Sensitization to acute procedural pain in pediatric sickle cell disease: modulation by painful vaso-occlusive episodes, age, and endothelin-1

Patient-Reported Experiences in Voxelotor-Treated Children and Adults with Sickle Cell Disease: A Semistructured Interview Study

Objective

Voxelotor is a first-in-class sickle hemoglobin-polymerization inhibitor that was approved in 2019 by the US Food and Drug Administration for treatment of patients with sickle cell disease (SCD) aged ≥12 years; in 2021, the approval was extended to children with SCD aged 4 to 11 years. Additionally, both the Ministry of Health and Prevention for the United Arab Emirates and the European Commission granted marketing authorization for voxelotor in September 2021 and February 2022, respectively, for treatment of SCD in adults and pediatric patients aged ≥12 years. Thus, additional information on the patient experience with voxelotor would be useful for patients, caregivers, and healthcare professionals alike. The purpose of this study was to conduct semistructured interviews in an effort to understand the experiences and perspectives of voxelotor-treated patients with SCD.

Methods

One-time semistructured interviews with adults, adolescents, and children with SCD and their primary caregivers were conducted in the United States. Twenty-three adults and adolescents were recruited across 4 clinical sites, and 10 children-caregiver dyads were recruited from a single site. The interview was designed to elicit patient perspectives on symptomatic changes with voxelotor and the impact of treatment on patients' perceived health-related quality of life. Individual interview transcripts were analyzed using a thematic analytic approach, and concept saturation was assessed in both cohorts.

Results

Most patients reported improvements in their SCD symptoms with voxelotor treatment, specifically regarding pain crises, jaundice, and fatigue. Almost all patients experienced improvements in self-reported health-related quality of life with voxelotor treatment.

Conclusions

This study provides patient and caregiver perspectives on the symptomatic benefits of voxelotor treatment. These findings not only highlight the benefits of voxelotor treatment in improving symptoms and increasing health-related quality of life across the entire SCD population but also can inform further research on SCD-specific patient-reported outcomes.

Distracting Through Procedural Pain and Distress Using Virtual Reality and Guided Imagery in Pediatric, Adolescent, and Young Adult Patients: Randomized Controlled Trial

BACKGROUND

Children with acute and chronic illness undergo frequent, painful, and distressing procedures.

OBJECTIVE

This randomized controlled trial was used to evaluate the effectiveness of guided imagery (GI) versus virtual reality (VR) on the procedural pain and state anxiety of children and young adults undergoing unsedated procedures. We explored the role of trait anxiety and pain catastrophizing in intervention response.

METHODS

Children and young adults were recruited from the hematology, oncology, and blood and marrow transplant clinics at a children's hospital. Each study participant completed the GI and VR intervention during separate but consecutive unsedated procedures. Self-report measures of pain and anxiety were completed before and after the procedures.

RESULTS

A total of 50 participants (median age 13 years) completed both interventions. GI and VR performed similarly in the management of procedural pain. Those with high pain catastrophizing reported experiencing less nervousness about pain during procedures that used VR than those using GI. State anxiety declined pre- to postprocedure in both interventions; however, the decrease reached the level of significance during the VR intervention only. Those with high trait anxiety had less pain during GI.

CONCLUSIONS

In our sample, VR worked as well as GI to manage the pain and distress associated with common procedures experienced by children with acute or chronic illnesses. Children who are primed for pain based on beliefs about pain or because of their history of chronic pain had a better response to VR. GI was a better intervention for those with high trait anxiety.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04892160; https://clinicaltrials.gov/ct2/show/NCT04892160.

Clinical Interpretation of Self-Reported Pain Scores in Children with Acute Pain

OBJECTIVE

To identify self-reported pain scores that best represent categories of no pain, mild, moderate, and severe pain in children, and a pain score that accurately represents a child's perceived need for medication, that is, a minimum pain score at which a child would want an analgesic.

STUDY DESIGN

Prospective cross-sectional cohort study of children aged 6-17 years presenting to a pediatric emergency department with painful and nonpainful conditions. Pain was measured using the 10-point Verbal Numerical Rating Scale. Receiver operating characteristic -based methodology was used to determine pain scores that best differentiated no pain from mild pain, mild pain from moderate pain, and moderate pain from severe pain. Descriptive statistics were used to determine the perceived need for medication.

RESULTS

We analyzed data from 548 children (51.3% female, 61.9% with a painful condition). The scores that best represent categories of pain intensity are as follows: 0-1 for no pain; 2-5 for mild pain; 6-7 for moderate pain; and 8-10 for severe pain. The area under the curve for the cut points differentiating each category ranged from 0.76 to 0.88. The median pain score representing the perceived need for medication was 6 (IQR, 4-7; range, 0-10).

CONCLUSIONS

We identified population-level self-reported pain scores in children associated with categories of pain intensity that differ from scores conventionally used. Implementing our findings may provide a more accurate representation of the clinical meaning of pain scores and reduce selection bias in research. Our findings do not support the use of pain scores in isolation for clinical decision making or the use of a pain score threshold to represent a child's perceived need for medication.

Changes in Pain Score Associated With Clinically Meaningful Outcomes in Children With Acute Pain

BACKGROUND

Identifying changes in pain score associated with clinically meaningful outcomes is necessary when using self-report measures to assess pain in children. We aimed to determine the changes in pain score associated with a minimum clinically significant difference (MCSD), ideal clinically significant difference (ICSD), and patient-perceived adequate analgesia (PPAA) and to evaluate for differences based on initial pain intensity and patient characteristics.

METHODS

This was a cross-sectional study of children 6 to 17 and 4 to 17 years old who were assessed using the Verbal Numerical Rating Scale (VNRS) and Faces Pain Scale-Revised (FPS-R), respectively. Children qualitatively described any endorsed change in pain score; those who received an analgesic were asked if they wanted additional analgesics to decrease their pain intensity. We used a receiver operating characteristic curve-based methodology to identify changes in pain score associated with "a little less" and "much less" pain (MCSD and ICSD, respectively) and patients declining additional analgesics because of adequate analgesia (PPAA).

RESULTS

We enrolled 431 children with painful conditions. For the VNRS, raw change and percent reductions in pain scores associated with MCSD, ICSD, and PPAA were 2/10 and 20%, 3/10 and 44%, and 2/10 and 29%, respectively, and for the FPS-R, 2/10 and 33%, 4/10 and 60%, and 4/10 and 40%, respectively. Raw change in pain scores increased with increasing initial pain intensity, but percent reductions remained stable. There were no significant differences based on patient characteristics such as age, sex, and race/ethnicity.

CONCLUSION

Our findings provide patient-centered outcomes in children that are suitable for designing trials and are generalizable across patient characteristics.

Defining No Pain, Mild, Moderate, and Severe Pain Based on the Faces Pain Scale-Revised and Color Analog Scale in Children With Acute Pain

OBJECTIVES

The aims of this study were to define the Faces Pain Scale-Revised (FPS-R) and Color Analog Scale (CAS) scores associated with no pain, mild pain, moderate pain, and severe pain in children with acute pain, and to identify differences based on age, sex, and ethnicity.

METHODS

We conducted a prospective observational study in 2 pediatric emergency departments of children aged 4 to 17 years with painful and nonpainful conditions. We assessed their pain intensity using the FPS-R, CAS, and qualitative measures. Pain score cut points that best differentiated adjacent categories of pain were identified using a receiver operating characteristic-based method. Cut points were compared within subgroups based on age, sex, and ethnicity.

RESULTS

We enrolled 620 patients, of whom 314 had painful conditions. The mean age was 9.2 years; 315 (50.8%) were in the younger age group (aged 4-7 years); 291 (46.8%) were female; and 341 (55%) were Hispanic. The scores best representing categories of pain for the FPS-R were as follows: no pain, 0 and 2; mild pain, 4; moderate pain, 6; and severe pain, 8 and 10. For the CAS, these were 0 to 1, 1.25 to 2.75, 3 to 5.75, and 6 to 10, respectively. Children with no pain frequently reported nonzero pain scores. There was considerable overlap of scores associated with mild and moderate pain. There were no clinically meaningful differences of scores representing each category of pain based on age, ethnicity, and race.

CONCLUSIONS

We defined pain scores for the FPS-R and CAS associated with categories of pain intensity in children with acute pain that are generalizable across subgroups based on patient characteristics. There were minor but potentially important differences in pain scores used to delineate categories of pain intensity compared to prior convention.

Ghanaian nurses' knowledge of invasive procedural pain and its effect on children, parents and nurses

AIM

To explore Ghanaian nurses' knowledge of invasive procedural pain in children who are in hospital and to identify the effect of unrelieved pain on children, parents and nurses.

METHOD

An exploratory, descriptive and qualitative design was adopted. A purposive sampling technique was used and individual face-to-face, semi-structured interviews were conducted with 16 registered nurses from four children's units at a hospital in the Eastern Region of Ghana. Thematic and content analyses were performed.

FINDINGS

Four themes emerged: types of invasive procedure; pain expression; pain assessment; and effects of unrelieved pain. Participants had adequate knowledge of painful invasive procedures, however, they were not aware of the range of available validated pain assessment tools, using observations and body language instead to assess pain.

CONCLUSION

Ghanaian nurses require education on the use of validated rating scales to assess procedural pain in children. The inclusion of pain assessment and management in pre-registration curricula could improve knowledge.

Endothelin receptor antagonists in sickle cell disease: A promising new therapeutic approach

Sickle cell disease (SCD) is a genetic hematologic disorder that is characterized by a variety of potentially life threatening acute and chronic complications. Currently, hydroxyurea is the only clinically approved pharmacological therapy for the treatment of SCD, and the continued prevalence of severe disease complications underscores the desperate need for the development of new therapeutic agents. Central features of the sickle cell disease milieu, including hypoxia, oxidative stress, and thrombosis, are established enhancers of endothelin-1 (ET-1) synthesis. This conceptual connection between ET-1 and SCD was confirmed by multiple studies that demonstrated markedly elevated plasma and urinary levels of ET-1 in SCD patients. Direct evidence for the involvement of ET-1 signaling in the development of SCD pathologies has come from studies using endothelin receptor antagonists in SCD mice. This review summarizes recent studies that have implicated ET-1 signaling as a mechanistic contributor to renal, vascular, pulmonary, and nociceptive complications of sickle cell disease and discusses the potential for the use of ET receptor antagonists in the treatment of SCD.

Endothelin

The endothelins comprise three structurally similar 21-amino acid peptides. Endothelin-1 and -2 activate two G-protein coupled receptors, ETA and ETB, with equal affinity, whereas endothelin-3 has a lower affinity for the ETA subtype. Genes encoding the peptides are present only among vertebrates. The ligand-receptor signaling pathway is a vertebrate innovation and may reflect the evolution of endothelin-1 as the most potent vasoconstrictor in the human cardiovascular system with remarkably long lasting action. Highly selective peptide ETA and ETB antagonists and ETB agonists together with radiolabeled analogs have accurately delineated endothelin pharmacology in humans and animal models, although surprisingly no ETA agonist has been discovered. ET antagonists (bosentan, ambrisentan) have revolutionized the treatment of pulmonary arterial hypertension, with the next generation of antagonists exhibiting improved efficacy (macitentan). Clinical trials continue to explore new applications, particularly in renal failure and for reducing proteinuria in diabetic nephropathy. Translational studies suggest a potential benefit of ETB agonists in chemotherapy and neuroprotection. However, demonstrating clinical efficacy of combined inhibitors of the endothelin converting enzyme and neutral endopeptidase has proved elusive. Over 28 genetic modifications have been made to the ET system in mice through global or cell-specific knockouts, knock ins, or alterations in gene expression of endothelin ligands or their target receptors. These studies have identified key roles for the endothelin isoforms and new therapeutic targets in development, fluid-electrolyte homeostasis, and cardiovascular and neuronal function. For the future, novel pharmacological strategies are emerging via small molecule epigenetic modulators, biologicals such as ETB monoclonal antibodies and the potential of signaling pathway biased agonists and antagonists.

Serum apelin as a novel non-invasive marker for subclinical cardiopulmonary complications in children and adolescents with sickle cell disease

BACKGROUND

Cardiovascular involvement represents a leading cause of mortality and morbidity in sickle cell disease (SCD). Apelin is a peptide involved in the regulation of cardiovascular function.

AIM

To determine serum apelin among 40 children and adolescents with SCD compared with 40 healthy controls and assess its relation to markers of hemolysis, iron overload as well as cardiopulmonary complications.

METHODS

SCD patients, in steady state and asymptomatic for heart disease, were studied stressing on hydroxyurea/chelation therapy, hematological profile, serum ferritin and apelin levels. Full echocardiographic study including assessment of biventricular systolic function and pulmonary artery pressure was done.

RESULTS

Apelin levels were significantly lower in SCD patients compared with controls (P<0.001). Cardiopulmonary complications were encountered in 30% of patients. Apelin was significantly decreased among patients with cardiopulmonary disease (P=0.006) whether those at risk of pulmonary hypertension (P=0.018) or patients with heart disease (P=0.043). Hydroxyurea-treated patients had higher apelin levels than untreated ones (P=0.001). Apelin was negatively correlated to lactate dehydrogenase, indirect bilirubin, serum ferritin, end systolic diameter, tricuspid regurgitant jet velocity, right ventricle systolic pressure, pulmonary vascular resistance and tissue Doppler imaging S wave. Apelin cutoff value of 1650ng/L could significantly detect the presence of cardiopulmonary complications in SCD with 90.9% sensitivity and 72.4% specificity.

CONCLUSION

Apelin is a promising marker for screening of SCD patients at risk of cardiopulmonary disease because it is altered during the early subclinical stage of cardiac affection. A combination of apelin and echocardiography provides a reliable method to assess cardiopulmonary affection in young SCD patients.

Clinically significant differences in acute pain measured on self-report pain scales in children

OBJECTIVES

The objective was to determine the minimum and ideal clinically significant differences (MCSD, ICSD) in pain intensity in children for the Faces Pain Scale-Revised (FPS-R) and the Color Analog Scale (CAS) and to identify any differences in these estimates based on patient characteristics.

METHODS

This was a prospective study of children aged 4 to 17 years with acute pain presenting to two urban pediatric emergency departments. Participants self-reported their pain intensity using the FPS-R and CAS and qualitatively described their changes in pain. Changes in pain score reported using the FPS-R and CAS that were associated with "a little less" and "much less" pain (MCSD and ICSD, respectively) were identified using a receiver operating characteristic-based method and expressed as raw change score and percent reductions. Estimates of MCSD and ICSD were determined for each category of initial pain intensity (mild, moderate, and severe) and patient characteristics (age, sex, and ethnicity). Post hoc exploratory analyses evaluated categories of race, primary language, and etiology of pain.

RESULTS

A total of 314 children with acute pain were enrolled; mean (±SD) age was 9.8 (±3.8) years. The FPS-R raw change score and percent reduction MCSD estimates were 2/10 and 25%, with ICSD estimates of 3/10 and 60%. For the CAS, raw change score and percent reduction MCSD estimates were 1/10 and 15%, with ICSD estimates of 2.75/10 and 52%. For both scales, raw change score and percent reduction estimates of the MCSD remained unchanged in children with either moderate or severe pain. For both scales, estimates of ICSD were not stable across categories of initial pain intensity. There was no difference in MCSD or ICSD based on age, sex, ethnicity, race, primary language, or etiology of pain.

CONCLUSIONS

The MCSD estimates can be expressed as raw change score and percent reductions for the FPS-R and CAS. These estimates appear stable for children with moderate to severe pain, irrespective of age, sex, and ethnicity. Estimates of ICSD were not stable across different categories of initial pain intensity, therefore limiting their potential generalizability.

Modulation of pain in pediatric sickle cell disease: understanding the balance between endothelin mediated vasoconstriction and apelin mediated vasodilation

Children with sickle cell disease (SCD) have painful vaso-occlusive episodes (VOEs), which often reoccur across the individual's lifespan. Vaso-constrictive and vaso-dilatory molecules have been hypothesized to play a role in VOEs. Endothelin-1 (ET-1) is a potent vasoconstrictor that is released during VOEs and is correlated with pain history. Apelin is a vaso-dilatory peptide that also has a modulatory role in pain processing. We hypothesize that the ratio between vaso-dilatory and vaso-constrictive tone in children with SCD may be a marker of pain sensitization and vaso-occlusion. Plasma endothelin and apelin levels were measured in 47 children with SCD. Procedural pain and baseline pain were assessed via child- and caregiver-reports and observational distress. Pain history was assessed using retrospective chart review. Plasma apelin was related to age, with decreased levels in older children. The ratio between apelin and ET-1 was negatively correlated to observational baseline pain. The ratio between apelin and Big ET was negatively correlated to caregiver ratings of baseline pain and positively correlated to history of VOEs, which is possibly due to hydroxyurea treatment. These results suggest that an imbalance in the apelin and endothelin systems may contribute to an increasing number of VOEs and baseline pain in children with SCD.

Endothelin-1 induced desensitization in primary afferent neurons

Endothelin-1 (ET-1) is a known algogen that causes acute pain and sensitization in humans and spontaneous nociceptive behaviors when injected into the periphery in rats, and is elevated during vaso-occlusive episodes (VOEs) in sickle cell disease (SCD) patients. Previously, our lab has shown that a priming dose of ET-1 produces sensitization to capsaicin-induce secondary hyperalgesia. The goal of this study was to determine if the sensitization induced by ET-1 priming is occurring at the level of the primary afferent neuron. Calcium imaging in cultured dorsal root ganglion (DRG) neurons was utilized to examine the effects of ET-1 on primary afferent neurons. ET-1 induces [Ca(2+)]i transients in unprimed cells. ET-1 induced [Ca(2+)]i transients are attenuated by priming with ET-1. This priming effect occurs whether the priming dose is given 0-4 days prior to the challenge dose. Similarly, ET-1 priming decreases capsaicin-induced [Ca(2+)]i transients. At the level of the primary afferent neuron, ET-1 priming has a desensitizing effect on challenge exposures to ET-1 and capsaicin.

Evidence for the endothelin system as an emerging therapeutic target for the treatment of chronic pain

Many people worldwide suffer from pain and a portion of these sufferers are diagnosed with a chronic pain condition. The management of chronic pain continues to be a challenge, and despite taking prescribed medication for pain, patients continue to have pain of moderate severity. Current pain therapies are often inadequate, with side effects that limit medication adherence. There is a need to identify novel therapeutic targets for the management of chronic pain. One potential candidate for the treatment of chronic pain is therapies aimed at modulating the vasoactive peptide endothelin-1. In addition to vasoactive properties, endothelin-1 has been implicated in pain transmission in both humans and animal models of nociception. Endothelin-1 directly activates nociceptors and potentiates the effect of other algogens, including capsaicin, formalin, and arachidonic acid. In addition, endothelin-1 has been shown to be involved in inflammatory pain, cancer pain, neuropathic pain, diabetic neuropathy, and pain associated with sickle cell disease. Therefore, endothelin-1 may prove a novel therapeutic target for the relief of many types of chronic pain.

Cold hypersensitivity increases with age in mice with sickle cell disease

Sickle cell disease (SCD) is associated with acute vaso-occlusive crises that trigger painful episodes and frequently involves ongoing, chronic pain. In addition, both humans and mice with SCD experience heightened cold sensitivity. However, studies have not addressed the mechanism(s) underlying the cold sensitization or its progression with age. Here we measured thermotaxis behavior in young and aged mice with severe SCD. Sickle mice had a marked increase in cold sensitivity measured by a cold preference test. Furthermore, cold hypersensitivity worsened with advanced age. We assessed whether enhanced peripheral input contributes to the chronic cold pain behavior by recording from C fibers, many of which are cold sensitive, in skin-nerve preparations. We observed that C fibers from sickle mice displayed a shift to warmer (more sensitive) cold detection thresholds. To address mechanisms underlying the cold sensitization in primary afferent neurons, we quantified mRNA expression levels for ion channels thought to be involved in cold detection. These included the transient receptor potential melastatin 8 (Trpm8) and transient receptor potential ankyrin 1 (Trpa1) channels, as well as the 2-pore domain potassium channels, TREK-1 (Kcnk2), TREK-2 (Kcnk10), and TRAAK (Kcnk4). Surprisingly, transcript expression levels of all of these channels were comparable between sickle and control mice. We further examined transcript expression of 83 additional pain-related genes, and found increased mRNA levels for endothelin 1 and tachykinin receptor 1. These factors may contribute to hypersensitivity in sickle mice at both the afferent and behavioral levels.