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A randomised comparison of variable-frequency automated mandatory boluses with a basal infusion for patient-controlled epidural analgesia during labour and delivery
Article first published online: 20 DEC 2012
Anaesthesia © 2012 The Association of Anaesthetists of Great Britain and Ireland
Volume 68, Issue 3, pages 267–275, March 2013
How to Cite
Sia, A. T., Leo, S. and Ocampo, C. E. (2013), A randomised comparison of variable-frequency automated mandatory boluses with a basal infusion for patient-controlled epidural analgesia during labour and delivery. Anaesthesia, 68: 267–275. doi: 10.1111/anae.12093
- Issue published online: 5 FEB 2013
- Article first published online: 20 DEC 2012
- Manuscript Accepted: 20 MAY 2012
This trial was conducted to compare the analgesic efficacy of administering variable-frequency automated boluses at a rate proportional to the patient's needs with fixed continuous basal infusion in patient-controlled epidural analgesia (PCEA) during labour and delivery. We recruited a total of 102 parturients in labour who were randomly assigned to receive either a novel PCEA with automated mandatory boluses of 5 ml administered once, twice, three or four times per hour depending on the history of the parturient's analgesic demands over the past hour (Automated bolus group), or a conventional PCEA with a basal infusion of 5 ml.h−1 (Infusion group). The incidence of breakthrough pain requiring supplementation by an anaesthetist was significantly lower in the Automated bolus group, three out of 51 (5.9%) compared with the Infusion group, 12 out of 51 (23.5%, p = 0.023). The time-weighted mean (SD) hourly consumption of ropivacaine was similar in both groups, 10.0 (3.0) mg in the Automated bolus group vs 11.1 (3.2) mg in the Infusion group (p = 0.06). Parturients from the Automated bolus group reported higher satisfaction scores compared with those in the Infusion group, 96.5 (5.0) vs 89.2 (9.4), respectively (p < 0.001). There was no difference in the incidence of maternal side-effects and obstetric and neonatal outcomes.
Patient-controlled epidural analgesia (PCEA) is a mode of labour epidural drug delivery that confers greater autonomy and flexibility by enabling the parturient to self-administer boluses of epidural solution as necessary. Several studies have affirmed the advantages of PCEA over a conventional epidural infusion and it has become established as a safe and efficacious mode of labour epidural drug delivery [1-3]. However, despite extensive research over the last decade, the optimal PCEA program settings have not been elucidated. In particular, there have been conflicting results in the literature with regard to the merit of administering a basal infusion as well as an optimal infusion rate [4-8]. At our institution we postulated that, although a basal infusion may not be beneficial in early labour, its role may become increasingly important as pain intensifies with the progress of labour. This led to the creation of a computer-integrated PCEA program, which could analyse the parturient's demand boluses over the last hour and adjust its infusion rate proportionally, essentially operating on an auto regulatory feedback loop. Results from initial trials utilising the computer-integrated PCEA program were encouraging, demonstrating a reduced incidence of breakthrough pain and greater maternal satisfaction with no increase in total local anaesthetic consumption [9-11].
Studies in the past have suggested that maintaining labour analgesia using regular intermittent epidural boluses instead of a slow continuous infusion can be more efficacious [12-14]. This may be attributed to a more extensive spread of epidural solution when delivered as a bolus rather than as a steady infusion [15, 16]. When incorporated into a PCEA regimen and used in place of a continuous basal infusion, automated intermittent boluses have been shown to reduce overall local anaesthetic consumption without compromising analgesic efficacy [17, 18].
The purpose of our current trial was to combine the above concepts by administering variable-frequency automated boluses at a rate proportional to the patient's needs, in place of a fixed continuous basal infusion in a PCEA regimen. We designed a complex software program that enables an ordinary syringe pump to function as a PCEA pump with the ability to deliver variable-frequency automated mandatory boluses in addition to patient-driven PCEA boluses. This was compared with a conventional PCEA using a basal infusion, which is the standard regimen used at our institution. Our primary outcome measure was the incidence of breakthrough pain requiring supplementation by an anaesthetist.
This study was conducted with the approval of the Hospital Ethics Committee and written informed consent was obtained from every parturient who participated in the study. We recruited 102 healthy (ASA physical status 1) nulliparous parturients at term (> 36 weeks, gestation) with a singleton fetus, who were in early labour (cervical dilation < 5 cm) and who had requested labour epidural analgesia.
Parturients with multiple pregnancies, non-cephalic fetal presentation and obstetric complications (e.g. pre-eclampsia and premature rupture of amniotic membranes) were not studied. Parturients who had contraindications to neuraxial blockade or who had received parenteral opioids within the last 2 h were also not studied.
After establishing intravenous access, the cuff of a non-invasive blood pressure monitor (Dinamap, Critikon, FL, USA) was applied over the parturient's right brachial artery. Baseline systolic blood pressure and heart rate were measured in the supine position with left uterine displacement. Each parturient was pre-loaded with 500 ml intravenous Ringer's lactate solution. A baseline visual analogue pain score (VAS) on a 0–10 cm scale was obtained from the parturient during a uterine contraction, and only those who had a VAS > 3 cm were entered into the study. Pre-block data such as the cervical dilation before neuraxial blockade, use of cervical prostaglandin E2 for induction of labour, artificial rupture of membranes and administration of oxytocin infusion for labour augmentation were recorded.
Combined spinal–epidural (CSE) analgesia was explained to each parturient and informed consent obtained as per the institution protocol. All neuraxial blocks were performed by a single operator at the L3–4 interspace using the needle-through-needle technique with the patient sitting. The epidural space was located with an 18-G Tuohy needle (Espocan; B. Braun, Melsungen, Germany) using loss of resistance to < 2 ml saline. A 27-G pencil-point needle was then used to puncture the dura mater and free flow of cerebrospinal fluid (CSF) was confirmed before a standard intrathecal dose of ropivacaine 2 mg (Naropin; Astra Zeneca, Södertälje, Sweden) and fentanyl 15 μg (David Bull Laboratories, Melbourne, Australia) was injected over 15 s with the needle orifice facing cephalad. A multi-orifice catheter (Perifix®; B. Braun) was inserted into the epidural space to a distance of 4 cm. A test dose of 3 ml lidocaine 1.5% (Xylocaine; Astra Zeneca) was administered through the catheter following negative aspiration for blood and CSF. The patient was then placed supine with left uterine displacement and the post-block profile was recorded. If a profound motor block (defined as inability to flex either knee) or significant hypotension (reduction in systolic blood pressure > 30%) developed within the next 15 min, the patient was withdrawn from the study in case this was due to intrathecal catheter misplacement. Patients with a recognised accidental dural puncture, intravascular catheter placement and those in whom there was a failed spinal (defined as failure to obtain CSF backflow following two dural punctures with the spinal needle) were also not studied and were managed according to departmental protocols.
The parturients were randomly allocated into two groups using sealed opaque envelopes and computer-generated random number tables by a different investigator, who then programmed the epidural drug delivery system according to the group assignment. The parturients were subsequently monitored by a second anaesthetist who was not involved in performing the block. Neither the parturient nor the anaesthetist who recorded the post-block data was aware of the group assignment.
The parturients received 0.1% ropivacaine + fentanyl 2 μg.ml−1 via one of two regimens for maintenance of labour epidural analgesia:
- Automated bolus group: a PCEA algorithm as illustrated in Fig. 1 was used, initiated immediately after the completion of CSE. The pump was designed to administer automated boluses of 5 ml in addition to the patient-controlled boluses. The frequency of such automated boluses was dependent on the history of the patient's analgesic requirement over the past hour. The first automated bolus was programmed to be delivered 60 min from time 0 and every hour thereafter if no PCEA patient-bolus was made (one automated bolus of 5 ml every hour). At the first activation of a PCEA patient-bolus, the timer would be reset with the subsequent automated bolus delivered 30 min following the PCEA patient-bolus, and every hour thereafter if no further PCEA patient-bolus was made (one automated bolus of 5 ml every hour). If there was a second PCEA patient-bolus in that same hour after the initial bolus, the time interval between two automated boluses would be shortened to 30 min (two automated boluses of 5 ml every hour). If there was a third PCEA patient-bolus within that hour, the automated bolus would be delivered at 20-min intervals (three automated boluses of 5 ml every hour). A fourth PCEA patient-bolus within the same hour would further shorten the time interval between two automated boluses to 15 min (four automated boluses of 5 ml every hour). On the other hand, if there were no patient-bolus for 60 min, the frequency of automated boluses would step down in the reverse fashion. The lockout period for both PCEA and automated boluses was 10 min. If a PCEA demand was made within 10 min of an automated bolus, no patient-bolus would be given and this would be recorded as an unsuccessful PCEA attempt. The PCEA demand bolus was set at 5 ml with a maximum hourly limit of 20 ml.h−1 (inclusive of automated boluses).
- Infusion group: PCEA with basal infusion 5 ml.h−1 initiated immediately following intrathecal drug administration (noted as time 0). The PCEA demand bolus was set at 5 ml, lockout interval at 10 min and maximum dose at 20 ml.h−1 (inclusive of background infusion).
Our institution collaborated with computer engineers to create a software program that allowed an ordinary syringe driver to function as a PCEA with the ability to deliver background mandatory boluses in addition to patient-demand boluses. We developed an epidural drug delivery system utilising a Hewlett Packard Compaq 2710p Tablet PC operating on Microsoft Windows XP Tablet PC Edition 2005 (Microsoft, Redmond, WA, USA) connected to a modified Perfusor® Compact S infusion pump (B. Braun) (Fig. 2). Program source codes for both the automated bolus and basal infusion PCEA regimens were loaded into the Tablet PC. The two-way communication between the pump and the HP Tablet PC was accomplished by connecting the pump serial ports to the USB port on the Tablet PC. The 5-ml automated boluses as well as PCEA demand boluses were time-cycled, based on an infusion rate of 100 ml.h−1 and required 3 min to complete. Both programs underwent rigorous in vitro testing at our institution's Biomedical Engineering Unit and by all investigators independently before being applied to patients in a clinical setting.
Once the parturient reported a VAS < 3 cm 15 min after CSE, she was given the hand set and instructed to self-administer a PCEA bolus by pressing the button on the device when she experienced a recurrence of pain. She was instructed to activate the PCEA bolus if the pain was mild and before it increased in severity. She was informed about the purpose of a lockout period and maximum hourly dose limit. Parturients who did not obtain satisfactory pain relief (defined as VAS < 3 cm) 15 min after CSE were deemed to have an ineffective spinal. The epidural catheter would then be used to administer rescue analgesia and the patient removed from the study.
Post-block parameters were monitored by a separate blinded anaesthetist after the procedure. Maternal systolic blood pressure and heart rate were monitored every 5 min for the first 30 min and subsequently at 2-h intervals until delivery. Maternal VAS was monitored at 15 and 30 min from time 0 and subsequently at 2-h intervals until delivery. Maternal sensory block height (loss of cold sensation to ice tested at the mid-clavicular line bilaterally) was monitored at 15 and 30 min from time 0 and subsequently at 2-h intervals until delivery.
The degree of maternal lower limb motor block was monitored at 15 and 30 min from time 0 and subsequently at 2-h intervals until delivery, based on the modified Bromage scale (0 = no motor block, 1 = unable to flex either hip, but able to move knee and ankle joints, 2 = unable to flex hip and knee joint of either limb, but able to move ankle joints, 3 = unable to move hip, knee or ankle joint of either limb). The occurrence of post-block maternal side-effects such as shivering, nausea, vomiting, pruritus, maternal pyrexia, significant maternal hypotension (systolic BP < 90 mmHg or > 20% decrease from baseline) and fetal bradycardia requiring review by an obstetrician were documented. Treatment for maternal hypotension and fetal bradycardia was administered as per institution protocol, i.e. intravenous adrenaline in 5-mg aliquots if maternal hypotension was present, and intravenous terbutaline 0.25 mg if uterine hyperstimulation was diagnosed. Continuous fetal heart rate monitoring was maintained throughout the labour.
The parturient was instructed to inform the attending anaesthetist if she experienced inadequate pain relief (VAS ≥ 3 cm) during PCEA. In this case, additional pain relief was administered by the anaesthetist via the epidural catheter and an episode of breakthrough pain was recorded. According to departmental guidelines, the attending anaesthetist would administer epidural 0.2% ropivacaine in 5-ml aliquots every 10 min (up to a maximum of 20 ml) until VAS decreased to < 3 cm. Fentanyl 50 μg was added if the VAS remained ≥ 3 cm after 10 ml epidural 0.2% ropivacaine had been given. The pumps were paused for the duration of time taken to administer each clinician bolus, and resumed immediately afterwards. Such anaesthetist-administered manual boluses did not affect the PCEA pump settings in any way. The episode of breakthrough pain was concluded once the parturient reported a VAS < 3 cm. The following data were recorded at each episode of breakthrough pain: time of occurrence; pain score; cervical dilation; use of oxytocin; and total dose of epidural medication needed to abolish the pain. If the epidural top-up failed to achieve adequate analgesia (defined as VAS < 3 cm), the catheter was deemed ineffective and the parturient would be removed from the study.
Obstetric and neonatal outcomes such as the mode of delivery, indication for instrumental or caesarean delivery, duration of second stage of labour and neonatal Apgar scores at 1 and 5 min were noted. The parturient was interviewed within 24 h of delivery by a separate anaesthetist not involved in the study for an overall assessment of her satisfaction with labour analgesia (graded on a verbal scale from 0 = very dissatisfied to 100 = extremely satisfied).
A sample size of 49 patients in each group was required to detect an 80% reduction in the incidence of breakthrough pain requiring physician top-up for patients in the Automated bolus group compared with those in the Infusion group (α = 0.05, β = 0.2). A reduction in the incidence of breakthrough pain from a baseline of 25% at our institution to 5% was deemed clinically significant as this could potentially improve patient satisfaction and reduce clinician workload. All data and statistical analyses were managed with SPSS version 15 (SPSS Inc., Chicago, IL, USA). Student's t-test was used for the analysis of continuous data, which was normally distributed and the Mann–Whitney test employed for non-continuous data. For categorical data and proportions, the chi-squared test with Yates correction (where appropriate) was applied. For analysis of serial measurements such as pain scores and sensory levels, the mixed model repeated measurement analysis technique with a compound symmetry covariance structure for the data points was employed to adjust for missing data at time intervals after the parturients had delivered and the epidural infusion had been stopped.
All 102 recruited parturients completed the study (Fig. 3). Baseline demographic and pre-block obstetric data were similar for parturients in both groups (Table 1). None of the patients had a failed spinal or an ineffective epidural catheter. No parturients had intravascular misplacement of the epidural catheter or accidental dural puncture.
|Automated bolus (n = 51)||Infusion (n = 51)|
|BMI; kg.m−2||27.3 (3.9)||28.2 (4.9)|
|Cervical dilation pre-block; cm||3.2 (0.7)||3.2 (0.9)|
|Maternal systolic BP; mmHg||113.8 (10.6)||115.9 (11.9)|
|Maternal diastolic BP; mmHg||67.8 (9.5)||68.4 (9.3)|
|Maternal heart rate; beats.min−1||76.0 (10.1)||79.2 (13.2)|
|Fetal heart rate; beats; min−1||139.4 (10.1)||141.2 (11.1)|
|Pain VAS; cm||8.0 (1.7)||7.8 (1.5)|
|Using Entonox||28 (55.0%)||24 (47.1%)|
|Previous use of pethidine; > 2 h||4 (7.8%)||6 (11.8%)|
|Oxytocin infusion||18 (35.3%)||14 (27.5%)|
|Previous use of prostaglandin E2||23 (45.1%)||20 (39.2%)|
|Artificial rupture of membranes||33 (64.7%)||28 (54.9%)|
The incidence of the primary study outcome, breakthrough pain requiring epidural top-up by an attending anaesthetist, was significantly lower in the Automated bolus group with three patients (5.9%) compared with the Infusion group with 12 patients (23.5%, p = 0.023). There were two patients in the Infusion group who experienced two episodes of breakthrough pain, of whom one delivered vaginally and the other underwent caesarean delivery for poor progress of labour. The patient profiles at the time of breakthrough pain are shown in Table 2.
|Automated bolus (n = 3)||Infusion (n = 12)||p valuea|
|Time to 1st breakthrough pain; min||205 (139–555 [139–555])||286.5 (164–391 [145–630])||0.99|
|Volume of epidural solution infused at 1st breakthrough pain; ml||25 (15–65 [15–65])||47.5 (34–65 [20–100])||0.25|
|Cervical dilation at 1st breakthough pain; cm||6 (3–7 [3–7])||6.5 (5–8 [3–10])||0.42|
|VAS at 1st breakthrough pain; cm||6 (6–6 [6–6])||7.5 (6–9 [5–10])||0.12|
|Oytocin infusion at 1st breakthrough pain; ml.h−1||18 (12–42 [12–42])||12 (0–27 [0–72])||0.30|
|Sensory level at 1st breakthrough pain||T8 (T6–T10 [T6–T10])||T8 (T7–T10 [T6–T10])||0.89|
|Bromage score at 1st breakthrough pain||0 [0–0]||0 [0–0]||1.0|
The improved analgesic efficacy in the Automated bolus group was achieved without any significant difference in the amount of local anaesthetic consumed. The time-weighted mean hourly consumption of ropivacaine, inclusive of clinician-administered supplemental boluses, was similar in both groups, 10.0 (3.0) mg in the Automated bolus group vs 11.1 (3.2) mg in the Infusion group (p = 0.06). There was no difference in the total amount of ropivacaine used, 62.0 (32.6) mg in the Automated bolus group vs 74.2 (34.0) mg in the Infusion group (p = 0.07). The time to first patient-demand bolus following CSE was similar, 115.8 (65.2) min in the Automated bolus group vs 112.1 (70.4) min in the Infusion group (p = 0.78).
Mixed model repeated measurement analysis did not detect any difference in post-block serial pain scores (p = 0.146 for the interactive term of group and VAS score) or sensory levels (p = 0.619 for the interactive term of group and hourly block height), although this could be due to the study's not being adequately powered for these comparisons. Maternal side-effects experienced were also similar in both groups (Table 3). One parturient from the Infusion group had hypotension that resolved following administration of intravenous ephedrine 5 mg. Two patients in the Automated bolus group had fetal bradycardia, one resolving spontaneously and the other requiring intravenous terbutaline 0.5 mg. Two patients in the Infusion group had fetal bradycardia requiring administration of intravenous terbutaline 0.25 mg. None of these four parturients required an emergency caesarean section.
|Automated bolus (n = 51)||Infusion (n = 51)||p value|
|Shivering||23 (45.1%)||26 (51.0%)||0.69|
|Pruritus||29 (56.9%)||27 (52.9%)||0.84|
|Nausea||1 (2.0%)||1 (2.0%)||1.0|
|Vomiting||1 (2.0%)||2 (3.9%)||1.0|
|Maternal pyrexia||3 (5.9%)||4 (7.8%)||1.0|
|Maternal hypotension||0||1 (2.0%)||1.0|
|Fetal bradycardia||2 (3.9%)||2 (3.9%)||1.0|
Parturients in both groups had a similar mean duration of labour. There was no difference in the duration of the second stage of labour amongst parturients who delivered vaginally, either with or without instrumental assistance. This was in spite of the significantly higher mean rate of machine-delivered epidural medication in the Automated bolus group, 10.9 (4.5) ml.h−1 compared with the mean background infusion rate of 4.8 (1.0) ml.h−1 in the Infusion group at full cervical dilation (p < 0.001). Two parturients in the Infusion group had their epidural infusion stopped by the obstetrician during the second stage of labour and their data were analysed up to the point of cessation of analgesia. Neonatal outcomes such as birth weight and Apgar scores were similar (Table 4).
|Automated bolus (n = 51)||Infusion (n = 51)||p value|
|Duration of labour; min||389.4 (202.9)||414.2 (181.3)||0.52|
|Duration of 2nd stage; min||69.8 (48.9)||84.9 (57.9)||0.22|
|Rate of machine-delivered epidural medication during 2nd stage of labour; ml.h−1||10.9 (4.5)||4.8 (1.0)||< 0.001|
|Mode of delivery|
|Normal||33 (64.7%)||32 (62.7%)||0.65|
|Instrumental||5 (9.8%)||8 (15.7%)|
|Caesarean||13 (25.5%)||11 (21.6%)|
|Neonatal birthweight; g||3244.4 (392.5)||3083.5 (502.9)||0.08|
|Neonatal Apgar score at 5 min||9 (9–9 [7–9])||9 (9–9 [9–9])||1.00|
|Satisfaction score||96.5 (5.0)||89.2 (9.4)||< 0.001|
When asked to rate their overall labour analgesia experience, parturients in the Automated bolus group reported higher satisfaction scores compared with those in the Infusion group, 96.5 (5.0) vs 89.2 (9.4) respectively (p < 0.001).
In this study, we demonstrated that using variable-frequency automated intermittent boluses in place of a continuous basal infusion in PCEA for labour analgesia resulted in a reduced incidence of breakthrough pain requiring supplementation by the anaesthetist and greater overall maternal satisfaction, without any increase in local anaesthetic consumption.
The role of a basal infusion in PCEA has long been a topic of debate. On one hand, studies have shown that PCEA with a basal infusion can reduce the incidence of breakthrough pain and reduce pain scores with no increase in local anaesthetic consumption compared with a demand-only PCEA [4-6]. On the other hand, some investigators found that using a basal infusion in a PCEA regimen may increase local anaesthetic consumption without improving analgesic efficacy [7, 8]. However, a constant background infusion may not be ideal as it cannot be responsive to the dynamic and progressive nature of labour pain. This spurred us to create a novel computer-integrated PCEA program that analyses the number of patient-demand boluses over the past hour and adjusts its basal infusion rate according to the mother's analgesic requirements . The basal infusion is initiated by the parturient after her first demand bolus. Earlier studies that compared this interactive computer-integrated PCEA program to conventional PCEA regimens demonstrated similar analgesic efficacy and greater maternal satisfaction with the computer-integrated PCEA, without increasing the total amount of local anaesthetic consumed [10, 11]. However, these studies were not powered to detect a difference in the incidence of breakthrough pain requiring supplementation by an anaesthetist.
Previous experiments have also suggested that administering epidural drugs in the form of regular intermittent boluses instead of a slow continuous infusion may be more efficacious. In a study on human cadavers, Hogan  found that intermittent boluses that were delivered at higher infusion pressures could result in a more uniform spread of medication within the epidural space compared with a continuous infusion delivered at lower pressures. In a laboratory experiment using multi-orifice epidural catheters, Kaynar et al.  demonstrated that administering a slow continuous infusion at low injection pressures resulted in flow of solution primarily through the proximal hole with none flowing through the distal hole. In contrast, when the solution was delivered by a bolus at higher injection pressures, there was flow through all the catheter ports. This could translate into improved quality of block in a clinical setting where multi-orifice catheters are used. Experimental evidence has been applied successfully in clinical practice through several studies that have demonstrated that intermittent epidural boluses given in place of a continuous infusion can decrease the incidence of breakthrough pain and increase maternal satisfaction [12-14]. The automated mandatory bolus concept has also been incorporated successfully into PCEA regimens, conferring similar analgesic efficacy with lower local anaesthetic consumption and greater maternal satisfaction when used in place of a continuous basal infusion [17, 18].
In this study, we have successfully incorporated variable-frequency automated boluses in place of a conventional basal infusion into our PCEA regimen. Varying the frequency of automated mandatory boluses in tandem with the frequency of patient-demand boluses improves the analgesic efficacy of a PCEA regimen, as shown by the fourfold reduction in incidence of breakthrough pain when the Automated bolus regimen is used instead of a conventional PCEA with basal infusion. The lack of difference in local anaesthetic consumption between the two groups is likely to be due to the auto regulatory nature of the Automated bolus regimen, which minimises drug usage in early labour when pain is less intense and allows greater drug consumption to match the escalating pain of advanced labour. Indeed, we found a significantly higher rate of machine-delivered background epidural boluses in the Automated bolus group compared with the mean basal infusion rate in the Infusion group at full cervical dilatation. We postulate that this may have alleviated perineal pain more effectively and thus contributed to the observed increase in maternal satisfaction in the Automated bolus group. We did not detect any adverse effects resulting from the higher consumption of local anaesthetic during advanced labour, as shown by the similar duration of second stage, mode of delivery and neonatal outcomes in both groups, although this could be due to the study's not being adequately powered for such comparisons. Also, despite patient profiles at the first episode of breakthrough pain being largely similar in both groups, the number of patients was too small to draw any meaningful conclusion.
In conclusion, variable-frequency automated mandatory boluses are superior to a constant background infusion in PCEA for the maintenance of labour epidural analgesia. A reduction in the need for anaesthetist-administered supplementation of the epidural block not only increases maternal satisfaction but may also be important in reducing workload at a busy tertiary obstetric unit like ours. Harnessing the power of technological advancement to create newer and more interactive PCEA algorithms may bring us a step closer to achieving seamless labour analgesia for every parturient in the future.
We would like to acknowledge our research assistant Miss Agnes Teo and our systems analyst Mr Philip Cheong for their contributions to this project.
No external funding and no competing interests declared.
- 6Comparison of continuous background infusion plus demand dose and demand-only parturient-controlled epidural analgesia (PCEA) using ropivacaine combined with sufentanil for labor and delivery. International Journal of Obstetric Anesthesia 2005; 14: 114–20., , , et al.
- 12Automated intermittent epidural boluses improve analgesia induced by intrathecal fentanyl during labour. Canadian Journal of Anesthesia 2004; 51: 581–5., .
- 15Distribution of solution in the epidural space: examination by cryomicrotome section. Regional Anesthesia and Pain Medicine 2002; 27: 150–6..