Caesarean section is the most common surgical procedure performed in the United States . Caesarean section rates currently reach 27.5% in the United States  and vary between 15 and 29% in Germany . General anaesthesia for caesarean section has been shown to be associated with higher maternal morbidity and mortality than regional anaesthetic techniques . Therefore, regional anaesthesia for caesarean section should be preferred when balancing the risks and benefits for the mother and her fetus. Both spinal anaesthesia and epidural anaesthesia (EDA) have been shown to provide effective anaesthesia for caesarean section [5,6]. A trend of preference for spinal anaesthesia for elective caesarean section [4,7] is, among others, thought to be due to the perceived advantages of simplicity of technique and density of spinal anaesthetic block .
Most of the trials comparing spinal anaesthesia and EDA for caesarean section were not randomized and focused solely on intraoperative pain . Considering the concept of preemptive analgesia , we were interested in the effects of regional anaesthesia for caesarean section on postoperative pain. The concept of preemptive analgesia is based on experimental findings that effective analgesia initiated before the onset of surgery could prevent effects that amplify postoperative pain . Different sites of action of local anaesthetics (and opiates) with differences in blocking central sensitization may contribute to a preemptive effect. In a clinical model, it was shown that spinal anaesthesia was able to suppress temporal summation, whereas EDA had only partial effects [10,11]; however, results of clinical studies regarding the value of preemptive analgesia are controversial .
We hypothesized that spinal anaesthesia, providing superior intraoperative pain relief, would result in less postoperative pain and analgesic requirements than would EDA. Therefore, we conducted a prospective randomized study in women scheduled for elective caesarean section to assess the influence of spinal anaesthesia or EDA on postoperative analgesic requirements as measured by patient-controlled epidural application of ropivacaine.
After approval by the Ethics Committee of the University of Bonn and written informed consent, we included 132 (ASA I or II) parturients at full term who wished to receive regional anaesthesia for elective caesarean section. All pregnancies were uncomplicated. The patients were prospectively randomized into two groups. One group received EDA and the other received spinal anaesthesia after insertion of an epidural catheter for postoperative patient-controlled epidural analgesia (PCEA). Parturients younger than 18 years, a history of allergy to local anaesthetics, bleeding tendency or those unable to grasp the concept of PCEA were excluded from the study. In cases of unilateral, failed or inadequate sensory block, either epidural anaesthesia was performed (in the spinal anaesthesia group) or an attempt to extend anaesthesia with a higher dosage of local anaesthetic in the EDA group was made. If this was unsuccessful, general anaesthesia was performed. In all these cases, the patient was excluded from the study protocol. Before surgery, patients were briefed on visual analogue scales (VASs) and the use of the PCEA device.
Prior to the neuraxial block, all patients received an intravenous infusion of 500 ml hydroxyethyl-starch. The use of intravenous vasoconstrictive medication (Akrinor, Arzneimittelwerk Dresden, Germany) in cases of hypotension or bradycardia after completion of the neuraxial block was left to the discretion of the attending anaesthesiologist.
Patients were placed in the sitting position and the epidural space was identified between L 2/3 or L 3/4 with the loss-of-resistance to saline technique using an 18-gauge Tuohy needle (B. Braun, Germany) in the EDA group or a double-barrelled 18-gauge Tuohy needle (EpiStar, Rüsch, Germany) in the spinal anaesthesia group, and a 20-gauge indwelling epidural catheter was advanced 5 cm into the epidural space. After aspiration for blood or spinal fluid, an epidural test dose of 12.5 mg isobaric bupivacaine 0.5% was injected. EDA patients then received ropivacaine 0.75% (7.5 mg per 10 cm height) and 10 μg sufentanil through the epidural catheter. In the spinal anaesthesia group, after insertion of the epidural catheter and application of the test dose, a 25-gauge pencil point needle was passed through the double-barrelled Tuohy needle using the needle-through-needle technique. Isobaric bupivacaine 0.5% (0.5 mg per 10 cm height) and 5 μg sufentanil were injected intrathecally without barbotage over a period of approximately 30 s. The start of the local anaesthetic technique was defined as t0, with the time of injection of local anaesthetic marking the completion of regional anaesthesia (t1). The onset time of the blockade was defined as the time between injection of the local anaesthetic and opiate and the sensory blockade reaching the sixth thoracic dermatome using touch appreciation (t1 − t2). Caesarean section was performed with the Misgav–Ladach technique  and was started immediately after T6 sensory block was achieved. Skin incision (t3) was defined as the start of surgery, delivery as umbilical cord clamping (t4), and completion of skin closure was defined as the end of surgery (t5). Apgar scores and cord blood gas analysis of neonates were evaluated by a paediatrician who was unaware of group assignment. Intraoperative pain was assessed after the delivery using a visual analogue pain scale (0 mm, no pain; 100 mm, worst imaginable pain).
After the operation, patients were transferred to the recovery room, where they stayed for 1 h and were then transferred to their rooms. Patients were routinely mobilized 6 h after surgery. For postoperative analgesia and to assess the amount of local anaesthetic requirements, all women received PCEA (Pegasus, LogoMed, Germany) at identical settings. This device was programmed to deliver a bolus of ropivacaine 0.133% with a lock-out period of 1 h according to the patient's height: 160 cm or less, 8 ml (11 mg); 161–165 cm, 9 ml (12 mg); 166–170 cm, 10 ml (13 mg); 170 cm or more, 11 ml (15 mg). Owing to clinical safety reasons, there was no baseline infusion and no shorter lock-out period chosen. If patients had inadequate analgesia with local anaesthetic via PCEA, supplementary analgesia with 100 mg rectal diclofenac was available on request without any limitation on time, but there was a restriction in total dose as recommended by the manufacturer. Postoperatively, all women were interviewed by an independent observer (who was unaware of the regional technique) at time points immediately after surgery, and at 1, 3, 6, 12 and 24 h postoperatively. Visual analogue pain scores (0 mm, no pain; 100 mm, worst imaginable pain) at rest, coughing and mobilization were obtained. At all time points, motor blockade was assessed using the modified Bromage score (0 = no paralysis, 1 = unable to raise extended leg, 2 = unable to flex knee, 3 = unable to flex ankle). Any motor blockade as shown by a Bromage motor score grade 1 or above was considered to be a corresponding adverse effect. For statistical analysis of Bromage scores, patients were divided into two groups: no motor blockade (=Bromage score 0) and any demonstrable motor blockade (=Bromage score 1 + 2 + 3). In cases of marked differences in the motor score between the two legs, the higher score was recorded because this is clinically relevant. Other parameters recorded were side-effects such as nausea, vomiting, pruritus, backache and headache. Sedation was assessed on a four-point scale: 0, fully alert; 1, drowsy; 2, asleep but roused easily on speaking to the patient; 3, profoundly sedated, roused by physical stimulation. Total PCEA consumption was recorded. The epidural catheter was removed if requested by the patient or if further pain treatment via PCEA was no longer necessary. At this time point, patients were questioned about their overall satisfaction with the anaesthetic technique used. Every parturient was visited on the first, third and fifth postoperative days to check for postdural puncture headache, defined as severe headache limiting daily activity.
A prospective study power calculation was performed, based on the primary endpoint, that is, local anaesthetic consumption at 12 h postoperatively, from a pilot study of 32 patients (spinal anaesthesia group 57.7 ± 10.9 mg, EDA group 63.3 ± 11.0 mg). A sample size of 61 patients in each group was determined to detect a difference of 5.6 mg of local anaesthetic consumption between both groups, with a within-group SD of 11 mg with a power of 80% and a type I error of 5% for the two-sided test. Statistical analyses were assessed using the Mann–Whitney rank sum, chi-squared or Student's t-test as appropriate. A P value less than 0.05 was considered to be statistically significant. For the 24 h observation period, the area under the curve (AUC) for pain was calculated as the sum of the VAS values [(pain at tn + 1 + pain at tn)/2] × [time (h) between tn and tn + 1] calculated for each interval between observations. Values are given as the mean ± SD for all continuous data that follow a Gaussian repartition except where stated. Non-Gaussian numerical data were expressed as median values and (CI25 − CI75) (including pain on the VAS).
The results of this study are presented according to the revised Consolidated Standards of Reporting Clinical Trials (CONSORT) Statement . A CONSORT flow chart is presented in Fig. 1.
One hundred and thirty-two patients were included in the study, and seven were subsequently excluded (reasons are shown in Fig. 1). Sixty-three patients in the EDA group and 62 in the spinal anaesthesia group completed the study and were deemed eligible for statistical analysis. Patients' characteristics are shown in Table 1. More women with spinal anaesthesia had had previous central neuroaxial blocks for labour analgesia or other surgery. Although the onset of sensory block was significantly faster in parturients with spinal anaesthesia, time to delivery and total duration of surgery did not vary between the groups. During surgery, no patient needed additional intravenous analgesia; however, women given EDA rated their pain higher on the VAS during surgery (Table 2).
Consumption of ropivacaine by PCEA did not differ between the groups (Table 2); however, significantly more women with EDA received supplemental analgesic medication and the overall dosage of rectal diclofenac per patient was higher in them (Table 2).
For the whole period of 24 h postoperatively, the AUC of VAS scores at rest was significantly higher in the EDA group [600 (361.5–823.0)] than in the spinal anaesthesia group [379.8 (250.0–602.5)] (P = 0.0002). Furthermore, the AUC of VAS scores during mobilization and coughing for the 24 h observation was significantly higher in the EDA group [1166 (868.5–1380)] than in spinal anaesthesia group [795.5 (580.9–1116)] (P < 0.0001). At single time points, analgesia at rest and during mobilization and coughing was comparable between both the groups only immediately and 3 h after surgery (Fig. 2). At all other time points, women with EDA had higher pain scores (P < 0.05).
No patient had bradycardia. Twenty-six women in the spinal anaesthesia group and 24 in the EDA group received vasoconstrictive medication as a single intravenous bolus dose after completion of the neuraxial block (Table 3). Apart from short periods of less than 2 min duration of hypotension (systolic blood pressure <80 mmHg) being observed in five women in the spinal anaesthesia group and six in the EDA group, all women remained haemodynamically stable throughout the procedures.
The modified Bromage motor score was comparable for the intraoperative period between the groups. The incidence and duration of demonstrable motor weakness (Bromage grade 1 or above) was significantly lower in parturients with spinal anaesthesia (P < 0.05) during the study period except at 24 h after surgery (Fig. 3). Pruritus was the most common adverse effect in both groups (Table 3). Although more women with spinal anaesthesia had pruritus, none of them requested treatment for it. More parturients with EDA had vertigo and backache at least at one measuring time point (Table 3). Interestingly, the number of patients complaining of backache increased continuously over 24 h and the highest rate was reached after 24 h (29 with EDA versus 17 with spinal anaesthesia, P < 0.05). The incidence of headache was similar in both groups and there were no cases of postdural puncture headache within the first 24 h; however, two patients with spinal anaesthesia complained of postdural puncture headache 3 days after surgery. In these patients, the epidural catheter became dislodged in the earlier postoperative course. The rate of sedation, nausea and vomiting was comparably low in both groups throughout the first postoperative day. There were no instances of nausea or vomiting requiring treatment. Nevertheless, in the EDA group, more patients experienced nausea than in the spinal anaesthesia group. This difference was not statistically significant. Neonatal outcome was comparable among the groups (data are not shown).
The present study was designed to compare the effects of spinal anaesthesia and EDA on postoperative analgesic requirements as measured by PCEA application of ropivacaine during the first 24 postoperative hours in women undergoing elective caesarean section. We found that overall consumption of postoperative epidural ropivacaine was similar in both groups of patients; however, postoperative pain and the use of additional diclofenac as well as the intensity of motor blockade were increased after EDA compared with spinal anaesthesia.
Regional anaesthesia is increasingly used in women scheduled for elective caesarean section [1,4]. Although both spinal anaesthesia and EDA have been shown to provide effective anaesthesia during surgery , many parturients continue to experience inadequate postoperative analgesia . In experimental studies, it has been shown that the quality of intraoperative anaesthesia can affect postoperative analgesia. The different sites of action of local anaesthetic and opiates may result in a difference in the quality of blockade and suppression of temporal summation, which is considered to be the first step in central sensitization. It has been shown that spinal anaesthesia is superior to EDA in this respect [10,11]. This may indicate that spinal anaesthesia is more likely to have preemptive effects; however, clinical studies have resulted in controversial findings as regards the effects of preemptive analgesia on postoperative pain .
The primary endpoint of the study, that is, local analgesic consumption as measured by PCEA, was not reached; this was probably caused more by a lack of power than an absence of effect between the different anaesthesia techniques. In fact, interesting secondary endpoints of the study are that subjective pain assessments (pain score rated on a VAS at rest and during coughing and mobilization) were improved in women with spinal anaesthesia throughout the first 24 h postoperatively and women with EDA requested more supplemental diclofenac as analgesic medication owing to insufficient analgesia during the first postoperative day. Although none of the regional blocks performed in this study had to be supplemented by intravenous analgesics during surgery and intraoperative analgesia was rated higher during spinal anaesthesia than during EDA, the difference in postoperative analgesia might therefore be explained by a better preemptive analgesic effect of spinal anaesthesia. It remains unclear, however, whether experience of previous central neuroaxial block may have influenced the pain assessment with a VAS.
Opiates are commonly added to intrathecal or epidural local anaesthetics in caesarean section to enhance and prolong intraoperative and postoperative analgesia . In this study, combinations of local anaesthetic and sufentanil were administered. Although there are numerous scientific publications using epidural and intrathecal sufentanil in combination with local anaesthetics for caesarean section, previous equipotency studies compared different opiates applied via the same spinal route . A comparison of different routes of administration of equal doses of sufentanil has shown that sufentanil provides superior analgesia when given intrathecally than when given epidurally . Equipotency studies using sufentanil are still lacking and, to the best of our knowledge, only morphine has been tested for such comparisons [19,20]. Here, we used 10 μg of sufentanil for EDA and 5 μg of sufentanil for spinal anaesthesia as in our regular clinical practice; however, this might be a limitation of the study, because we are unaware of equipotent dosages. Furthermore, lipophilic opiate agents injected epidurally are quickly absorbed in the systemic circulation  and thus can also act supraspinally [22,23]. A segmental effect is suspected, however, as they lower the minimum concentration of local anaesthetics better than they do when they are given systemically  and they also act on temporal summation . It can be argued that these segmental effects may be stronger with intrathecal administration; however, our study is not suitable to answer this question.
In the parturients with spinal anaesthesia, the epidural catheter was placed before surgery and dural puncture was performed by the needle-through-needle technique. There was no case in which epidural augmentation of spinal anaesthesia was necessary during surgery. This good result of spinal anaesthesia may have been influenced by the dosages and the volume used in our protocol. In accordance with our results, a very recent study using a dosage regimen of intrathecal bupivacaine resulting in quite similar doses of plain bupivacaine according to the patient's height showed good analgesia even during caesarean section . As expected, spinal anaesthesia established surgical anaesthesia more rapidly; however, this did not influence time to delivery, duration of surgery or neonatal outcomes. Like the earlier onset of surgical anaesthesia with spinal anaesthesia, postoperative analgesia wears off even faster than EDA. As a consequence, residual surgical analgesia may have accounted for the lower pain in patients with EDA at 1 h after surgery. Although good postoperative analgesia with PCEA settings was provided during the whole study period at rest in both groups, patients in the EDA group rated their pain at mobilization or coughing unacceptably high between 6 and 24 h after surgery. Therefore, more women in the EDA group required a greater dosage of diclofenac as a supplemental medication. A single-dose diclofenac suppository, administered immediately after surgery, can reduce postcaesarean PCEA requirements ; however, our study was not designed to find such an effect.
The major safety concern with PCEA is an intrathecal application of local anaesthetics, in the very rare case of unintended secondary epidural catheter displacement. Another possible side-effect is respiratory depression caused by opiates. Nevertheless, most of the protocols for postoperative PCEA use background infusion [28,29], with quite often the addition of low-dose opiates . To assure patients' safety, we used no background infusion and limited PCEA ropivacaine boluses to 11–15 mg, which is less than the estimated ED50 for spinal ropivacaine (16.7 mg) in caesarean section . Furthermore, we did not use opiates for PCEA. In this PCEA setting, in some patients, we observed ‘breakthrough pain’ with higher VAS pain scores at 18 h after surgery, which was mainly during the night, since elective surgery was scheduled and performed in most cases before noon. It must be argued that the observed quality of analgesia could have been improved by using a background infusion or with the addition of low-dose opiates.
One major drawback of regional blocks is prolonged motor blockade; however, any motor block precludes patients from ambulation. We chose no background infusion of ropivacaine for postoperative analgesia, believing that a bolus administration would provide an acceptable balance between adequate analgesia and minimal motor block. Although overall consumption of ropivacaine was similar in both groups, however, there was a trend towards an increased use of ropivacaine by repeated boluses of local anaesthetic in the EDA group, presumably because their analgesia was less satisfactory. This may have aggravated frequency, intensity and duration of motor weakness in these patients during the first postoperative day.
The incidence of pruritus after epidural or intrathecal opiates is a side-effect that occurs with a frequency ranging between 20 and 80% and little preventive treatment is available . The observed rate of pruritus in our patients was within the reported range . As we expected, it was more frequent after spinal anaesthesia with intrathecal administration of sufentanil. None of these patients wished to be treated for itching. Nevertheless, pruritus is a very important clinical side-effect. Recently, it has been shown that reducing the dose of intrathecal sufentanil to 1.5 μg (as compared to 2.5 or 5 μg) in combination with hyperbaric bupivacaine provides comparable intraoperative and postoperative analgesia while preventing itching as side-effect .
Nausea and vomiting occurred less frequently and did not differ between groups. Parturients have the greatest risk of postdural puncture headache. In our study, we used 25-gauge pencil-point needles for spinal anaesthesia. No patient complained of postdural puncture headache on the first postoperative day, which is in contrast to previous findings of about 2.5% of patients reporting postdural puncture headache . This difference may be caused by the volume of local anaesthetics that was injected into the epidural space, thereby increasing the epidural pressure at the site of dural puncture. This hypothesis is supported by the fact that we observed postdural puncture headache in two patients more than 24 h after surgery. In both women, the epidural catheters became dislodged inadvertently.
In summary, we found that both spinal anaesthesia and EDA are reliable and well tolerated regional anaesthesia techniques for elective caesarean section; however, surgical anaesthesia was more complete with spinal anaesthesia than with EDA. Although the primary endpoint of the study, a reduction in regional analgesic consumption after spinal anaesthesia as compared with EDA, was not reached, spinal anaesthesia resulted in better intraoperative and postoperative pain relief, and decreased use of additional medication with the nonsteroidal analgesic diclofenac. We did not observe any severe side-effects with either spinal anaesthesia or EDA. After spinal anaesthesia, motor blockade was less frequent and intense during most time points on the first postoperative day, which is very important for mothers because it facilitates ambulation and early maternal–infant bonding .
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Keywords:© 2009 European Society of Anaesthesiology
anaesthetic techniques; analgesia; anaesthesia; epidural; obstetrics; patient-controlled; postoperative; preemptive; spinal