The Enigma of Low-Dose Ketamine for Treatment of Opioid-Induced Hyperalgesia in the Setting of Psychosocial Suffering and Cancer-Associated Pain

Comparison of the Effect of Intravenous Fentanyl with Low-Dose Ketamine on Pain Relief in Patients Taking Methadone and Suffering from Limb Fractures

Background

Given the significance of pain control in addicted patients and the prominence of not using opioids due to patient's drug dependence, the present study aimed at comparing and evaluating the effect of intravenous fentanyl with low-dose ketamine on pain relief in patients taking methadone and suffering from limb fractures.

Materials and Methods

The present double-blind randomized clinical trial was performed on 100 patients taking methadone and suffering from limb fractures. The patients were divided into two groups receiving 1 μg/kg single dose of fentanyl and 0.3 mg/kg single dose of ketamine (low-dose ketamine). Patients' pain scores and the incidence rate of complications were recorded before the intervention, and 15, 30, and 60 min after drug administration and were then compared between the two groups.

Results

The mean pain score of patients 15 min after the intervention was significantly lower in the low-dose ketamine group with a mean of 2.50 ± 1.34 as compared with the fentanyl group with a mean of 7.10 ± 1.43 (P < 0.001). However, the mean pain score was not significantly different between the two groups 30 and 60 min after the intervention (P > 0.05). In addition, the incidence rate of complications was not significantly different between the two groups (P > 0.05).

Conclusion

According to the results of this study, low-dose ketamine as compared with fentanyl relieves pain in the mentioned patients with a faster effect and in a shorter time although no difference can be found between the pain scores of the two groups 30 and 60 min after the intervention.

Ketamine Compared With Fentanyl for Surgical Abortion: A Randomized Controlled Trial

OBJECTIVE

To compare patient satisfaction with anesthesia after first-trimester surgical abortion among patients receiving intravenous (IV) ketamine compared with IV fentanyl for procedural sedation.

METHODS

This was a randomized noninferiority trial comparing IV ketamine to IV fentanyl for first-trimester surgical abortion up to 13 6/7 weeks of gestation. Patients were randomized to receive either ketamine 200-500 micrograms/kg IV over 2 minutes, repeated every 5 minutes until appropriate analgesia was achieved, or fentanyl 0.5-1 micrograms/kg IV over 2 minutes, repeated every 5 minutes until appropriate analgesia was achieved. All patients received midazolam 2 mg IV. The primary outcome, patient satisfaction, was measured using the Iowa Satisfaction with Anesthesia Scale immediately postprocedure. Secondary outcomes included postoperative pain, additional pain medication necessary during the procedure and on discharge, physician satisfaction, and time to discharge. We calculated a sample size of 84 with a noninferiority margin of 0.6 on the Iowa Satisfaction with Anesthesia Scale with 80% power, one-sided type 1 error of 0.025, and further increased this number to 110 to account for potential dropout.

RESULTS

From April to October 2021, 184 patients were screened and 110 were randomized (57 to ketamine and 53 to fentanyl). Demographics were similar between groups. The primary outcome, patient satisfaction with anesthesia, was noninferior in the ketamine group (mean score 2.4, SD 0.8) as compared with the fentanyl group (mean score 2.2, SD 0.9) with a risk difference of 0.20 (95% CI 0.11-0.52). More hallucinations were reported in the ketamine group. Otherwise, secondary outcomes were similar between the groups.

CONCLUSION

Compared with IV fentanyl, IV ketamine is noninferior for patient satisfaction with anesthesia when used for procedural sedation for first-trimester outpatient surgical abortion.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov , NCT04871425.

Research advances in the clinical application of esketamine

Esketamine is dextrorotatory ketamine, which is an enantiomer of ketamine. Compared with ketamine, it has the advantages of a fast metabolism, fewer side effects, and strong pharmacological effects, so it is more suitable for clinical use. Esketamine has a powerful analgesic effect and has little effect on breathing. It has a wide range of applications in the fields of pediatric anesthesia, conscious sedation anesthesia, and emergency analgesia. In addition, it is also used for pain that is difficult to relieve with conventional drugs and to prevent postoperative pain. Various routes of administration are also suitable for patients who need short-term analgesia and sedation. As a drug, esketamine inevitably brings some side effects when it is used clinically. In this article, by introducing the mechanism of action and pharmacological characteristics of esketamine, its clinical application is reviewed, and it provides a reference for the more reasonable and safe clinical application of esketamine.

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.