Neuraxial opioid-induced pruritus: An update

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.

Prophylatic use of IV nalmefene to prevent epidural opioid-induced pruritus: A multicenter, randomized clinical trial

STUDY OBJECTIVE

The incidence of pruritus from neuraxial opioids is about 60%. Pruritus causes discomfort and decreases the quality of recovery. This randomized double-blinded clinical trial was aimed to evaluate the prophylactic effects of a single dose IV nalmefene on the incidence and severity of epidural opioid-induced pruritus within 24 h after surgeries.

DESIGN

A two-center, randomized, double blinded, controlled clinical trial.

SETTING

The study was conducted from March 2022 to February 2023 at two tertiary care hospitals in China.

PATIENTS

Patients aged between 18 and 80 years-old who underwent elective surgeries and received epidural analgesia intra- and post-operatively were screened for study enrollment. A total of 306 patients were enrolled, 302 patients underwent randomization and 296 patients were included in the final analysis.

INTERVENTIONS

The nalmefene group was prophylactically given 0.5 μg/kg nalmefene intravenously while the control group was given the same volume of saline.

MEASUREMENTS

The primary endpoint was the incidence of pruritus within 24 h after surgeries. The secondary endpoints included time of the first patient-reported pruritus, severity of pruritus after surgeries, severity of acute pain scores after surgeries and other anesthesia/analgesia related side effects.

MAIN RESULTS

Pruritus occurred in 51 of the 147 (34.69%) patients in the control group and 35 of the 149 (23.49%) patients in the nalmefene group (odds ratio, 0.58; 95% CI, 0.35 to 0.96; P = 0.034) within 24 h postoperatively. Nalmefene group demonstrated delayed onset of pruritus, reduced severity of pruritus and decreased vomiting within 24 h after surgery. There were no significant differences in postoperative analgesia and the incidence of other anesthesia/analgesia associated side effects.

CONCLUSIONS

A single dose of 0.5 μg/kg nalmefene intravenously significantly reduced the incidence and severity of epidural-opioid induced pruritus within 24 h after surgery without affecting the efficacy of epidural analgesia.

TRIAL REGISTRATION

Chinese Clinical Trial Registry (www.chictr.org.cn) and the registration number is ChiCTR2100050463. Registered on August 27th, 2021.

Comparison of the ED50 of prophylactic butorphanol in preventing morphine-induced pruritus with or without palonosetron: a prospective, double-blinded, randomized dose-response trial using an up-down sequential allocation method

BACKGROUND

Butorphanol has been used to reduce the incidence and severity of neuraxial morphine-induced pruritus. Palonosetron is a commonly used antiemetic for the prevention of postoperative nausea and vomiting. The aim of our study was to compare the effective dose in 50% of subjects (ED50) of intravenous butorphanol infusion with or without a single intravenous bolus of palonosetron for preventing pruritus induced by epidural administration of morphine.

METHODS

A total of 120 parturients were randomly assigned to receive an intravenous bolus injection of palonosetron plus continuous infusion of butorphanol (Group P + B) or an intravenous bolus of saline plus continuous infusion of butorphanol (Group B) after epidural administration of morphine. The antipruritic effect was graded as satisfactory (numerical rating scale (NRS) of pruritus ≤3) or unsatisfactory (NRS >3) within 48 h after morphine treatment. The first patient in each group received butorphanol infusion at a rate of 4 µg/kg/h. The infusion dose for each subsequent patient in the corresponding group was increased by 0.2 µg/kg/h after an unsatisfactory response or decreased by 0.2 µg/kg/h after a satisfactory response. The ED50 was calculated for each group and compared using up-down sequential analysis.

RESULTS

The ED50 (mean [95% confidence interval (CI)]) of the dose of intravenous butorphanol infusion for preventing moderate to severe pruritus was lower in Group P + B (3.29 µg/kg/min [3.25-3.34 µg/kg/min]) than in Group B (3.57 µg/kg/min [3.47-3.67 µg/kg/min]) (p < 0.05).

CONCLUSIONS

Under the conditions of the present study, a prophylactic use of 0.25 mg palonosetron reduced the ED50 of prophylactic infusion of butorphanol by approximately 8% to achieve a satisfactory antipruritic effect after epidural morphine for post-caesarean analgesia.

Ondansetron for the Prevention of Pruritus in Women Undergoing Cesarean Delivery With Intrathecal Opioid: A Systematic Review and Meta-Analysis

BACKGROUND

Pruritus is a frequently reported and unpleasant side effect following intrathecal opioid use with frequency further increased among parturients. We have performed a systematic review to assess the overall efficacy of ondansetron for the prevention of pruritus in patients receiving intrathecal opioid as part of spinal anesthesia for cesarean delivery.

METHODS

A literature search of MEDLINE, Embase, Cochrane, and Web of Science databases was conducted from date of inception to September 2022. Studies that included patients undergoing cesarean delivery with spinal anesthesia using intrathecal opioid were included. The primary outcome was the presence of pruritus, and the secondary outcome was time to onset of pruritus. Data from included studies were pooled for analysis using an appropriately determined random-effects model. Outcomes were presented using forest plots and 95% confidence intervals. Additional sensitivity and subgroup analysis were performed. Trial sequential analysis was conducted for the primary outcome.

RESULTS

Twenty-three randomized controlled trials with a total of 2586 patients were included: 1219 received ondansetron, 1030 received a placebo, and a further 337 received a different study drug and were excluded from analysis. Opioids used in the included studies were morphine, fentanyl, and sufentanil. Patients who received ondansetron showed a significant reduction in the incidence of pruritus compared to the control group (RR, 0.81; 95% confidence interval [CI], 0.71-0.92; I 2 = 64%). There was no significant difference in pruritus onset between the groups (mean difference [MD], 17.54 minutes; 95% CI, -2.18 to 37.26; I 2 = 83%). The overall Grading of Recommendations Assessment, Development, and Evaluation (GRADE) assessment of quality of evidence was low.

CONCLUSIONS

This systematic review has demonstrated a significant reduction in the incidence of pruritus following the use of ondansetron. This is in contrast to previously published meta-analyses. Studies included were of varying quality and some at high risk of bias with a high degree of statistical heterogeneity. Furthermore, high-quality and well-powered studies are required to confirm these findings.

Effects of oral morphine on experimentally evoked itch and pain: a randomized, double-blind, placebo-controlled trial

OBJECTIVES

Pain and itch share similar neuronal networks; hence, it is difficult to explain why opioids can relieve pain but provoke itching. The present human volunteer study aimed to investigate the similarities and differences in responses to experimentally provoked pain and itching to explore the underlying fundamental mechanisms.

METHODS

Twenty-four healthy volunteers were enrolled in this single-center, randomized, double-blind, placebo-controlled, parallel-group trial. Three volar forearms and two mandibular areas were marked, and participants randomly received morphine (20 mg) or identical placebo tablets. Heat, cold, and pressure pain thresholds, and vasomotor responses were assessed at baseline and after oral morphine administration. Itch provocations were induced by intradermal application of 1 % histamine or a topical cowhage (non-histaminergic itch) to a marked area of the skin. The participants were subsequently asked to rate their itching and pain intensities. The assessments were repeated for all marked areas.

RESULTS

Morphine caused analgesia, as assessed by the significant modulation of cold and pressure pain thresholds (p<0.05). There were no significant differences in histaminergic or non-histaminergic itch or pain intensity between the morphine and placebo groups. Superficial blood perfusion (vasomotor response) following histamine provocation was significantly increased by morphine (p<0.05) in both areas. No correlation was found between the provoked itch intensity and analgesic efficacy in any area or group.

CONCLUSIONS

Oral administration of morphine caused analgesia without modulating itch intensities but increased neurogenic inflammation in response to histamine, suggesting that different opioid mechanisms in histaminergic and non-histaminergic neurons evoke neurogenic inflammation.

Translational research updates in female health anesthesiology: a narrative review

Background and Objective

Females represent 49.6% of the global population and constitute a significant proportion of surgical patients and hospital admissions. Little is known about the bi-directional effects of sex and anesthetics or the impact of anesthetic interventions on long-term female health outcomes. Sex differences in pain pathways can influence pain experience and treatment effectiveness. The impact of anesthetic management on the recurrence of breast cancer is poorly understood, as are the long-term consequences of cardiovascular disease and safe and effective treatments in pregnancy. This review aims to outline recent advances in translational science in female health anesthesiology research and highlight critical research opportunities in pain, cancer outcomes, and cardiovascular disorders.

Methods

We searched PubMed and summarized relevant articles published in English between December 2021 and June 2022.

Key Content and Findings

Studies reveal sex differences in pain pathways and highlight the importance of sex as a biological variable in experimental designs and translational medicine. Sex differences have also been observed in side effects attributed to opioid analgesics. We summarize some of the neural circuits that might underlie these differences. In the perioperative setting, specific anesthetics are implicated in metastatic seeding potential and acute and chronic pain outcomes, suggesting the importance of anesthetic selection in comprehensive care during oncologic surgery. In the peridelivery setting, preeclampsia, a cardiovascular disorder of pregnancy, affects maternal outcomes; however, biomarkers can risk-stratify females at risk for preeclampsia and hold promise for identifying the risk of adverse neurological and other health outcomes.

Conclusions

Research that builds diagnostic and predictive tools in pain and cardiovascular disease will help anesthesiologists minimize sex-related risks and side effects associated with anesthetics and peri-hospital treatments. Sex-specific anesthesia care will improve outcomes, as will the provision of practical information to patients and clinicians about the effectiveness of therapies and behavioral interventions. However, more research studies and specific analytic plans are needed to continue addressing sex-based outcomes in anesthesiology.

STING controls opioid-induced itch and chronic itch via spinal tank-binding kinase 1-dependent type I interferon response in mice

BACKGROUND

Patients receiving epidural or intrathecal opioids administration for neuraxial analgesia frequently suffer from an irritating itch. STING (stimulator of interferon genes), an innate immune modulator, is strongly implicated in pain pathogenesis via neuron-immune modulation. Given that pain and itch share some common neurocircuits, we evaluate the therapeutic potential of STING agonists in opioid-induced itch and chronic itch.

METHODS

Opioids (morphine, fentanyl and sufentanil) were intrathecally injected to induce acute itch. Chronic itch was induced by dry skin and contact dermatitis. Opioids analgesic effect, itch-induced scratching behavior, spinal expression of STING, phosphorylation of TBK1 (tank-binding kinase 1), IRF3 (interferon regulatory factor-3) and ERK (extracellular signal-regulated kinase), as well as production of IFN-α and IFN-β were examined. STING agonists (DMXAA and ADU-S100), TBK1 inhibitor, recombinant IFN-α and IFN-β elucidated the mechanism and treatment of itch. Whole-brain functional connectivity was evaluated using resting-state fMRI.

RESULTS

We report the primary expression of STING protein by the spinal dorsal horn neurons. Intraperitoneal injection of DMXAA dose-dependently reduces morphine-induced scratch bouts, without impairing morphine antinociception. Simultaneously, DMXAA alleviates fentanyl- and sufentanil-induced itching-like behavior, and chronic scratching behavior caused by dry skin and contact dermatitis. Furthermore, DMXAA drastically increases spinal phosphorylation of TBK1 and IRF3 following morphine exposure, dry skin and contact dermatitis. DMXAA-induced anti-pruritus effects and spinal productions of IFN-α and IFN-β are compensated by intrathecal delivery of the TBK1 inhibitor. Also, ADU-S100, recombinant IFN-α and IFN-β exhibits remarkable attenuation in scratching behaviors after morphine injection and dermatitis. Recombinant IFN-α inhibits morphine-induced spinal phosphorylation of ERK. Finally, DMXAA prevents dermatitis-induced the increase of cerebral functional connectivity between regions of interests such as primary somatosensory cortex, piriform cortex, retrosplenial cortex, colliculus and ventral thalamus.

CONCLUSIONS

STING activation confers protection against opioid-induced itch and chronic itch through spinal up-regulation of TBK1-IRF3-type I interferon cascades in mice, suggesting that STING agonists are promising candidates in translational development for pruritus relief.

Endogenous Opioid Imbalance as a Potential Factor Involved in the Pathogenesis of Chronic Kidney Disease-Associated Pruritus in Dialysis Patients

Chronic pruritus is one of the most common symptoms of dermatological diseases. It may occur in the course of other disorders, such as kidney disease. Chronic kidney disease-associated pruritus (CKD-aP) most often affects people with end-stage renal disease. The etiology of this condition is still not fully understood, but researchers are currently focusing on a thorough analysis of the association between disturbed opioid balance and increased neuronal signaling leading to pruritus. The aim of this study is to assess the concentration of endogenous opioids in dialysis patients with and without pruritus and in the control group, and to determine the correlation between the concentration of these substances and the occurrence and severity of itching. The study involved 126 dialysis patients and 50 healthy controls. Patients were divided into groups with pruritus (n = 62) and without pruritus (n = 64). The severity of pruritus was assessed using the NRS scale. The concentration of endogenous opioids was determined using the ELISA. The concentration of met-enkephalin was higher in the group of patients with pruritus compared to the control group. Moreover, significantly lower levels of β-endorphin and dynorphin A were observed in the group of dialysis patients compared to the control group. In addition, a statistically significant difference was seen between the β-endorphin concentration in the group of dialysis patients with pruritus compared to the group without pruritus. The ratio of β-endorphin/dynorphin A concentrations was significantly lower in the group of patients with pruritus compared to patients without pruritus and the control group. No correlations were found between serum level of studied opioids and the severity of pruritus. The concentrations of the studied opioids did not correlate with the severity of pruritus. Observed opioid imbalance may affect the occurrence of CKD-aP in dialysis patients, but a thorough understanding of the mechanism of action of these substances in the sensation of pruritus is necessary to assess the possibility of finding a new therapeutic target.

Opioid toxicity: histamine, hypersensitivity, and MRGPRX2

Insights into the pathophysiology of many non-immune-mediated drug reactions referred to as toxicities, sensitivities, intolerances, or pseudoallergies have resulted from research identifying the mastocyte-related G-protein-coupled receptor (GPCR) member X2 (MRGPRX2), a human mast cell receptor mediating adverse reactions without the involvement of antibody priming. Opioid-induced degranulation of mast cells, particularly morphine, provoking release of histamine and other preformed mediators and causing hemodynamic and cutaneous changes seen as flushing, headache and wheal and flare reactions in the skin, is an example of results of MRGPRX2 activation. Opioids including morphine, codeine, dextromethorphan and metazocine as well as endogenous prodynorphin opioid peptides activate MRGPRX2 at concentrations causing mast cell degranulation. Unlike the canonical opioid receptors, MRGPRX2 shows stereochemical recognition preference for dextro rather than levo opioid enantiomers. Opioid analgesic drugs (OADs) display a range of histamine-releasing potencies from the strong releaser morphine to doubtful releasers like hydromorphone and the non-releaser fentanyl. Whether there is a correlation between histamine release by individual OADs, MRGPRX2 activation, and presence or absence of adverse cutaneous effects is not known. To investigate the question, ongoing research with recently pursued methodologies and strategies employing basophil and mast cell tests resulting from MRGPRX2 insights should help to elucidate whether or not an opioid's histamine-releasing potency, and its property of provoking an adverse reaction, are each a reflection of its activation of MRGPRX2.

Uremic pruritus: pathophysiology, clinical presentation, and treatments

Uremic pruritus is one of the most common and bothersome symptoms in patients with end-stage renal disease. Most patients with uremic pruritus experience a prolonged and relapsing course and significant impairments of quality of life. The pathophysiology of uremic pruritus is not completely understood. A complex interplay among cutaneous biology and the nervous and immune systems has been implicated, with the involvement of various inflammatory mediators, neurotransmitters, and opioids. Uremic pruritus treatment outcomes are often unsatisfactory. Clinical trials have mostly been small in scale and have reported inconsistent results. Recent evidence shows that gabapentinoids, nalfurafine, and difelikefalin are effective for relieving uremic pruritus in hemodialysis patients. This review provides an overview of the epidemiology and proposed mechanisms of uremic pruritus, then highlights the manifestations of and clinical approach to uremic pruritus. Current evidence regarding treatment options, including topical treatments, treatment of underlying disease, phototherapy, and systemic treatments, is also outlined. With a better understanding of uremic pruritus, more therapeutic options can be expected in the near future.

Caudal epidural catheterization for pain management in 48 hospitalized horses: A descriptive study of demographics, complications, and outcomes

The placement of caudal epidural catheters in horses has become more frequent as a multi-modal analgesic strategy. Despite its integration into clinical practice, there are limited reports describing the use of caudal epidural catheterization for prolonged use in horses. The purpose of this study was to characterize the hospitalized caseload undergoing epidural catheterization for long-term epidural analgesic administration, to report the response to epidural therapy and observed complications, and to describe patient outcomes. Medical records of hospitalized equine patients that underwent placement of a caudal epidural catheter for analgesic management between 2017 and 2021 were analyzed retrospectively. For the 62 catheters placed in the 48 cases, the most frequent diagnosis category prompting epidural analgesia was orthopedic (43/48, 89.6%). Synovial sepsis was the most frequent specific diagnosis prompting epidural catheter placement (11/48, 22.9%). The initial response to epidural therapy was characterized as positive for 37/62 (59.7%) catheters. Complications were documented for 46/62 (74.2%) catheters. However, most of these complications were classified as mild (51.6%) or moderate (14.5%), and exaggerated physiologic responses were observed most frequently. Of the horses studied, 52.1% survived to be discharged from the hospital. With awareness of potential complications and vigilant monitoring, caudal epidural catheters should be considered for equine patients as an analgesic strategy.

Pruritus, neuraxial morphine and recrudescence of oral herpes simplex and treatment: an educational review in obstetric patients

Neuraxial opioids are well known to cause itching, which may be challenging to treat. Neuraxial morphine has been demonstrated to cause recrudescent herpes simplex viruses (HSV-1), especially in women during labor and childbirth with neuraxial analgesia, and may be an occult etiology of refractory itching. This educational review summaries the clinical and epidemiological characteristics associated with recrudescent HSV-1 in patients treated with neuraxial opioids, especially morphine.

Neuraxial labor analgesia: Maintenance techniques

Since the advent of neuraxial analgesia for labor, approaches to maintaining intrapartum pain relief have seen significant advancement. Through pharmacologic innovations and improved drug delivery mechanisms, current neuraxial labor analgesia maintenance techniques have been shaped by efforts to maximize patient comfort during the birthing process, while minimizing undesirable side effects and promoting the unimpeded progress of labor. To these ends, a modern anesthesiologist may avail themselves of several techniques, including programmed intermittent epidural bolus (PIEB), patient controlled epidural analgesia (PCEA) and dilute concentration local anesthetic + opioid epidural solutions. We explore the historical development and the evidential underpinnings of these techniques, in addition to several contemporary neuraxial labor analgesia practices. We also summarize current understanding of the effects these interventions have on maternal/fetal health and the labor course, as well as several important aspects of analgesic safety and monitoring.

A Randomized Controlled Trial for Prevention of Postspinal Anesthesia Shivering in Gynecological Surgeries: Mirtazapine vs. Dexamethasone

Background

The frequency of shivering regarding regional anesthesia is 55%. Newer effective and tolerable options for postspinal anesthesia shivering (PSAS) prophylaxis are necessary to improve patients' quality of care. This research assessed the impact of preemptive mirtazapine versus preemptive dexamethasone to decrease frequency and severity of PSAS in gynecological procedures.

Methods

300 patients booked for gynecological procedures under spinal anesthesia (SA) were randomly apportioned into three groups (100 each) to get one preemptive dose of 30 mg mirtazapine tablet (M group), 8 mg dexamethasone diluted in 100 ml of saline infusion (D group) or placebo (C group) two hours before surgery. Incidence of clinically significant PSAS was the primary outcome. Core temperature, shivering score, hemodynamics changes, adverse events, and patient satisfaction score were documented as secondary outcomes.

Results

Compared with C group, mirtazapine and dexamethasone decreased incidence of clinically significant shivering (74% vs. 16% and 31%, respectively; P < 0.001). M and D groups had less hypotensive episodes during 5–25 min after intrathecal injection (P < 0.001). 90 min after SA, tympanic temperatures were lower than baseline values in the three groups (P < 0.001). Pruritus, nausea, and vomiting were more often in C group (P < 0.001), whereas sedation was more frequent in M group (P < 0.001). C group had the lowest satisfaction scores (P < 0.001).

Conclusion

Prophylactic administration of mirtazapine or dexamethasone attenuated shivering with minimal hazards in patients scheduled for gynecological surgeries under spinal anesthesia with priority to mirtazapine. The trial is registered with NCT03675555.

Mas-Related G Protein–Coupled Receptor-X2 and Its Role in Non-immunoglobulin E–Mediated Drug Hypersensitivity

A diverse group of Food and Drug Administration-approved cationic drugs including antibiotics, neuromuscular blocking drugs, opioids, antidepressants, and radiocontrast media activate mast cells and cause hypersensitivity reactions by both an immunoglobulin E IgE-dependent and independent manner. The recent discovery that these drugs activate mast cells via the G protein-coupled receptor known as Mas-related GPCR-X2 (MRGPRX2) has represented a paradigm shift of how drug hypersensitivity reactions are viewed. This article provides an overview of the current status of the role of MRGPRX2 on non-IgE-mediated drug hypersensitivity. Potential risk factors and evaluation for suspected MRGPRX2-mediated drug reactions are also discussed.

The Incidence of Itching in Thoracic Epidural Morphine Applications: Can Laboratory Parameters Be Effective in Predicting Itching?

Background

Epidural morphine, a powerful analgesic, also causes significant itching in patients. This study aimed to determine the incidence of thoracic epidural morphine-induced pruritus (EMIP) after thoracotomy and to investigate preoperative laboratory parameters for predicting itching in patients who received thoracic epidural morphine (TEM).

Methods

The patients were divided into two groups. The itching (+) group consists of patients who developed itching (n=31). The no-itching (-) / control group (n=31) was selected among patients who did not develop itching after TEM. Preoperative hemogram values, neutrophil/lymphocyte rate (NLR), platelet/lymphocyte rate (PLR), lymphocyte/monocytes rate (LMR), preoperative and postoperative alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase (ALP), gamma-glutamyl transferase values, and whether there was itching in the first 48 hours after surgery were determined.

Results

The incidence of thoracic EMIP after thoracotomy was 7.9%. While preoperative and postoperative ALP was found to be lower in patients with itching compared to those without itching. The cut-off value for preoperative/postoperative ALP was 84.5/53. Decreased white blood cell (WBC) could predict pruritus with a borderline statistical significance.

Conclusions

The incidence of EMIP after thoracotomy was lower compared to other literature data. Infusion of morphine only into the epidural area may cause a low incidence of EMIP. Laboratory parameters ALP and WBC can predict EMIP, but other hemogram parameters, NLR, LMR, and PLR cannot predict EMIP.

Chronic Intractable Pruritus in Chronic Kidney Disease Patients: Prevalence, Impact, and Management Challenges - A Narrative Review

Chronic kidney disease (CKD) is recognized as a leading public health problem and causes numerous health complications. One of the most common and burdensome dermatological symptoms affecting patients undergoing dialysis is CKD-associated pruritus (CKD-aP). This condition not only has a negative impact on sleep, mood, daily activities, and quality of life but also increases the mortality risk of hemodialyzed patients. Despite that, this condition is greatly underestimated in clinical practice. Due to the complex and still not fully understood etiopathogenesis of CKD-aP, the choice of an effective therapy remains a challenge for clinicians. Most common therapeutic algorithms use topical treatment, phototherapy, and various systemic approaches. This review aimed to summarize most recent theories about the pathogenesis, clinical features, and treatment of CKD-aP.

Influence of Catheter-Incision Congruency in Epidural Analgesia on Postcesarean Pain Management: A Single-Blinded Randomized Controlled Trial

Patient-controlled epidural analgesia (PCEA) or epidural morphine may alleviate postcesarean pain; however, conventional lumbar epidural insertion is catheter–incision incongruent for cesarean delivery. Methods: In total, 189 women who underwent cesarean delivery were randomly divided into four groups (low thoracic PCEA, lumbar PCEA, low thoracic morphine, and lumbar morphine groups) for postcesarean pain management. Pain intensities, including static pain, dynamic pain, and uterine cramp, were measured using a 100 mm visual analog scale (VAS). The proportion of participants who experienced dynamic wound pain with a VAS score of >33 mm was evaluated as the primary outcome. Adverse effects, including lower extremity blockade, pruritus, postoperative nausea and vomiting, sedation, and time of first passage of flatulence, were evaluated. Results: The low thoracic PCEA group had the lowest proportion of participants reporting dynamic pain at 6 h after spinal anesthesia (low thoracic PCEA, 28.8%; lumbar PCEA, 69.4%; low thoracic morphine, 67.3%; lumbar morphine group, 73.9%; p < 0.001). The aforementioned group also reported the most favorable VAS scores for static, dynamic, and uterine cramp pain during the first 24 h after surgery. Adverse effect profiles were similar among the four groups, but a higher proportion of participants in the lumbar PCEA group (approximately 20% more than in the other three groups) reported prolonged postoperative lower extremity motor blockade (p = 0.005). In addition, the first passage of flatulence after surgery reported by the low thoracic PCEA group was approximately 8 h earlier than that of the two morphine groups (p < 0.001). Conclusions: Epidural congruency is essential to PCEA for postcesarean pain. Low thoracic PCEA achieves favorable analgesic effects and may promote postoperative gastrointestinal recovery without additional adverse effects.

MRGPRX2 and Adverse Drug Reactions

Many adverse reactions to therapeutic drugs appear to be allergic in nature, and are thought to be triggered by patient-specific Immunoglobulin E (IgE) antibodies that recognize the drug molecules and form complexes with them that activate mast cells. However, in recent years another mechanism has been proposed, in which some drugs closely associated with allergic-type events can bypass the antibody-mediated pathway and trigger mast cell degranulation directly by activating a mast cell-specific receptor called Mas-related G protein-coupled receptor X2 (MRGPRX2). This would result in symptoms similar to IgE-mediated events, but would not require immune priming. This review will cover the frequency, severity, and dose-responsiveness of allergic-type events for several drugs shown to have MRGPRX2 agonist activity. Surprisingly, the analysis shows that mild-to-moderate events are far more common than currently appreciated. A comparison with plasma drug levels suggests that MRGPRX2 mediates many of these mild-to-moderate events. For some of these drugs, then, MRGPRX2 activation may be considered a regular and predictable feature after administration of high doses.

Characterization of Hyperacute Neuropathic Pain after Spinal Cord Injury: A Prospective Study

There is currently a lack of information regarding neuropathic pain in the very early stages of spinal cord injury (SCI). In the present study, neuropathic pain was assessed using the Douleur Neuropathique 4 Questions (DN4) for the patient's worst pain within the first 5 days of injury (i.e., hyperacute) and on follow-up at 3, 6, and 12 months. Within the hyperacute time frame (i.e., 5 days), at- and below-level neuropathic pain were reported as the worst pain in 23% (n = 18) and 5% (n = 4) of individuals with SCI, respectively. Compared to the neuropathic pain observed in this hyperacute setting, late presenting neuropathic pain was characterized by more intense painful electrical and cold sensations, but less itching sensations. Phenotypic differences between acute and late neuropathic pain support the incorporation of timing into a mechanism-based classification of neuropathic pain after SCI. The diagnosis of acute neuropathic pain after SCI is challenged by the presence of nociceptive and neuropathic pains, with the former potentially masking the latter. This may lead to an underestimation of the incidence of neuropathic pain during the very early, hyperacute time points post-injury. TRIAL REGISTRATION: ClinicalTrials.gov (Identifier: NCT01279811) PERSPECTIVE: This article presents distinct pain phenotypes of hyperacute and late presenting neuropathic pain after spinal cord injury and highlights the challenges of pain assessments in the acute phase after injury. This information may be relevant to clinical trial design and broaden our understanding of neuropathic pain mechanisms after spinal cord injury.

[Neuraxial Morphine for Postoperative Analgesia after Caesarean Deliveries]

The use of neuraxial morphine, in combination with nonopioid analgesic regimens for postoperative analgesia after Caesarean deliveries is common practice, especially in the Anglo-American world. Neuraxial morphine offers a longer-lasting superior analgesia than intravenous opioids or patient-controlled analgesia. If neuraxial anaesthesia is being used for a caesarean delivery, it may be recommended to concomitantly administer neuraxial morphine for the postoperative analgesia.A low dose of neuraxial morphine in a healthy parturient bears a low morbidity and mortality risk. The optimal frequency, duration and modality of respiratory monitoring for patients at low risk for respiratory depression is dependent on the dose of morphine administered and the patient-specific and obstetric risk profile.

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.

Assessment of main complications of regional anesthesia recorded in an acute pain unit in a tertiary care university hospital: a retrospective cohort

Background

Regional anesthesia has been increasingly used. Despite its low number of complications, they are associated with relevant morbidity. This study aims to evaluate the incidence of complications after neuraxial block and peripheral nerve block.

Methods

A retrospective cohort study was conducted, and data related to patients submitted to neuraxial block and peripheral nerve block at a tertiary university hospital from January 1, 2011 to December 31, 2017 were analyzed.

Results

From 10,838 patients referred to Acute Pain Unit, 1093(10.1%) had side effects or complications: 1039 (11.4%) submitted to neuraxial block and 54 (5.2%) to peripheral nerve block. The most common side effects after neuraxial block were sensory (48.5%) or motor deficits (11.8%), nausea or vomiting (17.5%) and pruritus (8.0%); The most common complications: 3 (0.03%) subcutaneous cell tissue hematoma, 3 (0.03%) epidural abscesses and 1 (0.01%) arachnoiditis. 204 of these patients presented sensory or motor deficits at hospital discharge and needed follow-up. Permanent peripheral nerve injury after neuraxial block had an incidence of 7.7:10,000 (0.08%). The most common side effects after peripheral nerve block were sensory deficits (52%) and 21 patients maintained follow-up due to symptoms persistence after hospital discharge.

Conclusion

Although we found similar incidences of side effects or even lower than those described, major complications after neuraxial block had a higher incidence, particularly epidural abscesses. Despite this, other serious complications, such as spinal hematoma and permanent peripheral nerve injury, are still rare.

Patient-controlled epidural analgesia, patient-controlled intravenous analgesia, and conventional intravenous opioids for gynecologic interstitial brachytherapy: A single-center retrospective study

PURPOSE Interstitial brachytherapy for gynecologic malignancies is stressful physically and mentally; however, optimal analgesic methods remain unclear. We investigated the effect of analgesic methods on pain and adverse events during interstitial brachytherapy for gynecologic malignancies. METHODS The data of 73 patients who underwent interstitial brachytherapy for gynecologic malignancies between April 2015 and March 2020 were retrospectively analyzed. Patient-controlled epidural analgesia (PCEA), patient-controlled intravenous analgesia (PCIA), and conventional intravenous opioid administration were used for analgesia during treatment. We compared the analgesic effects based on a numerical rating scale (NRS), the number of additional analgesics, and the adverse events associated with analgesia. The NRS score was calculated as an average value for every 12 h (NRS1: treatment on the 1st day from 12 to 24 o'clock; NRS2: treatment on the 2nd day from 0 to 12 o'clock; NRS3: treatment on the 2nd day from 12 to 24 o'clock). The mean NRS score differences between the methods were evaluated using mixed models for repeated-measures analyses. RESULTS The NRS score was significantly lower at all times for PCEA (NRS1: p = 0.003; NRS2: p = 0.011; NRS3: p < 0.001). NRS2 and NRS3 were significantly lower for PCIA (NRS2: p = 0.043; NRS3: p < 0.001) than for the conventional method. The NRS scores for PCEA and PCIA were not significantly different. Moreover, additional analgesics and adverse events did not differ between the three treatments. CONCLUSION PCEA and PCIA were superior to conventional intravenous opioids for analgesia in interstitial brachytherapy for gynecologic malignancies. However, adverse events associated with PCEA and PCIA were not reduced.

Central opioid receptors mediate morphine-induced itch and chronic itch via disinhibition

Opioids such as morphine are mainstay treatments for clinical pain conditions. Itch is a common side effect of opioids, particularly as a result of epidural or intrathecal administration. Recent progress has advanced our understanding of itch circuits in the spinal cord. However, the mechanisms underlying opioid-induced itch are not fully understood, although an interaction between µ-opioid receptor (MOR) and gastrin-releasing peptide receptor (GRPR) in spinal GRPR-expressing neurons has been implicated. In this study we investigated the cellular mechanisms of intrathecal opioid-induced itch by conditional deletion of MOR-encoding Oprm1 in distinct populations of interneurons and sensory neurons. We found that intrathecal injection of the MOR agonists morphine or DAMGO elicited dose-dependent scratching as well as licking and biting, but this pruritus was totally abolished in mice with a specific Oprm1 deletion in Vgat+ neurons [Oprm1-Vgat (Slc32a1)]. Loss of MOR in somatostatin+ interneurons and TRPV1+ sensory neurons did not affect morphine-induced itch but impaired morphine-induced antinociception. In situ hybridization revealed Oprm1 expression in 30% of inhibitory and 20% of excitatory interneurons in the spinal dorsal horn. Whole-cell recordings from spinal cord slices showed that DAMGO induced outward currents in 9 of 19 Vgat+ interneurons examined. Morphine also inhibited action potentials in Vgat+ interneurons. Furthermore, morphine suppressed evoked inhibitory postsynaptic currents in postsynaptic Vgat- excitatory neurons, suggesting a mechanism of disinhibition by MOR agonists. Notably, morphine-elicited itch was suppressed by intrathecal administration of NPY and abolished by spinal ablation of GRPR+ neurons with intrathecal injection of bombesin-saporin, whereas intrathecal GRP-induced itch response remained intact in mice lacking Oprm1-Vgat. Intrathecal bombesin-saporin treatment reduced the number of GRPR+ neurons by 97% in the lumber spinal cord and 91% in the cervical spinal cord, without changing the number of Oprm1+ neurons. Additionally, chronic itch from DNFB-induced allergic contact dermatitis was decreased by Oprm1-Vgat deletion. Finally, naloxone, but not peripherally restricted naloxone methiodide, inhibited chronic itch in the DNFB model and the CTCL model, indicating a contribution of central MOR signalling to chronic itch. Our findings demonstrate that intrathecal morphine elicits itch via acting on MOR on spinal inhibitory interneurons, leading to disinhibition of the spinal itch circuit. Our data also provide mechanistic insights into the current treatment of chronic itch with opioid receptor antagonist such as naloxone.

Ondansetron versus ondansetron with dexamethasone to prevent intrathecal-morphine pruritus for caesarean patients: randomised double-blind trial

The objective of this randomised, double blinded clinical trial was to evaluate the efficacy of prophylactic administration of 4 mg ondansetron as monotherapy versus combination therapy of 4 mg ondansetron plus 8 mg dexamethasone for the prevention of intrathecal morphine-associated pruritus in caesarean section within 24 h. A total of 194 patients were included, 96 patients in the monotherapy group and 98 in the combination group. One hour after the operation, 11.5% of patients in ondansetron group had failure of prophylaxis for pruritus compared to 13.5% of patients in the combination group (p = .66). This decreased throughout the follow-up to reach 0.0% and 1.0% at 24 h in the ondansetron vs. the combination groups respectively. There was no superiority of combining ondansetron with dexamethasone over the use of ondansetron as prophylactic antipruritic in parturients receiving intrathecal morphine for caesarean section.IMPACT STATEMENTWhat is already known on this subject? The incidence of pruritus has been reported to be between 36% and 60% in patients undergoing caesarean section with intrathecal morphine. Ondansetron has been identified as possible antipruritic agent while the antipruritic effect of dexamethasone is inconclusive.What do the results of this study add? The study demonstrated that there was no superiority of combining ondansetron with dexamethasone over the use of ondansetron as prophylactic antipruritic in parturients receiving intrathecal morphine for caesarean section. Moreover, it seems that there is no effect of combining ondansetron with dexamethasone over ondansetron alone on antiemetic consequences.What are the implications of these findings for clinical practice and/or further research? Ondansetron could be an effective antipruritic if used solely for patients undergoing caesarean section.

Morphine acts on spinal dynorphin neurons to cause itch through disinhibition

Morphine-induced itch is a very common and debilitating side effect that occurs in laboring women who receive epidural analgesia and in patients who receive spinal morphine for relief of perioperative pain. Although antihistamines are still widely prescribed for the treatment of morphine-induced itch, their use is controversial because the cellular basis for morphine-induced itch remains unclear. Here, we used animal models and show that neuraxial morphine causes itch through neurons and not mast cells. In particular, we found that spinal dynorphin (Pdyn) neurons are both necessary and sufficient for morphine-induced itch in mice. Agonism of the kappa-opioid receptor alleviated morphine-induced itch in mice and nonhuman primates. Thus, our findings not only reveal that morphine causes itch through a mechanism of disinhibition but also challenge the long-standing use of antihistamines, thereby informing the treatment of millions worldwide.

Pruritus after continuous administration of epidural morphine for post-cesarean delivery analgesia: a case control study

Background

Pruritus is one of the most common side effects of epidural morphine administered for post-surgery analgesia, and pregnant women tend to be highly susceptible. The relative contributions of morphine concentration, local anesthetics, and level of pain to pruritus after epidural morphine for post-cesarean delivery analgesia remain unclear. Accordingly, the present study aimed to identify risk factors for pruritus after continuous administration of epidural morphine for post-cesarean delivery analgesia.

Methods

This case control study was based on routinely collected clinical data. Participants included women who had undergone cesarean section and adopted a patient-controlled analgesia pump for postoperative analgesia. A series of logistic regression analyses were performed. Interaction terms were added to explore the moderation effects of combined local anesthetics and pain level on associations between morphine concentration and pruritus. Robustness of the results was checked through sensitivity analysis using propensity scores matching approach.

Results

Higher morphine concentration, assisted reproductive treatment, and multipara and cesarean section history were significantly more prevalent in the pruritus group than in the control group. The probabilities of pruritus at morphine concentrations of 10, 15, 20, 25, 30 and 40 μg/mL increased sequentially from 0.05, 0.1, 0.2, 0.35, 0.54 to 0.84, respectively. The trend remained steep in the ropivacaine stratum and became flatter when combined with levobupivacaine. At mild pain combined with levobupivacaine, the incidence of pruritus increased from 0.33 (95% confidence interval [CI] 0.1–0.68) in the 10 μg/mL morphine group to 0.48 (95% CI 0.1–0.88) in the 40 μg/mL morphine group. In the stratum of moderate pain combined with levobupivacaine, the incidence increased from 0.4 (95% CI 0.04–0.92) to 0.56 (95% CI 0.03–0.98). The results in the sensitivity analysis were in consistent with above findings.

Conclusions

Higher concentrations of morphine, multipara, and assisted reproductive treatment were factors associated with a higher probability of pruritus. Pain level or combined local anesthetics could moderate the association between morphine concentration and pruritus.

Safety and efficacy of low-dose selective spinal anesthesia with bupivacaine and fentanyl as compared to intravenous sedation and port-site infiltration for outpatient laparoscopic tubal ligation: A randomized controlled trial

Background:

Selective spinal anesthesia has been safely applied for short-duration outpatient gynecological laparoscopic procedure. However, this anesthesia technique is often inadequate and not tolerated by awake patients due to pneumoperitoneum and visceral manipulation.

Aims:

We aimed to conduct a study to compare spinal anesthesia with bupivacaine, fentanyl, and i.v. sedation with i.v. sedation and laparoscopic port-site infiltration with local anaesthetic in outpatient laparoscopic tubal ligation procedures.

Settings and Design:

100 female patients posted for elective surgeries were recruited for a prospective single blind randomised control trial in a tertiary care center in two groups.

Materials and Methods:

In Group S, patients receive intrathecal 3 mg hyperbaric bupivacaine 0.5% plus 20 microgram fentanyl along with intravenous (i.v.) fentanyl at 1μg.kg^-1.h^-1 and in Group C i.v. fentanyl at 1μg.kg^-1.h^-1 along with laparoscopic port site infiltration with 0.5% bupivacaine. Postoperatively, overall patient satisfaction, visual analog score (VAS) score, duration of motor blockade, sensory blockade, and time to attain discharge criteria and any adverse.

Statistical Analysis:

Continuous variables between the groups were compared by the independent t-test and Wilcoxon rank sum. Chi-square and Fisher exact test used for the categorical value.

Results:

Overall VAS was significantly lower and patient satisfaction was higher in Group S than Group C. Time to oral intake was significantly prolonged in Group C 126.33 (±29.54) compared to group S 110.81 (±29.54). The requirement of total rescue analgesia (fentanyl) was significantly higher in Group C 2.0 (±0.6) μg.kg^-1 compared to group S 0.79 (±0.53) μg.kg^-1. Incidence of postoperative nausea vomiting (PONV) was significantly greater in Group C while incidence of pruritus was significantly greater in Group S.

Conclusion:

Low-dose intrathecal anesthesia with 3 mg bupivacaine and 20 μg fentanyl provided better analgesia, patient satisfaction and with less opioids consumption.

Inhibition of Itch by Hunger and AgRP Neuron Activity

Unpleasant somatosensory stimuli such as pain and itch can interrupt normal behavior. But survival can depend on resuming normal behavior before these challenges are fully resolved. The neural mechanisms that prioritize behavior when individuals are challenged with unpleasant somatosensory sensations, however, are not fully understood. Recently, we identified a neural circuit activated by hunger that can inhibit pain, prioritizing food seeking over tending to an injury. Here, we examine the ability of hunger, and neurons activated by hunger, to inhibit behavioral responses to another unpleasant somatosensory sensation - itch. We demonstrate that food deprivation inhibits scratching induced by three different pruritogenic stimuli: histamine, serotonin, and chloroquine. The inhibition of scratching correlates with the level of food deprivation, suggesting a cross-competition of alarm systems in the brain whereby more energy need more efficiently inhibits competing drives. Finally, we show that activity in hunger-sensitive, hypothalamic agouti-related protein (AgRP)-expressing neurons is sufficient to inhibit itch. Taken together, we showed that hunger or AgRP neuron activity inhibits itch, demonstrating that organisms have neural systems to filter and process ascending spinal signals activated by unpleasant somatosensory stimuli to prioritize salient needs.

Comparison of analgesic efficacy between rectus sheath blockade, intrathecal morphine with bupivacaine, and intravenous patient-controlled analgesia in patients undergoing robot-assisted laparoscopic prostatectomy: a prospective, observational clinical study

Background

We explored the analgesic outcomes on postoperative day (POD) 1 in patients undergoing robot-assisted laparoscopic prostatectomy (RALP) who received intravenous patient-controlled analgesia (IV-PCA), rectus sheath bupivacaine block (RSB), or intrathecal morphine with bupivacaine block (ITMB).

Methods

This was a prospective, observational clinical trial. Patients were divided into three groups: IV-PCA (n = 30), RSB (n = 30), and ITMB (n = 30). Peak pain scores at rest and with coughing, cumulative IV-PCA drug consumption, the need for IV rescue opioids, and Quality of Recovery-15 (QoR-15) questionnaire scores collected on POD 1 were compared among the groups.

Results

The preoperative and intraoperative findings were comparable among the groups; the ITMB group required the least remifentanil of all groups. During POD 1, the ITMB group reported lower levels of pain at rest and with coughing, compared with the other two groups. During POD 1, incidences of severe pain at rest (10.0% vs. 23.3% vs. 40.0%) and with coughing (16.7% vs. 36.7% vs. 66.7%) were the lowest in the ITMB group compared with the RSB and IV-PCA groups, respectively. After adjustment for age, body mass index, diabetes mellitus, hypertension, and intraoperative remifentanil infusion, severe pain at rest was 0.167-fold less common in the ITMB group than in the IV-PCA group, while pain with coughing was 0.1-fold lower in the ITMB group and 0.306-fold lower in the RSB group, compared with the IV-PCA group. The ITMB group required lower cumulative IV-PCA drug infusions and less IV rescue opioids, while exhibiting a better QoR-15 global score, compared with the other two groups. Complications (nausea and pruritus) were significantly more common in the ITMB group than in the other two groups; however, we noted no ITMB- or RSB-related anesthetic complications (respiratory depression, post-dural headache, nerve injury, or puncture site hematoma or infection), and all patients were assessed as Clavien-Dindo grade I or II during the hospital stay.

Conclusion

Although ITMB induced complications of nausea and pruritus, this analgesic technique provided appropriate pain relief that enhanced patient perception related to early postoperative recovery.

Trial registration

Clinical Research Information Service, Republic of Korea, (approval number: KCT0005040) on May 20, 2020

Management of pain in colorectal cancer patients

In this review we focus on the pathophysiology of CRC-related pain and discuss currently applied pain management. Pain is a symptom reported by over 70 % of colorectal cancer (CRC) patients. It remains a feared and debilitating consequence of both cancer and cancer-related treatment. There are many options for pain management in CRC, consisting of intravenous, oral or topical medications. In order to address the full spectrum of pain, proper treatment should address the nociceptive, neuropathic and/or psychogenic pain component. Currently available methods do not bring pain relief to satisfying number of patients and, if used improperly, can cause a number of complications. Therefore, future treatments should focus primarily on alleviating pain, but also on reducing possible side effects. In this article we cover recent and promising pharmacological and non- pharmacological developments emerging in the field of CRC treatment.

Medications for the prevention of pruritus in women undergoing cesarean delivery with Intrathecal morphine: A systematic review and bayesian network meta-analysis of randomized controlled trials

PURPOSE

Intrathecal morphine-induced pruritus can cause significant discomfort in parturients and is refractory to conventional antipruritic treatment. This systematic review and network meta-analysis evaluates the effectiveness of the medications used for prevention of intrathecal (IT) morphine-induced pruritus after cesarean delivery under spinal anesthesia.

METHODS

A literature search was conducted from 1946 up to October 2019. We included all randomized controlled trials (RCTs) that compared medications used for prevention of pruritus with a control group in women undergoing cesarean delivery under spinal anesthesia with IT morphine. The primary outcome examined was the incidence of pruritus up to 24 h after cesarean delivery. Dichotomous data were extracted and summarized using odds ratios (OR) and 95% credible intervals (CrI) with Bayesian random effects network meta-analysis model. The GRADE approach was used to evaluate quality of the studies and effect evidence.

RESULTS

Of the 26 studies included in the systematic review, 21 studies with a total of 2594 patients were included in the network meta-analysis [prophylaxis, n = 1603 (62%) vs. control, n = 991 (38%)]. These studies investigated seven classes of drugs including serotonin-receptor antagonists, dopamine-receptor antagonists, opioid agonist-antagonists, opioid-receptor antagonists, histamine-receptor antagonists, propofol and celecoxib. The network meta-analysis showed that serotonin-receptor antagonists' prophylaxis [control vs. prophylaxis: 60% vs. 47%; OR (95% CrI): 2.69 (1.43-5.36)] and opioid agonist-antagonists prophylaxis [control vs. prophylaxis: 72% vs. 47%; OR (95% CrI): 4.57 (1.67-12.91)] decreased the incidence of pruritus compared to the control group. Although all included studies were at low risk of bias, the quality of the overall network meta-analysis pooled estimates was low.

CONCLUSION

This bayesian network meta-analysis of RCTs demonstrates serotonin-receptor antagonists and opioid agonist-antagonists may prevent pruritus in women undergoing cesarean delivery with intrathecal morphine compared to control group. However, further RCTs of adequate power and clearly defined end points are warranted.

Intrathecal Morphine Versus Ketamine in Postoperative Pain After Hysterectomy: Double-Blinded, Randomized Clinical Trial

PURPOSE

Abdominal hysterectomy is one of the most commonly performed gynecologic surgical procedures and is frequently associated with moderate to severe pain. The present study compared the effects of morphine and ketamine on postoperative analgesia, hemodynamic stability, and postoperative adverse effects in patients who underwent abdominal hysterectomy.

DESIGN

This randomized controlled trial compares the effects of morphine plus adjuvants to those of ketamine plus adjuvants, administered as spinal anesthetic agents in patients who underwent abdominal hysterectomy.

METHODS

Eighty patients were randomly assigned to two different groups: group M (morphine, 40 mcg) and group K (ketamine, 20 mg); the anesthetic agents were combined with equal quantities of other adjuvants. Postoperative analgesia was evaluated by means of a numeric pain rating scale; adverse effects (pruritus, nausea and vomiting, urinary retention, respiratory depression, and changes in bowel habits) at specific postoperative time intervals of T1 (4 hours), T2 (12 hours), and T3 (24 hours) were documented and compared. Hemodynamic stability was assessed intraoperatively.

FINDINGS

Both groups displayed similar patient characteristics, comorbidities, paravertebral block level, and intraoperative hemodynamics. The present study observed a significant difference in postoperative analgesia between the two groups, 12 hours after the surgery, with group M exhibiting better results, compared with group K (P = .004). The pain scores obtained from group K were consistent with the amount of rescue medication (tramadol) administered to the subjects in the group, which showed a concomitant higher consumption of tramadol, compared with group M (42.5 and 71.8 mg in group M and group K, respectively, P = .011). Group M showed a higher incidence of pruritus, changes in bowel habits, and constipation compared with group K.

CONCLUSIONS

Compared with ketamine, intrathecal morphine obtained better postoperative analgesia up to 12 hours after surgery, with a higher incidence of pruritus without any significant change in other variables.

The Quality of Recovery after Dexamethasone, Ondansetron, or Placebo Administration in Patients Undergoing Lower Limbs Orthopedic Surgery under Spinal Anesthesia Using Intrathecal Morphine. A Randomized Controlled Trial

Intrathecal morphine is widely and successfully used to prevent postoperative pain after orthopedic surgery, but it is frequently associated with side effects. The aim of this study was to evaluate the effect of dexamethasone or ondansetron when compared to placebo to reduce the occurrence of these undesirable effects and, consequently, to improve the quality of recovery based on patient's perspective. Methods. One hundred and thirty-five patients undergoing lower extremity orthopedic surgery under spinal anesthesia using bupivacaine and morphine were randomly assigned to receive IV dexamethasone, ondansetron, or saline. On the morning following surgery, a quality of recovery questionnaire (QoR-40) was completed. Results. No differences were detected in the global and dimensional QoR-40 scores following surgery; however, following postanesthesia care unit (PACU) discharge, pain scores were higher in patients receiving ondansetron compared with patients who received dexamethasone. Conclusion. Neither ondansetron nor dexamethasone improves the quality of recovery after lower limbs orthopedic surgery under spinal anesthesia using intrathecal morphine.

A prospective randomized controlled study of combined spinal-general anesthesia vs. general anesthesia for laparoscopic gynecological surgery: Opioid sparing properties

STUDY OBJECTIVE

We aimed to determine the magnitude of peri-operative opioid sparing effect when general anesthesia is combined with spinal analgesia for laparoscopic gynecological surgery.

DESIGN

A prospective randomized controlled study; a three-group trial with two comparisons (each intervention group to control).

SETTING

Operating room and postoperative recovery area.

PATIENTS

Patients aged between 18 and 65 years with American Society of Anesthesiologists physical status 1 or 2 who were scheduled for inpatient elective laparoscopic gynecological surgery with expected pneumoperitoneum duration of at least 20 min. Of 102 randomized patients, 99 completed the study.

INTERVENTIONS

Patients were randomized to general anesthesia alone (control group) or combined with very-low-dose (levobupivacaine 3.75 mg; sufentanil 2.5 μg) or low-dose (levobupivacaine 7.5 mg; sufentanil 2.5 μg) spinal analgesia.

MEASUREMENTS

Primary endpoints were perioperative opioid consumption and pain scores (11-point numeric rating scale) at 30 min, 1 h, 2 h, 4 h and 24 h post-surgery. Secondary endpoints were patient satisfaction with anesthetic care and participation in research, sevoflurane consumption and adverse effects.

MAIN RESULTS

Intra-operative sufentanil (median [95% CI]) consumption was 16.1 (10.5-22.6) μg/h in the control group versus 4.7 (3.2-9.2) μg/h in the very-low-dose and versus 2.9 (0.0-4.0) μg/h in the low-dose spinal analgesia groups (p < 0.001, for both comparisons). Median (95% CI) piritramide consumption at 24 h post-surgery was 7.5 (3-8) mg in the control group versus 5 (0-7.5) mg in the very-low dose spinal analgesia group (p = 0.182) and versus 2 (0-2.5) mg in the low-dose spinal analgesia group (p = 0.001). Postoperative pain scores were consistently <3 only in the low dose spinal analgesia group. Patient satisfaction with anesthetic care and participation in research was very high in all groups.

CONCLUSIONS

Low-dose spinal analgesia in combination with general anesthesia reduces peri-operative opioid consumption in laparoscopic gynecological surgery in immediate postoperative period.

Strategies of analgesic treatment after cesarean delivery. Current state and new alternatives

The number of caesarean sections performed worldwide is increasing, and with it, the need for the optimal analgesia strategies. Deficient postoperative analgesia increases the need for opioids, delays recovery, and is associated with chronic pain and postpartum depression. It is essential to find good postoperative pain control strategies that facilitate early mobility, early recovery, and early hospital discharge with minimal side effects on the mother and infant. Multimodal analgesia based on neuroaxial anaesthesia with morphine in combination with non-opioids such as non-steroidal anti-inflammatory drugs and paracetamol, gives the best post-caesarean analgesia outcome, and allows anaesthesiologists to reserve opioids, corticoids, gabapentin, magnesium or ketamine for situations where neuroaxial anaesthesia cannot be performed, for high-risk patients, or when pain is difficult to control. Peripheral nerve block techniques can also be added, such as transverse abdominis plane block, erector spinae block, or continuous wound infiltration.

Incidence and risk factors for epidural morphine induced pruritus in parturients receiving cesarean section: A prospective multicenter observational study

This study is designed to clarify the incidence of epidural morphine induced pruritus (EMIP) in Chinese Han and Tibetan parturients after cesarean section (CS) and to identify the correlated risk factors.This is a prospective multicenter observational study. Follow-up evaluations were performed at 3 hours, 6 hours, 12 hours, 24 hours, and 48 hours after morphine administration. The primary outcome was EMIP incidence. Other details were also recorded for risk factor screening.Totally 284 parturients receiving CS were enrolled and 247 completed the study. The overall incidence of EMIP was 18.6% (46 in 247). The onset of pruritus was 5.6 ± 4.8 hours (mean ± SD) after morphine administration and the duration of pruritus was 14.0 ± 8.8 hours. Logistic regression models was built with 5 variables, history of allergy, serotonin receptor antagonist administration, I.V. fentanyl administration, epidural morphine volume and VAS pain score. Results of showed that 2 of the variables, history of allergy (P < .001) and serotonin receptor antagonist (P < .05), were significantly correlated with incidence of EMIP.In conclusion, EMIP incidence in our study was 18.6%. Positive medical history of allergy and not using serotonin receptor antagonist were potential risk factors of EMIP development.Trial registration: ChiCTR-OPC-17012345.

Sub-hypnotic dose of propofol as antiemetic prophylaxis attenuates intrathecal morphine-induced postoperative nausea and vomiting, and pruritus in parturient undergoing cesarean section - a randomized control trial

Background

Postoperative Nausea and Vomiting (PONV) is a dreadful and uncomfortable experience that significantly detracts patients’ quality of life after surgery. This study aimed to examine the antiemetic effect of a single sub-hypnotic dose of propofol as prophylaxis for PONV.

Method

In this prospective, double-blind, randomized control trial, 345 parturients presented for elective cesarean section at the Obstetric unit of Tamale Teaching Hospital were recruited. Each recruited parturient was randomly assigned to one of three groups; Propofol group (n = 115) represented those who received propofol 0.5 mg/kg, Metoclopramide group (n = 115) represented those who received metoclopramide 10 mg and, Control group (n = 115) represented those who received 0.9% saline. Spinal anesthesia with 0.5% hyperbaric bupivacaine 7.5–10 mg, and intrathecal morphine 0.2 mg was employed for the anesthesia.

Results

The data indicate that 108 (93.9%) parturients from the control group, 10 (8.7%) from the propofol group and 8 (7.0%) from the metoclopramide group experienced some incidence of PONV. There was no significant difference in the incidence of PONV (nausea, vomiting, and none) between the propofol and the metoclopramide groups (P = 0.99; 0.31; and 0.35 respectively). Parturients who received antiemetic agents were 105 (97.2%), 1 (10.0%) and 3 (37.5%) from the control, propofol and metoclopramide groups respectively. The data indicated that 98 (85.2%) parturients from the control, 3 (2.6%) from propofol group, and 100 (87.0%) from the metoclopramide group experienced some levels of pruritus. There was a significant difference in the incidence of pruritus (mild, moderate, and no pruritus) between the metoclopramide and propofol groups (P <  0.01; P <  0.01; and P <  0.01 respectively).

Conclusion

A sub-hypnotic dose of propofol is effective as metoclopramide in the prevention of PONV in parturient undergoing cesarean section under spinal anesthesia with intrathecal morphine. Sub-hypnotic dose of propofol significantly reduces the incidence of postoperative pruritus following intrathecal morphine use.

Trial registration

Current control trial, registered at ISRCTN trial registry: ISRCTN15475205. Date registered: 03/04/2019. Retrospectively registered.