Ketamine as a Prehospital Analgesic: A Systematic Review

Narrative Review: Low-Dose Ketamine for Pain Management

Pain is the leading cause of medical consultations and occurs in 50-70% of emergency department visits. To date, several drugs have been used to manage pain. The clinical use of ketamine began in the 1960s and it immediately emerged as a manageable and safe drug for sedation and anesthesia. The analgesic properties of this drug were first reported shortly after its use; however, its psychomimetic effects have limited its use in emergency departments. Owing to the misuse and abuse of opioids in some countries worldwide, ketamine has become a versatile tool for sedation and analgesia. In this narrative review, ketamine's role as an analgesic is discussed, with both known and new applications in various contexts (acute, chronic, and neuropathic pain), along with its strengths and weaknesses, especially in terms of psychomimetic, cardiovascular, and hepatic effects. Moreover, new scientific evidence has been reviewed on the use of additional drugs with ketamine, such as magnesium infusion for improving analgesia and clonidine for treating psychomimetic symptoms. Finally, this narrative review was refined by the experience of the Pain Group of the Italian Society of Emergency Medicine (SIMEU) in treating acute and chronic pain with acute manifestations in Italian Emergency Departments.

A Comparison of Prehospital Pediatric Analgesic Use of Ketamine and Opioids

OBJECTIVE/INTRODUCTION

Ketamine is an opioid-alternative used for analgesia in the prehospital setting. There are knowledge gaps regarding its use during emergency medical services (EMS) encounters for pediatric patients. Our objective was to compare pain reduction, adverse events, and prehospital deaths between ketamine and opioids when used for analgesia administered by any route among pediatric patients.

METHODS

This was a retrospective review of 9-1-1 EMS records of injured pediatric patients (≤17 years of age) who received ketamine or opioids for analgesia using the ESO Data Collaborative (calendar years 2019-2020). We excluded interfacility transfers, patients receiving both medications, those with EMS clinician impressions indicating behavioral disorders, and those who received medication to facilitate advanced airway placement. EMS narrative review was performed to confirm ketamine use was for analgesia and to identify any unplanned airway placements. We assessed pain score reduction (0-10 ordinal scale) and clinician-documented patient response (improved, unchanged, worsened, unknown). Adverse events were defined as change in vital signs (GCS, SBP, RR, SpO2), bag valve mask ventilation alone, or death. Descriptive statistics were calculated to compare outcomes between groups.

RESULTS

Overall, 9,223 patients were included, 190 (2.1%) received ketamine and 9,033 (97.9%) received opioids. Mean age in years was 12.8 [SD 4.0] for ketamine and 12.7 [SD 4.0] for opioids. Patients in both groups experienced pain reduction, and more patients receiving ketamine had EMS clinician reported improvement (93.2% vs. 87.9%, p = 0.03). Ketamine was associated with a greater average reduction in pain score than opioids (mean difference: -4.4 [SD 3.5], and -3.1 [SD 2.8], p < 0.001). Adverse events were rare with few patients receiving ventilatory support following the use of ketamine or opioids, (0, [SD 0.0%] vs. 6 [SD 0.1%], p = 1). There were no unplanned airway placements or prehospital deaths identified.

CONCLUSION

We identified similar high rates of pain reduction and rare adverse events among pediatric patients who received ketamine or opioids. A greater pain reduction was noted among patients administered ketamine. Intubation as a result of medication administration did not occur and need for ventilatory assistance was rare.

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 for acute pain after trauma: the KAPT randomized controlled trial

Background

Evidence for effective pain management and opioid minimization of intravenous ketamine in elective surgery has been extrapolated to acutely injured patients, despite limited supporting evidence in this population. This trial seeks to determine the effectiveness of the addition of sub-dissociative ketamine to a pill-based, opioid-minimizing multi-modal pain regimen (MMPR) for post traumatic pain.

Methods

This is a single-center, parallel-group, randomized, controlled comparative effectiveness trial comparing a MMPR to a MMPR plus a sub-dissociative ketamine infusion. All trauma patients 16 years and older admitted following a trauma which require intermediate (IMU) or intensive care unit (ICU) level of care are eligible. Prisoners, patients who are pregnant, patients not expected to survive, and those with contraindications to ketamine are excluded from this study. The primary outcome is opioid use, measured by morphine milligram equivalents (MME) per patient per day (MME/patient/day). The secondary outcomes include total MME, pain scores, morbidity, lengths of stay, opioid prescriptions at discharge, and patient centered outcomes at discharge and 6 months.

Discussion

This trial will determine the effectiveness of sub-dissociative ketamine infusion as part of a MMPR in reducing in-hospital opioid exposure in adult trauma patients. Furthermore, it will inform decisions regarding acute pain strategies on patient centered outcomes.

Trial registration

The Ketamine for Acute Pain Management After Trauma (KAPT) with registration # NCT04129086 was registered on October 16, 2019.

Prehospital Ketamine Use in Pediatrics

Introduction: Information regarding prehospital ketamine use in the pediatric population is limited as existing literature focuses primarily on critical care and air transport. Our objective was to describe patient characteristics among pediatric EMS patients who received ketamine. Secondarily, we assessed effectiveness, deviation from recommended dosing, and adverse outcomes of pediatric EMS patients who received ketamine.Methods: We conducted a retrospective data review of records from the ESO Data Collaborative for all 9-1-1 transports of pediatric patients (≤ 18 years of age) who received ketamine from 2019-2020. We categorized EMS primary impressions as a proxy for medication indication. We defined effectiveness as paramedic-identified clinical improvement, and pain relief as decrease in pain score ≥2 points between initial and final recording. Descriptive statistics were used to summarize clinical characteristics. Non-parametric Wilcoxon signed-rank test was used to assess change in pain score.Results: Out of 422,968 ground-ambulance pediatric patients, 1,291 received ketamine. They were predominately male (842, 65.2%), teenagers (median age 16, IQR: 13-17), Caucasian (810, 62.7%), and from urban areas (1,041, 80.6%). The most common EMS impressions were related to injuries (810, 62.7%) and behavior disorders (281, 21.8%). Only 980/1,291 (75.9%) had weights and identifiable routes recorded. Most patients (960, 74.4%) received single doses of ketamine, with EMS clinicians reporting improvement in 855 (89.1%) of 960 patients. Among non-behavioral emergency patients, 727/1,010 (72.0%) had pain scores recorded. Pain scores decreased significantly from a median of 8 (IQR: 4-10) to 2 (IQR: 0-6) (p < 0.001) with 59% (429) of 727 patients reporting pain score reductions of 2 or more points. Desaturation (<90% SpO₂) events were noted to be minimal (1.8%). A small number (28, 2.2%) received positive pressure ventilation without advanced airway placement. No prehospital deaths were documented.Conclusion: In this large review of pediatric prehospital ketamine use, ketamine was primarily used for analgesia, but was frequently used for other indications. Most patients were observed to improve after ketamine use, with most injured patients reporting decreases in pain scores. We observed few significant adverse events related to ketamine use in this population.

Opioid Sparing Effect of Ketamine in Military Pre-Hospital Pain Management - A Retrospective Study

BACKGROUND

Opioids are the most commonly used analgesics in acute trauma, but are limited by slow onset and significant adverse effects. Ketamine is an effective and widely used analgesic. This study was aimed to evaluate the effectiveness and opioid-sparing effects of ketamine when utilized in pre-hospital military trauma setting.

METHODS

A retrospective analysis of a pre-hospital military trauma registry between 2014 - 2020. Inclusion criteria were age ≥ 16 years, ≥2 documented pain assessments, at least one indicating severe pain, and administration of opioids and/or low-dose ketamine. Joint hypothesis testing was used to compare casualties who received opioids only to those who received ketamine on outcomes of pain score reduction and opioid consumption.

RESULTS

Overall, 382 casualties were included. 91 (24%) received ketamine (21 as a single analgesic), with a mean dose of 29 mg (SD 11). Mean reduction in pain scores (on an 11-point scale) was not significantly different; 4.3-point (2.8) reduction in the ketamine group and 3.7-points (2.4) in the opioid-only group (p = 0.095). Casualties in the ketamine group received a median of 10 mg (IQR 3.5, 25) of morphine equivalents (ME) compared with a median of 20 ME (10, 20) in the opioid-only group. In a multivariable multinomial logistic regression, casualties in the ketamine group were significantly more likely to receive a low (1-10 ME) rather than a medium (11-20 ME) dose of opioids compared to the opioid-only group (OR 0.032, CI 0.14 - 0.75).

CONCLUSIONS

The use of ketamine in the pre-hospital military setting as part of a pain management protocol was associated with a low rather than medium dose of opioids in a multivariable analysis, while the mean reduction in pain scores was not significantly different between groups. Using ketamine as a first-line agent may further reduce opioid consumption with a similar analgesic effect.

LEVELS OF EVIDENCE

Level IV, therapeutic/care management.

Should Ketamine Not Be Banned? A Scoping Review

OBJECTIVES

Although the importance of ketamine in clinical practice and in resource-poor settings and disaster zones, several attempts were made to reschedule it because of the issues around its misuse. Resisting future moves to reschedule ketamine is important for its continuous availability where needed. This scoping review addresses the question of whether ketamine should or should not be banned and the state of preparedness of low resource settings if ketamine petitions become successful in the future.

METHODS

A search was performed using PubMed and Google Scholar to identify articles published in the English language from March 2015 to August 2020. The articles were searched with a wide range of priori search terms related to the research questions. The selection of articles was based on relevance and eligibility.

RESULTS

Seventy-five articles were selected and grouped into 4 ethical themes. The search revealed that several articles addressed the importance of ketamine, pharmacology, misuse, supply, and consequences of a ketamine ban; however, none addressed how resource-poor countries should prepare for a future without the overreliance of ketamine.

CONCLUSION

Four ketamine petitions in about 10 years are an indication that another may resurface soon; therefore, it is important to continue to study the clinical importance of ketamine while discouraging its overreliance for clinical practice.

Analgesia in adult trauma patients in physician-staffed Austrian helicopter rescue: a 12-year registry analysis

Background

Sufficient analgesia is an obligation, but oligoanalgesia (NRS> 3) is frequently observed prehospitally. Potent analgesics may cause severe adverse events. Thus, analgesia in the helicopter emergency medical service (HEMS) setting is challenging. Adequacy, efficacy and administration safety of potent analgesics pertaining to injured patients in HEMS were analysed.

Methods

Observational study evaluating data from 14 year-round physician-staffed helicopter bases in Austria in a 12-year timeframe.

Results

Overall, 47,985 (34.3%) patients received analgesics, 26,059 of whom were adult patients, injured and not mechanically ventilated on site. Main drugs administered were opioids (n=20,051; 76.9%), esketamine (n=9082; 34.9%), metamizole (n=798; 3.1%) and NSAIDs (n=483; 1.9%). Monotherapy with opioids or esketamine was the most common regimen (n=21,743; 83.4%), while opioids together with esketamine (n= 3591; 13.8%) or metamizole (n=369; 1.4%) were the most common combinations. Females received opioids less frequently than did males (n=6038; 74.5% vs. n=14,013; 78.1%; p< 0.001). Pain relief was often sufficient (> 95%), but females more often had moderate to severe pain on arrival in hospital (n=34; 5.0% vs. n=59; 3.2%; p=0.043). Administration of potent analgesics was safe, as indicated by MEES, SpO₂ and respiratory rates. On 10% of all missions, clinical patient assessment was deemed sufficient by HEMS physicians and monitoring was spared.

Conclusions

Opioids and esketamine alone or in combination were the analgesics of choice in physician-staffed HEMS in Austria. Analgesia was often sufficient, but females more than males suffered from oligoanalgesia on hospital arrival. Administration safety was high, justifying liberal use of potent analgesics in physician-staffed HEMS.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13049-021-00839-9.