Nuri Bradford Farber

(R,S)-ketamine (ketamine) and its enantiomer (S)-ketamine (esketamine) can produce rapid and substantial antidepressant effects. However, individual response to ketamine/esketamine is variable, and there are no well-accepted methods to differentiate persons who are more likely to benefit. Numerous potential peripheral biomarkers have been reported, but their current utility is unclear. We conducted a systematic review/meta-analysis examining the association between baseline levels and longitudinal changes in blood-based biomarkers, and response to ketamine/esketamine. Of the 5611 citations identified, 56 manuscripts were included (N = 2801 participants), and 26 were compatible with meta-analytical calculations. Random-effect models were used, and effect sizes were reported as standardized mean differences (SMD). Our assessments revealed that more than 460 individual biomarkers were examined. Frequently studied groups included neurotrophic factors (n = 15), levels of ketamine and ketamine metabolites (n = 13), and inflammatory markers (n = 12). There were no consistent associations between baseline levels of blood-based biomarkers, and response to ketamine. However, in a longitudinal analysis, ketamine responders had statistically significant increases in brain-derived neurotrophic factor (BDNF) when compared to pre-treatment levels (SMD [95% CI] = 0.26 [0.03, 0.48], p = 0.02), whereas non-responders showed no significant changes in BDNF levels (SMD [95% CI] = 0.05 [−0.19, 0.28], p = 0.70). There was no consistent evidence to support any additional longitudinal biomarkers. Findings were inconclusive for esketamine due to the small number of studies (n = 2). Despite a diverse and substantial literature, there is limited evidence that blood-based biomarkers are associated with response to ketamine, and no current evidence of clinical utility.

Background: Postoperative depressive symptoms are associated with pain, readmissions, death, and other undesirable outcomes. Ketamine produces rapid but transient antidepressant effects in the perioperative setting. Longer infusions confer lasting antidepressant activity in patients with treatment-resistant depression, but it is unknown whether a similar approach may produce a lasting antidepressant effect after surgery. This protocol describes a pilot study that will assess the feasibility of conducting a larger scale randomized clinical trial addressing this knowledge gap. Methods: This single-center, double-blind, placebo-controlled pilot trial involves the enrollment of 32 patients aged 18 years or older with a history of depression scheduled for surgery with planned intensive care unit admission. On the first day following surgery and extubation, participants will be randomized to an intravenous eight-hour infusion of either ketamine (0.5 mg kg-1 over 10 minutes followed by a continuous rate of 0.3 mg kg-1 h-1) or an equal volume of normal saline. Depressive symptoms will be quantified using the Montgomery-Asberg Depression Rating Scale preoperatively and serially up to 14 days after the infusion. To detect ketamine-induced changes on overnight sleep architecture, a wireless headband will be used to record electroencephalograms preoperatively, during the study infusion, and after infusion. The primary feasibility endpoints will include the fraction of patients approached who enroll, the fraction of randomized patients who complete the study infusion, and the fraction of randomized patients who complete outcome data collection. Conclusions: This pilot study will evaluate the feasibility of a future large comparative effectiveness trial of ketamine to reduce depressive symptoms in postsurgical patients. Registration: K-PASS is registered on ClinicalTrials.gov: NCT05233566; registered February 10, 2022.

Electroconvulsive therapy (ECT) relies on the electrical induction of generalized seizures to treat major depressive disorder and other psychiatric illnesses. These planned procedures provide a clinically relevant model system for studying neurophysiologic characteristics of generalized seizures. We recently described novel central-positive complexes (CPCs), which were observed during ECT-induced seizures as generalized, high-amplitude waveforms with maximum positive voltage over the vertex. Here, we performed a systematic characterization of 6,928 CPC ictal waveforms recorded in 11 patients undergoing right unilateral (RUL) ECT. Analyses of high-density 65-electrode EEG recordings during these 50 seizures allowed evaluation of these CPCs across temporal, spatial, and spectral domains. Peak-amplitude CPC scalp topology was consistent across seizures, showing maximal positive polarity over the midline fronto-central region and maximal negative polarity over the suborbital regions. Total duration of CPCs positively correlated with the time required for return of responsiveness after ECT treatment ( r = 0.39, p = 0.005). The rate of CPCs showed a frequency decline consistent with an exponential decay (median 0.032 (IQR 0.053) complexes/second). Gamma band (30-80 Hz) oscillations correlated with the peak amplitude of CPCs, which was also reproducible across seizures, with band power declining over time ( r = −0.32, p < 10 ⁻⁷ ). The sources of these peak potentials were localized to the bilateral medial thalamus and cingulate cortical regions. Our findings demonstrated CPC characteristics that were invariant to participant, stimulus charge, time, and agent used to induce general anesthesia during the procedure. Consistent with ictal waveforms of other generalized epilepsy syndromes, CPCs showed topographic distribution over the fronto-central regions, predictable intra-seizure frequency decline, and correlation with gamma-range frequencies. Furthermore, source localization to the medial thalamus was consistent with underlying thalamocortical pathophysiology, as established in generalized epilepsy syndromes. The consistency and reproducibility of CPCs offers a new avenue for studying the dynamics of seizure activity and thalamocortical networks.

Fifteen to thirty percent of patients with major depressive disorder do not respond to antidepressants that target the monoaminergic systems. NMDA antagonists are currently being actively investigated as a treatment for these patients. Ketamine is the most widely studied of the compounds. A brief infusion of a low dose of this agent produces rapid improvement in depressive symptoms that lasts for several days. The improvement occurs after the agent has produced its well characterized psychotomimetic and cognitive side effects. Multiple infusions of the agent (e.g., 2–3× per week for several weeks) provide relief from depressive symptoms, but the symptoms reoccur once the treatment has been stopped. A 96-h infusion of a higher dose using add-on clonidine to mitigate the psychotomimetic effects appears to also provide relief and resulted in about 40% of the subjects still having a good response 8 weeks after the infusion. As this was a pilot study, additional work is needed to confirm and extend this finding. Nitrous oxide also has had positive results. Of the other investigational agents, CERC-301 and rapastinel remain in clinical development. When careful monitoring of neuropsychiatric symptoms has been conducted, these agents all produce similar side effects in the same dose range, indicating that NMDA receptor blockade produces both the wanted and unwanted effects. Research is still needed to determine the appropriate dose, schedule, and ways to mitigate against unwanted side effects of NMDA receptor blockade. These hurdles need to be overcome before ketamine and similar agents can be prescribed routinely to patients.

Electroconvulsive therapy (ECT) employs the elective induction of generalizes seizures as a potent treatment for severe psychiatric illness. As such, ECT provides an opportunity to rigorously study the recovery of consciousness, reconstitution of cognition, and electroencephalographic (EEG) activity following seizures. Fifteen patients with major depressive disorder refractory to pharmacologic therapy will be enrolled (Clinicaltrials.gov, NCT02761330). Adequate seizure duration will be confirmed following right unilateral ECT under etomidate anesthesia. Patients will then undergo randomization for the order in which they will receive three sequential treatments: etomidate + ECT, ketamine + ECT, and ketamine + sham ECT. Sessions will be repeated in the same sequence for a total of six treatments. Before each session, sensorimotor speed, working memory, and executive function will be assessed through a standardized cognitive test battery. After each treatment, the return of purposeful responsiveness to verbal command will be determined. At this point, serial cognitive assessments will begin using the same standardized test battery. The presence of delirium and changes in depression severity will also be ascertained. Sixty-four channel EEG will be acquired throughout baseline, ictal, and postictal epochs. Mixed-effects models will correlate the trajectories of cognitive recovery, clinical outcomes, and EEG metrics over time. This innovative research design will answer whether: (1) time to return of responsiveness will be prolonged with ketamine + ECT compared with ketamine + sham ECT; (2) time of restoration to baseline function in each cognitive domain will take longer after ketamine + ECT than after ketamine + sham ECT; (3) postictal delirium is associated with delayed restoration of baseline function in all cognitive domains; and (4) the sequence of reconstitution of cognitive domains following the three treatments in this study is similar to that occurring after an isoflurane general anesthetic (NCT01911195). Sub-studies will assess the relationships of cognitive recovery to the EEG preceding, concurrent, and following individual ECT sessions. Overall, this study will lead the development of biomarkers for tailoring the cogno-affective recovery of patients undergoing ECT.

Background: While electroconvulsive therapy is widely regarded as a lifesaving and safe procedure, evidence regarding its effects on myocardial cell injury is sparse. The objective of this investigation was to determine the incidence and magnitude of new cardiac troponin elevation after electroconvulsive therapy using a novel high-sensitivity cardiac troponin I assay. Methods: This was a prospective cohort study in adult patients undergoing electroconvulsive therapy in a single academic center (up to three electroconvulsive therapy treatments per patient). The primary outcome was new high-sensitivity cardiac troponin I elevation after electroconvulsive therapy, defined as an increase of high-sensitivity cardiac troponin I greater than 100% after electroconvulsive therapy compared to baseline with at least one value above the limit of quantification (10 ng/l). Twelve-lead electrocardiogram and high-sensitivity cardiac troponin I values were obtained before and 15 to 30 min after electroconvulsive therapy; in a subset of patients, an additional 2-h high-sensitivity cardiac troponin I value was obtained. Results: The final study population was 100 patients and a total of 245 electroconvulsive therapy treatment sessions. Eight patients (8 of 100; 8%) experienced new high-sensitivity cardiac troponin I elevation after electroconvulsive therapy with a cumulative incidence of 3.7% (9 of 245 treatments; one patient had two high-sensitivity cardiac troponin I elevations), two of whom had a non–ST-elevation myocardial infarction (incidence 2 of 245; 0.8%). Median high-sensitivity cardiac troponin I concentrations did not increase significantly after electroconvulsive therapy. Tachycardia and/or elevated systolic blood pressure developed after approximately two thirds of electroconvulsive therapy treatments. Conclusions: Electroconvulsive therapy appears safe from a cardiac standpoint in a large majority of patients. A small subset of patients with preexisting cardiovascular risk factors, however, may develop new cardiac troponin elevation after electroconvulsive therapy, the clinical relevance of which is unclear in the absence of signs of myocardial ischemia.

Objectives: Glucocorticoids (GCs) are used to improve respiratory mechanics in preterm infants despite clinical evidence linking neonatal GC therapy to cerebellar pathology. In developing mouse cerebellum, the GC dexamethasone (DEX) causes rapid GC-induced neural progenitor cell apoptosis (GINA). Focusing on pharmacological neuroprotection strategies, we investigated whether dexmedetomidine (DMT) protects against GINA. Methods: Neonatal mice were pretreated with DMT prior to DEX challenge. Additionally, we tested clonidine and yohimbine in vivo to determine mechanism of DMT neuroprotection. For in vitro studies, cerebellar neural progenitor cells were pretreated with DMT before DEX challenge. Results: In vivo, DMT attenuated GINA at 1 μg/kg and above, p < 0.0001. Clonidine significantly attenuated GINA, p < 0.0001, while yohimbine reversed DMT neuroprotection, p < 0.0001, suggesting DMT neuroprotection is likely mediated via adrenergic signaling. In vitro, DMT neuroprotection was achieved at 10 μM and above, p < 0.001, indicating DMT rescue is cell autonomous. Conclusions: DMT affords dose-dependent neuroprotection from GINA at clinically relevant doses, an effect that is cell autonomous and likely mediated by α2 adrenergic receptor agonism. DMT co-administration with GCs may be an effective strategy to protect the neonatal brain from GINA while retaining the beneficial effects of GCs on respiratory mechanics.

Objectives We examined the feasibility of a high-dose, 96-h infusion of ketamine in treatment-resistant depression. Methods Ten participants were randomised to receive a 96-h ketamine infusion, titrated as tolerated to a target rate of 0.6 mg/kg/h, while 10 received a 40-min ketamine infusion (0.5 mg/kg). Both groups received clonidine, titrated to a maximum of 0.6 mg orally daily, during the infusion to mitigate side effects of ketamine. Participants were followed for 8 weeks to examine potential antidepressant effects. Results All 20 participants completed the infusion. Most participants tolerated the infusion well, with minimal psychotomimetic symptoms or blood pressure elevation despite achieving high ketamine concentrations (mean 424 ng/ml for 96-h arm, 156 ng/ml for 40-min arm). There was no rebound hypertension upon discontinuing clonidine. Rapid and sustained improvement in depressive symptoms was observed in both study groups. Higher ketamine concentration was associated with sustained antidepressant response, and was not with greater psychotomimetic side effects, in the 96-h arm. Conclusions This study provides evidence for the feasibility of prolonged ketamine infusions in treatment-resistant depression. Co-administration of clonidine appeared to mitigate ketamine’s psychotomimetic effects. Further study is required to investigate the extent to which prolonged ketamine infusions could provide both rapid and sustained improvements in treatment-resistant depression. Clinicaltrials.gov identifier NCT01179009