The addition of fentanyl to epidural bupivacaine in first stage labour

[Recent standards in management of obstetric anesthesia]

The following article contains information not only for the clinical working anaesthesiologist, but also for other specialists involved in obstetric affairs. Besides a synopsis of a German translation of the current "Practice Guidelines for Obstetric Anaesthesia 2016" [1], written by the American Society of Anesthesiologists, the authors provide personal information regarding major topics of obstetric anaesthesia including pre-anaesthesia patient evaluation, equipment and staff at the delivery room, use of general anaesthesia, peridural analgesia, spinal anaesthesia, combined spinal-epidural anaesthesia, single shot spinal anaesthesia, and programmed intermittent epidural bolus.

Practice Guidelines for Obstetric Anesthesia

The American Society of Anesthesiologists Committee on Standards and Practice Parameters and the Task Force on Obstetric Anesthesia and the Society for Obstetric Anesthesia and Perinatology present an updated report of the Practice Guidelines for Obstetric Anesthesia.

Supplemental Digital Content is available in the text.

A Comparison of Minimum Local Anesthetic Volumes and Doses of Epidural Bupivacaine (0.125% w/v and 0.25% w/v) for Analgesia in Labor

BACKGROUND

In this study we sought to determine and compare the minimum local anesthetic volumes (MLAV) and doses (MLAD) of two concentrations of bupivacaine for epidural pain relief in labor, and to quantify the effect on dose.

METHODS

Eighty women were randomized in a double-blind manner to receive a first bolus of either plain bupivacaine 0.125% (w/v) or 0.25% (w/v). The arbitrary starting volume was 15 mL. Subsequent volumes were decided by sequential allocation according to analgesic efficacy. A visual analog pain score < or =10 (0-100) within 30 min, indicated effective analgesia. The next woman received a decrement of 2 mL. A failure of the visual analog pain score to reach < or =10 was followed by a 2 mL increment for the next woman.

RESULTS

Using the formula of Dixon and Massey, MLAV and MLAD, with 95% confidence intervals (CI) were calculated for each concentration. MLAV was 13.6 mL (95% CI 12.4-14.8), with bupivacaine 0.125% (w/v), and 9.2 mL (95% CI 6.9-11.5) with bupivacaine 0.25% (w/v). The difference was highly significant (P = 0.002). MLAD for these volumes were 17.0 mg (95% CI 15.5-18.5), and 23.1 mg (17.2-28.9), respectively (P = 0.045).

CONCLUSIONS

Bupivacaine 0.125% (w/v) when compared with 0.25% (w/v) produced equivalent analgesia with a 50% increase in volume, but with a 25% reduction in dose. Any reduction in dose, without loss of efficacy, reduces risk of toxicity and improves safety.

Determination of the analgesic dose-response relationship for epidural fentanyl and sufentanil with bupivacaine 0.125% in laboring patients

STUDY OBJECTIVE

To establish the analgesic effective doses as defined as a visual analog pain scale (VAS) of at least 10 for 95% of parturients (ED95) receiving either epidural fentanyl or sufentanil with bupivacaine 0.125% for labor analgesia.

DESIGN

Double-blind, randomized controlled study.

SETTING

Two tertiary-care teaching hospitals.

PATIENTS

100 female patients, at full-term pregnancy, in active early labor (< 5 cm cervical dilation) and requesting obstetric anesthesia services for labor analgesia.

INTERVENTIONS

Patients were randomized and equally distributed to receive one of ten epidural dosing regimens of bupivacaine 0.125% alone or with either fentanyl 25, 50, 75, or 100 micrograms or sufentanil 5, 10, 15, 20, or 25 micrograms in a 10-ml bolus after a 3-ml test dose of bupivacaine 0.25%.

MEASUREMENTS AND MAIN RESULTS

VAS scores were obtained from each parturient using a 10-cm plastic VAS slide rule at times 0, 1, 5, 10, 15, 20, 25, and 30 minutes, and then again when the patient requested additional analgesia. Analgesic duration and demographic and obstetric data also were obtained. Using a log-probit dose-response analysis, analgesic success as defined as a VAS of at least 10 with each opioid dose was plotted and an ED95 value of 8 micrograms and 50 micrograms was established for sufentanil and fentanyl, respectively, in bupivacaine 0.125%. No statistical difference was detected for analgesic duration or incidence of side effects between analgesic groups.

CONCLUSIONS

Epidural analgesia with fentanyl and sufentanil in bupivacaine 0.125% behaves in a dose-response fashion allowing for the determination of equipotent dose of each.

Comparison of 15 mg and 25 mg of bupivacaine both with 50 μg fentanyl as initial dose for epidural analgesia

Bupivacaine 15 mg is commonly used as a test dose prior to the initial dose for epidural analgesia in labour. When 15 mg or 25 mg of bupivacaine (15 ml of 0.1% or 0.167%) with 50 microg fentanyl was administered blindly to two groups of labouring women, as an initial dose, 83% and 90% of women respectively, achieved analgesia within 20 min. All the remaining women achieved analgesia with a further dose of 10 mg bupivacaine (10 m10.1%) with fentanyl 2 microg per ml given at 20 min.

Patient controlled epidural analgesia during labour: choice of solution

Epidural characteristics, when using different solutions for patient controlled epidural analgesia (PCEA), were compared in a randomised, blinded study in labour. Women in group 1 (n=23) self-administered 0.25% plain bupivacaine, in group 2 (n=23) 0.125% plain bupivacaine plus fentanyl 3 microg/ml and in group 3 (n=20) 0.0625% bupivacaine with adrenaline 1:250,000 plus fentanyl 3 microg/ml. There were no significant differences between groups with respect to the quality of obstetric pain relief or maternal satisfaction, the requirement for supplementary boluses of staff-administered solution or the incidence of side effects. There was more intense motor block after 3 hours of PCEA (odds ratio 3.33 for score 0 versus 1, 2 or 3) and a significantly higher ratio of demands received to demands made (P<0.03) in group 1 compared groups 2 and 3. The rate of bupivacaine utilisation was significantly higher in group 1 compared to groups 2 and 3 and lower in group 3 compared to 1 and 2 (median+interquartile range: 16+11-21 vs 9+6-11 vs 4+3-8 mg/hr, P<0.0002). Although all solutions provided effective pain relief for PCEA during labour, the use of a low-dose bupivacaine-fentanyl combination offers clinical advantages and further evaluation of such solutions is warranted.

The addition of pethidine to epidural bupivacaine in labour--effect of changing bupivacaine strength

The effects of varying the strength of bupivacaine used in epidurals for the relief of labour pain was examined. The trial randomly allocated sixty women in the first stage of labour to one of three groups. All women were of ASA status 1 or 2 and had uncomplicated pregnancies. Subjects in each group received pethidine 25 mg in 10 ml of either 0.125%, 0.1875%, or 0.25% bupivacaine. Pain scores for each patient were then assessed over the following thirty minutes. Duration of analgesia and subsequent dose requirements were examined. No difference in pain scores between groups at thirty minutes after injection of the test solutions was found. The 0.25% solution group did however have a more rapid onset of analgesia with the majority of patients in this group achieving their maximum effect between ten and twenty minutes after injection. Duration of analgesia was not prolonged by using the stronger solutions. This study suggests that when epidural pethidine 25 mg is added to local anaesthetic solutions of bupivacaine, adequate analgesia for the first stage of labour is achieved with the 0.125% bupivacaine solution. The use of stronger solutions of bupivacaine achieves no greater degree of analgesia nor longer duration of action, although the onset of analgesia may be faster with the stronger solutions. Further investigations are needed to determine if 25 mg of pethidine is the best choice of dose to use under these circumstances.

Obstetric epidural analgesia with mixtures of bupivacaine, adrenaline and fentanyl

We performed a double-blind comparison of six solutions for epidural analgesia in 90 healthy Chinese women with uncomplicated pregnancies. Patients were randomly allocated to receive 10 ml bupivacaine 0.125% or 0.25% plain, bupivacaine 0.125% with adrenaline 1.25 micrograms/ml, bupivacaine 0.25% with adrenaline 2.5 micrograms/ml or the latter two solutions with added fentanyl 50 micrograms. Analgesia was unsatisfactory in 30% of the bupivacaine 0.125% groups without fentanyl. The addition of adrenaline, compared with bupivacaine 0.25% plain, gave faster onset and longer duration of analgesia (p less than 0.05) which was similar to that found in both fentanyl groups. There were no differences in method of delivery or neonatal Apgar scores among groups. The least concentrated mixture that gave the best analgesia was the combination of bupivacaine 0.125% with adrenaline 1.25 micrograms/ml and fentanyl 50 micrograms.