Effect of preemptive nerve block on inflammation and hyperalgesia after human thermal injury

Effect of Bilateral Superficial Cervical Plexus Block on Postoperative Analgesic Consumption in Patients Undergoing Thyroid Surgery

Purpose

Patients complain of moderate-intensity pain following thyroid surgery. Superficial cervical plexus block (SCPB) can be employed as a component of multimodal analgesia after thyroid surgery. This double-blind, randomized study aimed to compare the effects of bilateral SCPB (BSCPB) on postoperative analgesic requirements following thyroid surgery.

Methods

A total of 60 American Society of Anesthesiologists (ASA) I-II patients who underwent elective total thyroidectomy under general anesthesia were randomly assigned to Group 1 and Group 2. After inducing general anesthesia, BSCPB was not administered to Group 1, whereas BSCPB was administered using a three-point injection technique with 0.5% levobupivacaine in Group 2. Patient-controlled analgesia (PCA) was applied by using tramadol in both groups for postoperative analgesia. Tenoxicam was administered as rescue analgesic to patients in case of numeric rating scale (NRS) >4. The postoperative consumption of tramadol, rescue analgesic requirement, and hoarseness, hematoma, signs of local anesthetic toxicity were recorded.

Results

The consumption of tramadol for PCA at two, six, 12, and 24 hours postoperatively, NRS scores in the recovery room, and the number of patients who used tenoxicam as rescue analgesic were significantly lower in Group 2 than in Group 1. The hemodynamic values were similar between the groups.

Conclusions

Our study demonstrates that BSCPB, when applied as a component of multimodal analgesia, is an effective method for reducing the analgesic requirements following thyroid surgery.

Regional anesthesia for ambulatory pediatric penoscrotal procedures

BACKGROUND/PURPOSE

Pediatric urology procedures are amongst the most commonly performed in children. The need for proactive treatment of pain is essential for optimal patient care. Current guidelines recommend the routine use of regional anesthesia in children as appropriate unless contraindicated. Given the commonality of urologic procedures in children, it is essential to understand the indications for and the utility of regional anesthesia.

METHODS

The current literature was searched using PubMed as the primary platform. Search words included 'dorsal penile nerve block,' 'pudendal nerve block,' 'ring block,' 'spinal anesthesia,' and 'caudal,' along with 'pediatric', 'circumcision,' 'hypospadias,' 'urology', and 'urological surgery' as part of the keywords of the search.

RESULTS

The articles resulting from the literature search were reviewed for content, clarity and study design by two co-authors, and agreement determined the incorporation into the review. Additionally, a detailed description of study design, regional anesthetic technique, local anesthetic(s) used, and outcomes of each study referenced was incorporated into the supplemental table.

CONCLUSION

Given the variance in block technique and local anesthetic choice amongst the current reported studies in the literature, it is difficult to truly compare and infer superiority of the regional anesthetic choices for ambulatory penoscrotal procedures. When choosing a regional anesthetic technique, careful consideration must be placed on block coverage, severity of expected pain and surgical duration of the procedure, type and dose of local anesthetic, as well as the patient's past medical history and anatomy. Moreover, the regional block chosen should result from a thorough preoperative discussion between the surgeon and the anesthesiologist.

Methodology and applicability of the human contact burn injury model: A systematic review

The contact burn injury model is an experimental contact thermode-based physiological pain model primarily applied in research of drug efficacy in humans. The employment of the contact burn injury model across studies has been inconsistent regarding essential methodological variables, challenging the validity of the model. This systematic review analyzes methodologies, outcomes, and research applications of the contact burn injury model. Based on these results, we propose an improved contact burn injury testing paradigm. A literature search was conducted (15-JUL-2020) using PubMed, EMBASE, Web of Science, and Google Scholar. Sixty-four studies were included. The contact burn injury model induced consistent levels of primary and secondary hyperalgesia. However, the analyses revealed variations in the methodology of the contact burn injury heating paradigm and the post-burn application of test stimuli. The contact burn injury model had limited testing sensitivity in demonstrating analgesic efficacy. There was a weak correlation between experimental and clinical pain intensity variables. The data analysis was limited by the methodological heterogenicity of the different studies and a high risk of bias across the studies. In conclusion, although the contact burn injury model provides robust hyperalgesia, it has limited efficacy in testing analgesic drug response. Recommendations for future use of the model are being provided, but further research is needed to improve the sensitivity of the contact burn injury method. The protocol for this review has been published in PROSPERO (ID: CRD42019133734).

American Burn Association Guidelines on the Management of Acute Pain in the Adult Burn Patient: A Review of the Literature, a Compilation of Expert Opinion, and Next Steps

The ABA pain guidelines were developed 14 years ago and have not been revised despite evolution in the practice of burn care. A sub-committee of the American Burn Association's Committee on the Organization and Delivery of Burn Care was created to revise the adult pain guidelines. A MEDLINE search of English-language publications from 1968 to 2018 was conducted using the keywords "burn pain," "treatment," and "assessment." Selected references were also used from the greater pain literature. Studies were graded by two members of the committee using Oxford Centre for Evidence-based Medicine-Levels of Evidence. We then met as a group to determine expert consensus on a variety of topics related to treating pain in burn patients. Finally, we assessed gaps in the current knowledge and determined research questions that would aid in providing better recommendations for optimal pain management of the burn patient. The literature search produced 189 papers, 95 were found to be relevant to the assessment and treatment of burn pain. From the greater pain literature 151 references were included, totaling 246 papers being analyzed. Following this literature review, a meeting to establish expert consensus was held and 20 guidelines established in the areas of pain assessment, opioid medications, nonopioid medications, regional anesthesia, and nonpharmacologic treatments. There is increasing research on pain management modalities, but available studies are inadequate to create a true standard of care. We call for more burn specific research into modalities for burn pain control as well as research on multimodal pain control.

Regional Anesthetic Blocks for Donor Site Pain in Burn Patients: A Meta-Analysis on Efficacy, Outcomes, and Cost

Background

Skin graft donor site pain significantly affects pain management, narcotic use, and hospital length of stay. This study is intended to evaluate the efficacy of regional anesthesia in the burn population to decrease narcotic consumption and to assess the impact on hospitalization costs.

Methods

PubMed/MEDLINE, Embase, and ScienceDirect were searched with the following inclusion criteria: comparative studies, adult populations, burn patients, autologous skin grafting, regional nerve blocks, and traditional narcotic regimens. Outcomes assessed included narcotic consumption, pain scores, and opioid side effects. Meta-analysis obtained pooled values for morphine consumption and side effects. Cost analysis was performed using published data in the literature.

Results

Final analysis included 101 patients. Cumulative morphine consumption at 72 hours was lower for patients treated with regional anesthesia versus patient-controlled analgesia (PCA; single shot 25 ± 12 mg, continuous regional 23 ± 16 mg, control 91.5 ± 24.5 mg; P < .05). Regional anesthesia decreased nausea/vomiting (P < .05) and lowered subjective pain scores. Regional anesthesia interventions cost less than PCA, single shot less than continuous (P < .05).

Conclusion

Regional anesthesia at skin graft donor sites significantly decreases narcotic consumption in burn patients. Regional anesthesia is cost-effective, decreases side effects, and may result in shorter hospital stays due to improved pain management.

Managing rebound pain after regional anesthesia

Rebound pain after regional anesthesia can be defined as transient acute postoperative pain that ensues following resolution of sensory blockade, and is clinically significant, either with regard to the intensity of pain or the impact on psychological well-being, quality of recovery, and activities of daily living. Current evidence suggests that it represents an unmasking of the expected nociceptive response in the absence of adequate systemic analgesia, rather than an exaggerated hyperalgesic phenomenon induced by local anesthetic neural blockade. In the majority of patients, it does not appear to significantly impact cumulative postoperative opioid consumption, quality of recovery, or patient satisfaction, and is not associated with longer-term sequelae such as persistent post-surgical pain. Nevertheless, it must be considered whenever regional anesthesia is incorporated into perioperative management. Strategies to mitigate the impact of rebound pain include routine prescribing of a systemic multimodal analgesic regimen, as well as patient education on appropriate expectations regarding block offset and expected surgical pain, and timely initiation of analgesic medication. Prolonging the duration of action of regional anesthesia with continuous catheter techniques or local anesthetic adjuncts may also help alleviate rebound pain, although further research is required to confirm this.

Comparison of antinociceptive effects of plain lidocaine versus lidocaine complexed with hydroxypropyl-β-cyclodextrin in animal models of acute and persistent orofacial pain

Herein, it was investigated whether a complex of lidocaine with 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) would present a better antinociceptive profile in vivo when compared with plain lidocaine in models of orofacial pain. Plain lidocaine (LDC) and complexed lidocaine (LDC:HP-β-CD) were initially evaluated in vitro to determine the release rate of the two formulations. Subsequently, the effect of both formulations was evaluated in independent groups of rats submitted to the orofacial formalin test, induction of facial heat hyperalgesia by capsaicin and carrageenan, and induction of facial heat and mechanical hyperalgesia by constriction of the infraorbital nerve. LDC:HP-β-CD led to a reduction in the lidocaine release assessed in the in vitro release assay compared to plain LDC. Both formulations presented an antinociceptive effect in all models, but LDC:HP-β-CD showed a better effect in the second phase of the formalin response, in carrageenan-induced heat hyperalgesia, and in the heat hyperalgesia associated to infraorbital nerve constriction. Our results show that complexation improved in vivo antinociceptive effects of LDC, but further studies are necessary to elucidate what properties contribute to the better effect of the complexed formulation on this models and/or what characteristics of the pain model facilitate the action of the complexed formulation.

Protective multimodal analgesia with etoricoxib and spinal anesthesia in inguinal hernia repair: a randomized controlled trial

BACKGROUND

Inguinal hernia repair is a common procedure, and can be performed under spinal anesthesia. Although adequate analgesia is crucial to postoperative recovery, the optimal protective analgesic regimen remains to be established.

PURPOSE

To investigate the effects of preoperative etoricoxib within a protective multimodal analgesic regimen with respect to pain control following open inguinal hernia repair.

METHODS

Sixty adult patients undergoing open inguinal hernia repair participated in a single-center, randomized, double-blinded, placebo-controlled trial in a general academic medical center. The intervention group (n = 30) received 120 mg of oral etoricoxib 1 h preoperatively, and 10-12 mg bupivacaine with 25 μg fentanyl as spinal anesthesia. The control group (n = 30) received oral placebo 1 h preoperatively, and spinal anesthesia as above. Postoperative Visual Analog Scale pain scores at rest and on active straight leg raise were recorded and analyzed.

RESULTS

Resting pain scores were significantly lower in the intervention than the control group at 16 h, 24 h, and on discharge (3.00 vs. 4.35; 1.57 vs. 4.00; 1.24 vs. 3.76, respectively; p < 0.05). Pain scores on active straight leg raise were significantly lower in the intervention than the control group at 16 h, 24 h, and on discharge (3.85 vs. 5.59, p < 0.01; 2.84 vs. 4.90, p < 0.05; 3.55 vs. 5.32, p < 0.05, respectively).

CONCLUSION

The addition of etoricoxib to spinal anesthesia as a multimodal protective regimen can improve pain control after inguinal hernia repair. The optimal dose and applicability to other operations remains to be established.

Demarcation of secondary hyperalgesia zones: Punctate stimulation pressure matters

BACKGROUND

Secondary hyperalgesia is increased sensitivity in normal tissue near an injury, and it is a measure of central sensitization reflecting injury-related effects on the CNS. Secondary hyperalgesia areas (SHAs), usually assessed by polyamide monofilaments, are important outcomes in studies of analgesic drug effects in humans. However, since the methods applied in demarcating the secondary hyperalgesia zone seem inconsistent across studies, we examined the effect of a standardized approach upon the measurement of SHA following a first degree burn injury (BI).

NEW METHOD

The study was a two-observer, test-retest study with the two sessions separated by 6wk. An observer-blinded design adjusted to examine day-to-day and observer-to-observer variability in SHA was used. In 23 healthy volunteers (12 females/11 males) a BI was induced by a contact thermode (47.0°C, 420s, 2.5×5.0cm(2)). The SHA, demarcated by polyamide monofilaments (bending force: 0.2, 69 and 2569mN) and a "weighted-pin" stimulator (512mN), were assessed 45 to 75min after each BI.

RESULTS

A random effect, linear mixed model demonstrated a logarithmic correlation between elicited skin pressures (mN/mm(2)) and the SHAs (P<0.0001). No day-to-day or observer-to-observer differences in SHAs were observed. Intraclass correlation coefficients, in the range of 0.51 to 0.84, indicated a moderate to almost perfect reliability between observers.

COMPARISON WITH EXISTING METHODS

No standardized approach in SHA-assessment has hitherto been presented.

CONCLUSIONS

This is the first study to demonstrate that demarcation of secondary hyperalgesia zones depends on the developed pressure of the punctate stimulator used.

Systemic ropivacaine diminishes pain sensitization processes: a randomized, double-blinded, placebo-controlled, crossover study in healthy volunteers

Introduction

Ropivacaine is a local anesthetic widely used for regional anesthesia. One of its advantages is low toxicity at plasma concentrations reached systemically during continuous peripheral or central nervous block. The objective of this study was to test the effect of systemic ropivacaine on pain, hyperalgesia, dynamic allodynia, and flare response.

Methods

This randomized, double-blinded, placebo-controlled, crossover study was carried out in at the Clinical Trials Centre, University of Zurich, Switzerland. Twenty healthy male volunteers were included in the study. Exclusion criteria were contraindications or hypersensitivity to local anesthetics, vulnerable subjects (intellectually or mental impaired), drug, alcohol or nicotine abuse, known peripheral neuropathies, diabetes mellitus and/or congestive heart disease. Ropivacaine and saline were infused intravenously during a subcutaneous electrical stimulation. The stimulation software adjusted the stimulus strength according to the rating on a numeric rating scale (NRS; 0–10) maintaining a NRS of 5. Areas of punctate hyperalgesia, dynamic allodynia, and flare response were measured before and after the infusion.

Results

The area of hyperalgesia increased significantly with saline (303 ± 380%, P < 0.05) and ropivacaine (186 ± 137%, P < 0.05). The area of allodynia (253 ± 299%, P < 0.05) and flare response (112 ± 24%, P < 0.05) increased only during the placebo infusion.

Conclusion

The results of this study imply that systemic ropivacaine may diminish pain sensitization processes.

Electronic supplementary material

The online version of this article (doi:10.1007/s40122-013-0021-z) contains supplementary material, which is available to authorized users.

Continuous femoral versus epidural block for attainment of 120° knee flexion after total knee arthroplasty: a randomized controlled trial

We conducted the prospective randomized controlled trial to test that continuous femoral nerve block (CFNB) improves attainment of 120° knee flexion compared to continuous epidural analgesia (CEA). Sixty-six patients scheduled for unilateral total knee arthroplasty were randomized into two groups; infusion of ropivacaine 0.15% into CEA or CFNB to third postoperative days. We studied the time required to attain 120° knee flexion, variations in thigh and calf circumferences around the treated knee, pain scores, rehabilitation milestones, the need for adjuvant analgesics, and side effects. CFNB patients attained earlier knee flexion to 120°, lower variations in thigh and calf circumferences, less pain during rehabilitation, and less need for adjuvant analgesics. CFNB is a better pain management strategy that accelerates knee flexion rehabilitation.

Chemical analgesia for velvet antler removal in deer

There is a legal requirement to provide analgesia for velvet antler removal in New Zealand. Currently, this is achieved using local anaesthetic blockade, with or without systemically administered sedative/analgesic agents, or by compression in 1-year-old stags. Lignocaine hydrochloride 2% is most commonly used and is most effective when administered as a high-dose ring block. Combinations of various amino-amide local anaesthetic agents can achieve rapid onset and prolonged duration of analgesia, though concerns about drug residues and carcinogenic potential of a lignocaine metabolite have led to consideration of the amino-ester family of local anaesthetics as alternatives. Systemically administered analgesics, including opioids, alpha-2-adrenergic agents and ketamine provide dose-dependent sedation and analgesia. However, none are sufficient, alone or in combination, to produce surgical analgesia at currently recommended dose rates and when reversal agents are given, analgesic effects are usually reversed as well as sedation. Thus, local anaesthetic blockade is still indicated, though the potential for drug or drug-metabolite residues in velvet antler remains a concern. The need for and effectiveness of non-steroidal anti-inflammatory drugs (NSAIDs) for post-operative analgesia requires investigation. Amitriptyline, locally administered opioid agonists, tramadol and other systemically administered agents may warrant future investigation for surgical and post-operative analgesia for velvet antler removal.

Superficial selective cervical plexus block following total thyroidectomy: a randomized trial

BACKGROUND

Pain after thyroid surgery is of moderate intensity and short duration. Bilaterally superficial cervical plexus block (BSCPB) may reduce analgesic requirements. However, its effectiveness in decreasing pain after thyroidectomy is debated.

METHODS

This double-blind, randomized placebo-controlled study in 100 patients undergoing total thyroidectomy evaluates the effects of BSCPB done with 20 mL of 0.75% ropivacaine. Additional parecoxib was administrated immediately postoperatively and 12 hours later.

RESULTS

Postoperative pain was assessed by visual analogue rating scale. All parameters were recorded at 0, 3, 6, 9, 12, and 24 hours after surgery. The control group had higher values than the ropivacaine group at all moments (p < .05) except H12 (p = .76). Additional analgesia was needed for 7 patients (14%) in the control group and for 8 patients (16%) in the group with ropivacaine (p = .96).

CONCLUSION

Two-point bilateral BSCPB has a major analgesic effect on patients after total thyroidectomy, with a statistically significant reduction in postoperative pain scores. However, no significant difference was noted in the proportion of patients that required additional analgesics.

Central sensitization: implications for the diagnosis and treatment of pain

Nociceptor inputs can trigger a prolonged but reversible increase in the excitability and synaptic efficacy of neurons in central nociceptive pathways, the phenomenon of central sensitization. Central sensitization manifests as pain hypersensitivity, particularly dynamic tactile allodynia, secondary punctate or pressure hyperalgesia, aftersensations, and enhanced temporal summation. It can be readily and rapidly elicited in human volunteers by diverse experimental noxious conditioning stimuli to skin, muscles or viscera, and in addition to producing pain hypersensitivity, results in secondary changes in brain activity that can be detected by electrophysiological or imaging techniques. Studies in clinical cohorts reveal changes in pain sensitivity that have been interpreted as revealing an important contribution of central sensitization to the pain phenotype in patients with fibromyalgia, osteoarthritis, musculoskeletal disorders with generalized pain hypersensitivity, headache, temporomandibular joint disorders, dental pain, neuropathic pain, visceral pain hypersensitivity disorders and post-surgical pain. The comorbidity of those pain hypersensitivity syndromes that present in the absence of inflammation or a neural lesion, their similar pattern of clinical presentation and response to centrally acting analgesics, may reflect a commonality of central sensitization to their pathophysiology. An important question that still needs to be determined is whether there are individuals with a higher inherited propensity for developing central sensitization than others, and if so, whether this conveys an increased risk in both developing conditions with pain hypersensitivity, and their chronification. Diagnostic criteria to establish the presence of central sensitization in patients will greatly assist the phenotyping of patients for choosing treatments that produce analgesia by normalizing hyperexcitable central neural activity. We have certainly come a long way since the first discovery of activity-dependent synaptic plasticity in the spinal cord and the revelation that it occurs and produces pain hypersensitivity in patients. Nevertheless, discovering the genetic and environmental contributors to and objective biomarkers of central sensitization will be highly beneficial, as will additional treatment options to prevent or reduce this prevalent and promiscuous form of pain plasticity.

Wound infiltration for surgery

Wound infiltration with local anaesthetics is a simple, effective and inexpensive means of providing good analgesia for a variety of surgical procedures without any major side-effects. In particular, local anaesthetic toxicity, wound infection and healing do not appear to be major considerations. The purpose of this review is to outline the existing literature on a procedure-specific basis and to encourage a more widespread acceptance of the technique, ensuring that all layers are infiltrated in a controlled and meticulous manner.

Antiinflammatory effect of peripheral nerve blocks after knee surgery: clinical and biologic evaluation

BACKGROUND

Nerve blocks provide analgesia after surgery. The authors tested whether nerve blocks have antiinflammatory effects.

METHODS

Patients had combined sciatic (single-shot) and continuous femoral block (48 h) (block group) or morphine patient-controlled analgesia after total knee arthroplasty. Pain at rest and upon movement was monitored at 1 (D1), 4 (D4), and 7 days (D7) and 1 (M1) and 3 months (M3) after surgery. Knee inflammation was evaluated (skin temperature, knee circumference) before surgery and at D1, D4, D7, M1, and M3. Plasma cytokine concentrations (interleukin [IL]-6, IL-1beta, tumor necrosis factor [TNF], IL-10, soluble receptor 1 of TNF [sTNF-R1]) were measured before surgery and at 4 h, D1, D4, and D7 after surgery. Capsule and synovial membrane cytokines were measured (IL-6, TNF, IL-1, IL-10). Knee flexion was evaluated before surgery and at D1, D4, D7, M1, and M3. Morphine use and recovery time to autonomy were monitored.

RESULTS

Pain at rest and upon movement was lower in the block group than in patient-controlled analgesia patients between D1 and D7 (analysis of variance, P < 0.005). Knee flexion was improved in the block group for D1 to M1 (analysis of variance, P < 0.0001). Block group patients recovered nonassisted mobilization (t test, P = 0.04) and toilet use (t test, P = 0.03) more rapidly. Knee circumference and skin temperature were lower in the block group between D1 and D7 (analysis of variance, P < 0.05). Synovial membrane IL-1 (P < 0.05) and IL-10 (P < 0.01) increased, and plasma IL-6 and sTNF-R1 peaked at 24 h, with no difference between groups.

CONCLUSION

Nerve blocks inhibited clinical inflammation after total knee arthroplasty, with no change in tissue and plasma cytokine concentrations.

Preemptive analgesia with local lidocaine infiltration for single-level open disc operation

To evaluate the impact of preemptive local analgesia at the incision site for postoperative pain in patients undergoing disc operation. In this prospective, randomized, double-blinded, placebo-controlled study 166 patients were assigned to either lidocaine (n = 83) or placebo (n = 83) groups. The incision site was infiltrated with either 20 mL of 2% lidocaine and 0.9% saline in lidocaine group or 0.9% saline before the incision. Morphine (5 mg) was used for postoperative pain treatment. Postoperative pain was measured with Visual Analog Scale (VAS) in 6, 12, 24 and 48 h. Data were analyzed with SPSS software, using Chi-square and t-tests. The groups were matched for age, sex, type of operation, mean length of hospital stay and mean length of operation. Statistical analysis revealed no significant difference in visual analog scores of pain severity at 6, 12, 24 and 48 h after surgery between lidocaine and placebo groups (6 h: 38.22 +/- 26.87 vs. 34.52 +/- 24.43, p = 0.35; 12 h: 33.26 +/- 28.83 vs. 28.01 +/- 24.71, p = 0.20; 24 h: 26.71 +/- 23.31 vs. 22.85 +/- 22.48, p = 0.27; 48 h 16.35 +/- 10.16 vs. 15.23 +/- 8.90 p = 0.45). The amount of narcotics used post operatively had no meaningful difference in the groups (lidocaine 10.07 +/- 8.24 mg vs. placebo 10.54 +/- 9.31 mg p = 0.73). Preemptive analgesia with lidocaine 2% used subcutaneously before skin incision has no effect in reducing postoperative pain, narcotics demand and duration of hospital stay.

[Administration of ketamine during induction and maintenance of anaesthesia in postoperative pain prevention]

INTRODUCTION

Carcinologic breast surgery is responsible of intermediary postoperative pain and needs 30% additional morphine. Now, morphine administration generates adverse effects. Publications about morphine saving effect of ketalar as antagonist of R-NMDA, administrated in perioperative increase are discussed.

OBJECTIVE

To evaluate the morphine saving effect of ketalar in carcinologic breast surgery.

PATIENTS AND METHOD

This phase III randomized and double-blind study includes 208 patients during 14 months. Surgery consisted in mastectomy with or without axillary lymph node dissection or lumpectomy with axillary lymph node dissection. Group K received ketalar at induction until the end of surgery. Group P (placebo) received physiologic serum in the same condition. During the postoperative first 48h, morphine's consumption and EN are measured.

RESULTS

No significant difference between two groups was observed. The EN evaluation and morphine consumption remained the same in the two groups. Our results did not find any benefit with use of ketamine between axillary lymph node dissection and no axillary lymph node dissection group.

CONCLUSION

Ketalar adjunction in our analgesic protocol did not induce significant morphine saving in carcinologic breast surgery.

Analgesic efficacy of bilateral superficial cervical plexus block administered before thyroid surgery under general anaesthesia

BACKGROUND

The use of regional anaesthesia in thyroid surgery remains controversial. This double-blind, randomized controlled study was conducted to evaluate the analgesic efficacy of bilateral superficial cervical plexus block (BSCPB) performed under general anaesthesia in patients undergoing total thyroidectomy.

METHODS

Eighty-seven consecutive consenting patients were randomized to receive a BSCPB with saline (Group P, n = 29), ropivacaine 0.487% (Group R, n = 29), or ropivacaine 0.487% plus clonidine 5 microg ml(-1) (Group RC, n = 29). Sufentanil was given during the intraoperative period for a 20% increase in arterial mean pressure or heart rate in a patient with a bispectral index between 40 and 60. All patients received 4 g of acetaminophen during the first 24 h after operation. The pain score was checked every 4 h and nefopam was given for pain score >4 on a numeric pain scale.

RESULTS

During surgery, the median sufentanil requirements were significantly reduced in Group RC compared with Groups R and P (0.32 vs 0.47 and 0.62 microg kg(-1); P < 0.0001). After surgery, the number of patients requiring nefopam within 24 h of surgery was significantly lower in Groups R and RC than in Group P (16 and 19 vs 25; P = 0.03). At post-anaesthetic care unit admission, median (range) pain scores were significantly lower in Groups R [3 (0-10)] and RC [3 (0-8)] than in Group P [5 (0-8), P = 0.03]. No major complications of BSCPB occurred during study.

CONCLUSIONS

BSCPB with ropivacaine and clonidine improved intraoperative analgesia. BSCPB with ropivacaine or ropivaciane and clonidine was effective in reducing analgesic requirements after thyroid surgery.

Burn injury pain: the continuing challenge

The development of more effective methods of relieving pain associated with burn injury is a major unmet medical need. Not only is acute burn injury pain a source of immense suffering, but it has been linked to debilitating chronic pain and stress-related disorders. Although pain management guidelines and protocols have been developed and implemented, unrelieved moderate-to-severe pain continues to be reported after burn injury. One reason for this is that the intensity of pain associated with wound care and rehabilitation therapy, the major source of severe pain in this patient population, varies widely over the 3 phases of burn recovery, making it difficult to estimate analgesic requirements. The effects of opioids, the most commonly administered analgesics for burn injury procedural pain, are difficult to gauge over the course of burn recovery because the need for an opioid may change rapidly, resulting in the overmedication or undermedication of burn-injured patients. Understanding the mechanisms that contribute to the intensity and variability of burn injury pain over time is crucial to its proper management. We provide an overview of the types of pain associated with a burn injury, describe how these different types of pain interfere with the phases of burn recovery, and summarize pharmacologic pain management strategies across the continuum of burn care. We conclude with a discussion and suggestions for improvement. Rational management, based on the underlying mechanisms that contribute to the intensity and variability of burn injury pain, is in its infancy. The paucity of information highlights the need for research that explores and advances the identification of mechanisms of acute and chronic burn injury pain.

PERSPECTIVE

Researchers continue to report that burn pain is undertreated. This review examines burn injury pain management across the phases of burn recovery, emphasizing 3 types of pain that require separate assessment and management. It provides insights and suggestions for future research directions to address this significant clinical problem.

Efficacy and safety of steroid use for postoperative pain relief. Update and review of the medical literature

Despite the availability of various analgesic regimens, patient surveys have indicated that moderate-to-severe postoperative pain is still poorly managed. The use of corticosteroids for postoperative pain relief, although popular, has yet to gain wider acceptance because of concerns over side effects, in particular adrenal suppression, osteonecrosis, impaired wound-healing, and concerns about efficacy. The medical literature provides evidence that should substantially decrease these concerns with regard to low and short-dose applications. The results of randomized trials have shown low, short-dose corticosteroid regimens to be safe and effective for reducing postoperative pain. There is strong, grade-A evidence supporting the use of corticosteroids in multimodal analgesia protocols to contribute to the postoperative recovery of the patient by minimizing opioid doses and therefore side effects. However, the optimal mode, dose, and timing of administration remain unclear.

Measuring the quality of continuous epidural block for abdominal surgery

BACKGROUND

In view of the wide variation in pain experience between patients, a clinical standard -- the time from the end of surgery to the first experience of pain -- was applied to 1359 consecutive patients in order to investigate whether the initial quality of epidural block has an effect on the overall quality of postoperative pain relief.

METHODS

Clinical data were recorded in 58,118 out of 72,412 h in 1359 patients, and transferred to a database. Data collected included pain scores on a four-point verbal rating scale; nausea and vomiting; motor block; sedation scores; systolic blood pressure <100 and <90 mm Hg; ventilatory frequency <10 and <8 bpm; and hourly epidural infusion rate.

RESULTS

As the time to first experience of pain increased from nil to >24 hours, the time from the first to last experience of pain shortened from 34 (19-50) h to 3 (1-12) h (p<0.001) and the proportion of patients receiving an epidural bolus decreased from 53 to 8% (p<0.001). Increases in the initial pain free time increased the proportion of patients with systolic BP<100 mmHg from 59 to 77%, (p<0.001) and increased the proportion of patients with respiratory rate <10 bpm from 13 to 26%, (p<0.001).

CONCLUSION

Extending pain relief for more than 12 h beyond the end of abdominal surgery significantly improves the overall quality of postoperative pain relief, but is associated with an increase in side-effects.

The efficacy of preemptive analgesia for acute postoperative pain management: a meta-analysis

Whether preemptive analgesic interventions are more effective than conventional regimens in managing acute postoperative pain remains controversial. We systematically searched for randomized controlled trials that specifically compared preoperative analgesic interventions with similar postoperative analgesic interventions via the same route. The retrieved reports were stratified according to five types of analgesic interventions: epidural analgesia, local anesthetic wound infiltration, systemic N-methyl-d-aspartic acid (NMDA) receptor antagonists, systemic nonsteroidal antiinflammatory drugs (NSAIDs), and systemic opioids. The primary outcome measures analyzed were the pain intensity scores, supplemental analgesic consumption, and time to first analgesic consumption. Sixty-six studies with data from 3261 patients were analyzed. Data were combined by using a fixed-effect model, and the effect size index (ES) used was the standardized mean difference. When the data from all three outcome measures were combined, the ES was most pronounced for preemptive administration of epidural analgesia (ES, 0.38; 95% confidence interval [CI], 0.28-0.47), local anesthetic wound infiltration (ES, 0.29; 95% CI, 0.17-0.40), and NSAID administration (ES, 0.39; 95% CI, 0.27-0.48). Whereas preemptive epidural analgesia resulted in consistent improvements in all three outcome variables, preemptive local anesthetic wound infiltration and NSAID administration improved analgesic consumption and time to first rescue analgesic request, but not postoperative pain scores. The least proof of efficacy was found in the case of systemic NMDA antagonist (ES, 0.09; 95% CI, -0.03 to 0.22) and opioid (ES, -0.10; 95% CI, -0.26 to 0.07) administration, and the results remain equivocal.

Preemptive analgesia in foot and ankle surgery

Central neuroplasticity, or changes in CNS processing due to surgical nociception. can amplify postoperative pain. As a result, a hyperalgesic state called wind-up can occur, having debilitating effects on postoperative patients. Preemptive analgesia works to prevent this process and results in a more positive surgical experience. Inhibition of afferent pain pathways by use of local anesthetic blocks, altered perception of pain with opioid use, and inhibition of pain pathways by NMDA receptor antagonists are examples of preemptive analgesia. Using a combination of preemptive modalities and addressing patients' perceptions can aid in interrupting pathologic pain cycles. Positive and modest results have been obtained from animal and human preemptive trials, yet basic pathophysiology demonstrates the validity and importance of preemptive analgesia. Future studies are needed to test effective blockade of afferent input while controlling perception, hyperalgesia, and NMDA receptor activity. The Agency for Health Care Policy and Research now recommends a multifaceted approach to postoperative pain. The goal in pain management is to inhibit destructive pain pathways, maintain intraoperative analgesia, and prevent central sensitization. Preliminary results of multimodal preemptive analgesia trials continue to be promising.

Attenuation of pain in a randomized trial by suppression of peripheral nociceptive activity in the immediate postoperative period

Peripheral neuronal barrage from tissue injury produces central nervous system changes that contribute to the maintenance of postoperative pain. The therapeutic approaches to blocking these central changes remain controversial, because previous studies have not differentiated presurgical interventions from those administered after tissue injury, yet before pain onset. In this study, we evaluated the relative contributions of blockade of nociceptive input during surgery or during the immediate postoperative period on pain suppression. Subjects were randomly allocated to one of four groups: preoperative 2% lidocaine, postoperative 0.5% bupivacaine, both, or placebo injections. General anesthesia was induced and third molars extracted. Pain was assessed over 4 h and at 24 and 48 h. The beta-endorphin in blood samples increased twofold during surgery, which is indicative of activation of the peripheral nociceptive barrage in response to painful stimuli. Pain was decreased in the immediate postoperative period in the bupivacaine groups, whereas it increased in the lidocaine group over time. Pain intensity was less 48 h after surgery in the groups whose postoperative pain was blocked by the administration of bupivacaine, but no effect was demonstrated for the preoperative administration of lidocaine alone. These results in the oral surgery pain model suggest that minimizing the peripheral nociceptive barrage during the immediate postoperative period decreases pain at later time periods. In contrast, blocking the intraoperative nociceptive barrage does not appear to contribute significantly to the subsequent reduction in pain.

IMPLICATIONS

Suppression of postoperative pain immediately after surgery attenuates the pain experienced 1 to 2 days after surgery. These findings suggest that pain after minor surgery can be prevented by blocking the development of pain processes that amplify pain for days after surgery.

[Nociceptors and mediators in acute inflammatory pain]

OBJECTIVE

To bring together the most recent data concerning the physiology of nociceptors at a time when there has been significant progress in the understanding of these.

DATA SOURCES

References were obtained from computerised bibliographic data banks (Medline and others) and the authors' personal documents.

DATA SYNTHESIS

Nociceptive impulses are generated at the periphery in unmyelinated fibres called nociceptors, the responses of which depend on the tissue environment. Numerous mediators can activate, sensitise or "wake up" nociceptor: kinins (bradykinin, kallidin and their metabolites), pro-inflammatory cytokines (TNF alpha, IL-6, IL-1 beta, IL-8), anti-inflammatory cytokines (IL-4, IL-6, IL-10, IL-12, IL-13), prostanoids (PGE2, PGI2), lipo-oxygenases (leucotrienes such LTB4 or 15-HETE), the "central mediators of the immune response" (NF-kappa B), growth factors such as neurotrophins (NGF, BDNF, NT-3 and NT-4/5), peptides (substance P, CGRP, Neurokinin A), nitric oxide, histamine, serotonin, proteases, excitatory amino acids, adrenergic amines and opioids. The release of neuromediators by primary afferent fibres in the spinal cord may be summarised by successively considering calcium channels, presynaptic receptors, excitatory amino acids and peptides.

CONCLUSION

Sensitisation phenomena are not exclusively peripheral but also central in origin and these are interlinked.

Activation of central terminal vanilloid receptor-1 receptors and alpha beta-methylene-ATP-sensitive P2X receptors reveals a converged synaptic activity onto the deep dorsal horn neurons of the spinal cord

Using a spinal cord slice preparation and patch-clamp recordings from spinal cord dorsal horn neurons, we examined excitatory and inhibitory circuits connecting to lamina V neurons after the activation of afferent central terminal vanilloid receptor-1 (VR1) receptors and P2X receptors. We found that single neurons in lamina V often received excitatory inputs from two chemically defined afferent pathways. One of these pathways was polysynaptic from capsaicin-sensitive afferent terminals. In this pathway the capsaicin-sensitive afferent input first activated interneurons in superficial laminas, and then the excitatory activity was transmitted onto lamina V neurons. The second excitatory input was monosynaptic from alpha(beta)m-ATP-sensitive/capsaicin-insensitive afferent terminals. Both capsaicin-sensitive and alpha(beta)m-ATP-sensitive/capsaicin-insensitive pathways also recruited polysynaptic inhibitory inputs to lamina V neurons. Furthermore, we demonstrated that simultaneous activation of both capsaicin-sensitive afferent pathways and alpha(beta)m-ATP-sensitive/capsaicin-insensitive pathways could generate a temporal summation of excitatory inputs onto single lamina V neurons. These convergent pathways may provide a mechanism of sensory integration for two chemically defined sensory inputs and may have implications in different sensory states.

Multimodal analgesia for postoperative pain control

Pain is one of the main postoperative adverse outcomes. Single analgesics, either opioid or nonsteroidal antiinflammatory drugs (NSAIDs), are not able to provide effective pain relief without side effects such as nausea, vomiting, sedation, or bleeding. A majority of double or single-blind studies investigating the use of NSAIDs and opioid analgesics with or without local anesthetic infiltration showed that patients experience lower pain scores, need fewer analgesics, and have a prolonged time to requiring analgesics after surgery. This review focuses on multimodal analgesia, which is currently recommended for effective postoperative pain control.

Effect of pre- or post-traumatically applied i.v. lidocaine on primary and secondary hyperalgesia after experimental heat trauma in humans

Hyperalgesia on intradermal capsaicin application can be attenuated by systemic application of local anesthetics. We tested whether low doses of local anesthetics applied pre- or post-traumatically can reduce heat trauma-induced primary and secondary hyperalgesia in humans. Six healthy volunteers consented to the randomized, double-blind, and cross-over designed study. In each subject, a first-degree burn injury was induced three times (corresponding to a pre-traumatic, post-traumatic and control group) at an interval of at least 3 weeks. Heat was applied by a computer-controlled Peltier thermode (47 degrees C, 5 min). In the pre-traumatic group, lidocaine infusion was commenced 30 min prior to heat trauma, and in the post-traumatic group immediately after heat trauma for a total infusion time of 60 min each. Volunteers rated pain on a visual analogue scale (VAS) between threshold and tolerance maximum (0-100% VAS). Primary hyperalgesia was quantified by determining mechanical (von Frey hairs) and thermal (Peltier thermode) pain thresholds. Secondary hyperalgesia was quantified by determining the area in which normally unpleasant von Frey hairs evoked pain or tenderness. Baseline thermal and mechanical pain thresholds did not differ between groups. Heat application always resulted in a first-degree burn injury including both primary and secondary hyperalgesia. The former remained by and large stable for about 4 h whereas the latter continuously increased within the first 2 h. Lidocaine did not affect primary hyperalgesia, irrespective of pre- or post-traumatic application, but substantially reduced the development of secondary hyperalgesia on pre-traumatic, and for tendency on post-traumatic infusion (treatment groups did not differ significantly). Burn injury-induced erythema was smallest in the pre-traumatic group and largest in the control group; however, the level of significance was not reached. Plasma concentrations of lidocaine were always higher than 1.5 microg/ml 30 min after bolus application of lidocaine and reached a peak of 2-3 microg/ml after about 1 h. Thus, local anesthetics at concentrations that do not block nerve conduction substantially affect ongoing central changes in pain processing that are induced by a real tissue trauma. A significant preemptive effect could not be demonstrated. The anti-hyperalgesic effect of lidocaine is likely based on action of central (spinal) sites, but peripheral sites may also be addressed.

Involvement of presurgical pain in preemptive analgesia for orthopedic surgery: a randomized double blind study

Preemptive analgesia (PA) is effective in animal models but its clinical effectiveness remains controversial. We examined the effect of preexisting pain on PA. Subjects were recruited from patients needing orthopedic surgery. Some had presurgical pain (fracture surgery and arthritic surgery), while others had no presurgical pain (removal surgery for a tumor, nail or plate). Epidural morphine or a saline control was given preemptively before surgery and maintained until skin closure. Following skin closure, naloxone or placebo was injected intravenously to erase the aftereffects of the morphine. After total recovery, the PCA pump was set to inject epidural morphine. Pain intensity after surgery was measured by a visual analogue scale (VAS), and the amount of morphine used within 48h after surgery. PA was significantly effective for removal surgery, but ineffective for fracture or arthritic surgery. For the fracture and arthritic surgery PA treatment groups, there was a significant correlation between pre- and postsurgical (6h) spontaneous pain, while the corresponding control groups showed no significant correlation. Postsurgical VAS values in the fracture and arthritic surgery control groups increased significantly compared with presurgical VAS values. PA was effective when presurgical pain was absent, but ineffective when presurgical pain was present. We propose that central sensitization is already established by presurgical pain, and preserved until the termination of surgery. The ineffectiveness of PA did not depend on whether the pain was acute (fracture surgery) or chronic (arthritic surgery).

The effect of a sciatic nerve block on the development of inflammation in carrageenan injected rats

Neurogenic inflammation may participate in postoperative inflammatory pain. We evaluated, in the rat, the influence of a short and prolonged sciatic nerve block on carrageenan-induced inflammation, the time course of which may be compared to postoperative inflammation. A catheter was placed on the right sciatic nerve and injected with 0.5% bupivacaine with epinephrine (0.2 mL): one injection in the Short Block Group, and four injections performed at 90-min intervals in the Prolonged Block Group. In all groups, the two hind paws were then injected with carrageenan. The development of inflammation was evaluated in both hind paws by measurement of paw circumference (PC) before, and 1, 2, 3, 4, 6, and 24 h after carrageenan injection. Temperature of both hind paws was evaluated at the same time points. The vocalization threshold to paw pressure test (VTPP) of both hind paws was evaluated at 6, 8, 10, 12, and 24 h after carrageenan injection. The left hind paw was used for the Control Group. A Sham Group had a catheter placed on the sciatic nerve and injected with normal saline. Inflammation developed in the Control Group with a maximum increase of PC (32%) and temperature (14%) 4 h after carrageenan injection and a maximal reduction of VTPP (44%) at 6 h, reflecting mechanical allodynia. A similar evolution was observed in the Sham Group. In the Short Block Group, the nerve block did not influence the PC, the paw temperature, or the VTPP when compared with the Control Group. In the Prolonged Block Group, when compared with the Control Group, the increased PC was reduced throughout the 24 h (P < 0.0001). The maximal increase in PC at 4 h was limited to 23%, as compared with the precarrageenan value. This effect on PC did not persist at 24 h. Paw temperature was increased (P = 0.07) throughout the study in the Prolonged Block Group, as compared with the Control Group. The VTPP reduction was still limited in the Prolonged Block Group at 24 h, as compared with the Control Group (P < 0.0001). We conclude that a prolonged sciatic nerve block limits carrageenan-induced increase in PC and, subsequently, mechanical allodynia at 24 h in rats.

IMPLICATIONS

Our study has shown that a prolonged (6 h) but not a short sciatic nerve block (90 min) can limit edema and related pain after carrageenan-induced inflammation in rat.

Modern concepts of paediatric analgesia

Laboratory data, economic pressures, and the wish for humane treatment have been some of the driving forces behind improvements in paediatric pain management. Within the space of 10 years, there have been dramatic changes in the quality of treatment received by children undergoing surgical operations. Moreover, those receiving medical treatment, for example, sickle cell disease, have also benefited from increased experience in pain management. Children receiving care in specialised centres can now expect to benefit from up-to-date techniques of pain management, such as patient-controlled analgesia, nurse-controlled analgesia, and epidural infusions. They will be managed by ward nurses experienced and trained in paediatric pain relief, they will be attended by nurses whose special interest and training is the management of children's pain, and they will be provided with the techniques of analgesia by competent, trained anaesthetic staff. Improved care, with close attention to pain relief, is not only humane, but improves the patient turnaround by enhancing rapid discharge. Further education is required to spread these benefits to children being managed outside highly specialised centres. Not only education, but investment, is needed also to ensure that all children receive a standard of care second to none.

Analgesic agents for the postoperative period. Nonopioids

For many reasons, nonopioid analgesics have proven to be of immense benefit in postoperative pain relief. Consideration of the limitations and side effects of opioids confirms the need for alternative, complementary analgesics. The current understanding of pain pathophysiology recognizes that many tissue and neuronal factors and changes are invoked by tissue damage, producing peripheral and central sensitization, and some of these may be modulated by the use of NSAIDs, NMDA antagonists, and local anesthetic agents. If successful preemptive analgesic techniques are developed, they will likely include the use of NSAIDs and perhaps NMDA antagonists. Nonopioids are of benefit in multimodal analgesia and allow acute rehabilitation of surgical patients. Acetaminophen, NSAIDs, alpha 2-antagonists, and NMDA antagonists are in routine use as components of multimodal analgesia, in combination with opioids or local anesthetic techniques. Tramadol is interesting because it has nonopioid and opioid actions that can be attributed to the two isomers found in the racemic mixture. Spinal neostigmine and the use of adenosine represent completely different mechanisms of nonopioid analgesia being investigated. Nonopioids, including lidocaine, ketamine, the anticonvulsants, and the antidepressants, are necessary for the treatment of patients with the difficult clinical problem of neuropathic pain that can present in the postoperative period.

Postoperative complications and unanticipated hospital admissions

Following anesthesia and surgery, children have more postoperative complications in the recovery room than adults. The majority of events are age-related (neonates and infants) and involve the respiratory rather than the cardiovascular system. In spite of newer antinausea drugs, pediatric patients have a high incidence of postoperative nausea and vomiting leading to unexpected admission to the hospital. Pain is underreported and undertreated in the pediatric population.

Effect of topical local anesthetic application to skin harvest sites for pain management in burn patients undergoing skin-grafting procedures

OBJECTIVE

To determine if topical administration of local anesthesia, applied to fresh skin-harvest sites, reduces pain and analgesic requirements after surgery.

SUMMARY BACKGROUND DATA

Nonopioid treatments for pain after therapeutic procedures on patients with burns have become popular because of the side effects associated with narcotics. The topical administration of local anesthesia originally offered little advantage because of poor epidermal penetration.

METHODS

This study compares 2% lidocaine with 0.5% bupivacaine or saline, topically applied after skin harvest, to determine what effect this may have on pain and narcotic use. Sixty patients with partial- or full-thickness burns to approximately 10% to 15% of their body were randomly divided into three groups: group 1 received normal saline, group 2 had 0.5% bupivacaine, and group 3 had 2% lidocaine sprayed onto areas immediately after skin harvest. Blood samples were subsequently obtained to measure concentrations of the local anesthetic. Hemodynamic variables after surgery, wake-up times, emetic symptoms, pain, and narcotic use were compared.

RESULTS

Higher heart rates were noted in the placebo group than in those receiving lidocaine or bupivacaine. No differences were noted in recovery from anesthesia or emetic symptoms. Pain scores were lower and 24-hour narcotic use was less in patients who received lidocaine. Plasma lidocaine levels were greater than bupivacaine at all time points measured.

CONCLUSIONS

Topical lidocaine applied to skin-harvest sites produced an analgesic effect that reduced narcotic requirements compared with patients who received bupivacaine or placebo. Local anesthetic solutions aerosolized onto skin-harvest sites did not affect healing or produce toxic blood concentrations.

[Prevention of postoperative pain]

The pre-emptive analgesia concept suggests that pre-administration of analgesics may enhance the efficacy of these drugs. This review has selected the data from the literature according to two types of methodological criteria: Sackett's criteria, and those specific of pre-emptive analgesia studies. Infiltration, spinal and peripheral nerve blocks using local anaesthetic drugs do not seem to produce pre-emptive analgesia. The few positive results have limited clinical significance. The results concerning opioids are contradictory and the clinical significance is limited. Preoperative oral administration of non steroidal anti-inflammatory drugs (NSAIDs) offers no benefit. Intravenous pre-administration has a limited advantage, but enhances perioperative bleeding. Ketamine, an NMDA receptor antagonist, may have some pre-emptive analgesic properties according to the few studies available. In conclusion, pre-administration of analgesic drugs represents the usual strategy for the anaesthesiologist (spinal or peripheral block, infiltration, opioids). In other cases (NSAIDs, ketamine), pre-administration represents a change in usual practice. This is not justified for NSAIDs; NMDA receptor antagonists may offer an interesting research area. Data concerning pre-emptive analgesia for chronic pain syndrome such as phantom limb pain are quite limited.

Analgesic effect of bupivacaine on extraperitoneal laparoscopic hernia repair

Local anesthetics decrease postoperative pain when placed at the surgical site. Patients benefit from laparoscopic extraperitoneal hernia repair because this allows earlier mobilization than the more classical open surgical approach. The purpose of this study was to determine the pain-sparing efficacy of local anesthetics placed in the preperitoneal fascial plane during extraperitoneal laparoscopic inguinal hernia surgery. Forty-two outpatients were included in a double-blind, randomized, placebo-controlled, institutional review board-approved study. At the conclusion of a standardized general anesthetic, 21 patients received 60 mL of 0.125% bupivacaine into the preperitoneal fascial plane before incisional closure, whereas the other 21 patients received 60 mL of the isotonic sodium chloride solution placebo. Postoperative pain was assessed 1, 4, 8, 24, and 72 h postoperatively. In addition, postoperative fentanyl and outpatient acetaminophen 500 mg/hydrocodone 5 mg requirements were recorded. All hernia repairs were performed by the same surgeon. Appropriate statistical analyses were used. There were no significant differences between the bupivacaine and isotonic sodium chloride solution groups with regard to postoperative pain scores, length of postanesthesia care unit stay, or analgesic requirements. Furthermore, neither unilateral versus bilateral repair nor operative time affected the measured parameters. The addition of 60 mL of 0.125% bupivacaine into the preperitoneal fascial plane during extraperitoneal laparoscopic hernia repair did not significantly alter pain scores, supplementary analgesic requirements, or recovery room length of stay.

IMPLICATIONS

The placement of 60 mL of 0.125% bupivacaine into the preperitoneal fascial plane during extraperitoneal laparoscopic hernia repair did not significantly alter pain scores, supplementary analgesic requirements, or recovery room length of stay.

Peripheral nerve blocks improve analgesia after total knee replacement surgery

Total knee replacement (TKR) produces severe postoperative pain. Peripheral nerve blocks can be used as analgesic adjuncts for TKR, but the efficacy of femoral nerve blocks alone is controversial. The sciatic nerve innervates posterior regions of the knee; thus, performance of both sciatic and femoral nerve blocks may be necessary to improve analgesia after TKR. We performed this study to determine whether peripheral nerve blocks improve analgesia after TKR. In a randomized, double-blind fashion, 36 patients undergoing TKR received either femoral, sciatic-femoral, or sham nerve blocks after a standardized spinal anesthetic. Further postoperative analgesia was provided by patient-controlled i.v. morphine and ketorolac. Pain at rest and with physical therapy, morphine use, nausea, pruritus, sedation, and patient satisfaction were assessed. Patients receiving peripheral nerve blocks reported better analgesia at rest for at least 8 h after transfer to the hospital ward (P < 0.05). Morphine use was decreased by approximately 50% in the peripheral nerve block groups until the second postoperative day (P < 0.02). Side effect profiles and patient satisfaction were similar between groups. We conclude that femoral nerve blocks improve analgesia and decrease morphine use after TKR. The addition of a sciatic nerve block to the femoral nerve block did not further improve analgesic efficacy.

IMPLICATIONS

Performance of femoral nerve blocks improves analgesia and decreases the need for morphine after total knee replacement surgery. The addition of a sciatic nerve block to the femoral nerve block does not provide additional benefits.

Hyperalgesia and temporal summation of pain after heat injury in man

Temporal summation of pain occurs when repeated stimuli become increasingly painful in spite of unchanged stimulus intensity. Summation can be quantified as the difference in pain between the first and the last stimulus in a train of stimuli. The aim of the study was to compare temporal summation of pain in normal skin with summation of pain in skin with primary and secondary hyperalgesia evoked by a heat injury. A heat injury was produced on the crus of 12 volunteers with a 50 x 25 mm thermode (47 degrees C, 7 min). Measurements were made before, and 0, 1, 2, and 4 h after the heat injury, in three areas: primary and secondary mechanical hyperalgesia induced by the heat injury, and in a mirror image of the injury on the opposite leg. Temporal summation of pain was induced by repeated electrical stimuli (five stimuli at 2 Hz) and assessed by visual analog scale (VAS). Primary hyperalgesia was evaluated by von Frey hairs and electrical stimuli, and the areas of secondary hyperalgesia with a rigid von Frey hair (314 mN). Significant primary (P < 0.000001) and secondary (P < 0.00006) mechanical hyperalgesia were evoked by the heat injury. The pain threshold to single electrical stimuli was reduced within the injury (P < 0.03), but not outside. The pain responses to single and repeated electrical stimuli were not significantly altered by the injury. Temporal summation of pain occurred in 418 stimulus trains out of 576 (73%), but no significant changes in summation developed in skin with primary or secondary mechanical hyperalgesia compared with normal skin (baseline measurements). Temporal summation at high stimulus intensities was more pronounced than at lower intensities (P < 0.0002). We found no correlation between either temporal summation and area of secondary hyperalgesia, or temporal summation and pain intensity during the induction of heat injury. We conclude that the development of primary and secondary mechanical hyperalgesia after heat injury in man was not associated with changes in temporal summation of painful electrical stimuli.