Dextromethorphan Analgesia in a Human Experimental Model of Hyperalgesia

Anesthesia via peripheral nerve blocks during total knee replacement has no effect on postoperative inflammation in elderly patients

BACKGROUND

We have previously shown that, compared with general anesthesia (GA), the procedure of peripheral nerve blocks (PNB) facilitates faster recovery of elderly patients from total knee replacement (TKR). Here, we investigated whether the faster recovery is associated with decreased perioperative stress and inflammation and decreased incidences of postoperative complications.

METHODS

After randomization, 165 patients aged ≥65 years underwent TKR under GA or PNB. The primary outcomes were the perioperative inflammation and stress levels, based on the serum C-reactive protein and interleukin-6 levels, erythrocyte sedimentation rate, white-blood cell and neutrophil counts, and blood-sugar level. The secondary outcomes were the postoperative complications, including cardiovascular, respiratory, and hepatic or renal complications, insomnia, delirium, electrolyte disturbances, and nausea and vomiting.

RESULTS

The two groups were not significantly demographically different (p > .05). Of the cytokines related to stress and inflammation, the differences of time points were statistically significant between the two groups (p < .01), but two-way ANOVA revealed no interaction between the time points and groups. Incidences of postoperative complications were far lower in PNB group than in GA group (p = .006). Incidences of postoperative respiratory complications (p = .005) and postoperative nausea and vomiting (p = .040) were significantly lower in PNB group than in GA group. There were no significant differences in other complications between the two groups (p > .05).

CONCLUSIONS

PNB does not alleviate the stress and inflammation in elderly patients post TKR but significantly reduces the incidences of postoperative complications, especially respiratory complications, and nausea and vomiting. (ClinicalTrials.gov Identifier: NCT01871012).

Evaluation of Pupillometry for CYP2D6 Phenotyping in Children Treated with Tramadol

Following the contraindication of codeine use in children, increasing use of tramadol has been observed in pain management protocols. However, tramadol's pharmacokinetics (PK) and pharmacodynamics are influenced by cytochrome P450 (CYP)2D6 activity, similarly to codeine. Previous studies in adults have demonstrated a correlation between pupillary response and tramadol PK. Our objective was to evaluate pupillometry as a phenotyping method to assess CYP2D6 activity in children treated with tramadol. We included 41 children (mean age 11 years) receiving a first dose of tramadol (2 mg/kg) in the emergency room (ER) as part of their routine care. CYP2D6 phenotyping and genotyping were performed. The concentrations of tramadol and its active metabolite, M1, were measured, and static and dynamic pupillometry was conducted using a handheld pupillometer at the time of tramadol administration and during the ER stay. Pupillometric measurements were obtained for 37 children. Tramadol affected pupillary parameters, with a decrease in pupil diameter in 83.8% of children (p = 0.002) (mean decrease 14.1 ± 16.7%) and a decrease in reflex amplitude constriction in 78.4% (p = 0.011) (mean decrease 17.7 ± 34.5%) at T150 compared to T0. We were unable to identify a correlation between pupillometry measurements and CYP2D6 activity. Likely confounding factors include light intensity, pain, and stress, making the procedure less feasible in paediatric emergency settings.

Analgesic Effect of Electroacupuncture on Postherpetic Neuralgia: A Trial Protocol for a Multicenter Randomized Controlled Trial

INTRODUCTION

The chronic neuropathic pain associated with postherpetic neuralgia (PHN) can last for several months or even many years, seriously affecting the affected person's work, sleep, mood, and daily life activities. In generaly, current treatments for PHN are at best limited and unsatisfactory, and adverse reactions are common, especially in elderly patients. Electroacupuncture (EA) is widely used clinically to manage painful diseases, but there remains a lack of evidence to support the effectiveness of EA on PHN. This study is designed to assess the efficacy and safety of EA on PHN, and to provide evidence-based medical evidence for EA treatment of PHN.

METHODS

This multicenter, prospective, randomized controlled trial will recruit 448 patients with PHN at seven clinical centers. Multicenter stratified variable block randomization will be used, and the eligible patients will be randomly allocated in a ratio of 1:1 to the EA group or sham EA group. The EA group will receive 4 weeks of EA treatment, given as 30-min treatment sessions, once daily, 5 times per week, for a total of 20 treatments; the sham EA group will receive sham EA treatment under the same conditions.

PLANNED OUTCOMES

The primary outcome measure is the 11-point Numeric Rating Scale pain score at week 4. The secondary outcome measures, including mechanical pain threshold, pain area of PHN, average number of pain episodes, the short-form McGill Pain Questionnaire 2, Zoster Brief Pain Inventory, the Depression, Anxiety, and Positive Outlook Scale, Patient Global Impression of Change, safety of EA, and use of concomitant medications, among others. The primary analysis of the outcomes will be the mixed-effect model with repeated measurement between groups on an intent-to-treat population.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT04560361. Registered 23 September 2020 ( https://clinicaltrials.gov/ct2/show/NCT04560361?term=NCT04560361&draw=2&rank=1 ).

Human surrogate models of central sensitization: A critical review and practical guide

Background

As in other fields of medicine, development of new medications for management of neuropathic pain has been difficult since preclinical rodent models do not necessarily translate to the clinics. Aside from ongoing pain with burning or shock‐like qualities, neuropathic pain is often characterized by pain hypersensitivity (hyperalgesia and allodynia), most often towards mechanical stimuli, reflecting sensitization of neural transmission.

Data treatment

We therefore performed a systematic literature review (PubMed‐Medline, Cochrane, WoS, ClinicalTrials) and semi‐quantitative meta‐analysis of human pain models that aim to induce central sensitization, and generate hyperalgesia surrounding a real or simulated injury.

Results

From an initial set of 1569 reports, we identified and analysed 269 studies using more than a dozen human models of sensitization. Five of these models (intradermal or topical capsaicin, low‐ or high‐frequency electrical stimulation, thermode‐induced heat‐injury) were found to reliably induce secondary hyperalgesia to pinprick and have been implemented in multiple laboratories. The ability of these models to induce dynamic mechanical allodynia was however substantially lower. The proportion of subjects who developed hypersensitivity was rarely provided, giving rise to significant reporting bias. In four of these models pharmacological profiles allowed to verify similarity to some clinical conditions, and therefore may inform basic research for new drug development.

Conclusions

While there is no single “optimal” model of central sensitization, the range of validated and easy‐to‐use procedures in humans should be able to inform preclinical researchers on helpful potential biomarkers, thereby narrowing the translation gap between basic and clinical data.

Significance

Being able to mimic aspects of pathological pain directly in humans has a huge potential to understand pathophysiology and provide animal research with translatable biomarkers for drug development. One group of human surrogate models has proven to have excellent predictive validity: they respond to clinically active medications and do not respond to clinically inactive medications, including some that worked in animals but failed in the clinics. They should therefore inform basic research for new drug development.

Effects of ketamine versus dexmedetomidine maintenance infusion in posterior spinal fusion surgery on acute postoperative pain

Background:

One of the most challenging issues after posterior spinal fusion (PSF) surgery is providing appropriate pain control measures to enhance recovery of the patients. We aimed to compare effects of ketamine versus dexmedetomidine infusion during maintenance of anesthesia on acute postoperative pain in PSF surgery.

Methods:

In a double-blinded randomized clinical trial, 87 patients candidates for PSF surgery were randomly assigned into three groups. Anesthesia protocol for all groups was the same except: the first group received 0.2 mcg/kg/h dexmedetomidine infusion, the second received 0.1 mg/kg/h ketamine infusion, and control group received normal saline infusion as a placebo. Pain intensity by VAS scale and level of sedation by Ramsey scale were assessed, and amount of opioid prescribed after surgery was measured and compared for patients during the recovery and at 2, 4, 6, 12, and 24 h after surgery in three groups, and hypotension and bradycardia during operation were reported.

Results:

There was a significant difference among the groups regarding pain intensity and amount of opioids during recovery and at 2, 4, 6, 12, and 24 h after surgery. Pain intensity and amount of opioids for ketamine and dexmedetomidine groups were significantly lower than those in the controls during recovery and at the hours after surgery. There was no significant difference regarding bradycardia and hypotension and level of sedation during recovery and at the hours after surgery.

Conclusion:

Both ketamine and dexmedetomidine infusions during maintenance of anesthesia are effective in reducing acute postoperative pain effectively after PSF surgery.

Enhanced Recovery After Cesarean: Current and Emerging Trends

Purpose of Review

What are the latest enhanced recovery elements for cesarean delivery?

Recent Findings

Enhanced recovery after cesarean delivery (ERAC) provides an evidenced-based system to improve maternal outcomes, functional recovery, maternal-infant bonding, and patient experience. Postsurgical recovery has evolved from a one-dimensional pain score to a holistic multidimensional approach emphasizing faster functional recovery. ERAC involves multidisciplinary efforts of the anesthesiologist, obstetrician, nursing, hospital, and patient. Components of ERAC include preoperative patient education, limited fasting, carbohydrate load, limiting opioids intra- and postoperatively, using scheduled non-opioid analgesics and supplementing with advanced therapies for women at higher risk for pain. ERAC protocols reduce opioid consumption, reduce length of stay, and improve maternal and neonatal outcomes.

Summary

Implementing ERAC standardized care will likely be the most important change you can make in your practice to improve outcomes, improve quality care, help address racial disparities, and minimize opioid exposure and potential for addiction.

Challenges and opportunities in translational pain research - An opinion paper of the working group on translational pain research of the European pain federation (EFIC)

For decades, basic research on the underlying mechanisms of nociception has held promise to translate into efficacious treatments for patients with pain. Despite great improvement in the understanding of pain physiology and pathophysiology, translation to novel, effective treatments for acute and chronic pain has however been limited, and they remain an unmet medical need. In this opinion paper bringing together pain researchers from very different disciplines, the opportunities and challenges of translational pain research are discussed. The many factors that may prevent the successful translation of bench observations into useful and effective clinical applications are reviewed, including interspecies differences, limited validity of currently available preclinical disease models of pain, and limitations of currently used methods to assess nociception and pain in non-human and human models of pain. Many paths are explored to address these issues, including the backward translation of observations made in patients and human volunteers into new disease models that are more clinically relevant, improved generalization by taking into account age and sex differences, and the integration of psychobiology into translational pain research. Finally, it is argued that preclinical and clinical stages of developing new treatments for pain can be improved by better preclinical models of pathological pain conditions alongside revised methods to assess treatment-induced effects on nociception in human and non-human animals. Significance: For decades, basic research of the underlying mechanisms of nociception has held promise to translate into efficacious treatments for patients with pain. Despite great improvement in the understanding of pain physiology and pathophysiology, translation to novel, effective treatments for acute and chronic pain has however been limited, and they remain an unmet medical need.

Opioid-Sparing Anesthetic Technique for Pediatric Patients Undergoing Adenoidectomy: A Pilot Study

INTRODUCTION

An opioid-sparing anesthetic involves a multi-modal technique with non-opioid medications targeting different analgesic pathways. Such techniques may decrease adverse effects related to opioids. These techniques may be considered in patients at higher risk for opioid-related adverse effects including obstructive sleep apnea or sleep disordered breathing.

METHODS

A prospective, pilot study was performed in 10 patients (3-8 years of age), presenting for adenoidectomy. The perioperative regimen included oral dextromethorphan (1 mg/kg) and acetaminophen (15 mg/kg) plus single boluses of intraoperative dexmedetomidine (0.5 μg/kg) and ketamine (0.5 mg/kg). Pain scores were assessed in the post anesthesia care unit (PACU) using the FLACC (Face, Legs, Activity, Cry, Consolability) scale. Patients with a pain score >4 received fentanyl as needed. PACU time, pain scores, and parent satisfaction were recorded. Postoperatively, patients were instructed to use oral acetaminophen or ibuprofen every 6 hours as needed for pain.

RESULTS

The study cohort included 10 patients, 3-8 years of age. All patients had opioid-free anesthetic care. PACU time ranged from 24 to 102 minutes (median: 56 minutes). FLACC pain scores were 0 for all PACU assessments. Nine patients were discharged home and 1 patient had a planned overnight admission. Following hospital discharge, the pain scores were satisfactory during the 72-hour study period and 90% of the patients' guardians were satisfied or highly satisfied with their child's pain control.

CONCLUSION

This opioid-sparing approach provided safe and effective pain control as well as parental satisfaction following adenoidectomy in children. Additional prospective studies are needed to determine whether this regimen is effective in a larger cohort of patients with and for other otolaryngology procedures.