Role of N-methyl-D-aspartate receptor antagonists in postoperative pain management

Analgesic and Hemodynamic Effects of Dexmedetomidine-Ketamine vs Fentanyl-Ketamine in Healthy Volunteers: A Randomized Trial

Background

Dexmedetomidine is an α2-agonist sedative with opioid-sparing properties, is limited by dose-dependent hypotension and bradycardia. Ketamine, an NMDA receptor antagonist, has sympathomimetic effects and may attenuate these cardiovascular effects while contributing analgesia. Whether low-dose ketamine can stabilize dexmedetomidine-induced hemodynamic changes and provide comparable analgesia to an opioid-based regimen is uncertain.

Methods

In this open-label trial, we enrolled 41 healthy volunteers aged 18 to 45 years. All participants received a ketamine infusion (0.3 mg/kg bolus, then 0.15 mg/kg/hour for 3 hours). At 90 minutes, participants were randomized to receive either dexmedetomidine (0.7 µg/kg/hour for 90 minutes, KET/DEX group) or fentanyl (three 25 µg boluses, KET/FENT group). The primary outcomes were change in blood pressure and pain tolerance (measured by pressure algometry). Secondary outcomes included heart rate, subjective mood and sedation, and adverse events. Data were analyzed using mixed-effects models and Fisher's exact tests.

Results

Of 41 randomized participants, 39 completed the protocol (KET/DEX, 19; KET/FENT, 20). KET/DEX resulted in greater reductions in systolic blood pressure (mean decrease 35-40 mm Hg; ~25-30%) compared to KET/FENT (mean change minimal; between-group P<0.001). Heart rate declined modestly with KET/DEX but did not differ significantly between groups. Both regimens increased pain tolerance to a similar degree (mean threshold rise ~30-50 kPa; between-group P=0.80). Participants in the KET/DEX group reported greater sedation and transient negative mood effects (eg, disinterest), while KET/FENT was associated with mild nausea in a minority. Clinically significant hypotension occurred in 4 participants (21%) in the KET/DEX group and in none of the KET/FENT group (P=0.047). All events were transient and responsive to fluid boluses. No respiratory depression occurred in either group.

Conclusion

Ketamine plus dexmedetomidine produced analgesia equivalent to ketamine plus fentanyl but with more pronounced hypotension and deeper sedation. The hemodynamic effects of dexmedetomidine were not fully offset by low-dose ketamine. These findings suggest that while ketamine-dexmedetomidine may offer an opioid-sparing alternative, careful dose selection and monitoring are required to ensure tolerability. (Funded by Monash University and Monash Health; ACTRN12617000787381).

Clinical Trial Number and Registry Url

https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=372916.

An Opioid-Sparing Strategy for Laparoscopic Sleeve Gastrectomy: A Retrospective Matched Case-Controlled Study in China

Background: Opioid-sparing anesthesia may enhance postoperative recovery by reducing opioid-related side effects. The present study was to evaluate the effect of an opioid-sparing strategy in bariatric surgery.

Methods: This study was conducted as a retrospective matched case-controlled (1:1) study. A total of 44 patients receiving either an opioid-based approach (OBA group) or an opioid-sparing strategy (OSA group) who under laparoscopic sleeve gastrectomy were included between May 2017 and October 2020. The primary outcome was the postoperative hospital length of stay (PLOS). Secondary outcomes were the hospital costs, operative opioid consumption, time to recovery, postoperative pain score at rest and rescue antiemetic administered in the PACU.

Results: The clinical demographic and operative data in both groups were comparable. There were no significant differences between the two groups in the PLOS (OSA vs. OBA: 6.18 ± 0.23 days vs. 6.73 ± 0.39 days, p = 0.24). Compared to the OBA group, opioid consumption in the OSA group was significantly decreased (48.79 ± 4.85 OMEs vs. 10.57 ± 0.77 OMEs, p < 0.001). There were no significant differences in the hospital costs, time to recovery, and rescue antiemetic administered, the incidence of intravenous opioids and vasopressor use in the PACU.

Conclusion: The opioid-sparing anesthesia for laparoscopic sleeve gastrectomy was feasible but did not decrease the PLOS.

Opioid-Sparing Perioperative Analgesia Within Enhanced Recovery Programs

Opioid-based analgesia in the perioperative period can provide excellent pain control, but this approach exposes the patient to avoidable side effects and possible harm. Optimal analgesia, an approach that targets the fastest functional recovery with adequate pain control while minimizing side effects, can be achieved with opioid minimization. Many different options for nonopioid multimodal analgesia exist and have been shown to be efficacious, with certain modalities being more beneficial for specific surgeries. This review will present the evidence and practical tips for these management strategies.

Impact of Intraoperative Ketamine on Postoperative Analgesic Requirement Following Bariatric Surgery: a Meta-analysis of Randomized Controlled Trials

This meta-analysis aimed at exploring the impact of intravenous ketamine on pain relief and analgesic consumption in patients undergoing bariatric surgery (BS). Literature searches identified nine eligible trials with 458 participants. Forest plot revealed a significantly lower pain score [mean difference (MD) =  - 1.06, p = 0.005; 390 patients) and morphine consumption (MD =  - 3.85 mg, p = 0.01; 212 patients) immediately after BS in patients with intravenous ketamine than in those without. In contrast, pooled analysis showed comparable pain score (p = 0.28), morphine consumption (p = 0.45) within 24 h, and risk of postoperative nausea/vomiting (p = 0.67) between the two groups. In conclusion, the meta-analysis demonstrated improvements in pain outcomes immediately after surgery through perioperative intravenous ketamine administration despite the absence of analgesic benefit in the late postoperative period and a positive impact on postoperative nausea/vomiting.

Effects of ketamine versus dexmedetomidine maintenance infusion in posterior spinal fusion surgery on acute postoperative pain

Background:

One of the most challenging issues after posterior spinal fusion (PSF) surgery is providing appropriate pain control measures to enhance recovery of the patients. We aimed to compare effects of ketamine versus dexmedetomidine infusion during maintenance of anesthesia on acute postoperative pain in PSF surgery.

Methods:

In a double-blinded randomized clinical trial, 87 patients candidates for PSF surgery were randomly assigned into three groups. Anesthesia protocol for all groups was the same except: the first group received 0.2 mcg/kg/h dexmedetomidine infusion, the second received 0.1 mg/kg/h ketamine infusion, and control group received normal saline infusion as a placebo. Pain intensity by VAS scale and level of sedation by Ramsey scale were assessed, and amount of opioid prescribed after surgery was measured and compared for patients during the recovery and at 2, 4, 6, 12, and 24 h after surgery in three groups, and hypotension and bradycardia during operation were reported.

Results:

There was a significant difference among the groups regarding pain intensity and amount of opioids during recovery and at 2, 4, 6, 12, and 24 h after surgery. Pain intensity and amount of opioids for ketamine and dexmedetomidine groups were significantly lower than those in the controls during recovery and at the hours after surgery. There was no significant difference regarding bradycardia and hypotension and level of sedation during recovery and at the hours after surgery.

Conclusion:

Both ketamine and dexmedetomidine infusions during maintenance of anesthesia are effective in reducing acute postoperative pain effectively after PSF surgery.

Does central sensitization affect hyperalgesia after staged bilateral total knee arthroplasty? A randomized controlled trial

Objective

Osteoarthritis (OA) patients who undergo staged bilateral total knee arthroplasty (TKA) feel postoperative hyperalgesia in the second operated knee compared with the first knee. Ketamine is an important drug for central temporal summation and inhibition of secondary mechanical hyperalgesia. This study investigated whether central sensitization has a significant effect on hyperalgesia after consecutive operations.

Methods

Seventy-one of 80 OA patients were randomly allocated to the ketamine or saline group. A bolus of ketamine (group K) or saline (group C) (0.5 mg/kg) was injected before induction and at an infusion rate of 3 µg/kg/minute during surgery. A visual analog scale (VAS) was used to assess resting and moving pain and opioid consumption on postoperative days 1, 2, and 3.

Results

The difference in the VAS score between stages 1 and 2 (D_V2-V1) was higher in the ketamine compared with the saline group. D_V2-V1 for movement between the two groups was not inferior for all periods. Ketamine did not show a large analgesic effect on second-operated knee hyperalgesia in staged bilateral TKAs.

Conclusions

We could not confirm that hyperalgesia was only related to central sensitization with low-dose ketamine. Other factors might be also associated with the hyperexcitability of nociceptive stimuli.

Clinical Research Information Service (CRIS) trial registry no: KCT0001481

Chronic Opioid Use After Surgery: Implications for Perioperative Management in the Face of the Opioid Epidemic

Physicians, policymakers, and researchers are increasingly focused on finding ways to decrease opioid use and overdose in the United States both of which have sharply increased over the past decade. While many efforts are focused on the management of chronic pain, the use of opioids in surgical patients presents a particularly challenging problem requiring clinicians to balance 2 competing interests: managing acute pain in the immediate postoperative period and minimizing the risks of persistent opioid use after the surgery. Finding ways to minimize this risk is particularly salient in light of a growing literature suggesting that postsurgical patients are at increased risk for chronic opioid use. The perioperative care team, including surgeons and anesthesiologists, is poised to develop clinical- and systems-based interventions aimed at providing pain relief in the immediate postoperative period while also reducing the risks of opioid use longer term. In this paper, we discuss the consequences of chronic opioid use after surgery and present an analysis of the extent to which surgery has been associated with chronic opioid use. We follow with a discussion of the risk factors that are associated with chronic opioid use after surgery and proceed with an analysis of the extent to which opioid-sparing perioperative interventions (eg, nerve blockade) have been shown to reduce the risk of chronic opioid use after surgery. We then conclude with a discussion of future research directions.

A Comparative Study on the Efficacy of Oral Memantine and Placebo for Acute Postoperative Pain in Patients Undergoing Dacryocystorhinostomy (DCR)

BACKGROUND

Memantine is an N-methyl-D-Aspartate (NMDA) antagonist. By transferring acute postoperative pain, the NMDA channels may lead to active excess and neuropathic pain. Objectives: This study attempted to investigate the effect of preoperative use of single oral dose of memantine in controlling Dacryocystorhinostomy (DCR) postoperative pain.

METHODS

A double-blind clinical trial was conducted on 60 patients undergoing DCR. On arrival at the operating room, the memantine group received 20 mg of oral memantine and the control group received placebo. The severities of pain by visual analogue scale (VAS) and sedation by Ramsy Scale were measured immediately 1, 2, and 6 hours after the operation. The drug's side effects were recorded.

RESULTS

The pain scores of patients in the recovery in 1, 2, and 6 hours after operation were significantly lower in the memantine group than the placebo group (P < 0.001). The sedation score, 1 hour after the operation, was significantly greater in the memantine group than the placebo (P < 0.001). The sedation scores did not have any statistically significant difference in recovery and 2 hours after surgery between the two groups. Moreover, the sedation scores in 6 hours after the surgery were identical in the two groups.

CONCLUSIONS

The oral single-dose 20 mg of memantine administered before DCR can reduce postoperative pain compared with placebo.

Ketamine-A Narrative Review of Its Uses in Medicine

One of the most fascinating drugs in the anesthesiologist's armament is ketamine, an N-methyl-D-aspartate receptor antagonist with a myriad of uses. The drug is a dissociative anesthetic and has been used more often as an analgesic in numerous hospital units, outpatient pain clinics, and in the prehospital realm. It has been used to treat postoperative pain, chronic pain, complex regional pain syndrome, phantom limb pain, and other neuropathic conditions requiring analgesia. Research has also demonstrated its efficacy as an adjunct in psychotherapy, as a treatment for both depression and posttraumatic stress disorder, as a procedural sedative, and as a treatment for respiratory and neurologic conditions. Ketamine is not without its adverse effects, some of which can be mitigated with certain efforts. Such effects make it necessary for the clinician to use the drug only in situations where it will provide the greatest benefit with the fewest adverse effects. To the best of our knowledge, none of the reviews regarding ketamine have taken a comprehensive look at the drug's uses in all territories of medicine. This review will serve to touch on its chemical data, pharmacokinetics and pharmacodynamics, medical uses, and adverse effects while focusing specifically on the drugs usage in anesthesia and analgesia.

Preemptive Epidural Analgesia for Postoperative Pain Relief Revisited: Comparison of Combination of Buprenorphine and Neostigmine with Combination of Buprenorphine and Ketamine in Lower Abdominal Surgeries, A Double-blind Randomized Trial

Context:

Postoperative pain relief provides subjective comfort to patient in addition to blunting of autonomic and somatic reflex responses to pain, subsequently enhancing restoration of function by allowing the patient to breathe, cough, and move easily.

Aims:

The aim is to evaluate and compare the effects of neostigmine + buprenorphine and ketamine + buprenorphine for preemptive epidural analgesia for postoperative pain relief in patients undergoing abdominal surgeries under general anesthesia (GA).

Settings and Design:

A double-blind randomized trial.

Subjects and Methods:

A total of 60 American Society of Anesthesiologists physical status Classes I and II patients undergoing abdominal surgeries under GA were taken up for the study. They were randomly allocated into two groups, Group A and Group B of thirty patients each. Preemptive epidural analgesia for postoperative pain relief was provided by a combination of neostigmine 1 μg/kg + buprenorphine 2 μg/kg in Group A patients and ketamine 1 mg/kg + buprenorphine 2 μg/kg in Group B patients after induction of GA but before surgical incision. Postoperatively, vital parameters, pain score, requirement of top up doses, and side effects in the two groups were observed and recorded at 2, 4, 6, 10, 18, and 22 h.

Statistical Analysis Used:

Mean values within each of the Group A and Group B were compared using one-way analysis of variance (one-way ANOVA). Mean values between Group A and Group B were compared using double analysis of variance (two-way ANOVA).

Results:

Group A patients had a significant analgesia (visual analog scale [VAS] pain scores reduced significantly from 54.6 ± 6.3 at 2 h to 8.1 ± 8.9 at 22 h postoperatively). Group B patients had significant analgesia too (VAS pain scores reduced significantly from 36 ± 12.5 at 2 h to 5.3 ± 10.9 at 22 h postoperatively). There was however no significant difference between the two groups with respect to the degree of postoperative analgesia on comparison of VAS scores, effect on vital parameters, and incidence of side effects.

Conclusions:

Either of the two combinations, neostigmine 1 μg/kg + buprenorphine μg/kg or ketamine 1 mg/kg + buprenorphine 2 μg/kg can be safely used for preemptive epidural analgesia for postoperative pain relief in patients undergoing abdominal surgeries under GA.

Perioperative Dextromethorphan as an Adjunct for Postoperative Pain: A Meta-analysis of Randomized Controlled Trials

BACKGROUND

N-methyl-D-aspartate receptor antagonists have been shown to reduce perioperative pain and opioid use. The authors performed a meta-analysis to determine whether the use of perioperative dextromethorphan lowers opioid consumption or pain scores.

METHODS

PubMed, Web of Science, Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, Pubget, and EMBASE were searched. Studies were included if they were randomized, double-blinded, placebo-controlled trials written in English, and performed on patients 12 yr or older. For comparison of opioid use, included studies tracked total consumption of IV or intramuscular opioids over 24 to 48 h. Pain score comparisons were performed at 1, 4 to 6, and 24 h postoperatively. Difference in means (MD) was used for effect size.

RESULTS

Forty studies were identified and 21 were eligible for one or more comparisons. In 848 patients from 14 trials, opioid consumption favored dextromethorphan (MD, -10.51 mg IV morphine equivalents; 95% CI, -16.48 to -4.53 mg; P = 0.0006). In 884 patients from 13 trials, pain at 1 h favored dextromethorphan (MD, -1.60; 95% CI, -1.89 to -1.31; P < 0.00001). In 950 patients from 13 trials, pain at 4 to 6 h favored dextromethorphan (MD, -0.89; 95% CI, -1.11 to -0.66; P < 0.00001). In 797 patients from 12 trials, pain at 24 h favored dextromethorphan (MD, -0.92; 95% CI, -1.24 to -0.60; P < 0.00001).

CONCLUSION

This meta-analysis suggests that dextromethorphan use perioperatively reduces the postoperative opioid consumption at 24 to 48 h and pain scores at 1, 4 to 6, and 24 h.

Role of ketamine in acute postoperative pain management: a narrative review

OBJECTIVES

The objective of this narrative review was to examine the usage of ketamine as a postoperative analgesic agent across a wide variety of surgeries.

DESIGN

A literature search was performed using the phrases "ketamine" and "postoperative pain." The authors analyzed the studies that involved testing ketamine's effectiveness at controlling postoperative pain. Effectiveness was assessed through various outcomes such as the amount of opiate consumption, visual analog scale (VAS) pain scores, and persistent postoperative pain at long-term follow-up.

RESULTS

While many different administration protocols were evaluated, delivering ketamine both as a pre- or perioperative bolus and postoperative infusion for up to 48 hours appeared to be the most effective. These effects are dose-dependent. However, a number of studies analyzed showed no benefit in using ketamine versus placebo for controlling postoperative pain. While ketamine is a safe and well-tolerated drug, it does have adverse effects, and there are concerns for possible neurotoxicity and effects on memory.

CONCLUSIONS

In a number of limited situations, ketamine has shown some efficacy in controlling postoperative pain and decreasing opioid consumption. More randomized controlled trials are necessary to determine the surgical procedures and administrations (i.e., intravenous, epidural) that ketamine is best suited for.

Long-Term Stability of Tramadol and Ketamine Solutions for Patient-Controlled Analgesia Delivery

Background

Subanesthetic doses of ketamine as an adjuvant to tramadol in patient-controlled analgesia (PCA) for postoperative pain have been shown to improve the quality of analgesia. However, there are no such commercially available drug mixtures, and the stability of the combination has rarely been assessed.

Material/Methods

Admixtures were assessed for periods of up to 14 days at 4°C and 25°C. Three different mixtures of tramadol and ketamine (tramadol 5.0 mg/mL + ketamine 0.5 mg/mL, tramadol 5.0 mg/mL + ketamine 1.0 mg/mL, and tramadol 5.0 mg/mL + ketamine 2.0 mg/mL) were prepared in polyolefin bags by combining these 2 drugs with 0.9% sodium chloride (normal saline [NS]). The chemical stability of the admixtures was evaluated by a validated high-performance liquid chromatography (HPLC) method and by measurement of pH values. Solution appearance and color were assessed by observing the samples against black and white backgrounds. Solutions were considered stable if they maintained 90% of the initial concentration of each drug.

Results

The percentages of initial concentration of tramadol and ketamine in the various solutions remained above 98% when stored at 4°C or 25°C over the testing period. No changes in color or turbidity were observed in any of the prepared solutions. Throughout this period, pH values remained stable.

Conclusions

The results indicate that the drug mixtures of tramadol with ketamine in NS for PCA delivery systems were stable for 14 days when stored in polyolefin bags at 4°C or 25°C.

Acute pain management

This article updates acute pain management in ambulatory surgery and proposes a practical three-step approach for reducing the impact and incidence of uncontrolled surgical pain. By identifying at-risk patients, implementing multimodal analgesia, and intervening promptly with rescue therapies, the anesthesiologist may improve outcomes, reduce cost, and optimize the patient's experience and quality of recovery.

Effect of intravenous patient controlled ketamine analgesiaon postoperative pain in opium abusers

Background:

Acutepostoperative pain is among the worst experience that patient scan undergo, and many analgesics have been used to suppress it; especially in chronic opium abusers. Ketamine is an N-methyl-D-aspartate antagonist analgesic, having both anesthetic and analgesic properties, which are not affected to the same extent in chronic opium abusers.

Objectives:

In this study, we assessed the analgesic effects of ketamine added to morphine as a patient-controlled analgesia method for acute pain management, compared with a placebo, inchronic maleopium abusers.

Patients and Methods:

After institutional review board approval for ethical considerations, a randomized double-blinded placebo controlled clinical trial was conducted. A total of 140 male patients aged 18-65 years, undergoing orthopedic surgery, were entered into the study after matching inclusion and exclusion criteria. All patients received the same anesthesia method; while the first group received ketamine (1mg/mL) and morphine (0.5 mg/mL) as a patient-controlled analgesia (70 patients), the second group received morphine (0.5 mg/mL) plus normal saline (70 patients). P value less than 0.05 was considered statistically significant.

Results:

The ketamine and morphine group of patients experienced less postoperative pain and required less postoperative rescue analgesia. However, the unwanted postoperative side effects were nearly the same; although increased levels of postoperative nausea and vomiting were observed in the ketamine and morphine group

Conclusions:

This study demonstrated improved analgesic effects after using intravenous patient controlled analgesia with ketamine on postoperative pain in opium abusers.

Patients with chronic pain

Preoperative evaluation of patients with chronic pain is important because it may lead to multidisciplinary preoperative treatment of patients' pain and a multimodal analgesia plan for effective pain control. Preoperative multidisciplinary management of chronic pain and comorbid conditions, such as depression, anxiety, deconditioning, and opioid tolerance, can improve patient satisfaction and surgical recovery. Multimodal analgesia using pharmacologic and nonpharmacologic strategies shifts the burden of analgesia away from simply increasing opioid dosing. In more complicated chronic pain patients, multidisciplinary treatment, including pain psychology, physical therapy, judicious medication management, and minimally invasive interventions by pain specialists, can improve patients' satisfaction and surgical outcome.

Medical management of acute pain in patients with chronic pain

The number of patients with chronic pain has increased over the years, as well as the number of patients who manage chronic pain with opioids. As prescribed opioid use has increased, so has its abuse and misuse. It has also been estimated that the number of people using opioids illicitly has doubled worldwide over the last 20 years. Management of chronic pain with opioids is associated with pathophysiological phenomena such as tolerance, dependence and hyperalgesia. They can become a problem when chronic pain patients present for a surgical procedure. Furthermore, patients who are on opioids on a regular basis require higher amounts during the perioperative period. The perioperative management of the chronic pain patient is difficult and complex. Developing an appropriate plan that can fulfill patients' and surgical team's needs requires skills and experience. The aim of this review is to describe the options available for the optimal perioperative management of acute pain in patients with a history of chronic pain.

Effects of low-dose IV ketamine on peripheral and central pain from major limb injuries sustained in combat

OBJECTIVE

Examine response patterns to low-dose intravenous (IV) ketamine continuous infusions on multiple pain outcomes, and demonstrate effectiveness, safety, and tolerability of ketamine administration on general wards.

DESIGN

Retrospective case series of consecutive patients given low-dose IV ketamine continuous infusions.

SETTING

Walter Reed Army Medical Center, Washington, DC.

PATIENTS

Nineteen eligible inpatients with neuropathic pain from major limb injuries sustained in combat with inadequate pain control from multimodal analgesia.

INTERVENTIONS

A 3-day IV infusion of ketamine at doses ≤ 120 μg/kg/h.

OUTCOME MEASURES

Daily present (PPI), average (API), and worst (WPI) pain intensity (0-10), global pain relief (GPR) (1 "no relief" to 5 "complete relief"), daily assessments of adverse events, and daily opioid requirements measured during therapy.

RESULTS

A significant reduction in PPI (P < 0.001) and improvement in GPR (P = 0.031) was noted over time. Higher baseline WPI (≥ 7; N = 4) was associated with a significant decrease in WPI (P = 0.0388), but lower baseline WPI (N = 5) was not. Significant mean percent decreases in PPI with higher baseline PPI (N = 8; P = 0.0078) and WPI with no phantom limb pain (PLP) (N = 10; P = 0.0436) were observed. Mean percent increase in overall GPR was better for those reporting GPR scores ≤ 3 (N = 13) in the first 24 hours of therapy (P = 0.0153). While not significant, mean opioid requirement (IV morphine equivalents) decreased from 129.9 mgs ± 137.3 on day 1 to 112.14 ± 86.3 24 hours after therapy.

CONCLUSIONS

Low-dose ketamine infusions for complex combat injury pain were safe and effective, and demonstrated response patterns over time and by baseline pain score stratification and presence or absence of PLP.

Evaluation of the efficacy of memantine in the treatment of fibromyalgia: study protocol for a doubled-blind randomized controlled trial with six-month follow-up

Background

Fibromyalgia is a prevalent chronic rheumatic disease of great clinical importance. Recent studies have found raised levels of glutamate in the insula, hippocampus and posterior cingulate cortex regions of the brains of fibromyalgia (FM) patients. This finding has led researchers to speculate about the usefulness of glutamate-blocking drugs such as memantine in the treatment of fibromyalgia. The hypothesis of this study is that the administration of memantine will reduce the glutamate levels, and futhermore, will decrease the perceived pain. The aim of this study is to evaluate the efficacy of memantine in the treatment of pain (pain perception). A secondary objective is to evaluate the efficacy of memantine in the treatment of other clinical symptoms of FM, and to evaluate the efficacy of memantine in reducing brain levels of glutamate, and its effects on the central nervous system as a whole.

Method/Design

A double-blind parallel randomized controlled trial. Participants, Seventy patients diagnosed with FM will be recruited from primary health care centers in Zaragoza, Spain. Intervention. The subjects will be randomized in two groups: A) A treatment group (n = 35), which will receive 20 mg of memantine daily; B) A control group (n = 35), to which will be administered a placebo. There will be a six-month follow-up period (including a titration period of one month). Outcomes. The main efficacy variable of this study is pain (pain perception). The secondary efficacy variables are clinical symptoms (pain threshold, cognitive function, health status, anxiety, depression, clinical impression and quality of life) and glutamate levels in different regions of the brain, which will be assessed by magnetic resonance spectroscopy. Randomization and blinding. Randomization has been computer-generated, and the random allocation sequence will be implemented by telephone. Subjects of the study and the research assistants will be blinded to group assignment.

Discussion

There is a need for the development of innovative and more effective treatments for fibromyalgia. This clinical trial will determine whether memantine can be an effective pharmacological treatment for fibromyalgia patients.

Trial registration

Current Controlled Trials http://ISRCTN45127327 EUDRACT 2011-006244-73

Multimodal pain management after total joint arthroplasty

Adequate postoperative pain control in patients who have undergone total joint arthroplasty allows faster rehabilitation and reduces the rate of postoperative complications. Multimodal pain management involves the introduction of adjunctive pain control methods in an attempt to control pain with less reliance on opioids and fewer side effects. Current research suggests that traditional nonsteroidal anti-inflammatory drugs (NSAIDs) and the associated cyclooxygenase type-2 (COX-2) inhibitors improve pain control in most cases. Nearly all multimodal pain management modalities have a safe side-effect profile when they are added to existing methods. The exception is the administration of DepoDur (extended-release epidural morphine) to elderly or respiratory-compromised patients because of a potential for hypoxia and cardiopulmonary events.

The role of multimodal analgesia in pain management after ambulatory surgery

PURPOSE OF REVIEW

As outpatient (day-case) surgery had continued to grow throughout the world, many more complex and potentially painful procedures are being routinely performed in the ambulatory setting. Opioid analgesics, once considered the standard approach to preventing acute postoperative pain, are being replaced by a combination of nonopioid analgesic drugs with diverse modes of action as part of a multimodal approach to preventing pain after ambulatory surgery. This review will provide an update on the topic of multimodal pain management for ambulatory (day-case) surgery.

RECENT FINDINGS

Efficacy of multimodal analgesic regimens continues to improve; opioid analgesics are increasingly taking on the role of 'rescue analgesics' for acute pain after day-case surgery. The use of multimodal analgesia is rapidly becoming the 'standard of care' for preventing pain after ambulatory procedures at most surgery centers throughout the world.

SUMMARY

This article discusses recent evidence from the peer-reviewed literature regarding the role of local anesthetics, NSAIDs, gabapentinoids, and acetaminophen, as well as alpha-2 agonists, ketamine, esmolol, and nonpharmacologic approaches (e.g., transcutaneous electrical stimulation) as parts of multimodal pain management strategies in day-case surgery.

Rabbit analgesia

With the increasing popularity of rabbits as household pets, the complexity of diagnostic and surgical procedures performed on rabbits is increasing, along with the frequency of routine surgical procedures. More practitioners are faced with the need to provide adequate analgesia for this species. Preemptive analgesia prior to planned surgical interventions may reduce nervous system changes in response to noxious input, as well as reduce postoperative pain levels and analgesic drug requirements. Concurrent administration of analgesic drugs to anesthetized rabbits undergoing painful procedures is warranted both pre- and intraoperatively as well as postoperatively. This article discusses the neuropharmacologic and pharmacologic aspects of pain in rabbits, and reviews current protocols for the use of analgesic drugs.

Postoperative pain management after ambulatory surgery: role of multimodal analgesia

Multimodal (or balanced) analgesia represents an increasingly popular approach to preventing postoperative pain. The approach involves administering a combination of opioid and nonopioid analgesics. Nonopioid analgesics are increasingly being used as adjuvants before, during, and after surgery to facilitate the recovery process after ambulatory surgery. Early studies evaluating approaches to facilitating the recovery process have demonstrated that the use of multimodal analgesic techniques can improve early recovery as well as other clinically meaningful outcomes after ambulatory surgery. The potential beneficial effects of local anesthetics, NSAIDs, and gabapentanioids in improving perioperative outcomes continue to be investigated.

Effects of perioperative S (+) ketamine infusion added to multimodal analgesia in patients undergoing ambulatory haemorrhoidectomy

Background and objective

Perioperative low-dose ketamine has been useful for postoperative analgesia. In this study we wanted to assess the analgesic effect and possible side-effects of perioperative low-dose S (+) ketamine when added to a regime of non-opioid multimodal pain prophylaxis.

Methods

Seventy-seven patients scheduled for haemorrhoidectomy were enrolled in this randomized, double-blind, controlled study. They received oral paracetamol 1–2 g, total intravenous anaesthesia, intravenous 8 mg dexamethasone, 30 mg ketorolac and local infiltration with bupivacaine/epinephrine. Patients randomized to S (+) ketamine received an intravenous bolus dose of 0.35 mg kg−1 S (+) ketamine before start of surgery followed by continuous infusion of 5 μg kg−1 min−1 until 2 min after end of surgery. Patients in the placebo group got isotonic saline (bolus and infusion). BISTM monitoring was used. Pain intensity and side-effects were assessed by blinded nursing staff during PACU stay and by phone 1, 7 and 90 days after surgery.

Results

In patients randomized to S (+) ketamine emergence from anaesthesia was significantly longer (13.1 min vs. 9.3 min; p < 0.001). BIS values were significantly higher during anaesthesia (maximal value during surgery: 62 vs. 57; p = 0.01) and when opening eyes (81 vs. 70, p < 0.001). Pain scores (NRS and VAS) did not differ significantly between groups.

Conclusions

The addition of perioperative S (+) ketamine for postoperative analgesia after haemorrhoidectomy on top of multimodal non-opioid pain prophylaxis does not seem to be warranted, due to delayed emergence and recovery, more side-effects, altered BIS readings and absence of additive analgesic effect.