Title: Motor block during patient-controlledepidural analgesia with ropivacaine or ropivacaine/fentanyl afterintrathecal bupivacaine for Caesareansection †
Abstract: We compared patient-controlled epidural analgesia(PCEA) with ropivacaine alone or combined with fentanyl in terms ofanalgesic efficacy, motor weakness and side-effects in patients whohad received spinal anaesthesia for elective Caesarean section. ASA Ipatients received combined spinal–epidural anaesthesia and wererandomly assigned, in a double-blind study, into two groups afteroperation: group R (n=23) received PCEA ropivacaine0.1%, bolus 5 mg, lockout 15 min,3 mg h−1 background infusion, and group RF(n=24) received PCEA 0.1% ropivacaine/fentanyl2 μg ml−1 at identical settings. Pain andsatisfaction on a 100 mm visual analogue scale (VAS) andside-effects were noted. Incidence of motor weakness (Bromagegrade 1 or higher) was 48% (11/23) at 8 h in group Rcompared with 13% (3/24) in group RF (P=0.025).Pain scores on movement were lower in group RF at 8 and 12 h and atrest at 6 and 8 h (P<0.05 for each comparison). Analgesicconsumption was less in RF (P=0.041), but there was nodifference in time to first request for supplementary analgesia. Patientsatisfaction with postoperative analgesia (mean (sd)) washigher in RF (79 (23) vs 57 (29) mm,P=0.045). Caution should be exercised using ropivacainePCEA after spinal bupivacaine for Caesarean section, because its reputedmotor-sparing property may be unreliable. We compared patient-controlled epidural analgesia(PCEA) with ropivacaine alone or combined with fentanyl in terms ofanalgesic efficacy, motor weakness and side-effects in patients whohad received spinal anaesthesia for elective Caesarean section. ASA Ipatients received combined spinal–epidural anaesthesia and wererandomly assigned, in a double-blind study, into two groups afteroperation: group R (n=23) received PCEA ropivacaine0.1%, bolus 5 mg, lockout 15 min,3 mg h−1 background infusion, and group RF(n=24) received PCEA 0.1% ropivacaine/fentanyl2 μg ml−1 at identical settings. Pain andsatisfaction on a 100 mm visual analogue scale (VAS) andside-effects were noted. Incidence of motor weakness (Bromagegrade 1 or higher) was 48% (11/23) at 8 h in group Rcompared with 13% (3/24) in group RF (P=0.025).Pain scores on movement were lower in group RF at 8 and 12 h and atrest at 6 and 8 h (P<0.05 for each comparison). Analgesicconsumption was less in RF (P=0.041), but there was nodifference in time to first request for supplementary analgesia. Patientsatisfaction with postoperative analgesia (mean (sd)) washigher in RF (79 (23) vs 57 (29) mm,P=0.045). Caution should be exercised using ropivacainePCEA after spinal bupivacaine for Caesarean section, because its reputedmotor-sparing property may be unreliable. Analgesic techniquesfor Caesarean section must be highly effective and yet allow earlymobilization to enable these women to care for their babies. Whilepatient-controlled epidural analgesia (PCEA) with local anaestheticsprovides good analgesia, it causes motor weakness, limiting postoperativemobilization.1Cooper DW Ryall DM McHardy FE et al.Patient controlled extradural analgesia with bupivacaine, fentanyl or a mixture of both, after Caesarean section.Br J Anaesth. 1996; 76: 611-615Crossref PubMed Scopus (50) Google Scholar Ropivacaine, the most recent amide local anaesthetic introduced intoclinical practice, reportedly produces less motor weakness thanbupivacaine.2Muldoon T Milligan K Quinn P et al.Comparison between extradural infusion of ropivacaine or bupivacaine for the prevention of postoperative pain after total knee arthroplasty.Br J Anaesth. 1998; 80: 680-681Crossref PubMed Scopus (53) Google Scholar Ropivacaine epidural analgesia after spinal anaesthesia has not beenreported. We compared PCEA ropivacaine alone or combined with fentanylafter Caesarean section under bupivacaine spinal anaesthesia, in terms ofanalgesic efficacy, motor weakness andside-effects. Afterobtaining institutional ethics committee approval and written informedconsent, 50 women scheduled for elective Caesarean section under regionalanaesthesia were enrolled into the study. Excluded were patients other thanASA I, patients for whom a central neuraxial block was contraindicatedand those with a history of adverse reaction to any study medication.Patients were briefed preoperatively on visual analogue scales (VAS) andhow to operate the PCEA. After i.v. access had been established andan infusion of crystalloid commenced, all patients had a combinedspinal–epidural (CSE) anaesthetic. The epidural space was identifiedat L2–3 or L3–4 using a loss of resistance to saline techniquewith the patient in a sitting position. Dural puncture was performed by aneedle-through-needle technique with a Whitacre 26G needle;hyperbaric 0.5% bupivacaine 2.6 ml was injected into the intrathecalspace. An epidural catheter was then inserted into the epiduralspace. When surgery was complete, patients were randomized, by asealed envelope technique, into one of two groups: group R(n=25) received PCEA 0.1% ropivacaine, bolus5 mg, lockout 15 min, with 3 mg h−1background infusion. Group RF (n=25) received PCEA0.1% ropivacaine/fentanyl2 μg ml−1, at identical settings to groupR. The analgesic regimen was prepared by the anaesthetist managing thepatient, who was not subsequently involved in data collection. It wascommenced in the recovery room while the spinal block was still effective.Patients and nursing staff were blind to the grouprandomization. Pain at rest and on movement (sitting forward) on a100 mm VAS at 2, 4, 6, 8, 12 and 24 h, satisfaction with postoperativeanalgesia at 24 h (VAS) and the incidence of nausea and pruritus wererecorded by the patients on a four-page individual patient diary.Dermatomal sensory level was noted using ethyl chloride spray at thecommencement of the study and at 8 h. Motor block was evaluated usinga modified Bromage scale by nursing staff who were familiar with theseassessments. If patients had inadequate analgesia, supplementary rescueanalgesia with oral codeine 30 mg/paracetamol 500 mg wasavailable. Total PCEA consumption was noted. Postoperative monitoringconsisted of hourly respiratory rate, pulse rate and non-invasiveblood pressure measurements for 4 h and thereafter at intervals of4 h. Hypotension was defined as systolic blood pressure<90 mm Hg. Sedation was assessed on a four-point scale:0=fully alert, 1=drowsy, eyes closed occasionally;2=asleep but roused easily on speaking to the patient;3=profoundly sedated, roused by physical stimulation. Datawere analysed in GraphPad PrismTM, version 2.0. Physicalcharacteristics and satisfaction scores were compared using the unpairedt-test. VAS pain and total analgesic consumption werecompared using the Mann–Whitney U-test. Contingencytables were constructed for categorical data and analysed byχ2 analysis with Yates' correction. The prospectivestudy power calculation was based on analgesic data. Previous studies ofwomen after Caesarean section indicated a standard deviation of the orderof 30 mm in early postoperative pain scores. We took a VAS reductionof 25 mm to be clinically significant, hence 24 patients were requiredin each group to give an α value of 0.05 and a β value of0.2. Although 25 patients were enrolled in each group, only 23 ingroup R and 24 in group RF were deemed eligible for statistical analysis.One patient was withdrawn from each group because of technical difficultieswith the epidural catheter. Another patient's data were lost fromgroup R because of PCEA provider pump failure. A further two patients werewithdrawn from the ropivacaine group at 12 h because of profound,prolonged motor block. They were included in the analysis as the onlymissing data were at 24 h. The two groups did not differ in age,weight or parity. Patients receiving ropivacaine alone had significantlyhigher VAS pain scores at 6 and 8 h at rest and at 8 and 12 h onmovement. Total analgesic consumption was less in the RF group than ingroup R and no patient in RF requested supplementary oral analgesiacompared with eight patients in group R (P=0.005). Therewas no difference in the time to first request for supplementary analgesia.Patients in group RF had significantly higher scores for satisfaction withtheir postoperative analgesia compared with group R(P=0.045) (Table 1).Table 1Physical characteristics, analgesia, motor weakness andside-effects. All data are expressed as mean (sd) or median(interquartile range) except where statedRopivacaine(n=23)Ropivacaine/fentanyl(n=24)Statistical significanceAge (yr)32.4 (5.5)28.5 (5.0)n.s.Weight (kg)80.4 (8.3)82.0 (11.2)n.s.Parity1 (0–3)1 (1–3)n.s.Total PCEA ropivacaine consumption in 24 h (mg)199 (23)175 (15)P=0.041Supplementary oral analgesia, n (%)8 (35%)0 (0%)P=0.005Time to supplementary analgesia (h)9.7 (2.7)6.6 (2.4)n.s.Pain VAS at rest, 6 h (mm)20 (13–40)8 (1–25)P=0.039Pain VAS at rest, 8 h (mm)24 (19–35)12 (2–5)P=0.047Pain VAS on movement, 8 h (mm)54 (34–60)35 (4–35)P=0.045Pain VAS on movement, 12 h (mm)53 (30–70)39 (20–55)P=0.049Patient satisfaction VAS (mm)57 (29)79 (23)P=0.045Motor weakness at 8 h, n (%) Bromage score=1 Bromage score=2 Bromage score=311 (48%) 6 (26%) 3 (13%) 2 (9%)3 (13%) 2 (8%) 1 (5%)0P=0.025 n.s. n.s. n.s.Motor weakness at 12 h, n (%) Bromage score=1Bromage score=2 Bromage score=36 (26%) 4 (17%) 0 2 (9%)2 (8%) 2 (8%) 0 0n.s. n.s. n.s. n.s.Sensory level at baselineT5 (T4–T10)T6 (T3–T10)n.s.Sensory level at 8 hT11 (T10–L2)T10 (T8–L1)n.s.Pruritus, n311P=0.033Hypotension, n22n.s.Nausea, n13n.s.Sedation score >1, n02n.s. Open table in a new tab The incidence of demonstrable motorweakness (Bromage grade 1 or above) was significantly higher(P=0.025) in group R than in group RF at 8 h but notat 12 h. When patients with Bromage grades 2 or 3 were analysedseparately, there was no statistical difference. No patient was allowed towalk if any motor weakness was detected. The two patients in group R whowere withdrawn at 12 h had fully recovered by 24 h. There was nodifference between the groups in sensory level at 8 h. Pruritus wassignificantly more likely in group RF than in group R(P=0.033), but no patient requested treatment. There wereno differences in the incidences of nausea, hypotension or sedation betweenthe groups (Table 1). This isthe first report, to our knowledge, of epidural ropivacaine for continuingpostoperative analgesia after spinal anaesthesia. The increasing use of CSEtechniques increases the possibility of epidural administration ofropivacaine after spinal anaesthesia with bupivacaine. The principalfinding is the unexpectedly high incidence and duration of motor blockobserved in patients receiving PCEA with ropivacaine. This observationdiffers from the initial clinical impression of ropivacaine, whichsuggested a motor-sparing effect.2Muldoon T Milligan K Quinn P et al.Comparison between extradural infusion of ropivacaine or bupivacaine for the prevention of postoperative pain after total knee arthroplasty.Br J Anaesth. 1998; 80: 680-681Crossref PubMed Scopus (53) Google Scholar However, a study of PCEA epidural0.125% ropivacaine compared with 0.125% bupivacaine in labourfound that they were clinically indistinguishable in terms of motorweakness.3Owen MD d'Angelo R Gerancher JC et al.0.125% ropivacaine is similar to 0.125% bupivacaine for labor analgesia using patient-controlled epidural infusion.Anesth Analg. 1998; 86: 527-531Crossref PubMed Google Scholar Wechose a background infusion of ropivacaine 0.1%, believing that itwould provide an acceptable balance between adequate analgesia and minimalmotor block. In retrospect however, it is clear that we failed in thisobjective because we underestimated the pain produced by Caesarean sectionin our patients. In a randomized, double-blind study of threesolutions of ropivacaine/fentanyl for PCEA after lower abdominalsurgery, 0.05% ropivacaine/fentanyl1 μg ml−1 produced equivalent analgesia to0.2% ropivacaine/fentanyl4 μg ml−1. However, the latter group had a30% incidence of motor block, compared with none in those receivingthe lower concentration of ropivacaine.4Liu S Moore J Luo A et al.Comparison of three solutions of ropivacaine/fentanyl for postoperative patient controlled analgesia.Anesthesiology. 1999; 90: 727-733Crossref PubMed Scopus (79) Google Scholar Our choice of ropivacaine 0.1% couldreasonably have been expected not to aggravate motor weakness. Moreover,recent work has shown that the relative potency of ropivacaine comparedwith bupivacaine is only 0.6 and the EC50 for the minimum localanaesthetic concentration for ropivacaine in labour is approximately0.16%.5Capogna G Celleno D Fusco P et al.Relative potencies of bupivacaine and ropivacaine for analgesia in labour.Br J Anaesth. 1999; 82: 371-373Crossref PubMed Scopus (230) Google Scholar Hence,0.1% ropivacaine should have been even less likely to produce motorblock than 0.1% bupivacaine. Although the difference isstatistically significant only when patients with all grades of motorweakness are included, this unexpected finding is clinically importantbecause even Bromage grade 1 weakness precludes ambulation.Inadvertent intrathecal spread of ropivacaine (via the small dural holecreated by the spinal component of the CSE) could possibly explain ourobservations, although there was no suggestion of dural puncture in any ofour patients. Indeed, it has been shown that dural puncture with a26 gauge Whitacre spinal needle before epidural injection (as in thepresent study) increases the caudal, but not the cranial, spread ofepidural local anaesthetics.6Suzuki N Koganemaru M Onizuka S Takasaki M Dural puncture with a 26-gauge spinal needle affects spread of epidural anesthesia.Anesth Analg. 1996; 82: 1040-1042PubMed Google Scholar It is also possible that low thoracicplacement of the epidural catheter may have been more appropriate. Repeatedintroduction of boluses of local anaesthetic into the lumbar area may notprovide analgesia in the lower thoracic dermatomes, yet accumulation mayincrease the risk of motor weakness in the lumbar dermatomes. Althoughthere is also greater sensitivity of neural tissue to local anaestheticsduring the later stages of pregnancy, this is an unlikely explanationbecause patients in group RF did not have as much leg weakness as those ingroup R. However, it is noteworthy that patients in group R received asignificantly higher dose of ropivacaine than patients in group RF over theduration of the study, presumably because their analgesia was lesssatisfactory than in group RF. An alternative explanation is aninteraction between the two local anaesthetics. An experimental model ofprofound nerve block under spinal anaesthesia found that combinations ofamide local anaesthetics could produce unpredictable prolongation of theblock. Although the mechanism is unclear, these investigators postulatedthat local anaesthetics could interact at the sodium channel to prolongeffective duration.7Hassan HG Youssef H Renck H Duration of experimental nerve block by combinations of local anaesthetic agents.Acta Anaesthesiol Scand. 1993; 37: 285-287Crossref Scopus (16) Google Scholar Whether this effect could be more pronounced on motor as opposed to sensorynerves is unknown. In conclusion, we found a higher incidence ofmotor weakness after 8 h in patients receiving PCEA ropivacainecompared with a ropivacaine/fentanyl mixture after bupivacaine spinalanaesthesia. The reason for this finding is unclear, but further studiesare indicated to clarify the optimum dose regimen of epidural ropivacaineand fentanyl after spinal anaesthesia. In the interim, caution should beexercised when administering epidural ropivacaine after bupivacaine spinalanaesthesia.