Intrathecal fentanyl-induced pruritus during labour: the effect of prophylactic ondansetron

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.

A biased coin up-and-down sequential allocation trial to determine the ED90 of intrathecal sufentanil combined with ropivacaine 2.5 mg for labor analgesia

Purpose

To determine the 90 percent effective dose (ED90) of intrathecal sufentanil combined with ropivacaine 2.5 mg for labor analgesia and observe its safety for parturients and neonates.

Methods

We conducted a prospective, double-blind, biased coin up-and-down study. We injected a fixed 2.5 mg ropivacaine combined with a designated dose of sufentanil intrathecally to observe the labor analgesic effect. The initial dose of sufentanil was assigned 1.0 μg, and the remaining doses were assigned as per the biased coin up-and-down method. The criterion of successful response was defined as VAS ≤ 30 mm after intrathecal injection at 10 min. Safety was evaluated in terms of maternal and neonatal outcomes.

Results

The ED90 dose of intrathecal sufentanil combined with ropivacaine 2.5 mg (0.1%, 2.5 mL) was 2.61 μg (95% CI, 2.44 to 2.70 μg) by isotonic regression. No respiratory depression, hypotension, or motor block was observed. Thirty-one (77.5%) parturients complained of pruritus, and 14 (35.0%) suffered nausea and vomiting. Three neonates reported a 1 min Apgar score of ≤7, and none reported a 5 min Apgar score of ≤7.

Conclusion

The ED90 of intrathecal sufentanil combined with ropivacaine 2.5 mg for labor analgesia was 2.61 μg. The dose is safe for parturients and neonates.

Evaluation of Therapies for Peripheral and Neuraxial Opioid-induced Pruritus based on Molecular and Cellular Discoveries

Opioids are a mainstay of treatment for pain worldwide. Pruritus, a common side effect of opioids, is a patient dissatisfier that limits their use in many clinical settings. Both parenteral and neuraxial administration of opioids frequently evoke pruritus. The ability of opioids to suppress pain while causing itch continues to perplex clinicians and researchers alike. Several mechanisms have been proposed to explain how opioids can give rise to pruritus, but specific knowledge gaps perpetuate debate. This review summarizes the clinical burden of opioid-induced pruritus and emphasizes recent discoveries of peripheral and central mechanisms for opioid-induced pruritus, particularly with respect to scientific and conceptual advances in spinal cord circuitry and mast cell biology. The mechanisms and effectiveness of existing medications used for clinical management of pruritus will be evaluated, and we will highlight the emerging preclinical utility of selective κ-opioid receptor agonists, such as nalfurafine, for the management of opioid-induced pruritus.

Prophylactic Ondansetron for the Prevention of Intrathecal Fentanyl- or Sufentanil-Mediated Pruritus: A Meta-Analysis of Randomized Trials

BACKGROUND

Pruritus is a common side effect of intrathecal fentanyl or sufentanil that decreases patient satisfaction and may delay hospital discharge. There are conflicting reports about the efficacy of prophylactic ondansetron in reducing the incidence of pruritus. This meta-analysis aimed to assess the effect of prophylactic ondansetron on the incidence of intrathecal fentanyl- or sufentanil-mediated pruritus and the need for rescue treatment.

METHODS

A systematic search on PubMed, Medline, and the Cochrane Central Register of Controlled Trials from January 1, 1994, to January 1, 2014, was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. Randomized controlled trials evaluating the efficacy of prophylactic ondansetron on pruritus associated with intrathecal fentanyl or sufentanil were included. The primary outcome was the incidence of pruritus, and the secondary outcome was patients' need for rescue therapy. Sensitivity analyses were conducted to assess the outcomes in obstetric and nonobstetric patients and in patients who received ondansetron before or after intrathecal opioid injection. Analyses used random-effect models.

RESULTS

Six randomized controlled trials involving 555 patients were included. In the overall analysis, prophylactic ondansetron did not significantly decrease the incidence of pruritus, but there was a trend toward reduced rescue medication use (risk ratio [RR], 0.57; 95% confidence interval [CI], 0.35-0.91; I = 0%; P = 0.02). Exploratory subgroups, including nonobstetric surgery patients and patients who received ondansetron before spinal opioid administration, also suggest a trend toward less rescue medication use (RR, 0.47; 95% CI, 0.26-0.85; P = 0.01; and RR, 0.62; 95% CI, 0.38-1.00; P = 0.05).

CONCLUSIONS

IV 8 mg prophylactic ondansetron does not decrease the incidence of fentanyl- or sufentanil-mediated pruritus but may decrease the need for pruritus rescue medication, particularly in specific subgroups. Randomized trials are needed to confirm these results.

Comparison of epidural oxycodone and epidural morphine for post-caesarean section analgesia: A randomised controlled trial

Background and Aims:

Epidural morphine after caesarean section may cause moderate to severe pruritus in women. Epidural oxycodone has been shown in non-obstetric trials to reduce pruritus when compared to morphine. We hypothesised that epidural oxycodone may reduce pruritus after caesarean section.

Methods:

A randomised controlled trial was conducted in pregnant women at term who underwent caesarean section with combined spinal-epidural technique initiated with intrathecal fentanyl 15 μg. Women received either epidural morphine 3 mg or epidural oxycodone 3 mg via the epidural catheter after delivery. The primary outcome was the incidence of pruritus at 24 h after caesarean section. The secondary outcomes were the pruritus scores, treatment for post-operative nausea and vomiting (PONV), pain scores and maternal satisfaction.

Results:

One hundred women were randomised (group oxycodone O = 50, morphine M = 50). There was no difference between Group O and M in the incidence of pruritus (n [%] 28 [56%] vs. 31 [62%], P = 0.68) and the worst pruritus scores (mean [standard deviation] 2.6 (2.8) vs. 3.3 [3.1], P = 0.23), respectively. Both groups had similar pain scores at rest (2.7 [2.3] vs. 2.0 [2.7], P = 0.16) and sitting up (5.0 [2.3] vs. 4.6 [2.4], P = 0.38) at 24 h. Pruritus scores were lower at 4–8, 8–12 and 12–24 h with oxycodone, but pain scores were higher. Both groups had a similar need for treatment of PONV and maternal satisfaction with analgesia.

Conclusion:

There was no difference in the incidence of pruritus at 24 h between epidural oxycodone and morphine. However, pruritus scores were lower with oxycodone between 4 and 24 h after surgery with higher pain scores in the same period.

Neuraxial opioid-induced itch and its pharmacological antagonism

Given its profound analgesic nature, neuraxial opioids are frequently used for pain management. Unfortunately, the high incident rate of itch/pruritus after spinal administration of opioid analgesics reported in postoperative and obstetric patients greatly diminishes patient satisfaction and thus the value of the analgesics. Many endeavors to solve the mystery behind neuraxial opioid-induced itch had not been successful, as the pharmacological antagonism other than the blockade of mu opioid receptors remains elusive. Nevertheless, as the characteristics of all opioid receptor subtypes have become more understood, more studies have shed light on the potential effective treatments. This review discusses the mechanisms underlying neuraxial opioid-induced itch and compares pharmacological evidence in nonhuman primates with clinical findings across diverse drugs. Both nonhuman primate and human studies corroborate that mixed mu/kappa opioid partial agonists seem to be the most effective drugs in ameliorating neuraxial opioid-induced itch while retaining neuraxial opioid-induced analgesia.

Drug therapy for preventing post-dural puncture headache

BACKGROUND

Post-dural (post-lumbar or post-spinal) puncture headache (PDPH) is one of the most common complications of diagnostic, therapeutic or inadvertent lumbar punctures. Many drug options have been used to prevent headache in clinical practice and have also been tested in some clinical studies, but there are still some uncertainties about their clinical effectiveness.

OBJECTIVES

To assess the effectiveness and safety of drugs for preventing PDPH in adults and children.

SEARCH METHODS

The search strategy included the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library 2012, Issue 5), MEDLINE (from 1950 to May 2012), EMBASE (from 1980 to May 2012) and CINAHL (from 1982 to June 2012). There was no language restriction.

SELECTION CRITERIA

We considered randomised controlled trials (RCTs) that assessed the effectiveness of any drug used for preventing PDPH.

DATA COLLECTION AND ANALYSIS

Review authors independently selected studies, assessed risks of bias and extracted data. We estimated risk ratios (RR) for dichotomous data and mean differences (MD) for continuous outcomes. We calculated a 95% confidence interval (CI) for each RR and MD. We did not undertake meta-analysis because participants' characteristics or assessed doses of drugs were too different in the included studies. We performed an intention-to-treat (ITT) analysis.

MAIN RESULTS

We included 10 RCTs (1611 participants) in this review with a majority of women (72%), mostly parturients (women in labour) (913), after a lumbar puncture for regional anaesthesia. Drugs assessed were epidural and spinal morphine, spinal fentanyl, oral caffeine, rectal indomethacin, intravenous cosyntropin, intravenous aminophylline and intravenous dexamethasone.All the included RCTs reported data on the primary outcome, i.e. the number of participants affected by PDPH of any severity after a lumbar puncture. Epidural morphine and intravenous cosyntropin reduced the number of participants affected by PDPH of any severity after a lumbar puncture when compared to placebo. Also, intravenous aminophylline reduced the number of participants affected by PDPH of any severity after a lumbar puncture when compared to no intervention, while intravenous dexamethasone increased it. Spinal morphine increased the number of participants affected by pruritus when compared to placebo, and epidural morphine increased the number of participants affected by nausea and vomiting when compared to placebo. Oral caffeine increased the number of participants affected by insomnia when compared to placebo.The remainder of the interventions analysed did not show any relevant effect for any of the outcomes.None of the included RCTs reported the number of days that patients stayed in hospital.

AUTHORS' CONCLUSIONS

Morphine and cosyntropin have shown effectiveness for reducing the number of participants affected by PDPH of any severity after a lumbar puncture, when compared to placebo, especially in patients with high risk of PDPH, such as obstetric patients who have had an inadvertent dural puncture. Aminophylline also reduced the number of participants affected by PDPH of any severity after a lumbar puncture when compared to no intervention in patients undergoing elective caesarean section. Dexamethasone increased the risk of PDPH, after spinal anaesthesia for caesarean section, when compared to placebo. Morphine also increased the number of participants affected by adverse events (pruritus and nausea and vomiting)There is a lack of conclusive evidence for the other drugs assessed (fentanyl, caffeine, indomethacin and dexamethasone).These conclusions should be interpreted with caution, owing to the lack of information, to allow correct appraisal of risk of bias and the small sample sizes of studies.

Correlating an 11-point verbal numeric rating scale to a 4-point verbal rating scale in the measurement of pruritus

Pruritus, the subjective sensation of itch, can be a difficult symptom to assess and treat. Evaluating levels of patient discomfort across populations has proven to be challenging because of a lack of a standardized measurement tool to quantify levels of itch. The most widely used tool is the 4-point verbal rating scale (VRS-4), but others use an 11-point verbal numeric rating scale (VNRS-11). Therefore, the purpose of our study was to correlate a VNRS-11 to a VRS-4 for the assessment of pruritus. Fifty parturients were enrolled in this correlational study. Each subject's level of pruritus was measured at five specific intervals after administration of intrathecal opioids. The scales were administered one minute apart in random order. Data analysis demonstrated a strong correlation between these two scales, (r=.910 to .853) indicating that each verbal descriptor on the VRS-4 could readily be substituted with a quantifiable range on the VNRS-11.

Effect of prophylactic 5-HT3 receptor antagonists on pruritus induced by neuraxial opioids: a quantitative systematic review

Pruritus is a frequent adverse event observed after neuraxial administration of opioids. Central 5-hydroxytryptamine subtype 3 (5-HT3) receptors may be activated in this process. This systematic review aimed to evaluate the efficacy of prophylactic 5-HT3 receptor antagonists on neuraxial opioid-induced pruritus. We searched Medline, Embase, and Cochrane Collaboration Library databases. Studies were evaluated with the Oxford Validity Scale. Studies with a score of 3 or more and reporting prophylactic administration of 5-HT3 receptor antagonists vs placebo were included. Fifteen randomized double-blind controlled trials (n=1337) were selected. 5-HT3 antagonists (n=775) significantly reduced pruritus [odds ratio (OR) 0.44 (95% confidence interval, 95% CI, 0.29-0.68), P=0.0002, number-needed-to-treat (NNT) 6 (95% CI, 4-14)], the treatment request for pruritus [OR 0.58 (95% CI, 0.43-0.78), P=0.0003, NNT 10 (95% CI, 7-20)], the intensity of pruritus [weighted mean difference (WMD) -0.35 (95% CI, -0.59 to -0.10), P=0.007], the incidence and the intensity of postoperative nausea and vomiting (PONV), and the need of rescue treatment [respectively, Peto odds ratio (Peto OR) 0.43 (95% CI, 0.31-0.58), P<0.00001, NNT 7 (95% CI, 6-10); WMD -0.12 (95% CI, -0.24 to 0.00), P=0.05 and OR 0.42 (95% CI, 0.20-0.86), P=0.02, NNT 8 (95% CI, 5-35)]. However, the funnel plot was asymmetric, suggesting a risk of publication bias. 5-HT3 receptor antagonists may be an effective strategy in preventing neuraxial opioid-induced pruritus and PONV. Further large randomized controlled trials are required to confirm these findings.

Ondansetron treatment in a child presenting with chronic intractable pruritus

The case of a seven-year-old boy with chronic pruritus secondary to a giant congenital melanocytic nevus is presented. The pruritus did not respond to conventional antipruritic drug treatment, but responded to ondansetron, a selective antagonist of 5-hydroxytryptamine type 3 receptors.

Ondansetron and tropisetron do not prevent intraspinal morphine- and fentanyl-induced pruritus in elective cesarean delivery

BACKGROUND

Although intraspinal morphine has been shown to be effective in providing analgesia after cesarean delivery, pruritus as a side-effect remains a common cause of dissatisfaction. The role of ondansetron has been studied in preventing pruritus but the results have been contradictory.

METHODS

We randomized 98 parturients undergoing elective cesarean section using combined spinal-epidural anesthesia into a double-blinded trial to receive tropisetron 5 mg (T group) or ondansetron 8 mg (O group) or placebo (NaCl group) after delivery, when intrathecal morphine 160 microg and fentanyl 15 microg were used for post-operative pain control. The patients additionally received ketoprofen 300 mg per day. Post-operative itching, nausea and vomiting, sedation and need for rescue analgesics were registered every 3 h up to 24 h, and all patients were interviewed on the first post-operative day.

RESULTS

Seventy-six percent of the parturients in the placebo group, 87% in the ondansetron, and 79% in the tropisetron group had itching. The incidence of post-operative nausea and vomiting was 21%, 20% and 11% of the patients in the placebo, ondansetron and tropisetron groups, respectively. Medication for pruritus was needed by 31%, 23% and 39% of the patients in the placebo, ondansetron and tropisetron groups, respectively. In the post-operative questionnaire, the patients reported less post-operative nausea in the tropisetron group than in the placebo group (P < 0.01).

CONCLUSION

Neither ondansetron nor tropisetron prevent itching caused by intrathecal morphine with fentanyl. However, tropisetron reduced post-operative nausea.

Endogenous opiates and behavior: 2004

This paper is the 27th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning over 30 years of research. It summarizes papers published during 2004 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia; stress and social status; tolerance and dependence; learning and memory; eating and drinking; alcohol and drugs of abuse; sexual activity and hormones, pregnancy, development and endocrinology; mental illness and mood; seizures and neurologic disorders; electrical-related activity and neurophysiology; general activity and locomotion; gastrointestinal, renal and hepatic functions; cardiovascular responses; respiration and thermoregulation; and immunological responses.