Gabapentin and pregabalin for chronic neuropathic and early postsurgical pain: current evidence and future directions

Gabapentin is ineffective as an analgesic adjunct in the immediate postburn period

Successful treatment of burn pain requires a multimodality approach. Although opioid agents are the mainstay, other nonopioid agents, such as anticonvulsants, are frequently employed for pain control, with unknown benefits. The authors sought to determine the efficacy of gabapentin in acute burn pain management. Patients admitted to the burn center with burns more than 5% total body surface area and expected length of stay more than 48 hours were randomized and prospectively enrolled in this double-blind, placebo-controlled study from February 2010 to September 2011. Drug escalation and titration were done by protocol. Pain was assessed by unit protocol with the Numeric Rating Scale. Neuropathic pain and anxiety were recorded at least biweekly. Psychosocial adjustment was assessed at follow-up. Opioid medications were converted to morphine equivalents. Differences between pain levels and opioid consumption were analyzed between groups with the Student's t-test and χ test, respectively. The study was designed to detect a difference of 22% in opioid use between the two study groups with an enrollment of 50 patients with α of 0.05 and β of 80%. P < .5 was considered significant. Fifty-three patients consented for the study and received the loading dose. Four patients withdrew. Both an intention-to-treat and actual treatment analysis were performed on all 53 patients. The placebo and drug populations were well matched for demographic variables, body surface area burned, and need for surgical intervention. The average length of stay was 11 ± 6.8 days and did not vary between groups. The study drug group received 10.8 ± 0.67 days of study drug, with eight patients receiving a dosage of 300 mg thrice daily (TID), 24 receiving 600 mg TID, 14 receiving 800 mg TID, and seven receiving 1200 mg TID. The incidence of neuropathic pain was 39% in the study drug arm and 38% in the placebo group. Neither pain scores (rest and procedural) nor opioid consumption differed between the groups. Forty-three patients (81.1%) were assessed at their first clinic visit. There was no difference in psychosocial functioning in either treatment group. In this randomized, double-blind, placebo-controlled study, the use of gabapentin in acute burn pain management did not decrease pain scores or lessen opioid requirements. Further research into nonopioid alternatives for burn pain analgesia is needed.

Arnold's nerve cough reflex: evidence for chronic cough as a sensory vagal neuropathy

Arnold's nerve ear-cough reflex is recognised to occur uncommonly in patients with chronic cough. In these patients, mechanical stimulation of the external auditory meatus can activate the auricular branch of the vagus nerve (Arnold's nerve) and evoke reflex cough. This is an example of hypersensitivity of vagal afferent nerves, and there is now an increasing recognition that many cases of refractory or idiopathic cough may be due to a sensory neuropathy of the vagus nerve. We present two cases where the cause of refractory chronic cough was due to sensory neuropathy associated with ear-cough reflex hypersensitivity. In both cases, the cough as well as the Arnold's nerve reflex hypersensitivity were successfully treated with gabapentin, a treatment that has previously been shown to be effective in the treatment of cough due to sensory laryngeal neuropathy (SLN).

Adenylyl cyclase subtype 1 is essential for late-phase long term potentiation and spatial propagation of synaptic responses in the anterior cingulate cortex of adult mice

Long-term potentiation (LTP) is a key cellular mechanism for pathological pain in the central nervous system. LTP contains at least two different phases: early-phase LTP (E-LTP) and late-phase LTP (L-LTP). Among several major cortical areas, the anterior cingulate cortex (ACC) is a critical brain region for pain perception and its related emotional changes. Periphery tissue or nerve injuries cause LTP of excitatory synaptic transmission in the ACC. Our previous studies have demonstrated that genetic deletion of calcium-stimulated adenylyl cyclase 1 (AC1) or pharmacological application of a selective AC1 inhibitor NB001 blocked E-LTP in the ACC. However, the effect of AC1 on L-LTP, which requires new protein synthesis and is important for the process of chronic pain, has not been investigated. Here we tested the effects of NB001 on the ACC L-LTP and found that bath application of NB001 (0.1 μM) totally blocked the induction of L-LTP and recruitment of cortical circuitry without affecting basal excitatory transmission. In contrast, gabapentin, a widely used analgesic drug for neuropathic pain, did not block the induction of L-LTP and circuitry recruitment even at a high concentration (100 μM). Gabapentin non-selectively decreased basal synaptic transmission. Our results provide strong evidence that the selective AC1 inhibitor NB001 can be used to inhibit pain-related cortical L-LTP without affecting basal synaptic transmission. It also provides basic mechanisms for possible side effects of gabapentin in the central nervous system and its ineffectiveness in some patients with neuropathic pain.

Anesthetic premedication: new horizons of an old practice

The practice of anesthetic premedication embarked upon soon after ether and chloroform were introduced as general anesthetics in the middle of the 19(th) century. By applying opioids and anticholinergics before surgery, the surgical patients could achieve a less anxious state, and more importantly, they would acquire a smoother course during the tedious and dangerous induction stage. Premedication with opioids and anticholinergics was not a routine practice in the 20(th) century when intravenous anesthetics were primarily used as induction agents that significantly shorten the induction time. The current practice of anesthetic premedication has evolved into a generalized scheme that incorporates several aspects of patient care: decreasing preoperative anxiety, dampening intraoperative noxious stimulus and its associated neuroendocrinological changes, and minimizing postoperative adverse effects of anesthesia and surgery. Rational use of premedication in modern anesthesia practice should be justified by individual needs, the types of surgery, and the anesthetic agents and techniques used. In this article, we will provide our readers with updated information about premedication of surgical patients with a focus on the recent application of second generation serotonin type 3 antagonist, antidepressants, and anticonvulsants.

The effect of a combination of gabapentin and donepezil in an experimental pain model in healthy volunteers: Results of a randomized controlled trial

This double-blind, placebo-controlled, 3-period cross-over, 4-treatment option, incomplete block study (ClinicalTrials.gov number NCT01485185), with an adaptive design for sample size re-estimation, was designed to evaluate gabapentin plus donepezil in an established experimental model of electrical hyperalgesia. Thirty healthy male subjects aged 18-55 years were randomized to receive gabapentin 900 mg or gabapentin 900 mg+donepezil 5mg for 2 of the 3 treatment periods, with 50% of subjects randomized to receive placebo (negative control) and 50% to gabapentin 1800 mg (positive control) for the remaining period. Each treatment period was 14 days. Gabapentin or corresponding placebo was administered on Day 13 and the morning of Day 14. Donepezil or corresponding placebo was administered nocturnally from Day 1-13 and the morning of Day 14. Co-primary endpoints were the area of pinprick hyperalgesia (260 mN von Frey filament) and allodynia (stroking by cotton bud) evoked by electrical hyperalgesia on Day 14. Gabapentin 1800 mg (n=14) significantly reduced the area of allodynia vs placebo (n=14; -12.83 cm(2); 95% confidence interval [CI] -23.14 to -2.53; P=0.015) with supportive results for hyperalgesia (-14.04 cm(2); 95% CI -28.49-0.41; P=0.057), validating the electrical hyperalgesia model. Gabapentin+donepezil (n=30) significantly reduced the area of hyperalgesia vs gabapentin 900 mg (n=30; -11.73 cm(2); 95% CI -21.04 to -2.42; P=0.014), with supportive results for allodynia (-6.62 cm(2); 95% CI -13.29-0.04; P=0.052). The adverse event profile for gabapentin+donepezil was similar to the same dose of gabapentin. Data are supportive of further clinical investigation of a gabapentin-and-donepezil combination in patients with an inadequate response to gabapentin.

Use of non-opioid analgesics as adjuvants to opioid analgesia for cancer pain management in an inpatient palliative unit: does this improve pain control and reduce opioid requirements?

BACKGROUND

Cancer pain is complex, and despite the introduction of the WHO cancer pain ladder, few studies have looked at the prevalence of adjuvant medication use in an inpatient palliative medicine unit. In this study, we evaluate the use of adjuvant pain medications in patients admitted to an inpatient palliative care unit and whether their use affects pain scores or opiate dosing.

METHODS

In this retrospective observational study, patients admitted to the inpatient palliative care unit over a 3-month period with a diagnosis of cancer on opioid therapy were selected. Data pertaining to demographics, diagnosis, oral morphine dose equivalent of the opioid at the time of discharge, adjuvant analgesics, nonsteroidal anti-inflammatory drugs (NSAIDs), and pain scores as reported by nurses and physicians were collected.

RESULTS

Seventy-seven patients were eligible over a 3-month period, out of which 65 (84 %) were taking an adjuvant medication. The most commonly prescribed adjuvant was gabapentin (70 %). Fifty-seven percent were taking more than one adjuvant. There were more women in the group receiving adjuvants (57 vs. 17%, p = 0.010). Those without adjuvants compared with those on adjuvants did not have worse pain scores on discharge as reported by physicians (0.8 ± 0.8 vs. 1.0 ± 0.7, p = 0.58) or nurses (2.0 ± 2.7 vs. 2.1 ± 2.6, p = 0.86). There was no difference in morphine equivalent doses of the opioid in both groups (median (min, max); 112 (58, 504) vs. 200 (30, 5,040)) at the time of discharge; 75-80 % of patients had improvement in pain scores as measured by a two-point reduction in numerical rating scale (NRS).

DISCUSSION

This study shows that adjuvant medications are commonly used for treating pain in patients with cancer. More than half of study population were on two adjuvants or an adjuvant plus NSAID along with an opioid. We did not demonstrate any benefit in terms of improved pain scores or opioid doses with adjuvants, but this could reflect confounding variables and physician choice. Larger prospective studies are needed to define the opioid-sparing effects of adjuvants.

CONCLUSION

Adjuvant agents are used in over 80 % of those treated for cancer pain.

Australian and New Zealand evidence-based recommendations for pain management by pharmacotherapy in adult patients with inflammatory arthritis

AIM

To develop Australian and New Zealand evidence-based recommendations for pain management by pharmacotherapy in adult patients with optimally treated inflammatory arthritis (IA).

METHODS

Four hundred and fifty-three rheumatologists from 17 countries including 46 rheumatologists from Australia and New Zealand participated in the 2010 3e (Evidence, Expertise, Exchange) Initiative. Using a formal voting process, rheumatologists from 15 national scientific committees selected 10 clinical questions regarding the use of pain medications in IA. Bibliographic fellows undertook a systematic literature review for each question, using MEDLINE, EMBASE, Cochrane CENTRAL and 2008-09 EULAR/ACR abstracts. Relevant studies were retrieved for data extraction and risk of bias assessment. Rheumatologists from Australia and New Zealand used the evidence to develop a set of national recommendations. These recommendations were then formulated and assessed for agreement and the potential impact on clinical practice. The Oxford Levels of Evidence and Grade of Recommendation were applied to each recommendation.

RESULTS

The systematic reviews identified 49 242 references, from which 167 studies which met the pre-specified inclusion criteria. Combining this evidence with expert opinion led to the development of 10 final Australian and New Zealand recommendations. The recommendations relate to pain measurement, and the use of analgesic medications in patients with and without co-morbidities and during pregnancy and lactation. The recommendations reflect the clinical practice of the majority of the participating rheumatologists (mean level of agreement 7.24-9.65).

CONCLUSIONS

Ten Australian and New Zealand evidence-based recommendations regarding the management of pain by pharmacotherapy in adults with optimally treated IA were developed. They are supported by a large panel of rheumatologists, thus enhancing their utility in everyday clinical practice.

Perioperative Pregabalin for Acute Pain After Gynecological Surgery: A Meta-analysis

BACKGROUND

Pregabalin has been used as an adjuvant in some trials to control postoperative pain after gynecologic surgery. However, the potential clinical advantage remains debatable.

OBJECTIVE

We performed a meta-analysis of clinical trials of pregabalin to evaluate its ability to control acute postoperative pain after gynecologic surgery.

METHODS

We searched PubMed, ScienceDiret, and the Cochrane Library of Randomized Controlled Trials up to January 2014. We performed a systematic review and meta-analysis of prospective controlled studies reporting pregabalin for gynecologic surgery. The primary outcome was pain outcomes and postoperative cumulative opioid consumption. Data were reported as weighted mean differences (WMDs) and 95% CIs. The secondary outcome was adverse effects after surgery.

RESULTS

Six valid randomized trials met the eligibility criteria and were included in the meta-analysis. Pooled data were collected from 452 patients between 2007 and 2012 (These trials were separately conducted in Greece 2012, India 2011-2012, Turkey 2011, Denmark 2009 and Australia 2007). The pregabalin-treated patients consumed fewer opioids during the first 24 hours postoperatively (WMD, -8.50 mg; 95% CI, -11.29 to -5.71 mg; P < 0.00001). Pain intensity at rest and on movement or coughing revealed a statistically significant pain relief effect of pregabalin during 24 hours postoperatively (at rest: WMD, -6.20 mm; 95% CI, -11.83 to -0.58 mm; P = 0.03; on movement or coughing: WMD, -5.32 mm; 95% CI, -9.73 to -0.91 mm; P = 0.02). No differences were found between the pregabalin and control groups for the adverse effects.

CONCLUSIONS

Pregabalin has an analgesic and opioid-sparing effect and does not increase the frequency of adverse effects in acute postoperative pain management after gynecologic surgery.

The efficacy of preemptive analgesia with pregabalin in septoplasty

Objectives

Pregabalin is used to treat neuropathic pain and has shown analgesic properties in postoperative pain. The aim of this study was to investigate the effectiveness and safety of pregabalin in reducing postoperative pain in patients after septoplasty.

Methods

Forty-seven patients scheduled for elective septoplasty were randomly assigned to groups that received either pregabalin (150 mg) or placebo, both one hour before surgery and 12 hours after the initial dose. Pain (verbal numerical rating scale, VNRS) and side effect assessments were performed at 6, 12, 12 to 24, and 24 to 48 hours postoperatively.

Results

From 1 to 12 hours postoperatively, VNRS scores for pain were lower in the pregabalin group (n=24) than in the placebo group (n=23; P<0.05). The number of patients who needed rescue analgesics was lower in the pregabalin group (P=0.042). The incidence of nausea and vomiting did not differ between groups (P=0.666), and the incidence of sedation was higher in the placebo groups (P=0.022).

Conclusion

The perioperative administration of oral pregabalin (150 mg twice) is an effective and safe way to reduce early postoperative pain in patients undergoing septoplasty.

Effects of 2 different doses of pregabalin on morphine consumption and pain after abdominal hysterectomy: a randomized, double-blind clinical trial

BACKGROUND

Pregabalin has a similar pharmacologic profile to that of its developmental predecessor gabapentin but has shown greater analgesic activity in rodent models of neuropathic pain.

OBJECTIVE

The objective of the study was to compare the effects of 2 different doses of pregabalin and placebo on postoperative pain and morphine consumption.

METHODS

Ninety patients who underwent abdominal hysterectomy were included in the study and randomly divided into 3 groups in a doubled-blinded manner. They were given 150 mg of pregabalin (group P300, n = 30), 300 mg of pregabalin (group P600, n = 30), or placebo capsules (group C, n = 30) 4 hours before the induction of anesthesia; they received a second dose of the drug 12 hours postoperatively. Morphine consumption, nausea, and vomiting, visual analogue scale-pain intensity (VAS-PI), sedation scores, and dissatisfaction scores were recorded in the postanesthesia care unit (PACU) and at 2, 4, 6, and 24 hours after operation.

RESULTS

Morphine consumption at 24 hours was 40.80 (3.42) mg, 33.79 (5.77) mg, and 46.97 (6.67) mg in groups P300, P600, and C, respectively (P < 0.001). VAS-PI scores at movement and at rest in the PACU and at 2, 4, and 6 hours decreased in group P600 (P < 0.01). In the PACU and at 2, 4, and 6 hours, the sedation scores were increased in group P600 compared with the scores in group C (P < 0.001, P < 0.001, P = 0.01, P = 0.006, respectively). Patient satisfaction was higher in group P600 than in group C for all time points (P < 0.001, P < 0.001, P < 0.001, P = 0.001, P < 0.001, respectively). There were no statistically significant differences between the groups for side effects such as nausea, vomiting, and dizziness (P = 0.58).

CONCLUSIONS

Pregabalin at a total dose of 600 mg, administered before operation and at 12 hours postoperatively after abdominal hysterectomy, reduced morphine consumption and pain intensity and increased patient satisfaction. No significant differences in side effects were observed between the study groups.

Orally active opioid μ/δ dual agonist MGM-16, a derivative of the indole alkaloid mitragynine, exhibits potent antiallodynic effect on neuropathic pain in mice

(E)-Methyl 2-((2S,3S,7aS,12bS)-3-ethyl-7a-hydroxy-8-methoxy-1,2,3,4,6,7,7a,12b-octahydroindolo[2,3-a]quinolizin-2-yl)-3-methoxyacrylate (7-hydroxymitragynine), a main active constituent of the traditional herbal medicine Mitragyna speciosa, is an indole alkaloid that is structurally different from morphine. 7-Hydroxymitragynine induces a potent antinociceptive effect on mouse acute pain through μ-opioid receptors. In this study, we developed dual-acting μ- and δ-opioid agonists MGM-15 and MGM-16 from 7-hydroxymitragynine for the treatment of acute and chronic pain. MGM-16 showed a higher potency than that of 7-hydroxymitragynine and MGM-15 in in vitro and in vivo assays. MGM-16 exhibited a high affinity for μ- and δ-opioid receptors, with K(i) values of 2.1 and 7.0 nM, respectively. MGM-16 showed μ- and δ-opioid full agonistic effects in a guanosine 5'-O-(3-[(35)S]thiotriphosphate) binding assay and in a functional test using electrically elicited guinea pig ileum and mouse vas deferens contractions. Systemic administration of MGM-16 produced antinociceptive effects in a mouse acute pain model and antiallodynic effects in a chronic pain model. The antinociceptive effect of MGM-16 was approximately 240 times more potent than that of morphine in a mouse tail-flick test, and its antiallodynic effect was approximately 100 times more potent than that of gabapentin in partial sciatic nerve-ligated mice, especially with oral administration. The antinociceptive effect of MGM-16 was completely and partially blocked by the μ-selective antagonist β-funaltrexamine hydrochloride (β-FNA) and by the δ-selective antagonist naltrindole, respectively, in a tail-flick test. The antiallodynic effect of MGM-16 was completely blocked by β-FNA and naltrindole in a neuropathic pain model. These findings suggest that MGM-16 could become a class of a compound with potential therapeutic utility for treating neuropathic pain.

Management of cancer pain: 1. Wider implications of orthodox analgesics

In this review, the first of two parts, we first provide an overview of the orthodox analgesics used commonly against cancer pain. Then, we examine in more detail the emerging evidence for the potential impact of analgesic use on cancer risk and disease progression. Increasing findings suggest that long-term use of nonsteroidal anti-inflammatory drugs, particularly aspirin, may reduce cancer occurrence. However, acetaminophen may raise the risk of some hematological malignancies. Drugs acting upon receptors of gamma-aminobutyric acid (GABA) and GABA “mimetics” (eg, gabapentin) appear generally safe for cancer patients, but there is some evidence of potential carcinogenicity. Some barbiturates appear to slightly raise cancer risks and can affect cancer cell behavior in vitro. For cannabis, studies suggest an increased risk of squamous cell carcinoma of the tongue, larynx, and possibly lung. Morphine may stimulate human microvascular endothelial cell proliferation and angiogenesis; it is not clear whether this might cause harm or produce benefit. The opioid, fentanyl, may promote growth in some tumor cell lines. Opium itself is an emerging risk factor for gastric adenocarcinoma and possibly cancers of the esophagus, bladder, larynx, and lung. It is concluded that analgesics currently prescribed for cancer pain can significantly affect the cancer process itself. More futuristically, several ion channels are being targeted with novel analgesics, but many of these are also involved in primary and/or secondary tumorigenesis. Further studies are needed to elucidate possible cellular and molecular effects of orthodox analgesics and their possible long-term impact, both positive and negative, and thus enable the best possible clinical gain for cancer patients.

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.

Chloride extrusion enhancers as novel therapeutics for neurological diseases

The K(+)-Cl(-) cotransporter KCC2 is responsible for maintaining low Cl(-) concentration in neurons of the central nervous system (CNS), which is essential for postsynaptic inhibition through GABA(A) and glycine receptors. Although no CNS disorders have been associated with KCC2 mutations, loss of activity of this transporter has emerged as a key mechanism underlying several neurological and psychiatric disorders, including epilepsy, motor spasticity, stress, anxiety, schizophrenia, morphine-induced hyperalgesia and chronic pain. Recent reports indicate that enhancing KCC2 activity may be the favored therapeutic strategy to restore inhibition and normal function in pathological conditions involving impaired Cl(-) transport. We designed an assay for high-throughput screening that led to the identification of KCC2 activators that reduce intracellular chloride concentration ([Cl(-)]i). Optimization of a first-in-class arylmethylidine family of compounds resulted in a KCC2-selective analog (CLP257) that lowers [Cl(-)]i. CLP257 restored impaired Cl(-) transport in neurons with diminished KCC2 activity. The compound rescued KCC2 plasma membrane expression, renormalized stimulus-evoked responses in spinal nociceptive pathways sensitized after nerve injury and alleviated hypersensitivity in a rat model of neuropathic pain. Oral efficacy for analgesia equivalent to that of pregabalin but without motor impairment was achievable with a CLP257 prodrug. These results validate KCC2 as a druggable target for CNS diseases.

Optimizing the Pharmacologic Treatment of Insomnia: Current Status and Future Horizons

A number of medications are available for treating patients with insomnia. These medications include agents approved as insomnia therapies by the U.S. Food and Drug Administration (FDA), agents approved by the FDA for another condition that are used "off-label" to treat insomnia, and agents available "over-the-counter" that are taken by individuals with insomnia. These agents differ in their properties, their safety and efficacy when used for different insomnia patient subtypes, and the available data on their efficacy and safety in these subtypes. As a result, optimizing the medication treatment of insomnia for a given patient requires that the clinician select an agent for use which has characteristics that make it most likely to effectively and safely address the type of sleep difficulty experienced by that individual. This article is intended to assist clinicians and researchers in carrying out this optimization. It begins by reviewing the basic characteristics of the medications used to treat insomnia. This is followed by a review of the fundamental ways that individuals with insomnia may differ and affect the choice of medication therapy. This review includes discussions that illustrate how to best choose a medication based on the characteristics of the available medications, the key differences among insomnia patients, and the available research literature. Lastly, we discuss future directions for the optimizing pharmacologic management of insomnia. It is hoped that the treatment tailoring methods discussed herein serve as a means of improving the clinical management of insomnia and, thus, improve the lives of the many patients who suffer from this common and impairing condition.

Electrical stimulation as an adjunctive treatment of painful and sensory diabetic neuropathy

BACKGROUND

The objective of this review is to evaluate the use of electrical stimulation to treat diabetic neuropathy. Application of electrical stimulation may provide a novel treatment option for large and small fiber neuropathy in persons with diabetes. Large and small nerve neuropathy alters pain, proprioception, touch perception, and motor function, which cause burning foot pain and serve as protective mechanisms from ulcerations.

METHODS

A content search for clinical trials involving electrical stimulation, neuropathy, and diabetes was conducted through PubMed. Randomized clinical trials and prospective studies with outcome measures affecting the lower extremity function were selected for review.

RESULTS

We identified eight studies in which electrical stimulation was used to treat diabetic neuropathy. Six studies evaluated small fiber neuropathy. Two studies evaluated patients with both small and large fiber neuropathy and reported significant improvement in vibration and monofilament testing and reduction in symptoms in the electrical stimulation treatment group. Six of the eight painful neuropathy studies identified significant improvement in symptoms. There were no studies that evaluated electrical stimulation to treated diabetic motor neuropathy, fall prevention or postural instability.

CONCLUSIONS

Electrical stimulation may be an effective alternative and adjunctive therapy to current interventions for diabetic peripheral neuropathy.

Pregabalin suppresses nociceptive behavior and central sensitization in a rat trigeminal neuropathic pain model

The aim of this study was to determine whether pregabalin affects nociceptive behavior and central sensitization in a trigeminal neuropathic pain model. A partial infraorbital nerve transection (p-IONX) or sham operation was performed in adult male rats. Nociceptive withdrawal thresholds were tested with von Frey filaments applied to the bilateral vibrissal pads pre- and postoperatively. On postoperative day 7, the behavioral assessment was conducted before and at 30, 60, 120, and 180 minutes after and 24 hours after pregabalin (.1, 1, 10, 100 mg/kg intraperitoneally) or saline injection. The effects of pregabalin or saline were also examined on the mechanoreceptive field and response properties of nociceptive neurons recorded in the medullary dorsal horn at postoperative days 7 to 10. Reduced withdrawal thresholds reflecting bilateral mechanical allodynia were observed in p-IONX rats until postoperative day 28, but not in sham-operated rats. At postoperative day 7, pregabalin significantly and dose-dependently reversed the reduced mechanical withdrawal thresholds in p-IONX rats. Pregabalin also attenuated central sensitization of the neurons, as reflected in reversal of their reduced activation threshold, increased responses to pinch/pressure, and enhanced stimulus-response function. This study provides the first documentation that pregabalin attenuates the mechanical allodynia and central sensitization that characterize this trigeminal neuropathic pain model, and supports its clinical use for treating craniofacial neuropathic pain.

PERSPECTIVE

Trigeminal nerve injury in rats produced facial mechanical hypersensitivity and trigeminal central sensitization of medullary dorsal horn neurons that were markedly attenuated by systemically administered pregabalin, suggesting its potential clinical utility for orofacial neuropathic pain.

Long-term use of gabapentin for musculoskeletal disease and trauma in three cats

Gabapentin has been widely used in human medicine to control acute and chronic pain. Although the exact mechanism of action has yet to be determined, its use in veterinary medicine is increasing. The clinical use of gabapentin for analgesia in cats has been reported in review articles and one case report. Managing chronic pain, particularly in the feline patient, poses a challenge to veterinary surgeons. This report details the long-term use of gabapentin for musculoskeletal pain or head trauma in three cats. All cats received gabapentin for several months at an average dose of 6.5 mg/kg q12h. Clinical signs suggestive of pain, such as aggression, avoiding human interaction and loss of appetite, were observed to decrease with the administration of gabapentin, used as part of an analgesia regime or as sole medication. Long-term follow-up with the owners of all cats indicated that satisfactory pain management was achieved, administration was easy and no obvious side effects during the period of administration occurred. We conclude that long-term treatment with gabapentin is of potential benefit in controlling pain in cases of head trauma, as well as musculoskeletal disease. It may provide a valuable adjunct for the management of chronic pain in cats and should be investigated further for its clinical use and safety.

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.

The prophylactic effects of gabapentin on postoperative sore throat after thyroid surgery

Background

Postoperative sore throat (POST) is considered a usual complication after tracheal intubation, especially, thyroid surgery. Gabapentin is a widely studied multimodal perioperative drug, which can be used to treat acute postoperative pain. The primary endpoints of this study was a reduction of the incidence of POST at rest and during the swallowing movements after thyroid surgery. And the second endpoints was a reduction of the intensity of the POST after thyroid surgery.

Methods

Seventy-one patients that underwent elective thyroid surgery received either gabapentin (Neurontin™ 600 mg) or placebo, orally, one hour before anesthesia. The VAS scores and incidences of POST and adverse effects were determined at 1 hr, 6 hr, 12 hr, and 24 hr after surgery at rest and during swallowing movement.

Results

The gabapentin group (N = 36) showed a lower incidence of POST than the placebo group (N = 35) (47% vs. 78%, P = 0.038), and had significant lower VAS score at 6 and 24 hours after surgery in the resting state. However, during the movement, no intergroup differences were found in terms of the incidence of POST (83% vs. 91%, P = 0.305) or VAS score. Furthermore, no significant difference was observed between the two groups, in adverse effects.

Conclusions

Gabapentin (Neurontin™ 600 mg) administered 1 hr before anesthesia reduced the intensity and incidence of POST during the resting state without a significant adverse event, during the 24 hr after thyroid surgery. However, gabapentin did not reduce the intensity and incidence of POST during the swallowing movement.

Characterization of a new animal model for evaluation and treatment of back pain due to lumbar facet joint osteoarthritis

OBJECTIVE

Osteoarthritic (OA) degeneration of the lumbar facet joints has been implicated in low back pain. This study was undertaken to investigate the biologic links between cellular and structural alterations within facet joint components and the development of symptomatic chronic back pain.

METHODS

We generated an animal model of facet joint degeneration by intraarticular injection of monosodium iodoacetate (MIA) into facet joints (L3-L4, L4-L5, L5-L6) of Sprague-Dawley rats. Pain sensation due to pressure, which mimics a mechanical stimulus for facet joint injury, was measured using an algometer. Pain response was also assessed in a straight leg raising test. Cartilage alterations were assessed by biochemical evaluation and microfocal computed tomography (micro-CT). Therapeutic modulation of chronic facet joint pain with the use of various pharmacologic agents was investigated.

RESULTS

MIA injection resulted in severely damaged facet joint cartilage, proteoglycan loss, and alterations of subchondral bone structure. Micro-CT analyses suggested that the behavioral hyperalgesia from facet joint degeneration was not associated with foraminal stenosis. The biologic and structural changes in facet joints were closely associated with sustained and robust chronic pain. Morphine and pregabalin markedly alleviated pressure hyperalgesia, while celecoxib (a selective inhibitor of cyclooxygenase 2 [COX-2]) produced moderate antihyperalgesic effects and the effect of ketorolac (an inhibitor of COX-1 and COX-2) was negligible.

CONCLUSION

Our findings demonstrate that MIA injection provides a useful model for the study of OA changes in the facet joint and indicate that facet joint degeneration is a major cause of chronic low back pain. The treatment results suggest that classes of drugs that are widely used to treat OA, such as nonsteroidal antiinflammatory drugs, may have limited efficacy once joint destruction is complete.

Post-thoracotomy pain syndrome: assessment and intervention

Surgery is a cornerstone of treatment in early-stage non-small cell lung cancer. Chronic postoperative thoracotomy pain, post-thoracotomy pain syndrome (PTPS), is a condition occurring in 50% of postsurgical patients with lung cancer and is largely unrecognized. This article examines the diagnosis and treatment of PTPS to assist oncology nurses in providing better care to this patient population. Post-thoracotomy pain in patients with lung cancer may be under-reported and undertreated. Causes from the thoracotomy can be trauma and compression to the intercoastal nerves, fractured and compressed ribs, inflammation of the chest muscles, atrophy of chest muscles, or scar tissue rubbing. This article examines the diagnosis and treatment of PTPS to assist oncology nurses in providing better care to this patient population. If left untreated, chronic pain can have a deleterious effect on patients' recovery and overall well-being. Oncology nurses should be aware of the signs and symptoms of PTPS so that more patients are diagnosed and choose to seek treatment.

Cost analysis of adding pregabalin or gabapentin to the management of community-treated patients with peripheral neuropathic pain

OBJECTIVE

To compare the cost of adding either pregabalin or gabapentin to the management of community-treated patients with peripheral neuropathic pain (PNP).

METHODS

A retrospective observational study was conducted using medical records from a Spanish health care provider claims database. Patients receiving health care for PNP, above 18 years and for which either pregabalin or gabapentin was initiated between 2006 and 2008 were included. Economic evaluation included health care resource utilization costs and costs due to sick leave.

RESULTS

A total of 1163 patients with PNP were eligible for analysis: 764 were prescribed pregabalin and 399 gabapentin in addition to current pain therapy. Mean age was 59.2 years and 62.2% were female. Concomitant use of analgesics was higher in the gabapentin cohort (3.2 vs. 2.7; P = 0.003), mainly due to non-steroidal anti-inflammatory drugs (74.9% vs. 69.5%; P = 0.018) and opioids (27.7% vs. 17.9%; P = 0.031). Adjusted total costs per patient was lower in pregabalin-treated patients (€2514 vs. €3241; P = 0.003), due to less sick leave (€1067 vs. €1633; P = 0.018) and lower health care costs (€1447 vs. €1609; P = 0.004). The higher acquisition cost of pregabalin (€351 vs. €191; P < 0.001) was largely compensated with lower costs in medical visits, physiotherapy, hospital stays and concomitant analgesics.

CONCLUSIONS

In community-treated patients with PNP, total costs were considerably less for those patients initiated with pregabalin therapy than for those patients starting gabapentin add-on therapy. The relatively higher treatment acquisition cost of pregabalin was largely compensated by the overall lower costs for the other components of health care resources and sick leave, thus reducing the economic impact on the health care provider's budget and society.

An economic evaluation of pregabalin versus usual care in the management of community-treated patients with refractory painful diabetic peripheral neuropathy in primary care settings

OBJECTIVE

To estimate the cost-effectiveness of pregabalin versus usual care (UC) in the management of community-treated patients with refractory painful diabetic peripheral neuropathy (pDPN) in primary care settings (PCS) in Spain.

METHODS

Data was extracted from a 12-week registry study assessing costs of neuropathic pain in Spain. Pregabalin-naïve outpatients treated with UC or newly prescribed pregabalin were selected for inclusion in the cost-effectiveness analysis. Effectiveness was expressed as quality-adjusted life years (QALY) gain. Perspectives of the Spanish National Health System (NHS) and society (2006) were applied for cost calculations. Results were expressed as incremental cost-effectiveness ratio (ICER). Bootstrapping techniques (10,000 re-samples) were used to obtain the probabilistic ICER and the cost-effectiveness acceptability curve.

RESULTS

A total of 189 patients were included in the economic analysis. Compared with UC, pregabalin was associated with higher QALY gain in a period of 12-weeks; 0.0406±0.0343 versus 0.0285±0.0350 (p=0.167). Overall total costs (€1368±1229 vs. €1258±1474; p=0.587) and healthcare costs (€628±590 vs. €469±420; p=0.134) were similar for both pregabalin and UC, respectively. ICERs for pregabalin varied from €5302 (95% CI: dominant; €144,105) for total costs to €14,381 (dominant; €115,648) for healthcare costs. Probabilistic sensitivity analyses showed that 79-84% of ICERs were below the threshold of €30,000/QALY.

CONCLUSION

This study suggests that pregabalin may be cost-effective in the management of community-treated refractory outpatients, with pDPN when compared with usual care in the primary care setting in Spain. These findings may help policy makers when making health decision in the management of diabetes in the community.

Effects of Preoperative Gabapentin on Postoperative Pain after Radical Retropubic Prostatectomy

Objective:

The impact of preoperative gabapentin on tramadol consumption using patient-controlled analgesia (PCA) and postoperative pain was assessed in patients undergoing radical retropubic prostatectomy (RRP).

Methods:

In this prospective, randomized trial, 51 patients undergoing RRP were randomized into two groups: the gabapentin group received 900 mg gabapentin orally 2 h before surgery; the control group did not receive gabapentin. Postoperative analgesia was provided by tramadol PCA. Pain was assessed using a visual analogue scale for 24 h, postoperatively.

Results:

Mean cumulative tramadol consumption at 24 h was comparable in the two groups. Pain scores at 45 min, 60 min and 2 h postoperatively, and the number of patients who required rescue analgesia, were significantly lower in the gabapentin group than in the control group. Side-effects were similar in the two groups.

Conclusions:

Preoperative administration of 900 mg gabapentin did not decrease tramadol consumption, but was associated with lower pain scores in the early postoperative phase and a reduced need for rescue analgesia, compared with controls, in patients undergoing RRP.

Randomized, double-blind, placebo-controlled, phase II trial of gabapentin enacarbil for migraine prophylaxis

Objective

The objective of this article is to evaluate the efficacy and safety of gabapentin enacarbil (GEn) for migraine prophylaxis.

Methods

In this randomized, double-blind, parallel-group study, patients with International Headache Society-defined migraine who met criteria suggesting the need for prophylactic therapy were randomized 2:1:2:2:1 to one of the following five groups, designated according to target daily dose of study medication during the 20-week treatment period: placebo, GEn 1200 mg, GEn 1800 mg, GEn 2400 mg, or GEn 3000 mg.

Results

The intent-to-treat population included 523 patients ( n = 128 placebo, n = 66 GEn 1200 mg, n = 134 GEn 1800 mg, n = 133 GEn 2400 mg, n = 62 GEn 3000 mg). No statistically significant difference between active treatment (the average of 1800 mg and 2400 mg treatment groups) and placebo was found for change from baseline in the number of migraine headache days during the last four weeks of treatment prior to taper (the primary endpoint). Results of analyses of the primary endpoint using the per protocol population, analyses using imputation methods different from those of the primary analysis, and nonparametric analyses were consistent with the primary analysis in showing no difference between active treatment and placebo. The pattern of results was similar for the secondary efficacy endpoints. Pharmacokinetic data demonstrate that patients had adequate estimated exposure to GEn. The adverse event profile of GEn was consistent with that in previous studies.

Conclusion

GEn did not significantly differ from placebo for migraine headache prophylaxis. A high placebo effect should be considered when interpreting these results.

A cost-effectiveness analysis of the effect of pregabalin versus usual care in the treatment of refractory neuropathic pain in routine medical practice in Spain

OBJECTIVE

The objective of this study was to estimate the cost-effectiveness of pregabalin vs usual care (UC) in outpatients with refractory neuropathic pain (NeP), treated according to routine medical practice in primary care settings in Spain.

METHODS

Patients were extracted from a 12-week noninterventional prospective study conducted to ascertain the costs of NeP. Pairs of pregabalin-naïve patients receiving UC or pregabalin, matched by age, gender, pain intensity, and refractory to previous treatment, were selected in a 1:1 ratio. Refractory was considered a patient with actual pain (scoring >40 in a 100 mm in a pain visual analog scale) after receiving a course of a standard analgesic, at its recommended doses. Perspectives of the Spanish National Healthcare System and society were included in the analysis. Effectiveness was expressed as quality-adjusted life-year (QALY) gain. Results of the cost-effectiveness analysis were expressed as an incremental cost per QALY (ICER) gained. Probabilistic sensitivity analysis using bootstrapping techniques was also carried out.

RESULTS

A total of 160 pairs were extracted. Compared with UC, pregabalin was associated with significantly higher QALY gain; 0.0374 ± 0.0367 vs 0.0224 ± 0.0313 (P < 0.001). Despite drug acquisition costs being higher for pregabalin (€251 ± 125 vs €104 ± 121; P < 0.001), total and health care costs incurred for pregabalin were similar in both groups; €1,335 ± 1,302 vs €1,387 ± 1,489 (P = 0.587) and €529 ± 438 vs €560 ± 672 (P = 0.628), respectively, yielding a dominant ICER for both total and health care costs in the base case scenario; 95% confidence intervals, respectively, dominant to €17,268, and dominant to €6,508. Sensitivity analysis confirmed results of the basecase scenario.

CONCLUSION

This study showed that pregabalin may be cost-effective in the treatment of refractory NeP patients when compared with UC in routine medical practice in Spain.

Effects of single-dose pregabalin on postoperative pain in dacryocystorhinostomy surgery

Background

Postoperative pain of dacryocystorhinostomy (DCA) surgery is one of the serious issues to be considered. Administrating opioids to relieve postoperative pain and facing their increasing side effects in eye surgeries, make the use of non-opioid drugs inevitable.

Objectives

The present study examined the efficacy of pregabalin in alleviating the postoperative pain of DCA surgery.

Patients and Methods

The present study has been carried out as a double-blind, randomized clinical trial on the patient candidates for DCR. The patients were randomly divided in to two groups of pregabalin and placebo. Patients in pregabalin group received 300 mg of pregabalin, an hour before the operation in the morning of the surgery. Pain intensity on visual analog scale (VAS) was recorded until 24 hours after the operation; also the rate of administrated opioids and nausea/vomiting frequency were recorded during the first 24-hour period after the operation and the resultsof the two groups were compared.

Results

Postoperative pain intensity in the pregabalin group at the time of recovery was significantly lower than that of the placebo group (P = 0.001) until 24 hours after the surgery. In the pregabalin group 17.5% of the patients received opioids while in the placebo group the figure was 52.5% (P = 0.001). Nausea frequency was also higher in the placebo group than the pregabalin group (P = 0.003).

Conclusions

A single 300 mg dose of pregabalin, an hour before DCA can effectively reduce pain intensity and also reduce opioid dose and nausea/vomiting.

Does Pregabalin (Lyrica(®) ) help patients reduce their use of benzodiazepines? A comparison with gabapentin using the Norwegian Prescription Database

Pregabalin (Lyrica(®) ) may have an anxiolytic effect. It has also been reported that the use of this drug helps prevent excessive use of benzodiazepines. The aim of the present study was to examine if pregabalin reduced the intake of benzodiazepines. In a pharmacoepidemiological study, we compared pregabalin to the older drug gabapentin (Neurontin(®) ) in the Norwegian Prescription Database. The database has total capture of all prescribed drugs outside institutions. We identified all prescriptions for the two drugs for patients aged 18-69 years between 2004 and 2007. Patients were grouped as psychiatric patients, patients with epilepsy, patients with neuropathic pain or non-specified users. We measured the use of benzodiazepines 182 days before and after the initiation of treatment with pregabalin and gabapentin. Between 15% and 29% of the patients were able to stop using benzodiazepines after starting pregabalin or gabapentin treatment. Psychiatric patients who started pregabalin were able to reduce the amount of benzodiazepines used by 48%, compared to only 14% among starters of gabapentin. This study shows that some patients reduced their use of benzodiazepines substantially after starting pregabalin.

Elucidating the mechanism of action of pregabalin: α(2)δ as a therapeutic target in anxiety

This review provides a brief summary of what is known about the anxiolytic mechanism of action of pregabalin, a highly selective, high-affinity ligand of the P/Q type of voltage-gated calcium channel (CaV). Evidence from in vivo models of neuronal hyperexcitability suggests that pregabalin reduces synaptic release of neurotransmitters in selected CNS regions including the cortex, olfactory bulb, hypothalamus, amygdala, hippocampus, cerebellum and dorsal horn of the spinal cord. Release of neurotransmitters from the synaptic vesicle, and propagation of neurotransmission, requires the vesicle to fuse with the presynaptic membrane. Pregabalin binding to the α(2)δ type 1 protein of the P/Q type CaV reduces the availability of Ca2+ required for membrane fusion and exocytosis of neurotransmitters. Evidence that the anxiolytic mechanism of action of pregabalin is mediated by binding to the α(2)δ type 1 protein comes from animal models, which have demonstrated a structure-activity relationship between the affinity of ligands for the α(2)δ type 1 protein and their potency in models of anxiety such as the Vogel conflict test. Furthermore, the anxiolytic activity of pregabalin is lost in transgenic mice with specific point mutations in the CaV α(2)δ type 1 protein. Pregabalin-mediated reduction in calcium currents has also been shown to result in a significant inhibition of the release of neurotransmitters implicated in pathological anxiety such as glutamate and monoamine neurotransmitters. However, further research is needed to confirm that these effects contribute to the anxiolytic mechanism of action of pregabalin. Finally, pregabalin may also act by inhibiting synaptogenesis of excitatory neurons formed in response to chronic stress or anxiety, or more acutely inhibit the trafficking of CaV to the plasma membrane.

Effect of oral pregabalin premedication on post-operative pain in laparoscopic gastric bypass surgery

Background

Post-operative pain and the administration of opioids to relieve it, is considered to be one of the important issues in surgery wards. This issue is even more significant in obese patients, because of the side effects of opioids. Pregabalin is an analog of gamma aminobutyric acid (GABA) which can be effective in dealing with post-operative pain.

Objectives

This study will consider the effect of oral pregabalin in relieving the pain of obese patients after gastric bypass surgery.

Patients and Methods

In a double blind clinical trial, 60 candidates for laparoscopic gastric bypass surgery were enrolled in the study through convenience and non-random sequential sampling, into two groups; pregabalin group and control group. Inclusion criteria consisted of: morbid obesity with a body mass index (BMI) > 35, age 18–50, American Society of Anesthesiologists (ASA) status I or II, and willingness to take part in the study. Patients in the pregabalin group received 300 mg of oral pregabalin on the morning of the surgery. Post-operative pain was controlled by the patient-controlled intravenous analgesia (PCIA) method, an AutoMed infusion pump containing 20 mg of morphine and normal saline (total volume 100 cc) was administered to all patients after surgery. Patients’ level of pain were compared by considering their pain intensity on a visual analog scale (VAS), and the occurrence of nausea/vomiting from recovery, until 24 hours after surgery.

Results

A total of 60 patients were compared; 30 patients in each of the pregabalin and control groups. Both groups were similar in age and sex distribution. Mean pain intensity levels during the whole follow up were lower in the pregabalin group than in the control group, up to a maximum of 24 hours after the operation (P < 0.001). Incidence of nausea/vomiting was greater in the control group than in the pregabalin group (P < 0.001).

Conclusions

The findings of this study indicate that oral pregabalin (300 mg dose) can alleviate patients’ pain and nausea/vomiting and notably reduce adverse effects.

Complete atrioventricular block due to overdose of pregabalin

Pregabalin, a synthetic derivate of the inhibitory neurotransmitter γ-aminobutyric acid, shows antiepileptic, analgesic, anticonvulsant, anxiolytic, and sleep-modulating activities. The major advantage of pregabalin is its relative reliability, easy use, high tolerance, and lack of negative interaction with other drugs. A 65-year-old woman with medical histories of diabetes mellitus, lumbar spondylosis, diabetic nephropathy, chronic renal failure, and anemia of chronic disease was admitted with the complaint of dizziness and syncope. She had been taking pregabalin 300 mg daily for 8 months. Electrocardiogram revealed complete atrioventricular (AV) block and right bundle-brunch block with a heart rate of 39 per minute. Her creatinine was 1.8 mg/dL, and creatinine clearance was 50 mL/min. Pregabalin treatment was discontinued. Four days later, the complete AV block resolved spontaneously to Mobitz type II block and to sinus rhythm with right bundle-brunch block on the seventh day. To our knowledge, this is the first case of complete AV block associated with pregabalin. We believe that AV block occurred as a result of pregabalin's effect on L-type Ca++ channels in the heart. Pregabalin's different effects on electrocardiogram and on the heart in different individuals may have an association with the patterns of distribution of the L-type calcium channels in myocardium.

Pain management in dermatologic procedures: before and after

BACKGROUND

Periprocedural analgesic therapy is an often overlooked, but critical component of ensuring adequate surgical patient care and overall satisfaction with surgical outcomes. Adequate pain management requires thorough assessment of pain and complete knowledge and understanding of the various therapeutic agents available.

OBJECTIVES

To further the knowledge and understanding of current strategies in pain management.

METHODS

A literature review was conducted through PubMed to define current pain assessment and management strategies.

RESULTS AND CONCLUSIONS

Appropriate pain assessment leads to the selection of optimal pharmacologic options for pain control in the acute postoperative setting.

Battlefield analgesia: a brief review of current trends and concepts in the treatment of pain in US military casualties from the conflicts in Iraq and Afghanistan

SUMMARY Battlefield analgesia and post-injury pain management is a high priority within the military medical community. The combined military services of the USA have developed a Pain Task Force and clinical practice guidelines to ensure that adequate analgesia is provided to our wounded soldiers as far forward as the point of injury on the battlefield. As a result of this emphasis, novel analgesic techniques and equipment have led to improved pain management. Continuous peripheral nerve blocks, intranasal ketamine, battlefield acupuncture and other adjuncts have all been utilized safely and successfully. The ability to provide rapid analgesia as early in the course of injury as possible not only helps with the immediate pain of the soldier, but potentially minimizes the risk of developing chronic postinjury pain. During the long medical evacuation system the risks of both undertreatment and overtreatment of pain are very real. Future studies and observation will help to delineate best treatment regimens and pave the way for the next generation of medical providers to positively impact a soldier’s recovery. This article is written from the perspective of the USA with a focus on the conflicts in Afghanistan (Operation Enduring Freedom) and Iraq (Operation Iraqi Freedom).

Prevention of chronic pain after surgical nerve injury: amputation and thoracotomy

Although techniques for acute pain management have improved in recent years, a dramatic reduction in the incidence and severity of chronic pain following surgery has not occurred. Amputation and thoracotomy, although technically different, share the commonalities of unavoidable nerve injury and the frequent presence of persistent postsurgical neuropathic pain. The authors review the risk factors for the development of chronic pain following these surgeries and the current evidence that supports analgesic interventions. The inconclusive results from many preemptive analgesic studies may require us to reconceptualize the perioperative treatment period as a time of gradual neurologic remodeling.

Mechanisms of neuropathic pain

Neuropathic pain is a disease of global burden. Its symptoms include spontaneous and stimulus-evoked painful sensations. Several maladaptive mechanisms underlying these symptoms have been elucidated in recent years: peripheral sensitization of nociception, abnormal excitability of afferent neurons, central sensitization comprising pronociceptive facilitation, disinhibition of nociception and central reorganization processes, and sympathetically maintained pain. This review aims to illustrate these pathophysiological principles, focussing on molecular and neurophysiological findings. Finally therapeutic options based on these findings are discussed.

Pain in the ICU: a psychiatric perspective

Pain is abundant in the intensive care unit (ICU). Successful analgesia demands a comprehensive appreciation for the etiologies of pain, vigilant clinical assessment, and personalized treatments. For the critically ill, frequent threats to mental and bodily integrity magnify the experience of pain, challenging clinicians to respond swiftly and thoughtfully. Because pain is difficult to predict and physiologic correlates are not specific, self-report remains the gold standard assessment. When communication is limited by intubation or cognitive deficits, behavioral pain scales prove useful. Patient-tailored analgesia aspires to mitigate suffering while optimizing alertness and cognitive capacity. Mindfulness of the neuropsychiatric features of pain helps the ICU clinician to clarify limits of traditional analgesia and identify alternative approaches to care. Armed with empirical data and clinical practice recommendations to better conceptualize, identify, and treat pain and its neuropsychiatric comorbidities, the authors (psychiatric consultants, by trade) reinforce holistic approaches to pain management in the ICU. After all, without attempts to understand and relieve suffering on all fronts, pain will remain undertreated.