all determinations, a P value <0.05 was considered significant.
Eighty-two patients were randomized (41 in each group). In both groups, 1 interscalene catheter was accidentally removed at 20 and 32 hours postoperatively, respectively. Forty patients in each group completed the study and their data were analyzed. A patient flow diagram according to the CONSORT (Consolidated Standards of Reporting Trials) statement5 is presented in Figure 1. There was no difference between the groups regarding demographic patient data and data about the operative procedure (Table 1). All of the continuous ropivacaine infusions were maintained over 48 hours at a constant rate. The total amount of ropivacaine infused during the study was 2016 mg and 1344 mg in group 0.3% and group 0.2%, respectively.
No patient needed supplementary analgesics during surgery in either group. Total IV morphine consumption from T0 to T24 and T24 to T48 was significantly reduced in group 0.3% (7 ± 7 mg and 4 ± 4 mg, respectively) compared with group 0.2% (14 ± 9 mg and 16 ± 17 mg, respectively). In group 0.3%, the first morphine bolus was required at 20 ± 9 hours (range, 8–36 hours) postoperatively. This was significantly later than in group 0.2%, in which patients demanded the first morphine bolus 8 ± 2 hours (range, 1–11 hours) postoperatively (P < 0.02).
Pain at rest and pain with motion were not different between the 2 groups throughout the study. The relative decrease of the strength at T24, T48, and T54 was similar between the 2 groups. There was no statistically significant difference in the handgrip strength between the groups at T24, T48, and T54 compared with the preoperative values. At T48, significantly more patients in group 0.3% had weakened thumb adduction and weakened flexion of the second and third fingers (Table 2). All other measurements showed no difference between the groups.
The incidence of postoperative paresthesias was similar between the 2 groups. The number of patients awakened during the first postoperative night because of pain was significantly higher (27%) in the 0.2% group (95% confidence interval, 13.6% to 41.4%) than in the 0.3% group (5%) (95% confidence interval, −1.7% to 11.7%). The occurrence of side effects (9 in group 0.3% vs 8 in group 0.2%) was similar between groups. At 1 month, no patient complained of residual paresthesia or the occurrence of new sensory or motor deficit.
This study demonstrated that after open rotator cuff repair, continuous interscalene analgesia with ropivacaine 0.3% compared with ropivacaine 0.2% provided a significant reduction of morphine consumption and better sleep quality for the first postoperative night without increasing the intensity of motor block. The only significant difference was weakened thumb adduction and flexion of the second and third fingers at 48 postoperative hours in the 0.3% ropivacaine group.
The effects of volume and concentration of local anesthetics for continuous central or perineural analgesia are still a matter of controversy. Clinical studies have shown conflicting results as to whether similar results can be obtained by increasing either the volume or the concentration without considering the surgeon and the type of surgery.6,7 To avoid the bias of type of surgery, we decided to include only 1 type of surgery, open rotator cuff repair, a moderate to severely painful surgery8 performed by single surgeon. A large initial bolus (40 mL) was chosen to provide complete interscalene block making supplementary application of analgesics unnecessary during surgery. To avoid the possible confounding factor induced by the patient (use of PCA pump), a continuous infusion of ropivacaine without the option of patient-controlled doses was chosen for this study, despite evidence that patient-controlled doses improve analgesia for this type of surgery.9 Moreover, fixed-rate infusion is the optimal way to compare different local anesthetic concentrations. The rate of infusion of 14 mL/h was chosen according to our previous experiences in this surgical context, considering the basal rate and the average number of demanded doses.2
The hand grasp was chosen to assess motor function because this is the most reliable way to assess this variable after rotator cuff repair. Hand grasp depends on both median and ulnar functions and, although ulnar function is likely to be less affected with interscalene analgesia, this test remains clinically valid because hand weakness and paresthesia and dysesthesia in the fingers are the symptoms that generate patient complaints. In our data, hand grasp was not different between groups at any time, despite weakened thumb adduction and finger flexion in the 0.3% group observed at 48 hours. Although this difference was statistically significant, it was likely too small to influence the overall strength of the hand grasp. Ropivacaine 0.2% was selected as the “control” group because this concentration was shown, compared with bupivacaine 0.15%, to provide similar postoperative analgesia and better preservation of strength in the hand and less paresthesia in the fingers.2
Several studies have investigated the role of volume and concentration after shoulder surgery, but all have involved patient-controlled boluses, complicating a direct comparison with our results. Ilfeld et al.10 compared ropivacaine 0.2% with a basal rate of 8 mL/h and a 2-mL patient-controlled bolus available each hour with a basal rate of 4 mL/h and 6-mL bolus dose after moderately painful surgery. The authors found that decreasing the basal rate from 8 to 4 mL/h provided similar analgesia, but increased the incidence of breakthrough pain and sleep disturbance and was associated with less patient satisfaction. This study emphasizes the importance of volume in the context of shoulder surgery, in agreement with our work whereby multiple nerves (suprascapular, axillary, and supraclavicular) need to be blocked to provide analgesia after open shoulder surgery,11 making volume of local anesthetic a critical issue.
In this study, we showed that sleep quality during the first postoperative night was significantly better in the 0.3% ropivacaine group. This is most likely explained by the smoother transition provided by 0.3% ropivacaine when the initial block performed with 0.5% ropivacaine resolved. This was also shown by Ilfeld et al.10,12 who observed that patients receiving a lower basal infusion through an interscalene catheter experienced more frequent sleep disturbances and breakthrough pain.
The absence of significant difference between the 2 groups concerning morphine-induced side effects can be explained by, first, the relatively low consumption of morphine in both groups making the occurrence of side effect less likely.13 Second, the study was not powered to assess this outcome making a type I error possible.
At 1 month, no patient in either group had persistent paresthesia/dysesthesia or the appearance of new sensorimotor deficit, which is in accordance with previous results.3
In conclusion, this study showed that the application of 0.3% ropivacaine compared with 0.2% after open rotator cuff repair reduced morphine consumption and improved the quality of the first postoperative night without increasing the intensity of motor block assessed by hand grasp or side effects. The results of this investigation suggest that the use of 0.3% ropivacaine through an interscalene catheter during the first 24 hours after this surgery may be beneficial for the patient.
1. Borgeat A, Schappi B, Biasca N, Gerber C. Patient-controlled analgesia after major shoulder surgery: patient-controlled interscalene analgesia versus patient-controlled analgesia. Anesthesiology 1997;87:1343–7
2. Borgeat A, Kalberer F, Jacob H, Ruetsch YA, Gerber C. Patient-controlled interscalene analgesia with ropivacaine 0.2% versus bupivacaine 0.15% after major open shoulder surgery: the effects on hand motor function. Anesth Analg 2001;92:218–23
3. Borgeat A, Dullenkopf A, Ekatodramis G, Nagy L. Evaluation of the lateral modified approach for continuous interscalene block after shoulder surgery. Anesthesiology 2003;99:436–42
4. Aldrete JA. The post-anesthesia recovery score revisited. J Clin Anesth 1995;7:89–91
5. Altman DG, Schulz KF, Moher D, Egger M, Davidoff F, Elbourne D, Gotzsche PC, Lang T. The revised CONSORT statement for reporting randomized trials: explanation and elaboration. Ann Intern Med 2001;134:663–94
6. Brodner G, Buerkle H, Van Aken H, Lambert R, Schweppe-Hartenauer ML, Wempe C, Gogarten W. Postoperative analgesia after knee surgery: a comparison of three different concentrations of ropivacaine for continuous femoral nerve blockade. Anesth Analg 2007;105:256–62
7. Ilfeld BM, Loland VJ, Gerancher JC, Wadhwa AN, Renehan EM, Sessler DI, Shuster JJ, Theriaque DW, Maldonado RC, Mariano ER. The effects of varying local anesthetic concentration and volume on continuous popliteal sciatic nerve blocks: a dual-center, randomized, controlled study. Anesth Analg 2008;107:701–7
8. Bonica JJ Postoperative pain. In: Bonica JJ ed. The Management of Pain. 2nd ed. Philadelphia: Lea & Febiger, 1990:461–80
9. Singelyn FJ, Seguy S, Gouverneur JM. Interscalene brachial plexus analgesia after open shoulder surgery: continuous versus patient-controlled infusion. Anesth Analg 1999;89:1216–20
10. Ilfeld BM, Morey TE, Wright TW, Chidgey LK, Enneking FK. Interscalene perineural ropivacaine infusion: a comparison of two dosing regimens for postoperative analgesia. Reg Anesth Pain Med 2004;29:9–16
11. Borgeat A, Ekatodramis G. Anaesthesia for shoulder surgery. Best Pract Res Clin Anaesthesiol 2002;16:211–25
12. Ilfeld BM, Morey TE, Wright TW, Chidgey LK, Enneking FK. Continuous interscalene brachial plexus block for postoperative pain control at home: a randomized, double-blinded, placebo-controlled study. Anesth Analg 2003;96:1089–95
13. Roberts GW, Bekker TB, Carlsen HH, Moffatt CH, Slattery PJ, McClure AF. Postoperative nausea and vomiting are strongly influenced by postoperative opioid use in a dose-related manner. Anesth Analg 2005;101:1343–8
APPENDIX 1: DESCRIPTION OF HANDGRIP STRENGTH MEASUREMENT
Hand strength was measured by means of a soft rubber bulb, the “bulb grip device,” connected to an electronic pressure transducer (Abbott Critical Care Systems, Abbott, Dublin, Ireland). The bulb could be held in the hand and squeezed comfortably and was filled with water to offer resistance. The rubber bulb is oval shaped, as commonly used for inflating the pneumatic cuff of a conventional sphygmomanometer. The inlet to the bulb was sealed with a plug after being filled with water. The hydrostatic pressure, which increased on being squeezed, was measured with the pressure transducer connected to the bulb outlet. The transducer delivered an analog electrical signal, directly proportional to the pressure. The pressure transducer was of the electrical resistance type, using a Wheatstone bridge circuit. The bridge was supplied from a 5-V stabilized DC source and its output amplified by means of a DC amplifier (3100) before being led to a chart recorder (Watanabet type WX 441; Watanabe Instrument Corp., Tokyo, Japan) adjusted to 0.1 V/cm sensitivity and set to a sweep rate of 1 cm/s.
The system was calibrated by use of a Bourdon-type manometer with a range of 0 to 760 mm Hg that allowed pressure to be read from a scale, graduated in steps of 10 mm Hg, simultaneously. For the purpose of calibration, an external source of pressure that could be adjusted by means of a valve was also connected to the system. The pressure was adjusted in steps of approximately 50 mm Hg from 0 to 650 mm Hg, and the output voltage was recorded. The output signal exhibited a linear relationship of 729 mm Hg/V, or 72.9 mm Hg/cm on the chart recorder. Analysis of 4 calibration sequences showed a linear regression coefficient of 0.996 with a standard deviation of 617.7 mm Hg. The sensitivity of the device was mainly determined by the chart recorder, which could easily be read to within 61 mm (corresponding to 67 mm Hg). Because the grip strength is dependent on the position of the limbs, the control measurement (preoperative value) was taken in the postoperative position. All patients were able to use the device. The measurement was repeated at T24, T48, and T54. Each measurement was repeated 3 times and the one with the highest reading was chosen.© 2010 International Anesthesia Research Society