Useful adjuvants for postoperative pain management

Assessment of the impact of gabapentin on postoperative pain following shoulder open rotator cuff repair: a double-blind clinical trial

BACKGROUND

Gabapentin is an anticonvulsant used for managing neuropathic pain. Its effectiveness and dosing strategies for postoperative pain, particularly in open shoulder rotator cuff repair, are still debated. This study assesses gabapentin's impact on postoperative pain intensity in open rotator cuff repair.

METHODS

Sixty eligible patients were randomly distributed into 2 groups: placebo and gabapentin. The gabapentin group received a daily dose of 600 mg, administered in 2 divided increments, beginning 3 days before the surgery and continuing for 1 week postoperatively. Pain intensity, assessed via the Visual Analog Scale, was the primary endpoint during the first postoperative week. Secondary aims conducted on both groups included quantifying opioid consumption, evaluation of side effects attributed to gabapentin and opioids, assessment of sleep quality, and patients' satisfaction levels with the employed approach.

RESULT

Postoperative pain in the gabapentin group significantly decreased from the first 24 hours until the fourth day postsurgery (P < .002), accompanied by reduced opioid consumption (P = .02). Following discharge, the prevalence of nocturnal sleep disruptions and oxycodone consumption in the gabapentin group notably decreased compared to the placebo group, alongside a significant improvement in sleep quality and duration until the fifth day, as well as overall satisfaction with the pain management approach seen within the gabapentin group (P = .003).

CONCLUSION

Administering gabapentin perioperatively at 600 mg daily and divided over a minimum duration of 4 days postoperatively may significantly reduce postoperative pain intensity and opioid consumption in open shoulder rotator cuff repair surgery patients.

Pronociceptive role of spinal Cav2.3 (R-type) calcium channels in a mouse model of postoperative pain

BACKGROUND

More than 80% of patients may experience acute pain after a surgical procedure, and this is often refractory to pharmacological intervention. The identification of new targets to treat postoperative pain is necessary. There is an association of polymorphisms in the Cav2.3 gene with postoperative pain and opioid consumption. Our study aimed to identify Cav2.3 as a potential target to treat postoperative pain and to reduce opioid-related side effects.

EXPERIMENTAL APPROACH

A plantar incision model was established in adult male and female C57BL/6 mice. Cav2.3 expression was detected by qPCR and suppressed by siRNA treatment. The antinociceptive efficacy and safety of a Cav2.3 blocker-alone or together with morphine-was also assessed after surgery.

KEY RESULTS

Paw incision in female and male mice caused acute nociception and increased Cav2.3 mRNA expression in the spinal cord but not in the incised tissue. Intrathecal treatment with siRNA against Cav2.3, but not with a scrambled siRNA, prevented the development of surgery-induced nociception in both male and female mice, with female mice experiencing long-lasting effects. High doses of i.t. SNX-482, a Cav2.3 channel blocker, or morphine injected alone, reversed postoperative nociception but also induced side effects. A combination of lower doses of morphine and SNX-482 mediated a long-lasting reversal of postsurgical pain in female and male mice.

CONCLUSION

Our results demonstrate that Cav2.3 has a pronociceptive role in the induction of postoperative pain, indicating that it is a potential target for the development of therapeutic approaches for the treatment of postoperative pain.

Cesarean Sections Under Spinal Anaesthesia: Comparison of Varying Doses of Dexmedetomidine Combined with 0.75% Hyperbaric Ropivacaine: A Double-Blind Randomized Trial

Objective

The primary aim of this study was to evaluate the effects of 5 μg, 7.5 μg, and 10 μg doses of dexmedetomidine added to hyperbaric 0.75% ropivacaine on the duration of analgesia during cesarean section. Furthermore, the onset of sensory and motor block, hemodynamics, sedation, and adverse effects were investigated.

Methods

A total of 120 full-term parturients scheduled for cesarean section under spinal anaesthesia were randomized into three groups. Group RD5 received intrathecal hyperbaric 0.75% ropivacaine 15 mg (2 mL) plus dexmedetomidine 5 μg (0.5 mL), group RD7.5 received intrathecal hyperbaric 0.75% ropivacaine 15 mg (2 mL) plus dexmedetomidine 7.5 μg (0.5 mL), and group RD10 received intrathecal hyperbaric 0.75% ropivacaine 15 mg (2 mL) plus dexmedetomidine 10 μg (0.5 mL). Sensorimotor blockade characteristics, analgesia duration, hemodynamic variables, and adverse events were documented. Student's t-test and the chi-square test were used for data analysis.

Results

In groups RD5, RD7.5, and RD10, the onset of sensory block was 2.96±1.32 min, 2.26±1.50 min, and 1.96±0.93 min, respectively, while the onset of motor block was 9.63±0.11 min, 8.63±0.58 min, and 6.40±0.14 min, respectively. The duration of analgesia was significantly prolonged in group RD10 compared with groups RD7.5 and RD5 (483.43±76.21 vs. 398.74±73.59 vs. 362.58±79.87 min, respectively, P=0.001). Group RD10 also exhibited significantly higher incidences of sedation, bradycardia, and vomiting.

Conclusion

We conclude that increasing dexmedetomidine doses decreases the onset of sensory and motor blockade while prolonging analgesia duration in a dose-dependent manner.

Duloxetine reduces opioid consumption and pain after total hip or knee arthroplasty: a meta-analysis of randomized controlled trials

PURPOSE

There is no consensus in the current literature on the analgesic role of duloxetine after total hip arthroplasty (THA) or total knee arthroplasty (TKA). Thus, we designed this meta-analysis to reveal the analgesic effectiveness and safety of duloxetine in TKA or THA.

METHODS

As of October 2022, two authors (L.C. and W.Q.J.) independently searched five main databases (EMBASE, Web of Science, PubMed, Cochrane Library, and Google Scholar) to find relevant studies. Duloxetine vs. placebo in randomized controlled trials (RCTs) for THA or TKA were included. We set perioperative total opioid consumption as the primary outcome. Secondary outcomes included resting or dynamic pain scores over time, gastrointestinal adverse events, neurological adverse events, and other adverse reactions.

RESULTS

Eight RCTs with 695 patients were incorporated in our study. This meta-analysis showed high evidence that duloxetine was effective in reducing perioperative opioid consumption (Standard mean difference [SMD] = - 0.50, 95% confidence intervals [CI]: -0.70 to - 0.31, P < 0.00001) and low to moderate evidence that duloxetine could reduce pain within three weeks after surgery. Low to high evidence showed no differences between the two groups for most adverse events. Substantial evidence suggests that duloxetine can reduce nausea and vomiting after surgery (Risk ratio [RR] = 0.69, 95% CI: 0.50 to 0.95, P = 0.02, I2 = 4%). However, moderate evidence suggested that duloxetine might be associated with increased postoperative drowsiness (RR = 1.83, 95% CI: 1.08 to 3.09, P = 0.02, I2 = 0%).

CONCLUSION

Duloxetine reduced overall opioid consumption in the perioperative period and relieved pain within three weeks after surgery without increasing the risk of adverse drug events. Duloxetine can be part of a multimodal management regimen in patients with THA and TKA.

Transversus Abdominis Plane Block as a Strategy for Effective Pain Management in Patients with Pain during Laparoscopic Cholecystectomy: A Systematic Review

Laparoscopic cholecystectomy (LC), unlike laparotomy, is an invasive surgical procedure, and some patients report mild to moderate pain after surgery. Transversus abdominis plane (TAP) block has been shown to be an appropriate method for postoperative analgesia in patients undergoing abdominal surgery. However, there have been few studies on the efficacy of TAP block after LC surgery, with unclear information on the optimal dose, long-term effects, and clinical significance, and the analgesic efficacy of various procedures, hence the need for this review. Five electronic databases (PubMed, Academic Search Premier, Web of Science, CINAHL, and Cochrane Library) were searched for eligible studies published from inception to the present. Post-mean and standard deviation values for pain assessed were extracted, and mean changes per group were calculated. Clinical significance was determined using the distribution-based approach. Four different local anesthetics (Bupivacaine, Ropivacaine, Lidocaine, and Levobupivacaine) were used at varying concentrations from 0.2% to 0.375%. Ten different drug solutions (i.e., esmolol, Dexamethasone, Magnesium Sulfate, Ketorolac, Oxycodone, Epinephrine, Sufentanil, Tropisetron, normal saline, and Dexmedetomidine) were used as adjuvants. The optimal dose of local anesthetics for LC could be 20 mL with 0.4 mL/kg for port infiltration. Various TAP procedures such as ultrasound-guided transversus abdominis plane (US-TAP) block and other strategies have been shown to be used for pain management in LC; however, TAP blockade procedures were reported to be the most effective method for analgesia compared with general anesthesia and port infiltration. Instead of 0.25% Bupivacaine, 1% Pethidine could be used for the TAP block procedures. Multimodal analgesia could be another strategy for pain management. Analgesia with TAP blockade decreases opioid consumption significantly and provides effective analgesia. Further studies should identify the long-term effects of different TAP block procedures.

Multimodal Analgesia

Perioperative pain management is one of the domains in which Anesthesiologists are intricately involved, and which is immensely important. Adequate postoperative analgesia is central to avoid both the acute as well as chronic complications of uncontrolled postoperative pain. Preventive analgesia has been identified as an approach to mitigate the phenomenon of central sensitization, which plays an important role in the development of chronic pain after surgery. As an over-reliance on opioids for peri- and postoperative pain control is associated with opioid dependence and hyperalgesia, multimodal analgesia has taken center stage. Multimodal analgesia, in theory, will optimize perioperative pain control, reduce the chance of central sensitization, and avoid the detrimental effects of opioid overuse. Multiple classes of systemic analgesic medications have been used to accomplish these tasks, and the aim of this article is to outline these medications, their mechanisms of action, as well as the evidence behind their individual roles in multimodal analgesia. Regional anesthesia has also been embraced as a key component of multimodal analgesia in orthopedic surgery; however, over the past several years, local infiltration analgesia (LIA) emerged as a viable alternative, particularly in total knee arthroplasty.

[Role of Dexamethasone for Pain Management in Intervertebral Disc Surgery]

Intervertebral disc operations are already among the most common and their frequency is increasing. The pain associated with these operations is one of the most common postoperative discomforts, has a significant impact on psychosocial aspects, and should therefore be treated effectively. Therefore, we present the importance of dexamethasone for multimodal pain management after intervertebral disc surgery.

The Nuts and Bolts of a Successful Non-Narcotic Perioperative Enhanced Recovery After Surgery Protocol

BACKGROUND

Enhanced recovery after surgery (ERAS) protocols are widely utilized approaches to perioperative care that advocate preoperative counseling, multimodal perioperative medication management, and early postoperative mobilization to improve post-surgical patient outcomes and satisfaction.

OBJECTIVES

The authors aimed to elucidate the mechanism by which each medication utilized in the senior author's ERAS protocol acts, determine the efficacy of this protocol in postoperative pain management, and reveal other factors that may play a role in patients' degree of postoperative pain.

METHODS

A literature review was performed on the medications utilized in the senior author's ERAS protocol. Evidence from the author's previous study on the efficacy of this regimen and anecdotal evidence regarding the psychological component of pain was also compiled.

RESULTS

There is evidence that an ERAS protocol is as effective if not more effective than regimens involving opioid medications in management of postoperative pain. These medications act synergistically to block perception of pain by multiple pathways, while minimizing adverse effects that may be associated with high doses of a single medication and are affordable for both the patient and the surgeon.

CONCLUSIONS

ERAS protocols effectively manage postoperative pain while avoiding the adverse effects associated with opioid medications. Although an emphasis has often been placed on the medications involved in various protocols and avoidance of opioid medications, appropriate counseling on patients' expectations concerning postoperative "pain" or discomfort and a systemic shift in the approach to perioperative pain are perhaps the most important components to holistic non-narcotic postoperative care.

Low-Dose Ketamine Infusion as Adjuvant Therapy during an Acute Pain Crisis in Pediatric Patients

Recent studies in pediatric patients have suggested that ketamine, an N-methyl-D-aspartate receptor (NMDA) antagonist, given at sub-anesthetic doses can effectively decrease pain scores, provide analgesic effects, and in some cases, reduce opioid requirements. Our study aims to assess impact of low-dose ketamine on reducing pain scores and total opioid requirements during an acute pain crisis in pediatric patients. From November 2016 to December 2018, eight patients between the ages of 2 and 17 years admitted to the pediatric intensive care unit (PICU) were treated with LDK infusions to manage severe, opioid-refractory, acute pain crises. Subjective pain scores and total morphine milligram equivalent (MME) intake before, during, and after ketamine infusion were collected through a structured chart review. Overall, the addition of ketamine appeared to reduce subjective pain scores and opioid requirements. Two patients were in palliative care and expired shortly after ketamine was started and two patients were discharged within 48 hours of LDK infusion cessation. Ketamine seemed to reduce heart rate and had no appreciable effect on respiratory rate, blood pressure, or oxygen saturation. Hallucination was reported in one patient which resolved upon dose reduction. LDK infusion could be considered as an adjuvant therapy to optimize pain control in pediatric patients experiencing acute pain crises. Further investigation with a larger patient population is warranted to establish the effects of LDK on pain improvement and reducing total opioid requirements.

Intravenous patient-controlled analgesia: in vitro stability profiles of mixtures containing fentanyl, hydromorphone, oxycodone, nefopam, ondansetron, and ramosetron

Background and objectives

Patient-controlled analgesia often involves combinations of multiple drugs. This study aimed to determine the stability of drug mixtures commonly used for intravenous patient-controlled analgesia.

Materials and methods

We examined four of the most commonly used drug combinations in intravenous patient-controlled analgesia at our institution. Mixtures contained fentanyl (400 μg), either oxycodone (10 mg) or hydromorphone (4 mg), nefopam (20 mg), and either ondansetron (10 mg) or ramosetron (0.3 mg). Each drug mixture was diluted in 0.9% saline and stored in a portable patient-controlled analgesia system at room temperature (24 °C) for 96 h. Physical attributes including color, turbidity, and precipitation were assessed using digital imaging and optical microscopy. Sterility testing was conducted to assess for microbiological contamination. The pH of each mixture was monitored for up to 96 h after mixing. The concentration of each drug in the mixture was also evaluated using high-performance liquid chromatography.

Results

All mixtures remained colorless and transparent with no visible sediment for 96 h. After 14 days of culture, none of the samples showed bacterial or fungal growth. The pH for all mixtures was maintained between 4.17 and 5.19, and the mean pH change in any mixture was less than 0.4 over the study period. The concentration of each drug remained between 90 and 110% of the initial value for 96 h after mixing.

Conclusion

Four drug mixtures commonly used for intravenous patient-controlled analgesia are physiochemically stable and remain sterile for 96 h after mixing.

Six-year trends in postoperative prescribing and use of multimodal analgesics following total hip and knee arthroplasty: A single-site observational study of pain management

BACKGROUND

Guidelines for acute postoperative pain management recommend administering analgesics in multimodal combination to facilitate synergistic benefit, reduce opioid requirements and decrease side-effects. However, limited observational research has examined the extent to which multimodal analgesics are prescribed and administered postoperatively following joint replacement.

METHODS

In this longitudinal study, we used three-point prevalence surveys to observe the 6-year trends in prescribing and use of multimodal analgesics on the orthopaedic wards of a single Australian private hospital. We collected baseline postoperative data from total hip and knee arthroplasty patients in May/June 2010 (Time 1, n = 86), and follow-up data at 1 year (Time 2, n = 199) and 5 years (Time 3, n = 188). During the follow-up, data on prescribing practices were presented to anaesthetists.

RESULTS

We found a statistically significant increase in the prescribing (p < 0.001) and use (p < 0.001) of multimodal analgesics over time. The use of multimodal analgesics was associated with lower rest pain (p = 0.027) and clinically significant reduction in interference with activities (p < 0.001) and sleep (p < 0.001). However, dynamic pain was high and rescue opioids were likely under-administered at all time points. Furthermore, while patients reported high levels of side-effects, use of adjuvant medications was low.

CONCLUSIONS

We observed significant practice change in inpatient analgesic prescribing in favour of multimodal analgesia, in keeping with contemporary recommendations. Surveys, however, appeared to identify a clinical gap in the bedside assessment and management of breakthrough pain and medication side-effects, requiring additional targeted interventions.

SIGNIFICANCE

Evaluation of 6-year trends in a large Australian metropolitan private hospital indicated substantial growth in postoperative multimodal analgesic prescribing. In the context of growing global awareness concerning multimodal analgesia, findings suggested diffusion of best-evidence prescribing into clinical practice. Findings indicated the effects of postoperative multimodal analgesia in real-world conditions outside of experimental trials. Postoperative multimodal analgesia in the clinical setting was only associated with a modest reduction in rest pain, but substantially reduced interference from pain on activities and sleep.

Opioid Adjuncts: Optimizing Opioid Therapy With Nonopioid Medications

In this article, we describe a variety of medications that physicians managing outpatient chronic pain should familiarize themselves with to better aid their approach to multimodal pain therapy. Physicians should always consider the use of an adjuvant or coanalgesic drug as first-line treatments. Although many of these medications are not primarily analgesics, in clinical practice they have independent analgesic effects or synergistic analgesic properties when used with opioids. The use of adjunct analgesics reduces opioid-related adverse effects and optimizes pain management. Although there may be some medication overlap with this section and the ERAS section, the purpose of this article is to understand prolonged use in the outpatient setting to reduce opioid use or limit opioid dose with adjuvant therapy.

A Narrative Review of the Evidence on the Efficacy of Dexamethasone on Postoperative Analgesic Consumption

OBJECTIVES

The effect of dexamethasone on analgesic consumption has not been adequately studied. The aim of this review was to investigate recent literature regarding the possible effect of dexamethasone on postoperative analgesic consumption.

METHODS

Critical review of randomized trials and prospective consecutive studies investigating the postoperative analgesic effect of dexamethasone was performed. Only studies published during 2006 to 2015 were included.

RESULTS

Forty-one studies met the inclusion criteria; 33 in adults and 8 in children (9 in general surgery, 8 in gynecologic/breast surgery, 8 in orthopedic/spinal surgery, 8 in head/neck surgery, 7 in children's tonsillectomy, and 1 in children's orchiopexy). Literature review demonstrated that dexamethasone can decrease analgesic requirements in patients undergoing laparoscopic cholecystectomies, laparoscopic gynecologic and breast surgery; whereas there is no consensus regarding orthopedic procedures, with positive evidence mostly regarding spinal surgeries. The efficacy of dexamethasone during head and neck surgery is not conclusive; however, its use before thyroid surgery may be beneficial. In children a beneficial impact of dexamethasone administration was revealed on posttonsillectomy reduction of analgesic needs. Studies on other kinds of operations in children are lacking.

CONCLUSIONS

Dexamethasone administered at a dose of 8 mg before surgical incision may be beneficial in laparoscopic cholecystectomies, thyroid, laparoscopic gynecologic and breast surgery, and tonsillectomies in children. Dexamethasone's potential impact on reducing postoperative analgesic requirements should be investigated in more detail in a systematic manner, to support its use in other kinds of operations.

Time-dependent analysis of dosage delivery information for patient-controlled analgesia services

Pain relief always plays the essential part of perioperative care and an important role of medical quality improvement. Patient-controlled analgesia (PCA) is a method that allows a patient to self-administer small boluses of analgesic to relieve the subjective pain. PCA logs from the infusion pump consisted of a lot of text messages which record all events during the therapies. The dosage information can be extracted from PCA logs to provide easily understanding features. The analysis of dosage information with time has great help to figure out the variance of a patient’s pain relief condition. To explore the trend of pain relief requirement, we developed a PCA dosage information generator (PCA DIG) to extract meaningful messages from PCA logs during the first 48 hours of therapies. PCA dosage information including consumption, delivery, infusion rate, and the ratio between demand and delivery is presented with corresponding values in 4 successive time frames. Time-dependent statistical analysis demonstrated the trends of analgesia requirements decreased gradually along with time. These findings are compatible with clinical observations and further provide valuable information about the strategy to customize postoperative pain management.

"Comparison of Nalbuphine Hydrochloride and Fentanyl as an Adjuvant to Bupivacaine for Spinal Anesthesia in Lower Abdominal Surgeries:" A Randomized, Double-blind Study

Background and Aims

Opioids have been favored as adjuvants to local anesthetics during spinal anesthesia. Nalbuphine, a μ-receptor antagonist and ĸ-receptor agonist, seems to be a suitable adjuvant to local anesthetics. The aim of this study was to compare postoperative analgesia and adverse effects of nalbuphine and fentanyl when used as an adjuvant to hyperbaric bupivacaine during spinal anesthesia.

Materials and Methods

Sixty patients belonging to the American Society of Anesthesiologists Physical Status I and II were randomly allocated into two groups of thirty each. Patients in bupivacaine nalbuphine group (Group BN) received 0.8 mg (0.3 ml) of nalbuphine with 12.5 mg (2.5 ml) of 0.5% hyperbaric bupivacaine diluted to 3 ml and bupivacaine-fentanyl group (Group BF) received 25 μg (0.5 ml) of fentanyl with 12.5 mg (2.5 ml) of 0.5% hyperbaric bupivacaine. Patients were assessed for hemodynamic changes, sensory and motor block, early postoperative analgesia, and adverse effects.

Results

Onset, duration of sensory and motor block, and duration of effective analgesia were comparable between both groups. Postoperative visual analog scale score was 4.8 ± 1.12 in Group BN, and in Group BF, it was 3.86 ± 1.04 which was statistically highly significant (P = 0.0007). The number of patients demanding rescue analgesia in early postoperative period was 18 (60.0%) in Group BN and 7 (23.33%) in Group BF which was statistically significant (P = 0.004).

Conclusion

Fentanyl was more efficient than nalbuphine in providing early postoperative analgesia when used as an adjuvant to hyperbaric bupivacaine.

Decreasing postoperative narcotics in reconstructive pelvic surgery: a randomized controlled trial

BACKGROUND

Postoperative pain control is crucial to any successful recovery plan. Many currently used medication regimens are narcotic-focused.

OBJECTIVE

The objective of our study was to evaluate the efficacy of a multimodal pain regimen after pelvic reconstructive surgery.

STUDY DESIGN

The primary outcome measure was narcotic use. Secondary outcomes included pain, nausea, and constipation. Patients were randomized to either usual care postoperative treatment or multimodal pain regimen. Usual care included no specific preoperative or intraoperative medications, and postoperative narcotics with ibuprofen. Multimodal pain regimen included preoperative and postoperative celecoxib, gabapentin, intraoperative and postoperative intravenous and oral acetaminophen and ibuprofen, and narcotics as needed. All narcotics were converted to milligram equivalents of oral morphine for standardization according to Centers for Disease Control and Prevention guidelines where conversion factors for oral hydrocodone = 1, oral oxycodone = 1.5, and oral hydromorphone = 4. Patients were given the validated Brief Pain Inventory survey preoperatively (baseline), at postoperative day 1, and 1 week postoperatively. At 1 week, bowel function and narcotics usage was assessed.

RESULTS

Seventy patients were randomized to the usual care arm and 68 to the multimodal pain regimen arm. Patients in the multimodal pain regimen arm used significantly fewer intravenous narcotics in the operating room (90.7 ± 39.1 mg vs 104.6 ± 33.5 mg; P = .026) and while in the hospital (10.8 ± 15.1 mg vs 31.2 ± 29.6 mg; P < .001) and were more likely to use 0 oral narcotics after discharge to home (34.8% of patients vs 10.6%; P = .001). Of the patients who did use oral narcotics after discharge to home, there was no difference in amount used between groups (121.3 ± 103.7 mg in the multimodal pain regimen arm vs 153.0 ± 113.8 mg in the usual care arm; P = .139). Total narcotic usage (operating room + hospital + home) was significantly less in the multimodal pain regimen arm of the study (195.5 ± 147.2 mg vs 304.0 ± 162.1 mg; P < .001). There were no significant differences in pain scores between the 2 arms of the study on either postoperative time point. There were no significant differences in antiemetic use while in hospital, consistency of first bowel movement, length of stay, or number of telephone calls to nurses in first 3 weeks postoperatively.

CONCLUSION

A multimodal pain regimen in pelvic reconstructive surgery was found to decrease postoperative opioid requirements, while providing equivalent pain control.

Perioperative pregabalin for reducing pain, analgesic consumption, and anxiety and enhancing sleep quality in elective neurosurgical patients: a prospective, randomized, double-blind, and controlled clinical study

OBJECTIVE

The aim of this study was to assess in-hospital (immediate) postoperative pain scores and analgesic consumption (primary goals) and preoperative anxiety and sleep quality (secondary goals) in patients who underwent craniotomy and were treated with pregabalin (PGL). Whenever possible, out-of-hospital pain scores and analgesics usage data were obtained as well.

METHODS

This prospective, randomized, double-blind and controlled study was conducted in consenting patients who underwent elective craniotomy for brain tumor resection at Tel Aviv Medical Center between 2012 and 2014. Patients received either 150 mg PGL (n = 50) or 500 mg starch (placebo; n = 50) on the evening before surgery, 1.5 hours before surgery, and twice daily for 72 hours following surgery. All patients spent the night before surgery in the hospital, and no other premedication was administered. Opioids and nonsteroidal antiinflammatory drugs were used for pain, which was self-rated by means of a numerical rating scale (score range 0–10).

RESULTS

Eighty-eight patients completed the study. Data on the American Society of Anesthesiologists class, age, body weight, duration of surgery, and intraoperative drugs were similar for both groups. The pain scores during postoperative Days 0 to 2 were significantly lower in the PGL group than in the placebo group (p < 0.01). Analgesic consumption was also lower in the PGL group, both immediately and 1 month after surgery. There were fewer requests for antiemetics in the PGL group, and the rate of postoperative nausea and vomiting was lower. The preoperative anxiety level and the quality of sleep were significantly better in the PGL group (p < 0.01). There were no PGL-associated major adverse events.

CONCLUSIONS

Perioperative use of twice-daily 150 mg pregabalin attenuates preoperative anxiety, improves sleep quality, and reduces postoperative pain scores and analgesic usage without increasing the rate of adverse effects.

Clinical trial registration no.: NCT01612832 (clinicaltrials.gov)

Arthroscopic bankart surgery: Does gabapentin reduce postoperative pain and opioid consumption? A triple-blinded randomized clinical trial

BACKGROUND

The role of gabapentin as preemptive analgesia in managing acute pain following shoulder bankart arthroscopy is controversial and the studies addressing this issue are limited.

HYPOTHESIS

The present study was undertaken to examine the effects of preemptive single dose of gabapentin on pain management and opioid consumption in patients undergoing arthroscopic bankart surgery.

PATIENTS AND METHODS

In the current triple-blinded randomized clinical trial, 76 eligible patients were randomly divided into two groups either taking gabapentin 600mg (G group) or placebo (P group). The primary outcomes were pain intensity assessed based on Visual Analogue Scale (VAS) and secondary outcomes were opioid consumption and side effects, dizziness, sedation, nausea and vomiting at 6h and 24h follow-up visits.

RESULTS

The pain intensity were not significantly different between the G and P groups (P>0.05). The opioid consumption, however, was significantly reduced in G group at both 6h and 24h follow-up visits (P<0.001). Dizziness and sedation were similar in both groups. Nausea and vomiting were significantly lower in G group only at 6h visit but similar at 24h follow-up visit (P<0.001).

DISCUSSION

The preemptive single dose of gabapentin 600mg administered prior to arthroscopic bankart surgery does not decrease post-operation pain, but reduces opioid consumption. Gabapentin restrained postoperative nausea and vomiting for a short while (less than 6h).

LEVEL OF EVIDENCE

Level I, treatment study.

Perioperative management in children with chronic pain

Children with chronic pain often undergo surgery and effective perioperative management of their pain can be challenging. Identification of the pediatric chronic pain patient preoperatively and development of a perioperative pain plan may help ensure a safer and more comfortable perioperative course. Successful management usually requires multiple different classes of analgesics, regional anesthesia, and adjunctive nonpharmacological therapies. Neuropathic and oncological pain can be especially difficult to treat and usually requires an individualized approach.

Adding magnesium sulfate to bupivacaine in transversus abdominis plane block for laparoscopic cholecystectomy: A single blinded randomized controlled trial

INTRODUCTION AND AIM

Use of transversus abdominis plane block (TAP) in the management of postoperative pain after the laparoscopic cholecystectomy (LC) has been a common anesthetic practice. This study evaluates the effect of adding magnesium sulfate to bupivacaine in TAP block in LC regarding postoperative analgesia and analgesic consumption.

PATIENTS AND METHODS

Ninety patients of American Society of Anesthesiologists I and II was divided into three groups: Control group (C group, n = 30), bupivacaine group (B group, n = 30), bupivacaine magnesium group (M group, n = 30).

RESULTS

M group showed better analgesic profile in the 1(st) postoperative day in the form of lower mean visual analog scale score (2.8 ± 0.6 for C group, 2.1 ± 0.5 for B group, 2.2 ± 0.5 for M group, P < 0.001), longer duration of analgesia (7 ± 2.8 h for C group, 16 ± 2.5 h for B group, 19 ± 2.2 h for M group, P < 0.006), lower morphine consumption (2 ± 0.1 mg for C group, 0.9 ± 0.1 mg for B group, 0.5 ± 0.1 mg for M group, P < 0.011). There was a significant lower incidence of postoperative nausea and vomiting (PONV) (32% for C group, 6% B group, 7% M group, P < 0.004).

CONCLUSION

Adding MgSo4 as an adjuvant to bupivacaine in TAP block; during anesthesia for LC; improved postoperative analgesia in the form of increased duration, decreased analgesic requirements and PONV.

The late effect of intraoperative wound infiltration with local anaesthetic in surgical patients; is there any? A randomized control trial

INTRODUCTION

Intraoperative wound infiltration with local anaesthetic is commonly used. Apart from the obvious immediate action it has been supported that a possible down regulation of pain receptors may lead to longer effects. Our aim was to compare the use of local anaesthetic versus placebo in order to assess if indeed there is a late beneficial effect.

METHODS

We conducted an RCT involving 400 consecutive general surgery patients randomized in 2 groups: Group A = placebo, Group B = wound infiltration with 15 ml of ropivacaine 10%. We recorded the preoperative and postoperative pain for the 1st week as well as the type and quantity of the analgesia used during the study period.

RESULTS

No significant difference was found between the groups in all known confounding factors recorded. No significant difference was found in the intensity of postoperative pain. More people of group A required NSAIDs during the first 3 PO days while more people of Group B required stronger painkillers. For those patients who underwent a non urgent operation and especially laparoscopic surgery higher pain score was recorded in the group B from the 3rd PO day onwards.

DISCUSSION

Intraoperative local infiltration of the wound with local anaesthetic offers no further benefit for the general surgery apart from that of the immediate PO period. There is no late effect for pain control. Considering that during the immediate postoperative period stronger systematic painkillers are given the intraoperative, infiltration of the wound with the local anaesthetic under study offers no obvious benefit.

Butorphanol and ketamine combined in infusion solutions for patient-controlled analgesia administration: a long-term stability study

BACKGROUND

Ketamine in subanesthetic dose added to butorphanol has been reported to give superior pain control when used for intravenous patient-controlled analgesia (PCA) after surgery. However, this admixture is not available commercially and stability data applicable to hospital practice are limited.

MATERIAL/METHODS

The butorphanol-ketamine admixtures were prepared in polyolefin bags and stored in the dark at 4°C, 25°C, or 37°C for 15 days. The initial concentrations were 50-150 microgram/ml for butorphanol and 1-4 mg/ml for ketamine, respectively. The stabilities were determined by visual inspection, pH measurement, and high-pressure liquid chromatography (HPLC) assay of drug concentrations.

RESULTS

Over the 15 days, all solutions were clear in appearance, and no color change or precipitation was observed among the three temperatures. The percentages of initial concentration of each drug were over 95% during the study period, and the pH value did not change significantly.

CONCLUSIONS

The results indicate that the drug mixtures of butorphanol and ketamine in 0.9% sodium chloride injection were stable for 15 days when stored in polyolefin bags at 4°C, 25°C, or 37°C.

Response to low-dose intrathecal clonidine in septuagenarians undergoing sub-umbilical surgeries: A study

Clonidine, an alpha-2-adrenergic agonist, may have a clinically relevant analgesic action but also a hypotensive action, when administered spinally.

Development of a Management Algorithm for Post-operative Pain (MAPP) after total knee and total hip replacement: study rationale and design

BACKGROUND

Evidence from clinical practice and the extant literature suggests that post-operative pain assessment and treatment is often suboptimal. Poor pain management is likely to persist until pain management practices become consistent with guidelines developed from the best available scientific evidence. This work will address the priority in healthcare of improving the quality of pain management by standardising evidence-based care processes through the incorporation of an algorithm derived from best evidence into clinical practice. In this paper, the methodology for the creation and implementation of such an algorithm that will focus, in the first instance, on patients who have undergone total hip or knee replacement is described.

METHODS

In partnership with clinicians, and based on best available evidence, the aim of the Management Algorithm for Post-operative Pain (MAPP) project is to develop, implement, and evaluate an algorithm designed to support pain management decision-making for patients after orthopaedic surgery. The algorithm will provide guidance for the prescription and administration of multimodal analgesics in the post-operative period, and the treatment of breakthrough pain. The MAPP project is a multisite study with one coordinating hospital and two supporting (rollout) hospitals. The design of this project is a pre-implementation-post-implementation evaluation and will be conducted over three phases. The Promoting Action on Research Implementation in Health Services (PARiHS) framework will be used to guide implementation. Outcome measurements will be taken 10 weeks post-implementation of the MAPP. The primary outcomes are: proportion of patients prescribed multimodal analgesics in accordance with the MAPP; and proportion of patients with moderate to severe pain intensity at rest. These data will be compared to the pre-implementation analgesic prescribing practices and pain outcome measures. A secondary outcome, the efficacy of the MAPP, will be measured by comparing pain intensity scores of patients where the MAPP guidelines were or were not followed.

DISCUSSION

The outcomes of this study have relevance for nursing and medical professionals as well as informing health service evaluation. In establishing a framework for the sustainable implementation and evaluation of a standardised approach to post-operative pain management, the findings have implications for clinicians and patients within multiple surgical contexts.

Postoperative analgesic effects of ultrasound-guided transversus abdominis plane block for open appendectomy

PURPOSE

Transversus abdominis plane (TAP) block is a newly developed and effective peripheral block involving the nerves of the anterior abdominal wall for lower abdominal surgery. We evaluated the postoperative analgesic efficacy of ultrasound-guided TAP block using 20 mL of 0.5% levobupivacaine in patients undergoing open appendectomy.

METHODS

Forty-four patients undergoing appendectomy were assigned either to undergo a right sided-TAP block (group I, n = 22), or to receive standard care (group II, n = 22). All patients received standard anesthetics, and the TAP block group received ultrasound-guided right side TAP block using 20 mL of 0.5% levobupivacaine after induction of anesthesia. All patients received acetaminophen, and nonsteroidal anti-inflammatory drug as required during the 48 postoperative hours. Each patients was assessed for time to first rescue analgesia, verbal numerical rating pain scores (VNRS), number of rescue analgesic demands, nausea, vomiting, pruritus, and drowsiness by a blinded investigator at 0, 1, 3, 6, 12, 24 and 48 hours postoperatively.

RESULTS

The TAP block group with levobupivacaine compared to the control group reduced VNRS significantly up to 12 hours postoperatively. There were no significant differences in time to first analgesia, number of rescue analgesics demands, nausea, vomiting, pruritus and drowsiness between the groups. There were no complications attributable to the TAP block.

CONCLUSION

Ultrasound-guided TAP block using 20 mL of 0.5% levobupivacaine provided effective postoperative analgesia during the 12 postoperative hours after an open appendectomy.

Analgesics as reinforcers with chronic pain: Evidence from operant studies

Previously preclinical pain research has focused on simple behavioral endpoints to assess the efficacy of analgesics in acute and chronic pain models, primarily reflexive withdrawal from an applied mechanical or thermal stimulus. However recent research has been aimed at investigating other behavioral states in the presence of pain, including spontaneous, non-elicited pain. One approach is to investigate the reinforcing effects of analgesics in animals with experimental pain, which should serve as reinforcers by virtue of their ability to alleviate the relevant subjective states induced by pain. The gold standard for assessing drug reinforcement is generally accepted to be drug self-administration, and this review highlights the ability of drugs to serve as reinforcers in animals with experimental neuropathic pain, and the extent to which this behavior is altered in chronic pain states. Additionally, intracranial self-stimulation is an operant procedure that has been used extensively to study drug reinforcement mechanisms and the manner in which neuropathic pain alters the ability of drugs to serve as reinforcers in this paradigm will also be discussed. Drug self-administration and intracranial self-stimulation have promise as tools to investigate behavioral effects of analgesics in animals with chronic pain, particularly regarding the mechanisms through which these drugs motivate consumption in a chronic pain state.

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.

Perioperative interventions to reduce chronic postsurgical pain

Approximately 10% of patients following a variety of surgeries develop chronic postsurgical pain. Reducing chronic postoperative pain is especially important to reconstructive surgeons because common operations such as breast and limb reconstruction have even higher risk for developing chronic postsurgical pain. Animal studies of posttraumatic nerve injury pain demonstrate that there is a critical time frame before and immediately after nerve injury in which specific interventions can reduce the incidence and intensity of chronic neuropathic pain behaviors-so called "preventative analgesia." In animal models, perineural local anesthetic, systemic intravenous local anesthetic, perineural clonidine, systemic gabapentin, systemic tricyclic antidepressants, and minocycline have each been shown to reduce pain behaviors days to weeks after treatment. The translation of this work to humans also suggests that brief perioperative interventions may protect patients from developing new chronic postsurgical pain. Recent clinical trial data show that there is an opportunity during the perioperative period to dramatically reduce the incidence and severity of chronic postsurgical pain. The surgeon, working with the anesthesiologist, has the ability to modify both early and chronic postoperative pain by implementing an evidence-based preventative analgesia plan.

Efficacy and Safety of an Intra-operative Intra-articular Magnesium/Ropivacaine Injection for Pain Control following Total Knee Arthroplasty

Eighty patients with osteoarthritis who underwent unilateral total knee arthroplasty were randomly assigned to two groups: the trial group received an intraoperative intra-articular injection of magnesium sulphate and ropivacaine, and the control group received an injection of normal saline. All patients received patient-controlled analgesia with morphine for 48 h post-operatively. It was found that an intra-articular injection of magnesium sulphate and ropivacaine significantly reduced morphine consumption during the 0 - 24 h post-operative period and total 48-h postoperative morphine consumption. Pain scores at rest and during motion in the trial group were significantly lower than in the controls during the first 24 h post-operatively. The time to be able to perform a straight leg raise and to reach a 90° knee flexion was significantly shorter in the trial group compared with the controls. This study demonstrated that an intra-operative intra-articular magnesium sulphate and ropivacaine injection reduced the use of post-operative morphine.

Incorporating the treatment of medical and psychiatric disorders in the critical care area

Critical care areas are fast moving, often chaotic, and therefore confusing, even frightening, to patients attempting to understand what has happened to them. The nurse acts to mitigate these reactions by understanding the range of possibilities that can occur with patients, including potential psychiatric issues, and serving as patient advocate to ensure that appropriate treatment is initiated. Certainly there may be other psychiatric problems not described in the preceding text. The main possibilities are covered in this article. Assessing and acting early are tools the critical care nurse uses to meet patient needs and prevent behavioral problems that can interfere with life-preserving care.

Temperature-dependent enhancement of the antinociceptive effects of opioids in combination with gabapentin in mice

Prescription opioids and anticonvulsants such as gabapentin are often used as combination therapeutics for chronic as well as acute post-operative pain conditions although the effectiveness of such combinations may be dependent on the intensity of the pain state. To test the capacity of gabapentin to enhance opioid effectiveness in the presence of different thermal stimulus intensities, morphine, oxycodone and gabapentin were examined alone and in combination for antinociception in Swiss-Webster male mice using a hot-plate set to one of three temperature intensities (48.5°C, 50.5°C, 52.5°C). Morphine and oxycodone produced significant dose- and stimulus intensity-dependent antinociception whereas gabapentin produced only modest antinociception. However, in combination, gabapentin enhanced the effectiveness of sub-antinociceptive doses of morphine and oxycodone and the gabapentin and oxycodone combinations were both dose- and temperature intensity-dependent. These results provide evidence that the effectiveness and magnitude of the interactions between gabapentin and opioids are dependent on the intensity of the pain stimulus in acute thermal pain states.

Analgesic efficacy of tramadol and butorphanol in mandibular third molar surgery: a comparative study

BACKGROUND

Butorphanol tartrate, a mixed synthetic agonistantagonist opioid analgesic has been used for management of postoperative pain in minor and major surgical procedures.(14,20) Tramadol hydrochloride is a centrally acting opioid which is effectively used in postoperative pain in various minor and major surgeries.

MATERIALS AND METHODS

Twenty subjects selected randomly received butorphanol tartrate 1 mg intramuscular and 20 subjects received tramadol hydrochloride 50 mg intramuscular after the removal of mandibular third molars. Time of injection, amount of anesthetic injected, duration of surgery, adverse effects were recorded.(21)

RESULTS

The mean amount of LA administered in butorphanol group was 2.6450 ml and in tramadol group was 2.640 ml respectively, the mean duration for surgery was 56.75 and 53.5 minutes for butorphanol and tramadol groups respectively which was statistically not significant. Pain assessment was done with VAS which showed mean of 19.2 and 15.5 mm (p = 0.001) which was significant for butorphanol and tramadol respectively after 12 hours. The mean time for rescue medication requirement was 5.9 hours (for tramadol) and 8.4 hours (for butorphanol). Effective analgesic activity was seen by butorphanol 1 mg intramuscular then tramadol 50 mg.

CONCLUSION

Butorphanol 1 mg was more effective than tramadol 50 mg in respect to postoperative analgesia.

Beneficial effect of amantadine on postoperative pain reduction and consumption of morphine in patients subjected to elective spine surgery

OBJECTIVE

To analyze the effect of coadministration of morphine and amantadine on postoperative pain reduction and morphine consumption in patients after elective spine surgery.

METHODS

In double-blinded study, 60 patients (ASA physical status I-II) were randomized into two groups. Group A was given oral amantadine 50 or 100 mg 1 hour before surgery and 8, 20, 32 hours after operation. Group P received placebo at identical times. Pain was assessed using numerical rating scale before first administration of morphine and in 2, 3, 4, 6, 24, and 48 hours after operation. The amounts of morphine consumed were recorded up to 48 hours after surgery. Blood samples were taken twice in 2 hours after surgery and plasma levels of morphine and its main metabolites were measured.

RESULTS

As compared with placebo, amantadine significantly reduced intra-operative Fentanyl use and sensation of postoperative pain. Up to 48 hours after operation, the cumulative consumption of morphine was 25% lower in the amantadine group. Moreover, intensity of nausea and vomiting tended to be lower in A group. Starting from 12th hour after surgery, the level of postoperative sedation was lower in patients who received amantadine, as compared with placebo group. No significant differences in plasma levels of morphine ant its metabolites were observed between A and P groups.

CONCLUSIONS

Pre- and postoperative administration of amantadine significantly reduced fentanyl use during operation, as well as reduced the postoperative pain and decreased morphine consumption in young patients undergoing orthopedic surgery.

Study of adrenergic, imidazoline, and endothelin receptors in clonidine-, morphine-, and oxycodone-induced changes in rat body temperature

OBJECTIVES

The potentiation of morphine or oxycodone analgesia by endothelin-A (ET(A)) receptor antagonists and imidazoline/α(2)-adrenergic agonists is well documented. However, the effect of morphine or oxycodone in combination with an ET(A) receptor antagonist or an imidazoline/α(2) adrenergic agonist on body temperature is not known. The present study was carried out to study the role of ET(A) and imidazoline/α(2) adrenergic receptors in body temperature effects of morphine, oxycodone, and clonidine in rats.

METHODS

Body temperature was determined in male Sprague-Dawley rats treated with morphine, oxycodone, or clonidine. Yohimbine, idazoxan, and BMS182874 were used to determine the involvement of α(2)-adrenergic, imidazoline, and ET(A) receptors, respectively.

KEY FINDINGS

Morphine and oxycodone produced hyperthermia which was not affected by α(2)-adrenergic antagonist yohimbine, imidazoline/α(2)-adrenergic antagonist idazoxan, or ET(A) receptor antagonist BMS182874. Clonidine alone produced hypothermia that was comparable to the hypothermia observed with clonidine plus morphine or oxycodone. The hypothermic effect of clonidine was blocked by idazoxan and yohimbine. The blockade by idazoxan was more pronounced compared to yohimbine. Clonidine hypothermia was not affected by BMS182874.

CONCLUSIONS

This is the first report demonstrating that ET(A) receptors do not influence morphine- and oxycodone- induced hyperthermia or clonidine-induced hypothermia. Imidazoline receptors and α(2)-adrenergic receptors are involved in clonidine-induced hypothermia, but not in morphine- and oxycodone-induced hyperthermia.

Preoperative and postoperative anesthetic and analgesic techniques for minimally invasive surgery of the spine

STUDY DESIGN

A review of methods to optimize anesthesia and analgesia for minimally invasive spine procedures.

OBJECTIVE

To provide information to surgeons and anesthesiologists of methods to provide optimal anesthesia and pain control for minimally invasive spine surgery with an emphasis on preoperative planning.

SUMMARY OF BACKGROUND DATA

Postoperative pain management in patients undergoing minimally invasive spine surgery is a challenge for the perioperative anesthesiologist. In addition to the incisional pain, trauma to deeper tissues, such as ligaments, muscles, intervertebral discs, and periosteum are reasons for significant pain. The increasing number of minimally invasive surgeries and the need for improved and rapid return of the patient of functionality have brought the perioperative anesthesiologist and the surgeon closer.

METHODS

We undertook a review of the literature currently available on anesthesia and analgesia for minimally invasive spine surgery with an emphasis on preoperative planning. A large number of reports of randomized controlled clinical trials with respect to perioperative anesthetic and postoperative pain management for minimally invasive spine surgery are reviewed and the applicability of some of the principles and protocols used for other types of minimally invasive surgical procedures are placed in the context of spine surgery.

RESULTS

It is important to understand and implement a multimodal analgesic therapy during a patient's preoperative visits. Perioperative multimodal analgesia with a fast-track anesthetic protocol is also important and provided in the manuscript. This protocol poses a challenge to the anesthesiologist with respect to neurophysiologic monitoring, which requires further study. The postoperative analgesic management should be a continuance of the multimodal analgesia provided before surgery. Some drugs are not appropriate for patients undergoing fusion surgery because of their effect on bone healing.

CONCLUSION

An optimal preoperative, perioperative, and postoperative anesthesia and analgesia protocol is important to best possible pain relief and rapid return to normal function. Communication between the anesthesiologist and spine surgeon is important to achieve a protocol with the best short- and long-term outcomes for the benefit of the patient.

Determination of α(2)-adrenoceptor and imidazoline receptor involvement in augmentation of morphine and oxycodone analgesia by agmatine and BMS182874

Studies have demonstrated that clonidine (α(2)-adrenoceptor and imidazoline receptor agonist) and BMS182874 (endothelin ET(A) receptor antagonist) potentiate morphine and oxycodone analgesia. Agmatine, an endogenous clonidine-like substance, enhances morphine analgesia. However, its effect on oxycodone analgesia and its interaction with endothelin ET(A) receptor antagonists are not known. The present study was performed to determine the effect of agmatine on morphine and oxycodone analgesia and the involvement of α(2)-adrenoceptors, imidazoline receptors, opioid receptors, and endothelin receptors. Antinociception at various time intervals was determined by the tail-flick latency method in mice. Agmatine produced dose-dependent increase in tail-flick latency, while BMS182874 did not produce any change over the 360-min observation period. Agmatine significantly potentiated morphine as well as oxycodone analgesia which was not altered by BMS182874. BMS182874 pretreatment did not increase the analgesic effect produced by agmatine alone. Agmatine-induced potentiation of morphine and oxycodone analgesia was blocked by idazoxan (imidazoline receptor/α(2)-adrenoceptor antagonist) and yohimbine (α(2)-adrenoceptor antagonist). BMS182874-induced potentiation of morphine or oxycodone analgesia was not affected by yohimbine. However, idazoxan blocked BMS182874-induced potentiation of oxycodone but not morphine analgesia. This is the first report demonstrating that agmatine potentiates not only morphine but also oxycodone analgesia in mice. Potentiation of morphine and oxycodone analgesia by agmatine appears to involve α(2)-adrenoceptors, imidazoline receptors, and opioid receptors. In addition, imidazoline receptors may be involved in BMS182874-induced potentiation of oxycodone but not morphine analgesia. It is concluded that agmatine may be used as an adjuvant in opiate analgesia.

Antinociceptive and anti-inflammatory effects of choline in a mouse model of postoperative pain

BACKGROUND

Choline is a dietary supplement that activates alpha7 nicotinic receptors. alpha7 nicotinic activation reduces cytokine production by macrophages and has antinociceptive activity in inflammatory pain models. We hypothesized that systemic administration of choline would reduce the inflammatory response from macrophages and have antinociceptive efficacy in a murine model of postoperative pain.

METHODS

We studied the response of wild-type and alpha7 nicotinic knockout mice to heat and punctate pressure after a model surgical procedure. We investigated the effect of genotype and choline treatment on alpha-bungarotoxin binding to, and their production of tumour necrosis factor (TNF) from, macrophages.

RESULTS

Choline provided moderate antinociception. The ED(50) for choline inhibition of heat-induced allodynia was 1.7 mg kg(-1) h(-1). The ED(50) for punctate pressure threshold was 4.7 mg kg(-1) h(-1) choline. alpha7 nicotinic knockout mice had no change in hypersensitivity to heat or pressure and were significantly different from littermate controls when treated with choline 5 mg kg(-1) h(-1) (P<0.05, 0.01). Choline 100 mM reduced binding of alpha-bungarotoxin to macrophages by 72% and decreased their release of TNF by up to 51 (sd 11)%. There was no difference by genotype in the inhibition of TNF release by choline.

CONCLUSIONS

Systemic choline is a moderately effective analgesic via activation of alpha7 nicotinic acetylcholine receptors. The antinocicepive effect may not be mediated by a reduction of TNF pathway cytokine release from macrophages. Although choline at millimolar concentrations clearly inhibits the release of TNF, this effect is not alpha7 subunit-dependent and occurs at concentrations likely higher than reached systemically in vivo.