Initiating Ketamine in Acutely Suicidal Patients in the Emergency Department

There is a strong corollary between stress and the development of depression and suicidal behaviors. The neurobiological mediators of stress are primarily controlled by the noradrenergic and corticotropin-releasing factor (CRF) median eminence systems. Furthermore, stress directly and indirectly, through the Hypothalamic Pituitary Axis, activates the Locus Coeruleus (LC), which is the primary producer of NE in the central nervous system (CNS). Directly, glutaminergic neurons send excitatory signals to the LC via interaction with N-Methyl-D-Aspartate (NMDA) receptors NMDA antagonists, such as ketamine, can dampen the glutaminergic system, which has been implicated during states of depression and low moods.

The neurobiological commonality between multiple psychiatric disorders and depression, suicide, and attempted suicide is a decrease in serotonergic activity. It has been shown that patients who died of suicide, have decreased serotonin transporter in the ventromedial prefrontal cortex and anterior cingulate, which are areas that control decision making or willful action. The prefrontal cortex is important for inhibitory behavioral control. A potential treatment modality of ketamine, is that it produces activation of this region.35 The anterior cingulate cortex has been shown to be associated with impulsive aggression compared to control. Clinical studies have shown that low CSF 5-HIAA, metabolite in serotonin system, has been implicated and positively correlated to aggression scores and impulsivity. This is interesting because, suicides in the military are thought to have an impulsivity component, triggered by one or more major life stressors.

Another region associated with suicide is the infralimbic cortex. A recent study, based on neuroimaging techniques, demonstrated that glucose metabolism in this region was associated with SI at baseline, and decreases in SI was observed after ketamine infusion. This is the same region target by deep brain stimulation, for depression treatment. Additionally, the infralimbic cortex has been implicated in behavioral flexibility. Implicating that ketamine's anti-suicidal properties may stem from its ability to promoting cognitive flexibility. Most likely due to its ability to increase brain-derived neurotrophic factor (BDNF), which is a major contributor to neuronal plasticity. BDNF also plays key roles in synaptic and long-term potentiation, which may counteract the decreased levels in Mood Disorder (MDD) patients. Furthermore, ketamine infusion has been shown to change sleep slow wave activity. This biomarker is functionally related to increased synaptic strengthening and cortical synchronization. These factors, combined, may be implicated in not only ketamine's antidepressant effects and counteraction of decreased synaptic plasticity seen mood disorders, but also its ability to have week long lasting effects.

This information leads us to hypothesize that treatment of acutely suicidal patients with ketamine would: 1) decrease suicidal ideationto a clinically significant degree, and 2) the effect of ketamine will be seen for as long as one-week post administration.

To the best of our knowledge, this study does not duplicate any ongoing work. Instead, it would strengthen power to past studies and current work. There are four clinical trials investigating ketamine's effect on SI. One has an unknown status. There are two that are investigating ketamine in relationship to psychiatric standard of care, whereas this study is investigating its effects against a saline placebo. Finally, the last clinical trial is investigating the Neurobiology of Suicide. Their phase 2 component, which utilizes a similar protocol, uses ketamine as a tool to identify potential biomarkers for suicide. Furthermore, this study differs from Janssen Research & Development's clinical trial in administration route and study design. Their study focuses on using ketamine through intranasal administration. Their primary outcomes are the long-term safety and efficacy, and the design of their study is an open label multicenter trial.