Neurotoxicity of ketamine: Known unknowns*

Neurological Effects of Stimulants and Hallucinogens

In this article, we will discuss the history, pharmacodynamics, and neurotoxicity of psychostimulants and hallucinogens. The drugs discussed are widely used and have characteristic toxidromes and potential for neurological injuries with which the practicing clinician should be familiar. Psychostimulants are a class of drugs that includes cocaine, methamphetamine/amphetamines, and cathinones, among others, which produce a crescendoing euphoric high. Seizures, ischemic and hemorrhagic strokes, rhabdomyolysis, and a variety of movement disorders are commonly encountered in this class. Hallucinogens encompass a broad class of drugs, in which the user experiences hallucinations, altered sensorium, distorted perception, and cognitive dysfunction. The experience can be unpredictable and dysphoric, creating a profound sense of anxiety and panic in some cases. Recognizing the associated neurotoxicities and understanding the appropriate management is critical in caring for these patient populations. Several of these agents are not detectable by standard clinical laboratory analysis, making identification and diagnosis an even greater challenge.

Ketamine impairs growth cone and synaptogenesis in human GABAergic projection neurons via GSK-3β and HDAC6 signaling

The growth cone guides the axon or dendrite of striatal GABAergic projection neurons that protrude into the midbrain and cortex and form complex neuronal circuits and synaptic networks in a developing brain, aberrant projections and synaptic connections in the striatum related to multiple brain disorders. Previously, we showed that ketamine, an anesthetic, reduced dendritic growth, dendritic branches, and spine density in human striatal GABAergic neurons. However, whether ketamine affects the growth cone, the synaptic connection of growing striatal GABAergic neurons has not been tested. Using human GABAergic projection neurons derived from human inducible pluripotent stem cells (hiPSCs) and embryonic stem cells (ES) in vitro, we tested ketamine effects on the growth cones and synapses in developing GABAergic neurons by assessing the morphometry and the glycogen synthase kinase-3 (GSK-3) and histone deacetylase 6 (HDAC6) pathway. Ketamine exposure impairs growth cone formation, synaptogenesis, dendritic development, and maturation via ketamine-mediated activation of GSK-3 pathways and inhibiting HDAC6, an essential stabilizing protein for dendritic morphogenesis and synapse maturation. Our findings identified a novel ketamine neurotoxic pathway that depends on GSK-3β and HDAC6 signaling, suggesting that microtubule acetylation is a potential target for reducing ketamine's toxic effect on GABAergic projection neuronal development.

Ketamine-assisted psychotherapy in adolescents with multiple psychiatric diagnoses

Ketamine-assisted psychotherapy is a promising new treatment for a variety of mental disorders of adolescence. There is currently an adolescent mental health crisis, with a high prevalence of disorders, diagnostic complexity, and many adolescents failing to respond to conventional treatments. While there is strong evidence for the use of ketamine in adults for a variety of treatment-refractory mental illnesses, research in adolescents is in its early stages. Ketamine-assisted psychotherapy (KAP) has been described in adults with promising results and here we present the first published cases of the use of KAP in adolescents. The four cases include adolescents aged 14-19 at the initiation of treatment, each with a variety of comorbid diagnoses including treatment-resistant depression, bipolar disorder, eating disorders, anxiety, panic, and trauma-related symptoms. They each initially received sublingual ketamine, followed by sessions with intramuscular ketamine. Their courses varied, but each had symptomatic and functional improvements, and the treatment was well-tolerated. Subjective patient reports are included. Rapid resolution of symptomatology and suffering often occurs within months as the result of the application of KAP to adolescent psychiatric care but is not inevitable. Family involvement in the treatment process appears to be essential to success. The development of this modality may have a singularly positive impact that will expand the psychiatric toolbox and its healing potency.

Parental Attitudes Toward Use of Ketamine in Adolescent Mood Disorders and Suicidality

Objectives: Investigation into parental decision-making processes involving ketamine is of high priority, given the necessary role of parents in consenting to treatment. In this study, we examined parental attitudes toward the emerging use of ketamine in adolescent mood disorders and suicidality. Methods: Two hundred eighty-three English-speaking parents completed an online survey using Amazon Mechanical Turk on psychiatric use of ketamine, acceptability of treatment, and their perceptions of ketamine treatment. Data quality control measures were used to mitigate invalid reporting. Results: Parents reported high acceptability toward use of ketamine for suicidality, major depressive disorder, and bipolar disorder in adolescents. Primary concerns around ketamine involved its potential side effects and lack of United States Food and Drug Administration (FDA) approval. Responses indicated a preference for short-term applications and less invasive routes of administration for ketamine. Parent history of mental illness, familiarity with psychological treatments, and comfort using other mental health interventions in their children predicted greater acceptability of ketamine. Conclusion: Although ketamine is not currently approved by the FDA for psychiatric use in children nor recommended outside of research protocols, these findings suggest that parents have interest in the application of ketamine as a treatment for pediatric mood disorders and point to future directions for research and clinical orientation.

Ketamine for Acute Pain Management and Sedation

TOPIC

Ketamine is beneficial in clinical settings ranging from procedural sedation to the treatment of chronic pain. This article describes the clinical benefits of ketamine for treatment of acute pain and for sedation of patients undergoing mechanical ventilation.

CLINICAL RELEVANCE

Ketamine causes analgesic and amnestic effects by noncompetitive inhibition of the N-methyl-D-aspartate receptor and activation of the opioid μ and κ receptors. Unlike other sedatives, ketamine provides analgesia and amnesia without causing hypotension or respiratory depression. Several studies have elucidated the clinical benefits of ketamine. The use of ketamine has extended beyond critical care areas such as the operating room and intensive care units. Nurses must be familiar with optimal clinical scenarios, monitoring parameters, and contraindications of ketamine.

PURPOSE

To highlight the clinical utility and pharmacological properties of ketamine through a literature review. Current studies of ketamine in acute pain and sedation management are summarized.

CONTENT COVERED

This narrative review describes pharmacological properties, dosing strategies, adminis-tration considerations, and adverse effects of ketamine.

Clinical Practice Guidelines for the Prevention and Management of Pain, Agitation/Sedation, Delirium, Immobility, and Sleep Disruption in Adult Patients in the ICU

OBJECTIVE

To update and expand the 2013 Clinical Practice Guidelines for the Management of Pain, Agitation, and Delirium in Adult Patients in the ICU.

DESIGN

Thirty-two international experts, four methodologists, and four critical illness survivors met virtually at least monthly. All section groups gathered face-to-face at annual Society of Critical Care Medicine congresses; virtual connections included those unable to attend. A formal conflict of interest policy was developed a priori and enforced throughout the process. Teleconferences and electronic discussions among subgroups and whole panel were part of the guidelines' development. A general content review was completed face-to-face by all panel members in January 2017.

METHODS

Content experts, methodologists, and ICU survivors were represented in each of the five sections of the guidelines: Pain, Agitation/sedation, Delirium, Immobility (mobilization/rehabilitation), and Sleep (disruption). Each section created Population, Intervention, Comparison, and Outcome, and nonactionable, descriptive questions based on perceived clinical relevance. The guideline group then voted their ranking, and patients prioritized their importance. For each Population, Intervention, Comparison, and Outcome question, sections searched the best available evidence, determined its quality, and formulated recommendations as "strong," "conditional," or "good" practice statements based on Grading of Recommendations Assessment, Development and Evaluation principles. In addition, evidence gaps and clinical caveats were explicitly identified.

RESULTS

The Pain, Agitation/Sedation, Delirium, Immobility (mobilization/rehabilitation), and Sleep (disruption) panel issued 37 recommendations (three strong and 34 conditional), two good practice statements, and 32 ungraded, nonactionable statements. Three questions from the patient-centered prioritized question list remained without recommendation.

CONCLUSIONS

We found substantial agreement among a large, interdisciplinary cohort of international experts regarding evidence supporting recommendations, and the remaining literature gaps in the assessment, prevention, and treatment of Pain, Agitation/sedation, Delirium, Immobility (mobilization/rehabilitation), and Sleep (disruption) in critically ill adults. Highlighting this evidence and the research needs will improve Pain, Agitation/sedation, Delirium, Immobility (mobilization/rehabilitation), and Sleep (disruption) management and provide the foundation for improved outcomes and science in this vulnerable population.

Beyond Opioids for Pain Management in Adult Critically Ill Patients

Critically ill patients commonly experience pain, and the provision of analgesia is an essential component of intensive care unit (ICU) care. Opioids are the mainstay of pain management in the ICU but are limited by their adverse effects, risk of addiction and abuse, and recent drug shortages of injectable formulations. A multimodal analgesia approach, utilizing nonopioid analgesics as adjuncts to opioid therapy, is recommended since they may modulate the pain response and reduce opioid requirements by acting on multiple pain mediators. Nonopioid analgesics discussed in detail in this article are acetaminophen, α-2 receptor agonists, gabapentinoids, ketamine, lidocaine, and nonsteroidal anti-inflammatory drugs. This literature review describes the clinical pharmacology, supportive ICU and relevant non-ICU data, and practical considerations associated with the administration of nonopioid analgesics in critically ill adult patients.

Ketamine-induced neurotoxicity blocked by N-Methyl-d-aspartate is mediated through activation of PKC/ERK pathway in developing hippocampal neurons

Ketamine, a non-competitive N-methyl d-aspartate (NMDA) receptor antagonist, is widely used in pediatric clinical practice. However, prolonged exposure to ketamine results in widespread anesthetic neurotoxicity and long-term neurocognitive deficits. The molecular mechanisms that underlie this important event are poorly understood. We investigated effects of anesthetic ketamine on neuroapoptosis and further explored role of NMDA receptors in ketamine-induced neurotoxicity. Here we demonstrate that ketamine induces activation of cell cycle entry, resulting in cycle-related neuronal apoptosis. On the other hand, ketamine administration alters early and late apoptosis of cultured hippocampus neurons by inhibiting PKC/ERK pathway, whereas excitatory NMDA receptor activation reverses these effects. Ketamine-induced neurotoxicity blocked by NMDA is mediated through activation of PKC/ERK pathway in developing hippocampal neurons.

Regional anesthesia in neonates and infants

Optimal pain management can significantly impact the surgical outcome and length of stay in the neonatal intensive care unit (NICU). Regional anesthesia is an effective alternative that can be used in both term and preterm neonates. A variety of neuraxial and peripheral nerve blocks have been used for specific surgical and NICU procedures. Ultrasound guidance has increased the feasibility of using these techniques in neonates. Education and training staff in the use of continuous epidural infusions are important prerequisites for successful implementation of regional anesthesia in NICU management protocols.

An update on pediatric hospital-based sedation

PURPOSE OF REVIEW

The need for sedation for procedures performed outside the operating room has increased dramatically, and pediatric procedural sedation (PPS) is increasingly performed by practitioners who are not anesthesiologists. With 'sedationists' emerging from various specialties, there are differences in practice and guidelines with regards to presedation assessment, targeted depths of sedation, monitoring requirements, and the training required. Our aim is to identify some of the recent advances in PPS and to describe progress towards greater standardization of practice.

RECENT FINDINGS

Several studies report attempts to optimize the efficacy of specific pharmaceuticals used in PPS. Ketamine, a dissociative agent, functions uniquely and requires its own sedation practice guidelines. Utilizing less invasive administration of sedation via transmucosal and inhaled routes is gaining popularity. Additionally, replacing subjective measurement of depths of the sedation continuum and the nonstandardized definitions of adverse events with alternatives based on physiological parameters and/or required rescue interventions is underway. Finally, the use of presedation family-centered counseling and adjuncts that provide visual and auditory distraction are enhancing pharmaceutical methods.

SUMMARY

Further multispecialty collaboration and formation of greater consensus with regards to sedation practice are essential to the development of universal guidelines that optimize patient care.