Effective obstetric paracervical block with reduced dose of bupivacaine. A prospective randomized double-blind study comparing 25 mg (0.25%) and 12.5 mg (0.125%) of bupivacaine

[Liposomal bupivacaine-No breakthrough in postoperative pain management]

One of the main limitations concerning the use of local anesthetics is due to their restricted duration of action. In recent years, liposomal formulations with prolonged release kinetics have been developed to extend the pharmacological duration of action of the 1‑stage peripheral regional anesthesia (single-shot procedure) and thus bring about a longer duration of action. The focus here is particularly on achieving postoperative freedom from pain for at least 24 h (or even better 48 h) and thus early mobilization of patients using on-demand medication causing (at most) minor local sensory blockade without causing motor impairments (at least that is the ideal). Therefore, methods of utilizing slow-release drugs as seen in liposomal carrier systems have experienced increasing scientific attention in the last few years. A common modern pharmacological example with a theoretically significantly longer duration of action is liposomal bupivacaine, an amide local anesthetic. Due to a multivesicular liposome structure, the retarded release of the active component bupivacaine HCl leads to a theoretical pharmacological effectiveness of up to 72 h. Previous studies consistently showed a safety profile comparable to conventional bupivacaine HCl. Liposomal bupivacaine has been approved by the U.S. Food and Drug Administration (FDA) under the trade name Exparel© (Pacira Pharmaceuticals, Parsippany, NJ, USA) since 2011; however, its use is currently limited to local wound infiltration, transverse abdominis plane (TAP) blocks, and interscalene nerve blocks of the brachial plexus. In 2020, the European Medicines Agency (EMA) also approved the use of liposomal bupivacaine for blockade of the brachial plexus or the femoral nerve and as a field block or for wound infiltration to treat postoperative pain. So far, studies on the clinical effectiveness of liposomal bupivacaine have been very heterogeneous and there have been no conclusive meta-analyses with sufficient rigor or significance. Recent systematic reviews and meta-analyses, combining the results of clinical studies regarding the analgesic efficiency of liposomal bupivacaine in different fields of application, consistently refuted any benefit of clinical relevance provided by the liposomal formulation. There is currently sufficient evidence to now end the ongoing debate around liposomal bupivacaine. The aim of this work is to give the reader a current, evidence-based overview of this substance.

Local anaesthetic nerve block for pain management in labour

BACKGROUND

Local anaesthetic nerve block is an important modality for pain management in labour. Pudendal and paracervical block (PCB) are most commonly performed local anaesthetic nerve blocks which have been used for decades.

OBJECTIVES

To establish the efficacy and safety of local anaesthetic nerve blocks for pain relief in labour.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (28 February 2012).

SELECTION CRITERIA

We included randomised controlled trials (RCTs) assessing pain management in labour with the use of local anaesthetic nerve blocks. We did not include results from quasi-RCTs.

DATA COLLECTION AND ANALYSIS

We designed a form to extract data. For eligible studies, two review authors extracted the data using the agreed form. We resolved discrepancies through discussion or, if required, we consulted a third person. We entered and analysed data using Review Manager software and checked for accuracy.

MAIN RESULTS

We found 41 trials for consideration of inclusion into this review. We included only 12 RCTs (1549 participants) of unclear quality. We excluded 29 studies (30 reports). The majority of excluded studies were not relevant to this review, and a few were not randomised.Local anaesthetic nerve block versus placebo or no treatment. We found that more women were satisfied with pain relief after local anaesthetic nerve block (in particular 2% lidocaine PCB) than after placebo (one study, 198 participants, risk ratio (RR) 32.31, 95% confidence interval (CI) 10.60 to 98.54). Local anaesthetic nerve block was associated with more side effects (one study, 200 participants, RR 29.0, 95% CI 1.75 to 479.61).Local anaesthetic nerve block (in particular, PCB) versus opioid Local anaesthetic nerve block (in particular, PCB) in comparison with opioid (in particular, intramuscular pethidine or fentanyl patient-controlled analgesia) was found to be more effective for pain relief (one study, 109 participants, RR 2.52, 95% CI 1.65 to 3.83) and was not associated with an increased rate of assisted vaginal birth (two studies, 129 participants, RR 1.02, 95% CI 0.56 to 1.87) or with an increased caesarean section rate (two studies, 129 participants, RR 0.23, 95% CI 0.03 to 1.87).Local anaesthetic nerve block versus non-opioid agents Satisfaction with pain relief and rate of caesarean sections were found to be the same in women receiving local anaesthetic nerve block and non-opioid agents (one study, 100 participants, RR 1.11, 95% CI 0.67 to 1.84; RR 2.0, 95% CI 0.19 to 21.36, respectively). More women who received non-opioid agent in comparison with women who received local anaesthetic nerve block required additional interventions for pain relief (one study, 100 participants, RR 0.06, 95% CI 0.02 to 0.25).Local anaesthetic nerve block using different anaesthetic agents There was no difference in pain relief satisfaction, assisted vaginal birth, caesarean section, side effects for mother, Apgar score or admission to the neonatal intensive care unit between different anaesthetic agents, e.g. bupivacaine, carbocaine, lidocaine, chloroprocaine.

AUTHORS' CONCLUSIONS

Local anaesthetic nerve blocks are more effective than placebo, opioid and non-opioid analgesia for pain management in labour based on RCTs of unclear quality and limited numbers. Side effects are more common after local anaesthetic nerve blocks in comparison with placebo. Different local anaesthetic agents used for pain relief provide similar satisfaction with pain relief. Further high-quality studies are needed to confirm the findings, to assess other outcomes and to compare local anaesthetic nerve blocks with various modalities for pain relief in labour.

[Paracervical block in obstetrics]

OBJECTIVE

To review the most recent and relevant issues concerning paracervical block in obstetrics since 1975 when Jägerhorn described the superficial technique that has become a standard.

DATA SOURCES

Extraction from Pubmed database of articles issued from 1975 to 2005.

DATA SELECTION

The collected articles were selected on the basis of the use of the superficial injection method. The more recent data were selected. The keywords were: paracervical, labour, childbirth, and neonate.

DATA SYNTHESIS

Paracervical block (PCB) is routinely used over the world despite the risk of foetal bradycardia. Bradycardia occurring immediately after the performance of block is short lasting. The reports of few cases of foetal or neonatal deaths have caused many physicians to question its safety. The incidence of bradycardia has dramatically decreased (less than 10%) due to the Jägerhorn superficial injection method. In case of healthy neonate the occurrence of bradycardia is harmless but its mechanism is still imprecise. The intensity an duration of analgesia is poor in comparison with epidural anaesthesia. PCB is a viable alternative to epidural in selected cases.

A comparative study of the safety of 0.25% levobupivacaine and 0.25% racemic bupivacaine for paracervical block in the first stage of labor

BACKGROUND

The objective of the study was to evaluate and compare the safety of levobupivacaine and racemic bupivacaine for paracervical block (PCB) in the first stage of labor after uncomplicated pregnancy.

METHODS

Forty women in an open pilot study and 397 women in a double-blind randomized study received PCB for pain relief in the first stage of labor, either with 25 mg of levobupivacaine or with 25 mg of racemic bupivacaine. The incidence of cardiotocographic pathology was compared between the groups using Fisher's exact test. The 95% confidence intervals for the between-group difference were calculated by Newcombe's method.

RESULTS

In the randomized double-blind study, the incidence of any pathological result in cardiotocography (CTG) was 10.4% in the levobupivacaine group and 12.8% in the racemic bupivacaine group. The incidence of fetal bradycardia in the groups was 2.6 and 3.8%, respectively. All the cardiotocographic changes were transient, and no operative intervention was indicated because of CTG. No difference in the analgesic effect between the drugs was found. Most of the parturients in the levobupivacaine group (97%) and in the racemic bupivacaine group (96%) had spontaneous vaginal delivery. Neonatal outcome was good in both groups.

CONCLUSIONS

No difference in cardiotocographic pathology was found between PCB with levobupivacaine compared with PCB with racemic bupivacaine. The incidence of bradycardia was low. PCB was found to be a safe pain-relief method for low-risk parturients.

What determines the analgesic effect of paracervical block?

BACKGROUND

The objective of the study was to evaluate the analgesic effect of paracervical block (PCB) in labor pain relief and to discover the determinants associated with good analgesia.

METHODS

In a prospective trial, 341 women received PCB for pain relief in the first stage of labor, with 10 ml of 0.25% levobupivacaine or racemic bupivacaine. All these pregnancies were uncomplicated and the progress of labor was normal. The analgesic effect of PCB was measured by using a visual analog scale (VAS). The factors associated with good pain relief (>50% decrease in the VAS score within 30 min) were analyzed statistically by Student's t-test or the Mann-Whitney test (continuous variables), Fisher's exact test (categorial variables) and after univariate analysis by logistic regression analysis. For pairwise comparisons, Wilcoxon's signed ranks test was used.

RESULTS

Good pain relief was achieved in 47.2% of the cases. 12.3% of the parturients needed subsequent epidural or spinal analgesia. In logistic regression analysis, primiparity, a high pain score before PCB, and PCB given by a specialized obstetrician were found to affect the level of pain relief 30 min after PCB.

CONCLUSIONS

The best pain relief after PCB was achieved among primiparas. Good pain relief was connected with a high pain score before PCB and an experienced obstetrician.

Newer techniques of labor analgesia

In maternity units in which central neuraxial techniques are frequently used, newer methods of epidural drug delivery (continuous infusion, patient-controlled) are well established and combined spinal-epidural analgesia is commonly used. Continuous spinal analgesia has reemerged as a useful approach after accidental dural puncture. Lumbar sympathetic block has been revisited and the safety of paracervical nerve block improved. The analgesic properties of systemic opioid in labor are poor, but PCIA at least has psychological benefits and allows rapid drug titration. PCIA is again under investigation because of the potent antinociceptive effects of the short-acting mu-opioid agonist, remifentanil. The premixing of nitrous oxide and a subanesthetic concentration of volatile anesthetic for patient-controlled administration has been tested under control of midwifery staff and without direct medical supervision.

Regional anesthesia for obstetrics

The practice of administration of labor analgesia has undergone dramatic changes this decade. This is largely attributable to unparalleled interest in the field by many dedicated and capable investigators around the world. Through their efforts, this decade has witnessed the introduction of new techniques (pencil point needles, CSE, PCEA, ultradilute epidural regimens) that have permitted us to come closer than ever to realizing the goal of complete relief from the pain and suffering of labor while safeguarding the well-being of mother and child and minimizing effects on the labor process. Neuraxial anesthetic techniques and modern multimodal analgesic approaches to postoperative pain relief now minimize the effects of cesarean delivery on maternal satisfaction and participation in the birth process.

A comparison of the hemodynamic effects of paracervical block and epidural anesthesia for labor analgesia

BACKGROUND

Both paracervical block (PCB) and epidural analgesia are sometimes associated with hemodynamic effects potentially harmful to the well-being of the fetus. Our study was designed to test the hypothesis that PCB would have a more profound effect on maternal and fetal blood flow than epidural analgesia.

METHODS

Forty-four healthy primiparous parturients were randomized to receive either PCB (n=21) or epidural analgesia (n= 23) with 25 or 30 mg of bupivacaine, respectively, for labor analgesia. Maternal blood pressure and fetal heart rate were recorded. Blood flow was measured using a color Doppler device. The blood flow measurements consisted of assessment of the pulsatility indices (PI) of the right maternal femoral artery and the main branch of the uterine artery (placental side), the umbilical artery and the fetal middle cerebral artery. The measurements were performed before administration of analgesia and approximately 15-20 min later after the onset of analgesia.

RESULTS

Both methods provided in general good analgesia, but rescue medication was required more often after PCB. Epidural analgesia decreased maternal blood pressure more than PCB and the PI of maternal femoral artery decreased after onset of epidural analgesia, indicating epidural-induced vasodilation. The PI of the uterine artery increased after the onset of PCB, indicating vasoconstriction of this artery. No significant adverse effects or differences in the well-being of the newborn were observed, as indicated by similar Apgar scores and pH-status.

CONCLUSION

There were small differences in the effects of PCB and epidural analgesia on uteroplacental circulation as well as on maternal hemodynamics. PCB may have a vasoconstrictive effect on the uterine artery. This and the fact that the parturients required rescue analgesia more frequently after PCB than after epidural block speaks for the feasibility of the latter in obstetrics.