The disruptive relationship among circadian rhythms, pain, and opioids

Disrupted Circadian Rhythms and Substance Use Disorders: A Narrative Review

Substance use disorder is a major global health concern, with a high prevalence among adolescents and young adults. The most common substances of abuse include alcohol, marijuana, cocaine, nicotine, and opiates. Evidence suggests that a mismatch between contemporary lifestyle and environmental demands leads to disrupted circadian rhythms that impair optimal physiological and behavioral function, which can increase the vulnerability to develop substance use disorder and related problems. The circadian system plays an important role in regulating the sleep-wake cycle and reward processing, both of which directly affect substance abuse. Distorted substance use can have a reciprocal effect on the circadian system by influencing circadian clock gene expression. Considering the detrimental health consequences and profound societal impact of substance use disorder, it is crucial to comprehend its complex association with circadian rhythms, which can pave the way for the generation of novel chronotherapeutic treatment approaches. In this narrative review, we have explored the potential contributions of disrupted circadian rhythms and sleep on use and relapse of different substances of abuse. The involvement of circadian clock genes with drug reward pathways is discussed, along with the potential research areas that can be explored to minimize disordered substance use by improving circadian hygiene.

Oblique subcostal transverse abdominis plane block for postoperative pain control in patients undergoing open sublay mesh hernia repair: a prospective double-blind randomized placebo-controlled clinical trial

BACKGROUND

A bilateral oblique subcostal transverse abdominis plane block may help provide perioperative analgesia and reduce opioid use in patients undergoing sublay mesh hernia repair, but its clinical value is unclear.

METHODS

In a single-centre, prospective, placebo-controlled, double-blind study, patients scheduled for sublay mesh hernia repair were randomized to receive oblique subcostal transverse abdominis plane blocks with either 60 ml of 0.375% ropivacaine (n=19) or isotonic saline (placebo, n=17). The primary outcome was patient-controlled total morphine consumption at 8:00 p.m. on the second postoperative day (POD), while secondary outcomes included the total morphine consumption during the post-anesthesia care unit stay and the occurrence of adverse events.

RESULTS

Total morphine consumption at 8:00 p.m. on the second POD was higher in patients receiving ropivacaine (39 mg, IQR 22, 62) compared with placebo (24 mg, IQR 7, 39), p value = 0.04. In contrast, the ropivacaine group received 2 mg less morphine during the post-anesthesia care unit stay (4 mg, IQR: 4, 9 mg vs 2 mg, IQR: 2,6 mg, p = 0.04). Patients receiving ropivacaine used more morphine (8:00 p.m. on the first POD until 8:00 a.m. on the second POD: 8 mg, IQR: 4, 18 mg vs 2 mg, IQR: 0, 9 mg, p = 0.01) and reported higher maximum pain scores since the last assessment (8:00 a.m. on the second POD: 5, IQR: 4, 7 vs 4, IQR: 3, 5, p = 0.03). There were no differences in adverse events between groups.

CONCLUSIONS

Bilateral oblique subcostal transverse abdominis plane blocks in patients undergoing sublay mesh hernia repair were not associated with a prolonged reduction in patient-controlled total morphine consumption in the evening of the second POD in this study. Rebound pain might explain the additional excess opioid required by the ropivacaine group.

The timing of the mouse hind paw incision does not influence postsurgical pain

Chronobiological approaches have emerged as tools to study pain and inflammation. Although time-of-day effects on the expression of pain after injury have been studied, it remains unaddressed whether the timing of the injury itself can alter subsequent pain behaviors. The aim of this study was to assess postsurgical pain behaviors in a mouse hind paw incision assay in a circadian-dependent manner. Incisions were made at one of four equally spaced time points over a 24-hour period, with evoked and spontaneous pain behaviors measured using the von Frey mechanical sensitivity test, Hargreaves' radiant heat paw-withdrawal test, and the Mouse Grimace Scale. Algesiometric testing was performed in C57BL/6 mice prior to and at multiple time points after incision injury, at the same time of day, until pain resolution. No statistically significant differences were observed between groups. This study adds to the literature on circadian rhythms and their influence on pain in the pursuit of more biologically informed pre- and postoperative care.

Opioid-induced adrenal insufficiency: diagnostic and management considerations

The dramatic rise in opioid use over the last two decades has led to a surge in their harmful health effects. Lesser known among clinicians is the impact of opioids on the endocrine system, especially with regard to cortisol. Opioids can suppress the hypothalamus-pituitary-adrenal (HPA) axis and may result in clinically significant adrenal insufficiency, especially in those treated at higher doses and for a longer time. A high clinical suspicion is necessary in this population for early diagnosis of opioid-induced adrenal insufficiency (OAI). Diagnosis of OAI is challenging, as the symptoms are often vague and overlap with those due to opioid use or the underlying pain disorder. Traditional assays to diagnose adrenal insufficiency have not been widely studied in this population, and more investigation is needed to determine how opioids might affect assay results. Once a diagnosis of adrenal insufficiency has been made, glucocorticoid replacement in the form of hydrocortisone is likely the mainstay of treatment, and effort should be made to taper down opioids where possible. Cortisol levels should be retested periodically, with the goal of stopping glucocorticoid replacement once the HPA axis has recovered. In this review, we provide context for diagnostic challenges in OAI, suggest diagnostic tools for this population based on available data, and offer recommendations for the management of this disorder. There is a paucity of literature in this field; given the widespread use of opioids in the general population, more investigation into the effects of opioids on the HPA axis is sorely needed.

Sleep Disorders and Chronic Pain Syndromes in the Pediatric Population

Sleep problems are widespread in children and adolescents suffering from chronic pain disorders. Sleep loss intensifies the experience of pain and is detrimental to the budding self-efficacy of a young individual with limitless horizons. Addressing sleep disorders may prevent the chronification of pain and prevent adverse health outcomes, such as functional impairment, psychiatric comorbidities and overall poor quality of life. This review will explore the cyclical nature between sleep, pain and mood, as well as the functional impact of this relationship on children and adolescents. There will be a discussion about sleep assessment and diagnostic testing, followed by a description of sleep disturbances found in specific pain conditions, ranging from headache, musculoskeletal/abdominal pain, to rheumatologic disorders. Finally, there will be a brief review of pharmacologic and behavioral interventions designed to improve sleep quality, and when possible, to alleviate pain.

Circadian rhythm disruptions associated with opioid use disorder in synaptic proteomes of human dorsolateral prefrontal cortex and nucleus accumbens

Opioid craving and relapse vulnerability is associated with severe and persistent sleep and circadian rhythm disruptions. Understanding the neurobiological underpinnings of circadian rhythms and opioid use disorder (OUD) may prove valuable for developing new treatments for opioid addiction. Previous work indicated molecular rhythm disruptions in the human brain associated with OUD, highlighting synaptic alterations in the dorsolateral prefrontal cortex (DLPFC) and nucleus accumbens (NAc)-key brain regions involved in cognition and reward, and heavily implicated in the pathophysiology of OUD. To provide further insights into the synaptic alterations in OUD, we used mass-spectrometry based proteomics to deeply profile protein expression alterations in bulk tissue and synaptosome preparations from DLPFC and NAc of unaffected and OUD subjects. We identified 55 differentially expressed (DE) proteins in DLPFC homogenates, and 44 DE proteins in NAc homogenates, between unaffected and OUD subjects. In synaptosomes, we identified 161 and 56 DE proteins in DLPFC and NAc, respectively, of OUD subjects. By comparing homogenate and synaptosome protein expression, we identified proteins enriched specifically in synapses that were significantly altered in both DLPFC and NAc of OUD subjects. Across brain regions, synaptic protein alterations in OUD subjects were primarily identified in glutamate, GABA, and circadian rhythm signaling. Using time-of-death (TOD) analyses, where the TOD of each subject is used as a time-point across a 24-h cycle, we were able to map circadian-related changes associated with OUD in synaptic proteomes associated with vesicle-mediated transport and membrane trafficking in the NAc and platelet-derived growth factor receptor beta signaling in DLPFC. Collectively, our findings lend further support for molecular rhythm disruptions in synaptic signaling in the human brain as a key factor in opioid addiction.

Circadian rhythm disruptions associated with opioid use disorder in the synaptic proteomes of the human dorsolateral prefrontal cortex and nucleus accumbens

Opioid craving and relapse vulnerability is associated with severe and persistent sleep and circadian rhythm disruptions. Understanding the neurobiological underpinnings of circadian rhythms and opioid use disorder (OUD) may prove valuable for developing new treatments for opioid addiction. Previous work indicated molecular rhythm disruptions in the human brain associated with OUD, highlighting synaptic alterations in the dorsolateral prefrontal cortex (DLPFC) and nucleus accumbens (NAc)-key brain regions involved in cognition and reward, and heavily implicated in the pathophysiology of OUD. To provide further insights into the synaptic alterations in OUD, we used mass-spectrometry based proteomics to deeply profile protein expression alterations in bulk tissue and synaptosome preparations from DLPFC and NAc of unaffected and OUD subjects. We identified 55 differentially expressed (DE) proteins in DLPFC homogenates, and 44 DE proteins in NAc homogenates, between unaffected and OUD subjects. In synaptosomes, we identified 161 and 56 DE proteins in DLPFC and NAc, respectively, of OUD subjects. By comparing homogenate and synaptosome protein expression, we identified proteins enriched specifically in synapses that were significantly altered in both DLPFC and NAc of OUD subjects. Across brain regions, synaptic protein alterations in OUD subjects were primarily identified in glutamate, GABA, and circadian rhythm signaling. Using time-of-death (TOD) analyses, where the TOD of each subject is used as a time-point across a 24- hour cycle, we were able to map circadian-related changes associated with OUD in synaptic proteomes related to vesicle-mediated transport and membrane trafficking in the NAc and platelet derived growth factor receptor beta signaling in DLPFC. Collectively, our findings lend further support for molecular rhythm disruptions in synaptic signaling in the human brain as a key factor in opioid addiction.