Opioid-Induced Hyperalgesia

Preclinical study in a postoperative pain model to investigate the action of ketamine, lidocaine, and ascorbic acid in reversing fentanyl-induced, non-glutamate-dependent hyperalgesia

Introduction

Opioid-induced hyperalgesia (OIH) is a paradoxical phenomenon in which exposure to opioids can increase sensitivity to painful stimuli. Currently, several drugs have been used in an attempt to prevent OIH. We design this study to address the effect of preemptive treatment with ketamine, lidocaine, and ascorbic acid in a rat preclinical model of perioperative opioid-induced hyperalgesia.

Methods

To reproduce OIH in a model of postoperative pain, rats received successive doses of fentanyl subcutaneously and underwent an incision in the paw. In an attempt to prevent OIH, ketamine, lidocaine, and ascorbic acid were administered before treatment with fentanyl. The von Frey test and the hot-plate test were used to evaluate mechanical allodynia and thermal hyperalgesia, respectively, with a follow-up period from 1 hour up to 7 days after surgery. Spinal cord nerve terminals (synaptosomes) were used to assess glutamate release under our experimental conditions.

Results

Consecutive fentanyl injections increased the postoperative pain as indicated by increased thermal hyperalgesia and allodynia 48 hours after incision. Ketamine, lidocaine, and the combination of ketamine + lidocaine were able to prevent thermal hyperalgesia but not mechanical allodynia. Ascorbic acid did not prevent the hyperalgesia induced by fentanyl. We found no correlation between spinal glutamate release and the pharmacological treatments.

Conclusion

Fentanyl induced a hyperalgesic effect that last few days in a postoperative model of pain. Hyperalgesic effect was not totally inhibited by ketamine and lidocaine in rats. Increased glutamate release was not the main molecular mechanism of fentanyl-induced hyperalgesia.

Demand-only patient-controlled analgesia for treatment of acute vaso-occlusive pain in sickle cell disease

BACKGROUND

Sickle cell disease (SCD) is a chronic illness that is associated with frequent admissions for vaso-occlusive episodes (VOE). Opioids are frequently utilized in pain management, but dosing is often provider dependent. Opioids cause both short-term and long-term side effects, so the minimal effective dose is desired. This study examined demand-only patient-controlled analgesia (PCA) in pediatric patients.

METHODS

A new clinical practice guideline (CPG) for a single institution was implemented, which eliminated basal infusion dosing for PCAs on hospital admission. The primary aim of this retrospective study was to evaluate length of stay (LOS) before and after implementation of a CPG of demand-only PCA and, in a selected subpopulation, addition of short-term methadone. Secondary aims included opioid utilization, acute chest syndrome (ACS), and hypoxia. Inclusion criteria included SCD, ≤21 years of age, uncomplicated VOE admission, and ≥ 3 and ≤ 8 hospital admissions for SCD pain control within one calendar year.

RESULTS

LOS decreased postintervention (7.2 ± 5.1 vs 4.5 ± 3.8 days, P < 0.001). Mean total opioid utilization in morphine equivalents mg/kg markedly decreased between the cohorts (13.3 ± 33.8 vs 3.6 ± 3.0, P < 0.001). ACS (21.9% vs 2.8%, P = 0.004) and hypoxia (28% vs 6.9%, P< 0.001) decreased significantly as well.

CONCLUSION

Bolus PCA dosing of opioids resulted in decreased LOS and reductions in opioid utilization, hypoxia, and ACS.

Is the Presence of a Psychiatric Disorder Associated With More Aggressive Management of Compartment Syndrome?

OBJECTIVE

To determine whether pre-existing psychiatric disorder is associated with potentially unnecessary fasciotomy.

DESIGN

Retrospective cohort study.

SETTING

Academic Level-1 trauma center.

PATIENTS

All the patients with orthopaedic trauma undergoing leg fasciotomy at an academic Level I trauma center from 2006 to 2020.

INTERVENTION

Pre-existing diagnosis of psychiatric disorder.

MAIN OUTCOME MEASUREMENTS

Early primary wound closure and delayed primary wound closure.

RESULTS

In total, 116 patients were included. Twenty-seven patients (23%) had a pre-existing diagnosis of psychiatric disorder with 13 having anxiety, 14 depression, 5 bipolar disorder, and 2 ADHD. Several patients had multiple diagnoses. Fifty-one patients (44%) had early primary closure (EPC), and 65 patients (56%) had delayed primary closure. Of patients with a psychiatric disorder, 52% received EPC compared with 42% of patients without a disorder, P = 0.38. This lack of a strong association did not seem to vary across specific psychiatric conditions. After adjusting for sex, age, injury type, and substance abuse, there was still no significant association between a psychiatric disorder and EPC with an odds ratio of 1.08 (95% CI, 0.43-2.75).

CONCLUSIONS

Among patients with orthopaedic trauma undergoing emergent fasciotomy for acute compartment syndrome, a psychiatric disorder was not associated with a significantly increased rate of possibly unnecessary fasciotomy. Given the potential for a psychiatric condition to complicate the diagnosis of acute compartment syndrome, this data is somewhat reassuring; however, there remains a need for continued vigilance in treating patients with psychiatric conditions and research in this area.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Opioid-induced Hyperalgesia in Patients With Chronic Pain: A Systematic Review of Published Cases

INTRODUCTION

Opioid-induced hyperalgesia (OIH) remains an issue in patients with chronic pain. Multiple cases of OIH in patients with chronic pain exposed to opioids have been reported worldwide. The objective of this systematic review was to summarize the evidence of OIH from clinical reports.

METHODS

We searched the PubMed, Cochrane, EMBASE, and LILACS databases for case reports and case series of OIH published up to December 2020, with the aim to summarize the evidence for OIH in patients with chronic pain from clinical reports and to discuss issues relevant to the clinical diagnosis and management of OIH.

RESULTS

We retrieved and reviewed 41 articles describing 72 cases. Clinical features of OIH were observed in patients of both sexes, all ages, and with various types of pain treated with different classes of opioids. OIH was reported at all doses, but most published studies reported a pattern of OIH following treatment with very high daily doses of opioids (median oral morphine equivalent dose of 850 mg). OIH was diagnosed clinically in all cases. Three different strategies for OIH management were described: opioid rotation, opioid cessation, and the use of adjuvant pharmacotherapies. All had statistically similar success rates for OIH treatment: 72%, 57%, and 79%, respectively. The decrease in pain was achieved rapidly (mean: 8 d; range: 1 to 28 d). Adjuvant therapies resulted in the largest decrease in dose. Ketamine and dexmedetomidine were the most widely used adjuvant drugs.

CONCLUSION

The key finding is that clinical symptoms of OIH can be resolved when this condition is diagnosed and managed.

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Prescribing opioids in older people

People are living to older age. Demographic pressures are driving change. Opiate analgesics are the most powerful known pain relievers. Persistent pain, both cancer and non-cancer types is frequent in older adults. The use of opioid analgesics is appropriate in the treatment of moderate to severe persistent pain. The challenge of prescribing opioids in older adults is to understand the factors involved in making appropriate choices and monitoring the beneficial effects of pain relief while managing the side-effects. This article will review the current concepts, evidence and controversies surrounding opiate use in the elderly. An approach is outlined which involves: pain assessment, screening for substance abuse potential, deciding whether you are able to treat your patient without help, starting treatment, monitoring effectiveness of pain control and managing opioid-associated side-effects. The goal of pain management using opioids is the attainment of improved function and quality of life.