Emerging applications of low-dose ketamine for pain management in the ED

A Case Report of Subanesthetic Ketamine Bolus and Infusion for Opioid Refractory Cancer Pain

Opioids and traditional adjuvant medications are frequently prescribed for the management of moderate to severe cancer pain with good effect. However, there are many cases, in which patients experience severe opioid refractory cancer pain. Ketamine is being used more frequently in the hospice and palliative setting to manage opioid refractory pain, although high-quality evidence regarding its effectiveness is lacking. It seems certain patients respond favorably to ketamine, while others experience no effect. Studies have not yet identified factors associated with a favorable response to ketamine. We present a case describing the successful treatment of high-dose opioid refractory cancer pain with a subanesthetic ketamine infusion and propose the novel use of a preinfusion test bolus of ketamine to identify patients who are likely to respond favorably to an infusion.

Synergistic Effect of Ketamine and Buprenorphine Observed in the Treatment of Buprenorphine Precipitated Opioid Withdrawal in a Patient With Fentanyl Use

BACKGROUND

Optimal treatment of buprenorphine precipitated opioid withdrawal (BPOW) is unclear. Full agonist treatment of BPOW is limited by buprenorphine's high-affinity blockade at mu-opioid receptors (μORs). Buprenorphine's partial agonism (low intrinsic efficacy) at μORs can limit the effectiveness of even massive doses once BPOW has begun. Adjunct medications, such as clonidine, are rarely effective in severe BPOW. Ketamine is an N-methyl-D-aspartate receptor antagonist with a potentially ideal pharmacologic profile for treatment of BPOW. Ketamine reduces opioid withdrawal symptoms independently of direct μOR binding, synergistically potentiates the effectiveness of buprenorphine μOR signaling, reverses (resensitizes) fentanyl induced μOR receptor desensitization, and inhibits descending pathways of hyperalgesia and central sensitization. Ketamine's rapid antidepressant effects potentially address depressive symptoms and subjective distress that often accompanies BPOW. Ketamine is inexpensive, safe, and available in emergency departments. To date, neither ketamine as treatment for BPOW nor to support uncomplicated buprenorphine induction has been described.

CASE DESCRIPTION

We report a case of an illicit fentanyl-using OUD patient who experienced severe BPOW during an outpatient low-dose cross taper buprenorphine induction (ie, "microdose"). The BPOW was successfully treated in the emergency department with a combination of ketamine (0.6 mg/kg intravenous over 1 hour) combined with high-dose buprenorphine (16 mg sublingual single dose); 3 days later he was administered a month-long dose of extended-release subcutaneous buprenorphine which was repeated monthly (300 mg). At 90 days the patient remained in treatment and reported continuous abstinence from fentanyl use.

CONCLUSIONS

This single case observation raises important questions about the potential therapeutic role of ketamine as a treatment for BPOW. BPOW is an important clinical problem for which there is currently only limited guidance and no universally accepted approach. Prospective study comparing the effectiveness of differing pharmacologic approaches to treat BPOW is urgently needed.

The Expanding Role of Ketamine in the Emergency Department

Patients frequently come to the emergency department for pain. For decades, ketamine has been used in the emergency department for procedural sedation but is now receiving attention as a potential alternative to opioids because of its unique analgesic effects. Additionally, ketamine's dissociative properties have made it a popular choice for sedating profoundly agitated patients. In this narrative review, these new roles for ketamine in the emergency department are discussed.

The Evolving Landscape of Acute Pain Management in the Era of the Opioid Crisis

PURPOSE OF REVIEW

The purpose of the study is to evaluate and analyze the role of both opioid and non-opioid analgesics in the emergency department (ED).

RECENT FINDINGS

Studies have shown that the implementation of opioid-prescribing policies in the ED has the potential to reduce the opioid addiction burden. Clinical studies point to inconsistencies in providers' approach to pain treatment. In this review, we discuss specific aspects of opioid utilization and explore alternative non-opioid approaches to pain management. Pain is the most common reason patients present to the ED. As such, emergency medicine (EM) providers must be well versed in treating pain. EM providers must be comfortable using a wide variety of analgesic medications. Opioid analgesics, while effective for some indications, are associated with significant adverse effects and abuse potential. EM providers should utilize opioid analgesics in a safe and rational manner in an effort to combat the opioid epidemic and to avoid therapeutic misadventures. EM providers should be aware of all of their therapeutic options, e.g., opioid and non-opioid, in order to provide effective analgesia for their patients, while avoiding adverse effects and minimizing the potential for misuse.

Low dose ketamine use in the emergency department, a new direction in pain management

There is a need for alternative non-opioid analgesics for the treatment of acute, chronic, and refractory pain in the emergency department (ED). Ketamine is a fast acting N-methyl-d-aspartate (NMDA) receptor antagonist that provides safe and effective analgesia. The use of low dose ketamine (LDK) (<1mg/kg) provides sub-dissociative levels of analgesia and has been studied as an alternative and/or adjunct to opioid analgesics. We reviewed 11 studies using LDK either alone or in combination with opioid analgesics in the ED. Ketamine was shown to be efficacious at treating a variety of painful conditions. It has a favorable adverse effect profile when given at sub-dissociative doses. Studies have also compared LDK to opioids in the ED. Although ketamine's analgesic effects were not shown to be superior, they were comparable to opioids. LDK has the benefit of causing less respiratory depression. It likely has less wide spread potential for abuse. Nursing protocols for the administration of LDK have been studied. We believe that LDK has the potential to be a safe and effective alternative and/or adjunct to opioid analgesics in the ED. Additional studies are needed to expand upon and determine the optimal use of LDK in the ED.

The use of subdissociative-dose ketamine for acute pain in the emergency department

OBJECTIVES

Ketamine is a well-known anesthetic with its use trailing back to the 1960s. It has antagonistic effects at the N-methyl-d-aspartate receptor. There is emerging literature to suggest the use of subdissociative-dose ketamine (SDDK) for pain reduction. This evidence-based review evaluates the evidence regarding the use of SDDK for acute pain control in the emergency department (ED).

METHODS

The MEDLINE and EMBASE databases were searched. Randomized controlled trials (RCTs) that described or evaluated the use of SDDK for acute pain in the ED were included. Literature was excluded if it was not published in English. Duplicate articles, unpublished reports, abstracts, and review articles were also excluded. Quality assessment and evaluation of literature were evaluated based on the GRADE criteria. The primary outcome of interest in this review was the difference in pain score from baseline to cutoff time as specified in the studies. Secondary outcome measures were the incidence of adverse events and reduction in the amount of adjuvant opioids consumed by patients who received SDDK.

RESULTS

Four RCTs met the inclusion criteria, which enrolled a total of 428 patients. Three adult trials and one pediatric trial were identified. The level of evidence for the individual trials ranged from low to moderate. A significant reduction in pain scores was only found in two of the four trials. One trial found a significant reduction in mean pain scores when ketamine was compared to morphine (p < 0.05). Another trial reported a significant decrease in mean distress scores, favoring SDDK over fentanyl (1.0 vs. 2.7, p < 0.05). One trial found a significant reduction in the amount of morphine consumed, favoring ketamine over placebo (0.14 mg/kg, 95% confidence interval [CI] = 0.13 to 0.16 mg/kg vs. 0.2 mg/kg, 95% CI = 0.18 to 0.22 mg/kg; p < 0.001). An emergence phenomenon was reported in one trial.

CONCLUSIONS

Four RCTs with methodologic limitations failed to provide convincing evidence to either support or refute the use of SDDK for acute pain control in the ED.

Low-Dose Ketamine Infusion for Emergency Department Patients with Severe Pain

OBJECTIVE

Use of low-dose ketamine infusions in the emergency department (ED) has not previously been described, despite routine use in perioperative and other settings. Our hypothesis was that a low-dose ketamine bolus followed by continuous infusion would 1) provide clinically significant and sustained pain relief; 2) be well tolerated; and 3) be feasible in the ED.

METHODS

We prospectively administered 15 mg intravenous ketamine followed immediately by continuous ketamine infusion at 20 mg/h for 1 hour. Optional morphine (4 mg) was offered at 20, 40, and 60 minutes. Pain intensity, vitals signs, level of sedation, and adverse reactions were assessed for 120 minutes.

RESULTS

A total of 38 patients were included with a median initial numerical rating scale (NRS) pain score of 9. At 10 minutes, the median reduction in pain score was 4, with 7 patients reporting a score of 0. At 60 and 120 minutes, 25 and 26 patients, respectively, reported clinically significant pain reduction (decrease NRS score > 3). Heart rate, blood pressure, respiratory rate, and oxygen saturation remained stable. Mild or moderate side effects including dizziness, fatigue, and headache were common. Patient satisfaction was high; 85% reported they would have this medication again for similar pain.

CONCLUSION

A low-dose ketamine infusion protocol provided significant pain relief with mostly mild side effects and no severe adverse events.

Low-dose ketamine improves pain relief in patients receiving intravenous opioids for acute pain in the emergency department: results of a randomized, double-blind, clinical trial

OBJECTIVES

Low-dose ketamine has been used perioperatively for pain control and may be a useful adjunct to intravenous (IV) opioids in the control of acute pain in the emergency department (ED). The aim of this study was to determine the effectiveness of low-dose ketamine as an adjunct to morphine versus standard care with morphine alone for the treatment of acute moderate to severe pain among ED patients.

METHODS

A double-blind, randomized, placebo-controlled trial with three study groups was conducted at a large, urban academic ED over a 10-month period. Eligible patients were 18 to 65 years old with acute moderate to severe pain (score of at least 5 out of 10 on the numerical pain rating scale [NRS] and pain duration < 7 days) who were deemed by their treating physician to require IV opioids. The three study groups were: 1) morphine and normal saline placebo (standard care group), 2) morphine and 0.15 mg/kg ketamine (group 1), or 3) morphine and 0.3 mg/kg ketamine (group 2). Participants were assessed at 30, 60, and 120 minutes after study medication administration and received rescue analgesia as needed to target a 50% reduction in pain. The primary outcome measure of pain relief, or pain intensity reduction, was derived using the NRS and calculated as the summed pain-intensity (SPID) difference over 2 hours. The amount and timing of rescue opioid analgesia was evaluated as a secondary outcome. The occurrence of adverse events was also measured.

RESULTS

Sixty patients were enrolled (n = 20 in each group). There were no differences between study groups with respect to age, sex, race/ethnicity, preenrollment analgesia, or baseline NRS. Over the 2-hour poststudy medication administration period, the SPIDs were higher (greater pain relief) for the ketamine study groups than the control group (standard care 4.0, interquartile range [IQR] = 1.8 to 6.5; group 1 7.0, IQR = 4.3 to 10.8; and group 2 7.8, IQR = 4.8 to 12.8; p < 0.02). The SPIDs for the ketamine groups were similar (p < 0.46). When compared to standard care, group 2 sustained the reduction in pain intensity up to 2 hours, whereas group 1 was similar to standard care by 2 hours. Similar numbers of patients received rescue analgesia: standard care group, seven of 20, 35%; group 1, four of 20, 20%; and group 2, four of 20, 20% (p = 0.48). Among those receiving rescue analgesia, those in the standard care group received analgesia sooner than either low-dose ketamine group, on average. More participants in the low-dose ketamine groups reported dysphoria and dizziness.

CONCLUSIONS

Low-dose ketamine is a viable analgesic adjunct to morphine for the treatment of moderate to severe acute pain. Dosing of 0.3 mg/kg is possibly more effective than 0.15 mg/kg, but may be associated with minor adverse events. Future studies should evaluate additional outcomes, optimum dosing, and use in specific populations.

Continuous Infusion of Ketamine for Out-of-hospital Isolated Orthopedic Injuries Secondary to Trauma: A Randomized Controlled Trial

Abstract Objective. Although ketamine has recently been demonstrated to provide a morphine-sparing effect, no previous study reports the effect of continuous infusion of ketamine for analgesia in out-of-hospital environments. The aim of this study was to compare the effect of a continuous infusion of ketamine (IK group) vs. a continuous infusion of saline (IS group) on morphine requirements in out-of-hospital trauma patients suffering from severe acute pain. Methods. In this prospective, multicenter, randomized, single-blind clinical study, patients suffering from isolated orthopedic injuries secondary to trauma with severe acute pain received a low-dose intravenous (IV) bolus of ketamine (0.2 mg·kg^-1) combined with an IV bolus of morphine (0.1 mg·kg^-1) and were randomized either in the IK group (IV continuous infusion of ketamine 0.2 mg·kg^-1·h^-1), or in the IS group (IV continuous infusion of saline at the same volume). The primary endpoint was morphine requirements in terms of total dose of morphine (excluding the baseline bolus) injected at the end of prehospital emergency care at hospital admission (final time, Tf). The secondary endpoint was evaluation of pain with visual analogic scale (VAS). Results. Sixty-six patients were enrolled. Total morphine dose was not significantly reduced with continuous infusion of ketamine (0.048 [0.000; 0.150] vs. 0.107 [0.052; 0.150] in IK and IS groups), with similar mean duration of care (median 35.0 min). Analgesia was as efficient without any significant difference in VAS at Tf between groups (3.1 ± 2.3 (IK group) vs. 3.7 ± 2.7 (IS group), p = 0.5). Conclusions. Continuous ketamine infusion did not reduce morphine requirements in severe acute pain trauma patients in the out-of-hospital emergency settings.

Sub-dissociative-dose intranasal ketamine for moderate to severe pain in adult emergency department patients

BACKGROUND

There are currently no studies assessing effectiveness of sub-dissociative intranasal (IN) ketamine as the initial analgesic for adult patients in the ED.

OBJECTIVE

The study aims to examine the effectiveness of sub-dissociative IN ketamine as a primary analgesic agent for adult patients in the ED.

METHOD

This is a prospective, observational study of adult ED patients presenting with severe pain (≥6 on 11-point scale at triage). IN ketamine dose was 0.7 mg/kg, with secondary dose of 0.5 mg/kg at 15 min if pain did not improve. After 6 months, initial dose was increased to 1.0 mg/kg with the same optional secondary dose.

PRIMARY OUTCOMES

The primary outcomes are change in VAS rating at 30 min; percentage of patients reporting clinically significant reduction in VAS (≥20 mm) at 30 min; dose resulting in clinically significant pain reduction.

RESULTS

Of the 72 patients available for analysis, median age was 34.5 years and 64% were men. Median initial VAS rating was 76 mm (interquartile range [IQR]: 65-82). Median total dose of IN ketamine for all patients was 0.98 mg/kg (IQR: 0.75-1.15, range: 0.59-1.57). Median reduction in VAS rating at 30 min was 24 mm (IQR: 2-45). Forty (56%, 95% CI: 44.0-66.7) reported VAS reduction ≥20 mm, these patients having had a total median ketamine dose of 0.94 mg/kg (IQR: 0.72-1.04).

CONCLUSION

IN ketamine, at a dose of about 1 mg/kg, was an effective analgesic agent in 56% of study patients. The place of IN ketamine in analgesic guidelines for adults requires further investigation.