Epidural infusion of alfentanil or diamorphine with bupivacaine in labour--a dose finding study

The 90% effective concentration of alfentanil combined with 0.075% ropivacaine for epidural labor analgesia: a single-center, prospective, double-blind sequential allocation biased-coin design

PURPOSE

More literature studies have reported that alfentanil is safe and effective for labor analgesia. However, there is no unified consensus on the optimal dosage of alfentanil used for epidural analgesia. This study explored the concentration at 90% of minimum effective concentration (EC90) of alfentanil combined with 0.075% ropivacaine in patients undergoing epidural labor analgesia to infer reasonable drug compatibility and provide guidance for clinical practice.

METHODS

In this prospective, single-center, double-blind study, a total of 45 singleton term primiparas with vaginal delivery who volunteered for epidural labor analgesia were recruited. The first maternal was administered with 3 μg/mL alfentanil combined with 0.075% ropivacaine with the infusion of 10 mL of the mixture every 50 min at a background dose of 3 mL/h. In the absence of PCEA, a total of 15 mL of the mixture is injected per hour. The subsequent alfentanil concentration was determined on the block efficacy of the previous case, using an up-down sequential allocation with a bias-coin design. 30 min after epidural labor analgesia, the block of patient failed with visual analog score (VAS) > 3, the alfentanil concentration was increased in a 0.5 μg/mL gradient for the next patient, while the block was successful with VAS ≤ 3, the alfentanil concentration was remained or decreased in a gradient according to a randomized response list for the next patient. EC90 and 95% confidence interval were calculated by linear interpolation and prediction model with R statistical software.

RESULTS

In this study, the estimated EC90 of alfentanil was 3.85 μg/mL (95% confidence interval, 3.64-4.28 μg/mL).

CONCLUSION

When combined with ropivacaine 0.075%, the EC90 of alfentanil for epidural labor analgesia is 3.85 μg/mL in patients undergoing labor analgesia.

'Soothing the ring of fire': Australian women's and midwives' experiences of using perineal warm packs in the second stage of labour

OBJECTIVE

to determine women's and midwives' experiences of using perineal warm packs in the second stage of labour.

DESIGN

as part of a randomised controlled trial (Warm Pack Trial), women and midwives were asked to complete questionnaires about the effects of the warm packs on pain, perineal trauma, comfort, feelings of control, satisfaction and intentions for use during future births.

SETTING

two hospitals in Sydney, Australia.

PARTICIPANTS

a randomised controlled trial was undertaken. In the late second stage of labour, nulliparous women (n=717) giving birth were randomly allocated to having warm packs (n=360) applied to their perineum or standard care (n=357). Standard care was defined as any second stage practice carried out by midwives that did not include the application of warm packs to the perineum. Three hundred and two nulliparous women randomised to receive warm packs (84%) received the treatment. Questionnaires were completed by 266 (88%) women who received warm packs, and 270 (89%) midwives who applied warm packs to these women.

INTERVENTION

warm, moist packs were applied to the perineum in the late second stage of labour.

FINDINGS

warm packs were highly acceptable to both women and midwives as a means of relieving pain during the late second stage of labour. Almost the same number of women (79.7%) and midwives (80.4%) felt that the warm packs reduced perineal pain during the birth. Both midwives and women were positive about using warm packs in the future. The majority of women (85.7%) said that they would like to use perineal warm packs again for their next birth and would recommend them to friends (86.1%). Likewise, 91% of midwives were positive about using the warm packs, with 92.6% considering using them in the future as part of routine care in the second stage of labour.

KEY CONCLUSIONS

responses to questionnaires, eliciting experiences of women and midwives involved in the Warm Pack Trial, demonstrated that the practice of applying perineal warm packs in the late second stage of labour was highly acceptable and effective in helping to relieve perineal pain and increase comfort.

IMPLICATIONS FOR PRACTICE

perineal warm packs should be incorporated into second stage pain relief options available to women during childbirth.

Techniques to reduce perineal pain during spontaneous vaginal delivery and perineal suturing: a UK survey of midwifery practice

OBJECTIVE

To investigate use of pharmacological and non-pharmacological methods of perineal analgesia used by midwives during the second stage of labour and perineal repair in the UK.

DESIGN

Postal survey.

METHODS

Self-complete questionnaires were sent to Heads of Midwifery in all 219 maternity units in the UK. Information was requested on the number and type of deliveries undertaken in the previous year and on the midwifery procedures used to provide pain relief immediately before delivery and for perineal repair. Details were also sought on local anaesthetics given before episiotomy or perineal repair.

FINDINGS

207 completed questionnaires were returned providing information on 210 maternity units. Midwives reported using a variety of non-pharmacological analgesic methods to control pain at the end of the second stage of labour. Hot packs were used in 70 (33%) maternity units, cold packs in 44 (21%) and perineal massage in 109 (52%). Midwives in 131 (62%) maternity units used injectable local anaesthetics to control perineal pain. All units advocated use of local anaesthetic before episiotomy or perineal repair, but the reported doses used varied widely.

CONCLUSIONS

The literature on levels of pain experienced immediately before spontaneous vaginal delivery and during perineal repair is sparse, but what evidence exists suggests that, for some women, these occasions are accompanied by severe pain. Findings from this survey show that there is considerable variation in what midwives provide to control pain. Formal evaluation of the perineal analgesia offered to women during the second stage of labour is urgently required.

Is the clinical efficacy of epidural diamorphine concentration-dependent when used as analgesia for labour? †

BACKGROUND

The physicochemical properties of diamorphine (3,6-diacetylmorphine) enhance its bioavailability compared with more lipid-soluble opioids when administered into the epidural space. However, the influence of concentration, volume or mass on the clinical efficacy of diamorphine is not known.

METHOD

In this double-blind, randomized, prospective study, 62 women in active labour and </=5 cm cervical dilatation were recruited to determine whether the mode of action of diamorphine in the epidural space is concentration-dependent. After insertion of a lumbar epidural catheter, patients received epidural diamorphine 3 mg either as a high-volume, low-concentration solution (group A) or a low-volume, high-concentration solution (group B). The concentration of diamorphine was determined by the response of the previous patient in the same group using up-down sequential allocation. Pain corresponding to the previous contraction was assessed using a 100-mm visual analogue score and effective analgesia was defined as </=10 mm within 30 min of epidural injection.

RESULTS

There was no significant difference in EC50 for diamorphine between the groups: the difference was 15.0 microg ml(-1) (95% CI -40.3 to 10.3). The EC50 for group A was 237.5 microg ml(-1) (95% CI 221.2 to 253.8) and the EC50 for group B was 252.5 microg ml(-1) (95% CI 232.2 to 272.8). The EC50 ratio was 0.95 (95% CI 0.87 to 1.06). The groups exhibited parallelism (P=0.98). The overall EC50 for all data was 244.2 microg ml(-1) (95% CI 230.8 to 257.2).

CONCLUSION

We conclude that diamorphine provides analgesia in labour by a concentration-dependent effect.

Continuous epidural analgesia with bupivacaine 0.125% or bupivacaine 0.0625% plus sufentanil 0.25 μg·mL−1: a study in singleton breech presentation

Epidural analgesia is the most efficient technique for labor pain relief. However, its resultant motor block might impair the mode of delivery, particularly in breech presentation where the risk of dystocia is high. In this trial, we compared bupivacaine 0.125% with a combination of a low concentration of bupivacaine (0.0625%) and sufentanil (0.25 microg.mL(-1)) both administered by continuous infusion. Analgesia, maternal and fetal/neonatal side effects and obstetric outcome were compared between group bupivacaine (n = 23) and group bupivacaine-sufentanil (n = 35). A greater number of patients in the bupivacaine 0.125% group required more than two top-ups (32 vs. 8% of patients, P = 0.03) while pain scores were similar. Motor block at delivery was more pronounced in the bupivacaine 0.125% group. Nausea and pruritus were more often encountered in the bupivacaine-sufentanil group. There was a trend toward a decreased rate of assisted or operative delivery in the bupivacaine-sufentanil group (92% vs. 74%, P = 0.09). Fetal/neonatal data did not differ between groups. Epidural analgesia with bupivacaine-sufentanil required fewer additional top-ups and produced less motor block than did bupivacaine 0.125%. However, there was no significant difference in mode of delivery between the two analgesic regimens.

Intrathecal diamorphine for analgesia after caesarean section. A dose finding study and assessment of side-effects

Eighty women undergoing elective Caesarean section under spinal anaesthesia using hyperbaric bupivacaine 0.5% were randomly allocated to receive, in addition, intrathecal diamorphine 0.125, 0.25 or 0.375 mg or saline. Postoperative morphine requirements, measured using a patient-controlled analgesia system, were reduced in a dose-dependent manner by diamorphine. Pain scores were significantly lower at 2 and 6 h following the two larger doses of diamorphine. Less supplemental analgesia was required intra-operatively if intrathecal diamorphine had been given. The incidences of vomiting and pruritus were also dose-related. No respiratory rates of less than 14 breath.min-1 were recorded and the incidence of oxygen saturation readings less than 95% and 90% did not differ between groups. There were no adverse neonatal effects. Intrathecal diamorphine in the present study was found to be safe in doses of up to 0.375 mg following Caesarean section. However, minor side-effects were frequently observed.

Segmental effects on motor function following different intrathecal receptor agonists and antagonists in rabbits

BACKGROUND

The occurrence of motor impairment after intrathecal drug administration is infrequently reported in the literature and the methods of determining motor function vary.

METHODS

Motor function was examined in rabbits after a wide dose range of a variety of intrathecally administered opioid agonists, alpha-adrenergic agonists, non-competitive NMDA antagonists, a benzodiazepine agonist, a sigma agonist, paracetamol, isotonic and acidified saline. The opioids, sigma agonist and NMDA antagonists were additionally examined following pretreatment with naloxone. The opioid antagonists naltrindole and MR2266 (delta- and kappa-opioid receptor antagonists, respectively) were administered before the delta agonist and the kappa agonist. The alpha 2-adrenergic antagonist yohimbine was given before administration of dexmedetomidine and xylazine. Motor function was evaluated by a five-point scale of motor impairment ranging from normal function to total paralysis of the hindlegs.

RESULTS

DPDPE (delta agonist), paracetamol, naloxone, naltrindole, yohimbine, isotonic and acidified saline did not affect motor function. MR2266 produced minor motor impairment. The alpha-adrenergic agonist dexmedetomidine reduced motor function slightly and dose independently. The remaining compounds affected motor function in a dose-dependent fashion. High doses of morphine produced hypersensitivity and myoclonus. An irreversible paralysis of the hindlegs was observed following intrathecal administration of the sigma agonist SKF10047 in high doses. Naloxone and MR2266 attenuated the effects of U50488H (kappa agonist).

CONCLUSION

The present results reveal a dose-dependent reduction in motor function after intrathecal administration of some of the investigated compounds. The mechanisms behind these effects appear to be multifactorial.