Combined spinal-epidural labor analgesia

Combined spinal-epidural (CSE) labor analgesia is a new neuraxial labor analgesic technique. An intrathecal injection of an opioid alone, or in combination with a local anesthetic, initiates analgesia. An epidural catheter can then be used to maintain pain relief for the duration of labor. The CSE technique combines the advantages of spinal analgesia (low drug doses, rapid onset, immediate sacral block) and epidural analgesia (titratable, able to maintain analgesia indefinitely, ability to convert to epidural anesthesia). Side effects are acceptable with attention to patient selection and technique. The initiation of CSE analgesia with either fentanyl (25 μg) or sufentanil (5.0–7.5 μg) is appropriate for early labor, or in patients for whom an acute decrease in preload is not desirable. Although an equipotent dose of sufentanil has a longer duration of analgesia than fentanyl, both drugs provide excellent analgesia and prolonged duration is of minimal clinical significance when the intrathecal dose is followed by maintenance epidural analgesia. The addition of a local anesthetic to the opioid is required to provide satisfactory analgesia once fetal descent begins. The addition of local anesthetic (usually bupivacaine 1.25–2.5 mg) allows the dose of opioid to be decreased. Markedly lower opioid doses (fentanyl 5 μg or sufentanil 1.0–2.5 μg) can then provide effective analgesia with fewer systemic side effects. Several additives have been shown to prolong the duration of analgesia of opioids and opioids plus bupivacaine, but the short increase in duration of analgesia may not be worth the increased difficulty of combining multiple drugs.     

Horner's syndrome following very low concentration bupivacaine infusion for labor epidural analgesia

Horner's syndrome is a complication of epidural analgesia and anesthesia, encountered more commonly in pregnant women than in other patients. Previous reports described the appearance of Horner's syndrome following epidural injection of concentrated local anesthetic solutions. We report unilateral Horner's syndrome occurring in the setting of lumbar epidural analgesia for labor with a very low local anesthetic concentration (bupivacaine 0.04%) in an epidural infusion. We discuss the possible factors that could have contributed to this occurrence despite the extremely dilute concentration of local anesthetic used for analgesia.     

Combined subarachnoid-epidural technique for obstetric analgesia

Combined spinal-epidural blockade for labor pain has enjoyed increasing popularity in obstetric anesthesia. The usual procedure is to use a single space and a single needle for dural puncture, inserting a spinal needle through an epidural needle followed by insertion of a catheter. A small dose of one or several substances (usually a lipophilic opioid and a local anesthetic) is first injected in the intrathecal space to provide rapid, effective analgesia with minimal muscle blockade. The epidural catheter is used if labor lasts longer than the spinal block, if the spinal block is insufficient, or in case of cesarean section. Combined spinal-epidural blockade is a safe, valid alternative to conventional epidural analgesia and has become the main technique for providing obstetric analgesia in many hospitals. The most widely-recognized advantage of the technique is high maternal satisfaction with rapid and effective analgesia. Mobility of the lower extremities is preserved and the mother is often able to walk. Because opioids are injected into the intrathecal space and because the technique is more invasive than standard epidural analgesia, the potential risk to mother and fetus increases.     

Epidural catheter function during labor predicts anesthetic efficacy for subsequent cesarean delivery

One of the benefits of labor epidural analgesia is that the catheter can be used to initiate a surgical block should the need for cesarean delivery arise. However, sometimes it is not possible to obtain adequate surgical anesthesia via a previously placed labor epidural catheter and it is unknown what factors are associated with this failure. We retrospectively investigated the incidence of failure to convert a labor epidural to a successful surgical block in our institution over a period of one year and determined the factors associated with this failure. There were 246 cases in which a patient had an epidural catheter placed for labor and then had a cesarean delivery. Of these 246 cases, 220 developed surgical anesthesia using the catheter. In six cases the anesthesiologist did not attempt to use the epidural catheter for the cesarean delivery. In 20 cases (classified as failed blocks), the catheter was injected, but another method of anesthesia was then used. Factors associated with failure of the epidural block were an increased requirement for supplemental local anesthetic boluses during labor in order to provide adequate analgesia and that the attending anesthesiologist for the cesarean delivery was not a specialist in obstetric anesthesia. Most epidural catheters placed for labor can be used to induce a surgical block. When significantly more local anesthetic than usual is required to maintain analgesia during labor, however, the epidural catheter may not be functioning properly and consideration should be given to replacing it.     

Continuous epidural infusion of 0.05% bupivacaine plus hydromorphone for labor analgesia: an observational assessment in 1830 parturients

IMPLICATIONS: We evaluated a continuous epidural infusion containing bupivacaine 0.05% plus the opioid hydromorphone in 1830 women requesting pain relief during labor and delivery. The infusion provided effective analgesia with minimal adverse events for patients differing in parity and at varying stages of labor. Pain relief was maintained in most patients without the need for epidural reinforcement with more concentrated doses of local anesthetic.     

Effect of standard diluted epinephrine infusion on epidural anesthesia in labor

BACKGROUND AND OBJECTIVES: Epinephrine is used with local anesthetics to prolong the duration of epidural analgesia and decrease the peak plasma concentrations of local anesthetics. However, the duration of labor may be prolonged because epinephrine reduces uterine activity. We designed a prospective, randomized, and doubleblind study to examine the effects of epinephrine infusion on the quality of analgesia and plasma concentration of local anesthetic, as well as the effect on the uteroplacental circulation, duration of the first or second stage of labor, and fetal outcome. METHODS: Twenty-four parturients received continuous epidural bupivacaine 0.125% (8 mL/h) combined either with epinephrine (40 microg/h) (n = 12) or without epinephrine (n = 12) for analgesia during labor. If patients requested additional analgesia, a bolus of 1% or 1.5% lidocaine (6 to 10 mL) was given. RESULTS: Only the plain bupivacaine group required additional lidocaine. However, epinephrine infusion prolonged the median (range) duration of the second stages of labor: 69 (21 to 231) minutes with epinephrine group versus 31 (8 to 99) minutes without epinephrine group (P < .05), and decreased pH in umbilical artery at the time of delivery. Epinephrine infusion did not change the uterine and umbilical blood flow, which were determined as the resistance indices. Changes in the fetal heart rate and Apgar score were also comparable. Epinephrine significantly reduced the umbilical venous to maternal arterial bupivacaine concentration (P < .05). CONCLUSIONS: A standard diluted epinephrine infusion (40 microg/h) into epidural space decreased anesthetic requirements. The possibility of the prolonged duration of labor remains a problem.     

Combined spinal-epidural analgesia for labor

Combined spinal-epidural analgesia is a technique that provides rapid-onset, profound epidural analgesia for laboring parturients at almost any stage of labor. The most commonly used technique is a needle-through-needle technique in which the epidural space is identified with an epidural needle, and then a long spinal needle is inserted through the epidural needle and into the cerebrospinal fluid. Intrathecal fentanyl, 15 to 25 μg ± 1 to 2.5 mg of bupivacaine, or 2.5 to 5 μg of sufentanil ± 1 to 2.5 mg of bupivacaine are injected to produce analgesia. The epidural needle is removed and an epidural catheter inserted. Analgesia is maintained by low-dose, patient-controlled epidural analgesia; continuous infusion epidural analgesia; or intermittent top-ups. Pruritus is a very common side effect. Respiratory depression is rare but of great concern. Current literature favors low-dose epidural analgesia in labor as leading to the best patient and obstetric outcomes. Both low-dose conventional epidural analgesia and combined spinal-epidural analgesia produce similar outcomes. The main advantage of combined spinal-epidural analgesia is its predictable profound analgesia in parturients during late labor or when labor is progressing rapidly. Copyright © 2001 by W.B. Saunders Company     

Combined spinal-epidural versus epidural labor analgesia

BACKGROUND: Despite the growing popularity of combined spinal-epidural analgesia in laboring women, the exact role of intrathecal opioids and the needle-through-needle technique remains to be determined. The authors hypothesized that anesthetic technique would have little effect on obstetric outcome or anesthetic complications. METHODS: Data were prospectively collected from 2,183 laboring women randomly assigned to have labor analgesia induced with either 10 microg intrathecal sufentanil with or without 2.0 mg bupivacaine (n = 1,071) or 10 microg epidural sufentanil and 12.5-25.0 mg bupivacaine (n = 1,112). Immediately after induction, a continuous epidural infusion of 0.083% bupivacaine plus 0.3 microg/ml sufentanil was begun in all patients and continued until delivery. Labor was managed by nurses, obstetricians, and obstetric residents who were unaware of the anesthetic technique used. RESULTS: Anesthetic technique lacked impact on our primary outcome: mode of delivery or labor duration. Infants whose mothers were allocated to the combined spinal-epidural group had a slightly higher umbilical artery carbon dioxide partial pressure (54.2 +/- 10.4 vs. 53.2 +/- 10.2 mmHg). However, only achieving at least 5 cm cervical dilation before induction of analgesia and having a cesarean delivery were independent risk factors for elevated umbilical artery carbon dioxide partial pressure. The frequencies of accidental dural puncture, failed epidural analgesia, headache, and epidural blood patch were low and similar in the two groups. CONCLUSIONS: Labor progress and outcome are similar among women receiving either combined spinal-epidural or epidural analgesia. The difference in neonatal outcome appears related to the presence of confounding variables. The combined spinal-epidural technique is not associated with an increased frequency of anesthetic complications. Either technique can safely provide effective labor analgesia.     

A randomized comparison of programmed intermittent epidural bolus with continuous epidural infusion for labor analgesia

Bolus injection through an epidural catheter may result in better distribution of anesthetic solution in the epidural space compared with continuous infusion of the same anesthetic solution. In this randomized, double-blind study we compared total bupivacaine consumption, need for supplemental epidural analgesia, quality of analgesia, and patient satisfaction in women who received programmed intermittent epidural boluses (PIEB) compared with continuous epidural infusion (CEI) for maintenance of labor analgesia. The primary outcome variable was bupivacaine consumption per hour of analgesia. Combined spinal epidural analgesia was initiated in multiparas scheduled for induction of labor with cervical dilation between 2 and 5 cm. Subjects were randomized to PIEB (6-mL bolus every 30 min beginning 45 min after the intrathecal injection) or CEI (12-mL/h infusion beginning 15 min the after the intrathecal injection). The epidural analgesia solution was bupivacaine 0.625 mg/mL and fentanyl 2 microg/mL. Breakthrough pain in both groups was treated initially with patient-controlled epidural analgesia (PCEA) followed by manual bolus rescue analgesia using bupivacaine 0.125%. The median total bupivacaine dose per hour of analgesia was less in the PIEB (n = 63) (10.5 mg/h; 95% confidence interval, 9.5-11.8 mg/h) compared with the CEI group (n = 63) (12.3 mg/h; 95% confidence interval, 10.5-14.0 mg/h) (P < 0.01), fewer manual rescue boluses were required (rate difference 22%, 95% confidence interval of difference 5% to 38%), and satisfaction scores were higher. Labor pain, PCEA requests, and delivered PCEA doses did not differ. PIEB combined with PCEA provided similar analgesia, but with a smaller bupivacaine dose and better patient satisfaction compared with CEI with PCEA for maintenance of epidural labor analgesia.     

Ropivacaine 0.075% and bupivacaine 0.075% with fentanyl 2 microg/mL are equivalent for labor epidural analgesia.

Fifty percent effective dose estimates for ropivacaine and bupivacaine suggest that ropivacaine is 40% less potent than bupivacaine to initiate labor analgesia. At clinically used concentrations, however, the drugs seem indistinguishable for initiating and maintaining labor analgesia. We designed this study to evaluate a concentration near the reported 50% effective dose values for ropivacaine and bupivacaine in an attempt to detect differences between the drugs during routine clinical use. Fifty-nine nulliparous women in labor were randomized to receive 0.075% ropivacaine or bupivacaine, each with fentanyl 2 microg/mL. After epidural placement and the administration of a lidocaine/epinephrine test dose, 20 mL of study solution was administered and a patient-controlled epidural infusion was initiated with the following settings: 6 mL/h basal rate, 5 mL bolus, 10 min lockout, and 30 mL/h limit. Breakthrough pain was treated with 10-mL boluses of study solution. By using a study design to detect a 40% difference in hourly drug use between groups, we found no statistically significant differences in the amount of local anesthetic used, verbal pain scores, sensory levels, motor blockade, labor duration, mode of delivery, side effects, or patient satisfaction. We conclude that 0.075% ropivacaine and bupivacaine, with fentanyl, are equally effective for labor analgesia using the patient-controlled epidural analgesia technique. IMPLICATIONS: At small concentrations, ropivacaine and bupivacaine when combined with fentanyl are equally effective for labor analgesia. Patients self-administered similar volumes of 0.075% ropivacaine or bupivacaine solutions containing fentanyl (2 microg/mL) suggesting that at this concentration, and with the addition of fentanyl, ropivacaine and bupivacaine can be used interchangeably.     

Does epidural versus combined spinal-epidural analgesia prolong labor and increase the risk of instrumental and cesarean delivery in nulliparous women?

Study ObjectiveTo compare duration of labor, mode of delivery, and local anesthetic consumed in women who received labor analgesia with epidural or combined spinal-epidural technique.DesignRetrospective, observational study.SettingDelivery room of a university hospital.Patients788 nulliparous women in labor at term with cervical dilation between three and 5 cm.InterventionsIn Group E (epidural alone), parturients received an epidural solution of 8 mL (levobupivacaine 0.125% with fentanyl 5 μg/mL). In Group CSE (combined spinal-epidural), parturients received a spinal injection of levobupivacaine two mg with fentanyl 15 μg (total volume two mL). Then an epidural catheter was placed in all patients and connected to a patient-controlled analgesia pump (basal infusion rate of 8 mL/hr of 0.1% levobupivacaine and fentanyl two μg/mL, patient-controlled bolus dose of three mL, and lockout time of 30 min).MeasurementsLabor duration, mode of delivery (spontaneous vaginal vs. instrumental delivery vs. cesarean section), and local anesthetic consumed, were recorded.Main ResultsLabor analgesia was performed with an epidural technique in 322 patients (40.9%), and a combined spinal-epidural technique in 466 patients (59.1%), of whom 39 Group E women (12.1%) and 46 Group CSE women (9.9%) required cesarean section (P=ns). No differences in the mode of delivery were observed between the groups. Time from analgesia to delivery (Group E: 217 ± 111 min vs. Group CSE: 213 ± 115 min; P=ns), and epidural local anesthetic consumed (Group E: 35 ± 20 mL vs. Group CSE: 33 ± 20 mL; P=ns), were similar in both groups.ConclusionsNo significant differences were observed between epidural and combined spinal-epidural given for labor analgesia in nulliparous women in duration of labor, mode of delivery, or local anesthetic consumed.     

Does epinephrine improve the diagnostic accuracy of aspiration during labor epidural analgesia?

Aspiration reliably detects almost all IV multiorifice epidural catheters. Although a supplemental epinephrine 15-microg test dose may detect the rare IV catheter that does not yield blood on aspiration, false-positive epinephrine responses may cause some women to unnecessarily undergo repeat epidural catheter insertion. We evaluated 532 consecutive eligible patients requesting neuraxial labor analgesia. Patients were excluded if they had a contraindication to epinephrine or if they received intrathecal sufentanil/bupivacaine. Multiorifice catheters were inserted 4-6 cm into the epidural space as part of an epidural (n = 305) or combined spinal-epidural (n = 270) technique. We used aspiration, a lidocaine/epinephrine test dose, and bolus injection or infusion of dilute bupivacaine/sufentanil solutions to systematically determine IV, intrathecal, or epidural catheter location. Aspiration alone detected 47 of 48 intravascular catheters. There were 10 positive epinephrine responses: 2 were true positives, 7 were falsely positive (subsequent local anesthetic injection/infusion produced bilateral sensory change and analgesia), and 1 catheter was removed without further testing. Aspiration detected almost all intravascular catheters. Although the epinephrine test dose did detect one catheter that proved to be in a blood vessel, 87.5% of positive responses occurred in women without intravascular catheters. IMPLICATIONS: Epidural catheters may enter a blood vessel. Many clinicians use epinephrine to detect these catheters. Because aspiration alone detects almost all IV multiorifice catheters in laboring women, a subsequent epinephrine test dose may be unnecessary.     

Horner's syndrome and trigeminal nerve palsy after lumbar epidural analgesia for labor and delivery

This report highlights transient Horner's syndrome and trigeminal nerve palsy following labor epidural analgesia. A 29-year-old primigravida had a lumbar epidural catheter placed for analgesia in labor. The analgesia was maintained by infusion of a dilute local anesthetic/opioid mixture and turned off after achieving complete cervical dilation. Approximately 1 hour after delivery she complained of heaviness in her left eyelid, and was noted to have left-sided ptosis and paresthesia within the distribution of the ophthalmic and maxillary divisions of the trigeminal nerve, which resolved over the next 2 hours. There were no other neurologic changes. Horner's syndrome and cranial nerve palsies can occur as a consequence of epidural analgesia for labor.     

Are combined spinal-epidural catheters reliable?

The combined spinal-epidural (CSE) technique can rapidly relieve labor pain. However, the location of the epidural catheter is initially uncertain. In an emergency, this untested catheter may fail to provide adequate anesthesia. This study compared the efficacy of catheters placed as a part of an epidural or needle-though-needle CSE technique in laboring women. Patients requesting pain relief received either epidural (n=601) or CSE (n=1061) analgesia. All patients had a 20 gauge, closed tip multi-holed polyamide catheter. (B. Braun Medical, Inc.) inserted 2-8 cm into the epidural space. Catheters were tested to rule out intrathecal and intravascular location. Then, epidural patients received 10-20 ml local anesthetic +/- opioid in divided doses. CSE patients received and infusion of 0.083% bupivacaine with opioid at 10-15 ml/h. Of the 1495 catheters that were adequately tested, those inserted as part of a CSE technique were more likely to produce bilateral sensory change and adequate analgesia than were those inserted without prior spinal analgesia (98.6% vs 98.2%, P<0.02). Stand-alone epidural catheters were more likely to produce neither sensory change nor analgesia than those inserted as part of CSE technique (1.3% vs 0.2%, P<0.02). The only catheters that failed completely and were not intravascular were stand-alone epidural catheters. In this clinical setting, catheters inserted as part of a CSE technique had a high probability of being in the epidural space and functioning appropriately.     

Patient-controlled epidural analgesia for labor and delivery: a novelty or a practical method?

Patient-controlled analgesia, familiar worldwide as “PCA” and derived from a conceptual framework designed to improve standards of pain relief, developed rapidly from an experimental paradigm to the gold standard of modern acute pain management. While PCA has been universally adopted for postoperative parenteral drug administration, as an approach to epidural drug delivery during childbirth, its acceptance has been slow and characterized by isolated flourishes of energy and pockets of clinical activity. Once largely confined to academic or tertiary maternity units, patient-controlled epidural analgesia (PCEA) now seems to be more widely used, although new survey data are awaited before this impression can be affirmed or refuted. World wide, the clinical use of PCEA during labor and delivery varies widely. In parts of North America and Western Europe, PCEA has firmly established a place in the provision of epidural analgesia for parturition, partly accounted for by regional practice patterns, by requirements with respect to epidural management by medical and nursing staff, and by remuneration issues. In other countries and institutions, a variety of factors, not least of which is cost-containment, finds PCEA rarely considered as an alternative to continuous infusion epidural analgesia (CIEA) or intermittent bolus epidural analgesia (IBEA). Consumer-focused epidural services placing emphasis on choice or satisfaction frequently offer PCEA as an option or have adopted PCEA as the routine approach. Nevertheless, while there is strengthening evidence for several advantages of PCEA compared with the alternatives methods of drug delivery, assessing and documenting maternal satisfaction is difficult and any general benefit of PCEA in this respect is largely theoretical. This chapter reviews the literature pertaining to the efficacy and safety of PCEA during labor and delivery, especially in comparison with CIEA and IBEA.     

The distribution of solutions in the epidural space

In 21 patients the distribution within the epidural space of epidurally injected 99mTc-DTPA was assessed. The gamma emissions from the epidural space were measured externally with the patients in supine position by use of a gamma camera. The recordings over the patient's back were stored in digital computer for 60 min. The results were as follows; 1) The spread of the radionuclide was mainly to cephalad direction, and seldom crossed the L5 level to sacral region. 2) The solution injected in the epidural space would distribute to less resistant compartments and the spread depends on the power of injection, negative pressure in the high epidural space and capillary pressure. 3) The elimination half-life of the injected radionuclide was between 1 to 17 min depending on the region in the epidural space. 4) The solution injected in the epidural space may penetrate dura mater at the ink cuff area and local anesthetic agents may affect the spinal nerve roots in the subarachnoid space rather than at the extra-dural space. 5) With continuous infusion technique the diffusion and penetration of the local agent through the dura mater are facilitated and more profound anesthetic effects would be expected. In clinical practice the utilization of the continuous infusion method should be considered along with the bolus injection.     

PCEA compared to continuous epidural infusion in an ultra-low-dose regimen for labor pain relief: a randomized study

BACKGROUND: Patient-controlled epidural analgesia, PCEA, has been introduced in obstetric analgesia during the past decade. Many studies have shown that the consumption of analgesic is reduced when the parturient requests her own doses. This study investigates whether this is also true when using an ultra-low-dose regimen. METHODS: Eighty parturients were prospectively randomized to have either continuous epidural infusion (CEI) with ropivacaine 1 mg ml-1 and sufentanil 0.5 micro g ml-1, 6 ml h-1, or patient-controlled epidural analgesia (PCEA) with 4 ml demand doses with 20 min' lockout. The epidural start dose was the same for the two groups, 8 ml of the study solution. Rescue bolus doses were given when needed and the continuous infusion could be increased, which gave the two groups the same maximum possible dose. The consumption of local ropivacaine in combination with sufentanil during labor was registered. Hourly assessments made throughout labor included pain intensity documented with visual analog score, VAS, the patient's opinion on epidural efficacy, motor block, pruritus and need for nitrous oxide. RESULTS: The PCEA group consumed 33% less of the study solution than the CEI group. Mean total consumption was 35 ml (SD 18.0) and 52 ml (SD 19.6), respectively. Mean hourly consumption was 5.2 ml h-1 (SD 2.54) in the PCEA group and 6.9 ml h-1 (SD 1.31) in the CEI group. There were no significant differences between the two groups in pain relief, epidural efficacy, side-effects or obstetric outcome. CONCLUSION: PCEA reduces doses compared to continuous infusion even when ultra-low-dose local anesthetic with opioid is used. The PCEA technique provides individual titration of doses to an acceptable degree of pain relief.     

The effects of ropivacaine hydrochloride on platelet function: an assessment using the platelet function analyser (PFA-100)

Amide local anaesthetics impair blood clotting in a concentration-dependent manner by inhibition of platelet function and enhanced fibrinolysis. We hypothesised that the presence of ropivacaine in the epidural space could decrease the efficacy of an epidural blood patch, as this technique requires that the injected blood can clot in order to be effective. Ropivacaine is an aminoamide local anaesthetic used increasingly for epidural analgesia during labour. The concentration of local anaesthetic in blood achieved in the epidural space during the performance of an epidural blood patch is likely to be the greatest which occurs (intentionally) in any clinical setting. This study was undertaken to investigate whether concentrations of ropivacaine in blood, which could occur: (i) clinically in the epidural space and (ii) in plasma during an epidural infusion of ropivacaine, alter platelet function. A platelet function analyser (Dade PFA-100, Miami) was employed to assess the effects of ropivacaine-treated blood on platelet function. The greater concentrations of ropivacaine studied (3.75 and 1.88 mg x ml(-1)), which correspond to those which could occur in the epidural space, produced significant inhibition of platelet aggregation. We conclude that the presence of ropivacaine in the epidural space may decrease the efficacy of an early or prophylactic epidural blood patch.     

Regional anesthesia for cesarean section

Spinal or epidural local anesthetics are common and very reliable ways to provide anesthesia for cesarean section. Regional anesthesia avoids many of the maternal risks associated with general anesthesia. Spinal anesthesia is a good choice for elective cesarean section. In laboring women, epidural analgesia can be readily converted to epidural anesthesia. The combined spinal epidural technique is useful when surgery may be prolonged and in patients who may not tolerate standard doses of intrathecal local anesthetic. This article reviews some technical aspects to consider when performing regional anesthesia for cesarean section. It offers suggested protocols for each of these techniques. Lastly, it discusses two common clinical situations: the inadequate epidural anesthetic and the conversion of labor epidural analgesia to operative epidural anesthesia.     

A randomized controlled trial using patient-controlled epidural analgesia with 0.25% versus 0.0625% bupivacaine in nulliparous labor: effect on analgesia requirement and maternal satisfaction

BackgroundThe effect of epidural local anesthetic concentration on analgesic action is still the subject of debate. This study compared the effect of a four-fold change in concentration of bupivacaine for epidural analgesia in labor.MethodsNulliparous women in early active labor were recruited. All women received analgesic drugs via a lumbar epidural catheter, and all received fentanyl 1 μg/kg with the epidural induction dose and no further opioids throughout the study. Patients were randomized to receive either a 5-mL bolus followed by a 5-mL/h infusion of concentrated (0.25%) bupivacaine or a 20-mL bolus followed by a 20-mL/h infusion of dilute (0.0625%) bupivacaine. Patient-controlled epidural analgesia of the study solution was then used to assess additional analgesia requirements. Analgesic requirement, maternal satisfaction and obstetric outcome were compared.ResultsFor subjects receiving 0.25% bupivacaine, the median total dose of drug administered was greater (117 vs. 90 mg, P = 0.0008), and the mean maternal satisfaction score was less (82 vs. 93, P = 0.04) than with the 0.0625% solution.ConclusionsLarger volumes of more dilute solutions may result in dose sparing and provide more effective labor analgesia. This study supports the continued trend towards dilute local anesthetic mixtures for labor epidural analgesia.