Low doses of epidural ketamine or neostigmine, but not midazolam, improve morphine analgesia in epidural terminal cancer pain therapy

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.

The Efficacy of Ketamine for Acute and Chronic Pain in Patients with Cancer: A Systematic Review of Randomized Controlled Trials

Managing cancer-related pain poses significant challenges, prompting research into alternative approaches such as ketamine. This systematic review aims to analyze and summarize the impact of ketamine as an adjuvant to opioid therapy for cancer-related pain. We conducted a literature review in MEDLINE, EMBASE, and Scopus from 1 January 1982 to 20 October 2023. Abstracts were screened against inclusion criteria, and eligible studies underwent a full-text review. Data was extracted from the included studies, and a framework analysis approach summarized the evidence regarding ketamine's use in patients with cancer. A total of 21 randomized clinical trials were included, and the quality of all the included studies was good or fair. Significant improvements in pain scores and reduced morphine consumption were consistently observed with intravenous ketamine administration for postoperative pain control, particularly when combined with other analgesics such as morphine. Ketamine was less effective when used as an analgesic for chronic pain management, with several studies on neuropathic pain or chemotherapy-induced neuropathy finding minimal significant effect on reduction of pain scores or morphine requirements. The efficacy of ketamine in pain management appears to depend on factors such as dosage, route of administration, and patient population.

Should Subanesthetic Ketamine be Considered When Managing Opioid Refractory Cancer Pain?

In the cancer pain setting, ketamine has been typically employed as a co-analgesic for opioid refractory and neuropathic pain. One controversial topic is whether subanesthetic ketamine be considered when managing opioid refractory cancer pain. In this "Controversies in Palliative Care" article, three clinicians independently answer this question. Specifically, each clinician provides a synopsis of the key studies that inform their thought processes, share practical advice on their clinical approach, and highlight the opportunities for future research. Three independent clinicians reported a divergence of opinion regarding the usefulness of subanesthetic ketamine for managing opioid refractory cancer pain. All investigators acknowledged the lack of high-quality trials. All agreed on the need for adequately powered trials, the development of standardized methodology, and the exploration of any patient sub-populations that may benefit from ketamine for cancer related pain.

Efficacy of epidural analgesia for intractable cancer pain: A systematic review

BACKGROUND

Epidural analgesia is a common technique for managing perioperative and obstetric pain. Patients with cancer who cannot tolerate opioids or not responding to conventional treatment may benefit from epidural analgesia. Therefore, this systematic review aimed to analyze the efficacy and safety of epidural analgesia in patients with intractable cancer pain.

METHODS

We searched PubMed, Embase, and the Cochrane Central Register of Controlled Trials to identify studies on patients with cancer who received epidural analgesia. We assessed the quality of all included studies using the risk-of-bias tool or Newcastle-Ottawa scale. The primary outcome was pain relief after epidural analgesia, and the secondary outcome was quality of life, analgesic consumption, and adverse events. The studies were grouped based on the medications used for epidural analgesia. A descriptive synthesis was performed following the Synthesis Without Meta-analysis reporting guideline.

RESULTS

Our systematic review included nine randomized controlled trials (n = 340) and 15 observational studies (n = 926). Two randomized controlled trials suggested that epidural opioids were not superior to systemic opioids in relieving pain. Epidural opioids combined with local anesthetics or adjuvants, including calcitonin, clonidine, ketamine, neostigmine, methadone, and dexamethasone, offered better analgesic effects. No significant difference in pain relief between an intermittent bolus and a continuous infusion of epidural morphine was observed. Epidural opioids had more analgesic effects on nociceptive pain than neuropathic pain. The methods used to evaluate the quality of life and the corresponding results were heterogeneous among studies. Six observational studies demonstrated that some patients could have decreased opioid consumption after epidural analgesia. Adverse events, including complications and drug-related side effects, were reported in 23 studies. Five serious complications, such as epidural abscess and hematoma, required surgical management. The heterogeneity and methodological limitations of the studies hindered meta-analysis and evidence-level determination.

CONCLUSION

Coadministration of epidural opioids, local anesthetics, and adjuvants may provide better pain relief for intractable cancer pain. However, we must assess the patients to ensure that the benefits outweigh the risks before epidural analgesia. Therefore, further high-quality studies are required.

Developing non-opioid therapeutics to alleviate pain among persons with opioid use disorder: a review of the human evidence

The opioid crisis remains a major public health concern, causing significant morbidity and mortality worldwide. Pain is frequently observed among individuals with opioid use disorder (OUD), and the current opioid agonist therapies (OAT) have limited efficacy in addressing the pain needs of this population. We reviewed the most promising non-opioid analgesic therapies for opioid-dependent individuals synthesising data from randomised controlled trials in the Medline database from December 2022 to March 2023. Ketamine, gabapentin, serotoninergic antidepressants, and GABAergic drugs were found to be the most extensively studied non-opioid analgesics with positive results. Additionally, we explored the potential of cannabinoids, glial activation inhibitors, psychedelics, cholecystokinin antagonists, alpha-2 adrenergic agonists, and cholinergic drugs. Methodological improvements are required to advance the development of novel analgesic strategies and establish their safety profile for opioid-dependent populations. We highlight the need for greater integration of experimental pain methods and abuse liability assessments, more granular assessments of prior opioid exposure, greater uniformity of pain types within study samples, and a particular focus on individuals with OUD receiving OAT. Finally, future research should investigate pharmacokinetic interactions between OAT and various non-opioid analgesics and perform reverse translation basic experiments, particularly with methadone and buprenorphine, which remain the standard OUD treatment.

The effects of a multiday (10-14 days) subanesthetic dose IV ketamine infusion in the treatment of refractory chronic pain

Aim: Ketamine is an anesthetic agent that at lower doses can be a potent analgesic. There has been an interest in the use of low dose ketamine in treatment of chronic pain syndromes. Patients & methods: We report the results of a retrospective observational study for patients diagnosed with a chronic noncancer pain syndrome receiving a 2-week continuous subanesthetic IV ketamine infusion. Results & conclusion: We conclude that a 10-14 days of subanesthetic ketamine infusion in chronic patients results in clinically significant lowering of patients' numerical pain score. Further studies looking at subanesthetic ketamine infusion in a prospective trial of multi-day IV ketamine infusion in chronic refractory chronic neuropathic pain are needed to further assess the efficacy of ketamine.

A review of the clinical applications of ketamine in pediatric oncology

Ketamine is a dissociative anesthetic agent with excellent analgesic properties and a favorable safety profile. The feasibility and efficacy of various routes of administration have been established, including intravenous (IV), intramuscular (IM), oral, intranasal, rectal, and transdermal routes. The advent of newer anesthetic agents has led to a decline in the use of ketamine as an anesthetic, but its utility in short-term sedation and analgesia has expanded. Its value for chronic pain management in children with cancer is being increasingly recognized but requires more evidence. The use of topical ketamine is largely in investigational stages. Medical use of ketamine is, to a great extent, free from significant long-term neurological side effects. The objective of this review is to provide a brief account of the pharmacology of ketamine and primarily focus on the clinical applications of ketamine in pediatric oncology.

The Efficacy of Ketamine in the Palliative Care Setting: A Comprehensive Review of the Literature

Background: Previous literature suggests that ketamine may be an effective drug in the palliative care population as this drug has been shown to treat multiple conditions that are common in these patients. Objective: This review examines the efficacy of ketamine for the treatment of depression and physical pain in palliative care patients. Methods: Eleven studies were included on the topic of ketamine as an antidepressant in the palliative care population. Additionally, 5 RCT studies were included on the topic of physical pain in this population. Results: All 11 studies, including one RCT, found antidepressant effects of ketamine in this patient population. Ketamine's effect on treating physical pain was mixed with the largest and most recent RCTs suggesting no significant analgesic effect. Discussion: This review suggests that starting qualified patients on intravenous (IV) ketamine and switching to oral or intranasal administration may be the most effective and convenient for treating depression, especially for patients who wish to receive treatment at home. Significant analgesia was found in patients who received epidural or intrathecal ketamine as well as in one study using intravenous administration. More research is necessary to determine which palliative care patients may benefit from ketamine treatment.

Interventional Techniques to Management of Cancer-Related Pain: Clinical and Critical Aspects

Interventional techniques to manage cancer-related pain may be efficient treatment modalities in patients unresponsive or unable to tolerate systemic opioids. However, indication and selection of the right technique demand knowledge, which is still incipient among clinicians. The present article summarizes the current evidence regarding the five most essential groups of interventional techniques to treat cancer-related pain: Neuraxial analgesia, minimally invasive procedures for vertebral pain, sympathetic blocks for abdominal cancer pain, peripheral nerve blocks, and percutaneous cordotomy. Furthermore, indication, mechanism, drug agents, contraindications, and complications of the main techniques of each group are discussed.

Ketamine for cancer pain: what is the evidence?

PURPOSE OF REVIEW

In this review, we assess the benefit of ketamine in the treatment of terminal cancer pain that is refractory to opioid treatment and/or complicated by neuropathy.

RECENT FINDINGS

While randomized controlled trials consistently show lack of clinical efficacy of ketamine in treating cancer pain, a large number of open-label studies and case series show benefit.

SUMMARY

Ketamine is an N-methyl-D-aspartate receptor antagonist that at low-dose has effective analgesic properties. In cancer pain, ketamine is usually prescribed as adjuvant to opioid therapy when pain becomes opioid resistant or when neuropathic pain symptoms dominate the clinical picture. A literature search revealed four randomized controlled trials that examined the benefit of oral, subcutaneous or intravenous ketamine in opioid refractory cancer pain. None showed clinically relevant benefit in relieving pain or reducing opioid consumption. This suggests absence of evidence of benefit for ketamine as adjuvant analgesic in cancer pain. These findings contrast the benefit from ketamine observed in a large number of open-label studies and (retrospective) case series. We relate the opposite outcomes to methodological issues. The complete picture is such that there is still insufficient evidence to state with certainty that ketamine is not effective in cancer pain.

Intranasal Ketamine and Its Potential Role in Cancer-Related Pain

Cancer-related pain continues to be a significant therapeutic challenge, made more difficult by contemporary opioid use and diversion concerns. Conventional treatment using a tiered approach of nonsteroidal antiinflammatory drugs (NSAIDs), opioids, and adjuvant agents is limited; and alternatives are needed for patients with rapidly progressing pain and those who develop hyperalgesia and tolerance to opioids. Ketamine, an N-methyl-d-aspartate (NMDA) selective antagonist, has historically been used for anesthesia in adult and pediatric populations but has also been investigated for depression, bipolar disorder, and general and postoperative pain management. As an analgesic, low-dose ketamine decreases morphine requirements and rates of nausea and vomiting, suggesting a potentially beneficial role in cancer-related pain. Ketamine is typically administered intravenously and has a rapid onset of action with a relatively short half-life (2-3 hours) but is inconvenient for use in an ambulatory setting. Oral bioavailability is low and erratic, limiting application of this route for chronic use. Intranasal administration has a number of potential advantages, including avoidance of first-pass hepatic metabolism, no need for venous access, ability to repeat doses quickly, and rapid absorption. Although early studies of intranasal ketamine are promising in a number of indications, information is more limited in its use as an adjunct in cancer-related pain. We review the background, rationale, pharmacokinetics, and clinical and safety data using intranasal ketamine as an adjunctive agent and its potential in cancer-related pain.

Ketamine as an adjuvant to opioids for cancer pain

BACKGROUND

This is an update of a review first published in 2003 and updated in 2012.Ketamine is a commonly used anaesthetic agent, and in subanaesthetic doses is also given as an adjuvant to opioids for the treatment of refractory cancer pain, when opioids alone or in combination with appropriate adjuvant analgesics prove to be ineffective. Ketamine is known to have psychomimetic (including hallucinogenic), urological, and hepatic adverse effects.

OBJECTIVES

To determine the effectiveness and adverse effects of ketamine as an adjuvant to opioids for refractory cancer pain in adults.

SEARCH METHODS

For this update, we searched MEDLINE (OVID) to December 2016. We searched CENTRAL (CRSO), Embase (OVID) and two clinical trial registries to January 2017.

SELECTION CRITERIA

The intervention considered by this review was the addition of ketamine, given by any route of administration, in any dose, to pre-existing opioid treatment given by any route and in any dose, compared with placebo or active control. We included studies with a group size of at least 10 participants who completed the trial.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the search results and performed 'Risk of bias' assessments. We aimed to extract data on patient-reported pain intensity, total opioid consumption over the study period; use of rescue medication; adverse events; measures of patient satisfaction/preference; function; and distress. We also assessed participant withdrawal (dropout) from trial. We assessed the quality of the evidence using GRADE (Grading of Recommendations Assessment, Development and Evaluation).

MAIN RESULTS

One new study (185 participants) was identified by the updated search and included in the review. We included a total of three studies in this update.Two small studies, both with cross-over design, with 20 and 10 participants respectively, were eligible for inclusion in the original review. One study with 20 participants examined the addition of intrathecal ketamine to intrathecal morphine, compared with intrathecal morphine alone. The second study with 10 participants examined the addition of intravenous ketamine bolus in two different doses to ongoing morphine therapy, compared with placebo. Both of these studies reported reduction in pain intensity and reduction in morphine requirements when ketamine was added to opioid for refractory cancer pain. The new study identified by the updated search had a parallel group design and 185 participants. This placebo-controlled study examined rapid titration of subcutaneous ketamine to high dose (500 mg) in participants who were using different opioids. There were no differences between groups for patient-reported pain intensity.Pooling of the data from the three included trials was not appropriate because of clinical heterogeneity.The study examining intrathecal drug administration reported no adverse events related to ketamine. In the study using intravenous bolus administration, ketamine caused hallucinations in four of 10 participants. In the rapid dose escalation/high-dose subcutaneous ketamine study, there was almost twice the incidence of adverse events in the ketamine group, compared to the placebo group, with the most common adverse events being needle site irritation and cognitive disturbance. Two serious adverse events (bradyarrhythmia and cardiac arrest) thought to be related to ketamine were also reported in this trial.For all three studies there was an unclear risk of bias overall. Using GRADE, we judged the quality of the evidence to be very low due to study limitations and imprecision due to the small number of participants in all comparisons.

AUTHORS' CONCLUSIONS

Current evidence is insufficient to assess the benefits and harms of ketamine as an adjuvant to opioids for the relief of refractory cancer pain. The evidence was of very low quality, meaning that it does not provide a reliable indication of the likely effect, and the likelihood that the effect will be substantially different is high. Rapid dose escalation of ketamine to high dose (500 mg) does not appear to have clinical benefit and may be associated with serious adverse events. More randomised controlled trials (RCTs) examining specific low-dose ketamine clinical regimens in current use are needed.

Interventional options for the management of refractory cancer pain--what is the evidence?

PURPOSE

Pain is the most common symptom in cancer patients. Standard pain treatment according to the WHO three-step analgesic ladder provides effective pain management in approximately 70-90% of cancer patients. Refractory pain is defined as not responding to "standard" treatments. Interventional analgesic techniques can be used in an attempt to control refractory pain in patients in whom conventional analgesic strategies fail to provide effective pain relief or are intolerable due to severe adverse effects. This systematic review aims to provide the latest evidence on interventional refractory pain management in cancer patients.

METHODS

Systematic literature search in Cochrane, EMBASE and PubMed including reviews and randomised controlled trials (RCTs) and non-randomised controlled trials in the absence of reviews.

RESULTS

Neuraxial analgesia may play a role in refractory cancer pain management. Paravertebral blocks decrease the incidence of persistent post-surgical pain after breast cancer. Coeliac plexus blocks improve pain scores in refractory pancreatic cancer pain for up to 4 weeks after the intervention with fewer burdensome side effects as compared to opioids. Cordotomy has mainly been studied in mesothelioma, and the case series suggest possible benefit for pain at the expense of a relatively high risk of side effects.

CONCLUSIONS

Overall, very few RCTs have been conducted on interventional pain techniques. In reality, it is very difficult to undertake large controlled trials for a number of reasons. Therefore, today's best evidence for practice may be from large case series of comparable patients with careful response and toxicity evaluation and follow-up.

Long-Term Intravenous Ketamine for Analgesia in a Child with Severe Chronic Intestinal Graft versus Host Disease

Ketamine is reported to be an effective adjuvant to opioids in the treatment of refractory cancer pain; however, the use of high doses of ketamine for extended periods in pediatric patients has not been described. We present a five-year-old male with grade IV intestinal GVHD whose abdominal pain required both hydromorphone and ketamine for a period of over four months. There was no evidence of hepatotoxicity, hemorrhagic cystitis, or other adverse effects. Possible withdrawal symptoms were mild and were readily mitigated by gradually weaning ketamine.

The evidence of neuraxial administration of analgesics for cancer-related pain: a systematic review

BACKGROUND

The present systematic review analysed the existing evidence of analgesic efficacy and side effects of opioids without and with adjuvant analgesics delivered by neuraxial route (epidural and subarachnoid) in adult patients with cancer.

METHODS

Search strategy was elaborated with words related to cancer, pain, neuraxial route, analgesic and side effects. The search was performed in PubMed, EMBASE, and Cochrane for the period until February 2014. Studies were analysed according to methods, results, quality of evidence, and strength of recommendation.

RESULTS

The number of abstracts retrieved was 2147, and 84 articles were selected for full reading. The final selection comprised nine articles regarding randomised controlled trials (RCTs) divided in four groups: neuraxial combinations of opioid and adjuvant analgesic compared with neuraxial administration of opioid alone (n = 4); single neuraxial drug in bolus compared with continuous administration (n = 2); single neuraxial drug compared with neuraxial placebo (n = 1); and neuraxial opioid combined with or without adjuvant analgesic compared with other comprehensive medical management than neuraxial analgesics (n = 2). The RCTs presented clinical and methodological diversity that precluded a meta-analysis. They also presented several limitations, which reduced study internal validity. However, they demonstrated better pain control for all interventions analysed. Side effects were described, but there were few significant differences in favour of the tested interventions.

CONCLUSION

Heterogeneous characteristics and several methodological limitations of the studies resulted in evidence of low quality and a weak recommendation for neuraxial administration of opioids with or without adjuvant analgesics in adult patients with cancer.

The evolution of spinal/epidural neostigmine in clinical application: Thoughts after two decades

Since the first clinical application of analgesia following spinal anticholinesterase by 1940's, several clinical double-blind studies have been conducted to date, where intrathecal doses of neostigmine in humans ranged from 750 to 1 μg, due to side-effects. Conversely, epidural neostigmine has been evaluated in proportionally higher doses and represents an alternative, but still deserves more investigation concerning both acute and chronic pain, as it seems devoid of important side-effects.

Ketamine for pain in adults and children with cancer: a systematic review and synthesis of the literature

OBJECTIVE

Chronic cancer pain is often refractory and difficult to treat. Ketamine is a medication with evidence of efficacy in the treatment of chronic pain.

DESIGN

This article presents a synthesis of the data on ketamine for refractory cancer pain in adults and children.

RESULTS

There are five randomized, double-blind, controlled trials of ketamine use in cancer pain that demonstrate improvement in pain for some patients. There are six prospective, uncontrolled trials in cancer pain that also demonstrate improvement in pain scores for some patients. There are no randomized, controlled trials in children with cancer pain, although there are a few studies reflecting improved pain control with ketamine for children with cancer pain. Adverse events for adults on ketamine are most commonly somnolence, feelings of insobriety, nausea/vomiting, hallucinations, depersonalization/derealization, and drowsiness. However, when ketamine is combined with benzodiazepines, feelings of insobriety, hallucinations, and depersonalization/derealization are not reported. Children on ketamine have had few reported adverse effects, which include sedation, anorexia, urinary retention, and myoclonic movements. Recommended ketamine infusion dosages are from 0.05 to 0.5 mg/kg/h (intravenous or subcutaneous). Recommended oral dosages of ketamine are 0.2-0.5 mg/kg/dose two to three times daily with a maximum of 50 mg/dose three times daily.

CONCLUSIONS

Despite limitations in the breadth and depth of data available, there is evidence that ketamine may be a viable option for treatment-refractory cancer pain.

Daily oral ketamine for the treatment of depression and anxiety in patients receiving hospice care: a 28-day open-label proof-of-concept trial

BACKGROUND

Depression and anxiety are prevalent and undertreated in patients receiving hospice care. Standard antidepressants do not work rapidly or often enough to benefit most of these patients. Ketamine has many properties that make it an interesting candidate for rapidly treating depression and anxiety in patients receiving hospice care. To test this hypothesis, a 28-day, open-label, proof-of-concept trial of daily oral ketamine administration was conducted in order to evaluate the tolerability, potential efficacy, and time to potential efficacy in treating depression and anxiety in patients receiving hospice care.

METHODS

In this open-label study, 14 subjects with symptoms of depression or depression mixed with anxiety warranting psychopharmacological intervention received daily oral doses of ketamine hydrochloride (0.5 mg/kg) over a 28-day period. The primary outcome measure was the Hospital Anxiety and Depression Scale (HADS), which was used to rate overall depression and anxiety symptoms at baseline, and on days 3, 7, 14, 21, and 28.

RESULTS

Over the 28-day trial there was significant improvement in both depressive symptoms (F5,35=8.03, p=0.002, η(2)=0.534) and symptoms of anxiety (F5,35=14.275, p<0.001, η(2)=0.67) for the eight subjects that completed the trial. One hundred percent of subjects completing the trial responded to ketamine for both anxiety and depression. A significant response in depressive symptoms occurred by day 14 for depression (mean Δ=3.5, d=1.14, 95% CI=1.09-5.9, p=0.01) and day 3 for anxiety (mean Δ=2.4, d=0.67, 95% CI=1.0-3.7, p=0.004). These improvements remained significant through day 28 for both depression (mean Δ=4.0, d=1.34, 95% CI=2.3-5.9, p=0.001) and anxiety (mean Δ=6.09, d=1.34, 95% CI=3.6-8.6, p<0.001). Side effects were rare, the most common being diarrhea, trouble sleeping, and trouble sitting still.

CONCLUSIONS

Patients who received daily oral ketamine experienced a robust antidepressant and anxiolytic response with few adverse events. The response rate for depression is similar to those found with IV ketamine; however, the time to response is more protracted. The findings of the potential efficacy of oral ketamine for depression and the response of anxiety symptoms are novel. Further investigation with randomized, controlled clinical trials is necessary to firmly establish the efficacy and safety of oral ketamine for the treatment of depression and anxiety in patients receiving hospice care or other subject populations.

Oral ketamine for children with chronic pain: a pilot phase 1 study

OBJECTIVE

To assess whether oral ketamine is safe at higher dosages for sedating children and whether it may be an option for the control of chronic pain in children.

STUDY DESIGN

A prospective study was performed on 12 children with chronic pain to identify the maximum tolerated dosage of oral ketamine. Participants were given 14 days of oral ketamine, 3 times daily, at dosages ranging from 0.25-1.5 mg/kg/dose. Participants were assessed for toxicity and for pain severity at baseline and on day 14 of treatment.

RESULTS

Two participants, both treated at 1.5 mg/kg/dose, experienced dose-limiting toxicities (sedation and anorexia). One participant, treated at 1 mg/kg/dose, opted to stop ketamine treatment due to new pain on treatment. Nine participants completed their course of ketamine treatment. Of these 12 children, 5 experienced improvement in their pain scores, 2 with complete resolution of pain, lasting >4 weeks off ketamine treatment.

CONCLUSION

Oral ketamine at dosages of 0.25-1 mg/kg/dose appears to be safe when given for 14 days to children with chronic pain.

Ketamine as an adjuvant to opioids for cancer pain

BACKGROUND

This is an update of the original review published in Issue 1, 2003. Ketamine is a commonly used anaesthetic agent, and in subanaesthetic doses is also given as an adjuvant to opioids for the treatment of cancer pain, particularly when opioids alone prove to be ineffective. Ketamine is known to have psychotomimetic (including hallucinogenic), urological and hepatic adverse effects.

OBJECTIVES

To determine the effectiveness and adverse effects of ketamine as an adjuvant to opioids in the treatment of cancer pain.

SEARCH METHODS

Studies were originally identified from MEDLINE (1966 to 2002), EMBASE (1980 to 2002), CancerLit (1966 to 2002), The Cochrane Library (Issue 1, 2001); by handsearching reference lists from review articles, trials, and chapters from standard textbooks on pain and palliative care. The manufacturer of ketamine (Pfizer Parke-Davis) provided search results from their in-house database, PARDLARS.An improved and updated search of the following was performed in May 2012: CENTRAL, MEDLINE & OVID MEDLINE R, EMBASE.

SELECTION CRITERIA

Randomized controlled trials (RCTs) of adult patients with cancer and pain being treated with an opioid, and receiving either ketamine (any dose and any route of administration) or placebo or an active control. Studies having a group size of at least 10 participants who completed the trial.

DATA COLLECTION AND ANALYSIS

Two independent review authors identified four RCTs for possible inclusion in the review, and 32 case studies/case series reports. Quality and validity assessment was performed by three independent review authors, and two RCTs were excluded because of inappropriate study design. Patient-reported pain intensity and pain relief was assessed using visual analogue scales (VAS), verbal rating scales or other validated scales, and adverse effects data were collated. For the update three RCTs were identified for possible inclusion in the review.

MAIN RESULTS

Three new studies were identified by the updated search. All three were excluded from the review. Two studies were eligible for inclusion in the original review and both concluded that ketamine improves the effectiveness of morphine in the treatment of cancer pain. However, pooling of the data was not appropriate because of the small total number of participants (30), and the presence of clinical heterogeneity. Some patients experienced hallucinations on both ketamine plus morphine and morphine alone and were treated successfully with diazepam. No other serious adverse effects were reported.

AUTHORS' CONCLUSIONS

Since the last version of this review three new studies were identified but excluded from the review. Current evidence is insufficient to assess the benefits and harms of ketamine as an adjuvant to opioids for the relief of cancer pain. More RCTs are needed.

The influence of adjuvants used in regional anesthesia on lidocaine-induced neurotoxicity in vitro

BACKGROUND

Neurotoxic properties of local anesthetics can rarely lead to irreversible neuronal damage as in cauda equina syndrome. Clinically, local anesthetics are often combined with adjuvants to improve or prolong the anesthetic effect, whereas the impact of such adjuvants on lidocaine-induced apoptosis is unclear. Therefore, we investigated the influence of different adjuvants on the neurotoxicity of lidocaine.

METHODS

Human neuroblastoma cells and primary rat astrocytes were incubated for 24 hrs with lidocaine at a toxic concentration alone and in combination with morphine, sufentanil, clonidine, epinephrine, neostigmine, ketamine, and midazolam. Subsequently, the rates of cell death and early apoptosis were measured by flow cytometry in neuroblastoma cells, whereas astrocyte viability was analyzed by mitochondrial activity assay. In addition, isobolograms were calculated to describe the additive effects of lidocaine with ketamine or midazolam, respectively.

RESULTS

Coadministration of lidocaine with sufentanil, clonidine, epinephrine, and neostigmine did not alter the rates of cell death compared with cells treated with lidocaine alone. Morphine improved the viability of astrocytes only at concentrations beyond those occurring clinically. In contrast, coincubation of lidocaine with ketamine or midazolam led to significantly increased rates of cell death. The combined toxicity of ketamine and lidocaine was additive, whereas the combined toxicity of midazolam and lidocaine was subadditive.

CONCLUSIONS

Sufentanil, clonidine, epinephrine, and neostigmine do not influence the neurotoxicity of lidocaine in vitro. Morphine may have some cytoprotective effect at concentrations greater than those seen intrathecally in humans. In contrast, ketamine and midazolam increase the neurotoxicity of lidocaine in vitro, presumably by additive induction of mitochondrial apoptosis.

Muscarinic pain pharmacology: realizing the promise of novel analgesics by overcoming old challenges

The antinociceptive and analgesic effects of muscarinic receptor ligands in human and nonhuman species have been evident for more than half a century. In this review, we describe the current understanding of the roles of different muscarinic subtypes in pain modulation and their mechanism of action along the pain signaling pathway, including peripheral nociception, spinal cord pain processing, and supraspinal analgesia. Extensive preclinical and clinical validation of these mechanisms points to the development of selective muscarinic agonists as one of the most exciting and promising avenues toward novel pain medications.

Spinal opioids in adult patients with cancer pain: a systematic review: a European Palliative Care Research Collaborative (EPCRC) opioid guidelines project

BACKGROUND

A systematic review, undertaken according to an initiative to revise European Association for Palliative Care guidelines on the use of opioids for cancer pain, which aimed to analyse analgesic efficacy and side effects of spinal opioids in adult cancer patients previously treated with systemic opioids.

METHODS

Search strategy elaborated with MeSH terms and words related to cancer, palliative care, pain, spinal route and opioids. PubMed, Embase and Cochrane assessed in Nov 2009. Studies were analysed and classified according to quality of evidence and strength of recommendation.

RESULTS

Out of 2939 abstracts, 44 articles were selected (nine randomized controlled trials (RCTs), two non-randomized cohort studies, 28 uncontrolled prospective studies, and five case series). Relief of pain and/or side effects were reported in 42 articles; however, there were few studies of high quality design (RCTs) and these studies had methodological limitations that reduced their quality of evidence to very low.

CONCLUSION

There are few RCTs and these are of very low quality. As a result, they provide weak recommendation for using spinal opioids in adult cancer patients. Further studies are clearly needed.

Combination drug therapy for chronic pain: a call for more clinical studies

Chronic pain is a debilitating clinical condition associated with a variety of disease entities including diabetic neuropathy, postherpetic neuralgia, low back pathology, fibromyalgia, and neurological disorders. For many general practitioners and specialists, managing chronic pain has become a daunting challenge. As a modality of multidisciplinary chronic pain management, medications are often prescribed in combinations, an approach referred to as combination drug therapy (CDT). However, many medications for pain therapy, including antidepressants and opioid analgesics, have significant side effects that can compound when used in combination and impact the effectiveness of CDT. To date, clinical practice of CDT for chronic pain has been based largely on clinical experiences. In this article, we will focus on (1) the scientific basis and rationales for CDT, (2) current clinical data on CDT, and (3) the need for more clinical studies to establish a framework for the use of CDT.

PERSPECTIVE

More preclinical, clinical, and translational studies are needed to improve the efficacy of combination drug therapy that is an integral part of a comprehensive approach to the management of chronic pain.

Neostigmine decreases bupivacaine use by patient-controlled epidural analgesia during labor: a randomized controlled study

BACKGROUND

Intrathecal neostigmine not only produces analgesia but also severe nausea. In contrast, epidural neostigmine enhances opioid and local anesthetic analgesia without causing nausea. Previous studies examined only single epidural neostigmine bolus administration and did not assess the efficacy of continuous epidural infusion or several aspects of maternal and fetal safety. We therefore tested the hypothesis that epidural neostigmine in combination with bupivacaine by continuous infusion during labor would reduce the amount of bupivacaine required.

METHODS

Twelve healthy women scheduled for elective cesarean delivery were assigned to receive epidural neostigmine, 40 microg (first six subjects) or 80 microg (second six subjects) as a single bolus, with fetal heart rate (FHR) and uterine contractions monitored for 20 min. In a subsequent experiment, 40 healthy laboring women were randomized to receive bupivacaine 1.25 mg/mL alone or with neostigmine 4 microg/mL by patient-controlled epidural analgesia. The primary outcome measure was hourly bupivacaine use.

RESULTS

Epidural neostigmine bolus did not alter baseline FHR, induce contractions, or produce nausea. Epidural neostigmine infusion reduced bupivacaine requirement by 19% in all patients and 25% in those with >4 h of treatment (P < 0.05 for both) but might have contributed to the incidence of mild sedation. Mode of delivery, incidence of maternal nausea, and FHR abnormality were similar between groups.

CONCLUSIONS

These data show that adding epidural neostigmine 4 microg/mL reduces the hourly bupivacaine requirement by 19%-25% with patient-controlled epidural analgesia during labor. Administered as a bolus and by continuous infusion at the studied doses, epidural neostigmine does not cause nausea and does not induce uterine contractions or FHR abnormalities, but mild sedation can occur.

Use of neostigmine in the management of acute postoperative pain and labour pain: a review

Neostigmine is a parasympathomimetic agent that has been recently investigated for use as an adjunct analgesic agent in the perioperative and peripartum period. A number of studies have investigated the intrathecal, epidural, caudal and intra-articular routes of administration of this agent, as well as the addition of neostigmine to local anaesthetics used for brachial plexus block and intravenous regional anaesthesia. While the intrathecal administration of neostigmine produced useful analgesic effects in the postoperative period in some studies, the high incidence of adverse events, mainly nausea and vomiting, limit the clinical usefulness of this route of administration. Several studies investigated the postoperative analgesic effects of epidural neostigmine using a number of different regimens. Overall, this route of administration appeared to improve postoperative analgesia in most studies without increasing the incidence of adverse events, and merits further research. Neuraxial administration of neostigmine appears to be safe in the obstetric population, with no reported adverse effects in the mother or fetus. While intrathecal administration is limited by a high incidence of nausea and vomiting in this patient population, the epidural route appears more promising and requires further investigation. The addition of neostigmine to caudal local anaesthetics was associated with improved postoperative analgesia in a number of studies. A dose of 2 microg/kg proved to be effective in several studies but was associated with an increased incidence of vomiting in some studies. Intra-articular administration of neostigmine 500microg produced a useful analgesic effect in the postoperative period in several studies and was not associated with an increase in the incidence of adverse effects. Studies investigating the efficacy of adding neostigmine to the local anaesthetics used for brachial plexus block and intravenous regional anaesthesia reported conflicting results. Further studies are required to determine the place of the administration of neostigmine by these routes.

Beneficial Effect of Low-Dose Ketamine Addition to Epidural Administration of Morphine–Bupivacaine Mixture for Cancer Pain in Two Cases

Two patients experiencing cancer pain with neuropathic components were treated with epidural administration of a mixture of ketamine (1 mg/mL) + morphine (1 mg/mL) + bupivacaine (1 mg/mL) injected daily by epidural port. No serious adverse effect was observed throughout the therapy. The patients were mostly pain-free and have gotten better quality of life during 110- and 48-day follow-up when the therapy was given by epidural route. Low doses of epidural ketamine added to morphine and bupivacaine increase the mean duration of satisfactory analgesia without severe adverse effects and restore quality of life when traditional therapy fails.

Cancer pain assessment in clinical trials. A review of the literature (1999-2002)

The aim of this review was to evaluate the methods of pain measurement in controlled clinical trials in oncology published between 1999 and 2002. An electronic literature search strategy was used according to established criteria applied to the Medline database and PubMed search engine. Articles were selected to include only studies that had chronic cancer pain as the primary or secondary objective of a controlled clinical trial. A specific evaluation scheme was used to examine how pain measurement methods were chosen and implemented in the study procedures. The search strategy identified 613 articles, and 68 were selected for evaluation. Most articles (69%) chose unidimensional pain measurement tools, such as visual analogue scales, numerical rating scales and verbal rating scales, whereas others used questionnaires. The implementation of the pain assessment method was problematic in many studies, especially as far as time frame of pain assessment (70%), administration modalities (46%), and use of non-validated measurement methods (10%). Design of study and data analysis were often unclear about the definition of pain outcome measure (40%), patient compliance with pain assessment (98%), and impact of missing data (56%). Statistical techniques were seldom appropriate to the type of data collected and often inadequate to describe the pain variable under study. It is clear from this review that most authors were aware of the need of valid pain measurement tools to be used in clinical trials. However, too often these tools were not appropriately used in the trial, or at least their use was not described with sufficient accuracy in the trial methods.

Role of Analgesic Adjuncts in Postoperative Pain Management

Postoperative pain remains a major problem. A multi-modal analgesic approach is recommended to optimize pain management and reduce opiate-related adverse effects. Several analgesic adjuncts have been investigated, and many have proved to have a useful analgesic effect. This article reviews the literature regarding use of analgesic adjuncts in the perioperative period.

A Qualitative Systematic Review of the Role of N-Methyl-d-Aspartate Receptor Antagonists in Preventive Analgesia

We evaluated in a qualitative systematic review the effect of N-methyl-D-aspartate (NMDA) receptor antagonists on reducing postoperative pain and analgesic consumption beyond the clinical duration of action of the target drug (preventive analgesia). Randomized trials examining the use of an NMDA antagonist in the perioperative period were sought by using a MEDLINE (1966-2003) and EMBASE (1985-2003) search. Reference sections of relevant articles were reviewed, and additional articles were obtained if they evaluated postoperative analgesia after the administration of NMDA antagonists. The primary outcome was a reduction in pain, analgesic consumption, or both in a time period beyond five half-lives of the drug under examination. Secondary outcomes included time to first analgesic request and adverse effects. Forty articles met the inclusion criteria (24 ketamine, 12 dextromethorphan, and 4 magnesium). The evidence in favor of preventive analgesia was strongest in the case of dextromethorphan and ketamine, with 67% and 58%, respectively, of studies demonstrating a reduction in pain, analgesic consumption, or both beyond the clinical duration of action of the drug concerned. None of the four studies examining magnesium demonstrated preventive analgesia.

IMPLICATIONS

We evaluated, in a qualitative systematic review, the effect of N-methyl D-aspartate antagonists on reducing postoperative pain and analgesic consumption beyond the clinical duration of action of the target drug (preventive analgesia). Dextromethorphan and ketamine were found to have significant immediate and preventive analgesic benefit in 67% and 58% of studies, respectively.

Epidural administration of tiletamine/zolazepam in horses

OBJECTIVES

To evaluate the analgesic, physiologic, and behavioral effects of the epidural administration of tiletamine/zolazepam in horses.

STUDY DESIGN

Prospective, double-blind, randomized experimental study.

ANIMALS

Five adult, healthy horses aged 10-16 years and weighing (mean +/- SD) 400 +/- 98 kg.

METHODS

The horses were sedated with 1.0 mg kg(-1) intravenous (IV) xylazine, and an epidural catheter was placed into the first intercoccygeal intervertebral space. After a 48-hour resting period, epidural tiletamine/zolazepam, 0.5 mg kg(-1) (treatment I) or 1.0 mg kg(-1) (treatment II), diluted up to 5 mL in sterile water, was administered with a 1-week interval between the treatments. Heart rate, respiratory rate, arterial blood pressure, and sedation were evaluated. In order to evaluate the respiratory effects, blood from the carotid artery was withdrawn at time 0 (baseline), and then after 60 and 240 minutes. Analgesia was evaluated by applying a noxious stimulus with blunt-tipped forceps on the perineal region, and graded as complete, moderate, or absent. Data were collected before tiletamine/zolazepam administration and at 15-minute intervals for 120 minutes, and 4 hours after tiletamine/zolazepam administration. Data were analyzed with anova and Bonferroni's test with p < 0.05.

RESULTS

The results showed no significant difference between treatments in cardiovascular and respiratory measurements. Sedation was observed with both doses, and it was significantly different from baseline at 60, 75, and 90 minutes in treatment II. Moderate analgesia and locomotor ataxia were observed with both the treatments.

CONCLUSIONS AND CLINICAL RELEVANCE

The results suggest that caudal epidural 0.5 and 1.0 mg kg(-1) tiletamine/zolazepam increases the threshold to pressure stimulation in the perineal region in horses. The use of epidural tiletamine/zolazepam could be indicated for short-term moderate epidural analgesia. There are no studies examining spinal toxicity of Telazol, and further studies are necessary before recommending clinical use of this technique.

Ketamine as adjuvant to opioids for cancer pain. A qualitative systematic review

Ketamine is increasingly being used as an adjuvant to opioids in the treatment of refractory cancer pain. This systematic review examines the available evidence. Randomized, controlled trials, with or without crossover, were included. Studies were identified from MEDLINE, EMBASE, CANCERLIT, the Cochrane Library, handsearched reference lists from review articles and chapters from standard textbooks on pain and palliative care and reference lists from papers retrieved. Four randomized, controlled studies were identified. Two were excluded due to poor quality. Both included studies concluded that ketamine improves morphine treatment in cancer pain. Quantitative meta-analysis was not possible. The available evidence is not sufficient to conclude that ketamine improves the effectiveness of opioid treatment in cancer pain. High quality, randomized, controlled trials with larger numbers of patients and standardized, clinically relevant routes of administration of ketamine are needed.

Dose response study of caudal neostigmine for postoperative analgesia in paediatric patients undergoing genitourinary surgery

BACKGROUND

Neostigmine given through the neuraxial route has been found to have analgesic properties. In this clinical trial, we evaluated for the first time the efficacy of a varying dose of caudal neostigmine for postoperative analgesia in children undergoing genitourinary surgery.

METHOD

In this double blind prospective study, we studied 120 children ASA physical status I in age group of 2-8 years scheduled for surgical repair of hypospadias under general anaesthesia. Children were randomly allocated to one of the six groups (n = 20 each) and received either no caudal block (group C) or neostigmine (groups I-V) in doses of 10, 20, 30, 40 and 50 microgram.kg-1 respectively at the end of the surgery. Postoperatively pain was assessed using an objective pain score for 24 h. Blood pressure, heart rate, SpO2, total amount of analgesic consumed and adverse effects, if any, were also recorded.

RESULT

The duration of postoperative analgesia did not differ significantly between group C and I (P > 0.05). There was significant prolongation in the duration of analgesia in rest of the groups (group II-3.52 +/- 1.37 h; group III-6.50 +/- 1.93 h; group IV-10.45 +/- 3.41 h; group V-13.70 +/- 5.52 h) (P < 0.05). A dose dependent increase in the incidence of nausea and vomiting was also observed with highest incidence in group IV and V (group C-15%; group I-20%; group II and III-30%; group IV-45% and group V-60%) (P < 0.05). No significant alteration in vital signs and other adverse effects were noticed.

CONCLUSION

Caudal neostigmine in the dose range of 20-50 microgram.kg-1 provides dose dependent analgesia. However, dose exceeding 30 microgram.kg-1 is associated with a higher incidence of nausea and vomiting.

Ketamine as an adjuvant to opioids for cancer pain

BACKGROUND

Ketamine is a commonly used anaesthetic agent, and in subanaesthetic doses is also given as an adjuvant to opioids for the treatment of cancer pain, particularly when opioids alone prove to be ineffective. Ketamine is known to have hallucinogenic side effects. To date no systematic review of the benefits and harms of adjuvant ketamine for cancer pain has been undertaken.

OBJECTIVES

To determine the effectiveness and adverse effects of ketamine as an adjuvant to opioids in the treatment of cancer pain.

SEARCH STRATEGY

Studies were identified from MEDLINE (1966-2001), EMBASE (1980-2001), CancerLit (1966-2001), the Cochrane Library (Issue 1, 2001); by handsearching reference lists from review articles, trials, and chapters from standard textbooks on pain and palliative care. The manufacturer of ketamine (Pfizer Parke-Davis) provided search results from their in-house database, PARDLARS.

SELECTION CRITERIA

RCTs of adult patients with cancer and pain being treated with an opioid, and receiving either ketamine (any dose and any route of administration) or placebo or an active control.

DATA COLLECTION AND ANALYSIS

Two independent reviewers identified four RCTs for possible inclusion in the review, and 32 case studies/case series reports. Quality and validity assessment was performed by three independent reviewers, and two RCTs were excluded because of inappropriate study design. Patient reported pain intensity and pain relief was assessed using visual analog scales, verbal rating scales or other validated scales, and adverse effects data were collated.

MAIN RESULTS

Two trials were eligible for inclusion in the review and both concluded that ketamine improves the effectiveness of morphine in the treatment of cancer pain. However, pooling of the data was not appropriate because of the small total number of patients (30), and the presence of clinical heterogeneity. Some patients experienced hallucinations on both ketamine plus morphine and morphine alone and were treated successfully with diazepam. No other serious adverse effects were reported.

REVIEWER'S CONCLUSIONS

Current evidence is insufficient to assess the benefits and harms of ketamine as an adjuvant to opioids for the relief of cancer pain. More randomized controlled trials are needed.

Epidural morphine and neostigmine for postoperative analgesia after orthopedic surgery

In this study, we examined the side effects and analgesia of the combination of epidural neostigmine and morphine in patients undergoing orthopedic surgery. Sixty patients undergoing knee surgery were divided into four groups. The intrathecal anesthetic was 15 mg of bupivacaine. The epidural test drug was diluted in saline to a final volume of 10 mL. The control group received saline as the epidural test drug. The morphine group received 0.6 mg of epidural morphine. The neostigmine group (NG) received 60 micro g of epidural neostigmine. The morphine/neostigmine group received 0.6 mg of epidural morphine combined with 60 micro g of epidural neostigmine. The groups were demographically the same and did not differ in intraoperative characteristics. The visual analog scale score at first rescue analgesic and the incidence of adverse effects were similar among groups (P > 0.05). One patient from the NG complained of intraoperative nausea, closely related to spinal hypotension. Postoperatively, two patients from the NG had vomited once. The time (min) to first rescue analgesic was longer in the morphine/neostigmine group ( approximately 11 h) compared with the other groups (P < 0.05). The analgesic consumption (number of analgesic administrations in 24 h) was larger in the control group compared with the other groups (P < 0.05).

IMPLICATIONS

The combination of epidural morphine and epidural neostigmine resulted in postoperative analgesia (11 h) devoid of side effects, being an alternative analgesic technique in the population studied.

Caudal neostigmine, bupivacaine, and their combination for postoperative pain management after hypospadias surgery in children

In a randomized, double-blinded study, we examined the analgesic efficacy of caudal neostigmine, bupivacaine, or a mixture of both drugs in 60 children. After the induction of general anesthesia, children were allocated randomly into three groups (n = 20) to receive a caudal injection of either 0.25% bupivacaine 1 mL/kg, with or without neostigmine 2 micro g/kg, or neostigmine 2 micro g/kg in normal saline 1 mL/kg. Intraoperatively, children receiving caudal bupivacaine or a bupivacaine/neostigmine mixture maintained hemodynamic stability, required less inhaled anesthetics, and had a shorter recovery time compared with the caudal neostigmine alone. Postoperatively, the caudal bupivacaine/neostigmine mixture resulted in superior analgesia compared with the other two groups. Recovery to first rescue analgesic times were (mean +/- SD) 22.8 +/- 2.9 h, 8.1 +/- 5.9 h, and 5.2 +/- 2.1 h in the bupivacaine/neostigmine, bupivacaine, and neostigmine groups, respectively (P < 0.001). In addition, the bupivacaine and neostigmine groups received more doses of paracetamol than the bupivacaine/neostigmine group to maintain adequate analgesia in the first 24 postoperative h. Postoperative vomiting occurred in 25%, 10%, and 30% in the caudal bupivacaine/neostigmine, bupivacaine, and neostigmine groups, respectively (P < 0.01). We conclude that caudal neostigmine 2 micro g/kg provides postoperative analgesia comparable to caudal bupivacaine in children undergoing hypospadias repair surgery.

IMPLICATIONS

Caudal neostigmine 2 micro g/kg provides postoperative analgesia comparable to caudal bupivacaine in children undergoing hypospadias repair surgery. Co-administration of the two drugs is associated with extended postoperative analgesia and reduced need for supplementary analgesics.

Interaction of a combination of morphine and ketamine on the nociceptive flexion reflex in human volunteers

Experimental studies in animals have suggested that a combination of morphine and N-methyl-D-aspartate (NMDA) receptor antagonists may have additive or synergistic analgesic effects. To further study the nature of the interaction between these two classes of analgesic agents, we analyzed the effects of morphine, ketamine and their combination on electrophysiological recordings of the nociceptive flexion RIII reflex in 12 healthy volunteers. Morphine (0.1 mg/kg), ketamine (0.1 mg/kg followed by 4 microg/kg/min) or their combination were administered intravenously according to a double-blind, placebo controlled and cross-over design. The RIII reflex was recorded from the biceps femoris and elicited by electrical stimulation of the sural nerve. The effects of the drugs were tested on: (1) the stimulus-response curves of the reflex up to the tolerance threshold (frequency of stimulation: 0.1Hz); (2) the progressive increase of the reflex and painful sensations (i.e. wind-up phenomenon) induced by a series of 15 electrical stimuli at a frequency of 1Hz (intensity: 20% above threshold). The stimulus-response curve of the nociceptive RIII reflex was significantly reduced after injection of a combination of ketamine and morphine, but was not modified when placebo or each of the active drugs was administered alone. The wind-up of the RIII reflex and painful sensation was not significantly altered after the injection of placebo, ketamine, morphine or their combination. In conclusion, the present electrophysiological results in humans demonstrate a synergistic interaction between morphine and ketamine, which tends to confirm the interest of using this type of combination in the clinical context. The differential effects observed on the recruitment curve and wind-up indicate, however, that the mechanisms of the interaction between opiates and NMDA receptor antagonists are not univocal but depend on the modality of activation of the nociceptive afferents.

Evaluation of the safety and efficacy of epidural ketamine combined with morphine for postoperative analgesia after major upper abdominal surgery

STUDY OBJECTIVE

To evaluate the efficacy of the combination of epidural ketamine and morphine compared with epidural morphine alone for postoperative pain relief following major upper abdominal surgery.

STUDY DESIGN

Prospective, randomized, double-blinded study.

SETTING

Tertiary care referral and teaching hospital.

PATIENTS

46 ASA physical status I and II patients who underwent major upper abdominal procedures.

INTERVENTIONS

Patients were randomly allocated to one of the two treatment groups: patients in Group 1 received epidural morphine 50 microg/kg whereas patients in Group 2 received epidural ketamine 1 mg/kg combined with 50 microg/kg of morphine postoperatively.

MEASUREMENTS

A blinded observer using a visual analog scale (VAS) for pain assessment followed up patients for 48 hours postoperatively. Top-up dose of epidural morphine was provided when VAS was higher than 4. Analgesic requirements and side effects were compared between the two groups.

RESULTS

Only 40 patients completed the study. There were no differences between the two groups with respect to age, gender, weight, duration, or type of surgical procedure or intraoperative opioid requirements. Onset of analgesia was faster (p < 0.001) in Group 2 (11 min) than in Group 1 patients (25 min). The time for first requirement of analgesia was significantly (p < 0.01) longer (19.8 +/- 9.8 hours) in Group 2 patients than Group 1 (12.8 +/- 6.2 hours). Total number of supplemental doses of epidural morphine required in the first 48 hours postoperatively was also significantly less (p < 0.005) in Group 2 compared to Group 1. Patients in Group 2 had higher sedation scores than Group I patients for the first 2 hours postoperatively. None of the patients in either group developed hallucinations or respiratory depression. Other side effects such as pruritus, nausea, and vomiting were also similar in both groups.

CONCLUSIONS

The addition of epidural ketamine 1 mg/kg to morphine 50 microg/kg improved analgesia after major upper abdominal surgery without increasing side effects.

Ketamine: a new look at an old drug

Ketamine is a major drug for induction of patients with hypovolemia and for general anaesthesia under primitive conditions, but also has excellent properties for more generalized use in children, adults and other fragile patients. Potential beneficial effects on cardiac ischaemia and cerebral injury is presently explored, as well as the effects of ketamine as an potent analgesic drug. Combination with propofol or midazolam for sedation provides analgesia, sleep and spontaneous ventilation. The S-isomer of ketamine has a lower incidence of psychomimetic side effects in equianalgesic doses compared with the racemate or the R-isomer alone.