Bupivacaine and ropivacaine are widely used to provide efficient epidural analgesia in labour. The degree and duration of motor block is significantly lower using ropivacaine compared with bupivacaine in equal concentrations [1-3]. The concomitant use of opioids potentiates the effect, thus permitting the use of very low concentrations of local anaesthetic and so decreasing their side-effects, such as hypotension and motor block . The present study compared the effects of fentanyl added to low doses of bupivacaine or ropivacaine. Analgesia was provided for females in labour using patient-controlled epidural analgesia (PCEA); we studied both maternal and fetal haemodynamic variables, maternal arterial oxygen saturation (SPO2), and potency in the sense of analgesic quality as well as motor block.
Informed patient consent was obtained together with approval from the Hospital Ethics Committee for the randomized, double-blind study. There was no contraindication to regional anaesthesia. Forty nulliparous pregnant females ASA I and II, who were at ≥37 weeks' gestation, were allocated randomly into two groups to receive bupivacaine + fentanyl (Group 1) or ropivacaine + fentanyl (Group 2). All patients enrolled were of height >150 cm and body weight <100 kg. Each had a singleton fetus as a vertex presentation, had active regular contractions (at 50-70 mmHg) every 3-4 min lasting for 1 min, and the cervix was dilated to 4-5 cm. The age, weight, height, education and occupation of patients were noted. Patients with diabetes mellitus, neurological disease, pre-eclampsia or history of allergy were excluded. Patients had been taught the use of a patient-controlled analgesia device using a visual analogue scale (VAS) (0: no pain; 10: most severe pain). They were asked to inform us when they felt perianal fullness.
Systolic (SAP) and diastolic (DAP) arterial pressures, heart rate (HR) and SPO2 were monitored and the VAS scores noted. Uterine contractions and fetal heart sounds were monitored by an external cardiotocograph monitor (HP 8040A®; Hewlett Packard, Palo Alto, CA, USA). Normal saline (0.9% NaCl) solution was infused through an intravenous (i.v.) cannula (22 G) at 10 mL kg−1; the patients were then placed in the sitting position and an epidural block performed at the L3-4 or L4-5 interspace using the loss of resistance to saline technique and an epidural catheter inserted. Fentanyl 50 μg (1 mL) was added to bupivacaine 10 mL 0.125% and a total bolus dose of 11 mL solution was given epidurally to the Group 1 patients. Similarly fentanyl 50 μg was added to ropivacaine 0.125% 10 mL and administered epidurally to the Group 2 patients. Ten minutes later, PCEA was started (Abbott Pain Management Provider®; Abbott Laboratories, Beykoz, Istanbul, Turkey). An epidural infusion was started at a basal rate of 10 mL h−1: in Group 1, bupivacaine 0.05% + fentanyl 1.5 μg mL−1; in Group 2, ropivacaine 0.05% + fentanyl 1.5 μg mL−1. When necessary, a 10 mL bolus infusion could be given with a lockout time of 20 min. The total amount of drug (bolus + infused) was set to be 80 mL 4 h−1.
Maternal arterial pressures (SAP, DAP), HR, SPO2, fetal HR (FHR) and frequency of uterine contractions were noted before the epidural anaesthesia was started, and at 5, 10, 15, 20, 25 and 30 min and then every 15 min until delivery. The characteristics of the pains of contraction were noted, using the VAS, before starting epidural anaesthesia and at 5, 10, 15, 20, 25, 30, 45 and 60 min and thereafter every 30 min.
The degree of motor block in the lower extremities was tested by using a modified Bromage scale (scale of 0-3, where 0: ability to flex the knees and feet fully; 1: just able to flex the knees; 2: able to move the feet only; and 3: inability to move feet or knees). Sensory block was assessed, by loss of pinprick sensation, at 5, 10, 15, 20, 25, 30, 45 and 60 min and every 30 min thereafter until full cervical dilatation. We planned to stop the epidural infusion if the sensory block reached beyond T9.
The type of delivery (spontaneous, instrumental, Caesarean section), the duration of the first and second stage of labour, the total infusion time and volume of infusion (mL) were noted. Side-effects, e.g. severe hypotension, nausea, vomiting, systemic toxic reactions, fetal bradycardia, respiratory depression and second-degree motor block, were noted by the anaesthesiologist in the intrapartum period. Just after delivery, a sample was taken from the umbilical artery for blood-gas analysis. Apgar scores were noted at 1 and 5 min.
Statistical analysis was performed using: t-test for demographic and parametric data; a paired t-test for interpretation within groups; U-test for comparison of pain scores; χ2-test for non-parametric data; t-test for comparison of time and volume of infusion, the duration of stages (1 and 2) of labour and blood-gas status. P < 0.05 was taken to be significant.
There were no differences in demographic data, educational or occupational status of patients in either group (Tables 1 and 2). Although there were no significant differences in the strength of uterine contractions within the groups, there was a significant decrease in uterine contractions in Group 1 at 25 min (P < 0.01) (Table 3). There was no difference in the duration of the first stage of labour between the groups (Table 4); however, the second stage of labour was significantly shorter in Group 2 compared with Group 1 (P < 0.01). There were no significant differences in the type of delivery between the groups. In Group 1, 17 patients (85%) delivered spontaneously; three patients (15%) needed instrumental delivery (two by vacuum, one by forceps). In Group 2, 19 patients (95%) delivered spontaneously - one (5%) required instrumental delivery (by vacuum). Caesarean section was not needed in any patient in any group. The quantity of infused drugs and the duration of their infusion did not differ between the groups (Table 4). SPO2 did not decrease below 96% in any patient in either group.
The intra- and intergroup differences in SAP and DAP and in maternal HR of patients were not significant (P > 0.05) (Fig. 1); nor were the changes in FHR significant (P > 0.05) (Fig. 2). Fetal bradycardia (≤ 100 beats min−1), lasting <60 s, was observed during the first 30 min in three patients (15%) in Group 1, but resolved spontaneously without requiring intervention. Apgar scores were not less than 7 in any newborn, and there was no difference in scores between groups (Table 5). Umbilical blood gas analyses were all normal, and there were no differences between groups.
A similar median level of sensory loss to pinprick in the mid-clavicular line was observed in all patients in both groups (T10). A non-significant motor block (Bromage 1) was observed in two patients (10%) in Group 1, but not in Group 2. VAS scores were not different between the two groups. In both groups, a significant decrease was observed within the first 5 min (P < 0.05), but after 20 min pain was not observed in any patient (Table 6). After delivery, there was no difference in the quality of analgesia between two groups.
The most commonly seen side-effect was slight itching, which was observed in two (5%) and five (25%) patients in Groups 1 and 2, respectively. Nausea was observed in only one patient (5%) in each group; no patient requested treatment.
In recent years there has been a steady decline in the concentrations of local anaesthetics used for epidural analgesia in labour. Our results show that ropivacaine 0.05% + fentanyl 1.5 μg mL−1, or bupivacaine 0.05% + fentanyl 1.5 μg mL−1, given via a PCEA device, produces effective pain relief in labour.
Many studies have compared the local anaesthetic properties of epidurally administered ropivacaine and bupivacaine for analgesia in labour. Some investigators have compared ropivacaine 0.25% with bupivacaine 0.25% and found no significant differences in the quality of analgesia, sensory block or motor block [5,6]. Owen and colleagues  compared ropivacaine 0.125% + fentanyl 2 μg mL−1 with bupivacaine 0.125% + fentanyl 2 μg mL−1 using PCEA. The doses of local anaesthetics and opioids used in the present study have been used before with bupivacaine , but not with ropivacaine.
Capogna  reported that transient changes in FHR might occasionally follow the use of any technique, even if minimum effective doses are used in epidural analgesia for labour. Indeed, a transient decrease in FHR was observed in Group 1. Fischer and colleagues  reported that the incidence of motor block was lower in a ropivacaine group than in a bupivacaine group. However, Owen and colleagues  did not detect any significant difference in the degree of motor block, using ropivacaine 0.125% alone or bupivacaine 0.125% without opioid, via a PCEA route. In our study, a Bromage 1 motor block was only seen in the bupivacaine group. Although our results appear similar to those of Fischer and colleagues, we found no difference between the groups. This lower incidence may be due to lower doses of the local anaesthetic and opioid that we used in our study.
Hoult and colleagues  found that in the second phase of labour, the incidence of Caesarean section was increased when epidural analgesia was used. However, others have claimed that the continuation of analgesia during the entire period of the second stage of labour does not increase in the incidence of instrumental delivery, nor does it lengthen the second stage . Fischer and colleagues  reported that the duration of the second stage of labour was shorter in the ropivacaine group. In our study, analgesia was continued in both groups for the whole period of the second stage, and this stage was shorter in the topivacaine group. The difference observed in the duration of the second stage may be related to specific properties of ropivacaine.
Thornton and Capogna  claimed that continuous low-dose infusion of opioid and local anaesthetic could reduce the need for instrumental delivery by promoting more mobility in labour and by enabling females to push well. Smedvig and colleagues , reported that epidural use of ropivacaine 1 mg mL−1 + fentanyl 2 μg mL−1 provided effective analgesia with a high spontaneous rate of delivery (71%) and decreased the incidences of instrumental delivery (14%) and Caesarean delivery (2%). Fischer and colleagues  reported the spontaneous vaginal delivery rate as 78%, instrumental delivery as 14% and the incidence of Caesarean delivery as 2% in a ropivacaine group. In another study, it was shown that the rate of instrumental delivery did not increase, and the second stage of labour was not prolonged with an infusion of bupivacaine 0.125-0.0625% + fentanyl 0.0002% . The higher spontaneous delivery rate (85 and 95% in Groups 1 and 2, respectively) in our study may be related to the lower doses of drugs used.
Mulroy  stated that the lowest dose requirement appeared to be associated with the administration of PCEA, especially if a constant background infusion was used. In this study, the dose requirement was very low, in accord with Mulroy's opinion, and the total doses of bupivacaine and ropivacaine infused were very much lower than the toxic doses of either drug.
There is an important correlation between the pH of umbilical arterial blood and the second stage of labour . Segmental epidural analgesia during labour decreases metabolic acidosis in the fetus resulting in Apgar scores in the newborn being higher [17,18]. In this study, Apgar scores of all newborns were ≥7; umbilical arterial blood-gas status did not indicate any acidosis.
Cohen and colleagues  reported the incidence of itching in patients with epidural analgesia with bupivacaine/fentanyl to be as high as 30%. Kostamovaara and colleagues  reported no difference between epidural fentanyl and fentanyl-ropivacaine groups; the adverse effects were similar, consisting mostly of slight pruritus. Slight itching was the most common side-effect in both groups in our study and may be related to the administration of the fentanyl, since the incidence was not statistically different in either group.
Bupivacaine 0.05% or ropivacaine 0.05% combined with fentanyl 1.5 μg mL−1 given via a PCEA device is a suitable choice for analgesia in labour. Both drugs produce similar effects, effective analgesia, together with high patient satisfaction and a high spontaneous delivery rate.
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