Effect of butorphanol on etomidate-induced myoclonus: a systematic review and meta-analysis

The Application and Pharmaceutical Development of Etomidate: Challenges and Strategies

Etomidate is a synthetic imidazole anesthetic that exerts hypnotic effects by potentiating the action of the inhibitory neurotransmitter γ-aminobutyric acid (GABA) or directly activating the anionic GABA (GABAA) receptor. It stands out among many anesthetics because of its multiple advantages, such as good hemodynamic stability and minimal inhibition of spontaneous respiration. However, its low water solubility and side effects, such as adrenal cortex inhibition and myoclonus, have limited the clinical application of this drug. To address these issues, extensive research has been conducted on the drug delivery of etomidate in recent decades, which has led to the emergence of different etomidate preparations. Despite so many etomidate preparations, so far some of the toxic side effects have not yet been effectively addressed. Herein we discuss the pharmaceutical design of etomidate that may resolve the above problem. We also propose targeted strategies for future research on etomidate preparations and discuss the feasibility of different administration routes and dosage forms to expand the application of this drug. Through this review, we hope to draw more attention to the potential of etomidate and its application challenges and provide valuable insights into the development of new etomidate preparations.

Dexamethasone alleviates etomidate-induced myoclonus by reversing the inhibition of excitatory amino acid transporters

Background

Etomidate can induce myoclonus with an incidence of 50 ~ 85% during anesthesia induction. Dexamethasone, as a long-acting synthetic glucocorticoid, has neuroprotective effects. However, the effects of dexamethasone on the etomidate-induced myoclonus remain uncertain.

Methods

Adult male Sprague-Dawley rats were randomly assigned to receive etomidate (1.5 mg/kg) plus dexamethasone (4 mg/kg) (etomidate plus dexamethasone group) or etomidate (1.5 mg/kg) plus the same volume of normal saline (NS) (etomidate plus NS group). The mean behavioral scores, local field potentials and muscular tension were recorded to explore the effects of dexamethasone on etomidate-induced myoclonus. Liquid chromatography coupled with tandem mass spectrometric system (LC-MS/MS), quantitative real-time polymerase chain reaction (qRT-PCR), and western blotting were applied to analyze the levels of glutamate and γ-aminobutyric acid (GABA), the mRNA and protein expression of excitatory amino acid transporters (EAATs), and plasma corticosterone levels at different time points after anesthesia.

Results

Compared with the etomidate plus NS treatment, the etomidate plus dexamethasone treatment significantly decreased the mean behavioral score at 1, 3, 4, and 5 min after administration; the peak power spectral density (PSD) (p = 0.0197) in the analysis of ripple waves; and the glutamate level (p = 0.0139) in the neocortex. However, compared with etomidate plus NS, etomidate plus dexamethasone increased the expression of the neocortical proteins of EAAT1 (p = 0.0207) and EAAT2 (p = 0.0022) and aggravated the inhibition of corticosterone at 4 h (p = 0.0019), 5 h (p = 0.0041), and 6 h (p = 0.0009) after administration.

Conclusion

Dexamethasone can attenuate the myoclonus, inhibit the glutamate accumulation, and reverse the suppression of EAATs in the neocortex induced by etomidate following myoclonus, while conversely aggravating etomidate-induced adrenal suppression.

Pharmacological interventions for reducing the incidence of myoclonus in patients receiving etomidate for induction of general anesthesia: an umbrella review

OBJECTIVE

The objective of this umbrella review was to examine various pharmacologic interventions for their potential to reduce etomidate-induced myoclonus. A secondary objective was to compare the relative effectiveness of those medications in reducing the incidence of myoclonus when etomidate is utilized for the induction of general anesthesia.

INTRODUCTION

Etomidate is the drug of choice when inducing general anesthesia in hemodynamically unstable patients. However, its use is limited among the general surgical population due to its ability to cause adrenal suppression, vomiting, and myoclonus. Myoclonus can lead to damage of muscle fibers, myalgias, and patient discomfort, and can also be detrimental in patients with low cardiac reserve. Several systematic reviews have reported on the effectiveness of various intravenous medications in reducing mild, moderate, and severe myoclonus; however, a more thorough examination of their influence was lacking.

INCLUSION CRITERIA

This review included systematic reviews and meta-analyses of randomized controlled trials involving the use of pharmacologic interventions to reduce etomidate-induced myoclonus. Reviews in English and conducted after 1965 were considered for inclusion.

METHODS

A comprehensive search of 11 databases was conducted to identify published and unpublished reviews up to March 2022. Critical appraisal was conducted by 2 independent reviewers using the standardized JBI appraisal tool. Quantitative findings were summarized according to the dose, timing of administration, and relative risk using a data matrix, and were synthesized in tabular format with supporting narrative text. Results were organized by severity of myoclonus (overall, mild, moderate, and severe) and by type of intervention.

RESULTS

Eight systematic reviews were included in this umbrella review, which included 48 relevant studies, after removal of duplicates (3909 participants included in the primary studies). Five of the systematic reviews examined the effectiveness of various types of opioids in the prevention of myoclonus, and 3 systematic reviews examined the effectiveness of non-opioid interventions, such as lidocaine, midazolam, and dexmedetomidine. Seven reviews searched at least 4 databases for pertinent studies and specifically indicated that blinded reviewers appraised the articles. All reviews used a published and validated appraisal instrument. The overall quality of all included reviews was judged to be moderate to high. The absolute risk reduction indicating the effectiveness of the prophylactic medications ranged from 47% to 81% for mild, 52% to 92% for moderate, and 61% to 96% for severe myoclonus. Opioids demonstrated the most consistent and substantial effect on the reduction in myoclonus.

CONCLUSIONS

All pharmacologic interventions identified in this review demonstrated a statistically significant reduction in the incidence of myoclonus. Future studies and reviews should focus on elucidating the particular dose range and timing that is most effective. Anesthesia providers should consider a pre-treatment dose of one of the medications described in this umbrella review as a means to reduce myoclonus and the untoward effects of that condition.

Comparative assessment of dexmedetomidine and butorphanol for attenuation of etomidate-induced myoclonus: A double-blind, randomised controlled study

Background and Aims

Etomidate is a popular induction agent, but its use is associated with myoclonus in 50%-80% of non-premedicated patients. This study aims to compare dexmedetomidine and butorphanol for their relative efficacy in preventing etomidate-induced myoclonus.

Methods

This randomised study was conducted after obtaining institutional ethical committee clearance and written informed consent from sixty American Society of Anesthesiologists (ASA) I or II consenting patients between 18 and 60 years of age of either sex who had been scheduled for elective surgeries under general anaesthesia. Patients were randomly allocated to dexmedetomidine 0.5 μg/kg (Group D) or butorphanol 0.015 mg/kg (Group B). Both the drugs were given as an infusion over a period of 10 min before induction of anaesthesia. The primary outcome was the incidence of myoclonic movements after etomidate, and the secondary outcomes were the severity of myoclonus, changes in the haemodynamic parameters and incidence of airway complications. Normally distributed variables were compared using Student's t-test, and non-normally distributed variables were compared using Mann-Whitney U test. Qualitative data were analysed using Chi-square/Fisher's exact test. A P-value <0.05 was considered significant.

Results

The incidence of etomidate-induced myoclonus was significantly higher in group B compared to group D (P = 0.035). The median (interquartile range [IQR]) of myoclonus grade in patients of group D was 0.00 (0.00-3.00), and group B was 2.50 (0.00-3.00) (P = 0.035). Haemodynamics and airway-related complications were comparable between the groups.

Conclusion

Dexmedetomidine was more effective than butorphanol in preventing etomidate-induced myoclonus.

Etomidate affects spatial learning and memory and neuronal apoptosis of rats via MAPK/ERK pathway

OBJECTIVE

To observe the effect of etomidate on spatial learning and memory and neuronal apoptosis in rats of different ages.

METHODS

The rats of different ages were divided into 3 age groups: juvenile (21-day old), adult (~3-months old) and elderly (~19-months old). Then, rats with similar age within a group were randomly divided into three subgroups, with 10 rats in each group. The experimental subgroups were intraperitoneally injected with etomidate (emulsion formulated, i.p. injection) at a dose of 5 mg/kg; the solvent control subgroups were given intraperitoneal injection of vehicle emulsion; and blank control subgroups received laparoscopic injection of normal saline. The rats' learning and memory ability was tested by Morris water maze. The tissue sections of each group's hippocampus were analyzed by H&E staining. The apoptosis of hippocampal cells was detected by TUNEL staining. MAPK expression in hippocampus was tested by Western blot.

RESULTS

Etomidate significantly extended the escape latency and reduced the platform crossings and the swimming time at original platform of juvenile rats, indicating that the spatial learning and memory function of juvenile rats can be affected by etomidate. However, etomidate had no effect on spatial learning and memory in adult and elderly rats. There were no obvious abnormalities in number of neurons and morphology of vertebral cells in the hippocampus of all experimental subgroups when compared with those of corresponding blank control subgroups. There was no statistically significant difference in apoptosis index of the hippocampal tissue between the experimental subgroups and corresponding blank control subgroups (P>0.05). Within juvenile group, the expression of p-ERK in the hippocampus of experimental subgroup was remarkably lower than that of solvent control subgroup and blank control subgroup (P<0.05), while there were no significant differences in p-p38 and p-JNK expressions among the three subgroups of juvenile rats (P>0.05). The expressions of p-ERK, p-p38 and p-JNK in adult and elderly rats were not affected by etomidate.

CONCLUSION

Etomidate may have certain effects on spatial learning and memory in juvenile rats but not in adult and elderly rats. Etomidate affects neither the number of neurons in the CA1 area of the hippocampus nor the morphology of vertebral cells and did not cause the apoptosis of nerve cells. The mechanism of etomidate influence on the spatial learning and memory function of young rats may connect with the inhibition of MAPK/ERK pathway.

Comparison of the Effectiveness of Various Drug Interventions to Prevent Etomidate-Induced Myoclonus: A Bayesian Network Meta-Analysis

Background

Myoclonic movement is a very common but undesirable phenomenon during the induction of general anesthesia using etomidate. Such movement may cause unnecessary problems. Currently, there is an increasing number of drugs for preventing etomidate-induced myoclonus (EM). However, direct comparisons of various drugs are lacking, and this interferes with clinical decision-making. Our network meta-analysis (NMA) aimed to compare the efficacy of different drugs for the prevention of moderate-to-severe general myoclonus.

Methods

Using several biomedical databases, randomized controlled trials (RCTs) published in English from inception to August 22, 2021 were searched. Among the various interventions, we selected nine types of intervention drugs (dexmedetomidine, etomidate, lidocaine, NMDA receptor antagonist, κ opioid receptor agonist, μ opioid receptor agonist, muscle relaxant, gabapentin, and midazolam) for comparison, according to the number of studies. Bayesian NMA was performed using STATA16 and R softwares. The relative risk of EM was assessed using risk ratios (RRs) and the corresponding 95% confidence intervals (CI).

Results

A total of 31 RCTs (3209 patients) were included. NMA results showed that, compared with a placebo, etomidate (RR 4.0, 95%CI 2.1–7.8), κ opioid receptor agonist (RR 2.9, 95%CI 1.9–4.6), μ opioid receptor agonist (RR 3.1, 95%CI 2.3–4.3), NMDA receptor antagonist (RR 1.7, 95%CI 1.0–2.8), dexmedetomidine (RR 2.4, 95%CI 1.5–3.9), lidocaine (RR 2.1, 95%CI 1.2–3.9), and midazolam (RR 2.2, 95%CI 1.5–3.2) can significantly reduce the risk of EM. In contrast, the effects of muscle relaxants (RR 2.1, 95%CI 0.81–5.3) and gabapentin (RR 2.8, 95%CI 0.92–9.3) were inconclusive. Further subgroup analyses showed that preoperative low-dose etomidate, μ-opioid receptor agonist, and κ-opioid receptor agonist were significantly better than other interventions in the prevention of moderate to severe EM.

Conclusion

Preoperative use of small doses of etomidate or opioids may be the most effective way to avoid EM, especially moderate and severe EM, which makes anesthesia induction safer, more stable, and aligns better with the requirements of comfortable medicine.

Systematic Review Registration

[https://www.crd.york.ac.uk/prospero/], [CRD4202127706].

Butorphanol alleviates lipopolysaccharide-induced inflammation and apoptosis of cardiomyocytes via activation of the κ-opioid receptor

Sepsis-induced myocardial dysfunction is a leading cause of the high mortality rates associated with sepsis. The aim of the present study was to investigate the effect of butorphanol on sepsis-induced cardiomyocyte dysfunction. Lipopolysaccharide (LPS) was used to induce H9C2 cardiomyocytes to establish an in vitro sepsis model. The effect of butorphanol on the viability of LPS-induced H9C2 cells was analyzed using a Cell Counting Kit-8 assay. The levels of tumor necrosis factor-α, interleukin (IL)-1β and IL-6 were detected using ELISA. Western blotting was used to analyze the expression levels of inflammation-and apoptosis-related proteins. Cell apoptosis was measured using a TUNEL assay. The expression levels of κ-opioid receptor (KOR) were analyzed using reverse transcription-quantitative PCR analysis and western blotting. Following LPS induction, the levels of inflammatory cytokines and proapoptotic proteins were found to be upregulated in H9C2 cells, while butorphanol treatment downregulated these levels. The expression levels of KOR were also upregulated following butorphanol treatment in LPS-induced H9C2 cells. Addition of the KOR inhibitor, nor-binaltorphimine, alleviated the inhibitory effects of butorphanol on inflammation and apoptosis in LPS-induced H9C2 cells. In conclusion, the findings of the present study provided evidence indicating that butorphanol may alleviate LPS-induced inflammation and apoptosis in cardiomyocytes by upregulating KOR expression, which may provide a novel insight into the potential therapeutic effects of butorphanol and its underlying mechanism of action.

Anesthetic Induction With Etomidate in Cardiac Surgical Patients: A PRISMA-Compliant Systematic Review and Meta-Analysis

OBJECTIVE

This meta-analysis aimed to systematically review the effects of etomidate (ETM) during anesthetic induction on patients undergoing cardiac surgery.

DESIGN

Systematic review and meta-analysis.

SETTING

Operating room.

PARTICIPANTS

Patients undergoing cardiac surgery.

INTERVENTIONS

ETM or control drugs.

MEASUREMENTS AND MAIN RESULTS

PubMed, Cochrane Library, OVID, and EMBASE were searched through August 31, 2020. Primary outcomes included hemodynamic profiles and stress responses. Secondary outcomes included morbidity, mortality, and postoperative recovery. For continuous/dichotomous variables, treatment effects were calculated as weighted mean difference (WMD)/odds ratio (OR) and 95% confidence interval (CI). A database search yielded 18 randomized controlled trials including 1,241 patients. The present meta-analysis demonstrated that ETM-anesthetized patients had lower heart rates (WMD, -3.31; 95% CI -5.43 to -1.19; p = 0.002), higher blood pressures (systolic blood pressure: WMD, 12.02; 95% CI 6.24 to 17.80; p < 0.0001; diastolic blood pressure: WMD, 5.23; 95% CI 2.39 to 8.08; p = 0.0003; mean arterial pressure (MAP): WMD, 8.64; 95% CI 5.85 to 11.43; p < 0.00001), less requirement for vasopressor (OR, 0.26; 95% CI 0.15 to 0.44; p < 0.00001), and more nitroglycerin usage (OR, 14.89; 95% CI 4.92 to 45.08; p < 0.00001) during anesthetic induction. Current meta-analysis also demonstrated that single-dose ETM lowered cortisol levels transiently and did not have a significant effect on endogenous norepinephrine and epinephrine levels and was not associated with increased postoperative inotrope and/or vasopressor requirement. Additionally, the meta-analysis suggested that ETM anesthesia was associated with neither increased mortality nor morbidity, except a higher incidence of transient adrenal insufficiency in ETM recipients.

CONCLUSION

The present meta-analysis suggested that single-dose ETM during anesthetic induction could be associated with more stable hemodynamics, transient and reversible lower cortisol levels, and a higher adrenal insufficiency incidence, but not worse outcomes in cardiac surgical patients.