Side effects of the addition of clonidine 75 μg or sufentanil 5 μg to 0.2% ropivacaine for labour epidural analgesia

Mechanisms and treatment of opioid-induced pruritus: Peripheral and central pathways

BACKGROUND AND OBJECTIVE

Pruritus (also known as itch) is defined as an unpleasant and irritating sensation of the skin that provokes an urge to scratch or rub. It is well known that opioid administration can cause pruritus, which is paradoxical as itch and pain share overlapping sensory pathways. Because opioids inhibit pain but can cause itching. Significant progress has been made to improve our understanding of the fundamental neurobiology of itch; however, much remains unknown about the mechanisms of opioid-induced pruritus. The prevention and treatment of opioid-induced pruritus remains a challenge in the field of pain management. The objective of this narrative review is to present and discuss the current body of literature and summarize the current understanding of the mechanisms underlying opioid-induced pruritus, and its relationship to analgesia, and possible treatment options.

RESULTS

The incidence of opioid-induced pruritus differs with different opioids and routes of administration, and the various mechanisms can be broadly divided into peripheral and central. Especially central mechanisms are intricate, even at the level of the spinal dorsal horn. There is evidence that opioid receptor antagonists and mixed agonist and antagonists, especially μ-opioid antagonists and κ-opioid agonists, are effective in relieving opioid-induced pruritus. Various treatments have been used for opioid-induced pruritus; however, most of them are controversial and have conflicting results.

CONCLUSION

The use of a multimodal analgesic treatment regimen combined with a mixed antagonist and κ agonists, especially μ-opioid antagonists, and κ-opioid agonists, seems to be the current best treatment modality for the management of opioid-induced pruritus and pain.

SIGNIFICANCE

Opioids remain the gold standard for the treatment of moderate to severe acute pain as well as cancer pain. It is well known that opioid-induced pruritus often does not respond to regular antipruritic treatment, thereby posing a challenge to clinicians in the field of pain management. We believe that our review makes a significant contribution to the literature, as studies on the mechanisms of opioid-induced pruritus and effective management strategies are crucial for the management of these patients.

Investigation of the Minimum Local Analgesic Concentration of Epidural Sufentanil Combined With Ropivacaine for Labor Analgesia

PURPOSE

Worldwide, there are only few studies focusing on labor analgesia on the MLAC (minimum local analgesic concentration) or EC50 (median effective concentration) of sufentanil and ropivacaine. Therefore, we determine the MLAC or EC50 of sufentanil and ropivacaine for epidural analgesia by using an up-down sequential allocation and survey its adverse effect in a prospective blinded randomized trial.

METHODS

Sixty nulliparous full-term parturients who required labor analgesia were recruited and randomly divided into the sufentanil and ropivacaine groups. The formulation was 25 μg sufentanil combined with 0.1% ropivacaine (added 0.9% normal saline to 75 ml). According to the response of a previous parturient, the dosage of sufentanil was increased or decreased by 5 μg in the sufetanil group; meanwhile, we also administrated an initial concentration of 0.1% ropivacaine combined with 22.5 μg sufentanil (added 0.9% normal saline to 75 ml) in the ropivacaine group. The concentration of ropivacaine was increased or decreased by 0.01% following the response of the previous parturient. The Brownlee up-down sequential allocation was used to estimate the MLAC of epidural ropivacaine and its 95% confidence intervals in labor analgesia.

FINDINGS

There were no significant changes for the two groups, including for age, height weight, active stage, second stage of labor, and gestational weeks (P = 0.769, 0.900, 0.603, 0.441, 0.577, and 0.695, respectively). The VAS scores of the parturient decreased to varying degrees (P < 0.0001) after labor analgesia compared with VAS before labor analgesia, and the most effective analgesia was reached in 60 min. The EC50 dose of epidural ropivacaine combined with 0.3 μg/mL sufentanil was 0.09687%, and the 95% CI was 0.08944%~0.1043%. Five parturients had PONV, and the incidence rate was 16.7%; one parturient had pruritus, so the incidence rate was 3.3%. The EC50 dose of epidural sulfetanil combined with 0.1% ropivacaine was 18.76 μg with a 95% confidence interval of 13.5-24.48 μg. There were no significant differences in the active stage, second stage of labor, and maternal and fetal hemodynamic data between the two groups. Notably, the Apgar scores for 1 min and 5 min were 10 scores for almost all of these patients. There were no significant differences between the two groups for maternal and fetal side effects, which had very low incidence rates.

IMPLICATIONS

The MLAC of epidural sufentanil or ropivacaine could provide satisfactory and safe analgesia for parturients while having a low incidence rate of side effects.

Comparative efficacy of epidural clonidine versus epidural fentanyl for treating breakthrough pain during labor: a randomized double-blind clinical trial

BACKGROUND

Breakthrough pain during neuraxial labor analgesia is typically alleviated with additional administration of epidural local anesthetics, with or without adjuvants. Sometimes avoiding neuraxial opioids may be warranted and clonidine is an alternative. In a randomized double-blind trial we compared the efficacy of clonidine versus fentanyl, added to bupivacaine, for the management of breakthrough pain.

METHODS

Term parturients (n=98) receiving bupivacaine 0.0625% with fentanyl 2 μg/mL at 12 mL/h, a patient-administered bolus of 5 mL at lockout 6-10 min and a maximum of four boluses per hour, and experiencing breakthrough pain ≥5/10, were randomized to receive a 10 mL bolus containing 12.5 mg bupivacaine and either clonidine 100 μg or fentanyl 100 μg. The primary outcome was 'success' of study drug treatment, defined as a pain score reduction ≥4/10 within 15 min of administration. Maternal hemodynamics and fetal heart rate were documented for two hours after treatment.

RESULTS

There was no significant difference between groups in success rates (66.0% after clonidine (n=47) vs 74.5% after fentanyl (n=51), P=0.48) or in the incidence of hypotension (systolic blood pressure ≤80% of baseline or <90 mmHg) or sedation at 15 min, with 2/51 and 1/47 subjects in the fentanyl and clonidine groups, respectively, receiving phenylephrine.

CONCLUSION

Epidural clonidine 100 μg was not superior to fentanyl 100 μg for decreasing pain scores within 15 min of co-administration with bupivacaine 0.125% for intrapartum breakthrough pain. The analgesic efficacy and hemodynamic side effects did not significantly differ.

Clonidine versus sufentanil as an adjuvant to ropivacaine in patient-controlled epidural labour analgesia: A randomised double-blind trial

BACKGROUND

Adjuvants to local anaesthetics for epidural labour analgesia are useful if they reduce side-effects or personnel requirements. Epidural clonidine improves analgesia and provides a significant local anaesthetic-sparing effect.

OBJECTIVE

To compare the number of rescue doses administered by the anaesthesiologist when clonidine or sufentanil is added to epidural ropivacaine.

DESIGN

A randomised double-blind trial.

SETTING

Cliniques Universitaires Saint-Luc, Université Catholique de Louvain, Brussels, Belgium, from June 2009 to June 2010.

PATIENTS

One hundred and ninety-five women in labour.

INTERVENTION

Epidural analgesia initiated with 10 ml ropivacaine 0.1%, women randomised to receive patient-controlled epidural analgesia (5 ml demand bolus, 15 min lockout) with ropivacaine 0.1% and sufentanil 0.25 μg ml⁻¹ (RS group; n = 65), or ropivacaine 0.1% and clonidine 1.5 μg ml⁻¹ (RC1.5 group; n = 65) or ropivacaine 0.1% and clonidine 3 μg ml⁻¹ (RC3 group; n = 65). Rescue analgesia was available as needed – 10 ml ropivacaine 0.1% (numerical rating scale <6/10) or ropivacaine 0.2% (numerical rating scale ≥6/10).

MAIN OUTCOME

Comparison of the total number of rescue doses.

RESULTS

The total number of rescue doses was similar among the groups [median (interquartile range): 1 (0 to 1) in the RC1.5 group, 1 (1 to 2) in the RC3 group and 2 (1 to 2) in the RS group; overall P = 0.056]. However, fewer patients in both the RC1.5 and RC3 groups needed two or more rescue doses (25 and 29% versus 52% in the RS group, P = 0.01). The rate of instrumental delivery was higher in both clonidine groups (13 and 12% versus 0%, P = 0.03). Nausea was significantly less frequent in both the clonidine groups. Satisfaction scores, total ropivacaine consumption, maternal sedation, and hypotension and neonatal outcomes were similar among the groups.

CONCLUSION

Compared with sufentanil 0.25 μg ml⁻¹, addition of clonidine (1.5 to 3 μg ml⁻¹) to patient-controlled epidural analgesia with ropivacaine 0.1% provided similar labour analgesia and a similar need for anaesthesiologist-administered rescue doses. Clonidine 3 μg ml⁻¹ did not offer any advantage over clonidine 1.5 μg ml⁻¹. The instrumentation rate was higher in both the clonidine groups.

Labour analgesia: Recent advances

Advances in the field of labour analgesia have tread a long journey from the days of ether and chloroform in 1847 to the present day practice of comprehensive programme of labour pain management using evidence-based medicine. Newer advances include introduction of newer techniques like combined spinal epidurals, low-dose epidurals facilitating ambulation, pharmacological advances like introduction of remifentanil for patient-controlled intravenous analgesia, introduction of newer local anaesthetics and adjuvants like ropivacaine, levobupivacaine, sufentanil, clonidine and neostigmine, use of inhalational agents like sevoflourane for patient-controlled inhalational analgesia using special vaporizers, all have revolutionized the practice of pain management in labouring parturients. Technological advances like use of ultrasound to localize epidural space in difficult cases minimizes failed epidurals and introduction of novel drug delivery modalities like patient-controlled epidural analgesia (PCEA) pumps and computer-integrated drug delivery pumps have improved the overall maternal satisfaction rate and have enabled us to customize a suitable analgesic regimen for each parturient. Recent randomized controlled trials and Cochrane studies have concluded that the association of epidurals with increased caesarean section and long-term backache remains only a myth. Studies have also shown that the newer, low-dose regimes do not have a statistically significant impact on the duration of labour and breast feeding and also that these reduce the instrumental delivery rates thus improving maternal and foetal safety. Advances in medical technology like use of ultrasound for localizing epidural space have helped the clinicians to minimize the failure rates, and many novel drug delivery modalities like PCEA and computer-integrated PCEA have contributed to the overall maternal satisfaction and safety.