American Society of Regional Anesthesia and Pain Medicine February 2015 - (Page 14)

Ketamine-an Old Drug with New Tricks Many institutions (academic and private practice alike) are starting to develop various protocols and clinical pathways that include ketamine. Ketamine infusions are generally viewed as useful in multimodal perioperative pain management for patients who undergo complex surgeries (eg, spine fusion, median arcuate ligament release) or have a history of opioid tolerance, use, and abuse; in addition, ketamine has been added to many clinical pathway protocols which are integral to the Perioperative Surgical Home model. Magdalena Anitescu, MD, PhD Associate Professor, Department of Anesthesia and Critical Care Program Director, Multidisciplinary Pain Medicine Program Joseph J. Cooper, MD Assistant Professor, Department of Psychiatry and Behavioral Neuroscience Director, Neuropsychiatry and Neuromodulation Services University of Chicago Chicago, Illinois Section Editor: Kevin Vorenkamp, MD M ore than 50 years since its discovery in 1963, ketamine is still an agent that surprises us. While originally marketed as a general anesthetic, its use over the years has expanded to include treatment protocols targeting acute or chronic pain conditions and also psychiatric disease states. Ketamine's mechanisms of analgesic action are the subject of many reviews and are still under investigation. The role of ketamine as an N-methyl-D-aspartate receptor antagonist is well established. Its mechanism of action, however, is not unique and does show interference with many cellular receptors and neurotransmitters, including opioid receptors and monoamine transporters. The fact that ketamine is labeled a "dirty drug" by the research community-meaning that too many interactions with cellular mechanisms precludes isolation of a specific action- seems to have worked to its advantage. Even 50 years after its birth, ketamine continues to surprise the medical community with the ongoing discovery of new clinical indications. Ketamine's role in chronic pain management is not as well defined. Early reports of its use in chronic pain did not appear until the late 1990s,4 and the evidence supporting ketamine use in pain clinics is limited. Studies that have shown efficacy of ketamine for the chronic regional pain syndrome and other chronic pain syndromes, such as central sensitization,5,6 are limited due to heterogeneity of subjects and study design. Some retrospective studies7,8 have shown mixed results. The role of intravenous ketamine as an analgesic in chronic pain states has yet to be thoroughly defined. However, it was during one of those outpatient infusions therapies when antidepressive effects of ketamine were first observed.9 Since then, applications for psychiatric conditions have been emerging (Table 1), with increasing evidence to support its use, especially in acute and severe refractory depression. Early studies comparing intravenous ketamine infusions at subanesthetic doses to saline infusions have shown rapid antidepressant benefit with onset within hours.9,10 When compared to the response time of several weeks for standard antidepressants-or at least several days with electroconvulsive therapy (ECT)- improvement measured in hours represents a potential paradigm shift in the treatment of depression and has generated understandable enthusiasm. Follow-up studies have generally confirmed response rates of 25-71% at 24 hours and 14-50% of subjects at 72 hours postinfusion for both unipolar and bipolar depression,11 but the effect is lost beyond 7 days postinfusion. "Even 50 years after its birth, ketamine continues to surprise the medical community with the ongoing discovery of new clinical indications." In the current opioid epidemic, ketamine has been a savior for the many situations when patients on chronic high-dose opioids undergo surgery. Its intraoperative use in neurosurgical and orthopedic procedures as well as abdominal surgeries1-3 has been increasing. 14 2 While suicidal thoughts occur most commonly with depression, they are also present in other psychiatric disorders. One of the most intriguing uses of ketamine in psychiatry is for the reduction of suicidal ideation independent of decreased depressive and anxiety symptoms.12 Following ketamine infusions, patients report increased "wish to live" and decreased "wish to die" effects that start at 40 minutes and last for 3 days post-treatment.13 American Society of Regional Anesthesia and Pain Medicine 2015

Table of Contents for the Digital Edition of American Society of Regional Anesthesia and Pain Medicine February 2015

In Memoriam : Alon Palm Winnie, M.D., ASRA Founding Father
President’s Message
40th Annual Regional Anesthesiology and Acute Pain Medicine Meeting
Resident and Fellow Events at the 2015 Spring Meeting
How We Do It: Managing an Acute and Perioperative Pain Medicine (APPM) Service at the University of Florida
Ketamine—an Old Drug with New Tricks
Optimal Postcesarean Delivery Pain Management
Palliative Care and Pain Medicine—Beyond Intrathecal Pumps and Opioids
Scientist Spotlight—Dr. Guy Weinberg, Trailblazer in Patient Safety

American Society of Regional Anesthesia and Pain Medicine February 2015