Subdissociative-dose Ketamine Is Effective for Treating Acute Exacerbations of Chronic Pain

Use of Ketamine in Patients with Multifactorial Neuropathic Pain: A Systematic Review and Meta-Analysis

Neuropathic pain (NP) is a heterogeneous group of conditions characterized by the experience of a number of sensory disturbances including pain, burning sensations, paroxysms of stabbing pain, dysesthesias, allodynia, and hyperalgesia. The above-mentioned sensations may occur in a specific dermatome area or other delimited region of the body. The objective of this review was to analyze the evidence for ketamine in multifactorial neuropathic pain. The research group systematically searched the databases MEDLINE (via PubMed), EMBASE, SCOPUS, the Cochrane Central Register of Controlled Trials, the Cumulative Index to Nursing and Allied Health Literature (Cinahl), and the Web of Science. The findings of this review show that different forms of low doses of ketamine (LDK) do not present statistically significant changes for any of the scales included. In this study, the total symptom score [standardized mean difference (SMD) = -3.59, confidence interval (CI) = -4.16 to -3.02, and p < 0.00001], neuropathy impairment score (SMD = -1.42, CI = -3.68 to 0.84, and p = 0.22), and neuropathy symptom checklist (SMD = -0.09, CI = -0.15 to -0.02, and p = 0.01) were taken into account. For finality compared to the use of a placebo, the findings suggest that LDK does not exhibit significant differences in terms of pain reduction and functionality. Moreover, no specific dosages are identified to support the use of LDK in the reduction in NP.

Emerging innovation in pain medicines

The treatment of pain remains a critical, unmet public health challenge. According to the CDC, in 2021, an estimated 20.9% of US adults (51.6 million people) endured chronic pain, and 6.9% (17.1 million people) endured high-impact chronic pain. Additionally, the impact of the social determinants of health on pain treatment are beginning to emerge. Treating pain addresses its control and relief, enhancing patient outcomes and quality of life. However, current treatment options have limitations, creating a significant need for innovative solutions. This raises the role of innovation in identifying new pain medicines. Thus, the clinical development of novel pain medicines is an unmet need to address public health worldwide.

Ketamine in neuropsychiatric disorders: an update

The discovery of ketamine as a rapid-acting antidepressant led to a new era in the development of neuropsychiatric therapeutics, one characterized by an antidepressant response that occurred within hours or days rather than weeks or months. Considerable clinical research supports the use of-or further research with-subanesthetic-dose ketamine and its (S)-enantiomer esketamine in multiple neuropsychiatric disorders including depression, bipolar disorder, anxiety spectrum disorders, substance use disorders, and eating disorders, as well as for the management of chronic pain. In addition, ketamine often effectively targets symptom domains associated with multiple disorders, such as anxiety, anhedonia, and suicidal ideation. This manuscript: 1) reviews the literature on the pharmacology and hypothesized mechanisms of subanesthetic-dose ketamine in clinical research; 2) describes similarities and differences in the mechanism of action and antidepressant efficacy between racemic ketamine, its (S) and (R) enantiomers, and its hydroxynorketamine (HNK) metabolite; 3) discusses the day-to-day use of ketamine in the clinical setting; 4) provides an overview of ketamine use in other psychiatric disorders and depression-related comorbidities (e.g., suicidal ideation); and 5) provides insights into the mechanisms of ketamine and therapeutic response gleaned from the study of other novel therapeutics and neuroimaging modalities.

Low-dose ketamine infusions for chronic pain management: Does this qualify as evidence-based practice?

Chronic pain is becoming increasingly prevalent and burdensome both worldwide and in the United Kingdom. Due to the complexity of chronic pain and the therapeutic challenge associated, management is often difficult and requires multidisciplinary care encompassing a combination of pharmacological and non-pharmacological strategies. Conventional analgesic treatments, such as opioids and anticonvulsants, are effective in less than half of chronic pain sufferers and are typically limited to short-term use to prevent complications associated with long-term use such as tolerance and dependence. Consequently, research and clinical interest in alternative management options for chronic pain have increased in recent years, with ketamine being one example under investigation. However, since ketamine has been licensed as an anaesthetic for decades, it has bypassed the traditional scrutinous drug development sequence that is typically seen for therapeutics marketed for pain. As such, data supporting the unlicensed administration of ketamine for chronic pain management is lacking and is being outpaced by the rates of off-label use in pain clinics. Recent limited evidence suggests that ketamine, when given as an intravenous infusion in subanaesthetic doses for refractory pain patients, may provide modest analgesic effects in nearly all aetiologies of chronic pain, with side effects common but typically mild. However, there are concerns over the safety of this practice due to the paucity of robust supportive evidence and the accompanying lack of clinical guidelines or standardised protocols. This review shall summarise the literature examining the use of subanaesthetic-dose ketamine infusions for chronic pain to comment on the current level of evidence, with limitations of existing research and future recommendations discussed.

Incidence of Dissociation With Low-Dose Pre-hospital Ketamine in Geriatric Patients With Trauma-Related Pain

Introduction

Sub-dissociative ketamine has been used increasingly for the treatment of acute pain in a wide variety of settings. While there are studies evaluating its use in the geriatric population, no studies have described its safety in the pre-hospital geriatric trauma patient. The objective of this study was to define the incidence of dissociation with low-dose pre-hospital ketamine in geriatric trauma patients.

Methods

Using our county emergency medical services database, we identified all trauma patients greater or equal to 65 years of age who received pre-hospital ketamine for pain after the implementation of a low-dose ketamine protocol. We retrospectively reviewed pre-hospital and emergency department records for demographics, traumatic injuries, Glasgow Coma Score, emergency department length of stay and disposition, and hospital length of stay. This group was compared to a similar population of trauma patients, transported prior to the ketamine protocol. The comparison group was chosen by matching the ketamine group to more than double the number of non-ketamine patients. Records were obtained from two separate trauma centers. Our primary outcome was documentation of “ketamine-related dissociation” by either the pre-hospital, emergency department or trauma provider. Secondary outcomes included emergency department length of stay and intensive care unit admission.

Results

Seventy-nine patients received ketamine with records available for analysis. One hundred ninety-three non-ketamine patients were compared to this group. There were nosignificant differences between the two groups in regards to age, weight, gender, or mechanism of injury. The injury severity score was higher in the ketamine group. Nine patients (11%) had documented dissociation after ketamine, with six of these patients back to baseline mentation by arrival to the emergency department. The emergency department length of stay was shorter in the ketamine group. The rate of intensive care unit admission was the same between both groups.

Conclusions

Pre-hospital sub-dissociative ketamine in geriatric trauma patients is associated with brief episodes of dissociation in a small minority of patients.

Ketamine Versus Etomidate and Peri-intubation Hypotension: A National Emergency Airway Registry Study

BACKGROUND

The hemodynamic impact of induction agents is a critically important consideration in emergency intubations. We assessed the relationship between peri-intubation hypotension and the use of ketamine versus etomidate as an induction agent for emergency department (ED) intubation.

METHODS

We analyzed ED intubation data for patients aged >14 years from the National Emergency Airway Registry performed in 25 EDs during 2016 through 2018. We excluded patients with preintubation hypotension (systolic blood pressure <100 mm Hg) or cardiac arrest prior to intubation. The primary outcome was peri-intubation hypotension. Secondary outcomes included interventions for hypotension (e.g., intravenous fluids or vasopressors). We report adjusted odds ratios (aOR) from multivariable logistic regression models controlling for patient demographics, difficult airway characteristics, and intubation modality.

RESULTS

There were 738 encounters with ketamine and 6,068 with etomidate. Patients receiving ketamine were more likely to have difficult airway characteristics (effect size difference = 8.8%, 95% confidence interval [CI] = 5.3% to 12.4%) and to undergo intubation with video laryngoscopy (8.1%, 95% CI = 4.4% to 12.0%). Peri-intubation hypotension incidence was 18.3% among patients receiving ketamine and 12.4% among patients receiving etomidate (effect size difference = 5.9%, 95% CI = 2.9% to 8.8%). Patients receiving ketamine were more likely to receive treatment for peri-intubation hypotension (effect size difference = 6.5%, 95% CI = 3.9% to 9.3%). In logistic regression analyses, patients receiving ketamine remained at higher risk for peri-intubation hypotension (aOR = 1.4, 95% CI = 1.2 to 1.7) and treatment for hypotension (aOR = 1.8, 95% CI = 1.4 to 2.0). There was no difference in the aOR of hypotension between patients receiving ketamine at doses ≤1.0 mg/kg versus >1.0 mg/kg or patients receiving etomidate at doses ≤0.3 mg/kg versus >0.3 mg/kg.

CONCLUSIONS

Pending additional data, our results suggest that clinicians should not necessarily prioritize ketamine over etomidate based on concern for hemodynamic compromise among ED patients undergoing intubation.